EP1256193A1 - Utilisation de signalisation optique coherente par decalage de phase dans des liaisons de fibres optiques multiplexees en longueur d'ondes - Google Patents

Utilisation de signalisation optique coherente par decalage de phase dans des liaisons de fibres optiques multiplexees en longueur d'ondes

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Publication number
EP1256193A1
EP1256193A1 EP01946995A EP01946995A EP1256193A1 EP 1256193 A1 EP1256193 A1 EP 1256193A1 EP 01946995 A EP01946995 A EP 01946995A EP 01946995 A EP01946995 A EP 01946995A EP 1256193 A1 EP1256193 A1 EP 1256193A1
Authority
EP
European Patent Office
Prior art keywords
optical
fiber
phase
phase shift
wavelength division
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.)
Withdrawn
Application number
EP01946995A
Other languages
German (de)
English (en)
Other versions
EP1256193A4 (fr
Inventor
Ralph Spickermann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Lockheed Martin Corp
Original Assignee
Lockheed Corp
Lockheed Martin Corp
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
Application filed by Lockheed Corp, Lockheed Martin Corp filed Critical Lockheed Corp
Publication of EP1256193A1 publication Critical patent/EP1256193A1/fr
Publication of EP1256193A4 publication Critical patent/EP1256193A4/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2543—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to fibre non-linearities, e.g. Kerr effect
    • H04B10/2563—Four-wave mixing [FWM]
    • 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
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
    • 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
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/612—Coherent receivers for optical signals modulated with a format different from binary or higher-order PSK [X-PSK], e.g. QAM, DPSK, FSK, MSK, ASK

Definitions

  • the present invention relates generally to wavelength division multiplexed optical fiber links, and more particularly, to the use of phase shift keyed coherent optical signaling to mitigate the effects of fiber refractive index nonlinearity in such links.
  • the effects of refractive index nonlinearities are three-fold, and are commonly known as self-phase modulation, cross-phase modulation and four wave mixing.
  • the motivation for the mitigation of these phenomena is that they lead to two limits on fiber optic link performance.
  • the first is a maximum limit on transmitted power, which leads to a maximum distance between optical amplifiers.
  • the second is a minimum limit on the frequency spacing between wavelength division multiplexed optical channels, which limits the total number of optical channels within the optical amplifier bandwidth and hence the total aggregate data capacity on a fiber.
  • the present invention provides for the use of phase shift keyed coherent optical signaling, in combination with inexpensive unmodified chromatic dispersion fiber (dispersion coefficient approximately 17 ps/(nm x km)), to permit simultaneous reduction of self- and cross-phase modulation and four wave mixing.
  • This in turn permits higher transmitted power and thus increased fiber length between optical amplifiers, and also allows tighter spacing between wavelength division multiplexed channels. This reduces the cost of the fiber link and increases the aggregate data transmission capacity per fiber.
  • the present invention uses a combination of phase shift keyed coherent optical signaling to mitigate self- and cross- phase modulation, and dispersive fiber to mitigate four wave mixing.
  • phase shift keying mitigates self- and cross-phase modulation
  • dispersive fiber to mitigate four wave mixing.
  • phase shift keying mitigates self- and cross-phase modulation is now explained.
  • Self- and cross-phase modulation and four wave mixing all arise from the inherently nonlinear refractive index of the glass optical fiber medium.
  • the origin of all three of these phenomena is that the refractive index of glass optical fiber varies instantaneously according to the local intensity of the laser light.
  • On-off keying which encodes the data through maximal variation of the intensity of the light, by its very nature maximizes this nonlinear action.
  • the nonlinear action distorts on-off keyed optical pulse symbols in the following way.
  • the nonlinear action in an optical pulse consists of the pulse itself locally changing the refractive index of the fiber medium in which it is traveling.
  • the peak of the pulse has a different local refractive index than the flanks. The more intense the pulse, the larger the refractive index distortion.
  • Self-phase modulation is defined as the resultant distortion of the optical phase within the pulse caused by its own optical energy.
  • Cross-phase modulation is defined as the distortion of the optical phase within a pulse caused by a coincident pulse from another wavelength division multiplexed channel. Note that the total local refractive index variation in a fiber is due to the instantaneous total optical energy of all the coincident pulses from all channels.
  • phase-shift keying presents a locally constant, uninterrupted optical intensity envelope to the fiber.
  • the nonhnear action therefore simply yields an altered but locally constant refractive index, which ideally results in no self- and cross-phase modulation. Rather, the nonhnear action yields a simple constant optical phase shift that causes no harm to a phase-shift keyed format. Therefore, the dispersion of the fiber need not be reduced, and four wave mixing remains suppressed. This results in higher limits on optical channel power, and thus improved overall link length. It also results in reduced allowable wavelength division multiplexed channel spacing. In fact, in new links, it may be advantageous to install increased chromatic dispersion fiber (> 17 ps/(nm x km)) to suppress four wave mixing further. This would allow even higher optical power and narrower optical channel spacing.
  • phase shift modulation for instance analog, binary phase shift keying, quaternary phase shift keying, and even higher orders of phase shift keying. All have a constant optical intensity envelope, and thus benefit from this invention.
  • QPSK quaternary phase shift keying
  • QPSK quadrature phase shift keying
  • the narrower optical spectrum of QPSK is less susceptible to chromatic dispersion than binary signaling.
  • the phase shift keyed wavelength division multiplexed fiber optic link comprises a phase shift keyed coherent transmitter and receiver coupled together by way of a periodically optically amplified fiber cable.
  • the phase shift keyed coherent transmitter comprises a plurality of phase shift keyed optical modulators that each receive a separate data waveform to be transmitted over the periodically optically amplified fiber cable.
  • a separate laser each at a unique wavelength, is coupled into each of the plurality of phase shift keyed modulators whose respective optical outputs are each modulated with one of the separate data waveforms.
  • Outputs of each of the phase shift keyed modulators are input to a wavelength division multiplexer which combines the phase shift keyed modulated optical outputs of the phase shift keyed modulators for transmission over the optically amplified fiber cable.
  • An exemplary periodically amplified fiber cable comprises the following. It is similar in nature to that typically used with on-off keying.
  • each period of fiber consists of a 30 to 150 kilometer length of dispersive fiber.
  • a low noise optical preamplifier At the end of each fiber length period, there is a low noise optical preamplifier, a fiber chromatic dispersion compensator and a booster optical amplifier.
  • the amplifier gains are such that the total link period has unity gain.
  • the total fiber link may include many such periods totaling thousands of kilometers.
  • the positioning of the chromatic dispersion compensator is now discussed. It is well known that positioning the dispersion compensation module between the optical preamplifier and booster amplifier is the best configuration for minimizing optical noise. For this reason, the dispersion compensator in prior art on-off keyed links is positioned in this way. Fortunately, this position is also ideal for the phase-shift keyed signaling method under consideration. This is because, although the phase shift keyed signal launched into the fiber link has a constant envelope, if the fiber is chromatically dispersive, the envelope will not remain constant. This may be understood by the following qualitative description of how the optical envelope of the phase-shift keyed signal changes as it propagates down the periodically amplified fiber link.
  • the signal will be very close to the ideal constant envelope of the phase shift keyed format.
  • the fiber chromatic dispersion will result in increasing differential phase distortion within the phase shift keyed optical signal spectrum.
  • this manifests itself as an evolving intensity modulation.
  • chromatically dispersive fiber is a phase modulation to amplitude modulation converter. This evolving intensity modulation is, like on-off keyed signals, subject to distortion by the fiber nonlinearity.
  • the signal travels it is also subject to inherent optical fiber loss, so as the phase-to-amplitude modulation conversion evolves, the signal is simultaneously attenuated. Depending on launch power levels, symbol rate and fiber dispersion magnitude, this loss can be rapid enough such that the absolute power fluctuation in the envelope will be insignificant as far as the fiber nonhnearity is concerned.
  • the QPSK modulation format is much less susceptible to this phase-to-amplitude modulation conversion and its attendant nonlinear effects than is binary signaling. This is because the QPSK optical spectrum is half as wide, and chromatic dispersion causes only half as much differential spectrum phase distortion.
  • the chromatic dispersion compensator restores the original optical spectrum phase and thus the original constant optical envelope. Importantly, it does so immediately before the booster optical amplifier increases the optical signal power back into the nonlinear region.
  • the chromatic dispersion compensator in existing prior art on- off keyed links is positioned to minimize optical noise. However, coincidentally this position is also such that the ideal phase shift keyed constant optical amplitude envelope is restored in the peak power regions immediately after amplification where fiber nonlinearity is most significant. Subsequently, natural fiber attenuation reduces the signal rapidly enough such that the evolving phase to amplitude modulation conversion due to chromatic dispersion does not result in significant nonlinear action.
  • phase modulated links the nonlinear action on the result of phase to amplitude modulation conversion imposes an upper limit on the amount of fiber dispersion that may be introduced to suppress four wave mixing. Higher dispersion results in faster phase to amplitude modulation conversion, thus larger absolute optical power envelope variation, thus more nonlinear action.
  • Full optimization of the phase shift keyed format involves a trade between launched power, symbol rate and dispersion value. Note that on-off keying results in maximum relative optical power variation at the peak power region after the booster optical amplifier and hence maximizes harmful fiber nonlinear action, while phase shift keying does the opposite.
  • the last periodic length of the fiber cable is coupled into the front end of the coherent receiver.
  • the front end of the receiver comprises either an optical power splitter or a wavelength division demultiplexing optical filter.
  • the splitter front end type would be used if access to all channels by any single demodulator is desired, or if optical channel spacing is closer than can be resolved by available demultiplexing filters.
  • the wavelength division demultiplexing optical filter would be used in case conservation of individual optical channel power is the dominant consideration. In either case, the front end of the receiver splits the received signal into a plurality of signals. Each of these is then coupled to a coherent optical demodulator.
  • the electrical data signal output of the demodulator is coupled to an electronic filter to remove undesired spectral elements from adjacent wavelength division multiplexed channels.
  • the electronic output of the filter is coupled into an equalizer to compensate for various channel nonidealities.
  • Fig. 1 illustrates an exemplary wavelength division multiplexed fiber optic link in accordance with the principles of the present invention
  • Fig. 2 illustrates an original conception for a four phase coherent optical costas loop demodulator, which would be used to demodulate the particularly beneficial Quaternary Phase Shift Keyed (QPSK) data format
  • QPSK Quaternary Phase Shift Keyed
  • Fig. 3 illustrates an exemplary method in accordance with the principles of the present invention.
  • Fig. 1 illustrates an exemplary wavelength division multiplexed fiber optic link 10 in accordance with the principles of the present invention.
  • the wavelength division multiplexed fiber optic link comprises a phase shift keyed (PSK) coherent transmitter 20 and receiver 30 coupled together by way of a periodically optically amplified fiber link 40.
  • the phase shift keyed coherent transmitter 20 comprises a plurality of phase shift keyed optical modulators 22 that each receive a separate electronic data waveform for transmission over the optically amplified fiber link 40.
  • WN is uniquely coupled to one of a plurality of optical phase shift keyed modulators 22 whose respective output beams are each modulated with a data waveform.
  • Outputs of each of the phase shift keyed modulators 22 are input to a wavelength division multiplexer 23 that combines the phase shift keyed modulated outputs of the phase shift keyed modulators 22 for transmission over the optically amplified fiber link 40.
  • the fiber link 40 is periodic in nature. Each period consists of a length of nondispersion shifted optical fiber 41 coupled to a two-stage erbium doped optical fiber amplifier (EDFA).
  • the two stage optical amplifier comprises a low noise optical preamplifier (EDFA) 42 and a high power booster amplifier (EDFA) 44.
  • DCM chromatic dispersion compensation module
  • An optical link may include many such periods totaling thousands of kilometers.
  • the chromatic dispersion of the fiber 41 causes waveform amplitude variation to evolve as the signal travels down the length of fiber 41, the phase shift keyed ideal constant envelope is restored by the chromatic dispersion compensation module immediately before the second stage optical amplifier 44 increases the optical power into the nonlinear region of operation.
  • the signal has a constant optical amplitude envelope in peak power regions immediately after amplification where nonlinearity is most significant. The nonlinearity thus yields only a harmless uniform optical phase shift.
  • the amplified output of the booster fiber amplifier 44 of the final link period is coupled into the receiver 30.
  • the front end of the receiver 30 may comprise an optical power splitter 31 whose input is coupled to the optically amplified fiber link 40.
  • This splitter 31 splits optical power equally into each of a plurality of coherent optical demodulators 33.
  • each demodulator 33 has simultaneous access to all the data channels, and any demodulator 33 may be tuned to demodulate any channel. Additionally, the spacing of the channels is not limited by the resolution of available optical filters.
  • the front end of receiver 30 may comprise a wavelength division multiplexed (WDM) demultiplexing optical filter 32, whose input is coupled to the optically ampUfied fiber hnk 40.
  • WDM wavelength division multiplexed
  • This filter 32 splits the incoming optical signal into a pluraUty of individual optical channels. This sphtting of the optical signal conserves the optical power of each channel.
  • the optical outputs of either type receiver front end 31, 32 are coupled to the coherent optical demodulators 33.
  • the structure of the demodulators 33 is dependent on the format of the phase shift keyed signal.
  • An embodiment of an exemplary four phase (QPSK) demodulator 33 is illustrated in Fig. 2.
  • the electrical signal output of the demodulators 33 is a reproduction of the transmitted data.
  • Both self- and cross-phase modulation are due to the nonlinearity with optical power of the propagation constant of the fiber 41.
  • Prior art on-off keyed pulses maximize distortion due to this nonlinearity. This limits the maximum launched optical power, which Umits the length of the link.
  • the coherent phase shift keyed modulation format used in the present invention transmits a constant optical power envelope which is minimally distorted, even in common high dispersion characteristic fiber 41.
  • the high dispersion characteristic fiber 41 also suppresses four wave mixing. This allows higher optical power to be transmitted, and hence allows a longer length fiber optic link 40. Additionally, suppression of four wave mixing allows for narrower wavelength division multiplexed channel spacing which results in more total capacity per fiber link 40.
  • the present invention uses a combination of phase shift keyed coherent optical signaling to mitigate self- and cross-phase modulation, and dispersive fiber 41 to mitigate four wave mixing. How phase shift keying mitigates self- and cross-phase mixing will now be explained in detail.
  • the nonlinear action in an optical pulse includes the laser pulse that locally changes the refractive index of the fiber medium in which it is traveUng. The peak of the pulse has a different local refractive index than its flanks.
  • Self -phase modulation is defined as the resultant distortion of the optical phase within the pulse caused by its own optical energy.
  • Cross-phase modulation is defined as the distortion of the optical phase within a pulse caused by a coincident pulse from another wavelength division multiplexed channel.
  • the total local refractive index variation in a fiber 41 is due to the instantaneous total optical energy of all the coincident pulses from all channels. The more closely spaced the optical channels, the more severe the cross phase modulation.
  • the distortion of the optical phase within the pulse due to the nonlinear action broadens the spectral content of the pulse, but does not in and of itself change the temporal pulse shape.
  • Temporal pulse shape change is brought about by the chromatic dispersion of the optical fiber 41 acting more rapidly on the broadened pulse spectrum.
  • phase-shift keying presents a locally constant, uninterrupted optical intensity envelope to the fiber.
  • the nonlinear action therefore yields an altered but locaUy constant refractive index, which ideally results in no self- and cross-phase modulation. Rather, the nonlinear action yields a simple constant optical phase shift that causes no harm to a phase-shift keyed format. Therefore, the dispersion of the fiber 41 need not be reduced, and four wave mixing remains suppressed. This results in higher limits on optical channel power, and thus improved overall tink length. It also results in reduced aUowable wavelength division multiplexed channel spacing.
  • phase shift modulation such as analog, binary phase shift keying, quaternary phase shift keying, and higher orders of phase shift keying, for example. All have a constant optical intensity envelope, and thus benefit from the present invention.
  • QPSK quaternary phase shift keying
  • QPSK quadrature phase shift keying
  • the narrower optical spectrum of QPSK is less susceptible to chromatic dispersion than binary signaling.
  • the fiber optic link 40 comprises a phase shift keyed coherent transmitter 20 and receiver 30 coupled together by way of a periodically optically amplified fiber cable.
  • the phase shift keyed coherent transmitter 20 comprises a plurality of phase shift keyed optical modulators 22 that each receive a separate data waveform to be transmitted over the periodically optically amplified fiber link 40.
  • a separate laser 21, each at a unique wavelength, is coupled into each of the plurality of phase shift keyed modulators 22 whose respective optical outputs are each modulated with one of the separate data waveforms.
  • Outputs of each of the phase shift keyed modulators 22 are input to a wavelength division multiplexer 23 which combines the phase shift keyed modulated optical outputs of the phase shift keyed modulators 22 for transmission over the optically amplified fiber link 40.
  • An exemplary periodically amplified fiber link 40 comprises the following. It is similar in nature to that typically used with on-off keying. Depending on the total length of the link 40, each period of fiber 41 is a 30 to 150 kilometer length of dispersive fiber 41. At the end of each fiber length period, there is a low noise optical pre-amplifier 42, a fiber chromatic dispersion compensator 43 and a booster optical amplifier 44. The gains of the respective amplifiers 42, 44 are such that the total link period has unity gain.
  • the total fiber link 40 may include many such periods totaling thousands of kilometers.
  • the signal will be very close to the ideal constant envelope of the phase shift keyed format.
  • the fiber chromatic dispersion produces increasing differential phase distortion within the phase shift keyed optical signal spectrum.
  • chromatically dispersive fiber is a phase modulation to amplitude modulation converter.
  • This evolving intensity modulation is, like on-off keyed signals, subject to distortion by the fiber nonlinearity.
  • the signal travels it is also subject to inherent optical fiber loss, so as the phase-to-amplitude modulation conversion evolves, the signal is simultaneously attenuated.
  • the chromatic dispersion compensation module 43 restores the original optical spectrum phase and thus the original constant optical envelope. Importantly, it does so immediately before the booster optical amplifier 44 increases the optical signal power back into the nonlinear region.
  • the chromatic dispersion compensator in prior art on-off keyed links is positioned to minimize optical noise. However, coincidentally this position is also such that the ideal phase shift keyed constant optical amplitude envelope is restored in the peak power regions immediately after amplification where fiber nonlinearity is most significant.
  • phase modulated links the nonlinear action on the result of phase to amplitude modulation conversion imposes an upper limit on the amount of fiber dispersion that may be introduced to suppress four wave mixing. Higher dispersion results in faster phase to amplitude modulation conversion, thus larger absolute optical power envelope variation, thus more nonlinear action.
  • Full optimization of the phase shift keyed format involves a trade between launched power, symbol rate and dispersion value. On-off keying results in maximum relative optical power variation at the peak power region after the booster optical ampUfier 44 and hence maximizes harmful fiber nonlinear action, while phase shift keying does the opposite.
  • the last periodic length of fiber 45 is coupled into the front end of the coherent receiver 30.
  • the front end of the receiver 30 comprises either an optical power splitter 31 or a wavelength division demultiplexing optical filter 32.
  • the splitter front end type is used if access to all channels by any single demodulator 33 is desired, or if optical channel spacing is closer than can be resolved by available demultiplexing filters.
  • the wavelength division demultiplexing optical filter 32 is used in case conservation of individual optical channel power is the dominant consideration. In either case, the front end of the receiver 30 splits the received signal into a plurality of signals. Each of these is then coupled to a coherent optical demodulator 33.
  • Fig. 2 illustrates an exemplary embodiment of a four phase coherent optical costas loop demodulator 50.
  • this optical demodulator 50 fulfills the function of each coherent optical demodulator 33 used in the fiber optic link 10 shown in Fig. 1.
  • the QPSK modulated optical input (Iopt) and the local oscillator output (LO) of a high power, narrow linewidth semiconductor distributed feedback (DFB) local laser 52 are input into a 90 degree optical hybrid 51. There are two outputs from the 90 degree optical hybrid 51. Each output includes equal parts of the inputs, but there is a 90 degree relative optical phase difference introduced in one output.
  • Each output of the 90 degree optical hybrid 51 is input into one of two photodiodes 53 which act as optical mixers to produce in-phase and quadrature data signals I, Q.
  • the in-phase and quadrature data signals are low pass filtered 54 to remove undesired remnants of adjacent wavelength division multiplexed optical channels to produce I and Q data. Copies of the data are electrically mixed in mixers 55, and a sum 56 of the mixing products is produced. This sum corresponds to the phase error of the LO to the input signal optical carrier.
  • This error signal is low pass filtered 57 and used to adjust the laser current 58 and hence the frequency of the local laser 52 to maintain phase lock.
  • the temperature of the laser is controlled 59 and may be varied to tune the distributed feedback laser 52 to a particular input optical wavelength.
  • Fig. 3 iUustrates an exemplary optical signaling method 70 in accordance with the principles of the present invention.
  • the exemplary optical signaling method 70 comprises the following steps.
  • phase shift key modulated 71 Data in a plurality of data channels that are to be transmitted over an optically amplified fiber link are phase shift key modulated 71, such as by using an individual plurality of lasers, for example.
  • the respective phase shift keyed modulated signals are then wavelength division multiplexed 72.
  • the wavelength division multiplexed signals are transmitted 76 over an optical fiber 73, amplified 74, processed 75 to compensate for chromatic dispersion, and amplified 76 a second time.
  • the previous four steps (73-76) are repeated 77 a predetermined number of times to achieve a desired total optical fiber link length.
  • the signals transmitted over the fiber link are separated 78 into a pluraUty of data channels.
  • the signals in each of the data channels are coherently optically demodulated 79 to produce data for the respective channels.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Nonlinear Science (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention concerne une liaison par fibre optique (40) multiplexée en longueur d'ondes (23) comprenant un émetteur (20) cohérent à décalage de phase et un récepteur (30) couplés par l'intermédiaire d'une liaison par fibre (42, 44) périodique amplifiée optiquement. L'émetteur comporte plusieurs modulateurs (22) à décalage de phase recevant chacun des données à émettre sur la liaison par fibre. Un laser séparé (21) est couplé à chacun des modulateurs (22) dont les faisceaux de sortie respectifs sont modulés avec les données à émettre. Les sorties des modulateurs sont entrées dans un multiplexeur (23) en longueur d'ondes qui multiplexe les sorties modulées par décalage de phase des modulateurs pour émission sur la liaison par fibre. Le récepteur (30) comprend un diviseur (31) de puissance optique ou un démultiplexeur en longueur d'ondes (32) qui produit plusieurs canaux de données. Un démodulateur optique cohérent (33) permet de démoduler tous ces canaux de données afin de produire des données pour chaque canal de données. L'invention concerne aussi un procédé de signalisation correspondant.
EP01946995A 2000-01-26 2001-01-11 Utilisation de signalisation optique coherente par decalage de phase dans des liaisons de fibres optiques multiplexees en longueur d'ondes Withdrawn EP1256193A4 (fr)

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US49127400A 2000-01-26 2000-01-26
US491274 2000-01-26
PCT/US2001/000851 WO2001056196A1 (fr) 2000-01-26 2001-01-11 Utilisation de signalisation optique coherente par decalage de phase dans des liaisons de fibres optiques multiplexees en longueur d'ondes

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US7599627B2 (en) 2001-05-31 2009-10-06 Teradvance Communications, Llc Method and system for a polarization mode dispersion tolerant optical homodyne detection system with optimized transmission modulation
US9337948B2 (en) 2003-06-10 2016-05-10 Alexander I. Soto System and method for performing high-speed communications over fiber optical networks
WO2011126943A2 (fr) * 2010-04-09 2011-10-13 Nec Laboratories America, Inc. Optimisation de la puissance des récepteurs optiques

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US5101450A (en) * 1991-01-23 1992-03-31 Gte Laboratories Incorporated Quadrature optical phase modulators for lightwave systems
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TAKASHI ONO ET AL: "Characteristics of Optical Duobinary Signals in Terabit/s Capacity, High-Spectral Efficiency WDM Systems" JOURNAL OF LIGHTWAVE TECHNOLOGY, XX, XX, vol. 16, no. 5, May 1998 (1998-05), XP011029133 ISSN: 0733-8724 *

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