(12) United States Patent
`Bishop et al.
`
`US006507421B1
`(10) Patent N0.2
`US 6,507,421 B1
`(45) Date of Patent:
`Jan. 14, 2003
`
`(54) OPTICAL MONITORING FOR OXC FABRIC
`
`(75) Inventors: David John BiSh0P,$11H1I_I1it,NJ (US);
`Randy Clinton Giles, W_h1PPaI1y, NJ
`(Us); Davld Thomas Nellsoll,
`P1a1nSb°r°>NJ (Us)
`
`6,292,281 B1 * 9/2001 Bala et al. ................ .. 359/110
`6,301,402 B1 * 10/2001 Bhalla et al. ............... .. 386/16
`6,330,380 B1 * 12/2001 Young et a1.
`385/17
`6,363,182 B2 * 3/2002 Milles et a1. ............... .. 385/17
`6,366,716 B1 * 4/2002 Graves ...................... .. 385/17
`6,396,975 B1 * 5/2002 Wood et al. ................ .. 385/18
`
`(73) Assignees: Lucent Technologies Inc., Murray Hill,
`NJ (US); Agere Systems Guardian
`Corp., Orlando, FL (US)
`
`*
`
`_
`_
`cued by exammer
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/414,621
`(22) Filed:
`Oct. 8, 1999
`H04J 14/00
`(51) Int Cl 7
`(52) us CL _____________________ __ 359/117. 359/128. 359/110,
`359/124; 359/127; 359/130; 359/159; 385/17;
`385/18
`(58) Field of Search ............................... .. 359/117, 128,
`359/110, 124, 127, 130, 139, 159; 385/17,
`18> 16> 24> 19> 20> 21> 22> 23
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`P '' ima" y Examiner —Les1ie Pascal
`Assistant EX?min€r—Hanh Phan
`(74) Attorney, Agent, or Firm—Cohen, Pontani, Lieberman
`& Pavane
`(57)
`
`ABSTRACT
`
`An optical crossconnect (OXC) fabric including an array of
`tiltable mirrors, a re?ector and a plurality of optical ?bers
`controls the position of the mirrors to optimize the transfer
`of a signal between an input optical ?ber and an output
`optical ?ber by monitoring the optical signal at an optical
`translation unit in each of the input optical ?ber and the
`output optical ?ber. The optical translation units are operable
`1fglr regenerating the optical signals transmitted through the
`
`ers.
`
`5,436,986 A * 7/1995 Tsai .......................... .. 385/16
`
`11 Claims, 2 Drawing Sheets
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`2000
`19111
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`124C
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`1/4d
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`[200d
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`o/t
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`Ow
`—-
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`206
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`204
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`202
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`1;)0
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`OXC FABRIC
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`CONTROLLER
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`2>l0u
`14o
`/ ELL
`14b
`OTU
`/
`t/o
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`/200b
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`—
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`206
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`234
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`2212
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`Petitioner Ciena Corp. et al.
`Exhibit 1007-1
`
`

`

`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 1 of2
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`US 6,507,421 B1
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`3k. 5228
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`s\ @2228
`0252
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`02A
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`n:
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`\lui
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`.QDN
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`Petitioner Ciena Corp. et al.
`Exhibit 1007-2
`
`

`

`U.S. Patent
`
`Jan. 14, 2003
`
`Sheet 2 of2
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`US 6,507,421 B1
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`38
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`:5
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`0.1
`USN
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`E0
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`0:53 86
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`§ am @2 f f I E .F 531 0:
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`Petitioner Ciena Corp. et al.
`Exhibit 1007-3
`
`

`

`US 6,507,421 B1
`
`1
`OPTICAL MONITORING FOR OXC FABRIC
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to an Optical Crossconnect
`(OXC) fabric for connecting an optical signal in an input
`?ber to an output ?ber and that includes an array of I/O
`?bers, an array of tiltable mirrors, and a re?ector.
`2. Description of the Related Art
`An Optical Crossconnect (OXC) device comprises an
`array of lenses, a corresponding array of mirrors, and a
`re?ector. An array of I/O ?bers Which corresponds to the
`array of lenses is received in the device so that the array of
`mirrors corresponds to the array of I/O ?bers. Each of the
`mirrors is tiltable about 2 axes for directing an input signal
`received from its corresponding I/O ?ber (i.e. an input ?ber)
`against the re?ector to another mirror and to an output one
`of the I/O ?bers, thereby signally connecting the input ?ber
`to the output ?ber and functioning as a sWitch.
`To ensure proper positioning of the mirrors for optimiZing
`the connection of the optical signal from the input I/O ?ber
`to the output I/O ?ber, optical taps are formed in each of the
`I/O ?bers for monitoring the optical signals and ensuring
`that the output signal approximates the input signal. If a
`difference betWeen the input and output signals exceeds a
`threshold value, the mirror positions are adjusted to optimiZe
`the output signal. Aproblem With this arrangement is that the
`optical taps direct a portion of the optical signal aWay from
`the I/O ?ber. Furthermore, OXCs typically include arrays of
`approximately 256 ?bers and mirrors. Accordingly, the
`optical taps add considerable cost to the OXC because they
`are required for each of the I/O ?bers.
`
`SUMMARY OF THE INVENTION
`
`The present invention uses signals present in an optical
`translation unit to monitor the mirror position and maintain
`optimal performance of an optical crossconnect (OXC)
`device. After an optical signal is transmitted from its source
`to the OXC device, it is generally degraded from its original
`form and amplitude due to attenuation and other losses
`and/or disturbances that it may receive or that are present
`along its path. For this reason, each I/O ?ber includes an
`optical translation unit (OTU) Which detects the incoming
`signal and regenerates the signal to its proper intensity and
`form. To accomplish this task, the OTU converts the optical
`signal to an electrical signal, performs the regeneration on
`the electrical signal, and transforms the regenerated electri
`cal signal into an optical signal for continued transmission of
`the optical signal to the OXC fabric. Although the OTU is
`not a part of the OXC fabric and is typically controlled
`separately therefrom, the electrical signal present in the
`OTU can be used instead of an optical tap connected to the
`optical ?ber to control the mirror position, because that
`electrical signal in the OTU represents the optical signal that
`is transmitted to the OXC fabric. Since the presence of an
`OTU in the ?bers is required to ensure signal quality, the use
`of the OTU for control of the mirror position reduces the
`number of required parts for the OXC and thereby does not
`signi?cantly add to the cost of manufacture.
`Other objects and features of the present invention Will
`become apparent from the folloWing detailed description
`considered in conjunction With the accompanying draWings.
`It is to be understood, hoWever, that the draWings are
`designed solely for purposes of illustration and not as a
`
`2
`de?nition of the limits of the invention, for Which reference
`should be made to the appended claims. It should be further
`understood that the draWings are not necessarily draWn to
`scale and that, unless otherWise indicated, they are merely
`intended to conceptually illustrate the structures and proce
`dures described herein.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`In the draWings, Wherein like reference characters denote
`similar elements throughout the several vieWs:
`FIG. 1 is an elevated perspective vieW of an Optical
`Crossconnect (OXC) according to the present invention; and
`FIG. 2 is a block diagram shoWing the control arrange
`ment for the present invention.
`
`DETAILED DESCRIPTION OF THE
`CURRENTLY PREFERRED EMBODIMENTS
`
`Referring to FIG. 1, an Optical Crossconnect (OXC)
`fabric 100 comprises an array of imaging lenses 10, a mirror
`array 20, and a re?ector 30. The OXC 100 is typically
`formed using Micro Electro-Mechanical Systems (MEMS)
`technology. The array of imaging lenses 10 comprises lenses
`12a—12a' respectively aligned with U0 ?bers 14a—14d. The
`mirror array 20 includes a plurality of mirrors 22a—22d
`respectively corresponding to the I/O ?bers 14a—14a'. The
`lenses 12a—12a' respectively correspond to the I/O ?bers
`14a—14a' for focussing the optical signals transmitted
`betWeen the I/O ?bers 14a—14d and the respective mirrors
`22a—22d of the mirror array 20. To simplify the draWing and
`for ease of explanation of its operation, the OXC fabric 100
`of FIG. 1 is shoWn as having four I/O ?ber and mirrors.
`HoWever, the OXC fabric may include any number of I/O
`?bers and mirrors and more typically includes a 16x16 array
`of 256 ?ber and mirrors.
`Each mirror 22a—22d of the mirror array 20 is connected
`to a controller 50 Which controls the tilt of the mirrors for
`routing a signal from one I/O ?ber to another. The mirrors
`22a—22d are formed using MEMS technology With a tWo
`axis ?exure gimbal mount via torsion springs 25 so that each
`mirror 22a—22a' can be tilted +/—5 degrees on each axis in
`response to a voltage signal. For example, if an input signal
`on I/O ?ber 14a is to be routed to I/O ?ber 14c, the mirrors
`22a and 22c are tilted so that the signal is re?ected off of
`mirror 22a and directed toWard re?ector 30, re?ected off the
`re?ector and directed toWard mirror 22c, and re?ected off of
`mirror 22c and directed to the I/O ?ber 14c. This particular
`routing example is depicted in FIG. 1. In this manner, any
`tWo I/O ?bers may be signally connected.
`FIG. 2 is a block diagram shoWing the connection of the
`I/O ?bers 14a—14a' to the OXC fabric 100. Each of the I/O
`?bers 14a—14a' may be used as either an input ?ber or an
`output ?ber. HoWever, as a practical matter some are de?ned
`as input ?bers and others as output ?bers. In FIG. 2, I/O
`?bers 14a and 14b are input ?bers and the I/O ?bers 14c and
`14d are output ?bers. Before entering the OXC Fabric 100,
`each input I/O ?ber 14a—14b runs through a respective
`Optical Translation Unit (OTU) 200a—200b Which is con
`nected to the controller 50. The primary function of the OTU
`200a—200b is to act as a buffer element for the optical signal
`and, more speci?cally, as a regeneration unit for regenerat
`ing the optical signal in the ?ber. When an optical signal
`travels through a long length of optical ?ber, the original
`optical signal is attenuated and may be adversely affected in
`other Ways such, for example, as via a phase shift and/or a
`frequency variation due to various external in?uences.
`Accordingly, the OTU 200a—200b on the input I/O ?bers
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`25
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`65
`
`Petitioner Ciena Corp. et al.
`Exhibit 1007-4
`
`

`

`US 6,507,421 B1
`
`3
`14a—14b converts the received optical signal into an elec
`trical signal, regenerates the electrical signal back to its
`original intensity and form, and converts the regenerated
`electrical signal back into an optical signal. The regenerated
`signal is then transmitted to the OXC fabric 100. The output
`I/O ?bers 14c—14d also have respective OTUs 200c—200a'
`Which perform the same function. If some degradation of the
`signal occurs in the OXC, the OTU 200c, 200d Will clean-up
`the signal by restoring the correct intensity and form before
`the signal is transmitted externally.
`As stated above, the mirror positions are controlled by a
`controller 50 in response to a routing command 60 from an
`external source. Basically, the routing command instructs
`the controller as to Which output ?ber to connect to an input
`?ber. The routing command 60 may be a leading command
`received on an input ?ber or may be received from some
`other external source. Upon receipt of the command, the
`controller 50 performs a coarse adjustment of the mirrors to
`put the mirrors into proper position. HoWever, to optimiZe
`the position of the mirrors so that the optical signal is
`optimally connected betWeen the input ?ber and the output
`?ber, the positions of the mirrors are monitored. This is
`accomplished indirectly by monitoring and comparing the
`optical signals in the input ?ber and output ?ber. For this
`purpose, the controller 50 is connected to the OTUs
`200a—200d and the controller monitors the signal sent to the
`OXC fabric in the input ?ber and the signal exiting the OXC
`fabric in the output ?ber. More speci?cally, the controller 50
`is connected to the electrical signal present in each OTU
`Which represents the optical signal that is sent to, in the case
`of the input ?ber 14a—14b, or received from, in the case of
`the output ?ber 14c—14d, the OXC 100. The controller 50
`then compares the input signal to the output signal. If the
`difference betWeen the values of the optical signal in the
`output ?ber and the input ?ber exceeds a threshold value, the
`controller 50 adjusts the position of the mirrors in an attempt
`to correct or minimiZe the difference betWeen the signals.
`As mentioned above, the OTUs 200a—200d are required
`components in an OXC 100 for assuring signal quality.
`Accordingly, connecting the controller 50 to the OTU to
`provide the control signal for determining the correct mirror
`position does not require the addition of any further com
`ponents to the OXC fabric 100.
`FIG. 2 additionally shoWs a detailed vieW of OTU 200b
`on the input ?ber 14b of the I/O ?bers and a detailed vieW
`of OTU 200d on the output ?ber 14d. Each OTU 200a—200d
`includes an Optical-to-Electrical converter 202, a regenera
`tion device 204, and an Electrical-to-Optical converter 206.
`The connection in the OTUs 200a—200b of the input ?bers
`14a, 14b is made at the point at Which the electrical signal
`is connected to the Electrical-to-Optical converter 206. An
`electrical connection in the OTUs 200c—200a' of the output
`?ber 14c, 14d is made at the point at Which the electrical
`signal is connected to the Optical-to-Electrical converter
`202. The electrical signals are thereby connected to the
`controller 50 and monitored for each I/O ?ber. Accordingly,
`When an optical signal is being transmitted from one ?ber to
`another in the OXC, the controller 50 monitors the signals
`in the input and output ?bers to determine if the signal is
`being optimally transmitted and to adjust the mirrors accord
`ingly.
`Thus, While there have shoWn and described and pointed
`out fundamental novel features of the invention as applied to
`preferred embodiments thereof, it Will be understood that
`various omissions and substitutions and changes in the form
`and details of the devices illustrated, and in their operation,
`may be made by those skilled in the art Without departing
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`from the spirit of the invention. For example, it is expressly
`intended that all combinations of those elements and/or
`method steps Which perform substantially the same function
`in substantially the same Way to achieve the same results are
`Within the scope of the invention. Moreover, it should be
`recogniZed that structures and/or elements and/or method
`steps shoWn and/or described in connection With any dis
`closed form or embodiment of the invention may be incor
`porated in any other disclosed or described or suggested
`form or embodiment as a general matter of design choice. It
`is the intention, therefore, to be limited only as indicated by
`the scope of the claims appended hereto.
`We claim:
`1. An optical crossconnect device, comprising:
`an input ?ber;
`an output ?ber;
`an array of tiltable mirrors comprising a plurality of
`mirrors, each mirror being tiltable about at least one
`tilting axis for directing a signal received from said
`input ?ber to said output ?ber;
`a controller operatively connected to said array of tiltable
`mirrors for positioning said mirror of said array of
`tiltable mirrors about said at least one tilting axis so that
`an input signal received from said input ?ber is directed
`toWard said output ?ber; and
`an input buffer connected to said input ?ber and an output
`buffer connected to said output ?ber, said controller
`being connected to said input buffer and to said output
`buffer for monitoring an input optical signal transmitted
`from said input ?ber to said array of mirrors and for
`monitoring an output optical signal received by said
`output ?ber from said array of mirrors, and said con
`troller being operatively connected to said array of
`mirrors for operatively adjusting a position of said
`mirror of said array of mirrors in response to a moni
`tored difference betWeen said input optical signal in
`said input buffer and said output optical signal in said
`output buffer.
`2. The device of claim 1, Wherein said input buffer
`comprises an input optical translation unit connected to said
`input ?ber for regenerating an optical signal in said input
`?ber and said output buffer comprises an output optical
`translation unit for regenerating an optical signal in said
`output ?ber.
`3. The device of claim 2, Wherein each of said input
`optical translation device and said output optical translation
`device comprises an optical-to-electrical converter for con
`verting an optical signal to an electrical signal, a regenera
`tion unit for receiving the electrical signal and regenerating
`the electrical signal, and an electrical-to-optical converter to
`converting the regenerated signal back to an optical signal.
`4. The device of claim 3, Wherein said controller is
`connected to said electrical signal in said input optical
`translation device betWeen said regeneration unit and said
`electrical-to-optical converter and said controller is con
`nected to said electrical signal in said output optical trans
`lation device betWeen said optical-to-electrical converter
`and said regeneration unit.
`5. The device of claim 1, Wherein said input ?ber com
`prises an array of input ?bers and said output ?ber comprises
`an array of output ?bers.
`6. The device of claim 1, Wherein said array of tiltable
`mirrors comprises a plurality of tiltable mirrors, each of said
`tiltable mirrors being rotatable about tWo relatively perpen
`dicular axes.
`7. The device of claim 1, Wherein said controller is
`connected for receiving a routing command and includes
`
`Petitioner Ciena Corp. et al.
`Exhibit 1007-5
`
`

`

`US 6,507,421 B1
`
`5
`means for coarsely adjusting said mirrors of said array of
`mirrors in response to said routing command and for ?nely
`adjusting a position of said mirrors of said array of mirrors
`in response to the monitored difference betWeen said input
`optical signal in said input buffer and said output optical
`signal in said output buffer.
`8. The device of claim 1, further comprising a re?ector,
`Wherein said tiltable mirrors are positionable so that the
`input signal received from said input ?ber is directed toWard
`said output ?ber via said re?ector.
`9. A method of controlling a mirror position in a optical
`crossconnect fabric comprising an array of tiltable mirrors,
`said optical crossconnect fabric receiving a plurality of I/O
`?bers each including an optical translation unit for regen
`erating an optical signal, Wherein said tiltable mirrors are
`operable for directing the optical signal from an input one of
`the plurality of I/O ?bers to an output one of the plurality of
`I/O ?bers, said method of controlling a mirror position
`comprising the steps of:
`monitoring a level of an optical signal being transmitted
`to the array of tiltable mirrors in the optical translation
`unit from the input one of the plurality of ?bers;
`monitoring a level of an optical signal directed from the
`array of tiltable mirrors in the optical translation unit to
`the output one of the plurality of ?bers;
`comparing the monitored input optical signal to the moni
`tored output optical signal to calculate a difference
`betWeen the monitored input optical signal and the
`monitored output optical signal;
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`determining Whether the calculated difference betWeen
`the monitored input optical signal and the monitored
`output optical signal is greater than a predetermined
`threshold level; and
`adjusting the array of mirrors to minimiZe the calculated
`difference betWeen the monitored input optical signal
`and the monitored output optical signal if it is deter
`mined in said step of determining that the calculated
`difference betWeen the monitored input optical signal
`and the monitored output optical signal is greater than
`the threshold level.
`10. The method of claim 9, Wherein the optical translation
`units each include an optical-to-electrical converter for
`converting the optical signal into an electrical signal, and
`Wherein each of said steps of monitoring a level of an optical
`signal from the input one of the plurality of ?bers and of
`monitoring a level of an optical signal directed to the output
`one of the plurality of ?bers includes monitoring the elec
`trical signal in the optical translation units.
`11. The method of claim 9, Wherein said step of adjusting
`the array of mirrors comprises coarsely adjusting the array
`of mirrors in response to an eXternal routing command and
`?nely adjusting said array of mirrors in response to the
`calculated difference betWeen the monitored input optical
`signal and the monitored output optical signal.
`
`Petitioner Ciena Corp. et al.
`Exhibit 1007-6
`
`