WO2001063802A1 - Source laser a longueurs d'ondes multiples - Google Patents

Source laser a longueurs d'ondes multiples Download PDF

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Publication number
WO2001063802A1
WO2001063802A1 PCT/US2001/003694 US0103694W WO0163802A1 WO 2001063802 A1 WO2001063802 A1 WO 2001063802A1 US 0103694 W US0103694 W US 0103694W WO 0163802 A1 WO0163802 A1 WO 0163802A1
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WO
WIPO (PCT)
Prior art keywords
laser source
accordance
optical
output
multiple wavelength
Prior art date
Application number
PCT/US2001/003694
Other languages
English (en)
Other versions
WO2001063802A9 (fr
Inventor
Henry Hung
Original Assignee
Tedram Optical Networks, Inc.
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
Priority claimed from US09/510,685 external-priority patent/US6587239B1/en
Priority claimed from US09/511,053 external-priority patent/US6583901B1/en
Application filed by Tedram Optical Networks, Inc. filed Critical Tedram Optical Networks, Inc.
Priority to AU2001274797A priority Critical patent/AU2001274797A1/en
Publication of WO2001063802A1 publication Critical patent/WO2001063802A1/fr
Publication of WO2001063802A9 publication Critical patent/WO2001063802A9/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0278—WDM optical network architectures
    • H04J14/0283—WDM ring architectures
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0204—Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0205—Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H04J14/0241—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
    • H04J14/0242—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON
    • H04J14/0245—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for downstream transmission, e.g. optical line terminal [OLT] to ONU
    • H04J14/0246—Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths in WDM-PON for downstream transmission, e.g. optical line terminal [OLT] to ONU using one wavelength per ONU
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2821—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers using lateral coupling between contiguous fibres to split or combine optical signals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2383—Parallel arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/002—Coherencemultiplexing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0227—Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0278—WDM optical network architectures
    • H04J14/0282—WDM tree architectures
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0278—WDM optical network architectures
    • H04J14/0284—WDM mesh architectures

Definitions

  • This invention pertains to optical communications systems, in general, and an optical communications system utilizing a multiple wavelength laser source to provide channel synchronization, in particular.
  • optical network relates to any network that interconnects a plurality of nodes and conveys mfo ⁇ nation between nodes with optical signals.
  • optical communications system refers to any system that utilizes optical signals to convey information between one node and one or more other nodes.
  • An optical communications system may include one or more optical networks.
  • optical fiber systems relied on time division multiplexing to route traffic through a channel. Time division multiplexed systems add more capacity by tune multiplexing signals onto an optical fiber. A disadvantage of time division multiplex systems is that data must be converted from light waves to electronic signals and then back to light. The system complexity is thereby increased.
  • Wavelength Digital Multiplexing WDM
  • DWDM Dense Wavelength Digital Multiplexing
  • WDM and DWDM are being used and/or proposed for use in long-haul telecom network applications for increasing the capacity of existing fiber optic networks.
  • WDM and DWDM would appear to many to be the solution to optical network limitations.
  • WDM plural optical channels are caixied over a single fiber optic, with each channel being assigned to a particular wavelength.
  • optical amplifiers multiple optical channels are directly amplified simultaneously thereby facilitating the use of WDM systems in long-haul optical networks.
  • DWDM is a WDM system in which channel spacing is on the order of one nanometer or less.
  • WDM and DWDM expand the capacity of an optical fiber by multiple wavelength channels into a single laser beam. Each wavelength is capable of carrying as much traffic as the original.
  • traffic passes from one node of the network to its destination in the form of light waves without conversion to electrical signals.
  • DWDM and WDM will permit increase in the capacity of the fiber infrastructure.
  • a plurality of optical channels is provided and the optical channels are utilized for communications among a pluraUty of communications nodes.
  • Each optical channel is determined by at least two of three optical signal characteristics. At least one of the optical signal characteristics is selected from a pluraUty of predete ⁇ nined optical wavelengths.
  • the pluralities of multiple optical wavelengths are provided by a multiple wavelength laser source.
  • a multiple wavelength laser source is utilized to provide channel synchronization signals for the system.
  • the laser source utilizes a plurality of distributed feedback (DFB) lasers.
  • the output of each DFB laser is phase modulated, and the phase modulated outputs are multiplexed together and amplified.
  • DFB distributed feedback
  • a multiple wavelength laser source in accordance with the invention comprises a plurality, m, of distributed feedback lasers.
  • Each of the lasers generates optical signals at a predete ⁇ nined one of a plurality, m, of wavelengths.
  • Each of a corresponding plui'ality, m, of phase modulators is coupled to a corresponding one laser of the plui'ality of distributed feedback lasers.
  • Each of the phase modulators modulates optical signals from a coixesponding one laser with radio frequency signals having multiple frequency components to produce optical signals having a broad line width.
  • a multiplexer is coupled to each of the plui'ality of phase modulators to multiplex together the outputs of each of said phase modulators to produce a multiplexed multiple wavelength optical output having a plui'ality, m, of wavelength outputs.
  • An amplifier is coupled to the output of said multiplexer to amplify the output thereof.
  • a multiple wavelength laser source comprises a plurality, m, of lasers, with each of laser generating optical signals at a predetermined one of a plui'ality, m, of wavelengths. The optical signals have a line width less than 50 MHz.
  • a corresponding pluraUty, m, of phase modulators are each coupled to a corresponding one laser of the plurality of distributed feedback lasers. Each phase modulators modulates the optical signals from the corresponding one laser with radio frequency signals having multiple frequency components to produce optical signals having a broad line width of greater than 10
  • a multiplexer is coupled to each of said phase modulators to multiplex together the outputs of each of said phase modulators to produce a multiplexed multiple wavelength optical output having a plui'ality, m, wavelength outputs.
  • An amplifier is coupled to the output of said multiplexer to amplify the output thereof.
  • a method of providing a multiple wavelength laser source comprises providing a plurality, m, of distributed feedback lasers.
  • Each laser generates optical signals at a predete ⁇ nined one of a plui'ality, m, of wavelengths.
  • Phase modulating the optical signals from each co ⁇ esponding one laser with radio frequency signals having multiple frequency components produces optical signals having a broad line width. Multiplexing together the phase modulated optical signals produces a multiplexed multiple wavelength optical output having a plurality, m, of wavelength outputs. Amplifying the multiplexed output of said multiplexer produces the output signals.
  • FIG. 1 depicts an optical communication system in accordance with the principles of the invention
  • FIG. 2 depicts representative optical signal power distribution levels in a portion of the system of FIG. 1; .
  • FIG. 3 illustrates multiplexing of optical signals in accordance with the principles of the invention
  • FIG. 4 is a block diagram of a system control unit in the system of FIG. 1;
  • FIG. 5 is flow chart illustrating channel assignment in accordance with the invention.
  • FIG. 6 is iUusfrates the wavelength multiplexing utiUzed in the system of FIG. T;
  • FIG. 7 illustrates use of interferometer technology in an embodiment of the invention
  • FIG. 8 illustrates a frequency multiplex/switch layer implementation utilized in an embodiment of the invention
  • FIG. 9 illustrates in block diagram fonn a frequency modulator and frequency demodulator for use in a system in accordance with the invention
  • FIG. 10 iUusfrates the multiplexing of signals in a second embodiment of the invention in accordance with the principles of the invention
  • FIG. 11 illustrates, in simplified fonn, the transmission of data from one network node to a second network node
  • FIG. 12 illustrates, in simplified foiin, the transmission of data from the second network node to the first network node of FIG. 11;
  • FIG. 13 is a block diagram of a network node in accordance with the invention.
  • FIG. 14 is a detailed block diagram of a portion of a first optical network processor (ONP) for use with an embodiment of the invention
  • FIG. 15 is a detailed block of a second portion of the first optical network processor useable in conjunction with the optical network processor portion of FIG. 14;
  • FIG. 16 is a detailed block diagram of a second optical network processor;
  • FIG. 17 is a detailed block diagram of a first portion of a ti ird optical network processor for use with the second embodiment of the invention
  • FIG. 18 is a detailed block diagram of a second portion of the third optical network processor useable in conjunction with the optical network processor portion of FIG. 17
  • FIG. 19 is a detailed block diagram of a fourth optical network processor
  • FIGs. 20 through 23 depict multiple wavelength laser reference sources
  • FIGs. 24 and 25 depict Erbium doped fiber lasers (EDFLs) utilized in the reference sources of FIGs. 20 through 23; and
  • EDFLs Erbium doped fiber lasers
  • FIG. 26 depicts an optical add/drop (OAD). DETAILED DESCRIPTION
  • a system in accordance with one aspect of the invention is able to provide for bandwidth upgrade to existing optical fiber networks and optical communications systems.
  • Increasing the available channel count and speed increases the bandwidth of existing optical networks.
  • the number of concuirently available channels is increased over WDM systems by a factor of 10 to 200 pe ⁇ nitting serving up to 20,000 channels simultaneously.
  • the number of channels and an occupancy factor deteiTnines the number of users that may be served by a multi-channel communications system.
  • the system of the present invention may be used to provide communications for in excess of 200,000 users concuirently.
  • FIG. 1 depicts an optical communication system 1000 in accordance with the principles of the invention.
  • Optical communication system 1000 includes a Metro Network 1100 coupled to a Long Haul Network 1200 via an optical add/drop module 1203 and optical cross connect module 1205.
  • Metro Network 1100 couples one or more local access networks 1301, 1303, 1305 to each other and to Long Haul Network 1200.
  • Long Haul Network 1200 interconnects plural Metro Networks 1100.
  • Metro Network 1100 For purposes of clarity in ti e drawings and simplicity in the description, only one Metro Network 1100 is shown. Mefro Networks 1100 are typically located at widespread geographic locations. However, it is not intended to limit applicability of the present invention to arrangements in which networks are dispersed geographically. The present invention is applicable to networks that are overlapping in geographic ai'eas or even to networks that are in the same geographic area.
  • Metro Network 1100 is, in the illustrative embodiment, depicted as a ring-based metropolitan network system. Metro Networks are intended to provide high bandwidth to end customers directly and/or via local loop access networks. In the illustrative embodiment depicted in FIG. 1, Metro Network 1100 is depicted as a ring based network having a fiber optic ring 1101. It will be understood by those skilled in the art that the invention is not limited to use in networks that are of a ling based structure. The principles of the invention are equally applicable to other network architecture structures including, not by way of limitation but by way of example, star network structures, mesh network structures, and point-to-point structures. For purposes of clarity and brevity, those additional network architecture structures are not shown in ti e drawing.
  • the illustrative embodiment of the invention depicts a Metro Network coupled to plural Access Networks 1300, the principles of the invention are not so limited.
  • those skilled in the art will realize that the particular nomenclature used to describe the illustrative embodiment is also not intended to be lnniting of the invention in any manner. For example, it is not intended to Umit any aspect of the invention to so-called "Metro Network” applications.
  • Those skilled in the art are familiar with the specific te ⁇ ninology utilized to describe the illustrative embodnnent and will realize that the invention is applicable to other named communication systems and networks. For example, the principles of the present invention are applicable to "long haul" networks.
  • the principles of the invention are not limited to optical communications systems utilizing only optical fiber for the communications paths.
  • Those skilled in the art will recognize that various other tenns may be used to" describe or designate the identical or similar networks.
  • the term “long distance network” is also used in place of "long haul network”.
  • Each Access Network 1301, 1303, 1305 is coupled to optical fiber ring 1101 of Mefro Network 1100 via "add and drop nodes” referred to herein as optical add/drops (OADs) 1307, 1309, 1311, respectively.
  • OADs optical add/drops
  • Optical add/drops in various fonns are known to those skilled in the art. In its simplest fo ⁇ n an optical add/drop is a coupler. Optical add/drops are used to add or exfract optical signals.
  • OADs 1307, 1309, 1311 are utilized to inject (add) and retrieve (drop) optical signals into and from optical fiber ring 1101. Both add and drop are bi-directional with respect to optical fiber ring 1101.
  • optical signals may be fransmitted in or received from either direction, i.e., to the right or to the left in the ring as shown, on optical fiber ring 1101.
  • OADs utilized in the embodiment of the invention described herein provide broadband operation.
  • An OAD particularly advantageously utilized in the embodiments of the invention is show in FIG. 26 and described in greater detail with respect to FIG. 26.
  • Each optical add/drop 1307, 1309, 1311 is, in turn, coupled to an optical fiber amplifier 1313, 1315, 1317.
  • Optical fiber amplifiers 1313, 1315, 1317 may be of known design.
  • the optical fiber amplifiers 1313, 1315, 1317 are each Erbium-doped amplifiers (EDFAs).
  • EDFAs are the latest state-of-the-art solution for broadband amplification of optical signals in optical communication systems. EDFAs are commercially available from various sources. EDFAs overcome propagation losses of the optical signals through the optical fiber and boost the optical signals to necessary receiver levels. EDFAs can be used to amplify WDM and DWDM signals.
  • Access network 1301 includes a plurality of access locations or nodes that include a residential complex 1331 and a small office building 1333. Other access locations are not shown for clarity, but it will be understood that more than two access locations may be coupled into access network 1301. Furthermore, it will be understood by those skilled in the art that the various types of access locations or nodes shown are merely representative of the types of end users and are not intended in any way to limit the scope of the invention.
  • the terms "node” and "access location” ai'e used interchangeably herein.
  • Each access location 1331, 1333, 1341, 1343, 1351 has associated with it an optical network processor 1335, 1337, 1345, 1347, 1353.
  • Access network 1303 includes user complex 1341 and office buildingl343 along with other locations that are not shown.
  • Optical network processors 1345, 1347 ai'e utilized to provide network access functionality for user complex 1341 and office building 1343, respectively.
  • Access network 1305 includes large office complex 1351 and a single optical network processor 1353.
  • any user at any of the locations 1331, 1333, 1341, 1343, 1351 can utilize the communications system shown to access and exchange infbrniation with any other user in access networks 1301, 1303, 1305 or any other user coupled to Mefro Network 1100 or to any user coupled to long haul network 1200.
  • the system of the invention can use any idle channel as a communications channel between any two users or nodes.
  • optical reference signals originating at a reference laser source are utilized to provide for channel synchronization and to permit a significant increase in the number of channels that are available for use in the system.
  • an additional ring is provided for the distribution of reference optical signals from a reference laser source.
  • the additional ring serves to distribute reference optical signals thi'oughout the Metro Network 1100 to aU access networks 1301, 1303, 1305.
  • the reference laser source is, in the illustrative embodiment, co-located with a system control unit 1360.
  • the reference optical signals are distributed via a ring network 1370.
  • the reference optical signals are coupled to each access network 1301, 1303, 1305 via an optical coupler 1371, 1373, 1375, respectively.
  • the optical output of each coupler 1371, 1373, 1375 is distributed to each optical network processor via an optical ampUfier 1381, 1383, 1385.
  • the structure depicted in the illustrative embodiment of the invention is shown as a ring type distribution, the invention is equally applicable to other distribution structures such as, not by way of limitation but by way of example, star, mesh or point-to-point distribution arrangements.
  • Furfhemiore the distribution structure for the reference signals does not have to coixespond to the structure of the network. That is, because a ring distribution structure is used in the communications system, a ring distribution structure does not have to be used with the reference optical signal distribution, other distribution structures may be used including hybrid combinations of various distribution aixangements.
  • the reference laser source utilized in the illustrative embodiment includes a multiple wavelength laser. To assure adequate optical power levels are provided to each node coupled to the access networks 1301, 1303, 1305, a distribution network and power allocation aixangement is provided as shown in FIG. 2.
  • System control unit 1360 has co-located therewith a reference laser source 1362.
  • Optical reference signals from reference laser source 1362 are coupled to optical fiber ring 1370.
  • additional optical amplifiers 1382 are employed to maintain a power level of +10dBm for each wavelength. At the output of optical couplers 1371, 1373, 1375 the power level is a +0dBm.
  • Optical amplifiers 1381, 1383, 1385 raise the power level to +13dBm.
  • each optical amplifier 1381, 1383, 1385 may be disfricited at the access network level to one or more optical network processors, such as optical network processor 1335.
  • Optical couplers, such as optical coupler 1384 provide this distribution.
  • Optical coupler 1382 couples the output of amplifier 1381 to up to eight optical network processors, such as optical network processor 1335.
  • the power level for each wavelength of the reference laser signal at the input to the optical network processor 1335 is maintained at +3dBm.
  • a multiple wavelength laser is utilized as reference laser source 1362 to provide a reference optical signals for generation and assignment of optical channels that are dete ⁇ nined from selecting for each channel one wavelength of a plurality of optical wavelengths and one frequency of a plurality of optical modulation frequencies.
  • the number of wavelengths that are obtainable from a multiple wavelength laser source is M waveleiigtiis, where M is 32.
  • the number of optical modulation frequencies is O, where O is 128.
  • Each channel in the system of the iUustrative embodiment has a bandwidth of 155 mbs. In other embodiments of the invention higher or lower speed and bandwidths may be used. Also, in other embodiments of tiie invention, different numbers of channels, different numbers of wavelengths and different numbers of optical modulation frequencies may be utilized.
  • FIG. 3 the functionality of multiplexing and switching channels identified by wavelength and frequency is illustrated.
  • ⁇ j through ⁇ M frequencies F, ⁇ through F 0
  • the frequency-multiplexed wavelengths at the outputs of multiplexors 201 are multiplexed together at wavelength multiplexor/demultiplexor 203.
  • the multiplexed optical output of multiplexor/demultiplexor 203 is coupled to optical network 1101.
  • the multiplexor/ demultiplexer functions are changed to demultiplexing for received optical signals.
  • the optical signals received over optical network 1101 are first wavelength demultiplexed by multiplexor/demultiplexor 203 to wavelengths ⁇ t througli ⁇ M .
  • a multiplexor/demultiplexor 201 demultiplexes the frequencies Fj* through F 0 .
  • the multiplexor/demultiplexor 201, 203 provide switched multiplexing. For example, multiplexor/demultiplexor 203 to the left in FIG. 3 can switch any number of wavelengths onto optical network 1101
  • FIG. 4 illustrates a system control unit 1360 in block diagram fonn.
  • System control unit 1360 includes multiple wavelength laser 1362 that is coupled to optical amplifier 1363.
  • Optical amplifer 1363 couples wavelength laser 1362 to laser reference ring network 1370.
  • a network processing unit 1364 is provided to control and monitor operation of the supply of reference optical signals from multiple wavelength laser 1362 to the reference ring network 1370.
  • a wavelength sensing circuit 1366 is coupled to the output of optical amplifier 1363.
  • Optical amplifier 1363 provides sensing signals to network processing unit 1364 that permit network processing unit 1364 to adjust the output level of optical amplifier 1363 and to control multiple wavelength laser 1362.
  • Network processmg unit 1364 is coupled to network 1100 via an optical network processor 1368, an optical amplifier 1369 and an optical add/drop 1367.
  • Network processing unit 1364 receives requests for bandwidth and channel assignments from nodes coupled to the network 1101 and responds with the address of one or more allocated channels. The number of channels allocated to a node depends upon the bandwidth needed for handling the traffic.
  • Network processing unit 1364 includes one or more processors and associated memory. The processor units may be commercially available processors. Memory associated with the processor unit or units may be any commercially avaUable memory. 1.5
  • System control unit 1360 In processing requests for channel assignments is shown in FIG. 5.
  • System control unit 1360 constantly identifies which channels have been allocated and which channels are idle.
  • System control unit 1360 responds dynamically to requests for channels by selecting channels from the idle channels and allocating the channels as needed. When communication between users over a channel is complete, the channel is returned to the designated idle channel pool.
  • system control unit 1360 selects an idle channel to achieve maximum isolation with used channels, i.e., the channel is selected to have the max ⁇ num separation from channels in use.
  • the manner in which channels ai'e selected may utilize a selection algorithm or a weighting selection or other scheme for channel assignment.
  • a system node that needs to transmit info ⁇ nation via the network 1100 transmits a request to system control unit 1360 as indicated at step 501, for a channel.
  • the request also identifies the destination node or nodes.
  • network processing unit 1364 selects a channel from the pool of idle available channels, as indicated at step 503.
  • the channel address is assigned.
  • the channel address is identified by wavelength and modulation frequency.
  • network processing unit 1364 provides the designated channel identity to the fransmitting node and to the receiving node.
  • Network processing unit 1364 identifies the assigned channel as in use at step 507. Transmission and reception of information occurs at step 509.
  • network processing unit 1364 Upon completion of transmission by fransmitting node, network processing unit 1364 reclaims the channel and again assigns it to the pool of available channels at step 511. Communication of channel assignments to system nodes may be, accomplished in any one of a number of conventional channel assignment methods. In the illustrative embodiment of the invention, communication of channel assignments to nodes from SCU 1360 and from node to SCU 1360 is accomplished by use of dedicated control and communication channels.
  • FIG. 6 illustrates the operability of the multiplexing and switching provided in improved network of the invention.
  • an optical fiber network such as network 1101 is illustrated as a ring.
  • multiple wavelengths optical signals, ⁇ -, through ⁇ M are multiplexed together and disfricited via reference laser ring network 1370 to network nodes.
  • Chart 602 indicates the wavelengths that are available on reference laser ring network 1370.
  • a network node, identified as node 603 has requested that a channel be assigned.
  • System control unit 1360 allocates a channel. The allocated channel includes wavelength ⁇ z
  • a tuned optical wavelength filter 605 is utilized to select the wavelength ⁇ z assigned by the system control unit 1360.
  • Filter 605 couples optical channel signals at the wavelength ⁇ z over the optical fiber network 1101.
  • Chart 604 indicates that the output of the output of node 603 presented to network 1101 is a single wavelength.
  • Other nodes likewise transmit different wavelengtii channels over the network 1101 as indicated by the additional inputs to optical fiber network 1101.
  • Wavelength chart 606 illustrates that although each node may provide an optical signal at a single wavelength, optical fiber network 1101 carries multiple wavelengths.
  • System control unit 1360 has info ⁇ ed node 607 that it is assigned to receive communications from node 603 at wavelengtii ⁇ z
  • a tunable optical wavelength filter 609 is adjusted to select wavelength ⁇ z and provide the signal to a detector 611 that is used to extract information caixied by the optical signals.
  • Chart 608 indicates that the output of tunable optical wavelength filter 609 provides a single wavelength output.
  • Tunable output wavelength filters 605, 609 may be of a design described in the Uterature.
  • a phase modulated optical signal may be characterized in terms its wavelength ⁇ , its phase ⁇ , and its modulation frequency f. Recognizing this, the second embodiment of tiie invention utilizes phase modulated and delayed optical signals and defines each optical channel by a wavelengtii multiplex, a phase delay or coherence multiplex and a frequency multiplex.
  • the number of wavelength multiplexed is identified as "M”.
  • the number of phase or coherence multiplexed channels is identified as "N”.
  • the number of frequency-multiplexed channels is "O”.
  • the number of available channels that may be multiplexed together is 32 x 8 x 64 or 16,000 channels.
  • Each channel has a bandwidth of 155 mbs.
  • higher or lower speed and bandwidths may be used.
  • different numbers of channels, different numbers of wavelengths and different numbers of optical modulation frequencies may be utilized.
  • the architecture of the second embodiment of the invention is the same as shown in FIGs. 1 and 2.
  • the system control unit 1360 as shown in Fig. 4 and its operation as set forth with respect to FIG. 5 are substantially the same in the second embodiment.
  • the system and method of the second embod ⁇ nent of the invention utilize a phase multiplex/switch layer, a frequency multiplex/switch layer and a wavelength multiplex layer in addition to the wavelength multiplex/switch layer described in conjunction with FIG. 6.
  • phase multiplex/switch layer makes advantageous use of the fact that a single wavelength optical signal in optical fiber can cany multiple phases.
  • phase separation is provided through delay of the chamiel with respect to the reference chaimel.
  • phase recovery is provided at the receive end.
  • the phase- multiplexed chamiel can be separated and detected with an interferometer.
  • FIG. 7 the manner in which interferometer technology may be utihzed to provide phase multiplex/switching is illustrated. In the illustration, four phase channels are illustrated.
  • phase channels shown FIG. 7 is merely illustrative and is not to in any way be considered as limiting.
  • the transmit end is illustrated at 700 and the receive end is illustrated at 710.
  • Interconnecting transmit end 700 and receive end 710 is the optical fiber network 1101.
  • Light source 701 generates optical signals.
  • Phase delays Dl, D2, D3, D4 are created as shown at 703 to produce four phase multiplexed data channels.
  • the un-delayed optical signal 704 provides a reference that is shown as a shaded in pulse.
  • the phase-delayed signals 702 are phase modulated at 705 to encode data onto the signals.
  • the phase delayed optical signals appeal' on the optical network 1101 as shown at 707.
  • phase delay reversal is provided at 709.
  • the phase multiplexed reference signal is demultiplexed.
  • Interferometer techniques 711 are utilized to demodulate and decode the data that was transmitted via the optical signals.
  • signals are detected by phase amplitude based interferometer techniques, rather than by intensity based interferometer techniques, to get better sensitivity.
  • phase amplitude based interferometer techniques rather than by intensity based interferometer techniques, to get better sensitivity.
  • phase amplitude based interferometer techniques rather than by intensity based interferometer techniques, to get better sensitivity.
  • phase channels are caixied in the same wavelength. Switching between phase channels is done electro-optically within less than 0.1 microsecond to allow for fast packet switching. Channel
  • ⁇ isolation is enhanced by selection of phase, wavelength and modulation frequency.
  • FIG. 8 iUusfrates the frequency multiplex/switch layer implementation utilized in the invention.
  • Modulators 801 produce modulated optical signals at the individual optical carrier frequencies, F f through F 0
  • Combiner 803 combines the individual carrier frequencies onto the optical network 1100. As illustrated in spectral chart 804, combiner 803 combines all the carrier frequencies onto ti e network optical fiber 1101.
  • a divider 805 separates the frequency components, Fj through F 0 .
  • Demodulators 807 demodulate the optical signals.
  • FIG. 9 illustrates in block diagram form a modulator 801 and a demodulator 807.
  • modulator 801 data 903 to be fransmitted is combined in a mixer 905 with an IF signal produced by a RF source 901.
  • the resulting RF signal is applied to an RF filter 906 and driver 907 that provides appropriate filtering and driver buffering.
  • the particular configuration of RF filter 906 and driver 907 may be selected from any available configuration.
  • the output of RF driver 907 is supplied to modulator 909 to modulate an optical signal from a light source 911.
  • the optical signal from light source 911 is modulated by an RF signal at the modulation frequency coixesponding to the channel assigned for communication to the node at which the modulator 801 is located.
  • demodulator 807 receives optical signals.
  • Demodulator 807 includes a detector circuit 913.
  • Detector circuit 913 is set to detect optical signals at the channel frequency designated for communication from the node at which modulator 801 is located.
  • the output of detector 913 is coupled to a RF driver filter 915.
  • the output of the RF driver 915 is combined with an IF signal provided by RF source 917 in a mixer 919, filtered by filter 921 and provided as recovered data 923.
  • the RF source providing the IF signals may be a voltage controlled oscillator.
  • the IF signal is provided at the modulation frequency assigned to the particular chaimel.
  • FIG. 10 the functionality of multiplexing and switching channels identified by wavelength, phase and frequency is illustrated.
  • ⁇ , through ⁇ N of each wavelength, ⁇ through ⁇ M , frequencies F, ⁇ through F 0 , ai'e multiplexed by multiplexor/demultiplexors 201.
  • the frequency multiplexed signals for each of the phases at the outputs of multiplexors 201 are multiplexed together at phase multiplexor/demultiplexors 1021.
  • the frequency and phase-multiplexed signals for each wavelength are applied to wavelength multiplexor/demultiplexor 203.
  • the multiplexed optical output of multiplexor/demultiplexor 203 is coupled to optical network 1101.
  • the multiplexor/ demultiplexer functions are changed to demultiplexing for received optical signals.
  • the optical signals received over optical network 1101 ai'e first wavelength dem ⁇ ltiplexed by multiplexor/demultiplexor 203 to wavelengths ⁇ j through ⁇ M .
  • a coixesponding phase multiplexor/demultiplexor 1021 demultiplexes phases and for each phase a multiplexor/demultiplexor 201 demultiplexes the frequencies F, through F 0 .
  • Each multiplexor/demultiplexor is bi-directional in that it will switch or multiplex one or more signals into a single stream and that it will demultiplex or switch signals out of a combination sfream.
  • each channel Since each channel has a unique wavelength, phase and modulation frequency coixelation, it can be identified by a unique address that references its wavelength, phase and frequency.
  • each chamiel may be particularly identified by a chamiel identity in which the wavelength is assigned a number of from 1 to M, each phase is assigned a number of from 1 to N and each modulation frequency is assigned a number from 1 to O.
  • the channel identity for each chaimel may be referred to as z y f x ,where "z" is the wavelength number, "y” is the phase number and "x" is the frequency nmnber. This channel identity is selected for convenience and clarity in description only and is not in any way intended to limit the invention.
  • FIGs. 11 and 12 iUustrate the exchange of data between two network nodes as represented by optical network processors ONP#l and ONP#50.
  • ONP#l request a channel allocation from system control unit 1360.
  • System control unit 1360 selects a channel from the idle channels available and allocates the selected channel in response to the request.
  • the channel is removed from the grouping of idle channels available, hi this instance, an exemplary idle channel identified as chaimel ⁇ 2 ⁇ 8 F 4 is selected for transmission of data from ONP#l to ONP#50, and the channel identification is provided to both the fransmit and receive optical network processors ONP#l and QNP#50. As shown in FIG.
  • ONP#l inserts data, D ⁇ x into the designated channel ⁇ 2 ⁇ 8 F 4 .
  • ONP#50 receives the modulated signal and extracts the data D RX from channel ⁇ 2 ⁇ 8 F 4 .
  • system control unit 1360 Upon completion of the data transmission to ONP#50, system control unit 1360 returns the channel assigmnent of channel ⁇ 2 ⁇ g F 4 to the pool of unassigned or idle channels for reassignment. Subsequently, the node at which ONP#50 is located may request a channel assignment from system control unit 1360.
  • System control unit 1360 assigns a channel form the pool of available idle channels. In this instance channel ⁇ 4 ⁇ 3 F 6 is assigned. ONP#50 fransmits and ONP#l receives data in the assigned channel. Upon completion of the data transmission, the channel is reassigned by system control unit 1360 to the pool of idle channels.
  • each network node includes an optical network processor ONP that includes a modulator and a demodulator as described above.
  • Each ONP is coupled to the laser reference source 1362 via the laser reference network 1370 as shown in FIG. 1.
  • Each ONP is coupled to the optical fiber network 1101 via an optical add/drop OAD and an optical amplifier EDFA.
  • FIGs. 14 and 15 depict a transmitter portion and a receiver portion of an optical network processor particularly well adapted for use with the above described first embodiment of the invention.
  • FIGs. 16 and 17 depict a transmitter portion and a receiver portion of an optical network processor particularly well adapted for use with the above described second embodiment of the invention.
  • Each optical network processor includes a transmit function and a receive function.
  • the receive function decodes data from a systems communications channel assigned for coimnunications to a node coupled to tiie optical network processor to control the associated wavelength multiplex/switch, phase multiplex/switch and frequency multiplex/switch.
  • the transmit function converts data from an associated node to an assigned system communications channel by controlling the associated wavelength multiplex/switch; phase multiplex/switch and frequency multiplex/switch.
  • Transmitter portion 1400 of an optical network processor includes one or more processors or micro controllers 1401 that provides program control of operation of the optical network processor. For clarity only one processor is shown for each optical network processor, but more than one processor may be used.
  • Transmitter portion 1400 is coupled to laser reference network 1370 and receives signals from the multiple wavelength signals from laser reference source 1360.
  • a polarization controller 1403 under control of micro controller 1401 selects polarization of the received laser signals.
  • the output of polarization controller 1403 is coupled to tunable filter 1407.
  • a depolarizer replaces polarization controller 1403.
  • Micro controller 1401 receives channel allocation ⁇ ifonnation and utilizes the channels allocation information to select a wavelength and frequency for its associated node to transmit data.
  • Micro controller 1401 via wavelength tuning module 1405 operates tunable filter 1407.
  • Wavelength timing module 1405 selects a wavelength in response to micro controller 1401 providing a wavelength select signal.
  • Tunable filter 1407 is tuned to the selected wavelength.
  • Tunable filter 1407 thereby selects the wavelength optical signal for transmitting data under control of micro controller 1401.
  • the output of tunable filter 1407 is coupled to a Mach-Zehnder interferometer 1413.
  • Inteiferometer 1413 includes two legs coupled at the input to a coupler 1409 and at the output by coupler 1419.
  • a first leg includes dc bias module 1412 and a phase modulator 1416.
  • a second leg includes dc bias module 1414 and a phase modulator 1418.
  • Micro controller 1401 provides quadrature control of inteiferometer 1413 via bias control module 1411. Quadrature control ensures stable linear operation of the interferometer 1413.
  • Frequency selection is provided via micro controller 1401 controlling voltage-controlled oscillator 1415 that in turn provides a selected modulation frequency to rnixer/diiver module 1417.
  • Mixer/driver module 1417 mixes the modulation frequency output of voltage-controlled oscillator 1415 with Transmit data D ⁇ x .
  • FIG. 15 depicts optical network processor receive portion 1500.
  • Receive portion 1500 of an optical network processor includes a processor or micro controller 1501 that provides ' program control of operation of the optical network processor.
  • Receive portion 1500 is coupled to network 1101 and receives signals from another network node.
  • Micro controller 1501 receives channel assignment info ⁇ nation from SCU 1360 and utilizes the channel assignment to select the wavelength and fi'equency of a channel canying data for its associated node.
  • a polarization controller 1503 under control of micro controller 1501 selects polarization of the received laser signals.
  • a depolarizer replaces polarization controller 1503.
  • the output of polarization controller 1503 is coupled to tunable filter 1507.
  • module 1505 operates tunable filter 1507.
  • Wavelength tuning module 1505 selects a wavelength in response to micro controller 1501 providing a wavelength select signal.
  • Tunable filter 1507 selects the wavelength of a receive channel under control of micro controller 1501.
  • a coupler 1509 couples the output of tunable filter 1507 to a Mach-Zehnder Interferometer 1513.
  • Interferometer 1513 includes two legs.
  • a first leg includes dc bias module 1512 and a phase modulator 1516.
  • a second leg includes dc bias module 1514 and a phase modulator 1518.
  • Interferometer 1513 is not used as an interferometer in the receiver. Only the dc bias modules 1512 and 1514 are used in the receive function. Phase modulators 1516, 1518 are left unused in this receiver implementation.
  • Micro controller 1501 provides quadrature confrol via bias confrol module 1511. Frequency selection is provided via micro controller 1501 controlling voltage-controlled oscillator 1515 that in turn provides a selected frequency to mixer/driver module 1517.
  • the outputs of interferometer 1513 are applied to coupler 1519.
  • the output of coupler 1519 is in turn applied to tunable filter 1521 which is controlled by micro controller 1501 via wavelength tuning module 1505.
  • the wavelength-selected output of tunable filter 1521 is in turn applied to detector 1523.
  • Detector 1523 provides a quadrature dc output, which is provided to micro controller 1501 for use in controlling bias confrol circuit 1511.
  • An RF output of detector 1523 is provided to amplifier 1525.
  • Output of amplifier 1525 is coupled to a second input of rnixer/diiver 1517.
  • An output of mixer/driver 1517 is applied to low pass filter 1529.
  • the output of low pass filter 1529 provides data output signals D ⁇ that are provided to a network node such as user 1331.
  • the design of the optical network processor receive portion and transmit portion share similar basic design components in the implementations shown.
  • the transmit portion and receive portions in one embodiment are implemented on two separate chips for full duplex operation.
  • a bi-directional, half-duplex design combines both transmit and receive portions in a single integrated optic chip using reflective design.
  • Advantages of the second embodiment are that the length of the integrated optic chip is shortened by Vr, cost is reduced; and transmit and receive portions are combined into one design.
  • perfonnance of the wavelength filter is greatly enhanced for double pass operation. Sidelobe suppression of 15dB for one pass through the filter increases to 30dB with double pass operation. Still further, the drive voltage of the modulator is reduced 50%.
  • FIG. 16 depicts a transceiver 1600 in which a single integrated optic chip 1670 is utilized advantageously.
  • Transceiver 1600 is coupled to network HOlvia a circulator 1604.
  • Transceiver 1600 is also coupled to laser reference ring 1370 via circulator 1604 and an isolator 1602 interposed in reference laser ring 1370.
  • Circulator 1604 is coupled to integrated optic chip 1670 via a polarization controller or scrambler 1603.
  • Integrated optic chip 1670 includes a TM polarizer 1651 coupled to a tunable filter 1652.
  • Micro controller 1601 receives transmit and receive channel assignment information from system control unit 1360 and utilizes the channel assignment info ⁇ nation to select wavelengths and frequencies for transmit or receive functions.
  • Micro controller 1601 via a wavelength-tuning module 1605, controls tunable filter 1652.
  • a TE polarizer 1653 follows tunable filter 1652 to remove unwanted signals.
  • a 2 x 2 coupler 1654 is disposed between TE polarizer 1653 and interferometer 1613, Interferometer 1613 includes optical bias modulators 1612, 1614.
  • Phase modulators 1616, 1618 follow optical bias modulators 1612, 1614.
  • Reflection mirrors 1662,1660 are provided on the end of integrated optic chip 1670. The operation of ti e various circuit elements shown in Fig.
  • FIG. 16 depicts a transmitter portion 1700 of an optical network processor for use in the above-described second embodiment of the invention.
  • Transmitter portion 1700 includes " a processor or micro controller 1701 that provides program control of operation of fransmitter portion 1700.
  • Micro controller 1701 receives channel assignment infb ⁇ nation from system control unit 1360 and utilizes that information to select wavelength, phase and frequency of assigned channels.
  • Transmitter portion 1700 is coupled to laser reference network 1370 and receives multiple wavelength signals from laser reference source 1360.
  • a polarization controller 1703 under confrol of micro controller 1701 selects polarization of the reference laser signals.
  • the output of polarization controller 1703 is coupled to tunable filter 1707.
  • Micro controller 1701 via wavelength tuning module 1705 controls tunable filter 1707.
  • Wavelength tuning module 1705 selects a wavelength in response to micro controller 1701 providing a wavelengtii select signal.
  • Tunable filter 1707 selects the wavelength optical signal for fransmitting data under control of micro controller 1701.
  • a coupler 1709 couples the output of tunable filter 1707 to phase selector for selecting one out of "N" phases.
  • the phase selector includes a 1 x n switch 1771 that is controlled by micro controller 1701. Each of the N outputs of switch 1771 is coupled to a coixesponding phase modulator 1775.
  • Micro controller 1701 controlling a voltage-controlled oscillator 1715 provides frequency selection. The selected frequency output of voltage controlled oscillator 1715 is combined with data to be transmitted D ⁇ x by mixer/driver 1717. The data D ⁇ x to be transmitted is received from a user node 1331.
  • a filter/switch module 1770 under confrol of micro controUer 1701 * provides tiie output of rnixer/diiver 1717 to the N phase modulators 1775.
  • Each phase modulator 1775 is coupled to a phase delay module 1777.
  • the outputs of the phase delay modules are the N phases 1 through N Switch 1779 under control of micro controller 1701 selects the output phase.
  • the output of filter 1721 is the wavelength/frequency /phase selected optical signals modulated with transmit data and is coupled to optical network 1101. A portion of the output is coupled to a detector 1723 that provides a dc feedback signal to micro controller 1701.
  • FIG. 18 depicts optical network processor receive portion 1800 for the above described second embodiment.
  • Receive portion 1800 includes a processor or micro controller 1801 that provides program controlled operation of optical network processor receive portion.
  • micro controller 1801 receives channel assignment infoimation from system confrol unit 1360 and utilizes that infoimation to select channel wavelength, phase and frequency to select a desired channel for recovery of received data. The received data is provided to a node 1331.
  • Micro controller 1801 generates wavelengtii select, phase select and frequency select signals.
  • the frequency select signals confrol a voltage-controlled oscillator 1815 to provide a fi'equency-selected signal to a mixer/ driver circuit 1817.
  • the output of rnixer/diiver 1817 is filtered by filter 1840 to provide output data signals D ⁇ x .
  • Receive portion 1800 is coupled to network 1101 and receives optical signals carrying data D ⁇ x from another node coupled to network 1101.
  • a depolarizer 1803 depolarizes the optical signals received via network 1101.
  • depolarizer 1803 may be replaced with a polarization controller controlled by micro controller 1801.
  • the output of depolarizer 1803 is coupled to tunable filter 1807.
  • Micro controller 1801 via wavelength tuning module 1805 operates tunable filter 1807.
  • Wavelength Inning module 1805 selects a wavelengtii in response to micro controller 1801 and tunes filter 1807 to the selected wavelength.
  • Phase selection is accomplished by micro controller 1801 providing phase select signals to control switches 1871 and 1879.
  • Switches 1871 and 1879 are used to select one phase delay path from a group of "n" phase delay, where "n” is the number of selectable phases.
  • Each phase delay path includes aphase modulator 1875 and a phase delay circuit 1877.
  • Micro controller 1871 via bias control 1811 controls phase modulators 1875.
  • the output of the selected phase path is coupled via switch 1879 to coupler 1819.
  • a phase reference signal is coupled from signals received from network 1101 from coupler 1871 to coupler 1919 via optical connection 1873.
  • Coupler 1819 combines the phase reference signal from connection 1873 with the output of phase switch 1879.
  • the combined output is applied to wavelength filter 1821 that is tuned to the wavelength selected by micro controller 1801.
  • tunable filter 1821 is coupled to detector 1823 that separates an RF signal and a dc servo feedback signal.
  • the RF signal is applied to mixer/driver 1817 via pre amplifier 1880.
  • AU of the components shown within box 1881 may be fabricated on a single integrated optic chip using reflective design.
  • FIG. 19 is a block diagram of a transceiver 1900 in which economies are achieved by utilizing the commonality of receive and transmit portions, 1800, 1700.
  • Transceiver 1900 receives data D ⁇ x from a node 1331 and provides data D RX to a node 1331.
  • Transceiver 1900 is coupled to optical network 1101 and reference network 1370 by circulator 1940.
  • a micro controller 1901 provides progi'am controlled operation of fransmit and receive functions.
  • micro controller 1901 provides wavelength, phase and frequency selection to select a desired channel for recovery of received data and providing the received data to a node 1331 and for receipt of transmit data from node 1331 for transmission over network 1101.
  • Micro controller 1901 generates wavelength select, phase select and frequency select signals for fransmit and receive.
  • the frequency select signals control a voltage-controlled oscillator 1915a to provide a frequency-selected signal to a mixer/driver circuit 1917a.
  • the output of mixer/driver circuit 1917a is filtered by low pass filter 1940 to provide output data signals D ⁇ .
  • Frequency select signals from micro confroUer 1901 ai'e used for transmission of data from a node 1331 over network 1101.
  • Frequency select signals control voltage controlled oscillator 1915 to select a desired transmit channel frequency.
  • a mi er/diiver 1917 combines the output of voltage-controlled osciUator 1915 and D ⁇ x .
  • the modulated frequency signals are applied to filter switch 1970.
  • Micro controller 1901 also controls phase and wavelength selections. Phase selection is provide by micro confroUer 1910 providing phase selection signals to a phase control module 1972, bias confrol signals to bias confrol circuit 1911 and filter confrol signals to filter switch 1970. For fransmit data, filter switch 1970 is active but bias control 1911 is not.
  • Integrated optical chip assembly 1981 provides wavelength selection and phase multiplex selections. Integrated optical chip assembly 1981 utilizes reflective multiplex teclmology. Double pass operation of the integrated optical chip assembly 1981 greatly enhances performance of the wavelength filter operation.
  • phase selection circuit may be expanded to inore phase channels, but for purposes of drawing clarity, only a four-phase channel selection structure is shown.
  • micro controller 1901 provides wavelength selection signals to wavelength tuning module 1905.
  • Wavelength tuning module 1905 controls tunable filter 1983 to select the wavelength channel for fransmit and receive.
  • micro confroUer 1901 controls filter switch 1970 to control the phase modulator aixay 1987.
  • micro controller 1901 controls bias confrol 1911 to in turn control bias modulator aixay 1986.
  • filter switch 1970 is used to select a phase and couple the output of mixer/driver 1917 via coupler 1909 through polarizer 1983, wavelengtii filter 1983, polarizer 1982 to depolarizer 1903 and to network 1101 via cfrculator 1940.
  • optical signals received from network 1101 are coupled via cfrculator 1940 through depolarizer 1903 to polarizer 1982, tunable filter 1983, polarizer 1984 to the phase selector.
  • Bias confrol module 1911 under confrol of micro controller 1901 sets the bias to a quadrature point to stabilize the receive phase channel.
  • the output of the phase selector is coupled to detector 1923.
  • Detector 1923 provides an RF output to preamplifier 1980.
  • Preamplifier 1980 is coupled to mixer/driver 1917, and its output is filtered by low pass filter 1940 to provide output data to node 1331.
  • Each laser source may be assembled together to provide a laser reference source useable in the optical networks and optical communication system of the invention.
  • Various laser sources may be employed; however, each laser source must have specific characteristics.
  • multiple wavelength lasers that have high launch power are desirable.
  • the reference provides optical signals for each wavelength channel at levels greater than 10 mw for each wavelength channel.
  • Each laser source should desirably meet this requirement.
  • nonlinear effects such as self phase modulation (SPM), stimulated Brillion scattering (SBS) and four wave mixing be lninimized.
  • SPM self phase modulation
  • SBS stimulated Brillion scattering
  • a short coherence length of less than 5mm should be provided for phase multiplex/switch ⁇ ig operation.
  • wavelength stability is to be controlled within 20 Pico meters. It is des ⁇ able that spurious spectral components be minimized between wavelength channels.
  • Embodiments are shown and described that utilize disfricited feedback lasers and Erbium Doped Fiber Lasers. High launch power, short coherence length, minimized SBS/SPM effects and non-linear effects ai'e avoided by the use of Erbium Doped Fiber Lasers (EDFL).
  • Spectral width broadening is achieved by phase modulating the naixow line width distributed feedback (DFB) lasers with high frequency radio frequencies. Stable wavelengths are achieved by active wavelength measurement and control. High spectral purity is obtained by use of fiber gratings to remove noise between wavelength channels. At least up to 32 wavelengtii channels can be implemented in each embodunent.
  • DWDM multiplexmg is utilized. DWDM multiplexing provides a low loss multiplexing. Fiber coupler arrays can provide the same functionality but with higher loss.
  • FIG. 20 depicts one embodiment of a multiple wavelength reference laser source in which multiple distributed feedback (DFB) lasers ai'e used.
  • DFB distributed feedback
  • a plurality of DFB lasers 2001 is utilized.
  • a separate DFB laser 2001 is used to generate each wavelength l through M .
  • DFB lasers There are two limitations on DFB lasers that need to be accommodated. Ffrst, the output of each DFB laser 2001 typically has a naixow tinewidth of less than 50 MHz. This spectral width shown as spike 2002 is too naixow for use in the embodiments of the ⁇ vention described above. Second, the coherence length of each DFB laser 2001 output is too large for appUcation in the embod ⁇ nents of the present invention.
  • Phase modulating the output of each DFB laser 2001 with an RF signal broadens the spectral width of the output and further can reduce tiie coherence length. In other words, for optimum perfonnance, the laser signals cannot be too coherent and cannot have too naixow a tine width in the above-described embodiments.
  • a plurality of phase modulators 2003 is provided. Each phase modulator 2003 is coupled to a corresponding one of the DFB lasers 2001. Modulation is with an RF signal having multiple frequency components that ai'e selected in the RF range of a veiy low frequency to an upper frequency of 20 GHz. In the embodiment shown, the range is 0.01 to 20.0 GHz.
  • Modulation with a multiple component RF signal produces a laser signal having a broad linewidth output of gi'eater than 20 GHz as illustrated by waveform 2004.
  • the phase modulation reduces the coherence length.
  • the phase modulators produce polarization rotation to depolarize the signals.
  • a plui'ality of fiber gratings 2005 shapes the output spectrum and coherence. More specifically fiber gratings 2005 are utilized to remove the side lobes of the output waveforms of phase modulators 2003.
  • Each modulated DFB laser 2001 output is filtered to remove side lobes by a coixespondmg one of the fiber gratings 2005 to shape the modulated laser output spectrum.
  • a DWDM multiplexer 2007 is utUized to combine the outputs of each of the DFB lasers 2001.
  • the combined output of DWDM multiplexor 2007 is shown as waveform 2006.
  • An amplifier 2009 is coupled to the output of the DWDM multiplexor and amplifies the multiple wavelengtii laser output to produce an amplified output shown as wavefoixn 2008.
  • Amplifier 2009 is an erbium doped fiber amplifier, EDFA.
  • FIG. 21 illustrates an alternate embodiment of a Multiple Wavelength Laser.
  • the multiple wavelength laser source of FIG. 20 is modified.
  • a plurality of DFB lasers 2001 is utilized.
  • a separate DFB laser 200 l is used to generate each wavelength ⁇ through M .
  • each DFB laser 2001 output is too large for application in the embodiments of tiie present invention.
  • phase modulating the output of each DFB laser 2001 with an RF signal broadens the spectral width of the output and further can reduce the coherence length.
  • a plurality of phase modulators 2003 is provided. Each phase modulator 2003 is coupled to a corresponding one of the DFB lasers 2001. Modulation is with an RF signal hav ⁇ ig multiple frequency components that are selected in the RF range of 0.01 to 20.0 GHz. Modulation with a multiple component RF signal produces a laser signal having a broad linewidth output of gi'eater than 20 GHz as illustrated by wavefoixn 2004.
  • phase modulated laser signals at the different wavelengths are each amplified by one of a plui'ality of EDFA amplifiers 2101 to produce amplified wavefoims 2010 prior to be ⁇ ig shaped by fiber gratings 2005.
  • Each EDFA 2101 is coupled to the output of a corresponding one of the phase modulators 2003.
  • By amplifying each wavelength component prior to combining the wavelength components, as shown by wavefoixn 2010, before combimng the waveforms it is possible to achieve a combined output from DWDM multiplexor 2007 in which the wavelength components ai'e more unifoim. In addition, higher output levels may be achieved.
  • phase modulators provide depolarizing.
  • the phase modulators 2003 rotate linear input polarization signals to produce output c ⁇ cular polarization state signals. High power radio frequency signals ai'e utilized to achieve full rotation.
  • Each of the phase modulators 2003 is a high-speed phase modulator.
  • FIG. 22 illustrates a thfrd embodiment of a multiple wavelength laser source that may be used in accordance with the invention.
  • a plui'ality of separate Erbium Doped Fiber Lasers (EDFL) 2201 are used as sources.
  • Each EDFL 2201 is designed to have appropriate spectral width and coherence function with a coherence length of less than 5 mm.
  • Each EDFL 2201 provides an output at one of a plurality, m, of wavelengths j - m .
  • Wavelength confrol teclmology is used with each EDFL 2201 to control emission wavelength.
  • Each EDFL 2201 provides a single wavelength output.
  • a plurality of fiber gratings 2203 are used to provide output spectrum shaping and coherence function.
  • Each grating 2203 is selected to conform to one of the wavelengths 1 ⁇ 2 ,- m .
  • a plui'ality of EDFAs 2205 are coupled to the outputs of gratings 2203, with a one to one coixespondence between each EDFA 2205 and a coixespondmg one grating 2203.
  • Each EDFA 2205 amplifies a coixespondmg grating 2203 output j, 2 ,- m .
  • a DWDM multiplexer 2207 is used to comb ⁇ ie the outputs l5 2 ,- m to produce a multiple wavelength laser output 2211 that contains all the wavelengths j - m .
  • EDFLs 2201 phase modulation is not necessary because each EDFL has a broad line width and the coherence length is not too short.
  • fiber gratings 2203 Through selection of appropriate fiber gratings 2203 the desfred spectral response is achieved.
  • FIG. 23 An alternative EDFL based design for the multiple wavelength laser reference is illustrated in FIG. 23.
  • a single EDFA amplifier 2301 is utilized to amplify the combined output.
  • a filter 2303 is used to shape the amplified multiplexed output. More specifically, as in the embodunent of Fig. 22, a plui'ality of sepaiate Erbium Doped Fiber Lasers (EDFL) 2201 are used as sources.
  • EDFL Erbium Doped Fiber Lasers
  • Each EDFL 2201 is designed to have appropriate spectral width and coherence function with a coherence length of less than 5 mm.
  • Each EDFL 2201 provides an output at one of a plurality, m, of wavelengths ⁇ - m .
  • Wavelength confrol technology is used with each EDFL 2201 to control emission wavelengtii.
  • Each EDFL 2201 provides a single wavelength output.
  • a plurality of fiber gratings 2203 are used to provide output spectrum shaping and coherence function. Each grating 2203 is selected to conform to one of the wavelengths l5 2 ,- m .
  • a DWDM multiplexer 2207 is used to combine the outputs vom 2 ,- m to produce a multiple wavelengtii laser output 2211 that contains all tiie wavelengths ! - m .
  • An EDFA 2301 is coupled to the outputs of DWDM multiplexer 2207 and amplifies the combined output hav ⁇ ig all wavelength components ,, 2 ,- m .
  • Filter 2303 is used to shape the amplified multiplexed output to produce the multiple wavelength laser output 2311.
  • FIGs. 24 and 25 illustrate EDFLs suitable for application to the laser reference sources depicted in FIGs. 22 and 23.
  • an erbium-doped fiber 2401 is pumped from a laser pump source 2407 through a WDM 2409.
  • Each erbium-doped fiber 2401 is coupled at either end to a fiber grating.
  • both gratings 2403 and 2405 are reflecting naixow-band gratings at the same wavelength.
  • naixow-band fiber grating 2403 is replaced with a broadband reflecting grating 2501 or alternatively, a mirror.
  • WDM 2409 couples the pump source 2407 output to fiber grating 2405.
  • An isolator 2411 is used at the output of the EDFL
  • FIG. 26 depicts an optical add/drop 1307 that is utilized to particular advantage in the embodiments of the invention described above.
  • FIG. 26 also shows further details of a typical EDFA construction, such as EDFA 1313.
  • The, design shown is for a reciprocal optical add/drop inserted into optical link network 1101.
  • Optical add/drop 1307 utilizes three couplers 2603, 2605, 2607 and two isolators 2609, 2611 all of which are known in the art and are commercially available.
  • Optical add/drop 1307 includes a first bi-d ⁇ ectional port PI, a second bi-dfrectional port P2 and a thfrd bi-dfrectional port P3.
  • Bi-dfrectional ports P 1 and P2 are connected to optical link network 1101 and bi-dfrectional port P3 is coupled to an optical network processor or coupler via bi-dfrectional amplifier 1313.
  • Drop signals from optical link network 1101 are coupled from coupler 2605 to coupler 2607 and to, isolator 2611.
  • Isolator 2611 couples the optical signals to amplifier 1313.
  • Coupler 2607 is utilized to pe ⁇ nit the bi- dfrectional drop and add of optical signals.
  • couplers 2603 and 2605 are chosen in the illustrative embodiment such that 5% of the optical signal is coupled to an add/ drop path and 95% of the optical signal is passed on the through path of the coupler.
  • Coupler 2607 is chosen such that 50% of the signal is coupled from one path to the other.
  • Isolators 2609, 2611 ai'e used to provide dfrectionality for the add and drop paths to the ONP or coupler.
  • Amplifier 1331 comprises an EDFA 1313a for amplifying input signals and an EDFA 1313b for amplifying output signals.
  • a cfrculator 1313c having three ports cl, c2, c3 is used to couple both EDFAs 1313a, 1313b to tiie optical network processor or coupler.
  • Drop signals from PI are extracted via coupler 2603 and ai'e coupled via coupler 2607 to isolator 2611, amplified by EDFA 1313b, applied to cfrculator 1313c at its port c2 and extracted from c ⁇ culator at port c3 which is connected to an optical network processor at port P3.
  • Optical signals at port P2 . are coupled by coupler 2605 to coupler 2607 and processed as described above.
  • the output in this add path is applied to coupler 2607 provides 50% of the add signal to each of couplers 2603, 2605. Because the same level of signals are achieved in transmission of signals from ports PI to P2 as are achieved from ports P2 to PI and between any comb ⁇ iation of pafrs of the three ports PI, P2, P3, the optical add/drop in this embodunent may be characterized as a reciprocal add/drop.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention concerne un appareil et des procédés destinés au fonctionnement d'un système (1100, 1200) de communications optiques. On utilise une source laser (1360) à longueurs d'ondes multiples afin d'obtenir des signaux de synchronisation pour le système. La source laser comprend plusieurs lasers à rétraction répartie (DFB). La sortie de chaque laser est modulée en phase, et les sorties modulées en phase sont multiplexées ensemble et amplifiées.
PCT/US2001/003694 2000-02-23 2001-02-22 Source laser a longueurs d'ondes multiples WO2001063802A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001274797A AU2001274797A1 (en) 2000-02-23 2001-02-22 Multiple wavelength laser source

Applications Claiming Priority (18)

Application Number Priority Date Filing Date Title
US51156000A 2000-02-23 2000-02-23
US51069300A 2000-02-23 2000-02-23
US09/511,053 2000-02-23
US09/510,693 2000-02-23
US09/510,685 US6587239B1 (en) 2000-02-23 2000-02-23 Optical fiber network having increased channel capacity
US09/510,685 2000-02-23
US09/511,053 US6583901B1 (en) 2000-02-23 2000-02-23 Optical communications system with dynamic channel allocation
US09/511,560 2000-02-23
US64448800A 2000-08-23 2000-08-23
US64443300A 2000-08-23 2000-08-23
US64392600A 2000-08-23 2000-08-23
US64447500A 2000-08-23 2000-08-23
US09/644,475 2000-08-23
US09/644,488 2000-08-23
US09/644,433 2000-08-23
US09/643,926 2000-08-23
US77682101A 2001-02-05 2001-02-05
US09/776,821 2001-02-05

Publications (2)

Publication Number Publication Date
WO2001063802A1 true WO2001063802A1 (fr) 2001-08-30
WO2001063802A9 WO2001063802A9 (fr) 2002-11-07

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5894362A (en) * 1995-08-23 1999-04-13 Fujitsu Limited Optical communication system which determines the spectrum of a wavelength division multiplexed signal and performs various processes in accordance with the determined spectrum
US5953139A (en) * 1996-03-06 1999-09-14 Cfx Communications Systems, Llc Wavelength division multiplexing system
US6005702A (en) * 1996-02-23 1999-12-21 Kokusai Denshin Denwa Kabushiki-Kaisha Optical transmission device, WDM optical transmission apparatus, and optical transmission system using return-to-zero optical pulses

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5894362A (en) * 1995-08-23 1999-04-13 Fujitsu Limited Optical communication system which determines the spectrum of a wavelength division multiplexed signal and performs various processes in accordance with the determined spectrum
US6005702A (en) * 1996-02-23 1999-12-21 Kokusai Denshin Denwa Kabushiki-Kaisha Optical transmission device, WDM optical transmission apparatus, and optical transmission system using return-to-zero optical pulses
US5953139A (en) * 1996-03-06 1999-09-14 Cfx Communications Systems, Llc Wavelength division multiplexing system

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