WO1994016347A1 - Procede d'analyse de fibres et systeme de reflectometrie optique eloignee, a dimensions temporelles et a commutation electrique - Google Patents

Procede d'analyse de fibres et systeme de reflectometrie optique eloignee, a dimensions temporelles et a commutation electrique Download PDF

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Publication number
WO1994016347A1
WO1994016347A1 PCT/US1993/012684 US9312684W WO9416347A1 WO 1994016347 A1 WO1994016347 A1 WO 1994016347A1 US 9312684 W US9312684 W US 9312684W WO 9416347 A1 WO9416347 A1 WO 9416347A1
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WO
WIPO (PCT)
Prior art keywords
optical
line card
electrical signal
otdr
fiber
Prior art date
Application number
PCT/US1993/012684
Other languages
English (en)
Inventor
Elliot Eichen
Jagannath Chirravuri
Original Assignee
Gte Laboratories 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 Gte Laboratories Incorporated filed Critical Gte Laboratories Incorporated
Publication of WO1994016347A1 publication Critical patent/WO1994016347A1/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
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]

Definitions

  • the present invention relates generally to performing optical time domain reflectometry measurements on fiber optic telecommunications links and more particularly to automated systems for the same.
  • OTDR optical time domain reflectometry
  • An optical time domain reflectometry system is a sophisticated "optical radar" which can be used to observe and locate optical perturbations along the length of a fiber telecommunications link.
  • the system operates by sending a pulse of light from a laser down a fiber and monitoring the light scattered back in the direction of the transmitter with a photodetector.
  • the light source used for most commercial equipment is a high power (> 1 mW) semiconductor laser operating at 1.3 ⁇ m or 1.5 ⁇ m.
  • the light returned to the photodetector can be from discrete reflections such as a connector or a cleaved fiber, or can be due to backscatter in the fiber.
  • Return light scattering is an intrinsic function of all dielectric materials, and is caused by fluctuations in the density of the medium. When the average distance of these fluctuations is much smaller than the wavelength of light, the scattering has certain well known properties which is called Rayleigh scattering. Since the group velocity of a light pulse in a given fiber is known at the time of transmission, the returned signal, measured as a function of time, is an indication of the propagation distance within the fiber. Therefor, faults and losses can be (92-3-3S7.PCT) calibrated as a function of fiber length for a telecommunications link.
  • the backscattered optical power at any point along a telecommunications grade single mode optical fiber is on the order of 10 of the forward propagating optical power and thus receivers with good sensitivity and a large dynamic range are required to detect this backscatter.
  • the low level of the Rayleigh backscattered signal can be enhanced by using extremely high power lasers (>10 mW) to generate the light pulse.
  • extremely high power lasers >10 mW
  • apparatus and method for using the optoelectronic transmitters and receivers coupled to the system terminal equipment to transmit and receive the optical signals necessary for OTDR measurements The electronic signal processing required for OTDR measurements is shared among many fiber links, but the optoelectronics coupled to the system data terminal equipment provide the test light pulses, and detect the return light pulses.
  • the existing system transmitters and receivers act as the optical front end for the OTDR system, and an electronic crossbar switch allows a single signal processing device to access a plurality of optical front ends and thus many fiber lines.
  • FIG. 1 is a conventional system for taking OTDR measurements.
  • FIG. 2 is a system for taking OTDR measurements using an electronic IXN switch which is coupled to the system transmitters and receivers in accordance with the instant invention.
  • System 100 includes a plurality of optical fibers 105, 106, 107, 108, 109 for transferring data.
  • the fibers 105, 106, 107, 108, 109 are individually coupled by splitters 110, 111, 112, 113, 114 to unique line cards 120, 121, 122, 123, 124 which transmit and receive optical signals and to a IXN Optical Space Switch 130 for generating and receiving the OTDR test signals.
  • Line cards 120, 121, 122, 123, 124 are further coupled to system data terminal 125 which is typically a computer processor for processing the data sent and received by the line cards.
  • optical fibers 105, 106, 107, 108, 109 are shown with their accompanying line cards 120, 121, 122, 123, 124 and splitters 110, 111, 112, 113, 114 in FIG. 1 for convenience.
  • switch 130 blocks the optical signal from line card 124 and allows the OTDR test signal from the OTDR Signal Processing Unit 140 to replace it on fiber 109.
  • OTDR Signal Processing Unit 140 is controlled by an OTDR Optical Control System 150 to control the OTDR testing and has a data base to initiate, store, and display measurements.
  • OTDR Optical Control System 150 may control OTDR Signal Processing Unit 140 via a remote network 160, and also provides standard and open interfaces to other operating support systems.
  • System 200 includes a plurality of optical fibers 205, 206, 207, 208, 209 for transferring data.
  • the fibers 205, 206, 207, 208, 209 are individually coupled to unique line cards 220, 221, 222, 223, 224 which transmit and receive optical signals and to a IXN Electronic Space Switch 230 for passing an electical signal from Signal Processor 240 to the line cards and receiving the OTDR test pulse which has beeb converted to an electrical signal by the line cards.
  • system data terminal 225 which is typically a computer processor for processing the informational data sent and received by the line cards. Only five optical fibers 205, 206, 207, 208, 209 are shown with their accompanying line cards 220, 221,
  • OTDR Signal Processing Unit 240 is controlled by an OTDR Control System 250 which monitors and controls the OTDR testing and has a data base to initiate, store, and display the OTDR measurements.
  • OTDR Control System 250 may control OTDR Signal Processing Unit 240 via a remote network 260, and also provides standard and open interfaces to other operating support systems.
  • line card 224 provides single wavelength bi-directional communications (i.e., the line card contains both a receiver, a transmitter, and a combiner/splitter), then no additional optoelectronic or optical components are required to perform the OTDR function. However if line card 224 does not provide for bi-directional communications, then a transmitter and combiner/splitter must be added to the line card if the line card only has receive capability. Adding the transmitter and combiner/splitter causes the receiver to incur an additional power penalty which is typically 3 dB. Conversely, if the line card only has a transmitter capability then a receiver and combiner/splitter must be added. Again there will be a 3dB loss.
  • An electronically switched, line card based OTDR system operates as follows in accordance with one embodiment of the current invention.
  • the receiver portion of the line card 224 monitors the average received optical power, either dc . photocurrent or feedback voltage from automatic gain control in addition to recovering the optical data signal. If the optical signal substantially degrades or is unable to be recovered, the line card 224 checks to see if received optical power has similarly been degraded. If the received optical power has been degraded, after waiting a set period of time to see if the optical signal is restored, the line card initiates an OTDR measurement to check the condition of the optical fiber.
  • sequence of events for initiating an OTDR measurement in accordance with the present invention is as follows.
  • the line card 224 first sends an alarm to the system data terminal 225, and a local alarm to the OTDR Signal Processing Unit 240 via Electronic Switch 230.
  • the OTDR Signal Processing Unit 240 places the IXN Electrical Switch 230 in a position to pass electrical analog or digital data consisting of the electrical OTDR signals to the line card 224.
  • the line card 224 places itself in the OTDR test mode in which it accepts the elctrical OTDR signal from the OTDR Signal Processing Unit 240 via Electronic Switch 230, converts the electrical signal to an optical OTDR pulse, and sends the pulse by transmitter 228.
  • the Rayleigh backscattered signal is received by receiver 229, converted to an electrical signal and passed to the OTDR Signal Processing Unit 240 via Electronic Switch 230.
  • the line card receiver 229 may modify the parameters of the transmitter/receiver module to enhance the performance response of the system to long pulses by changing the biasing circuit in the transmitter and the preamplifier circuit in the receiver to lower the bandwidth and improve sensitivity.
  • the OTDR Signal Processing Unit 240 processes the data from the line card using signal averaging, filtering, and fault location algorithms to measure the condition of the optical link.
  • the condition of the link is communicated by OTDR Signal Processing Unit to the OTDR Control System for remedial action.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Testing Of Optical Devices Or Fibers (AREA)
  • Optical Communication System (AREA)

Abstract

Nouveau système permettant d'effectuer des mesures par réflectométrie optique à dimensions temporelles (RODT) sur une multiplicité de fibres optiques (105, 106, 107, 108, 109) et consistant à utiliser uniquement les émetteurs et les récepteurs de données du système. Le système comprend l'utilisation de cartes de ligne optiques (120, 121, 122, 123, 124), qui sont généralement utilisées pour la transmission des données du système, afin de détecter des défaillances. La détection d'une défaillance dans une fibre optique amène la carte de ligne associée à la fibre à interrompre la transmission de données et à avertir le processeur (140) de signaux afin de faire démarrer la mise à l'essai par RODT. Le processeur de signaux est couplé à chacune des cartes de ligne par l'intermédiaire d'un commutateur 1XN électronique, afin que chaque fibre puisse être individuellement mise à l'essai.
PCT/US1993/012684 1992-12-31 1993-12-30 Procede d'analyse de fibres et systeme de reflectometrie optique eloignee, a dimensions temporelles et a commutation electrique WO1994016347A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US99904392A 1992-12-31 1992-12-31
US99904592A 1992-12-31 1992-12-31
US07/999,045 1992-12-31
US07/999,043 1992-12-31

Publications (1)

Publication Number Publication Date
WO1994016347A1 true WO1994016347A1 (fr) 1994-07-21

Family

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Application Number Title Priority Date Filing Date
PCT/US1993/012684 WO1994016347A1 (fr) 1992-12-31 1993-12-30 Procede d'analyse de fibres et systeme de reflectometrie optique eloignee, a dimensions temporelles et a commutation electrique

Country Status (1)

Country Link
WO (1) WO1994016347A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5552881A (en) * 1994-03-17 1996-09-03 Teradyne, Inc. Method and apparatus for scanning a fiber optic network
CN1081415C (zh) * 1996-05-24 2002-03-20 林中翔 光纤电缆干线网络载线自动测试告警系统及其测试方法
EP1524781A1 (fr) * 2003-10-15 2005-04-20 Alcatel Surveillance de performance d'une liaison optique par OTDM avec un laser pour transmission/réception de données

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4306313A (en) * 1979-10-11 1981-12-15 International Telephone And Telegraph Corporation High reliability optical fiber communication system
US4749247A (en) * 1986-04-03 1988-06-07 The Mitre Corporation Self-monitoring fiber optic link
JPH021632A (ja) * 1988-01-11 1990-01-05 Nippon Telegr & Teleph Corp <Ntt> 光線路試験方式
US4898463A (en) * 1987-11-27 1990-02-06 Anritsu Corporation Optical time domain reflectometer with automatic measuring function of optical fiber defects
US4911515A (en) * 1988-12-22 1990-03-27 Northern Telecom Limited Optical fiber communications system with optical fiber monitoring
US5285305A (en) * 1991-12-12 1994-02-08 At & T Bell Laboratories Optical communication network with passive monitoring

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4306313A (en) * 1979-10-11 1981-12-15 International Telephone And Telegraph Corporation High reliability optical fiber communication system
US4749247A (en) * 1986-04-03 1988-06-07 The Mitre Corporation Self-monitoring fiber optic link
US4898463A (en) * 1987-11-27 1990-02-06 Anritsu Corporation Optical time domain reflectometer with automatic measuring function of optical fiber defects
JPH021632A (ja) * 1988-01-11 1990-01-05 Nippon Telegr & Teleph Corp <Ntt> 光線路試験方式
US4911515A (en) * 1988-12-22 1990-03-27 Northern Telecom Limited Optical fiber communications system with optical fiber monitoring
US5285305A (en) * 1991-12-12 1994-02-08 At & T Bell Laboratories Optical communication network with passive monitoring

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5552881A (en) * 1994-03-17 1996-09-03 Teradyne, Inc. Method and apparatus for scanning a fiber optic network
CN1081415C (zh) * 1996-05-24 2002-03-20 林中翔 光纤电缆干线网络载线自动测试告警系统及其测试方法
EP1524781A1 (fr) * 2003-10-15 2005-04-20 Alcatel Surveillance de performance d'une liaison optique par OTDM avec un laser pour transmission/réception de données

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