CN100486062C - Tunable resonator, tunable light source, and method for tuning wavelength of multiple resonator - Google Patents

Abstract

Tunable light source with a tunable resonator which comprises: a multiple resonator constituted by at least three resonant elements that oscillates with a wavelength where frequencies of three or more resonant elements with shifted free spectral ranges intersect; and a tunable device for controlling the resonant wavelength of the multiple resonator by simultaneously changing the respective optical path lengths of a plurality of the resonant elements. The multiple resonator has a structure in which three resonant elements are connected in series; and provided that the optical path lengths of the resonant elements are L 0 , L 1 , L 2 , Vernier orders are M 1 >1, M 2 > 1, the optical path lengths are defined as L 1 = M 1 M 1 - 1 L 0 , L 2 = M 2 M 2 - 1 L 0 , phase amount 'Phase' is the changed optical path length standardized by one-wavelength of the optical path length, and the respective phase amount 'Phase' of the two ring resonant elements whose optical path lengths are to be changed are defined as 'Phase M1 ' and 'Phase M2 ', the tunable device controls the increase/decrease amount of the phase amount 'Phase M1 ' and 'Phase M2 ' based on a linear function with a slope of M 2 - 1 M 1 - 1 .

Description

The wavelength tuning method of tunable resonator, tunable optical source, multiple resonator

Technical field

The present invention relates to can be used for tunable optical source of WDN (Wavelength Division Multiplexing, wavelength division multiplexing) transmission system etc. for example etc.

Background technology

Along with the arrival of broadband era, in order effectively to utilize optical fiber, available individual system carries out the WDN transmission system of the communication of a plurality of optical wavelength extensively to be introduced.Recently, can multiplexing dozens of optical wavelength carrying out more, the DWDM device of high-speed transfer (dense wavelength division multiplexingdevice, dense wave division multipurpose device) have obtained extensive utilization.Thereupon, in each WDM transmission system, need the light source corresponding, and along with height is multiplexing, the quantity of required light source increases greatly with each optical wavelength.Especially nearest, for commercial applications the ROADM (reconfigurable optical add/dropmultiplexers, Reconfigurable Optical Add/drop Multiplexer) at each node branch/slotting (Add/Drop) any wavelength is studied.If this ROADM system of introducing then except enlarging the transmission capacity based on wavelength multiplexing, can also carry out the light path switching by changing wavelength, so the degree of freedom of optical-fiber network significantly improves.

The light source of using as the WDM transmission system, so far, the DFB-LD (Distributed feedback laser diode, distributed feedback semiconductor laser) of single longitudinal mode vibration is because easy to use and reliability is high and be widely used always.In DFB-LD, be formed with diffraction grating about dark 30nm in whole resonator area, thereby can with the corresponding wavelength of product of the twice of diffraction grating cycle and equivalent refractive index on obtain stable single longitudinal mode vibration.But in DFB-LD, owing to can not stride across the tuning of oscillation wavelength on a large scale, so for each ITU (internationaltelecommunication union; International Telecommunications Union) grid only uses that the different goods of wavelength constitute the WDM transmission system.Therefore, owing to need use different goods,, maybe need to be used to tackle the excess reserve of fault so cause the increase of management cost at each wavelength.In addition, if use common DFB-LD in according to the ROADM of wavelength switching-over light path, then the tunable amplitude based on the wave-length coverage of variations in temperature is limited in about 3nm.Therefore, be difficult to constitute the optical-fiber network that the speciality of the ROADM of positive use wavelength resource is effectively utilized.

In order to overcome the above-mentioned present problem that DFB-LD had, and can in wide wave-length coverage, realize the single longitudinal mode vibration, the tunable laser as tunable optical source is furtherd investigate.Below, by enumerating several examples the content that describes in detail from following non-patent literature 1 existing tunable laser is described.

Tunable laser is broadly divided into two types, that is, the type of tunable mechanism is set in laser diode and the type of tunable mechanism is set outside laser diode.

In last type, propose to have DBR-LD (Distributed Bragg reflector Laserdiode, distributed feedback semiconductor laser).This DBR-LD will produce the active region of gain and be formed on structure in the same laser diode by the DBR zone that diffraction grating produces reflection.The highest 10nm only of the tunable range of this DBR-LD.In addition, also propose to have the DBR-LD that uses inhomogeneous diffraction grating.This DBR-LD be with produce the active region of gain and in the past the DBR zone of clamping this active region, rear be formed on structure in the same laser diode.In the DBR zone at front and back and rear, produce a large amount of reflection peaks by inhomogeneous diffraction grating, and a little is only staggered with the rear forwardly in the interval of reflection peak.Owing to can obtain so-called " fine setting effect (vernier effect) " by this structure, so can realize extremely wide tunable range.In using the DBR-LD of inhomogeneous diffraction grating, this can realize surpassing the tuning action of 100nm and the quasi-continuous tuning action of 40nm.

Thereby the tunable laser of back one type is to make the diffraction grating rotation that is located at the laser diode outside make the light of specific wavelength turn back to the structure of laser diode.

Non-patent literature 1: the bright work of holt merit, " light collection Plot デ バ イ ス (optical integrated device) ", the front page second impression, upright altogether the publication Co., Ltd., in December, 2000, p.104-122;

Non-patent literature 2: " Optical Filter Design and Analysis (optical fiber designs and analysis) " C.K.Madsen, J.H.Zhao.

Yet,, be easy to be called the wavelength switching accident that can't expect of " mode jump " though in tunable laser in the past, proposed multiple structure up to now.In addition, wavelength control method complexity, vibration resistance are weak owing to existing, element increases the shortcomings of bringing such as price rising, never change so be difficult to the situation of practical application.

In DBR-LD, by injecting charge carrier, the refractive index in the described DBR zone is changed, thereby wave-length coverage is changed to the DBR zone.Therefore, cause crystal defect to increase because electric current injects, then refractive index significantly change with respect to the variation ratio that electric current injects, so be difficult in long-term the use, keep the laser generation of fixed wave length.In addition, with the process technology of existing compound semiconductor, can not carry out three inches (inch) above processing.In order to realize this process, then need huge development cost.Therefore, in having the laser diode of large-scale size configurations, its manufacturing cost significantly rises.

In addition, in tunable mechanism being located at outside laser diode,, therefore need large-scale anti-shock mechanism for fear of this situation owing to vibration is easy to take place mode jump.Therefore cause the increase of module size and the rising of price.

Summary of the invention

Therefore, the objective of the invention is to, provide a kind of and can overcome the technical problem of debatable existing tunable laser in actual applications, realize the tunable optical source of high reliability, high-performance, low price etc.

In order to reach above-mentioned purpose, tunable resonator of the present invention is characterised in that and comprises: multiple resonator, and it carries out resonance with the wavelength that the frequency of the different resonant element more than three of cycle intersects; And tuned unit, it changes the described a plurality of resonant elements optical length separately that constitutes described multiple resonator simultaneously, thereby controls the resonance wavelength of described multiple resonator.

In described tunable resonator of the present invention, in order to control the resonance wavelength of carrying out the multiple resonator of resonance with the crossing wavelength of the frequency of the different resonant element more than three of cycle, change the described a plurality of resonant elements optical length separately that constitutes described multiple resonator simultaneously by tuned unit, thereby control the resonance wavelength of described multiple resonator.

When described multiple resonator be three resonant elements be connected in series structure the time, the optical length of establishing described resonant element is L ₀, L ₁, L ₂, establishing optical length the shortest in three is L ₀, at M ₁0, M ₂Under 0 the condition, will finely tune exponent number M ₁, M ₂Be defined as

${\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">M</figure-callout>}}_1=\frac{L_1}{L_1-{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0},$ ? ${\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">M</figure-callout>}}_2=\frac{L_2}{L_2-{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0},$

Make ${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{M_1}{M_1-1}\&times;{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0,$ ? ${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=\frac{M_2}{M_2-1}\&times;{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0$ Condition set up.

In addition, when the change amount of optical length be the light wavelength in the resonant element length ( λ is a wavelength, and n is a refractive index) time, the phase mass Phase that has changed optical length is defined as one-period.Illustrate with concrete numerical value, for example, when optical path-length shifts

The time, described phase mass Phase is 2.

Under above definition, when described multiple resonator be three resonant elements be connected in series structure the time, separately the phase mass Phase relative with two resonant elements that changed optical length is made as Phase _M1, Phase _M2So,,

Described tuned unit based on slope is

Linear function control described phase mass Phase _M1, Phase _M2The increase and decrease amount.

Described linear function preferably is made as

${\mathrm{<figure-callout\; id="1"\; label="Phase\; M"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M=\frac{M_1-1}{M_2-1}\&times;{\mathrm{<figure-callout\; id="2"\; label="Phase\; M"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M+N+\mathrm{\&phi;}.$

In the formula, the cycle that the frequency of the resonant element more than three that N indication cycle is different intersects, N=0, ± 1, ± 2, ± 3 ...In addition, φ represents initial phase.General 0≤φ＜1, this be because the φ that satisfies φ＜0 or 1≤φ in fact and satisfy the φ equivalence of 0≤φ＜1.

Described linear function also can be set as

${\mathrm{<figure-callout\; id="1"\; label="Phase\; M"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{<figure-callout\; id="2"\; label="Phase\; M"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M,1\}+N+\mathrm{\&phi;}.$

Described function m od[m, n] be expression m is removed resulting remainder by n function.Here " remainder " is meant the numerical value that decimal point is later.

In order to derive described function m od[m, n], establish

m＝(M ₂—1)/(M ₁—1)×Phase _M2

n＝1，

Then, Phase _M1=mod[m, n]+N+ φ,

${\mathrm{<figure-callout\; id="1"\; label="Phase\; M"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{<figure-callout\; id="2"\; label="Phase\; M"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M,1\}+N+\mathrm{\&phi;}.$

If the described phase mass of resonant element that will be corresponding with the resonance wavelength of described multiple resonator is made as Phase _M1(λ), Phase _M2(λ), then described linear function is

${\mathrm{Phase}}_{M1}\left(\mathrm{\&lambda;}\right)=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{Phase}}_{M2}\left(\mathrm{\&lambda;}\right),1\}+{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">N</figure-callout>}}_1+\mathrm{\&phi;}.$

The derivation process of this formula is described.

If $m=\frac{M_2-1}{M_1-1}\{\frac{1}{S_{\mathrm{CHANNEL}}(M_2-1)}(\mathrm{\&lambda;}-W_{\mathrm{CENTER}})+{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">N</figure-callout>}}_2+\mathrm{\&phi;}\}$

N=1, then

Phase _M1(λ) as follows:

Phase _M1(λ)＝mod[m，n]+N ₁+φ ₁。

Since function m od[m, n] be to represent m by the function of n except that resulting remainder, so

${\mathrm{Phase}}_{M1}\left(\mathrm{\&lambda;}\right)=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{Phase}}_{M2}\left(\mathrm{\&lambda;}\right),1\}+{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">N</figure-callout>}}_1+\mathrm{\&phi;}$

${\mathrm{Phase}}_{M2}\left(\mathrm{\&lambda;}\right)=\frac{1}{S_{\mathrm{CHANNEL}}(M_2-1)}(\mathrm{\&lambda;}-W_{\mathrm{CENTER}})+{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">N</figure-callout>}}_2+{\mathrm{\&phi;}}_2.$

Therefore, Phase _M1(λ) and Phase _M2Relational expression (λ) as mentioned above.

N ₁, N ₂The cycle identical with described N, that the frequency of two resonant elements that indication cycle is different intersects.φ ₁, φ ₂The expression initial phase, W _CENTERThe center of the tunable range of expression resonance wavelength, S _CHANNELThe tunable minimum interval of expression resonance wavelength.Each initial phase, i.e. φ, φ ₁, φ ₂, can be the value when luminous intensity is maximum in the resonance wavelength.At this moment, can obtain the light of stable resonance wavelength.The value of this initial phase can be obtained theoretically by calculating, and also can experimentize by actual measurement and find the solution.In fact, when making this element, can be owing to the influence that is subjected to foozle makes that the initial phase of design load and actual measurement is inconsistent.Therefore, after manufacturing, carry out the mensuration of initial phase value usually.Each cycle, i.e. N, N ₁, N ₂Can be made as " 0 ".At this moment, owing to be used to obtain as the required phase mass minimum of the characteristic of target, thus be used to obtain the energy minimum of the required power of resonance frequency, heat etc., thus can efficient realize the light of resonance wavelength well.

Allow described phase mass Phase _M1(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M1(λ) come in the scope of variable quantity of phase mass required when the resonance wavelength of adjacency is switched, and

Allow described phase mass Phase _M2(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M2(λ) come in the scope of variable quantity of phase mass required when the resonance wavelength of adjacency is switched.

Allow described phase mass Phase _M1(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M1(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 50% in, and

Allow described phase mass Phase _M2(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M2(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 50% in.

Allow described phase mass Phase _M1(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M1(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 30% in, and

Allow described phase mass Phase _M2(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M2(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 30% in.

That is, because phase mass Phase _M1(λ), phase mass Phase _M2Resonance condition is more stable in the time of (λ) in described scope, therefore allows it in described scope.For obtaining stable status more, preferably described " variable quantity of required phase mass when the resonance wavelength of adjacency is switched " 50% in, be preferably in 30%.

Preferred described tuned unit constitutes the structure that changes the resonance wavelength of resonant element based on the temperature characterisitic of resonant element.At this moment, preferred described tuned unit is regulated the light path refractive index of described resonant element and in the optical path length at least one will usually change described optical length.

Described resonant element also can be constructed by the annular resonance element with disc waveguide.Comprise two kinds of structures in having the optical resonance element of described disc waveguide, a kind of is the structure that only has disc waveguide, and another kind is except disc waveguide, also comprises the structure of input, output waveguide separately.

Described multiple resonator can have light reflection function unit.Described smooth reflection function unit is the Waveguide structure that makes the light reflection or be transmitted to described multiple resonator.Perhaps, described smooth reflection function unit comprises: reflection is from the reflection of light function element of described multiple resonator; And make light two-way waveguide of passing through between described multiple resonator and described reflection function element.In addition, described multiple resonator and described tuned unit can be formed on the same substrate.

Said structure is object with the tunable resonator, but the present invention is not limited to this.Also can be with described tunable resonator of the present invention as tunable optical source.Tunable optical source of the present invention is built into and comprises: multiple resonator, and it carries out resonance with the wavelength that the frequency of the different resonant element more than three of cycle intersects; Tuned unit, it changes the optical length separately of the described a plurality of resonant elements that constitute described multiple resonator simultaneously, thereby controls the resonance wavelength of described multiple resonator; Optical Amplifier Unit, it is connected an end of described multiple resonator; With light reflection function unit, it is present in an opposite side of described Optical Amplifier Unit and the link of described multiple resonator.

In addition, the optical length of resonant element is generally represented by the refractive index * length of light path.Therefore, when constituting multiple resonator, preferably, change the optical length of described resonant element by using described tuned unit to regulate the refractive index of the light path of described resonant element (high refracting crystal) by resonant element with a plurality of disc waveguides.In addition, as multiple resonator, when for example using basic filter, Mach-Zehnder (Mach-Zehnder) interferometer, by regulating the length of light path, for example mirror each other the length of formed light path change the optical length of described resonant element.In addition, the resonant element that constitutes multiple resonator is not limited to above-described, and the wavelength that any frequency that can constitute the resonant element more than three that staggers with the cycle intersects carries out the element of tuning multiple resonator can.

Each resonant element that constitutes multiple resonator is slightly different because of the difference FSR (free spectralrange, Free Spectral Range) of optical length.Therefore, in the wavelength (resonance wavelength) of the cyclic variation unanimity of the optical transmission that in each resonant element, produces, produce maximum optical transmission.Thus, in the present invention, the slightly different resonant element of a plurality of optical lengths of having contacted constitutes multiple resonator, thereby has utilized consequent fine setting effect dexterously.

In the present invention, for the interval with common minimum in multiple resonator changes resonance wavelength, importantly carry out the change (phase mass) of the optical length relative simultaneously with a plurality of resonant elements that should change optical length.That is, when only a resonant element being changed phase mass, can not change resonance wavelength with the interval of common minimum.Specifically, change each phase mass, make it to satisfy above-mentioned formula.Thus, owing to can prevent multiple resonator with undesirable oscillation wavelength, so can carry out stable tunable action.

As described above, according to the present invention, the wavelength crossing in the frequency of the resonant element three or more different with the cycle carries out in the multiple resonator of resonance, control the resonance wavelength of described multiple resonator owing to change the described a plurality of resonant elements optical length separately that constitutes described multiple resonator simultaneously, so can change resonance wavelength with the minimum interval.Consequently, because the wavelength switching of inhibition outside plan, so can realize stable tunable action, thus the tunable optical source of high reliability, high-performance and low price can be provided.

Description of drawings

Fig. 1 is the block diagram of basic structure that the tunable resonator of embodiments of the present invention is shown;

Fig. 2 is the plane graph that the tunable optical source of the embodiments of the present invention of having utilized tunable resonator shown in Figure 1 is shown;

Fig. 3 is illustrated in the tunable optical source shown in Figure 2, the figure of the wavelength response characteristic of many ring resonators of seeing from the SOA side;

Fig. 4 is the performance plot that the relation of phase mass relative with employed toroidal cavity resonator in the tunable optical source shown in Figure 2 and resonance wavelength is shown;

Fig. 5 is the performance plot of the resonance wavelength when the phase mass change relative with employed toroidal cavity resonator in the tunable optical source shown in Figure 2 is shown;

Fig. 6 is the performance plot that relation permissible value, phase mass and resonance wavelength of the phase mass that is used for illustrating tunable optical source shown in Figure 2 is shown;

Fig. 7 is the performance plot that relation permissible value, phase mass and mould gain inequality of the phase mass that is used for illustrating tunable optical source shown in Figure 2 is shown;

Fig. 8 is the part enlarged drawing of Fig. 7;

Fig. 9 is the schematic diagram that the tunable optical source of other execution modes of the present invention is shown.

Embodiment

Embodiments of the present invention are described below with reference to the accompanying drawings.

Making up basic filter, the such light feedback arrangement of PLC type annular resonance element, promptly have in the tunable optical source of the such image intensifer of the external resonator of a plurality of loop configuration and SOA, also do not have to establish the structure of not using the dynamic wavelength stabilizing mechanism and carrying out stable wavelength control.

Embodiments of the present invention relate to multiple resonator and comprise the light generating apparatus of this multiple resonator, and described multiple resonator has made up a plurality of resonant elements that can carry out the parameter of stable wavelength control that have.In embodiments of the present invention, in the multiple resonator of the resonant element of series connection more than three, the optical length of establishing the shortest resonant element of optical length is L ₀, and to optical length L ₀Each optical length L of resonant element in addition definition fine setting exponent number (vernier order) M makes L=M1/ (M1-1) L ₀Relation set up.Then, change controlled quentity controlled variable described later simultaneously, thereby can under the situation that does not possess the dynamic wavelength stabilization function, stably switch the tuning wavelength of tunable optical source a plurality of resonant elements according to function described later.

As shown in Figure 1, the basic structure of the tunable resonator of embodiment of the present invention is characterised in that, comprising: multiple resonator 5, and its crossing wavelength of frequency at the resonant element more than three 2,3,4 that the cycle staggers carries out resonance; Tuned unit 6, it changes the optical length separately of a plurality of resonant elements 2,3,4 that constitute described multiple resonator 5 simultaneously, thus the resonance wavelength of control multiple resonator 5.

Multiple resonator 5 arrives reflection function element 8 to the light signal (hereinafter referred to as light) of light input/output port 7 incidents through light input/output port 7 → resonant element 2 → resonant element 3 → resonant element 4, and after 8 reflections of reflection function element, turn back to light input/output port 7 through resonant element 4 → resonant element 3 → resonant element 2, and penetrate from the light input/output port 7 of multiple resonator 5.At this moment, since the light that penetrates from the light input/output port 7 of multiple resonator 5 with optical length L separately by resonant element 2,3,4 ₀～L ₂The resonance wavelength of determining, that is, the wavelength that the frequency of the resonant element 2,3,4 that staggers with the cycle intersects carries out resonance, so multiple resonator 5 is the strongest to the light intensity of light input/output port 7 outputs.

Thereby tuned unit 6 can change the resonance wavelength of multiple resonator 5 by controlling the optical length (phase mass) of resonant element 3,4 simultaneously in the interval of minimum.

In addition, the optical length of resonant element is generally represented by the refractive index * length of light path.Therefore, when constituting multiple resonator 5 by resonant element 2,3,4 with a plurality of disc waveguides, by using described tuned unit 6 to regulate the refractive index of the light path (high refracting crystal) of described resonant element 2,3,4, change the optical length of described resonant element 2,3,4.In addition, as multiple resonator 5, when for example using basic filter, Mach-Zehnder (Mach-Zehnder) interferometer, by regulating the length of light path, for example mirror each other the length of formed light path change the optical length of described resonant element 2,3,4.In addition, the resonant element that constitutes multiple resonator is not limited to above-described, and any wavelength that can intersect as the frequency of the resonant element more than three that staggers with the cycle carries out tuning multiple resonator and the element that constitutes can.In addition, the resonant element that constitutes multiple resonator 5 is not limited to illustrated number, so long as more than three, to the not restriction of its number.

(first execution mode)

Below, based on the following example of Fig. 2 explanation as first execution mode, promptly, the resonant element (below be called the annular resonance element) 21,22,23 that will have disc waveguide is as the resonant elements 2,3,4 that constitute multiple resonator 5, and three annular resonance elements, 21,22,32 polyphones are connected constructs multiple resonator 20.Multiple resonator 20 is corresponding to the multiple resonator 5 of Fig. 1.

The tunable resonator of embodiment of the present invention has: multiple resonator 20, carry out resonance on the wavelength that the frequency of three resonant elements 21,22,23 that it staggered in the cycle intersects; Tuned unit (6), it changes the optical length separately of three resonant elements 21,22,23 that constitute described multiple resonator 20 simultaneously, thereby controls the resonance wavelength of described multiple resonator 20.In execution mode shown in Figure 2, TO (Thermo Optic, hot light) phase shifter 17 and controller 18 are used as tuned unit shown in Figure 16.

In three resonant elements 21,22,23, be used to transmit optical waveguide and on PLC substrate 13, form ring-type by high refractive index crystals.In addition, input and output side waveguide 11, reflection-side waveguide 12, waveguide 24,25 form rectilinear form on PLC substrate 13.The disc waveguide of resonant element 21,22,23, waveguide 24,25 are formed on the same substrate, but also can be respectively formed on the different substrates.In addition, described waveguide also can be formed on the substrate by quartz glass serial crystal, lithium niobate etc.

Resonant element 21 is coupled by optical coupling unit with the locational input and output side waveguide 11, the waveguide 24 that are positioned at this resonant element 21 of clamping.In addition, resonant element 22 is coupled by optical coupling unit with the locational waveguide 24, the waveguide 25 that are positioned at this resonant element 22 of clamping.In addition, resonant element 23 is coupled by optical coupling unit with the locational reflection-side waveguide 12, the waveguide 25 that are positioned at this resonant element 23 of clamping.In addition, because optical coupling unit is general, describe in detail so omit it, any two-way lossless structure that passes through of light that makes between described resonant element and described waveguide can.

Light signal (hereinafter referred to as light) to 11 incidents of input and output side waveguide arrives highly reflecting films (reflection function element) 14 through input and output side waveguide 11 → resonant element 21 → resonant element 22 → resonant element 23 → reflection-side waveguide 12, and reflection on highly reflecting films 14, turn back to input and output side waveguide 11 through reflection-side waveguide 12 → resonant element 23 → resonant element 22 → resonant element 21, and from input and output side waveguide 11 directive Optical Amplifier Unit SOA 15.At this moment, since emergent light with resonant element 21,22,23 optical length L separately ₀～L ₂Determined resonance wavelength, that is, the wavelength that the frequency of the resonant element 21,22,23 that the cycle staggers intersects carries out resonance, so light intensity is the strongest.

As shown in Figure 2, the position of the disc waveguide of the TO phase shifter 16,17 of formation tuned unit and annular resonance element 22,23 is formed on the PLC substrate 13 accordingly.TO phase shifter 16,17 shown in Figure 2 has by the disc waveguide of giving annular resonance element 22,23 and heats the refractive index that changes described disc waveguide, thereby changes the optical length L of annular resonance element 22,23 ₁, L ₂Function.In execution mode shown in Figure 2, for example can use membranaceous heater to be used as TO phase shifter 16,17, this membranaceous heater is made of the pellumina of evaporation coating on the PLC substrate 13 of annular resonance element 22,23 positions.This membranaceous heater 16,17 is by controller 18 power supply heating described later.

In the disc waveguide of the annular resonance element 22,23 that has used glass and compound semiconductor, the refractive index of its crystal increases in 1/1000～1/100 scope with temperature.Thereby, when the disc waveguide of annular resonance element 21,22,23 receives the heat of membranaceous heater 16,17 and when being heated, because refractive index increases, so the optical length L of described annular resonance element 21,22,23 reality ₁, L ₂Change.By in as the membranaceous heater 16,17 of TO phase shifter, using controller 18 that the power of 0.5W is provided, can change the optical length of the annular resonance element 21,22,23 of a wavelength that is equivalent to multiple resonator 20.

Execution mode shown in Figure 2 shows the structure under the perfect condition that does not comprise foozle in the optical length of the disc waveguide of annular resonance element 21,22,23.But in reality, when making the disc waveguide of annular resonance element 21,22,23, in its optical length, produce error sometimes.Therefore, also can be used for determining that annular resonance element 21 settings of wavelength are equivalent to the TO phase shifter of TO phase shifter 16,17, thereby when tunable resonator starts, finely tune the optical length L of annular resonant element 21 ₀In addition, in order to suppress each wavelength channel (wavelength channel) employed wavelength shift from opto-electrical transmitting device, also can in oscillation action, finely tune the optical length L of annular resonant element 21 ₀

In addition, though hot type TO phase shifter 16,17 is used as the optical length L that changes or finely tune annular resonant element 21,22,23 ₀, L ₁, L ₂Tuned unit, but be not limited to this.The crystal of the disc waveguide of looping resonant element 21,22,23 has invertibity.At this moment, also can use the heat absorbing type Peltier element (Peltier Element) that will be located on the substrate as TO phase shifter 16,17, and by the heat-absorbing body of controller to this Peltier element power supply.When using this heat-absorbing body, owing to cool off from the disc waveguide absorption heat of annular resonance element 21,22,23, so the refractive index of described disc waveguide reduces in 1/1000～1/100 scope.Change the optical length L of annular resonance element 21,22,23 thus ₀, L ₁, L ₂In addition, as tuned unit, though what use is membranaceous heater of hot type or heat absorbing type Peltier element, any can change the element of the optical index of disc waveguide by other means can.

Many ring resonators 20 are constituted as to have connected has mutually different optical length L ₀, L ₁, L ₂The optical-waveguide-type filter of described annular resonance element 21～23.Many ring resonators 20 only all annular resonance elements 21～23 simultaneously during resonance the light signal to resonance wavelength carry out multiplexing (multiplexes) and demultiplexing (demultiplexes), obtain big FSR by finely tuning effect.So-called fine setting effect is meant the different resonant element of a plurality of optical lengths of combination increasing the method for tunable range, each resonance frequency of stack on the frequency of the least common multiple of the frequency of a plurality of resonant elements that it staggered in the cycle.Therefore, the apparent function that goes up FSR is the frequency that becomes the least common multiple of each ring.Therefore, can under big frequency, carry out the control of characteristic than single resonant element more easily.

In said embodiment, multiple resonator 20 is built into and has made up a plurality of annular resonance elements, and carries out the structure of the input and output of light by same waveguide 11, but is not limited thereto.Multiple resonator 20 also can be built into following structure: annular resonance element 21,22,23 comprises input and output waveguide separately in disc waveguide, from a waveguide input optical signal of multiple resonator 20, and multiple resonator 20, improved the light signal of luminous intensity from other waveguide output of multiple resonator 20.

In addition, the light reflection function unit that is had as multiple resonator 20, used the highly reflecting films 14 that the light from multiple resonator 20 is reflected and made the combination of light two-way waveguide of passing through 11,12 between multiple resonator 20 and highly reflecting films 14, but be not limited thereto.Described smooth reflection function unit also can constitute and make light reflection or transmission (transmits) arrive the waveguiding structure of multiple resonator 20.As shown in Figure 2, the light reflection function unit of the described waveguiding structure that is used to reflect is built into following structure: under the situation of not using highly reflecting films 14, only make transmission direction counter-rotating, thereby turn back to multiple resonator 20 once more from the light of multiple resonator 20 by reflection-side waveguide 12.In addition, the light reflection function unit of described transmission can be applicable to be undertaken in the multiple resonator of input and output of light signal by waveguide separately, and is built into and makes optical signal transmission arrive structure in the multiple resonator.

More than about the structure of tunable resonator.The tunable optical source 10 of embodiment of the present invention shown in Figure 2 also comprises except the structure of above-mentioned tunable resonator: the Optical Amplifier Unit 15 that links to each other with an end of described multiple resonator 20; The reflector element 14 that is present in described Optical Amplifier Unit 15 and an opposite side of the link of described multiple resonator 20.In execution mode shown in Figure 2, the reflectance coating 14 that will have high reflectance is as described reflector element 14.Tunable optical source 10 is equivalent to described light-emitting device.In addition, as reflector element 14, as long as can substitute highly reflecting films 14 by reverberation.

Described highly reflecting films 14 are coupled with the terminal of the reflection-side waveguide 12 of tunable resonator, and have following function: will reflex to reflection-side waveguide 12 by the light that reflection-side waveguide 12 transmits from many ring resonators 20.Light reflection function unit is by the highly reflecting films 14 that reflect the light that receives from multiple resonator 20 as reflecting element and make the light two-way waveguide of passing through (reflection-side waveguide 12) formation between multiple resonator 20 and reflecting element (14), but is not limited thereto.Light reflection function unit also can be made of the waveguide with two functions of input and output, that is: make the light that receives from multiple resonator 20 turn back to multiple resonator 20 by inside.

As Optical Amplifier Unit 15, use semiconductor optical amplifier (SOA, SemiconductorOptical Amplifier).In addition,, can use image intensifers such as fiber amplifier, also can use semiconductor laser light sources such as (laser diodes) as Optical Amplifier Unit 15.

Controller 18 is used to control membranaceous heater 16,17 and the light input-output unit 15 as the TO phase shifter.Specifically, controller 18 is by constituting according to the microcomputer of program behavior with by the combination of this microcomputer control direct current power source supplying power.Described microcomputer has following function: the control signal of importing the value of the resonance wavelength of representing multiple resonator 20 from the outside, and ask performance number according to the predetermined mathematical expression of described control signal and storage in advance, provide the power that is equivalent to this performance number from DC power supply to TO phase shifter 16,17 then.In addition, also can insert the asymmetric mach-Ceng Deer interferometer that is used for restricted band (band) in input and output side waveguide 11 or in the reflection-side waveguide 12.

Specify the situation of the resonance wavelength of control multiple resonator in embodiment of the present invention below.

In embodiment of the present invention, when the wavelength that intersects when the frequency of control different resonant element more than three with the cycle carries out the resonance wavelength of multiple resonator of resonance, change the optical length separately of the described a plurality of resonant elements that constitute described multiple resonator simultaneously by tuned unit, thereby control the resonance wavelength of described multiple resonator.

When three resonant elements of series connection constituted described multiple resonator, the optical length of establishing described resonant element was L ₀, L ₁, L ₂, establishing optical length the shortest in three is L ₀, at M ₁0, M ₂Under 0 the condition, will finely tune exponent number M ₁, M ₂Be defined as:

${\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">M</figure-callout>}}_1=\frac{L_1}{L_1-{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0},$ ? ${\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">M</figure-callout>}}_2=\frac{L_2}{L_2-{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0},$

Make ${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{M_1}{M_1-1}\&times;{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0,$ ? ${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=\frac{M_2}{M_2-1}\&times;{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0$ Condition set up.

In addition, when the change amount of optical length be the light wavelength in the resonant element length (

λ is a wavelength, and n is a refractive index) time, the phase mass Phase that has changed optical length is defined as one-period.Use concrete numerical value to illustrate, for example, when the variable quantity of optical length is

The time, described phase mass Phase is 2.

Under above definition, when three resonant elements of series connection constitute described multiple resonator, separately the phase mass Phase relative with two resonant elements that changed optical length is made as Phase _M1, Phase _M2So,,

Described tuned unit 16,17,18 based on slope is

Linear function control described phase mass Phase _M1, Phase _M2The increase and decrease amount.

Tunable optical source 10 can freely be selected required wavelength by many ring resonators 20 and SOA 15 under the control of tuned unit 16,17,18.Optical length L as the annular resonance element 21 of radix ₀For example be set as about 4mm, making FSR is 50GHz.At this moment, the optical length L of annular resonance element 22,23 ₁, L ₂Utilize fine setting exponent number M ₁, M ₂Draw by following formula.

${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{M_1}{M_1-1}\&times;L_0---\left(1\right)$

${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=\frac{M_2}{M_2-1}\&times;L_0---\left(2\right)$

The third order PLL shape resonant element 21～23 of Gou Chenging is the same with the second order toroidal cavity resonator like this, and also the wavelength that is complementary with the cycle shift of annular resonance element 21～23 separately carries out laser generation with least disadvantage.Determine that by the annular resonance element 21 that girth is the shortest channel spacing is 50GHz, and freely select oscillation wavelength by remaining two annular resonance elements 22,23.

Pass through three annular resonance elements 21～23 from the ASE light of SOA 15 outputs, and reflection on highly reflecting films 14, turn back to SOA 15 by three annular resonance elements 21～23 once more afterwards.For example connect between SOA 15 and the PLC substrate 13 by directly be coupled (butt-coupling).In SOA 15, implement the AR coating for the end face of PLC substrate one side, optical fiber one side end face has 10% reflectivity.Except direct coupling, SOA 15 and PLC substrate 13 can also directly be installed or Lens Coupling on PLC substrate 13 by passive formation (Passive Alignment) mode.

The light that penetrates from SOA15 arrives SOA 15 → non reflecting film → input and output side waveguide 11 → multiple resonator 20 → reflection-side waveguide 12 → highly reflecting films 14, after reflection on these highly reflecting films 14, return through path reflection-side waveguide 14 → multiple resonator 20 → input and output side waveguide 11 → non reflecting film → SOA 15, and on the exiting side end face of SOA 15, reflect.By this reflection of light effect, multiple resonator 20 plays a role as laser resonator.This back light is the light of the resonance wavelength of multiple resonator 20.Its reason is as follows: the FSR of each annular resonance element 21,22,23 of formation multiple resonator 20 is slightly different, therefore, bigger reflection takes place in the wavelength (resonance wavelength) of the cyclic variation unanimity of the reflection (transmission) that is taken place in each annular resonance element 21,22,23.So,, move so can obtain the good wavelength tuning of efficient because the wavelength of cycle unanimity significantly changes by the variation of the waveguide index of each annular resonance element 21,22,23.This waveguide index for example can change by hot optical effect.So-called hot optical effect is meant the phenomenon that increases the refractive index of material by heat, and usually, which type of material all has this characteristic.That is, can utilize the temperature characterisitic of a plurality of annular resonance elements 21,22,23 to change the resonance wavelength of multiple resonator 20.In addition, also can change wavelength by the refractive index control method outside the hot optical effect, the control of circumferential length.

Here narrate concrete numerical example.If the center transmission wavelength of multiple resonator (optical-waveguide-type filter) 20 is 1540nm, but the harmony scope of multiple resonator 20 is 50nm, then the girth as the annular resonance element 21 of radix (is L ₀) be about 4mm.At this moment, if wavelength channel be spaced apart 0.4nm, then M ₂-1 is 50nm/0.4nm=125, so M ₂=126.And, this moment M ₁From mould gain inequality maximization condition $M_1-1=\sqrt{M_2-1}$ Draw M ₁=12.2.Therefore, draw L from formula (1) ₁Be about 4.36mm, draw L from formula (2) ₂Be about 4.03mm.

At this moment, has becate shape waveguide L ₀ Annular resonance element 21 be used for fixing ITU grid (ITU grid), have the longest disc waveguide L ₂ Annular resonance element 22 be used for fine setting, have the disc waveguide L of intermediate length ₁ Annular resonance element 23 be used for coarse adjustment.

Fig. 3 is the performance plot that the wavelength response characteristic of many ring resonators 20 of seeing from SOA 15 1 sides is shown.Describe based on Fig. 2 and Fig. 3 below.

In the example depicted in fig. 3, except formula (1), (2) of front, also can set the fine setting exponent number and make M ₂-1=(M ₁-1) ²Set up.That is, the fine setting exponent number of each annular resonance element 21～23 is M ₁=11, M ₂=101.Directional coupler (optical coupling unit) moves as three-dB coupler by setting k=π/4.By M ₂100 wavelength channels of-1 definition exist at interval with 50GHz, and with by M ₁Per ten passages of-1 definition divide into groups.That is, can carry out the number of wavelengths of tuning action by M ₂Determine M ₂100 passage actions of-1.As passage that inserts the loss minimum and the mould gain inequality that inserts the loss difference of the little passage of loss second is 3.8dB.

Here, the group that comprises the passage that inserts the loss minimum is called central. set, the group adjacent with this central. set is called contiguous set, by satisfying aforesaid three formulas, can say so: in Fig. 3, insert loss second little passage and the interior insertion loss of inserting the passage of loss minimum of contiguous set in the central. set and equate substantially.

Fig. 4 is the curve chart that the relation of phase mass relative with annular resonance element 22,23 and resonance wavelength is shown.The action (one) of tunable optical source 10 is described according to Fig. 2 and Fig. 4 below.Described phase mass is defined as, the optical length by a wavelength amount to the variation of toroidal cavity resonator optical length carry out the phase mass that standardization gets.

Fig. 4 represents to be the phase mass relative with annular resonance element 23 when transverse axis, the analog result of the expression resonance wavelength the when longitudinal axis is the phase mass relative with annular resonance element 22.Each phase mass is proportional substantially with the electric energy that imposes on TO phase shifter 16,17.The fine setting exponent number M of annular resonance element 22 ₁Be " 12 " the fine setting exponent number M of annular resonance element 23 ₂Be " 126 ".

In Fig. 4, the phase mass of the longitudinal axis and transverse axis is periodically expression, and becomes 1 at 2 π places.When the power of 400mW for example is provided to TO phase shifter 16,17, can only change the phase place of the resonance wavelength of 2 π (amount of a wavelength).Have the many ring resonators 20 in three rank of this TO phase shifter 16,17 by use, can select required light source oscillation wavelength with matrix-style.In addition, to TO phase shifter 16,17 energising, thus the wavelength characteristic when only changing the phase mass of 0.5 (1/2 wavelength amount) the and only wavelength characteristic during change-0.5 (1/2 wavelength amount) is identical.Therefore, annular resonance element 22,23 all has the characteristic of the same wavelength of turning back in one-period.Be characterised in that the matrix configuration of wavelength is not a complete orthogonal system, but is tilted to the right in the drawings in many ring resonators 20.Therefore, the electric energy that offers TO phase shifter 16,17 has interdependence, rather than independence.

That is, as seen from Figure 4,, need to change simultaneously the both sides' relative phase mass with annular resonance element 22,23 in order to change resonance wavelength with the minimum interval usually.That is, be based on slope

Linear function change the both sides' relative phase mass simultaneously with annular resonance element 22,23.

Specifically, change each phase mass, make it satisfy some in following formula (3), formula (4), formula (5), the formula (6).Thus, owing to can prevent to disturb oscillation wavelength, so can realize stable tunable action.

Utilize the temperature characterisitic of TO phase shifter 16,17 to change annular resonance element 22,23 optical length separately simultaneously, thus the tuning wavelength of control multiple resonator.The optical length of annular resonance element 21,22,23 is made as L ₀, L ₁, L ₂, will finely tune exponent number and be made as M ₁1, M ₂1, described optical length is made as ${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{M_1}{M_1-1}\&times;{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0,$ ? ${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=\frac{M_2}{M_2-1}\&times;{\mathrm{<figure-callout\; id="0"\; label="L"\; filenames="C200610058345E00321.png"\; state="\{\{state\}\}">L</figure-callout>}}_0,$ Phase mass Phase is that the optical length by a wavelength amount carries out standardization to the optical length that has changed and gets, and separately the phase mass relative with two the annular resonance elements 22,23 that changed optical length is made as Phase _M1, Phase _M1, at this moment, described tuned unit (16,17,18) according to slope is

Linear function control described phase mass Phase _M1, Phase _M2The increase and decrease amount.

When the phase mass relative with annular resonance element 22,23 is set as Phase respectively _M1, Phase _M2The time, set described linear function suc as formula (3).

${\mathrm{<figure-callout\; id="1"\; label="Phase\; M"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M=\frac{M_1-1}{M_2-1}\&times;{\mathrm{<figure-callout\; id="2"\; label="Phase\; M"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M+N+\mathrm{\&phi;}---\left(3\right).$

In the formula, the cycle that the frequency of the resonant element more than three that N indication cycle is different intersects, N=0, ± 1, ± 2, ± 3 ...In addition, φ represents initial phase.General 0≤φ＜1, this be because the φ that satisfies φ＜0 or 1≤φ in fact and satisfy the φ equivalence of 0≤φ＜1.

Like this, for two phase mass Phase _M1, Phase _M2, linear relation is set up.Because the oscillation wavelength of tunable optical source 10 is determined by the least common multiple as the FSR in cycle of three annular resonance elements 21～23, so have such periodicity and interdependence.

In addition, described linear function also can be set at following formula:

${\mathrm{<figure-callout\; id="1"\; label="Phase\; M"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{<figure-callout\; id="2"\; label="Phase\; M"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">Phase</figure-callout>}}_M,1\}+N+\mathrm{\&phi;}---\left(4\right)$

Described function m od[m, n] be expression m is removed resulting remainder by n function.Here " remainder " is meant the numerical value that decimal point is later.

In order to derive described function m od[m, n], establish

m＝(M ₂—1)/(M ₁—1)×Phase _M2

n＝1，

Then, Phase _M1=mod[m, n]+N+ φ,

In addition, N and φ are equivalent to above-mentioned numerical value.

In addition, if the phase mass of resonant element that will be corresponding with the resonance wavelength of described multiple resonator is made as Phase _M1(λ), Phase _M2(λ), then described linear function also can be made as:

${\mathrm{Phase}}_{M1}\left(\mathrm{\&lambda;}\right)=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{Phase}}_{M2}\left(\mathrm{\&lambda;}\right),1\}+{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">N</figure-callout>}}_1+\mathrm{\&phi;}---\left(5\right)$

The derivation of this formula is described.

If $m=\frac{M_2-1}{M_1-1}\{\frac{1}{S_{\mathrm{CHANNEL}}(M_2-1)}(\mathrm{\&lambda;}-W_{\mathrm{CENTER}})+{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">N</figure-callout>}}_2+\mathrm{\&phi;}\}$

N=1, then

Phase _M1(λ) as follows:

Phase _M1(λ)＝mod[m，n]+N ₁+φ ₁。

Since function m od[m, n] be to represent m by the function of n except that resulting remainder, so

${\mathrm{Phase}}_{M1}\left(\mathrm{\&lambda;}\right)=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{Phase}}_{M2}\left(\mathrm{\&lambda;}\right),1\}+{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="C200610058345E00281.png,C200610058345E00321.png"\; state="\{\{state\}\}">N</figure-callout>}}_1+\mathrm{\&phi;}$

${\mathrm{Phase}}_{M2}\left(\mathrm{\&lambda;}\right)=\frac{1}{S_{\mathrm{CHANNEL}}(M_2-1)}(\mathrm{\&lambda;}-W_{\mathrm{CENTER}})+{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="C200610058345E00281.png"\; state="\{\{state\}\}">N</figure-callout>}}_2+{\mathrm{\&phi;}}_2---\left(6\right).$

Therefore, Phase _M1(λ) and Phase _M2Relational expression (λ) as mentioned above.

N ₁, N ₂The cycle identical with described N, that the frequency of two resonant elements that indication cycle is different intersects.φ ₁, φ ₂The expression initial phase, W _CENTERThe center of the tunable range of expression resonance wavelength, S _CHANNELThe tunable minimum interval of expression resonance wavelength.Each initial phase, i.e. φ, φ ₁, φ ₂, can be the value when luminous intensity is maximum in the resonance wavelength.At this moment, can obtain the light of stable resonance wavelength.The value of this initial phase can be obtained theoretically by calculating, and also can experimentize by actual measurement and find the solution.Each cycle, i.e. N, N ₁, N ₂Can be made as " 0 ".At this moment, owing to be used to obtain the required energy minimum of each phasor, so can efficient realize the light of resonance wavelength well.

Can allow described phase mass Phase _M1(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M1(λ) come in the scope of variable quantity of phase mass required when the resonance wavelength of adjacency is switched.

And, can allow described phase mass Phase _M2(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M2(λ) come in the scope of variable quantity of phase mass required when the resonance wavelength of adjacency is switched.

Can allow described phase mass Phase _M1(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M1(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 50% in.

And, can allow described phase mass Phase _M2(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M2(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 50% in.

Can allow described phase mass Phase _M1(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M1(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 30% in.

And, can allow described phase mass Phase _M2(λ) value when maximum is the center with light intensity in this resonance wavelength, is only changing this phase mass Phase _M2(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 30% in.

That is, because phase mass Phase _M1(λ), phase mass Phase _M2Resonance condition is more stable in the time of (λ) in described scope, therefore allows it in described scope.For obtaining stable status more, preferably described " variable quantity of required phase mass when the resonance wavelength of adjacency is switched " 50% in, be preferably in 30%.

Fig. 5 is the performance plot that the resonance wavelength when changing the phase mass relative with annular resonance element 22,23 and being scheduled to formula to satisfy is shown.The action of tunable optical source 10 is described according to Fig. 2 and Fig. 5 below.

Fig. 5 shows an example that changes the resonance wavelength of the phase mass relative with annular resonance element 22,23 when satisfying some in described formula (3), formula (4), formula (5), the formula (6).In this example, the fine setting exponent number M of annular resonance element 22 ₁Be " 12 " the fine setting exponent number M of annular resonance element 23 ₂Be " 126 ".In Fig. 5, the electric energy that provides to phase shifter 16,17 of with dashed lines and single-point line expression, just phase mass respectively; Represent the oscillation wavelength of tunable optical source 10 of this moment, just resonance wavelength with solid line.Like this, control the optical length (phase place) of annular resonant element 22,23, can realize the switching of wavelength discretely according to aforesaid mathematical expression.

In addition, in formula (3), formula (4), formula (5), formula (6), with each initial phase, i.e. φ, φ ₁, φ ₂Be made as the value of light intensity maximum in the resonance wavelength of multiple resonator 20.Each cycle, i.e. N, N ₁, N ₂Be " 0 ".

Fig. 6 is used to illustrate the phase mass Phase relative with annular resonance element 22,23 _M1, Phase _M2License Value, phase mass Phase _M1, Phase _M2Graph of a relation with resonance wavelength.Fig. 7 is the performance plot that the relation of phase mass relative with annular resonance element 22,23 and mould gain inequality is shown.Fig. 8 is the part enlarged drawing of Fig. 7.Illustrate according to Fig. 2, Fig. 4, Fig. 6 and Fig. 8 below.

Fig. 6 has schematically illustrated a part of taking out from Fig. 4, and is the phase mass Phase relative with annular resonance element 23 at transverse axis _M2, the longitudinal axis is the phase mass Phase relative with annular resonance element 22 _M1The time, the resonance wavelength of multiple resonator 20 is shown.Below to the phase mass Phase of the resonance wavelength that is used to keep multiple resonator 20 _M1, Phase _M2Tolerance band describe.

Phase mass Phase _M1Value O when can be with light intensity in this resonance wavelength maximum is the center, is only changing phase mass Phase _M1Come the variable quantity ± Δ P of phase mass required when the resonance wavelength of adjacency is switched _M1Scope in.Equally, phase mass Phase _M2Value O when can be with light intensity in this resonance wavelength maximum is the center, is only changing phase mass Phase _M2Come the variable quantity ± Δ P of phase mass required when the resonance wavelength of adjacency is switched _M2Scope in.That is, for Fig. 6 being exactly can be in the solid box of parallelogram.

Here, the light intensity maximum also is a mould gain inequality maximum in the resonance wavelength.Therefore, as phase mass Phase _M1, Phase _M2When leaving central point O, improved the possibility of switching with the resonance wavelength of purpose adjacency owing to noise etc.Therefore, in order to obtain more stable resonance condition, preferably at the described " variable quantity ± Δ P of required phase mass when the resonance wavelength of adjacency is switched _M1, ± Δ P _M1" separately 50% in, be preferably in it in 30%.That is, for Fig. 6, can be in the frame of broken lines of parallelogram or in the frame of double dot dash line.The following describes the basis that is defined as " 50% " and " 30% ".

For example, the wavelength interdependence is often arranged in the gain characteristic of SOA 15.In desirable SOA, there is not the wavelength interdependence, but owing to the problem of material and manufacture method produces the wavelength interdependence.Can exemplify out the easiest problem that becomes the SOA end face reflection of problem.

In desirable SOA, unidirectional from the light of outside input by SOA inside, direct then directive outside.Therefore, by bloomed coating being set, can make the reflectivity on end face become " 0 " ideally at the SOA end face.But, because in fact reflectivity can have fully, so produce mode of resonance in the inside of SOA.By this mode of resonance, the periodically pulsing (ripple) definite by resonator length (optical length) L of SOA is comprised in the Amplifier Gain composition.

Because the gain characteristic of substantial three rank resonator type lasers (multiple resonator) is by the product decision of the gain characteristic of the gain characteristic of the resonant element of three grades of polyphones and amplifier (SOA), so be subjected to the influence of the gain characteristic of SOA, the wavelength channel of the laser vibration of multiple resonator begins to change from the wavelength of expection.Therefore, need under the condition that can keep big as far as possible mould gain inequality, make laser works.Because the pulsating quantity of such SOA is about 2dB, so the mould gain inequality of the multiple resonator that third order PLL shape resonant element constitutes also need be more than 2dB.

According to simulation, the central part of the concussion wavelength characteristic of multiple resonator 20 that can be in Fig. 6 is realized maximum mould gain inequality.Drawn among Fig. 7 and had M ₂=126, M ₁=12 characteristic, and be comprised in mould gain inequality in the phase place (optical length) of each disc waveguide of the annular resonance element 22,23 in the multiple resonator 20.

Under the most stable condition of the resonance wavelength of multiple resonator 20, mould gain inequality maximum, this point becomes the center condition of Fig. 6.Fig. 7 part illustrates the condition of a mould gain inequality in the wavelength channel.By this figure as can be seen, the condition that obtains the above mould gain inequality of 1dB is, the phase difference that switches to the wavelength of adjacency from the part of maximum norm gain inequality ± 50% amplitude; The condition that obtains the above mould gain inequality of 2dB is the amplitude of phase difference ± 30%.Must be in accessing move under the condition of the mould gain inequality of the pulse characteristic of employed SOA above laser.The wavelength pulse characteristic of general SOA is about 2dB, if characteristic is good, then is about 1dB.

(execution mode 2)

Fig. 9 is the schematic diagram that other tunable optical source of embodiment of the present invention is shown.Describe according to this accompanying drawing below.

In the execution mode shown in Fig. 2 A, will have the resonant element of the annular resonance element 21,22,23 of disc waveguide as multiple resonator 20.In execution mode shown in Figure 9, replace described annular resonance element with basic filter (etalon filters) 31～33, and constitute multiple resonator 30 by these basic filters 31～33 of contacting.

It is the length that differs from one another that the optical length of the basic filter 31,32,33 of formation multiple resonator 30 is set to.In execution mode shown in Figure 9, the length of the light path by changing basic filter 31,32,33 changes the optical length of basic filter 31,32,33.

For example the light from the output of SOA (not shown) arrives basic filter 31 → basic filter 32 → basic filter 33 → highly reflecting films 34, and by these highly reflecting films 34 reflections, the path via basic filter 33 → basic filter 32 → basic filter 31 turns back to SOA then.The light that turns back to SOA is with the optical length L by basic filter 31,32,33 ₀, L ₂, L ₃The resonance wavelength of come determining, be that the wavelength that the frequency of different basic filter of cycle (resonant element) 31,32,33 intersects carries out resonance, therefore, the light intensity that outputs to SOA from multiple resonator 30 is the strongest.

In execution mode shown in Figure 9, identical with execution mode shown in Figure 2, also change the optical length of basic filter 31,32,33, thereby obtain effect and the effect identical with first execution mode according to formula (3), formula (4), formula (5), formula (6).

In addition, for example available high refractive index crystals, Mach-Zehnder interferometer wait and replace basic filter.The tuned unit of high refractive index crystals for example be make the birefringence crystal the polarization of incident light wave tilt through mechanism.The tuned unit of Mach-Zehnder interferometer for example is the TO phase shifter identical with first execution mode.

In addition, constituting the resonant element of multiple resonator, except the annular resonance element, can also be that for example basic filter, Mach-Zehnder interferometer, high refractive index crystals etc. become the element of resonant element.The resonant element that constitutes multiple resonator is slightly different because of the difference FSR (free spectralrange, Free Spectral Range) of optical length.Therefore, in the wavelength (resonance wavelength) of the cyclic variation unanimity of the optical transmission that in each resonant element, produces, produce maximum optical transmission.Thus, in embodiments of the present invention, the slightly different resonant element of a plurality of optical lengths of having contacted constitutes multiple resonator, has utilized the fine setting effect thus dexterously.

The invention is not restricted to above-mentioned first and second execution modes.For example multiple resonator also can be made of the resonator more than four.

Industrial applicibility

As described above, according to the present invention, at the resonance element three or more different with the cycle The wavelength that frequency intersects carries out in the multiple resonator of resonance, because it is described multiple humorous to change simultaneously formation The optical length separately of described a plurality of resonance elements of device of shaking is controlled the resonance ripple of described multiple resonator Long, so can change the resonance wavelength with minimum interval.

Claims (18)

1. tunable resonator is characterized in that having:

Multiple resonator, it carries out resonance with the wavelength that the frequency of the different resonant element more than three of cycle intersects; With

Tuned unit, in the described resonant element more than three, the optical length of establishing the shortest resonant element of optical length is L ₀, for optical length L ₀Each optical length L of resonant element in addition is according to making $L=\frac{M}{M-1}\&times;L_0$ The fine setting exponent number M that sets up of relation, change described three the above resonant elements optical length separately that constitutes described multiple resonator simultaneously, thereby control the resonance wavelength of described multiple resonator.

2. tunable resonator as claimed in claim 1 is characterized in that,

Described multiple resonator is three structures that resonant element is connected in series,

The optical length of described resonant element is made as L ₀, L ₁, L ₂, will finely tune exponent number and be made as M ₁1, M ₂1, described optical length is made as $L_1=\frac{M_1}{M_1-1}\&times;L_0,$ $L_2=\frac{M_2}{M_2-1}\&times;L_0,$ Phase mass Phase is that the optical length by a wavelength amount carries out standardization to the optical length that has changed and gets, and is L with optical length ₁The phase mass of resonant element be made as Phase _M1, optical length is L ₂The phase mass of resonant element be made as Phase _M2, at this moment,

Described tuned unit according to slope is

Phase _M2Be independent variable, Phase _M1For the linear function of dependent variable is controlled described phase mass Phase _M1, Phase _M2The increase and decrease amount.

3. tunable resonator as claimed in claim 2 is characterized in that,

Described linear function is

${\mathrm{Phase}}_{M1}=\frac{M_1-1}{M_2-1}\&times;{\mathrm{Phase}}_{M2}+N+\mathrm{\&phi;}$

The frequency of the different resonant element more than three of N indication cycle cycle of intersecting wherein, N=0, ± 1, ± 2, ± 3, φ represents initial phase.

4. tunable resonator as claimed in claim 2 is characterized in that,

Described linear function is

${\mathrm{Phase}}_{M1}=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{Phase}}_{M2},1\}+N+\mathrm{\&phi;}$

The frequency of the different resonant element more than three of N indication cycle cycle of intersecting wherein, N=0, ± 1, ± 2, ± 3, φ represents initial phase; Mod[m, n] be that expression m is removed resulting remainder by n, described remainder is meant the numerical value that decimal point is later.

5. tunable resonator as claimed in claim 2 is characterized in that,

If the described phase mass of resonant element that will be corresponding with the resonance wavelength of described multiple resonator is made as Phase _M1(λ), Phase _M2(λ), then described linear function is

${\mathrm{Phase}}_{M1}\left(\mathrm{\&lambda;}\right)=\mathrm{mod}\{\frac{M_2-1}{M_1-1}{\mathrm{Phase}}_{M2}\left(\mathrm{\&lambda;}\right),1\}+N_1+\mathrm{\&phi;}$

N wherein ₁The cycle that the frequency of the resonant element more than three that indication cycle is different intersects, N ₁=0, ± 1, ± 2, ± 3, φ represents initial phase; Mod[m, n] be that expression m is removed resulting remainder by n, described remainder is meant the numerical value that decimal point is later.

6. as each described tunable resonator in the claim 3 to 5, it is characterized in that,

Described φ satisfies following condition: 0≤φ＜1.

7. tunable resonator as claimed in claim 5 is characterized in that,

Described phase mass Phase _M1(λ) value that is set to light intensity in this resonance wavelength when maximum is the center, is only changing this phase mass Phase _M1(λ) come in the scope of variable quantity of phase mass required when the resonance wavelength of adjacency is switched, and

Described phase mass Phase _M2(λ) value that is set to light intensity in this resonance wavelength when maximum is the center, is only changing this phase mass Phase _M2(λ) come in the scope of variable quantity of phase mass required when the resonance wavelength of adjacency is switched.

8. tunable resonator as claimed in claim 5 is characterized in that,

Described phase mass Phase _M1(λ) value that is set to light intensity in this resonance wavelength when maximum is the center, is only changing this phase mass Phase _M1(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 50% in, and

Described phase mass Phase _M2(λ) value that is set to light intensity in this resonance wavelength when maximum is the center, is only changing this phase mass Phase _M2(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 50% in.

9. tunable resonator as claimed in claim 5 is characterized in that,

Described phase mass Phase _M1(λ) value that is set to light intensity in this resonance wavelength when maximum is the center, is only changing this phase mass Phase _M1(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 30% in, and

Described phase mass Phase _M2(λ) value that is set to light intensity in this resonance wavelength when maximum is the center, is only changing this phase mass Phase _M2(λ) come phase mass required when the resonance wavelength of adjacency is switched variable quantity 30% in.

10. tunable resonator as claimed in claim 1 is characterized in that,

Described tuned unit changes the resonance wavelength of resonant element based on the temperature characterisitic of resonant element.

11. tunable resonator as claimed in claim 1 is characterized in that,

Described tuned unit is regulated the light path refractive index of described resonant element and in the optical path length at least one will usually change described optical length.

12. tunable resonator as claimed in claim 1 is characterized in that,

Described resonant element is the annular resonance element with disc waveguide.

13. tunable resonator as claimed in claim 1 is characterized in that,

Described multiple resonator has light reflection function unit.

14. tunable resonator as claimed in claim 13 is characterized in that,

Described smooth reflection function unit has the waveguide that makes the light reflection or be transmitted to described multiple resonator.

15. tunable resonator as claimed in claim 13 is characterized in that,

Described smooth reflection function unit comprises: reflection is from the reflection of light function element of described multiple resonator; And make light two-way waveguide of passing through between described multiple resonator and described reflection function element.

16. tunable resonator as claimed in claim 1 is characterized in that,

Described multiple resonator and described tuned unit are formed on the same substrate.

17. a tunable optical source is characterized in that having:

Multiple resonator, it carries out resonance with the wavelength that the frequency of the different resonant element more than three of cycle intersects;

Tuned unit, in the described resonant element more than three, the optical length of establishing the shortest resonant element of optical length is L ₀, for optical length L ₀Each optical length L of resonant element in addition is according to making $L=\frac{M}{M-1}\&times;L_0$ The fine setting exponent number M that sets up of relation, change the optical length separately of described three the above resonant elements that constitute described multiple resonator simultaneously, thereby control the resonance wavelength of described multiple resonator;

Optical Amplifier Unit, it is connected an end of described multiple resonator; With

Light reflection function unit, it is connected the other end of described multiple resonator.

18. a tuning method is used to control the resonance wavelength of multiple resonator, wherein said multiple resonator carries out resonance with the wavelength that the frequency of the different resonant element more than three of cycle intersects, and described tuning method is characterised in that,

In the described resonant element more than three, the optical length of establishing the shortest resonant element of optical length is L ₀, for optical length L ₀Each optical length L of resonant element in addition is according to making $L=\frac{M}{M-1}\&times;L_0$ The fine setting exponent number M that sets up of relation, change described three the above resonant elements optical length separately that constitutes described multiple resonator simultaneously, thereby control the resonance wavelength of described multiple resonator.

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