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WO1997031436A1 - Reseau optique a acces multiple par repartition dans le temps a impulsions obscures - Google Patents

Reseau optique a acces multiple par repartition dans le temps a impulsions obscures Download PDF

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Publication number
WO1997031436A1
WO1997031436A1 PCT/GB1997/000520 GB9700520W WO9731436A1 WO 1997031436 A1 WO1997031436 A1 WO 1997031436A1 GB 9700520 W GB9700520 W GB 9700520W WO 9731436 A1 WO9731436 A1 WO 9731436A1
Authority
WO
WIPO (PCT)
Prior art keywords
optical
signal
clock signal
node
transmission medium
Prior art date
Application number
PCT/GB1997/000520
Other languages
English (en)
Inventor
Kevin Smith
Julian Kazimierz Lucek
Danny Robert Pitcher
Terence Widdowson
David Graham Moodie
Andrew David Ellis
Original Assignee
British Telecommunications Public Limited Company
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from GBGB9604020.9A external-priority patent/GB9604020D0/en
Priority claimed from GBGB9613345.9A external-priority patent/GB9613345D0/en
Priority claimed from GBGB9620502.6A external-priority patent/GB9620502D0/en
Priority claimed from EP96307207A external-priority patent/EP0835002A1/fr
Priority to US09/043,409 priority Critical patent/US6396604B1/en
Priority to AU18882/97A priority patent/AU732674B2/en
Priority to EP97905265A priority patent/EP0883938A1/fr
Priority to NZ331214A priority patent/NZ331214A/en
Application filed by British Telecommunications Public Limited Company filed Critical British Telecommunications Public Limited Company
Priority to JP52992097A priority patent/JP2002516043A/ja
Priority to CA002245716A priority patent/CA2245716A1/fr
Publication of WO1997031436A1 publication Critical patent/WO1997031436A1/fr
Priority to NO983894A priority patent/NO983894L/no

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/0075—Arrangements for synchronising receiver with transmitter with photonic or optical means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/27—Arrangements for networking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H04B10/505—Laser transmitters using external modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H04B10/505—Laser transmitters using external modulation
    • H04B10/5051—Laser transmitters using external modulation using a series, i.e. cascade, combination of modulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/508—Pulse generation, e.g. generation of solitons
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/08—Time-division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter
    • H04L7/0016—Arrangements for synchronising receiver with transmitter correction of synchronization errors
    • H04L7/0033—Correction by delay
    • H04L7/0037—Delay of clock signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/08—Time-division multiplex systems
    • H04J14/083—Add and drop multiplexing

Definitions

  • the present invention relates to an optical network for carrying TDMA (Time Division Multiple Access) signals and to transmitters and receivers for use in nodes of such a network.
  • TDMA Time Division Multiple Access
  • a network embodying the present invention might be used, for example, as a local area network (LAN) for interconnecting computer systems
  • LAN local area network
  • the increasing power of computer systems in terms of processor speeds and storage capacity has made it possible for conventional personal computers to handle multimedia applications involving real time video and animation and computer graphics.
  • the high bandwidth data associated with such applications place heavy demands on the network and the performance of conventional LANs has failed to keep pace.
  • An optical network using synchronous TDMA potentially offers a far higher bandwidth, and so might be used as a high speed LAN to replace a conventional LAN.
  • some electronic circuits have been required for such functions as channel selection. It has been recognised that such electronic components of the network infrastructure constitute a bottleneck restricting the performance of the network.
  • a High Speed Broadcast and Select TDMA network Using All-Optical Demultiplexing L P Barry et al, ECOC '95 pp 437-440, describes an experimental OTDM network.
  • an optical clock signal is detected and a variable delay applied in the electrical domain to the detected clock signal to select a particular TDMA channel.
  • the signal is taken back into the optical domain by driving a local optical source, a DFB laser, which produces an optical signal for use in a subsequent all-optical switching stage.
  • an optical network comprising- a) an optical transmission medium; and b) a plurality of nodes connected to the optical transmission medium, each of the plurality of node including a respective dark pulse generator which is coupled in-line with the optical transmission medium and in series with the others of the dark pulse generators and which is arranged to generate dark pulses in an optical signal carried on the transmission medium.
  • a "dark pulse” is a temporal gap, or region of reduced intensity radiation, in an essentially continuous burst of optical radiation, or light beam.
  • each node further comprises a variable delay stage which is arranged to apply a variable delay to a network clock signal in the electrical domain and which is connected at its output to the dark pulse generator.
  • the inventors have found it to be particularly advantageous to use in combination dark pulse generation and channel selection in the electrical domain. This further simplifies node structures, whilst enabling effective operation at high bit rates, for example at 40 Gbit/s.
  • each node further comprises a clock receiver for receiving a network clock signal carried on the optical transmission medium, the clock receiver including a photoelectric detector for converting the clock signal to the electrical domain.
  • the electro-optic modulator is an electro-absorption modulator
  • the present inventors have found that significant advantages can be achieved by combining channel selection in the electrical domain with the use of an electro-optic switch with a fast non-linearity to read the selected channel.
  • relatively high switching rates can be achieved without the power losses typically associated with all-optical channel selection.
  • the fast response time of such a device makes possible a switching window as short as a few picoseconds.
  • the receiver as a whole is therefore capable of operating at bit rates of 40Gb ⁇ t/s or higher.
  • the receiver includes means for separating the clock signal in the optical domain from the received TDMA datastream.
  • the said means for separating comprise a polarising beam splitter, in use the clock signal being marked by a different polarisation state to the TDMA datastream.
  • a first output of the means for separating is connected to the optical input of the electro-optic modulator, in use TDMA data passing from the first output to the modulator, and a second output of the means for separating is connected to the detector, in use optical clock signals passing from the second output to the detector.
  • an impulse generator is connected between the output of the variable delay stage and the control input of the electro-optic modulator.
  • the electro-optic modulator may require a drive signal having somewhat shorter pulses than those output by the delay stage.
  • some form of pulse shaping may be used, and in particular the output of the delay stage may be applied to an electrical impulse generator.
  • This may be a device using step recovery diodes to generate short electrical pulses from a sine wave.
  • variable delay stage comprises a plurality of logic gates, means connecting a first input of each gate to an input path for the clock signal, control means connected to a second input of each gate, and means connecting outputs of the gates in common to an output path for the delayed clock signal, the said means connecting inputs and outputs of the gates to respective input and output paths being arranged to provide paths of different respective lengths via different gates, in use the control means applying control signals to the gates to select a path and a corresponding delay for the clock signal.
  • This preferred feature of the present invention uses an array of logic gates to provide an electronic channel selector suitable for an integrated construction, and capable of quick reconfiguration.
  • This channel selector is not limited in applicability to receivers in accordance with the first aspect of the present invention, but may be used with other receiver designs, or in node transmitters In particular, it may be combined with a local optical source in a receiver in which an all-optical switch was used in place of the electro-optic modulator of the first aspect of the invention.
  • At least one of the said means connecting inputs and outputs comprises a microst ⁇ p delay line
  • the means connecting inputs and outputs comprise a pair of microst ⁇ p delay lines and the gates are connected between the pair of microst ⁇ p delay lines.
  • adjacent connections to the gates on the microst ⁇ p delay line on the input side of the gates are separated by a path length corresponding to t/2 and adjacent connections on the microst ⁇ p delay line on the output side of the gates are separated by a path length corresponding to t/2, in use the gates being controlled to vary the delay by multiples of t, where t corresponds to the channel spacing in the time domain of the TDMA signal.
  • the optical transmission medium is an optical bus, and more preferably hs an optical bus topology.
  • the use of dark pulse generation is found to be particularly well-adapted to a network using a bus-topology This allows the dark pulse generators in the different nodes to be effectively coupled in series so as to build up an OTDM multiplex.
  • the bus topology eliminates many of the timing problems associated with other topologies, such as star networks
  • a method of operating an optical network including a plurality of nodes connected to an optical transmission medium, the method comprising a) at one of the plurality of nodes, imposing dark pulses representing a data stream on an optical signal which is carried on the optical transmission medium; and b) at a subsequent node, receiving the optical signal including the dark pulses imposed in step (a) and imposing dark pulses on the optical signal in a different respective time slot, thereby creating an OTDM (optical time division multiplexed) signal.
  • the present invention also encompasses an optical network incorporating a receiver in accordance with the preceding aspects and also LANs and other computer networks formed using such a network.
  • Figure 1 is a schematic of an optical network
  • Figure 2 is a diagram showing the structure of one of the nodes of Figure
  • Figure 3 is a schematic of a transmitter for use in the network of Figure 1 ;
  • Figure 4 is a schematic of a receiver for use in the network of Figure 1 ;
  • Figure 5 is a circuit diagram for an electrical channel selector
  • Figure 6 is a diagram illustrating the use of the electrical channel selector with a local optical source
  • Figure 7 is a detailed schematic of a receiver based on the topology of
  • Figure 8 is a schematic of a pulse source
  • Figure 9 illustrates a dark pulse generator incorporating one EAM
  • Figure 10 is a graph representing a typical operational characteristic of an EAM
  • Figure 1 1 is a representation of an optical output signal provided by the system in Figure 9;
  • Figure 1 2 illustrates a system incorporating three EAMs
  • Figure 1 3 is an eye diagram of an optical output signal provided by the system in Figure 1 2;
  • Figure 14 is a schematic of an optical fibre LAN incorporating dark pulse generators.
  • FIGs 1 5a and 15b show fibre waveguides for use in the LAN of Figure 1 4.
  • An optical network comprises a number of nodes N 1 , N2, N3 connected to an optical fibre bus 1 .
  • the network is a local area network (LAN) and a number of personal computers PC1 , PC2, PC3 are connected via the optical fibre bus to each other and to a network server 2.
  • LAN local area network
  • PC1 , PC2, PC3 are connected via the optical fibre bus to each other and to a network server 2.
  • the network uses a structure termed by the inventors a re-entrant bus topology.
  • each node includes a transmitter 21 coupled to the bus 1 at two points and a receiver 22 coupled to the fibre bus 1 at a point downstream from the transmitter The transmitter 21 and receiver 22 are coupled to the respective personal computer by an electronic interface 23.
  • the network operates using a synchronous TDMA (time division multiple access) protocol.
  • a clock stream is distributed to all users of the network thereby ensuring that each node is synchronised.
  • a clock pulse marks the start of each frame.
  • the frame is precisely divided into time-slots - for example slots of 10ps duration for a 1 00Gb ⁇ t/s line rate.
  • each node has a tuneable transmitter and tuneable receiver and can thereby transmit and receive in any of the time- slots.
  • the granularity of the network may be chosen to be relatively high so that each user has access to a relatively low speed (say 1 55Mb ⁇ t/s) channel from a fibre optic pipe which itself carries rates in excess of 100Gb ⁇ t/s.
  • the electronic speeds within each node are at most 2.5Gb ⁇ t/s in this example
  • the clock source is typically located at the network controller 3 associated with the server 2.
  • the clock produces a regular stream of picosecond duration optical pulses at a low repetition rate, say 1 55 or 250MHz, relative to the peak line rate of the optical pipe ( 100Gb ⁇ t/s) .
  • Such a source may be provided by a mode-locked laser or a gain-switched laser with external pulse compression.
  • a pulse duration of around 2ps is required whereas for a 40Gb ⁇ t/s system around 5-7ps suffices.
  • a pulse source suitable for operation at 100Gb ⁇ t/s or higher is disclosed and claimed in the present applicant's co-pending European Patent Application filed 1 6th February 1 996 and entitled "Optical Pulse Source" (applicant's ref. A25146). The disclosures of that earlier application are incorporated herein by reference.
  • This pulse source may comprise a ⁇ dge- waveguide gain-switched distributed feedback semiconductor laser diode (DFB- SLD) having its output gated by an electro-absorption modulator. Continuous wave (cw) light is injected into the optical cavity of the DFB-SLD. A synchronised RF drive is applied to the DFB-SLD and to the EAM.
  • DFB- SLD distributed feedback semiconductor laser diode
  • cw Continuous wave
  • Figure 3 shows the transmitter in one of the nodes
  • a fraction of the distributed clock stream is split-off and then encoded via an electro- optic modulator.
  • This may be, for example, a lithium niobate modulator such as that available commercially from United Technologies, model no. APE MZM- 5-3- T- 1 -1 -B/C, or an electro-absorption modulator (EAM)
  • EAM electro-absorption modulator
  • a suitable EAM is described in the paper by D.G Moodie et al published at pp 1 370-1 371 Electron Letts., 3 August 1 995, Vol 31 , no. 1 6.
  • the variable time delay in the transmitter then places the modulated pulse stream into the correct time slot for onward transmission.
  • a pola ⁇ ser P eliminates the possibility of data channels breaking through and being modulated in the electro-optic modulator (EOmod).
  • the pola ⁇ ser need not be a separate device but might be integrated with the EO modulator.
  • the United Technologies EAM referred to above is inherently polarisation- selective in operation .
  • the delay line provides the required delay and data pulses are inserted into the appropriate time-slot with a polarisation orthogonal to the clock stream.
  • This polarisation rotation may be done via a simple polarisation rotator such as a retardation plate or, where polarisation maintaining fibre is used to implement the circuit, then rotation may be achieved by physically rotating the waveguide before reinserting it into the fibre optic pipe.
  • the clock and the data are separated.
  • a polarising beam splitter PBS
  • PBS polarising beam splitter
  • the clock and the data pulses are then forced to suffer a relative (programmable) optical delay using a variable time delay device This means that the clock pulse can be temporally overlapped with any data pulse slot and therefore used to demultiplex or read any channel.
  • the channel is demultiplexed, it is converted back into the electrical domain using a receiver operating at up to 2.5 Gbit/s, the allocated bandwidth per user.
  • FIG 4 shows in detail the structure of the receiver and in particular shows how an electrical channel selector (ECS) is used to provide a signal which, after suitable amplification and shaping drives an electro-absorption modulator (EAM).
  • the electrical channel selector (ECS) is shown in Figure 5.
  • the optical LAN clock is first detected using a detector 52 which might be, for example, a PIN photodiode. After amplification, the signal is filtered to generate a clean electrical sine wave. The signal is then input to a delay stages 53 comprising a series of electrical AND gates LG arranged in a linear array.
  • the array is implemented as a single low cost chip available commercially as NEL NLB6202.
  • the AND gates control access to the microst ⁇ p delay lines.
  • the delay lines are accurately stepped in delays equal to the channel separation of the LAN. For a system operating at 40Gb ⁇ t/s, the channel delay t equals 25ps.
  • the AND gates are controlled via an input from a demultiplexer 54
  • the demultiplexer is an NL4705 device manufactured by NEL.
  • the demultiplexer converts an incoming serial delay select word generated by the PC connected to the node into an appropriate gating signal for the AND gate array and thereby selects the appropriate delay.
  • the electrical channel selector produces at its output a stepped sine wave. This may then be amplified and suitably shaped in order to generate the appropriate drive signal required for the next stage.
  • the next stage may be, for example, an EAM, or a laser diode. If the pulses output by the ECS require shortening to drive the next component, then an electrical impulse generator may be used.
  • a suitable coaxial step recovery diode comb generator is available commercially as ELISRA series MW1 5900. Given that electronic clock recovery can be carried out with sub-picosecond temporal jitter and microst ⁇ p delay lines can be controlled to picosecond accuracy, it is potentially possible to use such an electrical channel selector at rates as high as 100Gb ⁇ t/s.
  • the ECS might alternatively be used in combination with a local optical source.
  • the ECS may be used either in the transmitter for programmable channel insertion ( Figure 6) , or in the receiver for channel dropping ( Figure 7) .
  • the output of the local picosecond pulse laser is combined with the data in an optical AND gate.
  • Advances in picosecond pulse lasers in recent years are such that it is possible to generate stable picosecond duration optical pulses using semiconductor based active media.
  • One example of such a laser is a gain- switched DFB laser followed by chirp compensation as described in our above-cited copendmg application.
  • the wavelength of the source depends on the design of the optical AND gate, but is not at all restricted to be the same as the data wavelength
  • the optical AND gate may be an SLA - NOLM or may be an integrated semiconductor-based device
  • the systems so far described have used what may be termed "bright pulses" to carry information.
  • dark pulses may be used instead A convenient system for generating dark pulses will now be described. Initially the description covers the case of a system incorporating only one EAM. Typically, however, more than one EAM would be utilised, as described in more detail below.
  • a 1 555nm DFB laser source 1 1 0 is coupled into an EAM 1 20 with a power level of -2dBm.
  • the EAM has a maximum extinction ratio of 20dB and a mean absorption characteristic of 2.5dB/V.
  • a 10 GHz sinewave drive 142 is synchronised with and passively added to a 10Gb ⁇ t/s data sequence from a data source 144 via a power splitter 140 (used in reverse to combine the two signals).
  • a suitable power splitter is the Wiltron K240B, available from Anritsu Wiltron.
  • Both the sinewave and data sequence signal levels have a 2.5V peak-to-peak amplitude.
  • the resulting signal comprises a sinewave with an offset voltage determined by the data signal, with the relative amplitudes arranged such that the maximum value of the cycle for a data 0 is below the minimum level for a data 1 .
  • An EAM suitable for use in the system is the one described in, for example, "Generation of 6 3 ps optical pulses at a 10 GHz repetition rate using a packaged EAM and dispersion compensating fibre” , Electronics Letters, Volume 30, pp 1 700-1 701 , which is incorporated herein by reference
  • the absorption characteristic of this EAM is reproduced in Figure 10.
  • Figure 1 0 it can be seen that the EAM has an operating region of low extinction at positive or low negative reverse biases, an operating region of high extinction at high reverse biases, and an exponentially varying operating region in between It is the exponentially varying operating region of the EAM which supports the generation of soliton-like dark pulses.
  • the dark pulses generated should resemble inverted SECH 2 pulses (that is to say, inverted so tons) having the form-
  • Figure 1 2 shows a system according to the present invention implementing three EAMs.
  • three EAMs 400, 41 0 and 420 are optically cascaded, or are arranged to be in optically coupled alignment, with an optical light source 1 00, comprising a 1 555nm DFB laser.
  • the laser light is coupled onto the first EAM 400, using a standard telecommunications optical fibre 105, the light having a power level of -2dBm.
  • optical amplifiers 405, 41 5 and 425, for example EDFAs follow each EAM to compensate for any losses incurred in the EAMs.
  • the amplifiers are only incorporated if necessary to compensate for optical loss incurred by the EAMs.
  • each EAM is driven by an electrical signal comprising a sinewave component and a data component aligned in data channel slots A, B or C.
  • electrical timing circuitry 450 is required to ensure that the data signals A, B and C are aligned correctly with the sinewave and are aligned also in the correct slot positions of the required OTDM signal which is output downstream of the third amplifier 425.
  • the light source can be separate from the modulator, the light from the light source being coupled into the modulator via, for example, an optical fibre as described above.
  • the light source and the EAMs are fabricated as an integrated device on a common semiconductor substrate Apart from convenience, this arrangement has the advantage that coupling loss between each modulator and between the light source and the first modulator is reduced. Also, amplification, if necessary, could be provided by integrating SLAs (semiconductor laser amplifiers) between one or more EAMs
  • SLAs semiconductor laser amplifiers
  • any form of optical, acousto-optic or electro-optic modulator having the necessary transmission and extinction or switching properties to provide dark pulses would be suitable for implementing the present invention.
  • the electrical bias scheme described above for driving the EAM is particularly advantageous for two reasons. Firstly, only one electrical signal is required to bias each EAM and secondly the electrical signal does not require any electrical processing. Electrical processing would be required if using the method described in "Generation of 2.5Gb ⁇ t/s soliton data stream with an integrated laser modulator transmitter", Electronics Letters, Volume 30, pp 1 880- 1 881 .
  • EAMs suffer some optical loss even when operating in their low optical loss regions.
  • the amount of optical loss of an EAM is partly determined by the length of the optical modulator section through which light from a light source travels.
  • modulator schemes comprising two modulators or multiple modulator sections, which firstly generate an optical pulse stream using an electrical sinewave drive signal, and secondly modulate data onto the pulse stream using an electrical data signal
  • both modulators, or both modulator sections incur an optical insertion loss.
  • the proposed system only implements one modulator (section) per data channel, the system intrinsically incurs a lower insertion loss overhead, regardless of the type of modulator used, than other schemes incorporating more than one modulator, or modulator section, to generate one data channel.
  • the optical radiation is in the form of a substantially continuous burst.
  • the duration of the burst depends on the application
  • the optical source might remain on all the time.
  • the source might be switched on only when transmission of data, or part thereof (for a packet switched network for example), is required. Therefore, 'substantially continuous' might be interpreted as continuous during data transmission.
  • the cw light input into the first EAM can be substituted for an optical clock, for example a sinewave or pulse stream.
  • each EAM can be used to modulate one time slot of the optical clock. That is to say, each EAM is arranged either to transmit, or prevent transmission, of light (the peaks or bright pulse portions of the clock signal) depending on the data-encoding requirements of its designated data channel. For example, for a 1 00Gb ⁇ t/s optical clock pulse stream, ten EAMs may be cascaded to encode ten 1 0Gb ⁇ t/s channels. Also, one or more EAMs operating according to this arrangement may be used as data-insert devices for one or more channels in an OTDM system. The skilled person would easily be able to implement data modulation or an insert function by applying the theory disclosed by the present description.
  • FIG. 14 shows dark pulse generators incorporated in a network using the re-entrant bus topology described previously. It differs from the networks considered previously, in that the time-slot into which data is added at a node transmitter can be chosen in the electrical domain. Each node transmitter has a 1
  • the network clock may be distributed along the optical fibre bus using a different polarisation state to distinguish it from the optical data on the bus. It is preferred however that the bus should comprise two co-located optical fibre waveguides, with one of the two waveguides
  • the two waveguides may be provided by twin cores 1 51 , 1 52 within a single optical fibre 1 53.
  • two or more optical fibres 51 a-51 d may be co-located within a single sheath
  • the optical signal for modulation by the EAM of the dark pulse generator is then transmitted down one of the waveguides while the network clock signal is transmitted down another of the waveguides.
  • the network clock does not need necessarily to be a short optical pulse, since in this embodiment the clock is not
  • a relatively broad optical pulse. or modulation of a CW beam may be used to generate the clock.
  • the network clock is converted to the electrical domain and a variable delay applied in order to generate a control signal for the EAM in the appropriate respective time slot
  • This signal is modulated with RZ data received, for example, from a PC data interface

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Computing Systems (AREA)
  • Optical Communication System (AREA)
  • Time-Division Multiplex Systems (AREA)

Abstract

L'invention concerne un réseau optique. Ce réseau comprend un certain nombre de noeuds couplés à un support de transmission optique, tel qu'un bus de fibres optiques. Chacun des noeuds comprend un générateur d'impulsions obscures dans des tranches de temps différentes sur le support de transmission, ce qui forme un signal multiplexé par répartition dans le temps à impulsions obscures. Ce réseau peut présenter une topologie de bus ré-entrant.
PCT/GB1997/000520 1996-02-26 1997-02-25 Reseau optique a acces multiple par repartition dans le temps a impulsions obscures WO1997031436A1 (fr)

Priority Applications (7)

Application Number Priority Date Filing Date Title
CA002245716A CA2245716A1 (fr) 1996-02-26 1997-02-25 Reseau optique a acces multiple par repartition dans le temps a impulsions obscures
JP52992097A JP2002516043A (ja) 1996-02-26 1997-02-25 ダークパルスｔｄｍａ光網
US09/043,409 US6396604B1 (en) 1996-02-26 1997-02-25 Dark pulse TDMA optical network
NZ331214A NZ331214A (en) 1996-02-26 1997-02-25 Dark pulse tdma optical network
AU18882/97A AU732674B2 (en) 1996-02-26 1997-02-25 Dark pulse TDMA optical network
EP97905265A EP0883938A1 (fr) 1996-02-26 1997-02-25 Reseau optique a acces multiple par repartition dans le temps a impulsions obscures
NO983894A NO983894L (no) 1996-02-26 1998-08-25 Optisk TDMA-nettverk med m°rke pulser

Applications Claiming Priority (12)

Application Number Priority Date Filing Date Title
GBGB9604020.9A GB9604020D0 (en) 1996-02-26 1996-02-26 Optical network
GB9604020.9 1996-02-26
EP96301277 1996-02-26
EP96301277.8 1996-02-26
GB9613345.9 1996-06-26
EP96304694.1 1996-06-26
GBGB9613345.9A GB9613345D0 (en) 1996-06-26 1996-06-26 Optical network
EP96304694 1996-06-26
EP96307207A EP0835002A1 (fr) 1996-10-02 1996-10-02 Réseau optique
GB9620502.6 1996-10-02
EP96307207.9 1996-10-02
GBGB9620502.6A GB9620502D0 (en) 1996-10-02 1996-10-02 Optical network

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WO1997031436A1 true WO1997031436A1 (fr) 1997-08-28

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PCT/GB1997/000520 WO1997031436A1 (fr) 1996-02-26 1997-02-25 Reseau optique a acces multiple par repartition dans le temps a impulsions obscures

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EP (1) EP0883938A1 (fr)
JP (1) JP2002516043A (fr)
KR (1) KR19990087351A (fr)
AU (1) AU732674B2 (fr)
CA (1) CA2245716A1 (fr)
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WO2001073981A1 (fr) * 2000-03-27 2001-10-04 Siemens Aktiengesellschaft Generateur de signaux optiques de donnees rz et procede correspondant
US6381056B1 (en) 1995-03-31 2002-04-30 British Telecommunications Public Limited Company Dark pulse generation and transmission

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Publication number Priority date Publication date Assignee Title
US6381056B1 (en) 1995-03-31 2002-04-30 British Telecommunications Public Limited Company Dark pulse generation and transmission
WO2000002334A3 (fr) * 1998-05-31 2000-04-27 Sun Microsystems Inc Procede et appareil de synchronisation binaire dans des systemes optiques de reseau et de communication
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CN1061496C (zh) * 1998-06-09 2001-01-31 北京格林威通信技术有限公司 光传输网络中的自定时方法及设备
WO2001073981A1 (fr) * 2000-03-27 2001-10-04 Siemens Aktiengesellschaft Generateur de signaux optiques de donnees rz et procede correspondant

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AU1888297A (en) 1997-09-10
NZ331214A (en) 1999-10-28
NO983894D0 (no) 1998-08-25
KR19990087351A (ko) 1999-12-27
CA2245716A1 (fr) 1997-08-28
AU732674B2 (en) 2001-04-26
NO983894L (no) 1998-08-26
EP0883938A1 (fr) 1998-12-16

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