EP2591581A1 - Procédé et dispositif de traitement de données dans un réseau de communication optique - Google Patents

Procédé et dispositif de traitement de données dans un réseau de communication optique

Info

Publication number
EP2591581A1
EP2591581A1 EP10730166.5A EP10730166A EP2591581A1 EP 2591581 A1 EP2591581 A1 EP 2591581A1 EP 10730166 A EP10730166 A EP 10730166A EP 2591581 A1 EP2591581 A1 EP 2591581A1
Authority
EP
European Patent Office
Prior art keywords
phase
signal
level
modulation
modulator
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Withdrawn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
EP10730166.5A
Other languages
German (de)
English (en)
Inventor
Arne Striegler
Mohammad Saeed Alfiad
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.)
Xieon Networks SARL
Original Assignee
Nokia Siemens Networks Oy
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 Nokia Siemens Networks Oy filed Critical Nokia Siemens Networks Oy
Publication of EP2591581A1 publication Critical patent/EP2591581A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H04L27/20—Modulator circuits; Transmitter circuits
    • H04L27/2003—Modulator circuits; Transmitter circuits for continuous phase modulation
    • H04L27/2021—Modulator circuits; Transmitter circuits for continuous phase modulation in which the phase change per symbol period is not constrained
    • H04L27/2025—Modulator circuits; Transmitter circuits for continuous phase modulation in which the phase change per symbol period is not constrained in which the phase changes in a piecewise linear manner within each symbol period
    • 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
    • H04B10/516—Details of coding or 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
    • H04B10/516—Details of coding or modulation
    • H04B10/548—Phase or frequency modulation
    • H04B10/556—Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]
    • H04B10/5561—Digital phase 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
    • H04B10/58—Compensation for non-linear transmitter output
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/002—Transmission systems not characterised by the medium used for transmission characterised by the use of a carrier modulation
    • H04B14/008—Polarisation modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/024—Channel estimation channel estimation algorithms
    • H04L25/0242—Channel estimation channel estimation algorithms using matrix methods
    • H04L25/0244—Channel estimation channel estimation algorithms using matrix methods with inversion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H04L27/20—Modulator circuits; Transmitter circuits
    • H04L27/2096—Arrangements for directly or externally modulating an optical carrier

Definitions

  • the invention relates to a method and to a device for data processing in an optical communication network.
  • a communication system comprising at least one such device.
  • QPSK quadrature phase shift keying
  • POLMUX polarization multiplexing
  • QPSK polarization multiplexed QPSK
  • CD chromatic dispersion
  • PMD polarization mode dispersion
  • the problem to be solved is to overcome the disadvantages mentioned above and in particular to provide a modulation format that provides an improved transmission performance with reduced bit pattern effects.
  • phase modulation is conducted comprising several phase states
  • phase states is gradually conducted.
  • the change of the phase state is in particular conducted continuously, stepwise or systematically
  • Such gradually conducted phase state change comprises, e.g., a smooth adaptation between phase states and thereby reduces high frequency modulations thereby allowing the optical signal power to remain
  • the approach presented herein provides a modulation format, which has a high spectral efficiency and is robust against distortions caused by non-linear effects. For example, an increase of about 300% transmission reach compared to yet existing 40G POLMUX-QPSK modulation can be achieved.
  • the phase state change is conducted over a given period of time from one phase state to a resulting phase state.
  • the given period of time is a portion of a duration of a bit period.
  • the given period of time may be more than 50% of the duration of the bit period.
  • phase states are based on a multi-level electrical signal, wherein level changes of this multi-level electrical signal are gradually conducted
  • the electrical signal can be fed to the phase modulation, in particular to a phase modulator conducting the phase modulation.
  • the electrical signal can be such multi-level data signal, wherein the stages or levels of the multi-level data signal are mapped to phase states of the optical signal. The transition between different levels of the electrical signal can be gradually conducted thereby avoiding abrupt changes and thus high frequencies in the phase modulated signal.
  • the gradually changing phase states can be obtained by applying a gradually changing electrical signal to the phase modulator.
  • phase states can be mapped to the multi-level electrical signal.
  • Two or more phase states may be used.
  • a state change of the phase state can be regarded as phase shift.
  • a level change of the multi-level electrical signal is conducted over a given period of time from one level to a resulting level. It is also an embodiment that the phase state change is provided by a phase modulator, in particular by a
  • the light source may be a (continuous wave) laser source.
  • the phase modulation is based on a bipolar modulation or any m-array modulation.
  • m may be an integer larger than 1.
  • the phase modulation is
  • a first carrier of a first polarization and a second carrier of a second polarization are provided at different frequencies.
  • distortions by non-linear effects between the two polarization planes can be further reduced by introducing an offset of the carrier frequency of the two polarization planes.
  • frequencies are provided each by a separate light source, e.g., utilized in a transmitter of the optical
  • the carriers of different frequencies are provided by a single light source wherein the light signal of the single light source is split into two parts, - wherein to the first part of the light signal a
  • linearly increasing phase shift over time can be added in particular by a first Mach-Zehnder modulator
  • a linearly decreasing phase shift over time can be added in particular by a second Mach-Zehnder modulator .
  • additional modulator stage can be combined with an optional pulse carver (in case a RZ signal is required) .
  • the carrier offset may be achieved by different modulators as the Mach-Zehnder modulator indicated above.
  • a portion of the linearly increasing phase shift over time can be added to the first part of the light signal.
  • a serrated signal can be used to provide such portion of linear increasing phase shift over time (for a predefined period of time) .
  • phase modulator being arranged to conduct a phase modulation utilizing several phase states, wherein a phase state change between different phase states is gradually conducted.
  • the phase modulator provides a phase- modulated signal based on a multi-level electrical signal, wherein a level change of the multi-level electrical signal is conducted over a given period of time from one level to a resulting level.
  • the device comprises
  • phase modulator is
  • the device comprises another phase modulator that is connected to the splitter.
  • the other phase modulator can be supplied by the same light source or by a different light source providing two polarized optical signals, e.g., with an offset of a predetermined frequency.
  • the splitter is a polarization beam splitter or a polarization multiplexer.
  • the problem stated supra is also solved by a method for processing data, in particular demodulating data, wherein said data were in particular modulated as described above, wherein the method analyzes a slope of a phase change and/or an absolute phase state of a signal, in particular by considering at least one preceding phase state.
  • a demodulator for processing data, wherein said demodulator is arranged for analyzing a slope of a phase change and/or for analyzing an absolute phase state of a signal in particular by
  • a communication system comprising at least one device as described herein.
  • Fig.l shows a schematic block diagram of a POLMUX-RZ-PSK transmitter structure with two- and four- dimensional constellation diagrams
  • Fig.2 shows a schematic block diagram of a coherent
  • Fig.3 shows a schematic block diagram of the digital
  • Fig.4 shows a schematic diagram of a transmitter th
  • Fig.5 shows an exemplary diagram of an unfiltered
  • Fig.6 shows a diagram based on Fig.5 visualizing as how a demodulator can detect a signal by analyzing an absolute phase state as well as a slope of a phase change .
  • FIG.l shows a schematic block diagram of a POLMUX-RZ-DQPSK transmitter structure with two- and four-dimensional constellation diagrams 116, 117.
  • a signal from a light source 101 e.g., a CW-laser
  • MZM 102 Mach-Zehnder-Modulator
  • an electrical signal 103 e.g. a substantially CW-laser
  • the output of the MZM 102 is split into a branch 104 and into a branch 105.
  • the outputs of the branches 104, 105 are combined by a polarization beam splitter PBS 106, which provides a modulated output signal 107.
  • the branch 104 comprises two parallel MZMs 108, 109, wherein the MZM 108 is connected with a ( ⁇ /2) phase shifter 110.
  • a modulation with an electrical signal 111 also referred to as precoded I-signal
  • a modulation with an electrical signal 111 is conducted and at the modulator MZM 109, a modulation with an electrical signal 111 (also referred to as precoded I-signal) is conducted and at the modulator MZM 109, a modulation with an electrical signal 111 (also referred to as precoded I-signal) is conducted and at the modulator MZM 109, a modulation with an electrical signal 111 (also referred to as precoded I-signal) is conducted and at the modulator MZM 109, a modulation with an electrical signal 111 (also referred to as precoded I-signal) is conducted and at the modulator MZM 109, a modulation with an electrical signal 111 (also referred to as precode
  • electrical signal 112 (also referred to as precoded Q- signal) is conducted.
  • the branch 105 comprises two parallel MZMs 113, 114, wherein the MZM 113 is connected with a ( ⁇ /2) phase shifter 115.
  • MZM 113 a modulation with the electrical signal 111 is conducted and at the modulator MZM 114, a modulation with the electrical signal 112 is conducted.
  • the transmitter of POLMUX-RZ-DQPSK provides a similar signal as does a common DQPSK modulator.
  • the transmitter of Fig.l provides two structures, one for each polarization.
  • RZ return-to-zero
  • a so-called pulse carver can be added after the CW-laser.
  • This pulse- carver is realized by the MZM 102.
  • the signal from the pulse carver is split up into the two branches 104, 105, by, e.g., using a 3dB splitter 118.
  • Both branches 104, 105 are separately DQPSK- modulated using a common QPSK-modulator .
  • the two DQPSK-modulated signals are combined by the PBS 106, which multiplexes the signals from the branches 104, 105 onto orthogonal polarizations.
  • the effect of the pulse carver can be determined as the output of the transmitter contains pulses. Every pulse (the middle) carries two phases of the two distinct signals. In total 16 combinations are possible.
  • the rate of pulses equals the total bitrate divided by four. This means that one symbol contains information of 4 bits, thus resulting in 4 bits per symbol.
  • Fig.2 shows a schematic block diagram of a coherent receiver processing the POLMUX-RZ-DQPSK signals conveyed by the transmitter shown in Fig.l and described above.
  • An incoming signal 201 is split by a PBS 202 into two orthogonal polarization components E sculptureX 203 and E sculptureY 204, which are a mixture of the two original signals as
  • Both polarization components 203, 204 are fed to a 90° optical hybrid 205, 206, where they are mixed with an output signal of a LO-laser 207.
  • the signal of the LO-laser 207 is fed to a PBS 208, where it is split into a component E L0 , X 209 and a component E L0 , y 210.
  • the component 209 is conveyed to the 90° optical hybrid 205 and the component 210 is conveyed to the 90° optical hybrid 206.
  • the optical hybrid 205, 206 is in detail summarized by a block 229.
  • the LO-laser 207 may be a free-running laser and it may be aligned with the transmitter laser within a frequency range of several hundred megahertz. This alignment can be
  • DSP digital signal processing
  • CPE carrier phase estimation
  • Distortions from direct detected signal components can be minimized by using a high LO-to-signal power ratio.
  • the signals from the photodiodes 213 to 220 are combined (via elements 221 to 224) and amplified (via amplifiers 225 to 228) .
  • the amplified signals are digitized by analog-to-digital converters (ADCs) of a unit 212.
  • ADCs analog-to-digital converters
  • the digital signal processing block 211 may control the gain of the drivers 225 to 228 and/or adjust the frequency of the LO-laser 207.
  • Fig.3 shows a schematic block diagram of the digital signal processing block 211. Such digital processing may be conducted in the electrical domain of the coherent receiver shown in Fig .2.
  • the signals fed to the digital signal processing block 211 are conveyed to a frequency domain equalization (FDE) stage 301, which is applied to estimate and compensate an
  • the FDE stage 301 is followed by a clock recovery 302 and a time domain equalization (TDE) stage 303 to
  • the signal is transferred into the frequency domain using FFT .
  • the frequency domain is better suited to compensate for the CD, because here the inverse linear part of the Schrodinger equation can be applied.
  • the signal is transformed back to the time domain using IFFT. As CD compensation is applied per polarization (see Fig.3), the FDE stage 301 is not able to demultiplex the polarizations.
  • the clock recovery 302 is
  • the PBS 202 splits the received signal 201 into two (arbitrary) orthogonal polarization components 203, 204.
  • a matrix H (transfer function) can be determined, which may be an approximation of the inverse matrix H to reverse the linear effects of the channel.
  • the matrix H can be
  • H [h xx h yx ; h xy h yy ] , which is represented by a butterfly structure of the TDE stage 303 shown in Fig.3. Multiplying the received signal with the transfer function H, an approximation of the transmitted signal can be determined. Hence, the TDE stage 303 can compensate for the residual CD, PMD and demultiplex the two polarizations.
  • the CD may (substantially) totally be compensated in this TDE stage 303; however such compensation requires extensive calculations. It is also possible to determine the transfer function H using methods such as the constant modulus algorithm (CMA) or the least mean square (LMS) algorithm. Using these algorithms, the coefficients of the transfer function H can be adapted over time to be able to track fast changes regarding the polarization state of the signal or changes of the channel characteristics.
  • CMA constant modulus algorithm
  • LMS least mean square
  • the TDE stage 303 may provide a limited tolerance towards nonlinear impairments.
  • the signal is processed by a carrier recovery 304, which corrects an offset in frequency and phase between the transmitter and LO-laser 207 (e.g., by using the Viterbi-and-Viterbi algorithm) .
  • a frequency offset can be estimated by
  • carrier phase estimation is applied to remove the phase offset.
  • a DQPSK decoder 306 determines the resulting bit stream.
  • Fig.3 also visualizes constellations that could be
  • the approach provided herewith suggests a modulation format that could work with a common coherent receiver.
  • the improvement is based on reducing bit pattern effects by phase modulation of a continuous wave signal, so that the signal after modulation has a (substantially) constant amplitude .
  • This modulation scheme can be applied to different
  • modulation formats such as bipolar-modulation, or m-array modulation. It can be combined with polarization
  • abbreviation CA stands for "continuous amplitude" and is in particular used to indicate the modulation format suggested herein.
  • Fig . 4 shows a schematic diagram of a transmitter that generates a CA-POLMUX-PSK modulation format.
  • a light signal is provided by a light source 401, e.g., a continuous wave laser, at a frequency fo-
  • the light source 401 is coupled to a phase modulator 402.
  • the phase modulator 402 is fed with an electrical (data) signal y e i provided by a unit 403.
  • the output of the phase modulator 402 is conveyed to a polarization beam splitter (PBS) 404 and the output of the PBS 404 is conveyed to an (optional) optical bandpass filter (OBF) 405.
  • PBS polarization beam splitter
  • OPF optical bandpass filter
  • the signal from the light source 401 is also fed to a phase modulator 406 to which an electrical (data) signal y e i is conveyed by a unit 407.
  • the output of the phase modulator 406 is conveyed to the PBS 404.
  • the phase modulator 402, 406 modulates the signal from the light source 401 according to, e.g., a 4-level electrical signal pursuant to the following mapping:
  • mapping is merely an example. Other mappings of signals of different levels may be applicable accordingly .
  • Fig.5 shows an exemplary diagram of an unfiltered
  • mapping can be changed accordingly.
  • a phase shift of 3 ⁇ 4,, ⁇ ⁇ /2 is added to the signal by the phase modulator 402, 406.
  • the phase is modulated such that the phase increases or decreases from one phase state to the next phase state over a time period
  • T symbol indicates a duration of one symbol.
  • Such symbol may comprise one bit or several bits.
  • phase does not abruptly jump to the discrete phase states; hence, high frequency modulations are avoided and the optical signal power can remain substantially constant.
  • a constellation diagram in a polarization plane reveals that the phase state changes between 0: ⁇ and 3/2 - and the absolute value of the signal is (substantially)
  • the pulse peak power is higher than the mean power and as a result non-linear effects are higher in these modulation formats.
  • the receiver hardware may be maintained unchanged.
  • a receiver as commonly used for POLMUX-QPSK or the like can be used.
  • the light source 401 in Fig.l can be replaced by two light sources, wherein a first light source is connected to the phase modulator 402 and a second light source is connected to the phase modulator 406.
  • the first light source may provide a continuous wave with an offset amounting to fo+Af and the second light source may provide a continuous wave with an offset amounting to fo ⁇ Af.
  • the PBS 404 can be replaced by a polarization multiplexer.
  • the two polarized signals are obtained with an offset amounting to 2Af.
  • phase shift can be realized by a frequency modulator or by directly modulating the light source, e.g., a laser diode.
  • phase shift can be provided by a non-linear effect, e.g., by a cross-phase-modulation, thereby using a non-linear element (for example a highly non-linear fiber) .
  • a gradual phase change could be utilized accordingly.
  • a delay line interferometer and/or a balanced detection can be used, because in such scenario pulses are carved out by the phase information.
  • a traditional DPSK receiver can be used and the transmission performance can be increased.
  • Fig.6 shows the diagram of Fig.5, wherein an interval between a point 601 and a point 602 can be used to detect the signal by analyzing the slope of the phase change by a demodulator. An interval between a point 603 and a point 604 can be used to detect the signal by analyzing the absolute phase state.
  • the demodulation can be achieved by analyzing the absolute phase value using a steady-state of the phase (with a duration amounting to T mm w— t mo a) . Also, the demodulation can be achieved by analyzing the slope during the gradual phase change (which lasts for a duration i m(il i) : Here, an information of a preceding phase state is required as well, because the slope depends on the phase state of the preceding bit (or symbol) .
  • demodulation may be optimized by adapting the parameter t, rii)d , i.e. in case of the slope analysis, t mod may be set as long as possible (e.g., t n K i— 3 s «*3 ⁇ 4o/) and in case of the absolute phase state, £ 7>!1 ,.; may have to remain short.
  • t mod may be set as long as possible (e.g., t n K i— 3 s «*3 ⁇ 4o/) and in case of the absolute phase state, £ 7>!1 ,.; may have to remain short.
  • a suitable compromise can be configured to provide
  • the CA phase modulation format suggested is robust against non-linear effects.
  • the CA modulation format in combination with carrier offset significantly increases the reach of the transmission.
  • the number of components providing 3R functionalities re ⁇ shape, re-time, re-amplify/re-generate
  • the reach can be further increased, because the absolute value of the dispersion coefficient at this wavelength is higher.

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

Abstract

L'invention concerne un procédé et un dispositif pour le traitement de données dans un réseau de communication optique, une modulation de phase étant conduite et comprenant plusieurs états de phase ; et un changement d'état de phase entre différents états de phase étant conduit graduellement. Elle concerne en outre un système de communication comprenant au moins un tel dispositif.
EP10730166.5A 2010-07-05 2010-07-05 Procédé et dispositif de traitement de données dans un réseau de communication optique Withdrawn EP2591581A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2010/059550 WO2012003856A1 (fr) 2010-07-05 2010-07-05 Procédé et dispositif de traitement de données dans un réseau de communication optique

Publications (1)

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EP2591581A1 true EP2591581A1 (fr) 2013-05-15

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JP5888056B2 (ja) * 2012-03-28 2016-03-16 富士通株式会社 デジタル光コヒーレント伝送装置
CN104144015B (zh) * 2013-05-09 2018-08-21 中兴通讯股份有限公司 实现可见光通信的方法、系统及发送装置和接收装置
JPWO2022244115A1 (fr) * 2021-05-18 2022-11-24
US20240143111A1 (en) * 2022-10-31 2024-05-02 Microchip Touch Solutions Limited Pseudoinverse-based noise equalization

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DE602008002051D1 (de) * 2008-04-11 2010-09-16 Alcatel Lucent Modulationsschema mit erhöhter Anzahl Polarisierungszustände

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WO2003028267A1 (fr) * 2001-09-26 2003-04-03 Celight, Inc. Attenuation de degradations de transmission non lineaire dans des systemes de communication par fibres optiques

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Title
BARRY J R ET AL: "Reduced-Bandwidth Duobinary Differential Continuous-Phase Modulation Format for Optical Communications", IEEE PHOTONICS TECHNOLOGY LETTERS, IEEE SERVICE CENTER, PISCATAWAY, NJ, US, vol. 17, no. 6, 1 June 2005 (2005-06-01), pages 1331 - 1333, XP011132351, ISSN: 1041-1135, DOI: 10.1109/LPT.2005.846572 *
BISHARA SHAMEE ET AL: "GauSsian Minimum Shift Keying for spectrally efficient and dispersion tolerant optical communications", CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (QELS), 2010 : 16 - 21 MAY 2010, SAN JOSE, CA, USA, IEEE, PISCATAWAY, NJ , USA, 16 May 2010 (2010-05-16), pages 1 - 2, XP031701845, ISBN: 978-1-55752-890-2 *
KERRY HINTON ED - LEIGH FISCHER ET AL: "Species of DPSK & DQPSK", OPTICAL FIBRE TECHNOLOGY/AUSTRALIAN OPTICAL SOCIETY, 2006. ACOFT/AOS 2006. AUSTRALIAN CONFERENCE ON, IEEE, PISCATAWAY, NJ, USA, 10 July 2006 (2006-07-10), pages 25 - 27, XP031252066, ISBN: 978-0-9775657-1-9 *
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