AU665802B2 - System for transmitting digital data over an optical link using optical amplifier repeaters - Google Patents
System for transmitting digital data over an optical link using optical amplifier repeaters Download PDFInfo
- Publication number
- AU665802B2 AU665802B2 AU33729/93A AU3372993A AU665802B2 AU 665802 B2 AU665802 B2 AU 665802B2 AU 33729/93 A AU33729/93 A AU 33729/93A AU 3372993 A AU3372993 A AU 3372993A AU 665802 B2 AU665802 B2 AU 665802B2
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- AU
- Australia
- Prior art keywords
- end equipment
- optical
- link
- error
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- 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.)
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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
- H04B10/293—Signal power control
- H04B10/2933—Signal power control considering the whole optical path
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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)
- Detection And Prevention Of Errors In Transmission (AREA)
- Dc Digital Transmission (AREA)
Description
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AUSTRALIA
Patents Act COMPLETE SPECIFICATION
(ORIGINAL)
~6$80 Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Societe Anonyme dite Alcatel Cit Actual Inventor(s): Stephane Morin Francois-Xavier Ollivier Jean-Luc Pamart Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA :i Invention Title: SYSTEM FOR TRANSMITTING DIGITAL DATA OVER AN OPTICAL LINK USING OPTICAL AMPLIFIER REPEATERS Our Ref 319884 POF Code: 1501/76619 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): -1- 6006 1
F
SYSTEM FOR TRANSMITTING DIGITAL DATA OVER AN OPTICAL LINK USING OPTICAL AMPLIFIER REPEATERS T i i Pq tip!~ The present invention concerns the transmission of digital data, especially over long distances, on an optical link.
It is known to provide at regular intervals on a link for transmitting data, especially over long distances, intermediate equipments for amplifying the signals conveying the data to compensate the attenuation that they undergo by virtue of their transmission over the link.
In the case of transmission of analog data over an electrical link it is known to use intermediate equipments known as repeaters using electronic amplifiers.
Likewise, in the case of transmission of digital data over an electrical link it is known to use intermediate equipments known as regenerators which not only amplify said signals but, given the digital nature of the data, regenerate the data as accurately as i possible.
25 In the case of transmission of digital data over an optical link it is known to use regenerator equipments to process the signals obtained after optical-to-electrical conversion of the optical signals transimitted on the fiber.
However, since the introduction of optical amplifiers such as doped fiber amplifiers or semiconductor optical amplifiers, for example, which are able to amplify optical signals directly, it has become possible to use such amplifiers as intermediate equipments or repeaters.
CU7 0J r pp 2 Although they amplify the incoming signals, the electronic or optical amplifiers introduce noise and it V is necessary to consider the energy balance of the combination of a link and its amplifier repeaters. From this -oint of view an optical link equipped with optical amplifier repeaters behaves in the same way as an electrical link equipped with electronic amplifiers.
The theory of transmitting analog data over an electrical link with electronic amplifier repeaters shows that, assuming equidistant identical repeaters each compensating exactly the attenuation introduced by the i preceding line section, in other words assuming unity gain "steps" (a step being defined as a repeater and the line section preceding it), there is a partic.J r relationship between the signal/noise ratio at the receiving end of the link and certain characteristic parameters of the system, including parameters characteristic of the link, such as the number of steps and their length (increasing the number of steps and likewise increasing the step length reduces the signal/noise ratio, all other things being equal).
Digital data transmission theory shows that the error rate at the receiving end, that is the ratio between the number of invalid bits after the decision operation effected at the receiving end of any such system to enable the reconstitution of said data and the total number of bits received is related to the signal/noise ratio prior to said decision operation, assuming a Gaussian distribution of the noise.
Given these assumptions, and allowing also for the noise contributed by the components of the receiving end equipment on the input side of the equipment carrying out said decision operation, there is in a system for transmitting digital data over an optical link using optical amplifier repeaters a particular relationship
F'
ii 3 between the error rate at the receiving end and certain characteristic parameters of the system including characteristic parameters of the link such as the number of steps and the length of the steps (increasing the number of steps and likewise increasing their length increases the error rate, all other things being equal).
An object of the invention is to improve the error rate at the receiving end of a system for transmitting digital data over an optical link using optical amplifier repeaters for a given rating of the system, that is to say for specific values of said characteristic parameters, compared with the error rate that would result, given the same parameter values, from the particular relationship mentioned above, and further to enable, for a given error rate at the receiving end, a the particular relationship mentioned above would y Ild an error rate greater than said given error rate.
A downgraded rating would result from creasing the number of steps, for example, in order t extend said link beyond the length for which id particular relationship and the same value of the other characteristic parameters entering to said relationship would yield said given error ra and/or increasing the length of the steps in orde to reduce the number of A repeaters relative to the ominal number for which said particular relationship nd the same values of the other characteristic param ers entering into said relationship would yield said ven error rate.
SUMMARY OF THE VENTION The p sent invention consists in a system for transmit ng digital data over an optical link comprising a sen end equipment, a receive-end equipment and one or mo optical amplifier repeaters wherein said send-end Wxe~eirqf/en
I-
-3a downgraded design or performance rating of the system, that is one for which the particular relationship mentioned above would yield an error rate greater than said given error rate.
A downgraded performance rating would result from increasing the number of steps, for example, in order to extend said link beyond the length for which said particular relationship and the same values of the other characteristic parameters entering into said relationship would yield said given error rate, and/or increasing the length of the steps in order to reduce the number of repeaters relative to the nominal number for which said particular relationship and the same values of the other characteristic parameters entering into said relationship would yield said given error rate.
The present invention provides a system for transmitting digital data over an optical link including a send-end equipment, a receive-end equipment and one or more optical amplifier repeaters wherein said send-end equipment includes error correcting encoding means and said receive-end equipment includes error correcting decoding means.
A preferred embodiment of the present invention will now be described with reference to the accompanying drawings wherein:lt C:kWINWORDWARIEGA1NODEL3729C.DOC t 4 decoding means.
Other objects and features of resent invention will emerge from the f Ing description of one embodiment of the ntion given with reference to the I appended ngs.
Figure 1 is a block diagram of a transmission system in accordance with the invention.
Figure 2 is a diagram showing in the case of one example of application of the present invention curves showing the error rate at the receiving end as a function of the level at the receiving end for different lengths Iof unity gain step, respectively before and after error correcting decoding.
I DETAILED DESCriPTION OF THE INVENTI3 The optical transmission system shown in the drawing comprises a send-end equipment 1, a receive-end equipment 2 and one or more optical amplifier repeaters.
The drawing shows a single repeater 3.
The send-end equipment 1 comprises error corrector encoding means 4 which receive digital data IE to be transmitted.
The error corrector encoding means use an error correcting code such as a block linear code like the B.C.H. (Bose Chaudhuri-Hocquenghem) or Reed-Solomon code or a convolutional c-de or a concatenation of several such codes, identical or otherwise, descriptions of these 3 codes being given in the literature.
The send-end equipment 1 further comprises an optical sender 5 which receives the data IEC from the error corrector encoding means and provides an optical signal SE transmitted over the optical link 6. The optical sender 5 includes an electro-optic transducer and optionally means for formatting the digital data to be I 1: transmitted (obtained in this instance from the error corrector encoding means) in a form suitable for transmission over an optical link.
The repeaters 3 may be doped fiber optical amplifiers or semiconductor optical amplifiers, for example.
The receive-end equipment 3 includes an optical filter 7 adapted to reject the optical noise generated by the optical amplifiers in order to increase the signal/noise ratio.
j The optical signal SR from the output of this optical filter is applied to an optical receiver 8 which supplies digital data IRC to error corrector decoding means 9 for the code used by the error corrector encoding means 4. The optical receiver 8 includes an optoelectronic transducer, decision means and optionally means for converting the format in which the digital data d was transmitted over the optical link to its original format.
As mentioned above, the theory of systems for transmitting analog data over a link equipped with electronic amplifier repeaters shows that the signal/noise ratio at the receiving end of the link, given the assumptions explained above, is expressed in logarithmic form by successively subtracting at the send level of the system a plurality of terms: a section, term representing the attenuation per line section, a term representing the noise level introduced by each repeater, a term dependent on the number of repeaters, specifically through the intermediary of the logarithmic function (see for example "Syst~mes de T616communications Bases de transmission" ("Telecommunication Systems Transmission Basics") P.G. FONTOLLIET Collection I 6 Technique et Scientifique des T616communicaticns DUNOD) and non-negligible non-linear effects generated in the transmission medium, which are optical fibers in this instance, a term dependent on these non-linear effects, per line section.
The theory of digital data transmission systems further shows that the error rate E at the receiving end is, given the above assumption, related to the signal/noise ratio prior to the decision process by the complementary integral Gauqs function (see the reference work cited above).
In the present context the signal/noise ratio prior Sto the decision process differs from the signal/noise ratio at the receive end of the link because the signal/noise ratio prior to the decision process also includes the noise contributed by components of the optical receiver on the input side of said decision operation.
The error rate E' at the receiving end for a system such as that shown in the drawing is additionally related to the error rate E mentioned above by an equation of the type: 1 n i C Ei n-i n i=t+l n in which and are parameters defining the error corrector code used, denoting the length of the code word and denoting the number of errors that can be corrected per code word (see for example "Codes Correcteurs Th6orie et Applications" ("Corrector Codes Theory and Applications") A. Poli, L. Huguet, MASSON Logique math6matiques informatique).
As mentioned above, the present invention allows a downgraded rating of the system for a given error rate 1 that is a rating yielding an error rate A downgraded rating may result, for example, from: increasing the number of steps, increasing the step length, increasing the level of noise introduced by each repeater, increasing the attenuation per unit length characterizing the transmission medium, degrading the performance of the optical sender, and so reducing the level of the signal at the send (and receive) ends of the link, degrading the performance of the optical receiver, for example reducing the sensitivity of the opto-electronic transducer, and so degrading the 1i: 15 signal/noise ratio prior to the decision process, increasing non-linear effects in the transmission op *0 medium, combinations of the above.
For a given rating of the system, the present S 20 invention also makes it possible to improve the operating margin relative to minimal performance constraints of the system, this margin enabling absorption of fluctuations
II
or degradation of the optimum operating point of the system caused by aging of components or changing environment conditions (temperature, electromagnetic, etc), for example.
il The figure 2 diagram shows curves showing the error rate at the receive end respectively before error corrector decoding and after error corrector decoding as a function of the level in dBm at the receiving end for various unity gain step lengths (in this example five lengths pl through p5 in decreasing order) on a link of given length.
The curves showing the error rate prior to error corrector decoding are drawn in dashed line and those
N
f 1 8 representing the error rate after error corrector decoding are drawn in full line. Note in each case that for a given step length the error rate decreases as the receive level increases and that for a given receive level the error rate decreases as the step length decreases.
Note also that for a given receive level and step length the error rate e after error correcter decoding is less than the error rate E' before error corrector decoding within the error correcting capacity limits of the error correcting code employed.
0 04 *0 0 u i. i-.i _i i I
Claims (7)
1. System for transmitting digital data over an optical link including a send-end equipment, a receive-end equipment and one or more optical amplifier repeaters wherein said send-end equipment includes error correcting encoding means and said receive-end equipment includes error correcting decoding means.
2. System according to claim 1 wherein said error correcting encoding and decoding means enable, for a given error rate at the receiving end at the output of said error correcting decoding means, a downgraded performance rating of the system, being a rating such that a characteristic parameter of the system yields an error rate greater than said given error rate.
3. System according to claim 2 wherein said downgraded rating is the result of increasing the number of unity gain steps of said link.
4. System according to claim 2 wherein said downgraded rating is the result of increasing the unity gain step length of said link.
System according to claim 1 wherein said error correcting encoding and Ii Sdecoding means obtain, for a given performance rating of the system, an d in improvement in the operating margin compared to minimal performance constraints of the system.
6. A system for transmitting digital data over an optical link substantially as DATED: 1 November, 1995. PHILLIPS ORMONDE FITZPATRICK Attorneys for: SOCIETE ANONYME DITE ALCATEL CIT MJP C:\W!NWORDMARIE GABNODEL\33729C.DOC
7 ABSTRACT OF THE DISCLOSURE optical link comprises a send-end equipment, a receive- end equipment and one or more optical amplifier repeaters. The send-end equipment comprises error corrector encoding means and said receive-end equipment comprises error corrector decoding means. jI I ol 'yj
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9202416 | 1992-02-28 | ||
| FR9202416A FR2688109B1 (en) | 1992-02-28 | 1992-02-28 | SYSTEM FOR TRANSMITTING DIGITAL INFORMATION ON AN OPTICAL LINK WITH REPEATERS WITH OPTICAL AMPLIFIERS. |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| AU3372993A AU3372993A (en) | 1993-09-02 |
| AU665802B2 true AU665802B2 (en) | 1996-01-18 |
Family
ID=9427205
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU33729/93A Ceased AU665802B2 (en) | 1992-02-28 | 1993-02-24 | System for transmitting digital data over an optical link using optical amplifier repeaters |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0558400A1 (en) |
| JP (1) | JPH066307A (en) |
| AU (1) | AU665802B2 (en) |
| CA (1) | CA2090292A1 (en) |
| FR (1) | FR2688109B1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5320011B2 (en) * | 2008-10-10 | 2013-10-23 | 日本電気通信システム株式会社 | Optical signal receiver, optical transmission device, and optical signal abnormality detection method |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1991004530A1 (en) * | 1989-09-12 | 1991-04-04 | Tandem Computers Incorporated | Error detection for fiber distributed interfaced optic link |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62166630A (en) * | 1986-01-20 | 1987-07-23 | Nippon Telegr & Teleph Corp <Ntt> | Binary balanced transmitting system having error correcting function |
| JPH0630471B2 (en) * | 1987-05-27 | 1994-04-20 | 三菱電機株式会社 | Optical repeater for star coupler |
| JPH01258531A (en) * | 1988-04-08 | 1989-10-16 | Kokusai Denshin Denwa Co Ltd <Kdd> | Optical repeater supervising system |
| JPH01268233A (en) * | 1988-04-19 | 1989-10-25 | Hitachi Ltd | Method for parallely transmitting light |
| JPH024036A (en) * | 1988-06-21 | 1990-01-09 | Canon Inc | Optical beam communication system |
| JPH0271626A (en) * | 1988-09-07 | 1990-03-12 | Hitachi Ltd | Optical space transmission equipment |
| JPH02155323A (en) * | 1988-12-08 | 1990-06-14 | Nec Corp | Supervisory system for optical repeater |
-
1992
- 1992-02-28 FR FR9202416A patent/FR2688109B1/en not_active Expired - Fee Related
-
1993
- 1993-02-23 EP EP93400461A patent/EP0558400A1/en not_active Withdrawn
- 1993-02-24 CA CA 2090292 patent/CA2090292A1/en not_active Abandoned
- 1993-02-24 AU AU33729/93A patent/AU665802B2/en not_active Ceased
- 1993-02-26 JP JP5038990A patent/JPH066307A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1991004530A1 (en) * | 1989-09-12 | 1991-04-04 | Tandem Computers Incorporated | Error detection for fiber distributed interfaced optic link |
| US5068854A (en) * | 1989-09-12 | 1991-11-26 | Cupertino, California U.S.A. | Error detection for fiber distributed interfaced optic link |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2688109B1 (en) | 1994-12-30 |
| CA2090292A1 (en) | 1993-08-29 |
| FR2688109A1 (en) | 1993-09-03 |
| AU3372993A (en) | 1993-09-02 |
| JPH066307A (en) | 1994-01-14 |
| EP0558400A1 (en) | 1993-09-01 |
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