CA1262304A - Laser-fiber positioner - Google Patents
Laser-fiber positionerInfo
- Publication number
- CA1262304A CA1262304A CA000486031A CA486031A CA1262304A CA 1262304 A CA1262304 A CA 1262304A CA 000486031 A CA000486031 A CA 000486031A CA 486031 A CA486031 A CA 486031A CA 1262304 A CA1262304 A CA 1262304A
- Authority
- CA
- Canada
- Prior art keywords
- fiber
- positioner
- epoxy
- light
- laser
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000000835 fiber Substances 0.000 title claims abstract description 107
- 239000004593 Epoxy Substances 0.000 claims abstract description 36
- 239000000463 material Substances 0.000 claims abstract description 26
- 239000011324 bead Substances 0.000 claims abstract description 16
- 238000004873 anchoring Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 17
- 239000000758 substrate Substances 0.000 claims description 7
- 230000008018 melting Effects 0.000 claims description 6
- 238000002844 melting Methods 0.000 claims description 6
- 238000012544 monitoring process Methods 0.000 claims description 4
- 230000008878 coupling Effects 0.000 abstract description 9
- 238000010168 coupling process Methods 0.000 abstract description 9
- 238000005859 coupling reaction Methods 0.000 abstract description 9
- 239000013078 crystal Substances 0.000 description 10
- 230000003534 oscillatory effect Effects 0.000 description 8
- 239000000523 sample Substances 0.000 description 5
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 4
- 238000005452 bending Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052709 silver Inorganic materials 0.000 description 4
- 239000004332 silver Substances 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 229910000679 solder Inorganic materials 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 101100352755 Drosophila melanogaster pnt gene Proteins 0.000 description 1
- 108091092889 HOTTIP Proteins 0.000 description 1
- OMFRMAHOUUJSGP-IRHGGOMRSA-N bifenthrin Chemical compound C1=CC=C(C=2C=CC=CC=2)C(C)=C1COC(=O)[C@@H]1[C@H](\C=C(/Cl)C(F)(F)F)C1(C)C OMFRMAHOUUJSGP-IRHGGOMRSA-N 0.000 description 1
- 230000002844 continuous effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
- G02B6/422—Active alignment, i.e. moving the elements in response to the detected degree of coupling or position of the elements
- G02B6/4227—Active alignment methods, e.g. procedures and algorithms
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
- G02B6/422—Active alignment, i.e. moving the elements in response to the detected degree of coupling or position of the elements
- G02B6/4226—Positioning means for moving the elements into alignment, e.g. alignment screws, deformation of the mount
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4219—Mechanical fixtures for holding or positioning the elements relative to each other in the couplings; Alignment methods for the elements, e.g. measuring or observing methods especially used therefor
- G02B6/4236—Fixing or mounting methods of the aligned elements
- G02B6/4239—Adhesive bonding; Encapsulation with polymer material
Abstract
LASER-FIBER POSITIONER
Abstract of the Disclosure To position a light output device such as a laser diode relative to a light input device such as a waveguide so as to obtain maximum coupling of light, light is launched into one end of the fiber and is detected at a remote part of the fiber where a corresponding electrical signal is generated. Positional information contained in the signal is used to reduce misalignment between the waveguide and laser by manipulating a positioner attached to the fiber. Since there is usually some slight movement of the fiber as an anchoring epoxy bead cures, it is necessary to move the fiber within the curing epoxy and it is advantageous if the position at which the positioner contacts the fiber is at the same site as the epoxy bead. By the invention, the positioner is attached to the fiber using a wax or similar material so that as the epoxy cures, it does not cure in contact with the positioner. When the epoxy is fully cured, the wax is melted and the positioner withdrawn.
- i -
Abstract of the Disclosure To position a light output device such as a laser diode relative to a light input device such as a waveguide so as to obtain maximum coupling of light, light is launched into one end of the fiber and is detected at a remote part of the fiber where a corresponding electrical signal is generated. Positional information contained in the signal is used to reduce misalignment between the waveguide and laser by manipulating a positioner attached to the fiber. Since there is usually some slight movement of the fiber as an anchoring epoxy bead cures, it is necessary to move the fiber within the curing epoxy and it is advantageous if the position at which the positioner contacts the fiber is at the same site as the epoxy bead. By the invention, the positioner is attached to the fiber using a wax or similar material so that as the epoxy cures, it does not cure in contact with the positioner. When the epoxy is fully cured, the wax is melted and the positioner withdrawn.
- i -
Description
This invention relates to a method and apparatus for positioning a light output device such as a laser diode relative to a light input device such as the end surface of an optical waveguide so as to maximize light launched from the laser diode into the waveguide.
Conventionally in the assembly of laser diode packages, in order to achieve a maximum amount of ligh-t coupled into a fiber From a laser, micropositioners are used to manipulate the fiber manually in Front of the lasing junction. Light from a remote end of the fiber or fiber pigtail is detected and generates a DC level. The fiber is manipulated in front of the laser in a liquid epoxy or low melting point solder and when the DC level is at a maximum, the epoxy is allowed to cure or the low melting point solder is cooled to solidification.
Al-ternatively as described in our co-pending application Serial No. 485,873, filed JunR 28, 1985 in the name of J.C. Goodwin et al, a fiber end facing the laser is vibrated by mechanical means to modulate the coupled light. Positional information contained in the oscillatory component of the output signal can be used to reduce misalignment.
A problem with these arrangements is that some slight movement of the Fiber can take place as the epoxy cures, so con-tinuous monitoring and restoration of the fiber position should take place as late as possible during the curing procedure. In the co pending patent application described previously, the technique used for holding the fiber during epoxy curing is a fork arrangement which contacts the fiber at a point which is spaced away from the position of the epoxy bead. This is necessary to ensure that the epoxy does not cure in contact with the fork arrangement since otherwise, the t positioner cannot be withdrawn after curing is complete. However, when a restoring force is applied to the fork arrangement to counteract a shi-fting tendency of the thickening epoxy, it can lead to a bending of that portion of -the fiber between the epoxy bead and the fork arrangement. To enable pure translation of the fiber back through the curing epoxy and so minimize the chance of bending, the fiber should be held, and the restoring Force applied, at a point on the fiber which is centered on the epoxy bead. However this means that the fiber holding point becomes entrapped in the cured epoxy.
According to the invention there is provided a method of anchoring a fiber to a substrate corrlprising:-attaching a posi-tioner to the fiber using a meltable material so that the positioner is coated by said meltable material and thereby is separated from the fiber by said meltable material;
moving the positioner to position the fiber in a desired position on the substrate so that a part of the fiber and only the coated portion of the positioner is in contact with a bead of curable material;
continuously monitoring the position of the fiber and maintaining the fiber in said desired position as the curable ma-terial cures; and when the curable material is cured, melting said meltable materlal and withdrawing the positioner.
The meltable material is preferably a wax or low melting point plastic, the wax contacting the fiber over only a small surface area thereof. The meltable material can be melted by heat thermally conducted from the positioner.
~ I
%~3~
.
Par-ticulary for use in the method the positioner preferably comprises an elongate probe having a resis-tive heater adjacent its end. The positioner can have a pointed bead of cured silver epoxy the meltable material during use being applied to said poin-ted bead.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:-Figure 1 shows partly in perspective and partly incircuit schematic form apparatus used in a method according to the invention;
Figure 2 shows in graphical form the variation in coupling efFiciency between a laser diode and an optical waveguide resulting when the input end of the waveguide is vibrated;
Figure 3 shows the vibration and oscillatory component of detected light applied to a common time base; and Figure 4 is a sectional view showing interengagement between a Fiber and a fiber end positioner used in the me-thod.
Referring in detail to Figure 1 there is shown a laser diode 10 a pigtail fiber 12 and an optical de-tec-tor 14. A
piezoelectric crystal 16 drives the fiber end 20 in the x-direction in response to an oscillatory signal at Frequency fx from a generator 24 summed with a DC level 38 from a phase sensitive detector 28. Similarly a piezoelectric crystal 18 drives the fiber end in the y-direction in response to an oscillatory signal at a frequency fy froln a generator 26 summed with a DC level 40 from a phase sensitive detector 30. The DC levels are derived by detecting variation in coupled light resulting from the impressed modulation at fx and fy and are maintained at levels which rnaxirnize the coupled light.
The invention finds particular application in the assembly of a laser diode package. In the package, the laser diode chip 10 is normally bonded to a heat sink. The pigtail fiber 12 passes through a hermetic seal in the wall of a package housing and an end portion 20 of -the fiber rests over a pedestals -the height of which is marginally lower than the height of the lasing junction within the laser chip lOo An important step in the assembly of a laser diode package is the accurate positioning of -the pigtail fiber end 20 to maximize light launched from the laser chip 10. Typically at a distance oF several tens of microns from the laser emitting facet, the light coupling profile is as shown in Figure 2 and spreads over a diameter of 5 to 10 microns, the pigtail fiber i-tself typically having a core radius of 10 microns. To maximize light coupling from the laser chip 10, the fiber pigtail end portion 20 can be both tapered and rendered bulb ended to provide a lens action. Even so, the most important considera-tion in maximizing light launched into the fiber 12 is in having the axis of the fiber end portion 20 accurately aligned with laser emi-tting spot 44.
In a method utilizing the present invention, light coupled from laser 10 into the fiber near end 20 is detected at a remote end 21 by a PIN or avalanche photodiode 14 mounted to receive light from the pigtail fiber. A corresponding detector output is taken through an amplifier 42 to a signal analysing circuit including 25 the phase sensitive detectors 28, 30. The fiber end 20 is moved in a mass of liquid epoxy 45 by energizing pièzoelectric crystals 16, 18.
~ Crystals 16 and 18 produce x and y-directional movement, respectively, : 4 7~ 3 ~ ~
where -the Fiber axis extends along the z-direction, the x and J
movement being combined at an elongate probe 48. Although details of the piezoelectric crystal moun-ting arrangement are not shown, it ~Jill be understood that through the independent action of the crystals the probe 48 can be moved to any spot within a predetermined zone of the xy plane.
Drive -to the piezoelectric crystals 16, 18 is applied -from drive generators 24, 26 which generate oscillatory signals at respective frequencies fx and fy~ The frequencies selected are not harmonically related. For ef-Fective operation of the phase sensitive detectors, fx and fy are greater than 10 Hz and are separated by at least 10 Hz to allow easy discrimination. A first output signal from each drive generator is taken through a summing junction 50 to a drive ampliFier 52 and then applied to its corresponding piezoelectric crystal.
Second outputs from the drive generators 24, 26 are applied as reference signals -to respective phase sensi-tive detec-tors 28, 30. The reference signals permit the phase relationship between the applied vibration and the detected signal to be determined. Delay D is introduced to compensa-te for the round trip time of the ac drive producing vibration and the detected signals re-turning to the detectors 28, 30. If the signals are in phase, then the fiber end 21 must be moved in one direction to increase coupling whereas if the signals are out of phase then the fiber end must be moved in the opposite direction.
The light coupling ef-Ficiency between the laser output facet and fiber as a function of misalignment in the x-direction is 3~
typically as shown in Figure 2. Ideally the fiber is positioned at d point C corresponding to the fiber and laser being accurately aligned a-t the x-direction. In fact, after ini-tial positioning of the fiber end rela-tive to the laser, the fiber is typically at a position 'A' or 'B' on one side or other o-f the optimal posi-tion 'C'. When the signal at frequency fx is applied to the piezoelectric crys-tal 16, the fiber end is oscillated as represented by arrow 54 (Figure 1) and waveform 'i'. At the detector 14, a corresponding electrical signal is generated having in addition to a DC component, an oscillatory component Wa, Wb or Wc depending on the median position of the fiber.
For accurate alignment, the fiber should be in a position in which the amplitude of -the oscillatory component is minimized as shown by waveform Wc. The waveforms~are shown with a common time base in Figure 3 which also shows their phase relationship. The phase ser,sitive detector 28 is tuned to frequency fx and, dependent on the amplitude and phase difference between the input signal from the drive generator 24 and tha-t from the detector 14, a DC control signal is generated which is summed with the AC drive from drive genera-tor 24 at the summing junction 50. The control signal is used to effect x-direction translational movement of the active surface of piezoelectric crystal 16 and thereby the pigtail fiber end 20. As shown in Figure 3, it is evident from the amplitude of waveforms Wa and Wb -that movement of the fiber is required to provide effective alignment. Moreover it is clear from the phase relationship of Wa and Wb relative to waveform 'i' in which direction the fiber should be moved to effect alignment.
A corresponding adjustment is effected in the ? ~
y-direction by vibrating -the fiber end 20 a-t a different Frequency fy and analysing the fy oscillatory component of the detected signal to derive its amplitude and phase relationship to the impressed modulation.
As previously indicated, this method finds particular application in fixing a fiber relative to a laser chip. In a particular implementation of that me-thodg -the fiber end portion 20 is held in the bead 45 of epoxy resin wi-th the fiber end surface i-tself clear o-F-the epoxy bead to permit light to be coupled directly into the Fiber. The epoxy is cured once the x and y control loops have been energized to fix the fiber end portion in its most effective position. It has been found that as epoxy resin is cured, the fiber end portion 20 can be moved of the order o-f 1 micron merely as a result of the curing mechanism. With the dynamic method described, if there is some movement of -the fiber during curing, a res-torative force is applied during the initial curing stage.
To ensure that translational movemen-t of the fiber through the epoxy rather than fiber bending takes place, the fiber is held, and the restoring force applied, at a point on the fiber which is centered in -the epoxy bead 45 as shown in Figure 4.
A holding tip 70 forming part of probe 48 is attached to the -Fiber by a layer 72 of Fusible material such as wax3 or low melting point plastic. A compact resistive heater 74 which is used to melt the fusible material 72, is soldered to the end of the elongate probe 48 which comprises a sliver of double-sided printed circuit board along which electrical current to the heater 74 is applied. To disturb the epoxy attachment as little as possible, the holding tip 70 ,.
contacts the fiber 20 over a short length (a few fiber diameters or less). The tip is made by forming a cone of silver epoxy paste on th~
bottom of the resistive heater 74. When the desired tip shape has been achieved, heater current is applied to -the chip resistor 74 to heat and thereby cure the silver epoxy. When the silver epoxy has cured, black wax 72 is melted onto the hot tip to thoroughly coat it.
To ini-tially cap-ture the fiber be-Fore alignment, the cold heater tip 70 is moved into contact with the fiber 20. Then heater current is applied and the molten wax is allowed to flow into contact with the fiber. The heater current is then removed and when the wax solifies, the top of the fiber is held firmly to the holder tip by the cold wax. The entire Fiber and tip assembly is then immersed in the uncured epoxy bead 45 located on a copper block sub mount 75 and the fiber positioned by movement of the holder 48 until optimum coupling is achieved. The epoxy 45 is then UV or air cured around the wax-coated holding tip 70. During at least the early portion of the curing, the real -time alignmen-t system is operated to counteract any shiFting of the fiber caused by the epoxy. When the epoxy has fully cured, the holder tip is retrieved simply by applying heater current to mel-t the wax. As long as the wax originally covers enough oF-the tip to shield it from direct contact with the epoxy as shown in Figure 49 it can easily be pulled freeO
Using this holder/positioner the fiber does not have to be bent to obtain alignmen-t with the laser. This ensures that no stress is frozen in when the epoxy cures and the loss in coupling efficiency caused by slight laser-fiber angular misalignment is avoided. Using the wax fixture, the fiber is held firmly by the positioning apparatus, allowing for a strong restorative force to be applied in all directions perpendicular to the fiber axis. Since the fiber is held at a point actually inside the epoxy, this permits the use of very strong restoring forces without Fiber bending.
Although the invention has been described in terms of a pigtail fiber 12 being fixed relative to a laser chip 10, the method can be used to precisely align other fiberoptic input and output devices. Thus the method can be used in aligning fibers for coupling light at a connector or splice site. It will be appreciated that although in this particular embodiment the light input device is vibrated, in an alternative embodiment the light input device can be fixed and the light output device vibrated.
The arrangement described above uses the same piezoelectric device to effect both the applied vibra-tion and the translational movement. It will be understood that different mechanisms may be used for these different tasks. For instance, the vibration can be applied sonically using a loudspeaker, and the piezoelectric devices used only to effect the restoring translational movement of the fiber.
Although in the embodiment described the positioner is fully withdrawn from the anchored Fiber when the wax melts, the positioner is alternatively fabricated with a sacrificial tip which is joined to the main positioner body with a meltable material. The tip is immersed directly into the epoxy bead during fiber positioning and is left there after the epoxy cures,
Conventionally in the assembly of laser diode packages, in order to achieve a maximum amount of ligh-t coupled into a fiber From a laser, micropositioners are used to manipulate the fiber manually in Front of the lasing junction. Light from a remote end of the fiber or fiber pigtail is detected and generates a DC level. The fiber is manipulated in front of the laser in a liquid epoxy or low melting point solder and when the DC level is at a maximum, the epoxy is allowed to cure or the low melting point solder is cooled to solidification.
Al-ternatively as described in our co-pending application Serial No. 485,873, filed JunR 28, 1985 in the name of J.C. Goodwin et al, a fiber end facing the laser is vibrated by mechanical means to modulate the coupled light. Positional information contained in the oscillatory component of the output signal can be used to reduce misalignment.
A problem with these arrangements is that some slight movement of the Fiber can take place as the epoxy cures, so con-tinuous monitoring and restoration of the fiber position should take place as late as possible during the curing procedure. In the co pending patent application described previously, the technique used for holding the fiber during epoxy curing is a fork arrangement which contacts the fiber at a point which is spaced away from the position of the epoxy bead. This is necessary to ensure that the epoxy does not cure in contact with the fork arrangement since otherwise, the t positioner cannot be withdrawn after curing is complete. However, when a restoring force is applied to the fork arrangement to counteract a shi-fting tendency of the thickening epoxy, it can lead to a bending of that portion of -the fiber between the epoxy bead and the fork arrangement. To enable pure translation of the fiber back through the curing epoxy and so minimize the chance of bending, the fiber should be held, and the restoring Force applied, at a point on the fiber which is centered on the epoxy bead. However this means that the fiber holding point becomes entrapped in the cured epoxy.
According to the invention there is provided a method of anchoring a fiber to a substrate corrlprising:-attaching a posi-tioner to the fiber using a meltable material so that the positioner is coated by said meltable material and thereby is separated from the fiber by said meltable material;
moving the positioner to position the fiber in a desired position on the substrate so that a part of the fiber and only the coated portion of the positioner is in contact with a bead of curable material;
continuously monitoring the position of the fiber and maintaining the fiber in said desired position as the curable ma-terial cures; and when the curable material is cured, melting said meltable materlal and withdrawing the positioner.
The meltable material is preferably a wax or low melting point plastic, the wax contacting the fiber over only a small surface area thereof. The meltable material can be melted by heat thermally conducted from the positioner.
~ I
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.
Par-ticulary for use in the method the positioner preferably comprises an elongate probe having a resis-tive heater adjacent its end. The positioner can have a pointed bead of cured silver epoxy the meltable material during use being applied to said poin-ted bead.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:-Figure 1 shows partly in perspective and partly incircuit schematic form apparatus used in a method according to the invention;
Figure 2 shows in graphical form the variation in coupling efFiciency between a laser diode and an optical waveguide resulting when the input end of the waveguide is vibrated;
Figure 3 shows the vibration and oscillatory component of detected light applied to a common time base; and Figure 4 is a sectional view showing interengagement between a Fiber and a fiber end positioner used in the me-thod.
Referring in detail to Figure 1 there is shown a laser diode 10 a pigtail fiber 12 and an optical de-tec-tor 14. A
piezoelectric crystal 16 drives the fiber end 20 in the x-direction in response to an oscillatory signal at Frequency fx from a generator 24 summed with a DC level 38 from a phase sensitive detector 28. Similarly a piezoelectric crystal 18 drives the fiber end in the y-direction in response to an oscillatory signal at a frequency fy froln a generator 26 summed with a DC level 40 from a phase sensitive detector 30. The DC levels are derived by detecting variation in coupled light resulting from the impressed modulation at fx and fy and are maintained at levels which rnaxirnize the coupled light.
The invention finds particular application in the assembly of a laser diode package. In the package, the laser diode chip 10 is normally bonded to a heat sink. The pigtail fiber 12 passes through a hermetic seal in the wall of a package housing and an end portion 20 of -the fiber rests over a pedestals -the height of which is marginally lower than the height of the lasing junction within the laser chip lOo An important step in the assembly of a laser diode package is the accurate positioning of -the pigtail fiber end 20 to maximize light launched from the laser chip 10. Typically at a distance oF several tens of microns from the laser emitting facet, the light coupling profile is as shown in Figure 2 and spreads over a diameter of 5 to 10 microns, the pigtail fiber i-tself typically having a core radius of 10 microns. To maximize light coupling from the laser chip 10, the fiber pigtail end portion 20 can be both tapered and rendered bulb ended to provide a lens action. Even so, the most important considera-tion in maximizing light launched into the fiber 12 is in having the axis of the fiber end portion 20 accurately aligned with laser emi-tting spot 44.
In a method utilizing the present invention, light coupled from laser 10 into the fiber near end 20 is detected at a remote end 21 by a PIN or avalanche photodiode 14 mounted to receive light from the pigtail fiber. A corresponding detector output is taken through an amplifier 42 to a signal analysing circuit including 25 the phase sensitive detectors 28, 30. The fiber end 20 is moved in a mass of liquid epoxy 45 by energizing pièzoelectric crystals 16, 18.
~ Crystals 16 and 18 produce x and y-directional movement, respectively, : 4 7~ 3 ~ ~
where -the Fiber axis extends along the z-direction, the x and J
movement being combined at an elongate probe 48. Although details of the piezoelectric crystal moun-ting arrangement are not shown, it ~Jill be understood that through the independent action of the crystals the probe 48 can be moved to any spot within a predetermined zone of the xy plane.
Drive -to the piezoelectric crystals 16, 18 is applied -from drive generators 24, 26 which generate oscillatory signals at respective frequencies fx and fy~ The frequencies selected are not harmonically related. For ef-Fective operation of the phase sensitive detectors, fx and fy are greater than 10 Hz and are separated by at least 10 Hz to allow easy discrimination. A first output signal from each drive generator is taken through a summing junction 50 to a drive ampliFier 52 and then applied to its corresponding piezoelectric crystal.
Second outputs from the drive generators 24, 26 are applied as reference signals -to respective phase sensi-tive detec-tors 28, 30. The reference signals permit the phase relationship between the applied vibration and the detected signal to be determined. Delay D is introduced to compensa-te for the round trip time of the ac drive producing vibration and the detected signals re-turning to the detectors 28, 30. If the signals are in phase, then the fiber end 21 must be moved in one direction to increase coupling whereas if the signals are out of phase then the fiber end must be moved in the opposite direction.
The light coupling ef-Ficiency between the laser output facet and fiber as a function of misalignment in the x-direction is 3~
typically as shown in Figure 2. Ideally the fiber is positioned at d point C corresponding to the fiber and laser being accurately aligned a-t the x-direction. In fact, after ini-tial positioning of the fiber end rela-tive to the laser, the fiber is typically at a position 'A' or 'B' on one side or other o-f the optimal posi-tion 'C'. When the signal at frequency fx is applied to the piezoelectric crys-tal 16, the fiber end is oscillated as represented by arrow 54 (Figure 1) and waveform 'i'. At the detector 14, a corresponding electrical signal is generated having in addition to a DC component, an oscillatory component Wa, Wb or Wc depending on the median position of the fiber.
For accurate alignment, the fiber should be in a position in which the amplitude of -the oscillatory component is minimized as shown by waveform Wc. The waveforms~are shown with a common time base in Figure 3 which also shows their phase relationship. The phase ser,sitive detector 28 is tuned to frequency fx and, dependent on the amplitude and phase difference between the input signal from the drive generator 24 and tha-t from the detector 14, a DC control signal is generated which is summed with the AC drive from drive genera-tor 24 at the summing junction 50. The control signal is used to effect x-direction translational movement of the active surface of piezoelectric crystal 16 and thereby the pigtail fiber end 20. As shown in Figure 3, it is evident from the amplitude of waveforms Wa and Wb -that movement of the fiber is required to provide effective alignment. Moreover it is clear from the phase relationship of Wa and Wb relative to waveform 'i' in which direction the fiber should be moved to effect alignment.
A corresponding adjustment is effected in the ? ~
y-direction by vibrating -the fiber end 20 a-t a different Frequency fy and analysing the fy oscillatory component of the detected signal to derive its amplitude and phase relationship to the impressed modulation.
As previously indicated, this method finds particular application in fixing a fiber relative to a laser chip. In a particular implementation of that me-thodg -the fiber end portion 20 is held in the bead 45 of epoxy resin wi-th the fiber end surface i-tself clear o-F-the epoxy bead to permit light to be coupled directly into the Fiber. The epoxy is cured once the x and y control loops have been energized to fix the fiber end portion in its most effective position. It has been found that as epoxy resin is cured, the fiber end portion 20 can be moved of the order o-f 1 micron merely as a result of the curing mechanism. With the dynamic method described, if there is some movement of -the fiber during curing, a res-torative force is applied during the initial curing stage.
To ensure that translational movemen-t of the fiber through the epoxy rather than fiber bending takes place, the fiber is held, and the restoring force applied, at a point on the fiber which is centered in -the epoxy bead 45 as shown in Figure 4.
A holding tip 70 forming part of probe 48 is attached to the -Fiber by a layer 72 of Fusible material such as wax3 or low melting point plastic. A compact resistive heater 74 which is used to melt the fusible material 72, is soldered to the end of the elongate probe 48 which comprises a sliver of double-sided printed circuit board along which electrical current to the heater 74 is applied. To disturb the epoxy attachment as little as possible, the holding tip 70 ,.
contacts the fiber 20 over a short length (a few fiber diameters or less). The tip is made by forming a cone of silver epoxy paste on th~
bottom of the resistive heater 74. When the desired tip shape has been achieved, heater current is applied to -the chip resistor 74 to heat and thereby cure the silver epoxy. When the silver epoxy has cured, black wax 72 is melted onto the hot tip to thoroughly coat it.
To ini-tially cap-ture the fiber be-Fore alignment, the cold heater tip 70 is moved into contact with the fiber 20. Then heater current is applied and the molten wax is allowed to flow into contact with the fiber. The heater current is then removed and when the wax solifies, the top of the fiber is held firmly to the holder tip by the cold wax. The entire Fiber and tip assembly is then immersed in the uncured epoxy bead 45 located on a copper block sub mount 75 and the fiber positioned by movement of the holder 48 until optimum coupling is achieved. The epoxy 45 is then UV or air cured around the wax-coated holding tip 70. During at least the early portion of the curing, the real -time alignmen-t system is operated to counteract any shiFting of the fiber caused by the epoxy. When the epoxy has fully cured, the holder tip is retrieved simply by applying heater current to mel-t the wax. As long as the wax originally covers enough oF-the tip to shield it from direct contact with the epoxy as shown in Figure 49 it can easily be pulled freeO
Using this holder/positioner the fiber does not have to be bent to obtain alignmen-t with the laser. This ensures that no stress is frozen in when the epoxy cures and the loss in coupling efficiency caused by slight laser-fiber angular misalignment is avoided. Using the wax fixture, the fiber is held firmly by the positioning apparatus, allowing for a strong restorative force to be applied in all directions perpendicular to the fiber axis. Since the fiber is held at a point actually inside the epoxy, this permits the use of very strong restoring forces without Fiber bending.
Although the invention has been described in terms of a pigtail fiber 12 being fixed relative to a laser chip 10, the method can be used to precisely align other fiberoptic input and output devices. Thus the method can be used in aligning fibers for coupling light at a connector or splice site. It will be appreciated that although in this particular embodiment the light input device is vibrated, in an alternative embodiment the light input device can be fixed and the light output device vibrated.
The arrangement described above uses the same piezoelectric device to effect both the applied vibra-tion and the translational movement. It will be understood that different mechanisms may be used for these different tasks. For instance, the vibration can be applied sonically using a loudspeaker, and the piezoelectric devices used only to effect the restoring translational movement of the fiber.
Although in the embodiment described the positioner is fully withdrawn from the anchored Fiber when the wax melts, the positioner is alternatively fabricated with a sacrificial tip which is joined to the main positioner body with a meltable material. The tip is immersed directly into the epoxy bead during fiber positioning and is left there after the epoxy cures,
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-
1. A method of anchoring a fiber to a substrate comprising:
attaching a positioner to the fiber using a meltable Material so that the positioner is separated from the fiber by said Meltable material;
moving the positioner to position the fiber in a desired position on the substrate so that the meltable material and a part of the fiber, but not the positioner are in contact with a bead of curable material which in turn is in contact with the substrate;
continuously monitoring the position of the fiber and maintaining the fiber in said desired position as the curable material cures and anchors the fiber to the substrate, and when the curable material is cured, melting said meltable material and withdrawing the positioner.
attaching a positioner to the fiber using a meltable Material so that the positioner is separated from the fiber by said Meltable material;
moving the positioner to position the fiber in a desired position on the substrate so that the meltable material and a part of the fiber, but not the positioner are in contact with a bead of curable material which in turn is in contact with the substrate;
continuously monitoring the position of the fiber and maintaining the fiber in said desired position as the curable material cures and anchors the fiber to the substrate, and when the curable material is cured, melting said meltable material and withdrawing the positioner.
2. A method as claimed in claim 1 in which the meltable material is a wax.
3. A method as claimed in claim 1 in which the positioner has a pointed tip and the meltable material is coated on an end part of the tip.
4. A method as claimed in claim 1, 2 or 3 wherein the positioner houses a resistive heater.
5. A method as claimed in claim 1, 2 or 3 in which the position of the fiber during curing of the curable material is monitored by directing light from a laser into an end of the fiber adjacent to the bead of curable material, monitoring the output of light at a remote position of the fiber and moving the position of the fiber within said epoxy bead to maximize the level of monitored light.
6. A method of anchoring a fiber to a substrate as defined in claim 1, further including moving the positioner so that the positioner and the meltable material are substantially centered in the curable material as the material cures.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000486031A CA1262304A (en) | 1985-06-28 | 1985-06-28 | Laser-fiber positioner |
| US06/797,328 US4679908A (en) | 1985-06-28 | 1985-11-12 | Laser-fiber positioning method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000486031A CA1262304A (en) | 1985-06-28 | 1985-06-28 | Laser-fiber positioner |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1262304A true CA1262304A (en) | 1989-10-17 |
Family
ID=4130893
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000486031A Expired CA1262304A (en) | 1985-06-28 | 1985-06-28 | Laser-fiber positioner |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4679908A (en) |
| CA (1) | CA1262304A (en) |
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| DE3413667A1 (en) * | 1984-04-11 | 1985-10-17 | Siemens AG, 1000 Berlin und 8000 München | METHOD FOR ADJUSTING A COUPLING OPTICS PROVIDED AT THE END OF AN OPTICAL WAVE GUIDE TO A SEMICONDUCTOR LASER, AND DEVICE FOR CARRYING OUT THE METHOD |
| DE3534017A1 (en) * | 1985-09-24 | 1987-03-26 | Siemens Ag | METHOD FOR COUPLING A LASER DIODE TO A MONOMODE LIGHT WAVE GUIDE, AND AN ARRANGEMENT OF A LASER DIODE AND A LIGHT WAVE GUIDE COUPLED TO IT |
| US4725128A (en) * | 1985-11-20 | 1988-02-16 | Medtronic, Inc. | Method for delivering light from multiple light emitting diodes over a single optical fiber |
| US5222170A (en) * | 1987-04-03 | 1993-06-22 | Bt&D Technologies Ltd. | Optical fiber device fabrication |
| US4747657A (en) * | 1987-06-15 | 1988-05-31 | American Telephone And Telegraph Company | Achieving improved radial alignment in an optical package |
| JPH0675023B2 (en) * | 1988-01-30 | 1994-09-21 | 株式会社フジクラ | Optical fiber splice loss estimation method |
| US4984885A (en) * | 1989-12-15 | 1991-01-15 | General Electric Company | Method and apparatus for high power optical fiber injection and alignment |
| JPH04309907A (en) * | 1991-04-09 | 1992-11-02 | Mitsubishi Electric Corp | Manufacture of photosemiconductor element module |
| US5217906A (en) * | 1991-12-03 | 1993-06-08 | At&T Bell Laboratories | Method of manufacturing an article comprising an opto-electronic device |
| US5383118A (en) * | 1992-09-23 | 1995-01-17 | At&T Corp. | Device alignment methods |
| EP0927375B1 (en) * | 1995-06-07 | 2002-02-20 | McDonnell Douglas Corporation | An alignment apparatus for precisely aligning an optical fiber and an associated fabrication method |
| US5602955A (en) * | 1995-06-07 | 1997-02-11 | Mcdonnell Douglas Corporation | Microactuator for precisely aligning an optical fiber and an associated fabrication method |
| US5606635A (en) * | 1995-06-07 | 1997-02-25 | Mcdonnell Douglas Corporation | Fiber optic connector having at least one microactuator for precisely aligning an optical fiber and an associated fabrication method |
| US5745624A (en) * | 1996-08-23 | 1998-04-28 | The Boeing Company | Automatic alignment and locking method and apparatus for fiber optic module manufacturing |
| JPH1096839A (en) * | 1996-09-20 | 1998-04-14 | Sumitomo Electric Ind Ltd | Production of semiconductor laser module |
| US6198580B1 (en) | 1998-08-17 | 2001-03-06 | Newport Corporation | Gimballed optical mount |
| US6430337B1 (en) | 1998-09-03 | 2002-08-06 | Agere Systems Optoelectronics Guardian Corp. | Optical alignment system |
| US6516130B1 (en) | 1998-12-30 | 2003-02-04 | Newport Corporation | Clip that aligns a fiber optic cable with a laser diode within a fiber optic module |
| US6996506B2 (en) * | 1999-02-23 | 2006-02-07 | Newport Corporation | Process and device for displacing a moveable unit on a base |
| FR2790115B1 (en) | 1999-02-23 | 2001-05-04 | Micro Controle | METHOD AND DEVICE FOR MOVING A MOBILE ON AN ELASTICALLY MOUNTED BASE |
| US6511035B1 (en) | 1999-08-03 | 2003-01-28 | Newport Corporation | Active vibration isolation systems with nonlinear compensation to account for actuator saturation |
| SE519332C2 (en) * | 2000-06-22 | 2003-02-18 | Ericsson Telefon Ab L M | Method and apparatus for forming an end surface of an optical fiber as well as computer software and computer software |
| US6531947B1 (en) | 2000-09-12 | 2003-03-11 | 3M Innovative Properties Company | Direct acting vertical thermal actuator with controlled bending |
| US6483419B1 (en) | 2000-09-12 | 2002-11-19 | 3M Innovative Properties Company | Combination horizontal and vertical thermal actuator |
| US6708491B1 (en) | 2000-09-12 | 2004-03-23 | 3M Innovative Properties Company | Direct acting vertical thermal actuator |
| US6655840B2 (en) | 2001-02-13 | 2003-12-02 | Newport Corporation | Stiff cross roller bearing configuration |
| US6601524B2 (en) | 2001-03-28 | 2003-08-05 | Newport Corporation | Translation table with a spring biased dovetail bearing |
| US6791058B2 (en) | 2001-04-25 | 2004-09-14 | Newport Corporation | Automatic laser weld machine for assembling photonic components |
| US6438954B1 (en) | 2001-04-27 | 2002-08-27 | 3M Innovative Properties Company | Multi-directional thermal actuator |
| US6568666B2 (en) | 2001-06-13 | 2003-05-27 | Newport Corporation | Method for providing high vertical damping to pneumatic isolators during large amplitude disturbances of isolated payload |
| US6619611B2 (en) | 2001-07-02 | 2003-09-16 | Newport Corporation | Pneumatic vibration isolator utilizing an elastomeric element for isolation and attenuation of horizontal vibration |
| US20030030869A1 (en) * | 2001-08-08 | 2003-02-13 | International Business Machines Corporation | Active real-time alignment system for optoelectronic (OE) devices |
| US6966535B2 (en) | 2002-05-07 | 2005-11-22 | Newport Corporation | Snubber for pneumatically isolated platforms |
| CN1726415B (en) * | 2002-12-13 | 2010-06-09 | 皇家飞利浦电子股份有限公司 | Optical system and image projection system |
| US7320455B2 (en) | 2003-10-24 | 2008-01-22 | Newport Corporation | Instrumented platform for vibration-sensitive equipment |
| US8231098B2 (en) | 2004-12-07 | 2012-07-31 | Newport Corporation | Methods and devices for active vibration damping of an optical structure |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4237474A (en) * | 1978-10-18 | 1980-12-02 | Rca Corporation | Electroluminescent diode and optical fiber assembly |
| US4296998A (en) * | 1979-12-17 | 1981-10-27 | Bell Telephone Laboratories, Incorporated | Encapsulated light source with coupled fiberguide |
| JPS57138191A (en) * | 1981-02-19 | 1982-08-26 | Kokusai Denshin Denwa Co Ltd <Kdd> | United structure of semiconductor laser and optical fiber |
| US4469399A (en) * | 1981-12-30 | 1984-09-04 | The United States Of America As Represented By The Secretary Of The Navy | Method of making an undersea, high pressure bulkhead penetrator for use with fiber optic cables |
-
1985
- 1985-06-28 CA CA000486031A patent/CA1262304A/en not_active Expired
- 1985-11-12 US US06/797,328 patent/US4679908A/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US4679908A (en) | 1987-07-14 |
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