United States Patent [19]
`Mizrahi
`
`US006069719A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,069,719
`May 30, 2000
`
`[54] DYNAMICALLY RECONFIGURABLE
`OPTICAL ADD-DROP MULTIPLEXERS FOR
`WDM OPTICAL COMMUNICATION
`SYSTEMS
`
`[75] Inventor: Victor Mizrahi, Columbia, Md.
`
`[73] Assignee: Ciena Corporation, Linthicum, Md.
`
`[21] Appl. No.: 08/902,810
`[22]
`Filed:
`Jul. 30, 1997
`
`[51] Int. Cl.7 .................................................... .. H04J 14/02
`[52] US. Cl. ........................ .. 359/124; 359/127; 359/128;
`359/130
`[58] Field of Search ................................... .. 359/124, 127,
`359/128, 129, 130, 131; 385/37
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,612,805
`5,712,932
`5,715,076
`5,748,815
`5,760,934
`5,778,118
`
`3/1997 Fevrier et al. ........................ .. 359/128
`1/1998 Alexander et al.
`359/127
`2/1998 Alexander et al.
`359/130
`5/1998 Hamel et al.
`359/130
`6/1998 Sutter et al. ..
`359/127
`7/1998 Sridhar .................................. .. 359/130
`
`OTHER PUBLICATIONS
`
`Toba, H., et al.; “An Optical FDM—Based Self—Healing Ring
`Network Employing Arrayed WaveGuide Grating Filters
`and EDFA’s with Level Equalizers”; pp. 800—813; IEEE
`Journal on Selected Areas in Communications, vol. 14, No.
`5, Jun. 1996.
`Toba, H., et al.; “Demonstration of Optical FDM Based
`Self—Healing Ring Network Employing Arrayed—
`WaveGuide—Gratting ADM Filters and EFDA ”; pp.
`263—266; Optical Communication (EC, FirenZe, Sep. 25—29,
`1994) vol. 1, No. CONF. 20, Sep. 1994.
`
`Kitayama, K. —I; “Subarrier Multiplexing Based Signaling
`and Access Control in Optical FDM Networks”; pp.
`1996—2002; Telecommunications Conference, Singapore,
`Nov. 14—16, 1995, vol. 3, Nov. 1995.
`Tachikawa, Y., et al.; “Arrayed—WavGuide Grating Multi
`plexer with Loop—Back Optical Paths and its Applications”;
`pp. 977—984; Journal of Lightwave Technology, vol. 14, No.
`6, Jun. 1996.
`Beer, J.; “Photonische TransportnetZe”; pp. 20—24; Tech
`nische Rundschau Transfer, vol. 88, No. 14, Apr. 1996.
`Chawki, M. J., et al.; “Evaluation of an Optical Boosted
`Add/Drop Multiplexer OBADM Including Circulators and
`Riber Grating Filters”; pp. 47—50; Proceedings of the Euro
`pean Conference on Optical Communication, vol. 1, Sep.
`1995.
`Noti?cation of Transmittal of The International Search
`Report or The Declaration, 6 pages.
`
`Primary Examiner—Daniel J. Wu
`Assistant Examiner—John Tweel, Jr.
`Attorney, Agent, or Firm—David L. SoltZ; Margaret Burke
`
`[57]
`
`ABSTRACT
`
`In an optical add/drop multiplexer, an optical switch is
`coupled to one or more outputs from a demultiplexer.
`Accordingly, a dropped optical channel can be switched
`between a receiver optical path for directing the dropped
`optical signal to an optical receiver and between a combiner
`optical path for routing the dropped optical channel back
`towards the optical transmission path, optionally passing the
`dropped optical channel through a remodulator.
`Alternatively, the optical switch routes the dropped optical
`channel towards an optical receiver while permitting a new
`optical channel to be routed to add port of the static add-drop
`multiplexer.
`
`10 Claims, 5 Drawing Sheets
`
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`Cisco Systems, Inc.
`Exhibit 1016, Page 1
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`

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`U.S. Patent
`
`May 30, 2000
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`Exhibit 1016, Page 2
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`Sheet 2 of 5
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`Cisco Systems, Inc.
`Exhibit 1016, Page 3
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`U.S. Patent
`
`May 30, 2000
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`Sheet 3 0f 5
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`Exhibit 1016, Page 4
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`Cisco Systems, Inc.
`Exhibit 1016, Page 5
`
`

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`U.S. Patent
`
`May 30, 2000
`
`Sheet 5 0f 5
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`6,069,719
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`Exhibit 1016, Page 6
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`

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`6,069,719
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`1
`DYNAMICALLY RECONFIGURABLE
`OPTICAL ADD-DROP MULTIPLEXERS FOR
`WDM OPTICAL COMMUNICATION
`SYSTEMS
`
`FIELD OF THE INVENTION
`The invention relates to optical add-drop multiplexers
`and, more particularly, to optical add-drop multiplexers for
`Wavelength division multiplexed optical communication
`systems Which are dynamically recon?gurable for transfer
`ring selected optical channels betWeen optical paths Within
`the optical system.
`
`10
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`BACKGROUND OF THE INVENTION
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`Wavelength division multiplexing (WDM) is one tech
`nique used to increase the capacity of optical communica
`tion systems. The expression “optical communication
`system,” as used herein, relates to any system Which uses
`optical signals to convey information across an optical
`Waveguiding medium. Such optical systems include, but are
`not limited to, telecommunications systems, cable television
`systems, and local area netWorks (LANs). Optical systems
`are described in GoWar, Ed. Optical Communication
`Systems, (Prentice Hall, NY) c. 1993, the disclosure of
`Which is incorporated herein by reference. A Wavelength
`division multiplexed optical communication system
`employs plural optical channels, each channel being
`assigned a particular channel Wavelength. In a WDM
`system, optical channels are generated, multiplexed to form
`an optical signal comprised of the individual optical
`channels, transmitted over a Waveguide, and demultiplexed
`such that each channel Wavelength is individually routed to
`a designated receiver. Through the use of optical ampli?ers,
`such as doped ?ber ampli?ers, plural optical channels are
`directly ampli?ed simultaneously, facilitating the use of
`Wavelength division multiplexing in long-distance optical
`systems.
`In many applications, such as optical LANs, cable tele
`vision subscriber systems, and telecommunications
`networks, there is a need to route one or more channels of
`a multiplexed optical signal to different destinations. Such
`routing occurs When optical channels are sent to or With
`draWn from an optical transmission line e.g., for sending
`optical channels betWeen a terminal and an optical bus or
`routing long distance telecommunications traf?c to indi
`vidual cities. Additionally, optical routing must be suf?
`ciently ?exible to enable a variety of system con?gurations,
`permitting optical signal paths to be recon?gured in
`response to changing traf?c pattern requirements. Thus,
`there is a need in the art for ?exible and effective optical
`routing to enable practical implementation of Wavelength
`division multiplexed optical communication systems.
`
`SUMMARY OF THE INVENTION
`The present invention provides a recon?gurable optical
`add-drop multiplexer for a Wavelength division multiplexed
`optical communication system. The recon?gurable add-drop
`multiplexer includes a static optical add-drop multiplexer
`including an input port for receiving optical signals from an
`optical transmission path in a Wavelength division multi
`plexed optical communication system, a drop port for rout
`ing optical channels to be removed from an optical trans
`mission path, an add port for receiving optical channels to be
`added to an optical transmission path, and Wavelength
`selecting means for selecting at least one optical channel to
`be dropped from the optical transmission path.
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`An optical path communicating With the drop port
`includes an optical demultiplexer having an input port for
`receiving the dropped optical channels and plural demulti
`plexer output ports for separately outputting optical chan
`nels. Alternatively, the demultiplexer can be omitted if only
`one optical channel is to be dropped. Plural demultiplexer
`optical paths optically communicate With the optical demul
`tiplexer for receiving each of the dropped optical channels.
`Similarly, an optical path optically communicates With the
`add port of the static add-drop multiplexer. The add optical
`path includes an optical combiner or multiplexer having
`plural combiner input ports communicating With plural
`combiner optical paths for receiving optical channels to be
`added to the optical transmission path and an output port for
`outputting a combined optical signal comprising the optical
`channels received from the combiner input ports.
`An optical sWitch positioned in one or more of the
`demultiplexer optical paths permits sWitching of a dropped
`optical channel betWeen a receiver optical path for directing
`the dropped optical signal to an optical receiver and betWeen
`a combiner optical path for routing the dropped optical
`channel back toWards the optical transmission path, option
`ally passing the dropped optical channel through a remodu
`lator. Alternatively, the optical sWitch routes the dropped
`optical channel toWards an optical receiver While permitting
`a neW optical channel to be routed to add port of the static
`add-drop multiplexer.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 schematically depicts a recon?gurable add-drop
`multiplexer according to the present invention;
`FIG. 2 schematically depicts a static add-drop multiplexer
`for use With the recon?gurable add-drop multiplexer of FIG.
`1;
`FIG. 3 schematically depicts a recon?gurable add-drop
`multiplexer according to a further embodiment of the
`present invention;
`FIG. 4 schematically depicts a recon?gurable add-drop
`multiplexer according to a further embodiment of the
`present invention; and
`FIG. 5 schematically depicts a remodulator.
`
`DETAILED DESCRIPTION
`
`Turning noW to the draWings in detail, in Which like
`numerals indicate the same or similar elements, FIG. 1
`depicts a recon?gurable add-drop multiplexer 10 according
`to the present invention. Recon?gurable add-drop multi
`plexer 10 is interposed in optical transmission path 12.
`Transmission path 12 is typically a single mode optical ?ber
`that forms the principal transmission medium of an
`N-channel Wavelength division multiplexed optical system
`Where N is a Whole number greater than or equal to 2.
`Exemplary values for N are 4, 8, 16, and 32 or more optical
`channels. WDM optical systems suitable for the application
`of the present invention are described in commonly-assigned
`US. Pat. No. 5,504,609, the disclosure of Which is incor
`porated by reference herein.
`Recon?gurable add-drop multiplexer 10 includes static
`add-drop multiplexer 14 for removing and inserting optical
`channels into optical transmission path 12. The expression
`“static” as used to describe add-drop multiplexer 14 refers to
`the fact that the channels dropped by multiplexer 14 are
`?xed, and are not remotely recon?gurable. An exemplary
`add-drop multiplexer for use as static add-drop multiplexer
`14 is depicted in FIG. 2. Add-drop multiplexer 14 comprises
`
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`Exhibit 1016, Page 7
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`3
`an optical circulator 20 having ?rst, second, and third optical
`circulator ports 22, 24, and 26, respectively. Optical circu
`lator 20 is con?gured such that optical signals Which enter
`circulator port 22 exit through circulator port 24 and optical
`signals Which enter circulator port 24 exit through circulator
`port 26.
`Optical transmission path 12 optically communicates With
`?rst circulator port 22. The expression “optically commu
`nicates” as used herein, refers to any connection, coupling,
`link, or the like, by Which optical signals carried by one
`optical system element are imparted to the “communicating”
`element. Such “optically communicating” devices are not
`necessarily directly connected to one another, but may be
`separated by intermediate optical components or devices. In
`an exemplary embodiment, optical transmission path 12 is a
`single mode optical ?ber Which forms the principal trans
`mission medium for a Wavelength division multiplexed
`optical communication system.
`A second transmission path 50 optically communicates
`With second circulator port 24. Positioned Within optical
`transmission path 50 is an optical ?lter 40. In the depicted
`embodiment, ?lter 40 comprises a set of four ?ber Bragg
`gratings, 42, 44, 46, and 48 respectively corresponding to
`Wavelengths of )ti, )tj, >\.k, and 9t]. In an exemplary
`embodiment, )ti<)tj-<)tk<)tl to avoid problems associated With
`transmission through radiation mode loss regions of adjacent
`gratings. Although gratings are employed as an exemplary
`optical ?lter, it is understood that any optical device capable
`of selecting the desired optical channels can be employed as
`?lter 40.
`A third optical transmission path 28 optically communi
`cates With third optical circulator port 26. Optical transmis
`sion path 28 receives optical signals Which are re?ected by
`optical ?lter 40 back toWards second circulator port 24.
`Optical coupler 30 is used to couple optical signals to be
`added to an optical transmission system. Optical coupler 30
`is selected from any optical device Which combines optical
`signals from plural input ports and places the combined
`optical signal onto an output port. Typically, the optical
`signals from tWo input ports are equally combined and
`placed on the output path although the tWo input paths can
`be combined in various ratios (e.g., 70:30, 80:20, etc.)
`depending upon the needs of the optical system (e.g., When
`desiring to equaliZe signal strength from tWo optical paths).
`Exemplary optical couplers are 1X2 fused ?ber optical
`splitters, commercially available from Corning and Gould,
`used to combine signals rather than split the signals. Optical
`coupler 30 includes ?rst input port 32, second input port 36,
`and output port 34. First input port 32 optically communi
`cates With optical transmission path 50 for receiving those
`optical signals output by optical circulator port 24 Which are
`not dropped by optical ?lter 40, i.e., the “through” optical
`signals.
`A fourth optical transmission path 39 optically commu
`nicates With second coupler input port 36 for adding optical
`signals to the through optical signals received by ?rst
`coupler input port 32. Because coupler 30 combines the
`optical signals from input ports 32 and 36, the optical signals
`Which are added via transmission path 39 do not contact
`optical ?lter 40 but are directly combined With the signals
`from ?rst input port 32 and output through port 34.
`Consequently, an arbitrary number of optical channels may
`be added to the optical system; the Wavelengths of the
`optical channels do not need to correspond to the Wave
`lengths of the channels dropped by optical ?lter 40.
`Optical transmission path 12, i.e., the primary optical
`transmission path of the WDM optical system, optically
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`communicates With coupler output port 34 for receiving the
`combined optical signal from the ?rst and second input
`ports. It is emphasiZed that the static add-drop multiplexer of
`FIG. 2 is merely exemplary. Any add-drop multiplexer
`Which can select the desired optical channels can be used in
`the recon?gurable add-drop multiplexers of the present
`invention. For example, an add drop multiplexer based on
`interference ?lters commercially available from Dicon and
`J DS Fitel, for example, may also be used. Further exemplary
`add-drop multiplexers are described in commonly-assigned
`US. patent application Ser. No. 08/622,957, ?led Mar. 27,
`1996 and 08/759,965, ?led Dec. 2, 1996, the disclosures of
`Which are incorporated by reference herein.
`Returning to the recon?gurable add-drop multiplexer of
`FIG. 1, optical path 28, Which receives the dropped optical
`channels, optically communicates With demultiplexer input
`port 62 of optical demultiplexer 60 for separating the
`dropped optical channels into individual optical channels to
`be individually routed to separate output paths 64 through
`output ports 63. Optical demultiplexer can be selected from
`any optical device or system Which can take a combined
`optical signal and separate individual optical channels there
`from. Exemplary optical demultiplexers include planar
`Waveguide devices such as arrayed Waveguide gratings
`(AWG) or other routers, as Well as passive optical splitters
`combined With gratings-based selectors (see, for example,
`the receiving system grating selectors of US. Pat. No.
`5,504,609, incorporated herein by reference).
`Typically, the dropped optical channel Will be routed to
`optical receiver 80, either directly or after being transmitted
`through another branch of the same or another optical
`system. HoWever, if it is desired that the optical channel
`remain on the optical transmission path 12, the optical
`channel can be routed to an optical path leading to the add
`port of static add-drop multiplexer 14. Optical sWitch 70
`permits the selection of either optical path for the appropri
`ate routing of the dropped optical signal. Optical sWitch 70
`may be an SR12AU-20NC 1:2 optical sWitch commercially
`available from JDS-Fitel. HoWever, it is understood that the
`depicted optical sWitches are exemplary. Other electrome
`chanical optical sWitches as Well as electro-optic and
`thermo-optic sWitches having a variety of sWitching con
`?gurations can also be employed in the recon?gurable
`add-drop multiplexers of the present invention. Exemplary
`optical sWitches and sWitch con?gurations enable the selec
`tion of different optical path in feWer than 50 milliseconds,
`With times of feWer than 15 milliseconds or even less than
`1 millisecond being preferred.
`To optionally enable the recon?gurable add-drop multi
`plexers of the present invention to be dynamically
`recon?gurable, the optical sWitches can be externally con
`trolled through control signals carried by a service channel,
`)tSC, on optical transmission path 12, as shoWn in FIG. 1.
`The service channel is fed, via optical demultiplexer 60, to
`a circuit such as a service channel modem 93 Where it is
`converted to an electrical signal used to direct sWitch
`controller circuit 95. If the service channel carries informa
`tion for receipt by other service channel modems coupled to
`optical communication path 12, service channel modem 93
`retransmits the service channel, km‘, to optical communi
`cation path 12 via combiner 90. While this technique for
`controlling the optical sWitching is exemplary, it is under
`stood that any method for controlling the optical sWitches is
`Within the scope of the present invention.
`Optical channels to be added to optical transmission path
`12 enter static add-drop multiplexer 14 through input port
`36. Input port 36 optically communicates With add optical
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`Exhibit 1016, Page 8
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`path 39 in Which is positioned optical combiner 90. Optical
`combiner 90, including, for example, a passive optical
`element such as a fused ?ber coupler, or a multiplexer Which
`routes Wavelengths, receives optical channels to be added to
`the Wavelength division multiplexed optic system through
`combiner input ports 92. Combiner input ports 92 commu
`nicate With combiner optical paths 94 Which carry the
`optical channel(s) to be added. In the con?guration of FIG.
`1, the optical channel to be added is the same as the optical
`channel dropped by the static add-drop multiplexer. Other
`optical paths 94 can communicate With optical transmitters,
`remodulators, or other dropped optical channels for carrying
`optical channels to be added to the optical system. The
`depicted optical sWitch can be interposed in any or all of the
`remaining “drop” optical paths. The optical channels to be
`added can have any optical channel Wavelength as long as
`that Wavelength is not occupied by a “through” channel
`passed by static add-drop multiplexer 14. Moreover, the
`channels to be added and dropped can be changed or
`recon?gured Without affecting the through channels.
`In the con?guration of FIG. 3, a dropped optical channel
`to be added back into the optical system is ?rst routed
`through an optical remodulator 100. As seen in FIG. 5,
`optical remodulator 100 includes an optoelectronic element,
`such as photodetector 502, for receiving a dropped optical
`channel and outputting a corresponding electrical signal
`Which includes the information from the optical channel.
`The electrical signal is supplied to a drive circuit 501, Which,
`in turn, supplies a modulating circuit to external modulator
`503. An optical source, such as semiconductor laser 504,
`continuously emits light Which is modulated by external
`modulator 503, a Mach-Zehnder interferometer, for
`example, in accordance With the electrical signal. The modu
`lated light is next output to combiner 90.
`Exemplary remodulators for use With the present inven
`tion are described in US. Pat. No. 5,504,609, incorporated
`by reference above. The con?guration shoWn in FIG. 3
`advantageously regenerates the signal and readily accom
`plishes Wavelength translation.
`Although an external modulation scheme is illustrated in
`FIG. 5, a directly modulated scheme is Within the scope of
`the present invention Whereby a modulated optical output is
`generated by directly turning laser 504 on and off.
`Preferably, the poWer level of the optical signal is adjusted
`so that all the channels carried by optical transmission path
`12 have substantially the same poWer level, i.e., “poWer
`balancing” is achieved. Moreover, in the embodiments illus
`trated in FIGS. 1 and 3, an optical ampli?er 91, including an
`erbium doped ?ber, for example, can be provided at the
`output of static add/drop multiplexer 14 to amplify signals
`carried on optical transmission path 12. Alternatively, opti
`cal ampli?er 91 can be provided at the input of add/drop
`multiplexer 14.
`In the con?guration of FIG. 4, a 2:2 bypass optical sWitch
`110, for example, an SR2BA5-20NC commercially avail
`able from JDS-Fitel, permits the dropped optical channel to
`be routed to optical receiver 80. An optical channel to be
`added is generated by optical transmitter 120 and mapped to
`a channel Wavelength Within the channel plan of the WDM
`optical system through remodulator 100. In this
`embodiment, a dropped channel to be re-routed to the optical
`transmission path is passed through the remodulator, as in
`the previous embodiment.
`While the foregoing invention has been described in terms
`of the embodiments discussed above, numerous variations
`are possible, Accordingly, modi?cations and changes such
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`as those suggested above, but not limited thereto, are con
`sidered to be Within the scope of folloWing claims.
`What is claimed is:
`1. A recon?gurable optical add-drop multiplexer for a
`Wavelength division multiplexed optical communication
`system comprising:
`a static optical add-drop multiplexer including an input
`port for receiving optical signals from an optical trans
`mission path in a Wavelength division multiplexed
`optical communication system, a drop port for routing
`optical channels to be removed from an optical trans
`mission path, an add port for receiving optical channels
`to be added to an optical transmission path, Wavelength
`selecting means for selecting optical channels to be
`dropped from the optical transmission path, an output
`port supplying at least ones of said optical channels not
`selected by said selecting means, and a continuous
`optical path coupling said input port and said output
`port;
`an optical path optically communicating With the drop
`port having positioned therein an optical demultiplexer
`having a demultiplexer input port for receiving the
`dropped optical channels and plural demultiplexer out
`put ports for separately outputting optical channels;
`plural demultiplexer optical paths optically communicat
`ing With the optical demultiplexer for receiving each of
`the dropped optical channels;
`an optical path optically communicating With the add port
`having positioned therein an optical combiner having
`plural combiner input ports for receiving optical chan
`nels to be added to the optical transmission path and an
`output port for outputting a combined optical signal
`comprising the optical channels received from the
`combiner input ports;
`at least one optical receiving path con?gured to route a
`dropped optical channel to an optical receiver;
`plural combiner optical paths optically communicating
`With the optical combiner for carrying optical channels
`to be added to the optical transmission path;
`optical sWitching means optically communicating With a
`demultiplexer optical path and With a combiner optical
`path and With an optical receiving means, the optical
`sWitching means con?gured to sWitch a dropped optical
`channel from the demultiplexer optical path to the
`combiner optical path or to sWitch a dropped optical
`channel from the demultiplexer optical path to the
`optical receiving means.
`2. A recon?gurable optical add-drop multiplexer as
`recited in claim 1 further comprising an optical remodulator
`positioned in the combiner optical path optically communi
`cating With the optical sWitching means, the optical remodu
`lator comprising:
`an optoelectronic element for receiving a dropped optical
`channel and outputting a corresponding electrical sig
`nal Which includes the information from the optical
`channel;
`an optical source for emitting an optical signal at an
`optical channel Wavelength; and
`means for modulating the optical source With information
`from the electrical signal output by the optoelectronic
`element to create an output signal including the infor
`mation from the dropped optical channel;
`a remodulator output port optically communicating With
`the combiner optical path for placing the output signal
`onto the combiner optical path.
`
`Cisco Systems, Inc.
`Exhibit 1016, Page 9
`
`

`
`6,069,719
`
`7
`3. Arecon?gurable optical add-drop multiplexer in accor
`dance With claim 2, wherein a Wavelength of said dropped
`optical channel is different than a Wavelength of said output
`signal.
`4. A recon?gurable optical add-drop multiplexer as
`recited in claim 2 further comprising an optical transmitter
`for transmitting an optical signal to be supplied to the optical
`remodulator.
`5. A recon?gurable optical add-drop multiplexer, com
`prising:
`a static add/drop multiplexer having an input port receiv
`ing a ?rst plurality of Wavelength division multiplexed
`channels, a drop port, an add port, an output port
`outputting a second plurality of Wavelength division
`multiplexed channels, a continuous optical path cou
`pling said input port to said output port, said static
`add/drop multiplexer outputting at least one of said ?rst
`plurality of Wavelength division multiplexed channels
`through said drop port; and
`an optical sWitch coupled to said drop port, said sWitch
`selectively supplying said at least one of said ?rst
`plurality of Wavelength division multiplexed channels
`to one of an opto-electronic receiver and said add port,
`said at least one of said plurality of Wavelength division
`multiplexed channels being supplied through said out
`put port of said static add/drop multiplexer as one of
`said second plurality of Wavelength division multi
`plexed channels When said optical sWitch supplies said
`at least one of said ?rst plurality of Wavelength division
`multiplexed channels to said add port.
`6. Arecon?gurable optical add-drop multiplexer in accor
`dance With claim 4, Wherein said input port also receives a
`service channel carrying control signals, said service chan
`nel being output through said drop port, said recon?gurable
`optical add-drop multiplexer further comprising:
`a service channel modem circuit coupled to said drop port,
`said service channel modem generating an electrical
`control signal in response to said service channel; and
`a sWitch controller circuit coupled to said optical sWitch
`and con?gured to receive said electrical control signal,
`said sWitch controller circuit controlling said optical
`sWitch in accordance With said electrical control signal.
`7. An optical device comprising:
`a static add/drop multiplexer having an input port receiv
`ing a ?rst plurality of Wavelength division multiplexed
`channels, a drop port, an add port, an output port
`
`10
`
`15
`
`45
`
`8
`outputting a second plurality of Wavelength division
`multiplexed channels, a continuous optical path cou
`pling said input port to said output port, said static
`add/drop multiplexer outputting at least one of said ?rst
`plurality of Wavelength division multiplexed channels
`through said drop port;
`an optical sWitch coupled to said drop port, said sWitch
`selectively supplying said at least one of said ?rst
`plurality of Wavelength division multiplexed channels
`to one of an opto-electronic receiver and said add port,
`said at least one of said plurality of Wavelength division
`multiplexed channels being supplied through said out
`put port of said static add/drop multiplexer as one of
`said second plurality of Wavelength division multi
`plexed channels When said optical sWitch supplies said
`at least one of said ?rst plurality of Wavelength division
`multiplexed channels to said add port; and
`an optical ampli?er coupled to said output port for ampli
`fying said second plurality of Wavelength division
`multiplexed channels.
`8. An optical device in accordance With claim 6, Wherein
`said optical ampli?er comprises an erbium doped ?ber.
`9. A recon?gurable optical add-drop multiplexer as
`recited in claim 5 further comprising an optical remodulator
`coupled to said optical sWitch and said add port, the optical
`remodulator comprising:
`an optoelectronic element for receiving a dropped channel
`from said ?rst plurality of Wavelength division multi
`plexed channels and outputting a corresponding elec
`trical signal Which includes the information from the
`dropped channel;
`an optical source for emitting an optical signal at an
`optical channel Wavelength; and
`means for modulating the optical source With information
`from the electrical signal output by the optoelectronic
`element to create an output signal including the infor
`mation from the dropped optical channel;
`an output port optically communicating With the add port
`for supplying the output signal as one of said second
`plurality of Wavelength division multiplexed channels.
`10. A recon?gurable optical add-drop multiplexer in
`accordance With claim 9, Wherein a Wavelength of said
`dropped optical channel is different than a Wavelength of
`said output signal.
`
`Cisco Systems, Inc.
`Exhibit 1016, Page 10