WO2006058830A1 - Procede de compensation de la diaphonie entre reel et reel fonction de la sequence des bits du a une diffusion raman stimulee, systeme de transmission longueur d'onde optique-multiplex et convertisseur de longueur d'onde optique - Google Patents

Procede de compensation de la diaphonie entre reel et reel fonction de la sequence des bits du a une diffusion raman stimulee, systeme de transmission longueur d'onde optique-multiplex et convertisseur de longueur d'onde optique Download PDF

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Publication number
WO2006058830A1
WO2006058830A1 PCT/EP2005/055914 EP2005055914W WO2006058830A1 WO 2006058830 A1 WO2006058830 A1 WO 2006058830A1 EP 2005055914 W EP2005055914 W EP 2005055914W WO 2006058830 A1 WO2006058830 A1 WO 2006058830A1
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WO
WIPO (PCT)
Prior art keywords
wavelength
transmission path
dispersion
channels
band
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Application number
PCT/EP2005/055914
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German (de)
English (en)
Inventor
Peter Krummrich
Original Assignee
Siemens Aktiengesellschaft
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 Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO2006058830A1 publication Critical patent/WO2006058830A1/fr

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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
    • H04B10/2537—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to scattering processes, e.g. Raman or Brillouin scattering
    • 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
    • H04B10/2531—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion using spectral inversion

Definitions

  • the invention relates to a method according to the preamble of patent claim 1, an optical wavelength division multiplex transmission system according to the preamble of patent claim 10 and an optical wavelength converter for a WDM system.
  • WDM wavelength division multiplexing
  • bit-pattern dependent crosstalk through stimulated Raman scattering abbreviated SRS-XT
  • SRS-XT bit pattern dependent Raman induced cross talk
  • Stimulated Raman scattering causes an energy transfer from shorter, so-called “blue” wavelengths to longer, so-called “red” wavelengths and causes a coupling between the channels.
  • a frequency range or wavelength range used for the transmission of a data signal is referred to as a channel. This frequency range corresponds approximately to the signal bandwidth and is for example 50 GHz in the 3rd transmission window. Due to the stimulated Raman scattering, the channels with the smaller wavelengths additionally undergo attenuation, while channels with the longer wavelengths have an attenuation. attenuation or gain experienced. This gain or additional damping is time-dependent.
  • the strength of the Raman effect also depends on the bit sequences transmitted in the individual channels.
  • the individual pulses in short wavelength channels experience a great deal of additional attenuation when many "1" bits are transmitted at the same time in many adjacent channels of longer wavelengths. When many "0" bits are transmitted in the other channels, there is little additional attenuation.
  • pulses in channels with long wavelengths gain gain when many "1" bits are transmitted at the same time in many channels with shorter wavelengths, and almost no change when many "0" bits are transmitted.
  • the dispersion-induced walkoff between the channels must also be taken into account for a more detailed analysis of the SRS-XT.
  • a walkoff between the channels is due to the different transit times of the signals at the different wavelengths due to the fiber dispersion. This means that due to the dispersion, the pulses in the individual channels pass each other during the transmission. The amplification or attenuation by a transmitted "1" signal in one channel will affect the other channels due to the dispersion over several pulses. The dispersion consequently affects the position of the individual pulses in the channels, while the crosstalk caused by SRS alters the amplitude of the pulses.
  • a certain reduction in the strength of the influence of SRS-XT can be achieved by using transmission fibers with high dispersion coefficients.
  • the aforementioned walkoff i. the propagation time differences of the signals at different wavelengths is increased with strong dispersion and there is a faster passing together of the pulses in the channels with different wavelengths.
  • the fibers with the highest dispersion coefficients occurring in practical use are standard single-mode fibers (SSMF). Fibers with higher dispersion coefficients have distinct disadvantages with regard to other transmission properties (pulse distortions, phase distortions).
  • transmission systems with the already deployed SSMF must be able to achieve long ranges. Even with SSMF, SRS-XT limits the possible range in systems with many channels or wide channel spacing.
  • the invention has for its object to provide a method and arrangements, which allows an improvement of the transmission properties in WDM systems by compensation of SRS-XT.
  • the advantage of the invention is that at least partial compensation of SRS-XT is achieved by converting the wavelengths within the transmission path, which leads to a greater transmission range.
  • a dispersion curve is used, through which a ne temporal synchronization of the bit sequences is to be achieved in order to allow the best possible compensation of the SRS-XT.
  • Another advantage of the invention is that the method is easy to implement. In principle, only one additional unit for wavelength conversion is required in a WDM system.
  • dispersion overcompensation is used in a first part of the transmission path and dispersion undercompensation is used in a second part of the transmission path or vice versa.
  • a dispersion full compensation is performed after each link section.
  • a wavelength converter could be switched on dynamically.
  • An additional advantage of the invention is that according to dependent claim 6, the transmission path can be divided into more than two parts, between which the wavelength converter is inserted.
  • a multiple wavelength conversion has the advantage that the gain or attenuation of the bits is better regulated.
  • FIG. 1 shows a sketch which is intended to show the effects of the bit pattern-dependent crosstalk due to the Raman effect during the transmission in a section of a WDM transmission system (without consideration of dispersion).
  • FIG. 2 shows the block diagram of a WDM transmission system with a plurality of link sections and a wavelength converter according to the invention in the middle of the transmission system.
  • FIG. 3 shows a possible arrangement of the wavelength converter according to the invention.
  • FIG. 4 shows a representation of a possible dispersion compensation scheme for the individual route sections.
  • the power of the "1" bit with the number 3 at ⁇ i increases on the receiver side as it increases at ⁇ 3 .
  • the power of the "1" bit numbered bit 5 at ⁇ i and ⁇ 2 remains constant since in the other channels, only "O" bits occur at the same time, in simple terms this means that amplification only occurs when "1" bits in at least two channels are transmitted simultaneously.
  • this presentation does not take into account the effects of dispersion. Due to the dispersion-related walkoff and the concomitant
  • FIG. 2 shows the block diagram of a WDM transmission system.
  • the carrier signals emerging from the transmittors Ti to T M are modulated with data signals either directly or by means of modulators.
  • the resulting optical signals OSi to 0S M are then combined with a multiplexer MUX to a transmission-side WDM signal WS.
  • the WDM signal WS accordingly comprises M channels at the center wavelengths ( ⁇ i, ⁇ 2 ,..., ⁇ M ).
  • the WDM signal WS is now transmitted in a transmission path which consists of N route sections SA.
  • Each track section SA contains a piece of an optical waveguide SSMF, for example a standard monomode fiber, an optical amplifier OAl, a piece of dispersion-compensating fiber DCF and a further optical amplifier 0A2.
  • the transmission link is divided into two parts in this embodiment. Between two link sections SA, a wavelength converter WU is inserted. In a preferred embodiment of the method according to the invention, the wavelength converter WU is introduced in the middle of the transmission path if the number of route sections is even (for example 2N).
  • the Transmission line does not have to be divided into two equal lengths.
  • the wavelength converter WU converts the channel having the shortest wavelength ⁇ i to the one having the longest wavelength ⁇ M and, in turn, the channel having the longest wavelength ⁇ M to the one having the shortest wavelength ⁇ i.
  • the other channels it proceeds analogously in pairs, ie the channel with the second shortest wavelength ⁇ 2 is converted to the one with the second longest ⁇ (Mi) and so on.
  • one channel can be converted to an adjacent, previously unused wavelength.
  • Bits transmitted in short wavelength channels in the first half of the transmission system and experiencing additional attenuation are transmitted in long wavelength channels in the second half and gain.
  • the level distributions of the channels at the fiber inputs in front of and behind the wavelength converter WU must be the same, at least in pairs, for the same so-called Raman efficiencies of the fibers, ie for each section in the second half of the wavelength Systems should set up a stretch of track in the first half with the same level distribution.
  • the term Raman efficiency refers to the quotient of the Raman coefficient divided by the effective closed-field field. It is a size that is material-dependent and characterizes the strength of the Raman scattering and that also includes fiber parameters over the mode field area.
  • the wavelength-converted WDM signal WS K is divided after transmission in the second half of the transmission path on the receiving side with a demultiplexer DMUX in the individual channels and demodulated according to the transmission-side occupancy, so that the transmitted data signals receivers Ri to R M are supplied.
  • FIG. 3 illustrates a preferred embodiment of the wavelength converter WU.
  • a WDM signal WS is fed to a first band switch BW1, which splits the WDM signal into two subbands with channels of larger and smaller wavelengths TB1 and TB2.
  • Subband TB1 which contains the channels with the longer wavelengths, is supplied to a wavelength converter WK1.
  • the wavelength converter WK1 has the task of converting the channels with the longer wavelengths contained in sub-band TB1 to free, yet unoccupied channels with smaller wavelengths.
  • the channel with the largest wavelength ⁇ M is preferably converted to a free channel with the smallest wavelength ⁇ i, and the channel with the second largest wavelength ⁇ ( M i) is converted to a free channel having the second smallest wavelength ⁇ 2
  • the wavelength converter WK is preferably made of periodically poled lithium niobate (PPLN), for example by the non-linear process of four-wave mixing (FWM) in a pumped waveguide structure
  • PPLN periodically poled lithium niobate
  • FWM four-wave mixing
  • the channels with the smaller wavelengths of TB2 are converted into unoccupied channels with longer wavelengths.
  • the wavelengths are preferably mirrored with respect to a mean wavelength, analogous to the procedure at WK1.
  • a second band filter BW2 adds the converted sub-bands Tbl ⁇ k and TB2 together again.
  • BW2 filters can be inserted in front of the second band filter to suppress the remaining portions of the original channels and the remaining pump radiation.
  • the method according to the invention for suppressing SRS-XT uses a special dispersion compensation scheme in order to ensure temporal synchronization of the bits in the individual channels. If the wavelength converter WU is arranged, for example, in the middle of the transmission path, the dispersion compensation scheme must be selected such that there are pairs of path sections in front of and behind the wavelength converter WU, at whose inputs the same bits in the individual channels meet one another at a time , This is achieved if the same value of the accumulated dispersion is set for two selected route sections.
  • the same pairwise arrangement of the accumulated dispersion in front of and behind the wavelength converter must also be selected at the inputs of the dispersion-compensating fibers DCF, since SRS-XT can also occur in these. If the same value for the accumulated dispersion is not set at the inputs of the dispersion compensating fibers of paired sections, the input levels to the DCF must be chosen so low that no SRS-XT occurs in them.
  • Time synchronized bits at the fiber inputs can be achieved by a dispersion compensation scheme in which the dispersion of a link through a dispersion-compensating fiber completely compensates DCF becomes (full compensation). Thus, no accumulated dispersion occurs at the beginnings of the sections.
  • the accumulated dispersion is plotted against the length of the transmission path for individual sections of the route with the numbers 1 to 12.
  • section No. 1 at the beginning of the transmission path the value of the accumulated dispersion initially drops below zero. This is called pre-compensation.
  • the dispersion accumulated during transmission is greater than the dispersion compensated in the DCF, resulting in undercompensation per section.
  • the accumulated dispersion at the beginning of each segment thus increases.
  • overcompensation and post-compensation are used. This means that per dispersion section the dispersion compensation in the DCF is greater than the dispersion accumulated in the transmission fiber.
  • the size of the over- and undercompensation and the compensation in the middle of the transmission system are selected such that pairs of path sections occur in front of and behind the wavelength converter WU, which have the same accumulated dispersion at the input.
  • a configured according to FIG. 2 WDM system consists of 20 sections SSMF with a length of 100 km. In these 160 channels are to be transmitted, 80 in the C and 80 in the L band. The channels have a bit rate of 10 GBit / s and a channel spacing of 50 GHz.
  • the wavelength converter WU according to the invention is arranged after 10 route sections.
  • the dispersion compensation scheme has an undercompensation of 50 ps / nm per section ahead of the wavelength converter WU and over-compensation of -50 ps / nm.
  • the pre-compensation is -200 ps / nm
  • the after-compensation is -1200 ps / nm.
  • the input level into the DCF before the first section is chosen so low (total power less than 10 dBm) that no noticeable SRS-XT occurs.
  • the other input levels can be selected as high as the route layout allows.
  • the pairs of path sections in front of and behind the wavelength converter, which have the same accumulated dispersion also have equal distributions of the channel levels at the fiber input with the same Raman efficiency.

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

Abstract

L'invention vise à réduire la diffusion Raman due à une diaphonie entre réel et réel fonction de la séquence des bits dans un parcours de transmission optique. A cet effet, une conversion de longueur d'onde est effectuée entre deux sections de parcours, les canaux de petites longueurs d'ondes par paires étant convertis inversement en canaux à grandes longueurs d'ondes. Selon un mode de réalisation du procédé, on utilise un schéma de compensation de dispersion spécial pour lequel la dispersion accumulée avant et après le convertisseur de longueur d'onde est équilibrée pour des sections de parcours sélectionnées. Ainsi le transfert d'énergie dû à la diffusion Raman de canaux à petites longueurs d'ondes vers les canaux à grandes longueurs d'ondes est compensé en respectant le croisement des impulsions dû à la dispersion.
PCT/EP2005/055914 2004-12-02 2005-11-11 Procede de compensation de la diaphonie entre reel et reel fonction de la sequence des bits du a une diffusion raman stimulee, systeme de transmission longueur d'onde optique-multiplex et convertisseur de longueur d'onde optique WO2006058830A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102004058644.6 2004-12-02
DE200410058644 DE102004058644A1 (de) 2004-12-02 2004-12-02 Verfahren und Anordnung zur Kompensation des durch stimulierte Raman-Streuung verursachten bitmusterabhängigen Übersprechens

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WO2006058830A1 true WO2006058830A1 (fr) 2006-06-08

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008087490A3 (fr) * 2007-01-18 2011-03-03 Kleysen, Hubert, T. Procédé et appareil pour déplacer des quantités substantielles d'eau

Citations (3)

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Publication number Priority date Publication date Assignee Title
WO2000014917A2 (fr) * 1998-09-04 2000-03-16 Nokia Networks Oy Mise en oeuvre d'une liaison a multiplexage optique par repartition en longueur d'onde
US6115173A (en) * 1997-12-11 2000-09-05 Kdd Corporation Optical amplifying transmission system and optical amplifier
US20030039006A1 (en) * 2001-07-20 2003-02-27 Fabrizio Carbone Wavelength division multiplexing optical transmission system using a spectral inversion device

Family Cites Families (1)

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Publication number Priority date Publication date Assignee Title
CA2177874C (fr) * 1995-06-12 2000-06-20 At&T Ipm Corp. Systeme de communication multicanal a fibres optiques

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6115173A (en) * 1997-12-11 2000-09-05 Kdd Corporation Optical amplifying transmission system and optical amplifier
WO2000014917A2 (fr) * 1998-09-04 2000-03-16 Nokia Networks Oy Mise en oeuvre d'une liaison a multiplexage optique par repartition en longueur d'onde
US20030039006A1 (en) * 2001-07-20 2003-02-27 Fabrizio Carbone Wavelength division multiplexing optical transmission system using a spectral inversion device

Non-Patent Citations (1)

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Title
LACEV J P R ET AL: "FOUR-CHANNEL WDM OPTICAL PHASE CONHUGATOR USING FOUR-WAVE MIXING INA SINGLE SEMICONDUCTOR OPTICAL AMPLIFIER", ELECTRONICS LETTERS, IEE STEVENAGE, GB, vol. 31, no. 9, 27 April 1995 (1995-04-27), pages 743 - 744, XP000517801, ISSN: 0013-5194 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008087490A3 (fr) * 2007-01-18 2011-03-03 Kleysen, Hubert, T. Procédé et appareil pour déplacer des quantités substantielles d'eau

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