WO2001019003A2 - Signaux comprimes positivement dans des systemes de communication optique - Google Patents

Signaux comprimes positivement dans des systemes de communication optique Download PDF

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Publication number
WO2001019003A2
WO2001019003A2 PCT/US2000/023314 US0023314W WO0119003A2 WO 2001019003 A2 WO2001019003 A2 WO 2001019003A2 US 0023314 W US0023314 W US 0023314W WO 0119003 A2 WO0119003 A2 WO 0119003A2
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WO
WIPO (PCT)
Prior art keywords
link
dispersion
transmitter
sum
laser
Prior art date
Application number
PCT/US2000/023314
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English (en)
Other versions
WO2001019003A3 (fr
Inventor
Jan Conradi
Roudas Ioannis
Manish Sharma
Original Assignee
Corning Incorporated
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 Corning Incorporated filed Critical Corning Incorporated
Priority to EP00986183A priority Critical patent/EP1219049A2/fr
Priority to MXPA02002476A priority patent/MXPA02002476A/es
Priority to JP2001522704A priority patent/JP2003511877A/ja
Priority to AU22465/01A priority patent/AU2246501A/en
Priority to CA002384431A priority patent/CA2384431A1/fr
Publication of WO2001019003A2 publication Critical patent/WO2001019003A2/fr
Publication of WO2001019003A3 publication Critical patent/WO2001019003A3/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
    • H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
    • H04B10/25137—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion using pulse shaping at the transmitter, e.g. pre-chirping or dispersion supported transmission [DST]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2210/00—Indexing scheme relating to optical transmission systems
    • H04B2210/25—Distortion or dispersion compensation
    • H04B2210/254—Distortion or dispersion compensation before the transmission line, i.e. pre-compensation

Definitions

  • the present invention relates generally to an optical waveguide fiber communications system, and particularly to such a communication system comprising negative dispersion waveguide fiber and a source of positively chirped signals.
  • Cost is a very important consideration in intra-city links, where the density of nodes is high.
  • a promising strategy is one that involves matching system components in such a way that a particular property of one component compensates a deficiency in another component.
  • the component matching strategy is one in which a given component is designed to allow another component to operate more efficiently or effectively.
  • Such compensation schemes have been effective, for example, in reducing dispersion penalty by adding a dispersion compensating module to the end of a communications link, thereby recovering a desired signal to noise ratio or signal pulse shape.
  • Another example of effective compensation is the use of large effective area waveguide fiber in communications systems in which non-linear effects are a major source of signal degradation.
  • the positive chirp that results from directly modulating a laser for example, a distributed feedback (DFB) semiconductor laser
  • a distributed feedback (DFB) semiconductor laser can be offset by using optical waveguide fiber having negative total dispersion over a desired range of operating wavelengths.
  • the effect of the negative dispersion fiber does not depend upon the type of light source or modulation scheme.
  • the beneficial effect is achieved when the negative dispersion fiber is used in conjunction with a signal having a positive chirp.
  • Matching a waveguide fiber to a positively chirped DFB semiconductor laser is a cost effective combination, especially because, in addition to being low in cost, the DFB semiconductor laser has relatively high power output and good longevity.
  • direct modulation is simpler and less expensive than external modulation schemes.
  • Chromatic dispersion arises because different frequency components of a pulse or signal travel with different group velocities in the fiber. Chromatic dispersion is characterized by the so called dispersion parameter D which is expressed in units of ps/nm-km. The value of the dispersion parameter D is the sum of two terms, one arising from the fiber material and the other from geometric characteristics of the waveguide.
  • the product of the length of a waveguide fiber and the dispersion parameter D (including material and waveguide contributions) will be subsequently called the dispersion product.
  • a link may be made of waveguide fiber within which the chromatic dispersion changes along the fiber length.
  • the sum of dispersion products for a fiber length is the algebraic addition of the individual dispersion products associated with the individual fiber lengths. In symbols, the sum of dispersion products is ⁇ Dj x U where, Dj is the dispersion parameter over the length U and the total length of the fiber is ⁇ j L,.
  • the dispersion parameter of a waveguide fiber is, by convention, positive when shorter wavelength light propagates at a higher speed than light of longer wavelength. The converse is the definition of negative dispersion waveguide fiber.
  • a waveguide fiber telecommunications link is made up of a transmitter of light signals, a receiver of light signals, and a length of waveguide fiber having respective ends optically coupled to the transmitter and receiver to propagate light signals therebetween.
  • a link can include additional optical components such as optical amplifiers, optical attenuators, optical switches, optical filters, or multiplexing or demultiplexing devices.
  • One may denote a group of inter-connected links as a telecommunications system.
  • - Extinction ratio is defined as the ratio of the transmitted power Pi when the transmitter is in the on state (a one bit is transmitted) to the transmitted power P 0 when the transmitter is in the off state (a zero bit is transmitted).
  • a positively chirped signal source produces pulses in which the carrier frequency varies along the pulse time axis. That is, the frequency of the electric field of the output pulse is red or blue shifted compared to the frequency of the laser at the threshold.
  • a conventional single- electrode DFB semiconductor laser produces pulses with an average blue shift, herein defined as positive chirp.
  • the chirp in a signal for example a signal from a directly modulated DFB laser, can be expressed approximately as a combination of adiabatic chirp and transient chirp.
  • Adiabatic chirp is proportional to the output power of the signal.
  • Transient chirp is proportional to the derivative of the output power of the signal and so is present only in the time periods when the signal power is in transition between a 0 and a 1 (or a 1 to a 0).
  • Dispersion power penalty of a link is the reduction of the link power budget due to dispersion-induced distortion of the signal.
  • the dispersion penalty is expressed as eye closure penalty.
  • the eye diagram is known in the art as the eye shaped opening formed when adjacent signal pulses begin to overlap. As overlap increases, the eye is said to close. This is a convenient way to refer to the reduction in signal to noise ratio due to pulse dispersion.
  • Gain compression factor also known as the nonlinear gain parameter, refers to a semiconductor laser and is a proportionality constant that relates semiconductor laser material optical gain of the active region of the laser to the number of photons in the active region.
  • G f( ⁇ P)
  • G the gain of the laser
  • ⁇ the gain compression factor
  • P number of photons in the active region (which is directly related to the laser output power)
  • f a function. See Fiber Optic Communications Systems 2 nd Edition, Agrawal, page 113. Summary of the invention
  • One aspect of the present invention is a telecommunications link that includes an optical signal transmitter, an optical signal receiver, and a length of optical waveguide fiber optically connected between the transmitter and receiver to carry the light signals from the transmitter to the receiver. At least a portion of the waveguide fiber of the telecommunications link has negative dispersion and the optical signals of the transmitter are positively chirped. In addition, the signal chirp is predominately adiabatic.
  • the signal source is a directly modulated laser included in the transmitter.
  • the laser is a directly modulated DFB semiconductor laser.
  • the positively chirped signal pulses originate in a continuous wave source of optical power that is externally modulated.
  • Adiabatic laser chirp is characterized by a relatively high gain compression factor, e.g., one in the range of 4 x 10 "23 m 3 to 30 x 10 "23 m 3 .
  • adiabatic chirp is favored in laser operating conditions in which the extinction ratio is not greater than about 20 dB. Extinction ratios which fall in the range of 5 dB to 11.5 dB are preferred.
  • An extinction ratio as high as 20 dB is contemplated in communications links that include forward error correction.
  • Forward error correction is a scheme by which bits that become corrupted during data transmission can be corrected. This requires electronics to encode the data before transmission and to decode the data after reception. The forward error correction electronics is known in the art and need not be discussed further here.
  • Fig. 1 is a theoretical graph of the optical output power versus time for a directly modulated adiabatic chirp dominated DFB semiconductor laser operating at the OC-48 (2.5 Gb/s) rate.
  • Fig. 2 is a theoretical graph of the optical output power versus time for a directly modulated transient chirp dominated DFB semiconductor laser operating at the OC-48 (2.5 Gb/s) rate.
  • Fig. 3 is a theoretical graph of the optical frequency deviation versus time for a directly modulated adiabatic chirp dominated DFB semiconductor laser operating at the OC-48 (2.5 Gb/s) rate.
  • Fig. 4 is a theoretical graph of the optical frequency deviation versus time for a directly modulated transient chirp dominated DFB semiconductor laser operating at the OC-48 (2.5 Gb/s) rate.
  • Fig. 5 is a theoretical graph of simulated eye closure penalty versus the dispersion product for a directly modulated adiabatic chirp dominated DFB semiconductor laser operating at the OC-48 (2.5 Gb/s) rate.
  • Fig. 6 is a theoretical graph of simulated eye closure penalty versus the dispersion product for a directly modulated transient chirp dominated DFB semiconductor laser operating at the OC-48 (2.5 Gb/s) rate.
  • Fig. 7 is a graph of Q versus dispersion product for a laser operated at an extinction ratio of 6.2 dB and the OC-48 (2.5Gb/s) rate.
  • Fig. 8 is a graph of Q versus dispersion product for a laser operated at an extinction ratio of 8.8 dB and the OC-48 (2.5Gb/s) rate.
  • Fig. 9 is a graph of Q versus dispersion product for a laser operated at an extinction ratio of 11.3 dB and the OC-48 (2.5Gb/s) rate.
  • Fig. 10 is a schematic drawing of an exemplary multi-channel optical communication link.
  • the invention comprises, in combination, a positively chirped laser in which the chirp is predominately adiabatic and an optical waveguide optical fiber having negative dispersion.
  • the term laser in this application is generally used to describe a source of optical power suitable for use in an optical waveguide link which is positively chirped and which can be directly modulated.
  • the invention includes any continuous wave source of optical power which is externally modulated and which exhibits positive chirp.
  • An example of a positively chirped laser is the distributed feedback semiconductor laser which is directly modulated.
  • Chirp can be characterized as adiabatic which means the chirp is proportional to the optical output power of the laser. In contrast, transient chirp is proportional to the rate of change of optical output power with time.
  • the chirp In the case of the directly modulated DFB lasers, the chirp is predominantly adiabatic when the laser is always operated well above threshold with low extinction ratios (e.g. 6dB). However with present technology the chirp becomes predominantly transient when the laser is operated closer to threshold, where the extinction ratios becomes much higher (e.g. 12dB).
  • the exact extinction ratio or drive condition under which a laser's chirp switches from predominantly adiabatic to predominantly transient depends upon the exact parameters of the laser itself. It is contemplated that laser design parameters can be found that provide adiabatic chirp at an extinction ratio as high as 12 dB.
  • Figs. 1 and 3 The characteristics of a directly modulated laser exhibiting predominately adiabatic chirp are illustrated in Figs. 1 and 3.
  • a particular laser which is described by these figures is the directly modulated DFB semiconductor laser.
  • the figures are derived from the exemplary case in which the bit rate is 2.5 Gb/s, the OC-48 rate. It will be understood that the figures could be modified to describe a higher or lower bit rate. Also, it will be understood that the bit rate can be achieved by any of several means known in the art, including time or wavelength division multiplexing, the latter of which is shown in Fig. 10.
  • Fig. 1 is shown a sequence of digital 1's, segments 6 of the chart, and 0's, segments 2 of the chart.
  • the ringing 8 (the oscillation of the laser signal about a steady state value) of the 1's, and the ringing 4 of the 0's is seen to be small. This is to be compared to the 0's, 14, and 1 's, 16, of the transient chirp dominated laser sequence of laser signals shown in Fig. 2.
  • the ringing for example chart segments 18 and 20, is much larger for the transient chirp dominated laser output.
  • the optical frequency deviations of segments 10 of Fig. 3 as compared to the optical frequency deviations of segments 12 in Fig.
  • the frequency difference between 0's and 1 's in the adiabatic case is pronounced.
  • This difference in optical frequency is to be compared to that in Fig. 4 where segments 22 are frequency deviation for the signal 0's and segments 24 are frequency deviation for the signal 1 's.
  • the primary difference between the laser characterized by Figs. 1 and 3 and the laser characterized by Figs. 2 and 4, is that the gain compression factor, defined above, was 5 x 10 '23 m 3 for the former laser and 1 x 10 "23 m 3 for the latter laser.
  • Gain compression factor for a particular laser structure may be measured by using fitting techniques described, for example, in L. A. Coldren and S. W. Corzine, "Diode lasers and photonic integrated circuits", Wiley,
  • a system designer maintains extinction ratio as high as possible consistent with the desired system operating parameters.
  • the decrease in signal overshoot, the reduction in ringing amplitude and duration, and the marked difference in optical frequency between 0's and 1 's of the predominately adiabatic chirped laser provide a telecommunications link in which distance between signal regenerators is large in comparison to the case of a predominately transient chirped laser.
  • the improved performance of the laser having predominately adiabatic chirp carries over into link performance as can be seen in Fig. 5 where simulated eye closure penalty is charted versus accumulated waveguide fiber dispersion at 2.5 Gb/s. Acceptable eye closure penalty is preferred to be no more negative than -2 dB.
  • curve 26 of Fig. 5 shows an accumulated dispersion of -5000 ps/nm when eye closure penalty reaches -2 dB.
  • a typical dispersion shifted negative dispersion waveguide can have a total dispersion at 1550 nm of about -3.5 ps/(nm-km).
  • the link length traversed by the pulse, without electronic regeneration, before incurring a -2 dB eye closure penalty is about
  • Comparing curves 30 and 32 of Fig. 6 again shows the advantage of negative dispersion waveguide fiber in combination with a positively chirped laser.
  • the positive dispersion waveguide fiber of corresponding to curve 32 shows an acceptable accumulated dispersion of only about 1000 ps/nm, which yields a typical link length of about 285 km of a positive dispersion fiber with the same absolute value of dispersion parameter.
  • the use of a laser having predominantly adiabatic chirp in combination with a negative dispersion fiber increases unregenerated link length by about a factor of four.
  • a bit error rate of 10 "12 corresponds to a link Q value greater than or equal to 8.5 dB. In systems in which a higher bit error rate can be tolerated, Q values greater than or equal to 6 dB are acceptable. In systems which make use of forward error correction electronics a Q value greater than or equal to 3 dB is acceptable.
  • Curve 34 of Fig. 7 shows the performance of a link operating at 2.5 Gb/s, in terms of Q value versus accumulated dispersion, having an extinction ratio no greater than
  • the accumulated link dispersion is not less negative than -12000 ps/nm. Again assuming a total dispersion at 1550 nm of -3.5 ps/nm-km, one finds a corresponding link length of nearly 3500 km before electronic signal regeneration is needed. At the higher extinction ratio, a ratio no greater than about 9 dB, curve 38 of Fig. 8, also pertaining to a 2.5 Gb/s rate, the acceptable accumulated dispersion of a pulse propagating in a negative dispersion waveguide fiber is not less negative than -6000 ps/nm, corresponding to an unregenerated link length at 1550 nm of about 1700km. Curve 42 of Fig.
  • Example receivers suitable for use in the telecommunications links disclosed and described herein are Alcatel 1916 SDH, Receiver STM-
  • Example transmitters suitable for use in the telecommunications links disclosed and described herein are D2570, D2526, D2555 Wavelength-Selected Laser 2000, Lucent
  • link length can be reduced to allow higher waveguide fiber total dispersion. Also link length can be increased in systems that can tolerate a higher value of Q.
  • Curve 36 of Fig. 7, curve 40 of Fig. 8, and curve 44 of Fig. 9 were generated using links essentially identical to those of links used to generate corresponding curves 34, 38, and 42, except that waveguide fiber having positive total dispersion was used.
  • the advantage of using negative dispersion waveguide fiber in combination with a laser of predominantly adiabatic chirp is evident. The advantage becomes more pronounced as extinction ratio of the laser is decreased.
  • the link includes a plurality 46 of sources of light pulse signals, for example, a plurality of directly modulated distributed feedback semiconductor lasers, having positive, predominately adiabatic chirp and operating in a wavelength division multiplexing mode.
  • the directly modulated DFB laser is a simple, low cost, and reliable signal source.
  • the plurality 46 of lasers are coupled into waveguide 52 via optical multiplexer 48.
  • Optical amplifiers 50 are inserted into the waveguide fiber path at pre-selected intervals to maintain a desired signal amplitude.
  • the signal then passes through optical demultiplexer 54 which separates the wavelengths and delivers a particular wavelength to one of the plurality of receivers 56.
  • At least a portion of the waveguide fiber 52 linking the transmitters and receivers has negative chromatic dispersion to compress the positively chirped laser pulses. Spacing between transmitters and receivers can be a few kilometers, or tens of kilometers, or hundreds of kilometers.
  • the laser is operated at an extinction ratio of 5 dB to 10 dB, with 20 dB extinction ratios being workable for lasers having the required chirp characteristic at a higher pulse power.
  • the link can support 2.5 Gb/s or 10 Gb/s data rates. No electronic regeneration is required.

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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)
  • Semiconductor Lasers (AREA)

Abstract

L'invention concerne une liaison de télécommunications comportant des impulsions de signal optique comprimées positivement qui se propagent dans une fibre de guide d'ondes optiques, au moins une partie de ces impulsions étant caractérisées par une dispersion chromatique négative. Une forme de réalisation de l'invention est une source laser à semi-conducteurs combinée à une fibre de guide d'ondes optiques à dispersion négative. La source d'impulsions de signal comprimées est sélectionnée de manière à présenter principalement une compression adiabatique, comme le montre, dans le cas d'un laser à rétroaction répartie, un facteur de compression compris entre 4 x 10-23m3 et 30 x 10-23m3. Les problèmes de fermeture de l'oeil et le taux d'erreurs sur les bits sont maintenus à un niveau bas pour des longueurs de liaison présentant un produit de paramètre de dispersion cumulatif fois distance de l'ordre de milliers de ps/nm. Le taux d'extinction de laser optimal se situe dans la plage de 5 à 10 dB, même si des taux d'extinction de 20 dB sont envisagés.
PCT/US2000/023314 1999-09-07 2000-08-24 Signaux comprimes positivement dans des systemes de communication optique WO2001019003A2 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
EP00986183A EP1219049A2 (fr) 1999-09-07 2000-08-24 Signaux comprimes positivement dans des systemes de communication optique
MXPA02002476A MXPA02002476A (es) 1999-09-07 2000-08-24 Senales con chirrido positivo en sistemas opticos de comunicacion.
JP2001522704A JP2003511877A (ja) 1999-09-07 2000-08-24 正のチャープ化信号による光通信システム
AU22465/01A AU2246501A (en) 1999-09-07 2000-08-24 Positively chirped signals in optical communication systems
CA002384431A CA2384431A1 (fr) 1999-09-07 2000-08-24 Signaux comprimes positivement dans des systemes de communication optique

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
US15262699P 1999-09-07 1999-09-07
US60/152,626 1999-09-07
US17839400P 2000-01-27 2000-01-27
US60/178,394 2000-01-27
US18640700P 2000-03-02 2000-03-02
US60/186,407 2000-03-02
US18679600P 2000-03-03 2000-03-03
US60/186,796 2000-03-03

Publications (2)

Publication Number Publication Date
WO2001019003A2 true WO2001019003A2 (fr) 2001-03-15
WO2001019003A3 WO2001019003A3 (fr) 2001-09-20

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PCT/US2000/023314 WO2001019003A2 (fr) 1999-09-07 2000-08-24 Signaux comprimes positivement dans des systemes de communication optique

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EP (1) EP1219049A2 (fr)
JP (1) JP2003511877A (fr)
AU (1) AU2246501A (fr)
CA (1) CA2384431A1 (fr)
MX (1) MXPA02002476A (fr)
WO (1) WO2001019003A2 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109196739A (zh) * 2016-06-30 2019-01-11 华为技术有限公司 啁啾补偿激光器及其驱动方法
CN111949468A (zh) * 2020-09-18 2020-11-17 苏州浪潮智能科技有限公司 一种双端口盘管理方法、装置、终端及存储介质

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013034134A (ja) * 2011-08-02 2013-02-14 Nippon Telegr & Teleph Corp <Ntt> 光アクセスシステム
NO2762823T3 (fr) 2013-01-30 2017-12-23

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US5774485A (en) * 1995-09-20 1998-06-30 Siemens Aktiengesellschaft Wavelength-tunable laser device
US5798856A (en) * 1992-02-03 1998-08-25 Kokusai Denshin Denwa Kabushiki Kaisha Optical pulse generator
US5877881A (en) * 1996-04-19 1999-03-02 Fujitsu Ltd. Optical transmission system
US5909297A (en) * 1994-08-02 1999-06-01 Fujitsu Limited Drift compensating circuit for optical modulators in an optical system
US6064682A (en) * 1996-07-26 2000-05-16 Wivenhoe Technology Limited Delaying of laser pulses

Patent Citations (5)

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Publication number Priority date Publication date Assignee Title
US5798856A (en) * 1992-02-03 1998-08-25 Kokusai Denshin Denwa Kabushiki Kaisha Optical pulse generator
US5909297A (en) * 1994-08-02 1999-06-01 Fujitsu Limited Drift compensating circuit for optical modulators in an optical system
US5774485A (en) * 1995-09-20 1998-06-30 Siemens Aktiengesellschaft Wavelength-tunable laser device
US5877881A (en) * 1996-04-19 1999-03-02 Fujitsu Ltd. Optical transmission system
US6064682A (en) * 1996-07-26 2000-05-16 Wivenhoe Technology Limited Delaying of laser pulses

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109196739A (zh) * 2016-06-30 2019-01-11 华为技术有限公司 啁啾补偿激光器及其驱动方法
CN109196739B (zh) * 2016-06-30 2020-04-21 华为技术有限公司 啁啾补偿激光器及其驱动方法
CN111949468A (zh) * 2020-09-18 2020-11-17 苏州浪潮智能科技有限公司 一种双端口盘管理方法、装置、终端及存储介质
CN111949468B (zh) * 2020-09-18 2023-07-18 苏州浪潮智能科技有限公司 一种双端口盘管理方法、装置、终端及存储介质

Also Published As

Publication number Publication date
JP2003511877A (ja) 2003-03-25
CA2384431A1 (fr) 2001-03-15
EP1219049A2 (fr) 2002-07-03
WO2001019003A3 (fr) 2001-09-20
AU2246501A (en) 2001-04-10
MXPA02002476A (es) 2002-08-20

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