WO2003052976A2 - Systeme de communication optique - Google Patents

Systeme de communication optique Download PDF

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Publication number
WO2003052976A2
WO2003052976A2 PCT/IL2002/000931 IL0200931W WO03052976A2 WO 2003052976 A2 WO2003052976 A2 WO 2003052976A2 IL 0200931 W IL0200931 W IL 0200931W WO 03052976 A2 WO03052976 A2 WO 03052976A2
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WO
WIPO (PCT)
Prior art keywords
communication system
optical communication
source
receiver
transmitter
Prior art date
Application number
PCT/IL2002/000931
Other languages
English (en)
Other versions
WO2003052976A3 (fr
Inventor
Ram Oron
Doron Nevo
Moshe Oron
Original Assignee
Kilolambda Ip Limited
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 Kilolambda Ip Limited filed Critical Kilolambda Ip Limited
Priority to AU2002343195A priority Critical patent/AU2002343195A1/en
Publication of WO2003052976A2 publication Critical patent/WO2003052976A2/fr
Publication of WO2003052976A3 publication Critical patent/WO2003052976A3/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
    • H04B10/50—Transmitters

Definitions

  • the present invention relates to multi-line, multi-wavelength transmitters and receivers for dense wavelength division and multiplexing (DWDM) optical communication. More particularly, the invention is directed toward providing dense transmission channels, providing users with wavelength communication lines at a desired bandwidth in two directions, namely, one downstream from a sender or a central or main office (referred to herein as "main office") to an end user/subscriber, and one upstream from an end user/subscriber to a central or main office.
  • main office central or main office
  • the portion closest to the end-user/subscriber also known as the access network, is characterized by the need to bring a separate optical channel to each subscriber, allowing for the use of a wide band and for bi-directional optical communications capability.
  • a common fiber optical link or loop serves many subscribers, each subscriber picking up its own designated downstream wavelength. This arrangement calls for very dense line distribution, wherein the stability of the line spacing in varying environmental conditions is of major importance.
  • General access communication in an optical fiber network requires at least 100 Mbps, and preferably up to 2 Gbps, in each direction, upstream and downstream of the optical link to the subscriber.
  • the system may designate two wavelengths for each subscriber, one modulated with the downstream data and the second unmodulated, to be used for modulation at the subscriber's station and for sending the modulated data back through the fiber.
  • the two downstream and upstream channels may be close to each other in their wavelengths. For example, both channels may be in the 1500 nm range or in the 1300 nm range, or spectrally separated, one in the 1500 nm range and the other in the 1300 nm range.
  • a dense multi-wavelength source supplying a multitude (up to hundreds or even thousands) of different wavelengths, is placed in a central or main office.
  • Each of the different wavelengths or channels is separated, spatially or angularly, so it can be propagated in a dedicated optical fiber.
  • the main office designates a specific channel or a number of channels to that subscriber.
  • the data designated for each of the specific subscribers is then modulated at the central office on the specific channels.
  • Sometimes the same data is sent to a multitude of subscribers ("broadcasting"); in this case, a single modulator may be used for a few channels. Some of the channels may be left unmodulated in the central office, after being transmitted from the wavelengths source.
  • These channels are dedicated for upstream communication, namely, for data sent by the subscribers to the main office. Furthermore, these channels may have wavelengths in the same wavelength band as that of the modulated channels, or they may be of different wavelength bands, e.g., one in the 1.3 micro-meter band, and the other in the 1.55 micro-meter band.
  • Both the modulated light, containing data from the main office to the subscribers, and the unmodulated light, dedicated for modulation by the subscribers for data to be sent from the subscribers to the main office, can be combined to propagate in the same waveguide. This is achieved by a multiplexing device, which combines the multitude of different wavelengths propagating in a plurality of waveguides into a single waveguide.
  • Some other unmodulated channels emerging from the wavelength source can be inserted into another, second, waveguide. These channels may have the same wavelengths as some of the modulated channels propagating towards the subscribers in the first waveguide. These channels are later used as part of the demultiplexing (or dropping) subsystem at the subscriber's end, or as parts of the all-optical, selective amplification of the transmitted data. These channels serve as reference wavelengths between the source/transmitter and the receiver, and only a single or few of these wavelengths that are transmitted can generate multiple combs for reference and selective amplification. These reference wavelengths are also called “pumps" for optical Brillouin amplifiers, as will be described in detail below.
  • the first step is to drop a group of wavelengths having a total width of, e.g., 10 GHz (10 channels with a 1 GHz separation), using a grating or another selective filter, followed by a novel separation module where the separation is carried out by a specially designed set of, e.g., 10, parallel Brillouin amplifiers.
  • the Brillouin amplifiers each amplify a single wavelength.
  • the Brillouin amplification occurs when a narrow band optical seed signal, having the same frequency as the back-scattered wave, is propagated in the opposite direction of the pump light in an optical waveguide.
  • the interaction between the seed or signal and the pump enhances the acoustic grating initially generated by the pump, and this increases the back-scattering of the pump into the seed signal, thereby amplifying the signal. This effect can be used to selectively amplify desired signals for further processing, detection or regeneration, where all other signals remain low and do not affect the system.
  • the central, amplified wavelength for each Brillouin amplifier is designed by selecting one wavelength from a wavelength comb as a pump for a group of Brillouin amplifiers, where the low spacing line is defined by material selection.
  • the amplifiers are each made of a different material, selected so that each amplifier amplifies a channel (a single wavelength), although the pump wavelength is the same for all the amplifiers, matching the channels to be separated/amplified, each having an input end and an output end, the pump line fitting all the amplifiers.
  • the pump wavelength is supplied from the main office, serving as the energy source for the amplification and as a reference wavelength.
  • the pump line may be different for each set of amplifiers, and may be created in the main office as a comb.
  • the width of the pump line can be made to fit the modulated line width data line to be amplified by the use of a few adjacent, very closely packed pump lines, creating a wider, combined line. These lines are created in parallel and are transmitted as one wide pump line.
  • the data-containing lines are detected by a light receiver/detector and, from this point, are treated as electronic data signals.
  • the unmodulated channels are treated in an "all optical" way, namely, they are modulated by the subscriber's data through an optical modulator and sent back to the main office in either the incoming waveguide or additional waveguides.
  • all of the wavelengths, modulated, unmodulated and pump may have optical (fiber or solid state) amplifiers along the lines and at their two ends.
  • the system can have either a single main office or multiple main offices carrying data in multiple directions.
  • the system is built of duplicates of the single main office unit, and all share the same pump lines which serve as pumps for the Bruillouin amplifiers and a reference wavelength for the light sources in all of the main offices.
  • the light source and pump are generated only at one of the main offices, and are shared by all of them. Disclosure of the Invention
  • the invention provides an optical communication system between a main office and a user/subscriber, comprising at least one source/transmitter for producing a plurality of optical radiation output signals, the output signals having predetermined wavelengths and being fed to output waveguides, the source/transmitter being capable of maintaining constant intra-wavelength spacings between the output signals; a plurality of modulators, each coupled to one of at least several of the output waveguides and leading to a multiplexer; two receiver/demultiplexer units, each followed by a detector unit, and at least one pump line for passing optical radiation from the source/transmitter to the receiver/demultiplexer units.
  • Fig. 1 is a schematic illustration of a first embodiment of a two-way communication system according to the present invention
  • Fig. 2 is a detailed illustration of the structure of a very dense demultiplexer and detector
  • Fig. 3 is a schematic illustration of a multi-user/subscriber system
  • Fig. 4 depicts a second embodiment of a two-way communication system according to the invention
  • Figs. 5 and 6 illustrate the principle of the generation of the spectrally widened source
  • Fig. 7 shows the spectrum of the widened pump source pump needed for the separation of modulated lines.
  • Fig. 1 there is shown an embodiment of a communication system according to the present invention, utilizing a single source/transmitter 10 and two dense receiver/demultiplexer units 12, 14, followed by electronic detector units 16, 18.
  • Receiver/demultiplexer unit 14 and detector unit 18 are located at the subscriber's end and receiver/demultiplexer unit 12 and its detector unit 16 are located at the sender, or main office, end, either as part of, or separated from, source/transmitter 10.
  • source/transmitter 10 generates optical signals of wavelengths ⁇ t to ⁇ affiliation, each being transmitted over a separate waveguide 20 ⁇ to 20 friendship, such as, e.g., fibers.
  • Each waveguide 20 ⁇ to 20 leads through a modulator 22 !
  • a pump line 38 which is common to the entire system, serves as a reference and connects source/transmitter 10 with dense demultiplexer units 12 and 14.
  • the system may also include several amplifiers 40, depicted by broken lines at various locations along the optical transmission lines.
  • Each of input pump lines 46 ! to 46 ownership is commonly connected to pump line 38 of the system via a splitter 48 and passes, via a splitter 50, at the end opposite to their inputs from common line 26, to each of the amplifiers 44 1 to 44 ownership, all having the same pump wavelength.
  • the input pump lines 46 ! to 46 ownership are connected to the amplifier output lines 36] to 36 shadow through circulators 51i to 51 religious.
  • the Brillouin amplification occurs when a narrow band seed signal, having the same frequency as the back-scattered wave, is propagated in the opposite direction of the direction of propagation of the pump.
  • the interaction between the seed signal and the pump enhances the acoustic grating initially generated by the pump, and this increases the back-scattering of the pump into the seed signal, thereby amplifying the signal.
  • This effect can be used to selectively amplify desired signals for further processing, where all other signals remain low and do not affect the system.
  • the central, received wavelength is designed by material selection.
  • n 2nVs/ ⁇ p for each one of the amplifiers.
  • Strain and temperature are used to fine-tune the frequency difference to the desired wavelength.
  • a selective amplifier allows detection of the amplified signal in the presence of all the others as background noise.
  • the line width is material- and pump-dependent, and is selected in a manner appropriate to the designed bandwidth of the communication channel. In cases where the single pump line width is not wide enough to contain the width of the data channel, a widened pump line is used, combined of an additional few closely packed lines, as will be described below with reference to Fig. 7.
  • the amplified signals in each output line 36] to 36 school are eventually separated by Brillouin amplifiers of different materials, pumped by the system's internal pump line.
  • the doping strongly affects the index n. Strain and temperature are used for fine tuning, affecting both n and the velocity of sound.
  • Fig. 3 illustrates a multi-subscriber system fed from a line 26 of a common source and having a single pump line 38 and return line 34.
  • Each of the demultiplexer units 14 is connected to lines 26 and 38 via splitters/optical circulators 42, 48 and to the return line 34 via modulators 32 t to 32 perpetrat and directly to the subscriber's detectors 18 ! to 18 jurisdiction through output lines 36i to 36 ownership.
  • splitters/optical circulators 42 or 48 on lines 26 and 38 there are affixed reflection filters or gratings 52 ! to 52 shadow and 53 1 to 53 broadcast.
  • the gratings may be constituted by per se known Bragg gratings, or by arrayed waveguide gratings (AWGs), each produced to provide a predetermined wavelength separation or spacing, e.g., a separation of 10 GHz from each other, while the lines exiting modulators >2 ⁇ to 32 radiation are separated by, e.g., 1 GHz.
  • the multi-subscriber system may contain a plurality of dense demultiplexer units 14 and 18, as shown, wherein each of the plurality of units is fed separately by the data wavelength and unmodulated wavelength via line 26 and obtains the needed pump via line 38.
  • Line 38 may carry one or many pump wavelengths. In the case of a plurality of wavelengths, they can be generated as a comb having a spacing of, e.g., 10 GHz, as described in Israel Patent Application Nos. 141,727 and 144,498.
  • FIG. 4 A further embodiment of a two-way communication system is illustrated in Fig. 4.
  • the system is duplicated with all its parts in two locations, but is served with a single, common optical pump line for both systems.
  • each system there is a source/transmitter 10, 10' and a dense demultiplexer unit 12, 12', followed by a detector at each end of the communication network.
  • the waveguides 20 1 to 20 administrat, 20/ to 20/, of the source/transmitters 10, 10' are lead through modulators 22i to 22 administrat, 22 to 22/, to common multiplexers 24, 24' and to the dense demultiplexer units 12, 12', followed by a detector.
  • a single pump line 38 interconnects each one of the source/ transmitters 10, 10' with one respective dense demultiplexer unit 12, 12', serving as the reference and pump of the two-way system.
  • Figs. 5 and 6 illustrate the layout of the line generation, where the pump line ⁇ 0 is injected via optical splitters 60 to a multitude of different materials 62, each having, for example, different doping of germanium oxide in silica fibers, resulting in a preselected frequency difference between the pump and the SBS (Simulated Brillouin Scattering) generated light for each one of the stages.
  • the injection can be done in parallel, as depicted in Fig. 5, or in series, as depicted in Fig. 6.
  • the SBS generators are each made of a different material, selected so that each gives the required wavelength for a wide source, as shown spectrally in Fig. 7.
  • This Figure shows, in the spectral dimension, the SBS generation of a plurality of lines having different spacing from the ⁇ 0 pump line, using a different composition of materials for the SBS generating parts.
  • the plurality of lines produces a widened line of n times the individual line.

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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)

Abstract

L'invention concerne un système de communication optique mis en oeuvre entre un poste principal et un utilisateur/abonné et comprenant: au moins une source/émetteur permettant de produire une pluralité de signaux de sortie de rayonnement optique, les signaux de sortie possédant des longueurs d'ondes prédéterminées et étant alimentés dans des guides d'ondes de sortie, la source/émetteur étant capable de conserver des espacements constants dans les longueurs d'ondes entre les signaux de sortie; ainsi qu'une pluralité de modulateurs, chacun étant couplé à au moins un guide d'ondes de sortie et conduisant à un multiplexeur; deux unités de récepteur/démultiplicateur, chacune suivie d'une unité de détection, et au moins une ligne de pompage permettant de passer un rayonnement optique de la source/émetteur vers les unités de récepteur/démultiplicateur.
PCT/IL2002/000931 2001-11-22 2002-11-21 Systeme de communication optique WO2003052976A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002343195A AU2002343195A1 (en) 2001-11-22 2002-11-21 Optical communication system

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IL146691 2001-11-22
IL146691A IL146691A (en) 2001-11-22 2001-11-22 Optical communication system

Publications (2)

Publication Number Publication Date
WO2003052976A2 true WO2003052976A2 (fr) 2003-06-26
WO2003052976A3 WO2003052976A3 (fr) 2004-03-18

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IL (1) IL146691A (fr)
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0261876A2 (fr) * 1986-09-26 1988-03-30 AT&T Corp. Récepteur optique à bande étroite accordable en fréquence
EP0408394A1 (fr) * 1989-07-13 1991-01-16 BRITISH TELECOMMUNICATIONS public limited company Réseau de communication optique
US6118561A (en) * 1996-09-10 2000-09-12 Fujitsu Limited Wavelength division multiplexing optical transmitter and wavelength division multiplexing-demultiplexing optical transmission-reception system
US6271944B1 (en) * 1999-06-30 2001-08-07 Philips Electronics North America Corp. Laser wavelength control in an optical communication system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0261876A2 (fr) * 1986-09-26 1988-03-30 AT&T Corp. Récepteur optique à bande étroite accordable en fréquence
EP0408394A1 (fr) * 1989-07-13 1991-01-16 BRITISH TELECOMMUNICATIONS public limited company Réseau de communication optique
US6118561A (en) * 1996-09-10 2000-09-12 Fujitsu Limited Wavelength division multiplexing optical transmitter and wavelength division multiplexing-demultiplexing optical transmission-reception system
US6271944B1 (en) * 1999-06-30 2001-08-07 Philips Electronics North America Corp. Laser wavelength control in an optical communication system

Also Published As

Publication number Publication date
WO2003052976A3 (fr) 2004-03-18
AU2002343195A1 (en) 2003-06-30
IL146691A0 (en) 2002-07-25
IL146691A (en) 2006-12-31

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