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WO2003052464A2 - Systeme et procede optimisant les transmissions dans des reseaux distribues a amplificateurs raman fonctionnant en saturation - Google Patents

Systeme et procede optimisant les transmissions dans des reseaux distribues a amplificateurs raman fonctionnant en saturation Download PDF

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Publication number
WO2003052464A2
WO2003052464A2 PCT/US2002/039751 US0239751W WO03052464A2 WO 2003052464 A2 WO2003052464 A2 WO 2003052464A2 US 0239751 W US0239751 W US 0239751W WO 03052464 A2 WO03052464 A2 WO 03052464A2
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WO
WIPO (PCT)
Prior art keywords
optical fiber
optical
data signal
fiber spans
group
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.)
Ceased
Application number
PCT/US2002/039751
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English (en)
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WO2003052464A3 (fr
Inventor
Nandakumar Ramanujam
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.)
Broadwing LLC
Original Assignee
Broadwing LLC
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Filing date
Publication date
Application filed by Broadwing LLC filed Critical Broadwing LLC
Priority to AU2002353126A priority Critical patent/AU2002353126A1/en
Publication of WO2003052464A2 publication Critical patent/WO2003052464A2/fr
Publication of WO2003052464A3 publication Critical patent/WO2003052464A3/fr
Anticipated expiration legal-status Critical
Priority to US10/866,846 priority patent/US20050019039A1/en
Ceased 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
    • H04B10/29—Repeaters
    • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
    • H04B10/2912—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing
    • H04B10/2916—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing using Raman or Brillouin amplifiers

Definitions

  • the present invention relates generally to optical communications, and more particularly to a system and method for optimizing the transmission of optical signals in a distributed Raman amplified system.
  • DPA Distributed Raman amplification
  • a method for controlling the amplification of an optical data signal in an optical communication system having a plurality of optical fiber spans, each optical fiber span providing amplification to the optical data signal includes transmitting the optical data signal into a first optical fiber span at an input power level lower than a nominal power level. More than unity gain is provided to the optical data signal over each of at least a first group of the optical fiber spans such that the power level of the optical data signal after propagating through each of the plurality of optical fiber spans is higher than the nominal power level.
  • the amount of gain provided in each of the optical fiber spans in the first group is substantially the same.
  • the number of optical fiber spans in the first group is less than the total number of optical fiber spans.
  • unity gain is provided to the optical data signal over each of a second group of optical fiber spans different from the first group of optical fiber spans.
  • Fig. 1 is a block diagram of a long-haul fiber optic communication system consistent with the present invention.
  • Fig. 2 is a block diagram of an exemplary architecture for a WDM terminal consistent with the present invention.
  • Fig. 3 A shows the net gain for signals versus launch power for a unity gain system consistent with the present invention.
  • Fig. 3B shows the signal power versus transmission distance where the launch power is -10 dBm in a unity gain system consistent with the present invention.
  • Fig. 4 shows the affect on system performance (Q 2 ) for a range of launch powers (P ) in a unity gain system consistent with the present invention.
  • Fig. 5 shows the signal power versus transmission distance for multiple launch powers in a unity gain system consistent with the present invention.
  • Fig. 6 shows the signal power versus transmission distance for multiple launch powers in a unity gain system with adjusted steady-state powers consistent with the present invention.
  • Fig. 7 shows experimental simulation data for a range of launch powers used in three different optical communication system arrangements.
  • Fig. 1 is a block diagram of a long-haul fiber optic communication system consistent with the present invention.
  • the system includes a wavelength division multiplexer (WDM) terminal 10 and a WDM terminal 12.
  • the WDM terminals 10 and 12 include a number of optical communication transmitters 14a to 14z, which respectively transmit signals at optical communications wavelengths ⁇ a to ⁇ z, where z is an integer corresponding to the total number of wavelengths being transmitted.
  • the number z of optical communications wavelengths is between approximately 200 and 400, although other numbers of wavelengths may be used.
  • the number of wavelengths maybe 256, 320 or 384.
  • the optical communications wavelengths are multiplexed into a multiplexed optical data signal by a multiplexer 16 in WDM terminal 10, which is amplified in the transmission fiber with pump power provided by a series of pump modules 20.
  • the multiplexed data signal is transmitted from one the WDM terminal 10 to the pump modules 20, between the pump modules 20, and from the pump modules 20 to the WDM terminal 12 via one or more transmission optical fibers 22.
  • the pump module 20 will also include transmission optical fiber.
  • the multiplexed data signal is then demultiplexed by demultiplexer 18 at the WDM terminal 12 into optical communications wavelengths ⁇ a to ⁇ z .
  • the demultiplexed optical communications wavelengths ⁇ a to ⁇ z are received by respective optical communications receivers 24a to 24z.
  • each of the WDM terminals 10 and 12 preferably include both transmission and reception components to provide bidirectional transmission.
  • the amplification architecture in the pump modules 20 provide pump light into optical fibers 22 and amplify the data signals traveling in the optical fibers 22.
  • the gain profile for Raman amplification has a typical bandwidth of 20-30 nm for a single pump wavelength.
  • WDM wavelength division multiplexed
  • This 20-30 nm bandwidth is too narrow.
  • Raman amplification employing multiple pump wavelengths over a broad wavelength range may be used in WDM optical communication applications.
  • pump wavelengths and pump power levels are selected to result in a constant or flat gain over the desired broad wavelength range.
  • Fig. 2 is a block diagram of an exemplary architecture for a WDM terminal consistent with the present invention. In the example of Fig. 2, the terminals are connected to undersea optical communication systems, although those skilled in the art will readily appreciate that the present invention is equally applicable to devices which operate in terrestrial communication systems.
  • long reach transmitters/receivers (LRTRs) 30 convert terrestrial signals into an optical format for long haul transmission, convert the undersea optical signal back into its original terrestrial format and provide forward error correction.
  • the number of LRTRs 30 in each terminal will vary with the number of channels supported by the optical communication system, but may easily reach 100, 200, 300 or more per terminal.
  • Each LRTR 30 can include a laser and a modulator, for example, and can be provided on one or more line cards which are physically mounted in shelves as described below.
  • a WDM and optical conditioning unit 32 multiplexes and amplifies the optical signals in preparation for their transmission over a cable 34 and, in the opposite direction, demultiplexes optical signals received from the cable 34. Enclosed within the cable 34 are the optical fibers 22.
  • Link monitor equipment 36 monitors the optical signals and undersea equipment for proper operation.
  • Line current equipment 38 provides power to undersea line units.
  • a network management system (NMS) 40 controls the operation of the other components in the WDM terminal, as well as sending commands to the line units via the link monitor equipment 36, and is comiected to the other components in the WDM terminal via a backplane 42.
  • Fig. 3 A shows the net gain for signals versus launch power (P L ) for a unity gain system.
  • the unity gain system can be implemented by adjusting the pump powers of the pump modules 20 in the fiber optic communication system.
  • the net gain is zero for the nominal launch power.
  • the nominal launch power of the optical signal in this unity gain system is approximately -10 dBm.
  • Fig. 3B shows the signal power (P(z)) versus transmission distance (z) at the nominal launch power of approximately -10 dBm in the unity gain system of Fig. 3A.
  • the signal power remains substantially constant.
  • Fig. 4 shows the effect on system performance (Q 2 ) for a range of launch powers (PL) at a unity gain condition.
  • the optical communication system maintains the power of the signal at substantially the same power as the launch power throughout the system.
  • the lower launch powers have poorer performance primarily as a result of greater linear penalties due to increased noise.
  • the higher launch powers have poorer performance primarily as a result of greater non-linear penalties.
  • the launch power that provides the optimal system performance can be identified by from the launch power providing the highest Q value.
  • altering the launch power affects the linear and non-linear penalties, which determine system performance and the quality of the transmitted optical signal, h general, increasing the launch power increases the optical to signal noise ratio (OSNR), which reduces linear noise.
  • OSNR optical to signal noise ratio
  • the increased launch power however, also increases the non-linearities.
  • lowering the launch power lowers the OSNR, which increases the amount of linear noise, but also reduces the amount of non-linearities.
  • Fig. 5 shows the signal power versus transmission distance for multiple launch powers in a unity gain system.
  • the unity gain system shown in Fig. 5 has a nominal launch power of approximately -10 dBm. If the launch power of the optical signal is increased over the nominal launch power, such as to -3 or -5 dBm, the net gain is -7 and -5 dB, respectively, as shown in Fig. 5. Because of the self-regulation due to the saturation effect, the output signal power is automatically adjusted to the nominal output power of approximately -10 dBm for each launch power. There is a limited range of launch powers, however, beyond which the required gain is not available to hold the output power constant.
  • a first section of pump modules 20 provides excess gain to the optical signal until a steady- state level is reached.
  • the steady-state power level which is substantially equal to the nominal launch power, is reached after approximately 4,200 km.
  • the remaining pump modules 20 provide unity gain as a result of the saturation effect.
  • a first section of pump modules 20 provides less than unity gain to the optical signal until the steady-state level is reached, and the remaining pump modules 20 provide unity gain.
  • the power evolution of the optical signal can be controlled by adjusting components in the system that have an effect on the power of the optical signal as it propagates. These components include, for example, the length of the system between WDM terminals, the span lengths of the optical fibers 22 between pump modules 20, the number of pump modules 20, and the losses in each span, as well as the launch power of the optical signal.
  • Fig. 6 shows the signal power versus transmission distance for multiple launch powers in a unity gain system with adjusted steady-state powers consistent with the present invention. As shown in Fig. 6, for launch powers greater than the nominal launch power, the steady-state power levels reached toward the end of the transmission are lower than the nominal output power. Conversely, for launch powers lower than the nominal launch power, the steady-state power levels reached toward the end of the transmission are higher than the nominal output power.
  • the lowered output power for the higher launch powers and the raised output power for the lower launch powers can be achieved by controlling the pump powers of the pump modules 20.
  • the pump powers of the pump modules 20 may be increased.
  • the increased pump power can be adjustable depending on the position of each pump module 20. More preferably, each pump module is configured to provide the same amount of pump power, with the amount provided being sufficient to raise the output power of the optical signal to be greater than the nominal output power.
  • the pump powers of the pump modules 20 may be decreased, either by adjusting the pump power depending on the position of each pump module 20 or configuring each pump module 20 to have the same amount of pump power sufficient to lower the output power of the optical signal to be lower than the nominal output power.
  • Fig. 7 shows experimental simulation data for a range of launch powers used in three different optical communication system arrangements.
  • the first arrangement is a unity gain system having a nominal power level of approximately 10 dBm.
  • the second arrangement is for an optical communication system configured for optimal transmission at 15 dBm.
  • the third arrangement is for an optical communication system optimized for each launch power.
  • the data shown in Fig. 7 show both the output power for each launch power in each arrangement, as well as the system performance (Q 2 ) for each launch power in each arrangement.
  • the best system performance is achieved where the optical communication system is optimized for launch powers between approximately -13 dBm and -17 dBm.
  • the output powers range between just below -9 dBm to just above -9 dBm.
  • the optimal transmission condition is one where the power evolves from less than the nominal power level, receives net excess gain, and reaches a steady-state power level that is greater than the nominal output power level.

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

Abstract

L'invention porte sur un système et un procédé de commande d'amplification d'un signal optique dans un système de télécommunications comprenant plusieurs segments de fibres optiques assurant chacun une amplification du signal. Ledit procédé consiste à injecter ledit signal dans un premier segment avec une puissance d'entrée inférieure au niveau nominal, puis à l'amplifier de plus d'un gain unitaire dans chacun des segments d'au moins un premier groupe de segments pour le porter à une puissance supérieure au niveau nominal.
PCT/US2002/039751 2001-12-13 2002-12-12 Systeme et procede optimisant les transmissions dans des reseaux distribues a amplificateurs raman fonctionnant en saturation Ceased WO2003052464A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2002353126A AU2002353126A1 (en) 2001-12-13 2002-12-12 Raman amplifiers operating in saturation
US10/866,846 US20050019039A1 (en) 2002-12-12 2004-06-14 System and method for optimized transmission in distributed Raman amplified systems operating in saturation

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US33916801P 2001-12-13 2001-12-13
US60/339,168 2001-12-13

Publications (2)

Publication Number Publication Date
WO2003052464A2 true WO2003052464A2 (fr) 2003-06-26
WO2003052464A3 WO2003052464A3 (fr) 2003-12-24

Family

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PCT/US2002/039751 Ceased WO2003052464A2 (fr) 2001-12-13 2002-12-12 Systeme et procede optimisant les transmissions dans des reseaux distribues a amplificateurs raman fonctionnant en saturation

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AU (1) AU2002353126A1 (fr)
WO (1) WO2003052464A2 (fr)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5058974A (en) * 1989-10-06 1991-10-22 At&T Bell Laboratories Distributed amplification for lightwave transmission system
EP1914849B1 (fr) * 1997-02-18 2011-06-29 Nippon Telegraph & Telephone Corporation Amplificateur optique et système de transmission utilisant cet amplificateur
US6038356A (en) * 1997-09-25 2000-03-14 Tyco Submarine Systems Ltd. Lightwave transmission system employing raman and rare-earth doped fiber amplification

Also Published As

Publication number Publication date
AU2002353126A1 (en) 2003-06-30
AU2002353126A8 (en) 2003-06-30
WO2003052464A3 (fr) 2003-12-24

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