(12)
`
`United States Patent
`Goldstein et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,928,244 B1
`Aug. 9, 2005
`
`US006928244B1
`
`(54) SYSTEM AND METHOD OF WAVELENGTH
`ADD/DROP MULTIPLEXING HAVING
`CLIENT CONFIGURABILITY
`
`(75) Inventors; Evan L_ Goldstein, Princeton, NJ (Us);
`Lih_Yuan Lin, Little Silver, NJ (Us);
`Chuan Pu, Middletown, NJ (Us);
`Robert William Tkach, Little Silver,
`NJ (US)
`
`(73) Assignee: AT&T Corp., NeW York, NY (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`USC. 154(b) by 573 days.
`
`(21) Appl. No.: 09/722,955
`(22) Filed:
`NOV‘ 27’ 2000
`
`Related U_S_ Application Data
`(60) Provisional application No‘. 60/172,732, ?led on Dec. 20,
`?99algndzgégvlslonal apphcatlon NO- 60/204352: ?led on
`ay
`’
`'
`(51) Int. C].7 ........................ .. H04J 14/00; H04] 14/02;
`G02B 6/26; G02B 6/42
`(52) US. Cl. ........................... .. 398/45; 398/51; 398/54;
`_
`398/83; 385/17; 385/18
`Fleld of Search ............................ ..
`54,
`398/83’ 82’ 38 / 17’ 18
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`5,671,304 A * 9/1997 Duguay ..................... .. 385/17
`5,841,917 A * 11/1998 Jungerman et al.
`385/17
`6,144,781 A * 11/2000 Goldstein et al. . . . . .
`. . . .. 385/18
`6,335,992 B1 * 1/2002 Bala et al. .................. .. 385/17
`6,356,679 B1 * 3/2002 Kapany ..................... .. 385/18
`6,445,841 B1 * 9/2002 Gloeckner et al.
`385/17
`6,480,645 B1 * 11/2002 Peale et al. .............. .. 385/18
`6,519,060 B1 * 2/2003 Liu ........................... .. 398/49
`
`* cited by examiner
`
`Primary Examiner—M. R. Sedighian
`
`ABSTRACT
`(57)
`An optical carrier drop/add transmission system and method
`for adding a signal to multiplexed input optical signals
`conveyed by an optical multiplex input line. The multi
`plexed input optical signals are demultiplexed to provide
`isolated input optical signals to an optical sWitch matrix
`comprising sWitches in an array of lines and columns, the
`isolated input Optical Signals being inputted in a direction
`parallel to a line of sWitches in the optical sWitch matrix. The
`added Optical Signal is input in a direction parallel to a
`column in the optical sWitch matrix. An output line is
`Selected and the Switch that is on the Column on
`the
`added 0 tical si nal is in utted and on the selected out ut
`P
`g
`P
`P
`line is Switched‘
`
`5,581,643 A * 12/1996 Wu ........................... .. 385/17
`
`10 Claims, 9 Drawing Sheets
`
`Cisco Systems, Inc.
`Exhibit 1033, Page 1
`
`

`

`U.S. Patent
`
`Aug. 9,2005
`
`Sheet 1 01 9
`
`US 6,928,244 B1
`
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`Cisco Systems, Inc.
`Exhibit 1033, Page 2
`
`

`

`U.S. Patent
`
`Aug. 9, 2005
`
`Sheet 2 0f 9
`
`US 6,928,244 B1
`
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`
`Cisco Systems, Inc.
`Exhibit 1033, Page 3
`
`

`

`U.S. Patent
`
`Aug. 9,2005
`
`Sheet 3 0f 9
`
`US 6,928,244 B1
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`
`Cisco Systems, Inc.
`Exhibit 1033, Page 4
`
`

`

`U.S. Patent
`
`Aug. 9,2005
`
`Sheet 4 0f 9
`
`US 6,928,244 B1
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`
`Cisco Systems, Inc.
`Exhibit 1033, Page 5
`
`

`

`U.S. Patent
`
`Aug. 9,2005
`
`Sheet 5 0f 9
`
`US 6,928,244 B1
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`Cisco Systems, Inc.
`Exhibit 1033, Page 6
`
`

`

`U.S. Patent
`
`Aug. 9,2005
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`US 6,928,244 B1
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`Exhibit 1033, Page 7
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`

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`U.S. Patent
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`Aug. 9,2005
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`Exhibit 1033, Page 8
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`U.S. Patent
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`Aug. 9,2005
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`US 6,928,244 B1
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`Exhibit 1033, Page 9
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`

`

`U.S. Patent
`
`Aug. 9,2005
`
`Sheet 9 0f 9
`
`US 6,928,244 B1
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`Exhibit 1033, Page 10
`
`

`

`US 6,928,244 B1
`
`1
`SYSTEM AND METHOD OF WAVELENGTH
`ADD/DROP MULTIPLEXING HAVING
`CLIENT CONFIGURABILITY
`
`This non-provisional application claims the bene?ts of
`US. Provisional Application No. 60/172,732 entitled
`“Wavelength add/drop Multiplexer With Client Con?g
`urability” Which Was ?led on Dec. 20, 1999 and is hereby
`incorporated by reference in its entirety. The applicants of
`the provisional application are Evan L. Goldstein, Lih-Yuan
`Lin and Robert W. Tkach.
`This non-provisional application also claims the bene?ts
`of US. Provisional Application No. 60/204452 entitled
`“Micro-machined Optical Add/Drop Multiplexer With Cli
`ent Con?gurability” Which Was ?led on May 16, 2000 and
`is hereby incorporated by reference in its entirety. The
`applicants of the provisional application are Chuan Pu, Evan
`L. Goldstein, Lih-Yuan Lin and Robert W. Tkach.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of Invention
`This invention relates to optical communication. More
`particularly, this invention relates to systems and methods
`using optical sWitches for adding and dropping channels
`from an optical transmission medium.
`2. Description of Related Art
`In current optical communication systems, multiple chan
`nels are multiplexed onto a single optical transmission
`medium using multiplexing techniques, such as Wavelength
`division-multiplexing (WDM). WDM can combine a plu
`rality of communication channels, in the form of discrete
`Wavelengths, onto a single optical ?ber. As multiplexing
`techniques improve, an increasing number of channels are
`being transmitted on a single optical ?ber or group of optical
`?bers. As the number of channels increase, so too does the
`need for an ability to add and/or drop a portion of the
`channels to and/or from the transmission medium.
`Current communication systems can use an opto
`electronic regeneration technique to add and drop channels
`from a transmission system. With such a technique, in order
`to receive or transmit data on the optical netWork using
`WDM, a node of the netWork can include at least one optical
`sensor that receives the optical signal at one or more
`Wavelengths. The optical sensor can include an optical
`electrical converter that can convert the optical signal to
`electrical signals corresponding to the received optical sig
`nals. Adding and/or dropping of the signals can then be
`performed electronically by processing the electrical signals
`in the electrical domain. The resulting electrical signal can
`then be modulated onto the netWork using an electro-optical
`converter. Such Optical-Electrical-Optical (OEO) conver
`sion can be very complex, costly and time consuming.
`Additionally, optical Wavelength add/drop multiplexers
`(OADM) can be used in WDM transmission systems.
`Currently, it has been Well recogniZed that OADMs are
`needed to avoid the complex and costly OEO conversions.
`HoWever, currently available OADMs are generally ?xed. In
`other Words, a given incoming channel (Wavelength) is only
`associated With a ?xed add/drop port. Such a device lacks
`“client-con?gurability” and therefore severely limits the
`selection of Which channels to add/drop for a client.
`Therefore, there exists a need for a device to add and drop
`channels from a transmission medium that can be readily
`con?gured according to the needs of a client.
`
`SUMMARY OF THE INVENTION
`
`The invention provides an optical sWitch matrix device
`and methods that selectively add and drop channels from an
`
`10
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`2
`optical communication medium. The optical sWitch matrix
`can receive an input signal from an optical medium, such as
`an optical ?ber cable. The input signal can include numerous
`input channels, for example a plurality of channels each
`having a different Wavelength. The optical sWitch matrix can
`also receive an add signal Which can include numerous add
`channels for different clients; each add channel can replace
`an input channel of the input signal that is dropped.
`Depending on the con?guration of the optical sWitch
`matrix, any channels of the input optical signal can be
`dropped from the communication medium to any of the
`clients. The dropped channels can be received and processed
`by a receiver. Further, any channels from the add signal can
`be added to the communication medium. The added chan
`nels along With the remaining channels of the input signal
`can then be outputted and transmitted on the communication
`medium. Different from ?xed optical Wavelength add/drop
`multiplexers (OADMs) described in the related art, the
`invented optical sWitch matrix can be con?gured to alloW
`each client to access any of the input channels, therefore
`offering client-con?gurability to the netWork.
`The optical sWitch matrix can be a device that operates on
`the optical channels in the optical domain. For example, the
`optical sWitch matrix can be a device, such as a micro
`electrical mechanical system (MEMs), having an array of
`micromirrors that are rotatably mounted on a substrate. The
`micromirrors may be selectively positioned to interact With
`passing light, so as to redirect light beams betWeen ports of
`the optical sWitch matrix. Accordingly, the optical sWitch
`matrix can add/drop channels to/from an optical communi
`cation medium.
`Alternatively, or in conjunction With the MEMs, the
`optical sWitch matrix can be a device such as a matrix of
`sWitches utiliZing bubble technology. As an optical channel
`passes through the optical sWitch matrix, bubble sWitches
`can be selectively activated causing the channel to be
`redirected betWeen ports of the optical sWitch matrix.
`Accordingly, the optical sWitch matrix can add/drop chan
`nels to/from an optical communication medium.
`These and other features and advantages of this invention
`are described in or are apparent from the folloWing detailed
`description of the system and method according to exem
`plary embodiments of this invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The bene?ts of the present invention Will be readily
`appreciated and understood from consideration of the fol
`loWing detailed description of exemplary embodiments of
`this invention, When taken together With the accompanying
`draWings, in Which:
`FIG. 1 is an exemplary block diagram of a Wavelength
`add-drop device in accordance With the present invention;
`FIG. 2 is an exemplary block diagram of a Wavelength
`add-drop device using MEMS technology in a unidirectional
`netWork in accordance With the present invention;
`FIGS. 3 and 4 are exemplary block diagrams of the
`Wavelength add-drop device of FIG. 2 in tWo different
`functioning con?gurations;
`FIG. 5 is an exemplary functional block diagram of a
`Wavelength add-drop device according to an embodiment of
`the present invention;
`FIGS. 6 and 7 are exemplary functional block diagrams of
`a Wavelength add-drop device using MEMS technology in a
`bi-directional netWork in accordance With the present inven
`tion; and
`FIGS. 8 and 9 are exemplary functional block diagrams of
`a Wavelength add-drop device using MEMS technology in a
`bi-directional netWork in accordance With the present inven
`tion.
`
`Cisco Systems, Inc.
`Exhibit 1033, Page 11
`
`

`

`US 6,928,244 B1
`
`3
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`FIG. 1 shows an optical switch matrix system 100 for
`selectively adding and dropping channels from a transmis
`sion medium 120. The system 100 includes an optical sWitch
`matrix 102 having four ports: input port 104, output port
`106, add port 108 and drop port 110. The input port 104 is
`optically coupled to a demultiplexer 112 for receiving input
`channels 104a—104f from the transmission medium 120. The
`output port 106 is optically coupled to a multiplexer 114 for
`transmitting optical channels 106a—106f onto the transmis
`sion medium 120. The add port 108 is optically coupled With
`the optical sWitch matrix 102 for inputting added channels
`108a—108e that are connected to different clients. The drop
`port 110 is optically coupled With the optical sWitch matrix
`102 for transmitting drop channels 110a—110e, possibly for
`further processing.
`Both the multiplexer 114 and the demultiplexer 112 are
`optically coupled With the transmission medium 120. The
`transmission medium 120 can include any structure that
`alloWs for the transmission of optical communication
`signals, such as an optical ?ber. The optical communication
`signals can further include a plurality of channels that are
`simultaneously transmitted along the communication
`medium 120. For example, numerous channels having dis
`crete Wavelengths can be combined onto a single optical
`transmission medium using Wavelength-division
`multiplexing (WDM).
`The demultiplexer 112 is a device that is capable of
`optically dividing input signals received on the transmission
`medium 120 into a plurality of channels 104a—104f. Once
`the input channel is divided, the input channels 104a—104f
`are transmitted to the optical sWitch matrix 102. As
`described above, the channels can travel along the transmis
`sion medium 120 on different Wavelengths.Additionally, the
`channels of the input signal can be combined on the trans
`mission medium 120 according to any Well knoWn commu
`nication technique, such as TDMA, CDMA and the like.
`Any technique that alloWs multiple channels to be transmit
`ted across the transmission medium 120 and separated by
`the demultiplexer 112 can be used Without departing from
`the spirit and scope of the present invention.
`The multiplexer 114 is a device that is capable of optically
`combining the output channels 106a—106f received from the
`optical sWitch matrix 102 into an output signal that is then
`transmitted on the transmission medium 120. As described
`above, the numerous output channels 106a—106f can travel
`along the transmission medium as an output signal in
`accordance With any knoWn or later developed transmission
`technique Without departing from the spirit and scope of the
`present invention.
`The add port 108 is a device that is capable of receiving
`channels 108a—108e from different clients, and then trans
`mitting the added channels 108a—108e to the optical sWitch
`matrix 102. Data sources for the added channels 108a—108e
`can be generated by a plurality of light sources, such as
`tunable laser diodes, included in the add port 108. Each of
`the light sources can be adjusted to emit a channel having a
`speci?c Wavelength. The light sources of the add port 108
`can further operate in accordance With instructions received
`from a controller (not shoWn) in order to selectively output
`an added channel of a speci?c Wavelength. For example,
`added channels 108a—108e can each be transmitted on
`different Wavelengths hf)», corresponding to the Wave
`lengths of the input channels.
`The drop port 110 is a device that is capable of receiving
`drop channels 110a—110e from the optical sWitch matrix
`102. Each of the channels can be of various Wavelengths.
`The drop port 110 can then output any of the drop channels
`to a processor (not shoWn) for further processing.
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`The optical sWitch matrix 102 is a device that is capable
`of redirecting optical signals passing through the optical
`sWitch matrix 102. In this manner, a portion of the input
`channels 104a—104f can pass through the optical sWitch
`matrix 102 to the output channels 106a—106f Without any
`substantial interference. In other Words, these channels are
`permitted to pass nearly unabated through the optical sWitch
`matrix 102 and continue to travel on the transmission
`medium 120.
`Alternatively, a portion of the input channels can be
`selectively redirected to a drop channel 110a—110e of the
`drop port 110 as the inputted channels 104a—104f pass
`through the optical sWitch matrix 102. In a similar manner,
`added channels 108a—108e can be selectively redirected to
`output channels 106a—106f of the output port 106 for Which
`the corresponding input channel has been dropped as the
`added channels pass through the optical sWitch matrix 102.
`According to this technique, input channels can be removed/
`dropped and neW channels can be added to the transmission
`medium 120.
`The optical sWitch matrix 102 can include an array of
`sWitches that can be in either an active or inactive state. In
`an active state, the sWitch is able to redirect a light beam or
`channel passing in close proximity to the sWitch. In an
`inactive state, the sWitch alloWs a light beam or channel to
`pass Without incident.
`As an example of operation, assume that the optical
`sWitch matrix 102 includes at least N><M matrix of sWitches
`that are initially in the inactive position. Further assume that
`the transmission medium 120 is transmitting an input signal
`having 6 channels (A—F). In the initial state, the input signal
`can be received by the demultiplexer 112. The demultiplexer
`112 operates on the input signal to optically separate the
`input signal into input channels 104a—104f. The input chan
`nels 104a—104f are then transmitted to the optical sWitch
`netWork 102.
`In the initial state of the sWitch matrix 102, Where all of
`the optical sWitches are in the inactive state, the input
`channels 104a—104f are permitted to pass through the optical
`sWitch matrix to the output channel 106a—106f Without
`being acted upon. Accordingly, the output channels
`106a—106f, corresponding to the input channels 104a—104f
`are transmitted to the multiplexer 114. The multiplexer 114
`then optically operates on the output channels 106a—106f in
`order to combine the output channels 106a—106f into an
`output signal, and then transmit the output signal back onto
`the transmission medium 120.
`During the course of operation, assume that it has noW
`become desirable to replace input channel 104c With an
`added channel 108b. Accordingly, as the input channels
`104a—104f are transmitted through the optical sWitch matrix
`102, one or more optical sWitches in the path of input
`channel 104c could be sWitched to an active state Whereby
`the optical sWitch can redirect the light beam corresponding
`to input channel 104c to the speci?ed drop port 110, such as
`dropped signal 110a. Furthermore, the add port 108 can
`begin transmitting an added signal 108b into the optical
`sWitch matrix 102 and an optical sWitch in the path of added
`channel 108b could be sWitched to an active state, and
`thereby redirect the added channel 108b to output channel
`106c of the output port 106.
`Accordingly, the multiplexer Would then receive the input
`channel 104a on output channel 106a, the input channel
`104b on the output channel 106b, the added channel 108b on
`the output channel 106c, the input channel 104d on the
`output channel 106d, the input channel 1046 on the output
`channel 1066 and the input channel 104f on the output
`channel 106f. The output channels 106a—106fWould then be
`combined by the multiplexer 114 and transmitted as an
`output signal across the transmission medium 120. In this
`
`Cisco Systems, Inc.
`Exhibit 1033, Page 12
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`

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`US 6,928,244 B1
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`5
`manner, a channel of the input signal, 1046, has been
`replaced (dropped) during the addition of the added channel
`108b.
`As is to be understood, the sWitches of the optical sWitch
`matrix 220 can be changed at any time during operation to
`add or drop channels to or from the transmission medium
`120. In this manner, a user can easily con?gure the optical
`sWitch matrix 102 to add or remove all or a portion of
`information from an optical netWork.
`As shoWn in FIG. 2, the optical sWitch matrix 102 can be
`a single microelectrical mechanical system (MEMs). This
`single MEMs design of the optical sWitch matrix can be
`particularly useful for dropping and adding channels from an
`unidirectional ring netWork. The MEMs includes an array of
`micromirrors 280 that are rotatably mounted to a substrate
`282. The micromirrors 280 are rotatable betWeen a non
`activated and activated position. In the non-activated
`position, the micromirrors 280 are substantially parallel and
`?ush With the substrate 282. In the active position, the
`micromirrors 280 are rotated or ?ipped to be in a substan
`tially perpendicular position relative to the substrate 280.
`Furthermore, in the active position the micromirrors 280 ate
`positioned Within the light path of channels passing through
`the optical sWitch matrix.
`This type of optical sWitch matrix is discussed in detail in
`Journal 0fMicroelectro-mechanical Systems, Vol. 5, No. 4,
`December 1996, entitled “Electrostatic Micro Torsion Mir
`rors for an Optical SWitch Matrix” by Hiroshi Toshiyoshi
`and Hiroyuki Fujita, incorporated herein by reference in its
`entirety. The optical sWitch matrix is also discussed in
`co-pending and commonly assigned patent application Ser.
`No. 09/002,240 ?led on Dec. 31, 1997, also incorporated
`herein by reference in its entirety.
`As shoWn in FIG. 2, the Wavelength add-drop device 200
`includes an optical N><M matrix sWitch 220 coupled to an
`input demultiplexer 210, an output multiplexer 230, an add
`port 240 and a drop port 250.
`The optical N><M matrix sWitch 220 can be a four-port
`matrix sWitch. In this embodiment, the optical N><M matrix
`sWitch 220 is a N><M free space MEMS crossconnect that
`comprises N><M micromirrors 280. In the exemplary
`embodiment shoWn in FIGS. 2—4, N=6 and M=5. As
`described above, each of the 30 micromirrors 280 shoWn in
`FIGS. 2—4 may take one of an active or inactive position.
`The positions of the micromirrors 280 can be controlled
`by a matrix controller (not shoWn in FIGS. 2—4). By ener
`giZing the sWitch that is on the ith roW and the jth column of
`the matrix sWitch, e.g., by ?ipping up the micromirror
`sWitch on line i and column j, and concurrently tuning the
`light source on 241j to the Wavelength used on the i”1 line,
`one can thus add a Wavelength from light source 241 j and/or
`drop a Wavelength at sensor 251j.
`Although the optical sWitch matrix 102 of FIG. 1 has been
`described in the exemplary embodiments of FIGS. 2—4 as
`being a MEMs type sWitch 220, it is to be understood that
`various other sWitches can be used Without departing from
`the spirit and scope of the present invention. For example,
`the optical sWitch matrix 102 can be any type of optical
`sWitch With or Without a micromechanical element, such as
`optical sWitches based on total internal re?ection of a
`?uid-containing planar light Wave circuit (PLC), otherWise
`knoWn as bubble technology. Such technology is more fully
`described in the article entitled “Compact Optical Cross
`Connect SWitch based on Total Internal Re?ection in a
`Fluid-Containing Planar Light Wave Circuit” by J. E.
`Fouquet, in 2000 OFC Technical Digest, pp. 204 to pp. 206,
`Which is incorporated herein by reference in its entirety.
`Referring again to FIG. 2, as an example of operation,
`assume that in an initial state of operation, all of the
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`micromirrors 280 are in the inactive position. Next, assume
`that a determination has been made that a signal conveyed
`by the input line 260 is to be dropped. If so, it is determined
`on Which line of the matrix the light ray that has the
`Wavelength that carries the signal to be dropped is trans
`mitted. Next, the sensor 251A to 251M on Which the signal
`is to be received is determined. The micromirror 280 cor
`responding to that line and the column of that selected sensor
`in the matrix is next positioned in the active position. Next,
`a determination is made Whether another signal conveyed by
`the input line 260 has to be dropped. The above operations
`are repeated until no other signal conveyed by the input line
`260 has to be dropped.
`As mentioned above, since the N><M matrix sWitch in
`FIG. 2 is implemented in a unidirectional netWork, the add
`channels are alWays associated With the drop channels. That
`is, the add channel and drop channel on the same column are
`associated With the same client. By using the backside
`re?ection of the activated micromirrors, and concurrently
`tuning the lasers of the add channels to selected
`Wavelengths, signals can be added into traf?c from the
`selected add channels.
`FIGS. 3 and 4 are exemplary functional block diagrams of
`the Wavelength add-drop device of FIG. 2 in tWo different
`functioning con?gurations corresponding to a same set of
`dropped light rays in a unidirectional netWork. In FIGS. 3
`and 4, the dropped light rays are the lights rays emitted by
`input ports 211B and 211D, on the second and fourth lines
`of sWitch matrix 220. HoWever, in the con?guration outlined
`in FIG. 3, the light ray transmitted on the second line is
`dropped to the sensor 251D and the light ray transmitted on
`the fourth line is dropped to the sensor 251B. In the
`con?guration outlined in FIG. 4, the light ray transmitted on
`the second line is dropped to the sensor 251C and the light
`ray transmitted on the fourth line is dropped to the sensor
`251E.
`Consequently, in the con?guration outlined in FIG. 3, the
`added signals are added by inputting light rays from the light
`sources 241B and 241D. In the con?guration outlined in
`FIG. 4, the added signals are added by inputting light rays
`from the light source 241C and 241E.
`FIGS. 3 and 4 shoW that the Wavelength add-drop device
`according to an exemplary embodiment of the invention can
`be con?gured to select Which sensor 251A—251E receives
`the dropped signal and to select the light source 241A—241E
`that inputs the added signal.
`The present invention describes a device that offers full
`client-con?gurability, permitting any subset of the incoming
`Wavelengths (1, 2, .
`.
`. N) to be added or dropped at any
`subset of the light sources 241A to 241E or sensors 251A to
`251E.
`An exemplary Wavelength add-drop device 400 is out
`lined in FIG. 5, and includes a signal manager 410, the
`optical N><M matrix sWitch 102, the input demultiplexer 112,
`the output multiplexer 114, the add port 108, the drop port
`110, the input line 160 and the output line 170.
`The signal manager 410 comprises a dropped signal
`processor 420, a matrix controller 430 and an added signal
`processor 440. The dropped signal processor receives the
`signals output by the dropped channels 110a—110e of the
`drop port 110 and processes those signals. The matrix
`controller 430 determines Which micromirrors in the optical
`matrix sWitch 102 are to be turned to their active position
`and commands the positions of the micromirrors. The added
`signal processor 440 provides the signals to be added
`through the add port 108 and the light sources 108A—108E.
`The signal manager 410, the dropped signal processor
`420, the matrix controller 430 and the added signal proces
`sor 440 may be, in the exemplary embodiment of the
`
`Cisco Systems, Inc.
`Exhibit 1033, Page 13
`
`

`

`US 6,928,244 B1
`
`7
`invention shown in FIG. 5, a microprocessor that uses
`software to implement exemplary embodiments of the meth
`ods and devices according to this invention.
`FIG. 6 shoWs a Wavelength add-drop device 700 Wherein
`the optical sWitch matrix 102 includes tWo optical N><M
`matrix sWitches 720A and 720B. This con?guration of the
`optical sWitch matrix 102 having tWo MEMs can be par
`ticularly useful for adding and dropping channels from a
`bi-directional ring netWork and/or a linear netWork. The
`optical N><M matrix sWitch 720A is coupled to an input
`demultiplexer 710, a drop port 750 and the optical N><M
`matrix sWitch 720B. The optical N><M matrix sWitch 720B
`is also coupled to an output multiplexer 730 and an add port
`740.
`As described above, the embodiment of the present inven
`tion described in FIG. 6 may be used in combination With a
`linear netWork or a bi-directional ring. Dropping and adding
`optical signals may be carried out independently by the
`optical N><M sWitch matrices 720A and 720B Which provide
`full client-con?gurability since the add port and the drop
`port associated With the same input channel or Wavelength
`are independent of each other.
`FIG. 7 shoWs an example of operation of the embodiment
`described in FIG. 6. In this example, assume that it is desired
`to replace a channel corresponding to input channel 711A
`With a neW channel corresponding to added channel 741C.
`As described above, the input channel is received by the
`demultiplexer 710. The demultiplexer divides the channels
`into respective input channels 711A—71F that are then input
`into the optical sWitch matrix 102.
`As can be seen in FIG. 7, the ?rst MEMs 720A of the
`optical sWitch matrix 102 receives the input channels.
`Further, micromirror 722 has noW been sWitched to an active
`state. Accordingly, the input channel 711A is redirected to a
`output channel 751B of the drop port 750. Additionally, as
`can be seen, the remaining input channels 711B—711F are
`permitted to pass across the ?rst MEMs 720A Without
`interference.
`Simultaneous to the dropping of input channel 711A, an
`input signal 741C is added to the output channel 731Aby the
`add port 740. As can be seen, a micromirror 724 of the
`second MEMs 720B is sWitched into an active position.
`Accordingly, the input signal 741C is redirected to the
`output port 731A of the output multiplexer 730.
`Additionally, the output ports 731B—731F receive the input
`channels 711B—711F, respectively.
`The multiplexer 730 then combines the neW combination
`of output channels 731A—731F into an output signal. The
`output signal is then transmitted across the transmission
`medium 770. Accordingly, the channel corresponding to
`input channel 711A has been removed from the transmission
`medium and the channel corresponding to added channel
`741C has been added in the removed channel’s place.
`It should be noticed that in the embodiment of the present
`invention outlined in FIG. 6, only one side of the sWitching
`mirrors is used. Moreover, the structure shoWn in FIG. 6 is
`strictly non-blocking. In other Words, a neW connection or a
`connection change can be made Without rerouting the exist
`ing non-changing connections.
`FIG. 8 shoWs a Wavelength add-drop device Wherein the
`optical sWitch matrix 102 includes one optical N><M matrix
`sWitch 820A and one optical M><M sWitch 820B. The optical
`N><M matrix sWitch 820A is coupled to an input demulti
`plexer 810, a drop port 850, the optical M><M matrix sWitch
`820B and an output multiplexer 830. The optical M><M
`matrix sWitch 820B is coupled to an add port 840.
`The embodiment of the present invention described in
`FIG. 8 may also be used in combination With a linear
`netWork or a bi-directional ring netWork. Dropping and
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`adding optical signals may be carried out independently by
`the optical matrix sWitches 820A and 820B Which provide
`full client-con?gurability since the add port and the drop
`port associated With the same input channel or Wavelength
`are independent of each other due to the optical M><M matrix
`820B.
`FIG. 9 shoWs an example of oper