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`PROVISIONAL APPLICATION under 37 C.F.R. §1.53(c)
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`TRANSMITTAL FORM
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`Docket Number: TI-30693P
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`
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`EIIMJEII.lllllllllllllllllllllllllllllliOld'3'l'lEli-‘JV
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`Box Pmvisimal Pam“ Application
`Assistant Commissioner For Pmm
`Washington, D.C. 20231
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`Examiner:
`
`Enclosed application parts are:
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`5
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`"EXPRESS MAILING" lldeiling Label Nu. EL356819491u3
`Date of Deposit. November 30. 2000.
`7
`7,
`7 W7
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`,
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`WE,
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`X_ Spec wl Claims
`— Spec w/o Claims
`Formal Drawings
`Informal Drawings
`Other:
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`Number of Pages
`Number of Pages
`Number of Sheets
`Number of Sheets
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`LAST NAME
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`INITIAL
`MIDDLE
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`RESIDENCE (City, State or Foreign Country)
`3215 San Leandro Dr, Dallas, TX 75218
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`PHONE: (972) 9|?-4379
`FAX:
`(972) 917-4418
`
`CORRESPONDENCE ADDRESS:
`
`Charles A. Brill
`Texas Instruments Incorporated
`P.0. Box 655474, MS 3999
`Dallas, Texas T5265
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`Was this invention made under a Govemrnenl contract?
`
`Identify contract and the Govemment agency:
`
`Please charge $150.00 to Deposit Account No. 20-0668.
`An original and two copies are enclosed.
`
`Respectfully submitted,
`
`~
`Charles A. Brill
`Reg. No. 37,786
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`PROVISIONAL APPLICATION ONLY
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-1
`
`
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`MICROMIRROR WAVELENGTH EQUALIZER
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`FIELD or THE INVENTION
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`This invention relates to the field of optical systems, particularly to fiber optic
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`communication systems.
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`BACKGROUND OF THE INVENTION
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`Modulated light beams carry infonnation in fiber optic communication systems. A single
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`fiber carries several light beams, and therefore several separate information streams. Each light
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`beam in the fiber has a unique wavelength. When necessary, the light beams are separated by
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`wavelength and routed to their particular destination. Through the course of the network,
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`various wavelengths come from different sources and along different paths. This typically
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`results in the different wavelengths having different amplitudes.
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`When the various amplitudes have different wavelengths, optical amplification is
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`difficult. An unequalized signal passing through an optical amplifier remains unequalized. The
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`disparity between the various signals can become even worse upon amplification. EFDA are the
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`amplifier of choice because they have gain across the entire spectrum of interest. When
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`amplified by an EFDA, the stronger signals in the unequalized source are spontaneously
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`matchedfamplified, robbing from the weaker signals.
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`When unequalized signals pass through cascaded amplifiers, the equalization problem
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`cascades as well. The worst case result is that the Weaker signals become weaker and weaker
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`20
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`until the information in the weak signals is not recoverable. What is needed it a method of
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`equalizing the signal strength between the various wavelengths in an optical fiber.
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`TI-30693 - Pagel
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-2
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`
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`SUMMARY OF THE INVENTION
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`Objects and advantages will be obvious, and will in part appear hereinafter and will be
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`accomplished by the present invention which provides a method and system for wavelength
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`equalization. One embodiment of the claimed invention provides a wavelength equalizer. The
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`wavelength equalizer comprises an input waveguide, an output waveguide, a wavelength
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`separation device, and a micromirror array. The wavelength separation device divides the input
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`beam of light into sub-beams. A first sub-array of the micromirrors in the micromirror array are
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`operable between a first and second position. The first position directing light in the sub—beam
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`to the output waveguide, and the second position excluding the light in the sub-beam from the
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`output Waveguide.
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`According to another embodiment of the wavelength equalizer, a method of equalizing a
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`plurality of components of an optical input signal is provided. The method comprises:
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`separating the components, directing each component to a sub-array of a micromirror array,
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`positioning rnicromirrors in each sub-array such that mioromirrors in a first position direct
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`incident light to an output waveguide and rnicromirrors in a second position do not, and
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`combining the sub—bearns into an output beam of light.
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`TI-30693 - Page2
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-3
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`
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`For a more complete understanding of the present invention reference is now made to the
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`following descriptions taken in conjunction with the accompanying drawings, in which:
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`FIGURE 1 is a perspective view of a small portion of a micromirror array of the prior art.
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`FIGURE 2 is an exploded perspective view of a single micromirror element fi'om the
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`Inicromirror array of Figure 1.
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`FIGURE 3 is a schematic view of one embodiment of a wavelength equalizer according
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`to the present invention.
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`FIGURE 4 is a schematic view of one embodiment of a wavelength equalizer according
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`to the present invention using a detector to sense the strength of the input signals.
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`FIGURE 5 is a schematic view of another embodiment of a wavelength equalizer
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`according to the present invention that operates without the use of a fixed mirror.
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`FIGURE 6 is a schematic view of another embodiment of a wavelength equalizer
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`according to the present invention similar to the embodiment of Figure 5, using both a detector
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`and a light trap.
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`FIGURE 7 is a schematic view of another embodiment of a wavelength equalizer
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`according to the present invention that does not require a circulator or other light separation
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`device.
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`FIGURE 8 is a schematic view of another embodiment of a wavelength equalizer
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`according to the present invention using a retro-refleetor and two groups of mirror elements and
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`having an output power monitor.
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`TI-30693 - Page 3
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-4
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`
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`FIGURE 9 is a schematic view of another embodiment of a wavelength equalizer
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`according to the present invention using a retro-reflector and two groups of mirror elements and
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`having an output power monitor.
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`.a:LiiiimaEn:H3:
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`TI-30693 — Page4
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`Petitioner Ciena Corp. et al.
`Exhibit 1008-5
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`
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`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
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`A rnicromirror wavelength equalizer has been developed that allows each signal in a
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`DWDM fiber optic communication system to be individually attenuated. By adjusting the
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`attenuation of each component signal, the composite signal is equalized allowing simple
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`amplification of the signal.
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`The equalizer described below typically uses a micromirror device to attenuate portions
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`of the device. A typical hidden-hinge micromirror 100 is actually an orthogonal array of
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`micromirror cells, or elements. This array often includes more than a thousand rows and
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`colunms of micromirrors. Figure 1 shows a small portion of a micromirror array of the prior art
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`with several mirrors 102 removed to show the underlying mechanical structure of the
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`micromirror array. Figure 2 is an exploded view of a single micromirror element of the prior art
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`further detailing the relationships between the micromirror structures.
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`A micrornirror is fabricated on a semiconductor, typically silicon, substrate 104.
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`Electrical control circuitry is typically fabricated in or on the surface of the semiconductor
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`substrate 104 using standard integrated circuit process flows. This circuitry typically includes,
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`but is not limited to, a memory cell associated with, and typically underlying, each mirror 102
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`and digital logic circuits to control the transfer of the digital image data to the underlying
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`memory cells. Voltage driver circuits to drive bias and reset signals to the mirror superstructure
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`may also be fabricated on the micromirror substrate, or may be external to the rnicromirror.
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`Image processing and formatting logic is also formed in the substrate 104 of some designs. For
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`the purposes of this disclosure, addressing circuitry is considered to include any circuitry,
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`including direct voltage connections and shared memory cells, used to control the direction of
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`rotation of a micromirror.
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`TI-30693 - Pagefi
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-6
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`
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`Some microtnirror configurations use a split reset configuration which allows several
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`micromirror elements to share one memory cell-«thus reducing the number of memory cells
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`necessary to operate a very large array, and making more room available for voltage driver and
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`image processing circuitry on the micrornirror integrated circuit. Split reset is enabled by the
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`bistable operation of a micromirror, which allows the contents of the underlying memory to
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`change Without affecting the position of the mirror 102 when the mirror has a bias voltage
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`applied.
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`The silicon substrate 104 and any necessary metal interconnection layers are isolated
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`fi'on1 the micrornirror superstructure by an insulating layer 106 which is typically a deposited
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`silicon dioxide layer on which the micromirror superstructure is formed. Holes, or vias, are
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`opened in the oxide layer to allow electrical connection ofthe micromirror superstructure with
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`the electronic circuitry formed in the substrate 104.
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`The first layer of the superstructure is a metalization layer, typically the third
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`metalization layer and therefore often called M3. The first two metalization layers are typically
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`required to interconnect the circuitry fabricated on the substrate. The third metalization layer is
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`deposited on the insulating layer and patterned to form address electrodes 110 and a mirror bias
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`connection 112. Some micromirror designs have landing electrodes which are separate and
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`distinct structures but are electrically connects to the mirror bias connection 112. Landing
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`electrodes limit the rotation of the mirror 102 and prevent the rotated mirror 102 or hinge yoke
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`114 from touching the address electrodes 110, which have a voltage potential relative to the
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`mirror 102. If the mirror 102 contacts the address electrodes 110, the resulting short circuit
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`could fuse the torsion hinges 116 or weld the mirror 102 to the address electrodes 110, in either
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`case mining the micrornirror.
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`TI-30693 - Page6
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-7
`
`
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`Since the same voltage is always applied both to the landing electrodes and the mirrors
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`102, the mirror bias connection and the landing electrodes are preferably combined in a single
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`structure when possible. The landing electrodes are combined with the mirror bias connection
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`112 by including regions on the mirror bias/reset connection 112, called landing sites, which
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`mechanically limit the rotation of the mirror 102 by contacting either the mirror 102 or the
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`torsion hinge yoke 114. These landing sites are ofien coated with a material chosen to reduce the
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`tendency of the mirror 102 and torsion hinge yoke 114 to stick to the landing site.
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`Mirror bias/reset voltages travel to each mirror 102 through a combination ofpaths using
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`both the mirror bias/reset metalization 1 [2 and the mirrors and torsion beams of adjacent mirror
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`elements. Split reset designs require the array ofmirrors to be subdivided into multiple
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`subarrays each having an independent mirror bias connection. The landing electrodefmirror bias
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`i=5 5
`5 ea
`9%
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`112 configuration shown in Figure l is ideally suited to split reset applications since the
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`
`
`
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`Ii'.'.'.i"+ii“"":'t":iElI"iii?
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`micromirror elements are easily segregated into electrically isolated rows or columns simply by
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`isolating the mirror bias/reset layer between the subarrays. The mirror bias/reset layer ofFigure
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`I is shown divided into rows of isolated elements.
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`A first layer of supports, typically called spacervias, is fabricated on the metal layer
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`forming the address electrodes 110 and mirror bias connections 112. These spacervias, which
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`include both hinge support spacervias 116 and upper address electrode spacervias 118, are
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`typically formed by spinning a thin spacer layer over the address electrodes 110 and mirror bias
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`connections 1 12. This thin spacer layer is typically a 1 pm thick layer ofpositive photoresist.
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`After the photoresist layer is deposited, it is exposed, patterned, and deep UV hardened to form
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`holes in which the spacervias will be formed. This spacer layer and a thicker spacer layer used
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`TI-30693 - Page 7
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-8
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`
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`later in the fabrication process are often called sacrificial layers since they are used only as forms
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`during the fabrication process and are removed from the device prior to device operation.
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`A thin layer of metal is sputtered onto the spacer layer and into the holes. An oxide is
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`then deposited over the thin metal layer and patterned to form an etch mask over the regions that
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`later will form hinges 120. A thicker layer ofmetal, typically an aluminum alloy, is sputtered
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`over the thin layer and oxide etch masks. Another layer of oxide is deposited and patterned to
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`define the hinge yoke 114, hinge cap 122, and the upper address electrodes 124. After this
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`second oxide layer is patterned, the two metals layers are etched simultaneously and the oxide
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`etch stops removed to leave thick rigid hinge yokes 114, hinge caps 122, and upper address
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`electrodes 124, and thin flexible torsion beams 120.
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`A thick spacer layer is then deposited over the thick metal layer and patterned to define
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`holes in which mirror support spacervias 126 will be formed. The thick spacer layer is typically
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`a 2 pm thick layer of positive photoresist. A layer of mirror metal, typically an aluminum alloy,
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`is sputtered on the surface of the thick spacer layer and into the holes in the thick spacer layer.
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`This metal layer is then patterned to form the rrrirrors 102 and both spacer layers are removed
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`using a plasma etch.
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`Once the two spacer layers have been removed, the mirror is free to rotate about the axis
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`formed by the torsion hinge. Electrostatic attraction between an address electrode 110 and a
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`deflectable rigid member, which in effect form the two plates of an air gap capacitor, is used to
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`rotate the mirror structure. Depending on the design of the micrornirror device, the deflectable
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`rigid member is the torsion beam yoke 114, the beam or mirror 102, a beam attached directly to
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`the torsion hinges, or a combination thereof. The upper address electrodes 124 also
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`electrostatically attract the deflectable rigid member.
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`
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`ii.,.iiil...ii
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`TI-30693 - Page8
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-9
`
`
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`The force created by the voltage potential is a function of the reciprocal of the distance
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`between the two plates. As the rigid member rotates due to the electrostatic torque, the torsion
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`beam hinges resist deformation with a restoring torque which is an approximately linear function
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`of the angular deflection of the torsion beams. The structure rotates until the restoring torsion
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`beam torque equals the electrostatic torque or until the rotation is mechanically blocked by
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`contact between the rotating structure and a fixed component. As discussed below, most
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`micrornirror devices are operated in a digital mode wherein sufficiently large bias voltages are
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`used to ensure full deflection of the micrornirror superstructure.
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`Micromiiror devices are generally operated in one of two modes of operation. The first
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`mode of operation is an analog mode, sometimes called beam steering, wherein the address
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`electrode is charged to a voltage corresponding to the desired deflection of the mirror. Light
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`striking the micromirror device is reflected by the mirror at an angle determined by the
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`deflection of the mirror. Depending on the voltage applied to the address electrode, the cone of
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`light reflected by an individual mirror is directed to fall outside the aperture ofan optical system,
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`partially within the aperture, or completely within the aperture.
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`The second mode of operation is a digital mode. When operated digitally, each
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`micrornirror is fully deflected in either ofthe two directions about the torsion beam axis. Digital
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`operation uses a relatively large voltage to ensure the mirror is fully deflected. Since it is
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`advantageous to drive the address electrode using standard logic voltage levels, a bias voltage,
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`typically a negative voltage, is applied to the mirror metal layer to increase the voltage difference
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`between the address electrodes and the mirrors. Use of a sufficiently large mirror bias voltage-
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`a voltage above what is termed the collapse voltage of the device—ensures the mirror will
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`deflect to the closest landing electrodes even in the absence of an address voltage. Therefore, by
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`TI-30693 — Page9
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`
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`
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`'rl...iiii...Eiv,ii31':
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`Petitioner Ciena Corp. et al.
`Exhibit 1008-10
`
`
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`using a large mirror bias voltage, the address voltages need only be large enough to deflect the
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`mirror slightly so that the mirror bias voltage will drive the mirror to the correct landing
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`electrode.
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`Figure 3 is a schematic view of one embodiment of a wavelength equalizer according to
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`the present invention. In Figure 3, light from an optical fiber or other waveguide 302 passes
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`through a circulator 304 and on to an optic 306. The circulator 304, as will be described below,
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`is operable to separate light beams traveling through the circulator 304 based on the polarization
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`of the light. Any light separation device can be used in place of the circulator 304 shown in
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`Figure 3. Afier exiting the circulator 304, the light passes through the optic 306. The optic 306
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`shown in Figure 3 is a collimator lens, but the choice of optic 306 depends on the system.
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`Wavelength separation device 310 can be any type of device, such as a diffraction
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`grating, prism, or other optical component. The grating spatially separates each wavelength
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`carried by the optical fiber 302. The light then passes through a second optic 312, typically a
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`focussing optic. The second optic 312 directs the light to a micrornirror array 314. The input
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`light beam is spatially separated into various sub-beams according to wavelength. While the
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`sub—bearns are generally considered single-wavelength, it should be understood that the sub-
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`beams may have a narrow range of wavelengths, so long as the sub—beams are separated into the
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`various channels used in the fiber optic input.
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`At the micromirror array 314, each sub-beam impinges on several micromirrors. The
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`group of micrornirrors on which a single sub-beam impinges is called a sub—ar-ray. The number
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`of micromirrors receiving a significant amount of light from the sub—bea:m depends on the optical
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`components used by the equalizer, and by the intensity of the sub-beam. The micrornirrors in a
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`sub-array are used to deflect the light striking them. If the micromirrcrs dcflcct light a first
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`TI-30693 - Page 10
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-11
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`
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`direction, the light will travel to a fixed mirror 316, and return to the circulator 304 following the
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`same path it traveled to the fixed mirror 316. If the micro:-nirrors in a sub—array deflect light a
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`second direction 318, the light does not retrace its path. A light trap 320 is often used to control
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`the light traveling along the second direction 318.
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`Other spatial light modulators——for example, various grating light valves or
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`micromechanical shutter devices~may be used in place of the micromirror array 314. The other
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`spatial light modulators typically include arrays of individually controllable elements that are
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`operable in a first position or state and a second position or state to control the reflectivity,
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`including the direction of reflection, or transmittance of the element. A micromirror array 314,
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`however, is an optimal device since it provides precise adjustment of the power levels, reliable
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`operation, and excellent isolation between the first and second mirror positions.
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`In retracing its path to the circulator 304. The return light separated by the circulator 304
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`exits the equalizer through an output fiber or other waveguide 322.
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`In Figure 3, the strength of each sub-beam returning to and exiting from the circulator is
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`determined by the input strength of the sub-beam, by the number of mirrors turned in the first
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`direction, by the degree to which the mirrors are turned in the first direction, and by the location
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`of the mirrors turned in the first direction within the sub-array. The mirrors typically are
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`operated in a digital mode in which a given mirror is either fully rotated in the first direction, or
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`is fully rotated in the second direction. When the mirrors are operated in an analog mode, the
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`degree to which the mirrors are rotated will determine the degree to which the light striking the
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`mirror is reflected by the fixed mirror and returned to the circulator 304. The mirrors near the
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`center of a sub-array receive more of the sub-beam compared to the mirrors farther from the
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`center.
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`TI-30693 - Page 11
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-12
`
`
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`By controlling the mirrors in a given sub—array, the exit strength of the sub~beam
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`corresponding to that sub-array is altered. Thus, by individually altering the position of the
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`mirrors in each sub-array the strength of each exiting sub-beam is altered. The mirrors typically
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`are positioned to equalize the power between each sub-beam traveling through the input and
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`output fibers, but the various sub-beams may be adjusted to have other power levels.
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`Figure 4 is a schematic view of a second embodiment of a wavelength equalizer
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`according to a second embodiment of the disclosed invention. In Figure 4, light fi'orn an optical
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`fiber 302 passes through a circulator 304 and on to an optic 306. Any light separation device can
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`be used in place of the circulator 304 shown in Figure 4. After exiting the circulator 304, the
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`light passes through the optic 306. The optic 306 shown in Figure 4 is a collimator lens, but the
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`choice of optic 306 depends on the system. The light then strikes the wavelength separation
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`device 310.
`
`Wavelength separation device 310 can be any type of device, such as a diffraction
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`grating, prism, or other optical component. The grating spatially separates each wavelength
`
`carried by the optical fiber 302. The light then passes through a second optic 312, typically a
`
`focussing optic. The second optic 312 directs the light to a micromirror array 314. The input
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`light beam is spatially separated into various sub-beams according to wavelength. While the
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`sub-beams are generally considered single-wavelength, it should be understood that the sub-
`
`beams may have a narrow range of wavelengths, so long as the sub-beams are separated into the
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`various channels used in the fiber optic input.
`
`At the micrornirror array 314, each sub-beam impinges on a sub—array of micromirrors.
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`The number of micromirrors receiving a significant amount of light from the sub-beam depends
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`on the optical components used by the equalizer, and by the intensity of the sub-beam. The
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`TI-30693 - Page 12
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-13
`
`
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`micmmirrors in a sub-array are used to deflect the light striking them. If the rnicromirrors
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`deflect light a first direction, the light will travel to a fixed mirror 316, and return to the
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`circulator 304 foilowiug the same path it traveled to the fixed mirror 316. If the rnicromirrors in
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`a sub-array deflect light a second direction 318, the light is directed to a detector 324.
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`In retracing its path to the circulator 304, the return light separated by the circulator 304
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`exits the equalizer through an output fiber 322.
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`In Figure 4, the strength of each sub-beam returning to and exiting from the circulator is
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`determined by the input strength of the sub-beam, by the number of mirrors turned in the fi1'SlZ
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`direction, by the degree to which the mirrors are turned in the first direction, and by the location
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`of the mirrors turned in the first direction within the sub-array. The mirrors typically are
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`operated in a digital mode in which a given mirror is either fully rotated in the first direction, or
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`is fiilly rotated in the second direction. When the mirrors are operated in an analog mode, the
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`degree to which the mirrors are rotated will detennine the degree to which the light striking the
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`mirror is reflected by the fixed mirror and returned to the circulator 304. The mirrors near the
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`center of a sub—array receive more of the sub-beam compared to the mirrors farther from the
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`center.
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`By controlling the mirrors in a given sub—array, the exit strength of the sub—bearn
`
`corresponding to that sub-array is altered. Thus, by individually altering the position of the
`
`mirrors in each sub-array the strength of each exiting sub-beam is altered. The mirrors typically
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`are positioned to equalize the power between each sub-beam traveling through the input and
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`output fibers, but the various sub—‘oeams may be adjusted to have other power levels.
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`The detector 324 of Figure 4 allows monitoring ofthe light dumped out of the return path
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`by the mirror array 314. The detector processor 326 reads the signal from the detector and
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`TI-30693 - Page 13
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-14
`
`
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`provides a signal to controller 328. By knowing the number and location of the mirrors from a
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`given sub-array rotated in the second direction, and the strength of the signal received by the
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`detector, the detector controller 328 can determine the input and output strengths of the signal
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`corresponding to that sub-array. The controller 328 determines which mirrors are rotated in the
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`first and second directions so that a given signal has the proper signal strength at the output.
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`Alternatively, the controller not only receives signals from the detector processor 326,
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`but also from an external source. The external source provides various information including,
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`for purposes of illustration, information about the input signal strength of one or more sub-beams
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`and information of the desired output signal strength for one or more sub-beams. Thus, the
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`external source can indicate that a given sub—bearn should have a particular output signal
`
`strength suited to its prospective signal path.
`
`Figure 5 is a schematic view of another embodiment of a wavelength equalizer according
`
`to another embodiment of the disclosed invention. The embodiment shown in Figure 5 does not
`
`require a fixed mirror, but instead tilts the mieromirror array 314 at the proper angle to direct
`
`light striking mirrors in a first position along the return path. In Figure 5, as in the prior
`
`embodiments, light from an optical fiber 302 passes through a circulator 304 and on to an optic
`
`306. Any tight separation device can be used in place of the circulator 304 shown in Figure 5.
`
`After exiting the circulator 304, the light passes through the optic 306. The optic 306 shown in
`
`Figure 5 is a collimator lens, but the choice of optic 306 depends on the system. The light then
`
`strikes a wavelength separation device 310.
`
`Wavelength separation device 310 can be any type of device, such as a diffraction
`
`grating, prism, or other opticat component. The grating spatially separates each wavelength
`
`carried by the optical fiber 302. The light then passes through a second optic 312, typically a
`
`TI-30693 - Page 14
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-15
`
`
`
`focussing optic. The second optic 312 directs the light to a micromirror array 314. The input
`
`light beam is spatially separated into various sub—bean1s according to wavelength. While the
`
`sub-beams are generally considered single-wavelength, it should be understood that the sub-
`
`heams may have a narrow range ofwavelengths, so long as the sub-beams are separated into the
`
`various channels used in the fiber optic input.
`
`At the rnicromirror array 314, each sub-beam impinges on a sub-array of micromirrors.
`
`The number of micromirrors receiving a significant amount of light from the sub—beam depends
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`on the optical components used by the equalizer, and by the intensity of the sub—bearn. If the
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`rnicromirrors in a given sub-array are in a first position, the light striking the micromirrors is
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`reflected back to optic 312 and returns to the circulator 304 along the same path it traveled to the
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`rnicrornirror array 314. If the rnicrornirrors in a sub-array deflect light a second direction 318,
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`the light is directed to a light trap 320.
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`In retracing its path to the circulator 304, the return light separated by the circulator 304
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`exits the equalizer through an output fiber 322.
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`In Figure 5, as in the prior embodiments, the strength of each sub-beam returning to and
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`exiting from the circulator is determined by the input strength ofthe sub—beam, by the number of
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`mirrors tumed in the first direction, by the degree to which the mirrors are turned in the first
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`direction, and by the location of the mirrors turned in the first direction within the sub—array.
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`The mirrors typically are operated in a digital mode in which a given mirror is either fully
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`rotated in the first direction, or is fully rotated in the second direction. When the mirrors are
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`operated in an analog mode, the degree to which the mirrors are rotated will determine the
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`degree to which the light striking the mirror is reflected by the fixed mirror and returned to the
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`TL30693 — Page 15
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-16
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`
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`circuiator 304. The mirrors near the center of a sub-array receive more of the sub-beam
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`compared to the mirrors farther from the center.
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`By controlling the mirrors in a given sub-array, the exit strength of the sub-beam
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`corresponding to that sub-array is altered. Thus, by individually altering the position of the
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`mirrors in each sub-array the strength of each exiting sub-beam is altered. The mirrors typically
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`are positioned to equalize the power between each sub-beam traveling through the input and
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`output fibers, but the various sub—beams may be adjusted to have other power levels.
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`Figure 6 is a schematic view of another embodiment of a wavelength equalizer according
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`to another embodiment of the disclosed invention. The embodiment shown in Figure 6 does not
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`require a fixed mirror, but instead tilts the micromirror array 314 at the proper angle to direct
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`light striking mirrors in a first position along the return path. In Figure 6, as in the prior
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`embodiments, light from an optical fiber 302 passes through a circulator 304 and on to an optic
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`306. Any light separation device can he used in place of the circulator 304 shown in Figure 6.
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`After exiting the circulator 304, the light passes through the optic 306. The optic 306 shown in
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`Figure 6 is a collimator lens, but the choice of optic 306 depends on the system. The light then
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`strikes a wavelength separation device 310.
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`Wavelength separation device 310 can be any type of device, such as a diffraction
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`grating, prism, or other optical component. The grating spatially separates each wavelength
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`carried by the optical fiber 302. The light then passes through a second optic 312, typically a
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`focussing optic. The second optic 312 directs the light to a rnicromirror array 314. The input
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`light beam is spatially separated into various sub-beams according to wavelength. While the
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`sub-beams are generally considered single-wavelength, it should be understood that the sub-
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`bearns may have a narrow range of wavelengths, so long as the sub-beams are separated into the
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`‘.57-
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`Ha=_=
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`Tl-30693 - Page 16
`
`Petitioner Ciena Corp. et al.
`Exhibit 1008-17
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`
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`various channels used in the fiber optic input. In Figure 6, each light beam and sub~beam is
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`shown as a single ray. Thus, Figure 6 shows three separate sub-beams afier the wavelength
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`separation device.
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`At the microniirror array 314, each sub-beam impinges on a sub-array of rnicromirrors.
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`The number of tnicromirrors receiving a significant amount of light from the sub-beam depends
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`on the optical components used by the equalizer, and by the intensity of the sub—beam. If the
`
`rnicrornirrors in a given sub-array are in a first position, the light striking the micromirrors is
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`reflected back to optic 312 and returns to the circulator 304 along the same path it traveled to the
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`rriicromirror array 314. If the micromirrors in a sub-array deflect light a second direction 318,
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`the light is directed to a light trap 320. If the micromirrors in a third position, typically a flat
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`position parallel with the plane of the rnicrornirror array 314. the light is directed to a detector
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`324.
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`K.:-'-...1=i¢
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`'.._i{,..|!ll...tiamit'.‘.i..Il-
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`In retracing its path to the circulator 304, the return light separated by the circulator 304
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`exits the equalizer through an output fiber 322.
`
`In Figure 6, as in the prior embodiments, the strength of each sub-beam returning to and
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`exiting from the circulator is determined by the input strength of the sub-beam, by the number of
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`mirrors turned in the first direction, by the degree to