WO1998033287A1 - Communications system with star topology - Google Patents
Communications system with star topology Download PDFInfo
- Publication number
- WO1998033287A1 WO1998033287A1 PCT/GB1998/000169 GB9800169W WO9833287A1 WO 1998033287 A1 WO1998033287 A1 WO 1998033287A1 GB 9800169 W GB9800169 W GB 9800169W WO 9833287 A1 WO9833287 A1 WO 9833287A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- network
- routers
- nodes
- node
- optical
- Prior art date
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0287—Protection in WDM systems
- H04J14/0297—Optical equipment protection
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
- H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
- H04J14/0242—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON
- H04J14/0245—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for downstream transmission, e.g. optical line terminal [OLT] to ONU
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
- H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
- H04J14/0242—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON
- H04J14/0249—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for upstream transmission, e.g. ONU-to-OLT or ONU-to-ONU
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0278—WDM optical network architectures
- H04J14/0282—WDM tree architectures
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0287—Protection in WDM systems
- H04J14/0293—Optical channel protection
- H04J14/0295—Shared protection at the optical channel (1:1, n:m)
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0278—WDM optical network architectures
- H04J14/028—WDM bus architectures
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0278—WDM optical network architectures
- H04J14/0283—WDM ring architectures
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q11/0066—Provisions for optical burst or packet networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0007—Construction
- H04Q2011/0009—Construction using wavelength filters
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0007—Construction
- H04Q2011/0011—Construction using wavelength conversion
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0007—Construction
- H04Q2011/0013—Construction using gating amplifiers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0007—Construction
- H04Q2011/0015—Construction using splitting combining
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0007—Construction
- H04Q2011/0018—Construction using tunable transmitters or receivers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
- H04Q2011/0037—Operation
- H04Q2011/0043—Fault tolerance
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q2011/0079—Operation or maintenance aspects
- H04Q2011/0081—Fault tolerance; Redundancy; Recovery; Reconfigurability
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q2011/009—Topology aspects
- H04Q2011/0092—Ring
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q2011/009—Topology aspects
- H04Q2011/0094—Star
Definitions
- the present invention relates to a communications system which employs a network which has a star topology, and particularly, but not exclusively, to networks employing wavelength division multiplexing (WDM).
- WDM wavelength division multiplexing
- WDM has attracted considerable interest as a technology which potentially makes it possible to utilise fully and flexibly the bandwidth available on optical networks Its use has been proposed, for example, in the core network which interconnects trunk switches in a national telecommunications network.
- a variety of different network structures and switching techniques are possible for implementing a WDM network. These include a star network which may, for example, have connections from N nodes converging on a single NxN WDM router at the hub.
- An alternative structure is a WDM add/drop multiplex (ADM) ring in which each node adds and drops wavelength channels to and from other nodes. Further alternatives include a WDM broadcast-and-select ring, and an arbitrary mesh.
- an optical communications system comprising: a) a network having a star topology; b) a plurality of nodes which are located at the periphery of the network, each node including: a plurality of wavelength division multiplexing terminals, each wavelength division multiplexing terminal being arranged to _ _
- WDM terminal is used to denote a device which terminates a WDM channel, and will typically comprise an electro-optical transmitter or receiver.
- terminals are located at a trunk switch which concentrates and distributes traffic via access networks which may include both optical and electrical access networks.
- the present invention provides a network which has a simple regular network structure, and which needs reduced fibre lengths by comparison, for example, with WDM rings, but which at the same time provides greatly enhanced resilience by comparison with conventional star networks and WDM rings
- This is achieved by using in parallel, at the hub of the network, a number of routers, each one of which is undersized with respect to the total network capacity. That is to say, if the network comprises N nodes, then each router has the capacity to handle only a fraction of the capacity of one node on each of its N inputs. At the same time, the total capacity integrated over all of the different routers is greater than the network capacity This provides the network with the flexibility to implement alternative routing of traffic in the event of the failure of one or more components.
- an optical communications system comprising: a) a network having a star topology; b) a plurality of nodes which are located at the periphery of the network, and which are arranged to communicate optical signals with other nodes via the hub of the network ; and c) a plurality of routers connected to the hub of the network, each one of the routers having a capacity which is less than the capacity of the network as a whole, and the routers in total having a capacity which is greater than that of the network as a whole, and each of the routers being connected in parallel to a plurality of the said nodes.
- the system further comprises an optical switch which is connected to the network, and which is operable to select alternative paths for traffic between the node and another node.
- the system also includes a controller which is connected to the optical switch and which is arranged automatically to select one of the alternative paths in response to the detection of a fault condition in another of the alternative paths.
- Such an arrangement may be used, for example, to bypass one of the routers in the event of a failure at that router, or to bypass a failed fibre.
- the plurality of routers include a working router which is arranged to carry working traffic only and a standby router which is arranged to carry protection traffic only.
- different ones of the said plurality of routers are located at different sites.
- the allocation of a router to function as a working router or as a standby router need not be fixed. Rather, a router may be functioning as a working router at one time, and at another time the network may be configured so that that same router functions as a standby router. It is found that the resilience and cost efficiency of this network is further maximised if routers are allocated either to working traffic or to standby traffic.
- Standby traffic is traffic which is diverted from its usual working path in the event of a component failure. Locating different routers at different sites further protects the network from vulnerability to localised damage.
- the network further comprises peripheral transmission paths directly connecting different ones of the plurality of nodes.
- the resilience and efficiency of the system is further enhanced by adding to the basic star network peripheral connections which pass directly between nodes. This makes it possible to ensure that the capacity on the main connections between the nodes and the hub is fully used, and also provides further options for the diversion of standby traffic in response to network or router failures.
- a method of operating an optical communications system comprising a network having a star topology, a plurality of nodes located at the periphery of the network, and a plurality of routers connected to the hub of the network, the method comprising: a) at the nodes, modulating signals onto different WDM channels carried by optical signals at different respective wavelengths; b) outputting some optical signals from a node onto one branch of the network which is connected to one of the plurality of routers, c) outputting other optical signals from the said node onto another branch of the network which is connected to another one of the plurality of the routers; and d) routing WDM channels received by the plurality of routers to different destination nodes depending on the wavelength of a respective channel.
- a method of operating an optical communications system comprising a network having a star topology, a plurality of nodes located at the periphery of the network, and a plurality of routers connected to the hub of the network, the method comprising 1 a) at the nodes, outputting optical signals directed to different destination nodes, b) outputting some of the optical signals from a node onto one branch of the network which is connected to one of the plurality of routers; c) outputting others of the optical signals from the said node onto another branch of the network which is connected to another one of the plurality of the routers; and d) at the hub routing signals received at the plurality of routers to different destination nodes .
- Figure 1 is a schematic of a prior art communications system employing a star network:
- Figure 2 is a schematic of a network embodying the present invention
- Figure 3 is a diagram showing in detail an optical switch connected in the network of Figure 2;
- Figure 4 is a diagram showing a multiplexer/demultiplexer suitable for use in the network of Figure 3;
- Figure 5 is a schematic of an alternative multiplexer/demultiplexer structure
- Figure 6 is a schematic showing a second example of a network embodying the present invention
- Figure 7 shows the switching paths at one of the switch nodes of Figure 6
- Figure 8 is a circuit diagram for an experimental implementation of the system of Figure 7.
- Figure 9 is a schematic showing a third example of a network embodying the invention.
- Figure 10 is a schematic showing a fourth example of a network embodying the invention.
- Figure 1 1 is a schematic showing an alternative structure for a router;
- Figure 1 2 shows the distribution of channels from one node between working routers
- Figures 13a and 13b show examples of routers implementing the distibution scheme of Figure 12.
- a conventional communications system includes an optical fibre network 1 which has a star topology.
- a number of nodes 2 are positioned at different locations at the periphery of the network.
- the nodes 2 are connected via the optical fibre network 1 to a router 3 which is located at the hub of the network.
- the router is an NxN passive wavelength division multiplexing router. It interconnects N inputs and N outputs, where N is chosen to be equal to the number of nodes in the network.
- optical amplifiers 4a, 4b are included so that the network operates transparently, that is without opto-electronic conversion and regeneration.
- the nodes 2 includes a number of transmitter terminals 5 and receiver terminals 6.
- the wavelengths of operation of the transmitters and receivers are variable.
- a transmitter terminal at the originating node is tuned to a wavelength channel which is selected in dependence upon the intended destination.
- the signal is then output in the optical domain by the selected terminal, combined with other wavelength channels from other transmitter terminals and travels along the outgoing fibre in the respective branch of the optical fibre network 1 .
- the fibre from the originating node is connected to one of the N input ports of the router 3.
- the router directs the signal internally to one of the N output ports. Which output port is used depends on the wavelength of the signal
- the signal then passes over the optical fibre network to the destination node.
- the destination node separates each wavelength channel, eg by means of a wavelength demultiplexer or a splitter and set of tunable filters. Completely non- blocking operation can be obtained, for any traffic matrix between nodes, by employing wavelength conversion between dummy ports around the router.
- variable transmitters and receivers may be replaced by sets of fixed wavelength transmitters and receivers, with different transmitters and receivers operating at different wavelengths.
- Such a system still functions generally as described above, but with a reduced degree of flexibility.
- wavelength multiplexers may be used to join, e.g., groups of transmitter terminals to an outgoing optical fibre.
- FIG 2 shows a communications system embodying the present invention
- an optical fibre network 1 with a star topology links nodes 2 to the hub 3 of the network.
- the hub comprises a number of NxN routers, each of which is still connected to all of the N nodes but now receives traffic from only a subset of the terminals within each node
- the total capacity of all of the routers in terms of the number of different channels which can be handled by the routers, is greater than the total capacity of the N nodes
- the Figure shows how, at each of the nodes, the transmitter terminals 5 and receiver terminals 6 are divided into groups.
- a first group of transmitter terminals 501 have their outputs coupled by a non-wavelength selective fibre couplers 7 onto the outgoing optical fibre which is referenced 101 . That optical fibre is connected to an input in the first one of the routers, which router is referenced 301 .
- a second group of transmitter terminals 502 are coupled via a second optical fibre 1 02 to a second router 302, and the third group of transmitter terminals 503 are connected via a third optical fibre 1 03 to a third router 302.
- receiver terminal groups 601 , 602, 603 are connected to outputs of routers 301 , 302 and 303 respectively.
- Optical switches 9 are connected between the different branches of the network. As described in further detail below, the switches may be operated to bypass one or more of the fibre paths and/or one or more of the routers in the event of a component failure.
- the NxN routers are located at the hub of the network. However, advantageously different physical locations are used for the different routers.
- the routers may be divided between several sites, or each router may be sited individually. In the UK core network, for example, the different sites may all be located within a 10km radius of the geographical centre of the network. The use of different sites further enhances the resilience of the system by reducing the effects on the system of, e.g., accidental damage or fire at a single site.
- the communications system forms the core network of a national telecommunications network. Each node is a trunk switch and is connected to a number of digital local exchanges (DLE's) 8a, 8b.
- DLE's digital local exchanges
- the connections between the DLE's 8 and the nodes 2 may include both broadband circuits using, for example, ATM (asynchronous transport mode) and also conventional narrowband circuits for voice telephony.
- ATM asynchronous transport mode
- narrowband circuits for voice telephony Although for ease of illustration only three nodes are shown, in practice, in the UK core network for example, 23 nodes may be used. Typically, for a system of this size, 1 2 23x23 routers may be used at the hub of the network.
- a first customer S 1 connected to a first DLE 8a makes a call to a second customer S2 connected to a second DLE 8b
- the call is initially set up in a conventional fashion, using network signalling messages to establish a circuit which extends across the core network from the first DLE 8a to the second DLE 8b.
- the node 2a which is functioning as a trunk switch, receives signals from the customer S1 via the DLE 8a in the electrical domain.
- the customer signal is switched electrically to one of the transmitter terminals 501 , which it then modulates For example, in this instance, one of the terminals 501 which are connected to the first optical fibre 101 is selected.
- the wavelength of operation of the selected terminal is set by a traffic or network management system (automatically, manually or by design), depending on the intended destination nodes.
- a traffic or network management system automated, manually or by design
- 45 different wavelengths within the erbium window, with channel spacing of 0.8nm may be used across the network
- Each group of terminals connected to a single branch of the network uses a respective subset of 23 of the 45 possible wavelengths, providing one wavelength channel for each of the other nodes.
- the second wavelength channel ⁇ 2 is selected for the transmitter terminal 501
- An optical carrier at that wavelength modulated with the signal from the customer S1 is output on fibre 101 to router 301 .
- the router 301 routes signals received at the relevant input port at wavelength ⁇ 2 to the output port which is connected via optical fibre 104 to node 2b.
- a receiver terminal which is tuned to the ⁇ 2 channel converts the signal back to the electrical domain
- the signal is relayed via DLE 8b to the destination customer S2.
- a connection is established in the reverse direction via fibre 105, router 301 , and fibre 106. In this way a duplex circuit is provided between the two customers.
- the circuit is part of a multiplex of traffic from different customers which is carried between the nodes.
- Suitable devices for implementing the transmitter terminals 501 include Distributed Bragg Reflector (DBR) lasers and grating-assisted vertical coupler semiconductor lasers. Such devices are tuneable over a 35nm range within the erbium window. Examples of such devices are disclosed in the present applicant's copending International Patent Application no PCT/GB 96/02424 (Applicant's Reference A25036)
- the tuneable source may be in the form of an amplifier and modulator such as those described in D.J Pratt et al , "Tunable Source Options for Race-2070 Project (MUNDI)" Cost 240 workshop, Marcoussis, France 25th October 1 993.
- This design uses a mechanically tuneable optical filter and a semiconductor amplifier/modulator to select a required wavelength channel from a comb of reference wavelengths which are broadcast form a central location to a large number of terminals.
- a tuneable filter is used in combination with a photodiode.
- the filter may be a mechanically tuned Fabry Perot cavity, an angled interference filter, or a tuneable grating filter.
- the signals from the taps t 1 -t4 are taken to an optical switching system which comprises a number of 2x 1 optical switches, such as those available commercially from JDS Optics, connected in a tree structure as shown Fault signals may be handled centrally by network management logic, or may be restricted to the element management level for a faster response.
- An electrical control signal which is generated by network management logic or by element management logic located with the node, is applied to the optical switching system.
- the switches are set to pass the signal from tap T1 , and to block the signals from the other taps
- the optical output from the switching system is passed to a WDM demultiplexer
- the multiplexer splits up the channels which were originally present on the first output fibre, so that one channel is placed on each of the other fibres.
- the set of wavelength channels output onto each fibre includes a spare channel which is normally left empty. This spare channel is marked by a dashed line in the Figure
- Each of the outputs from the demultiplexer is arranged to carry a signal at a wavelength corresponding to the spare channel on the respective output fibre.
- the arrangement illustrated in Figure 3 enables the network to continue functioning in the event of a single failure at a router or in a fibre.
- the illustrated switching system is replicated n times
- Each fibre and router then requires only a small fraction n/(r-n) of additional wavelengths, where r is the number of routers, in order to provide the required degree of resilience.
- a star network which is constructed in this way is far more resilient than the equivalent WDM ring.
- multiple fibre breaks spread around the ring cause node-node connections to become more and more localised within sections of the ring between pairs of breaks.
- a multiple-star structure embodying the present invention by contrast, complete recovery from the effects of multiple breaks or failures is possible.
- the network topology makes possible savings in the lengths of fibre required Calculations by the inventor indicate that in a network covering the United Kingdom, the length of fibre required is 250,000 km less than other competing topologies.
- Figure 4 shows a first example of a router which is suitable for use in the networks described above.
- each array is formed by locating fibres in grooves etched in a silicon substrate.
- an entirely passive router such as that shown in Figure 4 is suitable
- the router is modified to include dummy ports, as shown in Figure 5.
- the dummy ports may be used to carry out wavelength conversion for selected incoming signals, so that, in effect, two or more wavelength channels are assigned to a single route across the network
- FIG. 6 shows a second example of a network embodying the present invention
- An optical fibre network 61 which has a star topology links N switch nodes 62 to the hub 63 of the network.
- a plurality of NxN routers R are located at the hub Groups of optical fibres 64, which are termed "spokes", carry traffic between the switch nodes 62 and the routers R
- peripheral optical fibre connections 65 are connected around the network and provide direct interconnection of adjacent switch nodes
- the peripheral optical fibre connections provide protection against path failure in a way which minimises the total fibre quantities required by the network.
- the enlarged detail in Figure 6 shows optical amplifier chains 66 included in the spokes to provide transparent, that is loss-less, operation The spoke is terminated at the switch node by tuneable WDM transmitters 67 and receivers 68.
- path protection is achieved by providing additional "standby" fibres, that is to say fibres which are additional to those fibres, termed the "working" fibres, needed to carry all the channels of the network when the network is functioning normally.
- the standby fibres may extend along one or more of the working spokes, as shown in Figure 6.
- the standby fibres are grouped together in a standby spoke.
- the standby spoke is then connected to a standby switch which functions only to redirect traffic to/from others of the switch nodes in the event of a path failure.
- the network is configured so that the working and standby paths from any switch node to the router is disjoint. In the example of Figure 6, this is achieved by mesh interconnection between the switch nodes and routers For ease of illustration, connections to and from two only of the spokes are shown.
- the working and standby fibre paths may be arranged in the network in different ways depending on the degree of protection against path failure ("path protection”) or protection against router failure (“router protection”) which is required If there were just two cable routes leaving a node, then to protect against failure in one route would require the number of optical fibres to be doubled, so that each route carried standby fibres for the other route Such protection is termed 1 .1 fibre protection. However, protection can be achieved at less expense if m of the spokes have standby fibres and the standby fibres are shared between
- Possible configurations for the network include: all working traffic from one switch node along one spoke; half along the one spoke and half along an adjacent spoke; one third along the one spoke and one third each along two adjacent spokes.
- the peripheral optical fibre connections may carry both working traffic and protection traffic- protection traffic is traffic which has been diverted from its usual path in response to a path failure
- Additional protection can be achieved if the network has switching flexibility to allow selection of different standby paths in the event of failure, rather than a single predetermined standby path being associated with a given working path
- the network By carrying working traffic between nodes on the peripheral optical fibre connections, the network ensures maximum utilisation of the network capacity while tending to minimise the amount of optical fibre required. If the number of wavelength channels from a node is such that one fibre is not fully filled, then only fully-filled fibres are taken directly to the hub from the node The other wavelength channels are taken via the peripheral optical fibre connections to one or more of the other nodes, and are there combined with other channels to fill a whole fibre to the hub A second fibre pair in the peripheral optical fibre connections is used to provide conventional bi-directional ring protection against breaks The ring is used in both directions simultaneously, so that at most a node- node connection only has to go half way around the ring, instead of all the way When a break occurs in the ring, traffic approaching the break is diverted back along the ring in the opposite direction around the ring, but propagation is still in both directions at any point around the ring the direction of propagation is reversed at nodes adjacent to the break
- each and every working node is connected to all the working routers.
- the routers have the same number of ports as the number of nodes N.
- wavelength conversion is used at the router to map some incoming wavelengths to different wavelength channels. As described in relation to the first embodiment above, in general a given wavelength channel from one node goes to a particular one of the other nodes.
- the fractional capacity is provided by time-division of one of the wavelength channels This is implemented, for example, by periodic tuning of a wavelength converter at the router
- the port on a wavelength router carrying a 5th wavelength channel is connected to a wavelength converter which is tuned, for half of the time, to a wavelength which allows the optical signal to pass to the same destination node as the other 4 of the 4.5 wavelength channels.
- the wavelength converter For the other half of the time the wavelength converter is tuned so that the channel is thereby switched by the router so as to divert the signal to another node-node connection where a .5 channel capacity is required.
- the switching is scheduled with respect to a master clock which is distributed between the nodes.
- Control logic managing traffic at the node selects an appropriate time slot for transmission of signals which form part of the 4.5 wavelength node-node circuit.
- Table 1 shows performance parameters for different path protection strategies which may be implemented on the network of Figure 6.
- the parameters are the fibre increase factor, which is the relative increase in the quantity of fibre required to implement the protection strategy, the proportion of fibre paths (spokes) in the network which can fail simultaneously, and the ratio of these two parameters.
- This last parameter is a measure of the increase in fibre quantity (and hence the cost) of each unit of protection
- the Table includes examples with one working path from each switch node (in which case the peripheral fibre connections carry standby traffic only) and with two working paths from each switch node (in which case the peripheral fibre connections carry working traffic as well as standby traffic)) .
- N the number of switch nodes, is 23.
- Table 1 shows that a large increase in fibre quantities is necessary to ensure protection against a large proportion of simultaneous fibre path failures, as one would expect. Nevertheless, the concomitant fibre increase/unit of protection is at its lowest at this extreme, indicating that the greater the degree of protection, the more efficiently it can be provided.
- fixed standby paths provide very efficient protection, they result in traffic loss when a large proportion of path failures occurs, which flexible standby paths do not However, since in practice the probability of e.g.
- the network is configured for m:N path protection, with all working fibres taken directly to the hub along N spokes, and additional standby fibres taken along m of the spokes A further increase in fibre quantities is needed to account for the peripheral fibre connections which carry the protection traffic.
- the overall increase in fibre quantities for m:N protection is given by:
- FIG. 7 shows in further detail the switching arrangements at one of the switch nodes when the network of Figure 6 is configured for m-N path protection.
- Working traffic is carried directly from the switch node to the router R at the hub along one of the spokes S2. If the working path fails, traffic switched either way around the peripheral fibre connections to a node with an available standby fibre path to the router R along a respective spoke S1 or S3 2x2 optical switches sw in the switch node are configured so that when a node is not making use of standby fibres for its own protection, then protected traffic from other switch nodes received on the peripheral fibre connections passes straight through the switch node.
- the switching arrangement illustrated in Figure 7 may be elaborated to handle multiple sets of standby fibres in the peripheral connections, and to handle standby fibres, in addition to working fibres, in a respective spoke Figure 8 shows an experimental implementation of the arrangement shown schematically in Figure 7.
- the hub contains a 22 x 22 wavelength router, described in further detail below, together with a personal computer which is used to control electromechanical optical switches which are deployed around the wavelength router, to provide path protection switching
- the hub is linked via a 75km go and return path to a major switch node, and via 2 separate 200km standby paths
- the standby paths traverse nominal major switch nodes, which contain optical amplifiers
- the fibre links include attenuators to provide between 25 and 27dB path loss- this corresponds to the extra loss that would be present in a typical installed fibre link Switch losses in the 2x2 optical switches are between 0.5dB and 3dB, depending on position.
- Typical amplifier output powers are + 14dBm to + 1 7dBm.
- the optical SNR (signal/noise ratio) at the receiver is typically better than 20dB in a 0 1 nm bandwidth
- the major switch node contains a 1 6 wavelength WDM transmitter, covering the range from 1 547.74nm, to 1 560.55nm, with 100GHz channel spacing Individual channel wavelengths are optimised for transmission through the router
- the WDM transmitter is externally modulated at a bit rate of 2.5Gb/s for the purposes of measurement.
- the receiver array is represented by the combination of a variable attenuator, mechanically tuneable filter with 0.5nm FWHM bandwidth, and an APD receiver Typical attenuations well in excess of 20dB are required to reduce the power from the preceding EDFA to the level required for a 1 in 10 9 error rate at the receiver for both working and standby paths.
- a sufficient power budget exists to accommodate a 1 6-way splitter (approx 1 3dB) and 1 6 tuneable receivers incorporated into a fully functioning network.
- a m:N path protection strategy was implemented as follows. To simulate a fibre break, switch S1 , on the working path between the hub and the operating major switch node, was operated to open this path.
- the switch was positioned close to the hub, to maximise the deleterious effects of propagation delay.
- a photoelectric detector D 1 is filtered to monitor a wavelength known to originate from this node. This detector then detects the reduction in power caused by the simulated break. The detection of this reduction in power causes a 2x2 optical switch S2 on the transmit side of the node to be thrown.
- a time constant of at least 1 25 ⁇ s is associated with photodetector D 1 .
- This time constant which corresponds in length to one SDH (Synchronous Digital Hierarchy) frame, acts as a persistence check to ensure that a real break has been detected. In the present implementation an effective time constant of a few ms was used.
- S2 After S2 has been thrown, the loss of transmit signal, after propagation back to the hub, is detected by another photoelectric detector D2, which is loosely filtered to discriminate against ASE (amplified spontaneous emission) from the EDFA's (erbium doped fibre amplifiers) .
- ASE amplified spontaneous emission
- the information is sent as a TTL signal to a small personal computer (PC) , which contains a control algorithm to detect the TTL transition and choose an appropriate spare path, based on knowledge of the network condition.
- PC personal computer
- the present implementation of this control algorithm can handle up to 8 nodes, and has a response time of 800 ⁇ s on a 386 PC.
- the appropriate switches are thrown. For example, for Standby Path 1 , switches S4 and S5 are thrown.
- An additional DFB (distributed feedback) laser which may operate outside the mam band occupied by the WDM channels, is placed at the hub. This additional DFB laser generates a probe signal for use in the path restoration process.
- This signal propagates down the standby path to the switch node.
- the signal is detected by a photodetector D 1 .
- This detector which ideally has a faster response time, around 10 ⁇ s, causes switches S9 and S 1 0 at the node to switch, and so brings the standby path into operation.
- D2 which informs the controller that the restoration path is intact. Full restoration only occurs when these signals propagate back to the node, down the standby path (representing propagation via the wavelength router to all other nodes in the network) .
- the wavelength multiplexer which is used as the router is a 22x22 port router with a channel spacing of 0.8 nm. It employs a Stimax (TRADEMARK) multiplexer configuration with a double array of N fibres to provide an NxN WDM multiplexer.
- the Stimax mulitplexer is commercially available from Jobin-Yvon - Spex
- the device provides a maximised ratio of channel width to channel spacing using single-mode fibres (typical FWHM of 0.21 nm) and losses are below 4 dB.
- the router has a polarisation sensitivity of between 0.3dB and 0.8dB, depending on wavelength and path through the router.
- the range of wavelengths routed from any input 1 to 22 to any output 1 to 22 is given in the following matrix (Table 2) .
- Table 2 The design minimises wavelength errors between the wavelengths of the ITU frequency standard and the channel centre wavelengths.
- the maximum residual error is 0.04 nm over the wavelength range 1 538-1 560 nm when the multiplexer is heated to 28.1 °C.
- the router has half connectors attached to all 44 fibre tails, and is housed within a thermally controlled environment, in order to raise its temperature, and thereby minimise the wavelength errors.
- each switch node is shared between a number r of routers and each router carries a fraction 1 /r of a respective switch node's traffic.
- connections for standby paths for router protection are made to and from working fibres in a region which is closer to the hub than to the switch nodes, but which is far enough away from respective working routers to be unaffected by localised causes of failure (such as fire or other physical damage) .
- the connections to the working fibres may be by way of switches or by splitting/coupling.
- Optical fibre paths extend from the working fibres to standby routers a distance xR ⁇ ⁇ R, where R is the distance of the working fibre path from a switch node to a working routers.
- R is the distance of the working fibre path from a switch node to a working routers.
- the standby routers themselves switch in fibres from failed routers.
- the increase in fibre lengths for implementing the router protection strategy is given by a factor of 1 + xn (where n is the number of standby routers).
- a bus topology is used. As shown in Figure 9, the optical fibre bus runs across the working fibre paths at a distance from the routers such that the maximum path length via the bus to a standby router is xR.
- each standby router requires a number 2N of rx 1 optical switches Each rx 1 switch enables a fibre connected to any of r router locations to be switched to one of the n standby router locations In use, when a working router fails, all the fibres from all the switch nodes connected to that working router can then be switched to one of the n standby router locations.
- connection to the working fibre being by way of fixed splitters/couplers
- switching is employed using an r x (r + n) optical switch at the connection to each working fibre (where r is the number of working routers and n is the number of standby routers)
- Failure at the r x (r + n) switch site may be treated as a path failure, and is then encompassed by the path protection scheme outlined above, using a standby spoke
- the increase in fibre lengths for the router protection scheme is given by a factor 1 + xn/r
- the router In operation, using either of the router protection strategies described above, the router carries out self-diagnostic tests These include monitoring power levels and the presence of individual wavelength channels on each of the incoming and outgoing optical fibres When, as a result of these tests, a router failure is detected, then a message is sent to all other routers, both working and standby Supervisory signals are sent between routers and/or between routers and one or more centralised locations, so that all routers and/or control logic at the centralised locat ⁇ on(s) are aware of the status of all routers In one implementation, supervisory signals are sent over a separate data communication network (DCN) Alternatively the supervisory signals may be sent over the fibre infrastructure described above Signals are sent sufficiently frequently from each router, or alternatively continuously, so that the disappearance of a supervisory signal is used as a fast indication of router failure, for example within 0.5 msec When a router fails, a supervisory signal is turned off This may be done under the control of the router in response to the detection of a failure, or may be direct
- a node may interpret router failure as a path failure (unless path protection is only implemented if all fibres arriving at a node from all routers along one path fail simultaneously). Before a path protection controller can begin the setting up of a protection path it checks with the router protection controller that router failure is not the cause.
- the wavelength routers in the above examples use an NxN wavelength multiplexer, some of whose ports are used as "dummy" ports, containing one or more wavelength converters, which enables the router to become fully non- blocking, when the wavelength converters are used in conjunction with tunable transmitters and receivers at the node locations
- the three sets of tunable elements provide a 3-stage switching structure
- his use of "dummy" ports requires additional ports and wavelength channels than are strictly necessary
- An alternative structure is shown in Figure 1 1 .
- each NxN router in the above examples may be replaced by a full- scale optical cross-connect
- Figure 10 shows an implementation using SDH (synchronous digital hierarchy) technology
- the previous examples use working and standby wavelength routers, whose task is to route individual wavelength channels from a given node to any other node in the network, their place is taken in this example by working and standby SDH cross-connects, whose task is now to route SDH systems from a given node to any other
- the granularity of the routed SDH systems is optional, depending on the traffic matrix between the nodes.
- the network may carry individual 2 Mbit/s channels, or STM-1 channels, STM-4 channels, STM-1 6 channels etc.
- the traffic matrix is uniform, then ideally the granularity of the channels within a fibre matches the number of nodes to be connected to de N-1 ) .
- N 1 7 nodes is ideal.
- wavelength routemg is not used in this SDH example, it is still possible for WDM to be employed just for transmission capacity purposes within the fibres between the ATM switch nodes and the SDH cross-connects.
- each fibre could support 1 6 STM-1 6 systems, or even 1 6 STM-64 systems using 1 6-channel WDM within the fibre.
- the wavelength channels are converted to and from electrical signals.
- any residual channels from a node that are insufficient to fill a complete fibre from the node to the hub are transmitted around the perimeter of the network to an adjacent or further node, until they can be multiplexed with other nodes' channels to fill a fibre to the hub.
- the perimeter is also used for path protection purposes.
- the protection channels could still be switched around the perimeter by means of optical switches.
- the ATM switches themselves may fulfill this purpose.
- additional SDH cross-connects or add-drop multiplexers (ADMs) are connected to the ATM switches for this purpose.
- the residual channels are switched by either the ATM switches or by associated SDH cross-connects or ADMs.
- the multiple-star network structure employing SDH cross-connects requires less fibre than an SDH ring. Port-port connections in one or more of the hub SDH cross-connects are time-shared in order to provide the exact node-node capacity, or close to that capacity.
- one of the STM-1 channels instead of being dedicated between one input port and one output port of a cross-connect, will have smaller units of capacity, eg 8 Mbit/s (4 off 2Mbit/s), switched to multiple output ports by the cross-connect. Similarly multiple input ports would be multiplexed into one output port for the return path.
- another implementation may use a conventional optical cross-connect as the router in combination with fixed-wavelength WDM at the nodes.
- FIG. 1 shows an alternative router structure. This splits the router into two NxN wavelength multiplexers. Wavelength converters are positioned between the two multiplexers. The wavelength converters may be all-optical devices, or may comprise tuneable receiver/transmitter pairs. With this structure, there is no need for additional dummy ports. This reduces the number of wavelength channels required, and eases device fabrication.
- two fibres, each capable of carrying 1 6 channels extend from a node to working router number 1 . Since the node can take 22 channels, 10 channels are left.
- a tap from one of the two fibres, in a region which is closer to the router than to the node, is connected to inputs of another working router, in this case the adjacent router no. 2.
- Figure 1 3A shows the use of a wavelength multiplexer at the tap adjacent to router 1 to couple 10 wavelength channels, that is channels 7 to 1 6, to working router 2.
- Figure 1 3B shows the equivalent arrangement at the tap adjacent to working router 2.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU56728/98A AU5672898A (en) | 1997-01-27 | 1998-01-20 | Communications system with star topology |
EP98900923A EP1013012A1 (en) | 1997-01-27 | 1998-01-20 | Communications system with star topology |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9701591A GB9701591D0 (en) | 1997-01-27 | 1997-01-27 | Communications system |
GB9701591.1 | 1997-01-27 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1998033287A1 true WO1998033287A1 (en) | 1998-07-30 |
Family
ID=10806618
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1998/000169 WO1998033287A1 (en) | 1997-01-27 | 1998-01-20 | Communications system with star topology |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1013012A1 (en) |
AU (1) | AU5672898A (en) |
GB (1) | GB9701591D0 (en) |
WO (1) | WO1998033287A1 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1999037050A1 (en) * | 1998-01-03 | 1999-07-22 | British Telecommunications Public Limited Company | Communications system with star/ring topology |
WO2000064078A1 (en) * | 1999-04-15 | 2000-10-26 | Nokia Networks Oy | Method and apparatus for implementing an optical cross-connection |
GB2396086A (en) * | 2002-12-03 | 2004-06-09 | Abb Offshore Systems Ltd | Communication system for a hydrocarbon production well |
US6914880B1 (en) | 1999-04-22 | 2005-07-05 | Telecommunications Research Laboratories | Protection of routers in a telecommunications network |
EP1560457A1 (en) * | 2004-01-30 | 2005-08-03 | Technische Universität Berlin | A hybrid optical network and a method of routing data packets in a hybrid optical network |
WO2013164044A1 (en) | 2012-05-04 | 2013-11-07 | Deutsche Telekom Ag | Method and device for constructing and operating a modular, highly scalable, very simple, cost-efficient and sustainable transparent optically-routed network for network capacities of greater than 1 petabit(s) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS58177041A (en) * | 1982-04-10 | 1983-10-17 | Nec Corp | Optical transmission system |
EP0215711A2 (en) * | 1985-09-10 | 1987-03-25 | Alcatel N.V. | Voice and data distribution system with fiber optic multinode star network |
US5043975A (en) * | 1989-06-29 | 1991-08-27 | Digital Equipment Corporation | High bandwidth network based on wavelength division multiplexing |
-
1997
- 1997-01-27 GB GB9701591A patent/GB9701591D0/en active Pending
-
1998
- 1998-01-20 AU AU56728/98A patent/AU5672898A/en not_active Abandoned
- 1998-01-20 WO PCT/GB1998/000169 patent/WO1998033287A1/en not_active Application Discontinuation
- 1998-01-20 EP EP98900923A patent/EP1013012A1/en not_active Withdrawn
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS58177041A (en) * | 1982-04-10 | 1983-10-17 | Nec Corp | Optical transmission system |
EP0215711A2 (en) * | 1985-09-10 | 1987-03-25 | Alcatel N.V. | Voice and data distribution system with fiber optic multinode star network |
US5043975A (en) * | 1989-06-29 | 1991-08-27 | Digital Equipment Corporation | High bandwidth network based on wavelength division multiplexing |
Non-Patent Citations (4)
Title |
---|
HILL G R: "A WAVELENGTH ROUTING APPROACH TO OPTICAL COMMUNICATIONS NETWORKS", NETWORKS: EVOLUTION OR REVOLUTION?, NEW ORLEANS, MAR. 27 - 31, 1988, no. CONF. 7, 27 March 1988 (1988-03-27), INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, pages 354 - 361, XP000044787 * |
OBARA H ET AL: "SCALABLE TWO-STAGE WDM CROSSCONNECT ARCHITECTURE", ELECTRONICS LETTERS, vol. 32, no. 1, 4 January 1996 (1996-01-04), pages 57/58, XP000553379 * |
PATENT ABSTRACTS OF JAPAN vol. 008, no. 013 (E - 222) 20 January 1984 (1984-01-20) * |
SHARONY J ET AL: "THE WAVELENGTH DILATION CONCEPT IMPLEMENTATION AND SYSTEM CONSIDERATIONS", DISCOVERING A NEW WORLD OF COMMUNICATIONS, CHICAGO, JUNE 14 - 18, 1992, vol. VOL. 2, no. -, 14 June 1992 (1992-06-14), INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, pages 829 - 836, XP000326793 * |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1999037050A1 (en) * | 1998-01-03 | 1999-07-22 | British Telecommunications Public Limited Company | Communications system with star/ring topology |
WO2000064078A1 (en) * | 1999-04-15 | 2000-10-26 | Nokia Networks Oy | Method and apparatus for implementing an optical cross-connection |
US6914880B1 (en) | 1999-04-22 | 2005-07-05 | Telecommunications Research Laboratories | Protection of routers in a telecommunications network |
GB2396086A (en) * | 2002-12-03 | 2004-06-09 | Abb Offshore Systems Ltd | Communication system for a hydrocarbon production well |
GB2396086B (en) * | 2002-12-03 | 2005-11-23 | Abb Offshore Systems Ltd | A system for use in controlling a hydrocarbon production well |
EP1560457A1 (en) * | 2004-01-30 | 2005-08-03 | Technische Universität Berlin | A hybrid optical network and a method of routing data packets in a hybrid optical network |
WO2005076658A1 (en) * | 2004-01-30 | 2005-08-18 | Technische Universität Berlin | A hybrid optical network and a method of routing data packets in a hybrid optical network |
WO2013164044A1 (en) | 2012-05-04 | 2013-11-07 | Deutsche Telekom Ag | Method and device for constructing and operating a modular, highly scalable, very simple, cost-efficient and sustainable transparent optically-routed network for network capacities of greater than 1 petabit(s) |
US9882643B2 (en) | 2012-05-04 | 2018-01-30 | Deutsche Telekom Ag | Method and device for setting up and operating a modular, highly scalable, very simple, cost-efficient and enduring transparent optically routed network for network capacities of greater than 1 Petabit/s |
Also Published As
Publication number | Publication date |
---|---|
AU5672898A (en) | 1998-08-18 |
EP1013012A1 (en) | 2000-06-28 |
GB9701591D0 (en) | 1997-03-19 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6226111B1 (en) | Inter-ring cross-connect for survivable multi-wavelength optical communication networks | |
US6542268B1 (en) | Optical channel cross connect for telecommunication systems in wdm technology (wavelength division multiplexing) having a double spatial switching structure of optical flows strictly not blocking and interposed functional units operating on single channels | |
Elrefaie | Multiwavelength survivable ring network architectures | |
JP3008260B2 (en) | Ring network communication structure of optical transmission line and reconfigurable node for that structure | |
EP1360790B1 (en) | Optical transmission systems including optical protection systems, apparatuses, and methods | |
US6587235B1 (en) | Method and apparatus for capacity-efficient restoration in an optical communication system | |
EP0820666B1 (en) | Optical multichannel system | |
EP2494726B1 (en) | Improvements in optical communications networks | |
JP4219386B2 (en) | Optical network, optical gateway node and method | |
US5982517A (en) | Method and system for service restoration in optical fiber communication networks | |
EP1043859B1 (en) | Optical add/drop multiplexer node device | |
EP2385642A1 (en) | A method for providing protection in an optical communication network against connection failures | |
WO2002033857A1 (en) | Wdm optical communication system with channels supporting multiple data formats | |
US6968130B1 (en) | System and method for fully utilizing available optical transmission spectrum in optical networks | |
Wagner et al. | Multiwavelength ring networks for switch consolidation and interconnection | |
EP1050130B1 (en) | Communications system with star / ring topology | |
EP1013012A1 (en) | Communications system with star topology | |
Chidgey | Multi-wavelength transport networks | |
KR20050046703A (en) | Awg based wdm-pon architecture for the protection of multiple point failures | |
JP2000115133A (en) | Optical path cross connection device and optical network | |
Wuttisittikulkij et al. | Multiwavelength self-healing ring transparent networks | |
Song et al. | Hardware-accelerated protection in Long-Reach PON | |
Sue | Opn01-1: 1: n protection scheme for awg-based wdm pons | |
KR20060112862A (en) | Protection architectures for awg based wdm-pon | |
Peng et al. | Reliable architecture for high-capacity fiber-radio systems |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
WWE | Wipo information: entry into national phase |
Ref document number: 09043288 Country of ref document: US |
|
AK | Designated states |
Kind code of ref document: A1 Designated state(s): AL AM AT AU AZ BA BB BG BR BY CA CH CN CU CZ DE DK EE ES FI GB GE GH GM GW HU ID IL IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT UA UG US UZ VN YU ZW |
|
AL | Designated countries for regional patents |
Kind code of ref document: A1 Designated state(s): GH GM KE LS MW SD SZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN ML MR NE SN TD TG |
|
DFPE | Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101) | ||
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
WWE | Wipo information: entry into national phase |
Ref document number: 1998900923 Country of ref document: EP |
|
REG | Reference to national code |
Ref country code: DE Ref legal event code: 8642 |
|
NENP | Non-entry into the national phase |
Ref country code: JP Ref document number: 1998531711 Format of ref document f/p: F |
|
WWP | Wipo information: published in national office |
Ref document number: 1998900923 Country of ref document: EP |
|
WWW | Wipo information: withdrawn in national office |
Ref document number: 1998900923 Country of ref document: EP |