Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D. (Exhibit 1016)
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`UNITED STATES PATENT AND TRADEMARK OFFICE
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`
`
`BEFORE THE PATENT TRIAL AND APPEAL BOARD
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`FUJITSU NETWORK COMMUNICATIONS, INC.
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`Petitioner
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`v.
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`CAPELLA PHOTONICS, INC.
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`Patent Owner
`
`
`
`Inter Partes Review Case No. Unassigned
`Patent No. RE42,678
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`
`
`
`
`DECLARATION OF TIMOTHY J. DRABIK, Ph.D.
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`
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`Mail Stop “PATENT BOARD”
`Patent Trial and Appeal Board
`U.S. Patent and Trademark Office
`P.O. Box 1450
`Alexandria, VA 22313-1450
`
`FNC 1016
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`

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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`TABLE OF CONTENTS
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`B. 
`
`INTRODUCTION ........................................................................................... 1 
`A. 
`Background ........................................................................................... 1 
`B. 
`Qualifications ........................................................................................ 3 
`1. 
`Education .................................................................................... 3 
`2. 
`Career History ............................................................................ 3 
`3. 
`Publications ................................................................................ 5 
`4. 
`Other Relevant Qualifications .................................................... 6 
`THE ‘678 PATENT ........................................................................................ 7 
`II. 
`III.  LIST OF DOCUMENTS CONSIDERED IN FORMULATING MY
`OPINION ........................................................................................................ 8 
`IV.  TECHNICAL BACKGROUND ................................................................... 10 
`A.  Optical switching for telecommunications ......................................... 10 
`1. 
`Fiber cross-connects ................................................................. 10 
`2.  Wavelength switches ................................................................ 12 
`Free-space optical systems ................................................................. 14 
`1. 
`Basic properties of lenses ......................................................... 14 
`2. 
`Gaussian light beams ................................................................ 16 
`3. 
`The “Fourier lens” .................................................................... 19 
`4. 
`Concave mirrors as focusing elements ..................................... 20 
`5.  Wavelength-dispersive elements .............................................. 21 
`STATE OF THE ART AT THE TIME OF THE ALLEGED
`INVENTION ................................................................................................. 25 
`A. 
`Transparent optical switching prior to the alleged invention ............. 25 
`B. 
`Reconfigurable Optical Add-Drop Multiplexers ................................ 26 
`C.  Wavelength Selective Switches .......................................................... 27 
`D.  MEMS Mirrors ................................................................................... 29 
`VI.  PERSON OF ORDINARY SKILL IN THE ART ........................................ 32 
`VII.  OVERVIEW OF THE ‘678 PATENT .......................................................... 32 
`A.  Operation of the disclosed system of the ’678 Patent ........................ 33 
`i
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`V. 
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`I. 
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`VIII.  THE CLAIMS OF THE ‘678 PATENT ....................................................... 35 
`IX.  LEGAL STANDARDS ................................................................................. 36 
`A.  Anticipation ........................................................................................ 36 
`B. 
`Obviousness ........................................................................................ 37 
`CLAIM CONSTRUCTION .......................................................................... 42 
`X. 
`XI.  ANALYSIS OF INVALIDITY .................................................................... 44 
`A. 
`Summary of Analysis ......................................................................... 44 
`B. 
`Point 1: Claims 61-65 Are Disclosed by Smith .................................. 46 
`1. 
`Operation of the disclosed system of Smith ............................. 46 
`2. 
`Claim 61 ................................................................................... 51 
`3. 
`Claim 62 ................................................................................... 53 
`4. 
`Claim 63 ................................................................................... 53 
`5. 
`Claim 64 ................................................................................... 53 
`6. 
`Claim 65 ................................................................................... 54 
`Point 2: Claims 1–4, 9, 10, 13, 17, 19-23, 27, 29, 44–46 and 53
`Are Not Innovative in View of Smith and Carr ................................. 54 
`1. 
`Claim 1 preamble ..................................................................... 57 
`2. 
`Claim 1 – collimators and ports ............................................... 57 
`3. 
`Claim 1 – wavelength separator ............................................... 58 
`4. 
`Claim 1 – beam focuser ............................................................ 58 
`5. 
`Claim 1 – channel micromirrors ............................................... 58 
`6. 
`Claim 2 ..................................................................................... 59 
`7. 
`Claim 3 ..................................................................................... 60 
`8. 
`Claim 4 ..................................................................................... 60 
`9. 
`Claim 9 ..................................................................................... 60 
`10.  Claim 10 ................................................................................... 61 
`11.  Claim 13 ................................................................................... 61 
`12.  Claim 17 ................................................................................... 61 
`13.  Claim 19 ................................................................................... 62 
`14.  Claim 20 ................................................................................... 62 
`ii
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`C. 
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`D. 
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`E. 
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`F. 
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`15.  Claim 21 ................................................................................... 62 
`16.  Claim 22 ................................................................................... 63 
`17.  Claim 23 ................................................................................... 64 
`18.  Claim 27 ................................................................................... 64 
`19.  Claim 29 ................................................................................... 64 
`20.  Claim 44 ................................................................................... 64 
`21.  Claim 45 ................................................................................... 66 
`22.  Claim 46 ................................................................................... 66 
`23.  Claim 53 ................................................................................... 66 
`Point 3: Claims 1, 9, 10, 13, 17, 19, 44, 53, 61, 64 and 65 Are
`Not Innovative in View of Bouevitch and Carr .................................. 66 
`1. 
`Operation of the disclosed system of Bouevitch ...................... 67 
`2. 
`Combination of Bouevitch with Carr ....................................... 70 
`Point 4: Claims 1-4, 19-23, 27, 29, 44-46 and 61-63 Are Not
`Innovative in View of Bouevitch and Sparks ..................................... 89 
`Points 5 and 6: Claims 61–65 Are Not Innovative in View of
`the Combination of Smith and Tew and Claims 1–4, 9, 10, 13,
`17, 19–23, 27, 29, 44–46 and 53 Are Not Innovative in View of
`the Combination of Smith, Carr and Tew ......................................... 109 
`Point 7: Claims 1, 9, 10, 13, 17, 19, 44, 53, 61, 64 and 65 Are
`Not Innovative in View of the Combination of Bouevitch, Carr
`and Tew ............................................................................................. 113 
`Point 8: Claims 1–4, 20, 27, 44–46 and 61–63 Are Not
`Innovative in View of the Combination of Bouevitch, Sparks
`and Tew ............................................................................................. 114 
`XII.  CONCLUSION ........................................................................................... 115 
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`G. 
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`H. 
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`I, Timothy J. Drabik, hereby declare as follows:
`
`I.
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`INTRODUCTION
`A. Background
`1. My name is Timothy J. Drabik. I am a researcher and consultant
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`working in areas related to optics, telecommunications, display technologies, and
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`microelectronics. I undertake consulting through my company, Page Mill
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`Technology Corporation, and also work to develop commercial technologies for
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`information display and optical telecommunications.
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`2.
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`I have been retained to act as an expert witness on behalf of Fujitsu
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`Network Communications, Inc. (“FNC” or “Petitioner”) in connection with the
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`above captioned Petition for Inter Partes Review of U.S. Patent No. RE42,678
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`(“Petition”). I understand that this proceeding involves U.S. Patent No. RE42,678
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`(“the ‘678 Patent”), titled “Reconfigurable Optical Add-Drop Multiplexers with
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`Servo-Control and Dynamic Spectral Management Capabilities.” The ‘678 Patent
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`is provided as Exhibit 1001.
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`3.
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`I understand that Petitioner challenges the validity of Claims 1–4, 9,
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`10, 13, 17, 19–23, 27, 29, 44–46, 53 and 61–65 of the ‘678 Patent (the “challenged
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`claims”).
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`1
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`I have reviewed and am familiar with the ‘678 Patent as well as its
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`4.
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`prosecution history. The ‘678 prosecution history is provided as Exhibit 1002.
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`Additionally, I have reviewed materials identified in Section III.
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`5.
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`As set forth below, I am familiar with the technology at issue as of
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`both the August 23, 2001 filing date of the application which led to the ‘678
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`Patent, and the March 19, 2001 priority date corresponding to the filing of
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`Provisional Patent Application No. 60/277,217. I have been asked to provide my
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`technical review, analysis, insights, and opinions regarding the prior art references
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`that form the basis for the Petition. In forming my opinions, I have relied on my
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`own experience and knowledge, my review of the ‘678 Patent and its file history,
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`and of the prior art references cited in the Petition.
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`6. My opinions expressed in this Declaration rely to a great extent on my
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`own personal knowledge and recollection. However, to the extent I considered
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`specific documents or data in formulating the opinions expressed in this
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`Declaration, such items are expressly referred to in this Declaration.
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`7.
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`I am being compensated for my time in connection with this IPR at
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`my standard consulting rate, which is $500 per hour.
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`B. Qualifications
`1.
`Education
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
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`8.
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`I received my Ph.D. in Electrical Engineering from the Georgia
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`Institute of Technology in 1990, where I also received a M.S. degree in Electrical
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`Engineering in 1982. I received Bachelor’s degrees in Electrical Engineering and
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`in Mathematics from Rose-Hulman Institute of Technology in 1981; I also
`
`received certification in technical translation of German to English.
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`2.
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`Career History
`
`9.
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`I have over thirty years of experience in the areas of optics and optical
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`engineering, optoelectronics, telecommunications, liquid crystal display
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`technology, signal and image processing for video applications, microelectronics
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`and integrated circuit design, device packaging, digital systems, and high-
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`performance computing. I have worked both in the academic and industrial
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`environments.
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`10.
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`I held Assistant Professor and Associate Professor appointments at
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`Georgia Tech through the 1990s in electrical and computer engineering, and
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`Visiting and Consulting Professorships at Stanford University from 1999 to 2009.
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`I have taught courses in a broad range of areas, run a research laboratory, and
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`graduated Ph.D. students. I have done research program development with
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`government and industrial entities in the U.S., France, the UK, and other countries.
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`I also have worked for a number of companies. I have been employed directly by
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`AT&T Bell Labs, Displaytech, Inc., Sun Microsystems, and Spectralane, Inc.
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`Among my past consulting clients are the NASA Jet Propulsion Laboratory,
`
`Siemens Corporate Research, and early-stage investors performing due diligence
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`prior to making investment decisions.
`
`11. At AT&T Bell Labs in the early 1980s, I worked in a department that
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`was developing technologies and services for fiber-to-the home systems. Voice,
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`data, and television content were provided. I designed hardware and also
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`investigated options for video bandwidth compression and coding.
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`12. As a graduate student, I developed technologies for controlling arrays
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`of optical switches integrated with silicon chips. One of these technologies
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`combined ferroelectric liquid crystals (LCs) on silicon integrated circuit chips
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`(LCOS), and formed the basis for the microdisplays I developed later.
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`13. At Georgia Tech and Stanford, I directed research activity in liquid
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`crystal microdisplay technology, diffractive optics, optoelectronic packaging and
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`hybrid integration, and high-speed interconnection of digital systems, and
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`graduated four Ph.D. students working in these areas. Specifically, I conducted
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`research with Displaytech, Inc., which led to the development of commercial
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`liquid-crystal-on-silicon microdisplays. I developed new manufacturing
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`technology, designed the underlying pixel array and peripheral/driver circuitry for
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`a dozen designs, and tested and evaluated displays. I also taught courses in digital
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`signal processing, Fourier optics and holography, optical information processing,
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`information theory, pattern recognition, semiconductor electronics, integrated
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`circuit design, linear system theory, operational mathematics, and other areas, at
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`the undergraduate and graduate levels.
`
`14. As Director of Telecommunications with Displaytech, I developed
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`liquid crystal devices and designed subsystems for transparent optical switching
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`and signal restoration for single-mode, long haul optical transmission. This work
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`entailed development of new optical switch architectures as well as investigation of
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`new liquid crystal component manufacturing technologies to meet the strenuous
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`reliability requirements of the optical telecommunication industry. In particular, I
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`worked in the 2000 time frame to develop optical add/drop multiplexor subsystems
`
`based on liquid crystal on silicon (LCOS) technology.
`
`3.
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`Publications
`
`15.
`
`I have published more than 30 articles in scholarly journals, and am
`
`the first named inventor on four U.S. Patents. I have also delivered invited
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`addresses to the U.S.–Japan Joint Optoelectronics Project Expert Workshop
`
`(Makuhari, Japan), the Scottish Optoelectronics Association and Institute of
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`Physics Meeting on Optical Interconnections for Information Processing
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`(Edinburgh, Scotland), the Annual Meeting of the Materials Research Society (San
`
`Francisco, CA), and the IEEE/LEOS Workshop on Interconnections within High-
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`
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`Speed Digital Systems (Santa Fe, NM). I have served the European Union as an
`
`Expert Reviewer for EU research programs in microelectronics and optics, and the
`
`National Science Foundation as a reviewer of research proposals.
`
`4. Other Relevant Qualifications
`16. My consulting practice has involved the design of optoelectronic
`
`integrated systems on custom silicon platforms, development of new liquid crystal
`
`cell technology and manufacturing technology, investigation of advanced
`
`processor–memory architectures for high-performance parallel computing, and
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`development of long-haul optical fiber transmission subsystems. Specifically, for
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`Spectralane, Inc., a Silicon Valley startup pursuing disruptive techniques for
`
`ameliorating nonlinear impairments in long-haul, wavelength-division-multiplexed
`
`fiber systems, I developed simulation and modeling tools to aid in subsystem
`
`design, used those tools to develop effective subsystem architectures, and drafted
`
`patents.
`
`17. My practice also has involved preparing U.S. Patent applications,
`
`providing patent infringement and validity studies and reports, and conducting
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`intellectual property due diligence investigations in connection with venture
`
`financing. I have previously served as an expert in litigation matters relating to
`
`(among other areas) optical switching, optical fiber transmitter and receiver
`
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`components, video processing technologies, the design, fabrication, and operation
`
`of liquid crystal displays, and optical disk drive technologies.
`
`18. My curriculum vitae, Exhibit 1017, includes a compilation of my
`
`publications and patents, lists litigation matters in which I have been engaged, and,
`
`in particular, includes those in which I have provided testimony over the previous
`
`four years.
`
`II. THE ‘678 PATENT
`19. The above-referenced IPR petition seeks review of U.S. Patent No.
`
`RE42,678 (“the ‘678 Patent”), Ex. 1001. U.S. Application No. 09/938,426, now
`
`U.S. Patent No. 6,625,346, was filed on August 23, 2001, and claims priority to
`
`U.S. Provisional Application No. 60/277,217, filed on March 19, 2001. U.S.
`
`Patent No. RE39,397, filed on December 31, 2004, is a reissue of U.S. Patent No.
`
`6,625,346. The ‘678 Patent, filed on June 15, 2010, is a reissue of U.S. Patent No.
`
`RE39,397. I understand that the ‘678 Patent is currently assigned to Capella
`
`Photonics, Inc. (“Capella”).
`
`20. The technology related to the claims of the ‘678 Patent has
`
`applications in fiber optic communications as, for example, switches, filters, and
`
`attenuators.
`
`21.
`
`Jeffrey P. Wilde and Joseph E. Davis are listed as the inventors for the
`
`‘678 Patent.
`
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`III. LIST OF DOCUMENTS CONSIDERED IN FORMULATING MY
`OPINION
`22.
`
`In formulating my opinion, I have considered all of the following
`
`documents:
`
`Description
`Exhibit
`Ex. 1001 U.S. Patent No. RE42,678 to Chen et al.
`
`Ex. 1002 U.S. Patent No. 6,498,872 to Bouevitch et al.
`
`Ex. 1003 Prosecution History for U.S. Patent No. RE42,678.
`
`Ex. 1004 Joseph E. Ford et al., Wavelength Add-Drop Switching Using Tilting
`Micromirrors, 17(5) Journal of Lightwave Technology 904 (1999).
`
`Ex. 1005 U.S. Patent No. 6,442,307 to Carr et al.
`
`Ex. 1006 U.S. Patent No. 6,625,340 to Sparks et al.
`
`Ex. 1007 U.S. Patent Publication No. 2002/0081070 to Tew.
`
`Ex. 1008 U.S. Provisional Patent Application No. 60/250,520 to Tew.
`
`Ex. 1009 U.S. Patent No. 6,798,941 to Smith et al. (“Smith”)
`
`Ex. 1010 U.S. Provisional Patent Application No. 60/234,683 to Smith et
`al. (“Smith Provisional”)
`Ex. 1011 J. Alda, “Laser and Gaussian Beam Propagation and Transformation,”
`in Encyclopedia of Optical Engineering, R. G. Driggers, Ed. Marcel
`Dekker, 2003, pp. 999–1013. (“Alda”)
`Ex. 1012 Joint Claim Construction and Prehearing Statement, Capella
`Litigation, Case No. 3:14-cv-03348-EMC, Dkt. 151.
`Ex. 1013 Newton’s Telecom Dictionary (17th ed. 2001) (excerpted).
`
`Ex. 1014 Fiber Optics Standard Dictionary (3rd ed. 1997) (excerpted).
`
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`Ex. 1015 Webster’s New World College Dictionary (3rd ed. 1997) (excerpted).
`
`Ex. 1018 U.S. Patent No. 6,253,001 to Hoen.
`
`Ex. 1019 U.S. Patent No. 6,567,574 to Ma et al.
`
`Ex. 1020 U.S. Patent No. 6,256,430 to Jin et al.
`
`Ex. 1021 U.S. Patent No. 6,631,222 to Wagener et al.
`
`Ex. 1022 U.S. Patent No. 5,414,540 to Patel et al.
`
`Ex. 1023 U.S. Patent Publication No. 2002/0097956.
`
`Ex. 1024 Shigeru Kawai, Handbook of Optical Interconnects (2005) (excerpted).
`
`Ex. 1025 U.S. Patent No. 6,798,992 to Bishop et al.
`
`Ex. 1026 Joseph W. Goodman, Introduction to Fourier Optics, Second Edition,
`McGraw-Hill (1996).
`Ex. 1027 U.S. Patent No. 6,204,946 to Aksyuk et al.
`
`Ex. 1028 L.Y. Lin, “Free-Space Micromachined Optical Switches for Optical
`Networking, IEEE Journal of Selected Topics In Quantum
`Electronics,” Vol. 5, No. 1, pp. 4–9, Jan./Feb. 1999.
`
`Ex. 1029 S.-S. Lee, “Surface-Micromachined Free-Space Fiber Optic Switches
`With Integrated Microactuators for Optical Fiber Communications
`Systems,” in Tech. Dig. 1997 International Conference on Solid-State
`Sensors and Actuators, Chicago, June 16-19, 1997, pp. 85–88.
`Ex. 1030 H. Laor, “Construction and performance of a 576×576 single-stage
`OXC,” in Tech. Dig. LEOS ’99 (vol. 2), Nov. 8–11, 1999, pp. 481–482.
`
`Ex. 1031 R. Ryf, “1296-port MEMS Transparent Optical Crossconnect with 2.07
`Petabit/s Switch Capacity,” in Tech. Dig. OSA Conference on Optical
`Fiber Communication, March 2001, pp. PD28-1–PD28-3.
`Ex. 1032 A. Husain, “MEMS-Based Photonic Switching in Communications
`Networks,” in Tech. Dig. OSA Conference on Optical Fiber
`Communication, 2001, pp. WX1-1–WX1-3.
`
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`Ex. 1033 U.S. Patent No. 5,661,591 to Lin et al.
`
`Ex. 1034 H. Laor et al., “Performance of a 576×576 Optical Cross Connect,”
`Proc. of the Nat’l Fiber Optic Engineers Conference, Sept. 26-30,
`1999.
`Ex. 1035 V. Dhillon. (2012, Sep. 18). Blazes and Grisms. Available:
`http://www.vikdhillon.staff.shef.ac.uk/teaching/phy217/instruments/ph
`y217_inst_blaze.html. (“Dhillon”)
`Ex. 1036 Fianium Ltd. WhiteLase SC480 New Product Data Sheet. Available:
`http://www.fianium.com/pdf/WhiteLase_SC480_BrightLase_v1.pdf.
`(“Fianium”)
`
`
`
`23.
`
`I have reviewed the substance of the Petition for inter partes review
`
`submitted with this Declaration (and I agree with the technical analysis that
`
`underlies the positions set forth in the Petition).
`
`IV. TECHNICAL BACKGROUND
`A. Optical switching for telecommunications
`1.
`Fiber cross-connects
`24. Optical fiber network systems most preferably have a flexible
`
`capability of provisioning so that bandwidth may be reconfigured to accommodate
`
`changes in demand or to recover from faults.
`
`25. At the coarsest level of network provisioning, links originating at
`
`various geographic locations and entering a service facility may be selectively
`
`interconnected with each other to allocate entire fiber paths to link locations. A
`
`traditional way to implement this function is by means of a patch panel, an
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`example of which is pictured below, whereby fibers from various geographic
`
`locations may be connected by installing short patch cables manually.
`
`
`If such changes are frequent, however, the cost and delay of “truck rolls” to bring
`
`technicians to service facilities may become onerous. Therefore, an automated
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`means for whole-fiber provisioning is desirable.
`
`26. The graphic below shows a possible arrangement for what is called a
`
`space-division switch, or space switch, using arrays of computer-controlled
`
`mirrors, that implements the same function as a patch panel.1
`
`
`1 It is desirable for a switch to be bidirectional, i.e., for signals to be routed reliably
`
`from “outputs” to “inputs” as well as from “inputs” to “outputs.” This can
`
`generally be achieved with suitable engineering.
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
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`27. Such a switch may be referred to as an optical cross-connect (OXC).
`
`In operation, the optical signal from an input fiber is collimated by means of a lens
`
`and continues in the form of a pencil-like beam to a dedicated mirror in a first
`
`array. The mirror tilt is adjusted to point the reflected beam at the mirror
`
`corresponding to the desired output fiber. The second mirror is adjusted to point
`
`its reflected beam so that it couples into the output fiber through its collimator.
`
`While two separate mirror arrays are shown in the graphic above, the same concept
`
`may be implemented with a single mirror array. Because the mirrors are under
`
`computer control, no trucks need roll, and network operational costs can be
`
`reduced.
`
`2. Wavelength switches
`28. The granularity of such provisioning is coarse—a single fiber may
`
`carry multiple terabits per second (Tb/s) in each direction—and it is desirable to be
`
`able to allocate smaller chunks of bandwidth among fibers.
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
` Wavelength-division multiplexing (WDM) is used to impress multiple
`
`29.
`
`Tb/s of information onto a single fiber. This is done by dividing the spectrum of
`
`light into wavelength channels, each of which is capable of carrying distinct
`
`information. Because power in different channels does not overlap in wavelength,
`
`a single channel or set of channels may be split off—demultiplexed— from a fiber
`
`by means of wavelength filtering. Many optical techniques for wavelength
`
`selectivity have been employed for wavelength multiplexing and demultiplexing.
`
`Gratings capable of dispersing light by wavelength have been used in this regard to
`
`create devices that can add (or drop) wavelengths or groups of wavelengths to (or
`
`from) a fiber. If individual wavelength channels can be reallocated among fibers,
`
`provisioning can be effected with a granularity of tens of Gb/s.
`
`30. Prior to the alleged invention, it was known to implement wavelength
`
`control in a space switch to effect wavelength provisioning in a remotely
`
`controllable fashion. This can be done by using space switches in conjunction with
`
`wavelength multiplexers and demultiplexers. In the exemplary system shown in
`
`the graphic below, for example, a demux element places each wavelength channel
`
`from a WDM input port onto a distinct optical path. Then, space switches are used
`
`to send each wavelength to a desired destination port. Multiple wavelengths
`
`intended for a destination port are combined by a mux element. Multiplexing and
`
`switching functions can be implemented in various ways.
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`
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`13
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
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`B.
`Free-space optical systems
`31. The art discussed in this Declaration employs optical architectures
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`based at least in part on free-space propagation, i.e., optical propagation that is not
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`confined to a fiber or other kind of waveguide. It is useful to understand the
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`principles by which such systems function.
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`1.
`Basic properties of lenses
`32. Focusing elements such as lenses and concave mirrors are long-
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`known components of free-space optical systems. They groom light emerging
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`from fibers, and they also operate on image fields bearing many independent
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`channels of light.
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`33. The illustration below highlights certain properties of ideal, thin
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`lenses that are exploited in free-space systems. At left is a ray optics picture of
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`propagating beams. An ideal lens is characterized by its focal distance f.
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
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`Rays originating at a focal point (a distance f from the lens center along its axis)
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`are transformed to horizontal rays on the other side of the lens. But also, rays
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`originating at a common point anywhere in a focal plane all are transformed to
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`parallel rays on the other side of the lens. The rays’ common direction may be
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`found by tracing the ray passing through the lens center, which is not deflected.
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`Note that there are no arrows in the ray diagrams to indicate propagation direction:
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`because of the principle of reciprocity, the ray diagrams may be interpreted either
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`for light traveling generally left-to-right or right-to-left. Thus, rays arriving in a
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`common direction also are transformed to pass through the focal plane at a
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`common point. These basic phenomena underlie the imaging properties of lenses.2
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`2 Single-lens imaging is often depicted as illustrated below, according to the
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`equation 1/S1 + 1/S2 = 1/f:
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`34. The image at right in the illustration above shows qualitatively how
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`beams having lateral extent are transformed by lenses. A collimated beam (one
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`having flat wavefronts) many wavelengths in diameter remains substantially
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`collimated until the lens transforms it into a converging beam that attains its
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`minimum spot size in the focal plane, which size may be of the order of a few
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`wavelengths. Reciprocally, a diverging beam emerging, e.g., from a cleaved,
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`single-mode fiber end in the focal plane, is collimated by the lens. Note that the
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`paths of the extended beams’ central axes are the same as in the simple ray picture
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`of lens behavior.3
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`2. Gaussian light beams
`35. Gaussian beams are solutions of a useful approximation to the
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`electromagnetic wave equation and are important in the field of optical switching.
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`3 The colors in the above diagram are provided for illustration only, and are not
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`meant to convey wavelength information. The focal distance of actual physical
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`lenses may vary non-negligibly with wavelength.
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`A radially symmetric Gaussian beam g with waist radius w0 has a field profile at its
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`waist (narrowest point) of the form
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`(cid:1859)(cid:4666)(cid:1876),(cid:1877)(cid:4667)(cid:3404)(cid:1857)(cid:2879)(cid:3045)(cid:3118)/(cid:3050)(cid:3116)(cid:3118)(cid:3404) (cid:1857)(cid:2879)(cid:4666)(cid:3051)(cid:3118)(cid:2878)(cid:3052)(cid:3118)(cid:4667)/(cid:3050)(cid:3116)(cid:3118)
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`The waist radius w0 is the radius r at which the field amplitude takes on 1/e (i.e.,
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`about 37%) of its peak value. The plots below show such a radially symmetric
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`Gaussian profile:
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`The plot below shows a snapshot of the oscillatory field (red for positive, blue for
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`negative) in the vicinity of the waist of a radially symmetric Gaussian beam. The
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`plot would look the same along a y–z section. It is apparent that the wavefront is
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`flat only at the waist, and exhibits converging or diverging behavior elsewhere.
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`The divergence angle of the beam as it propagates past its waist depends on the
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`optical wavelength and on the waist radius:
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`So, for a given wavelength, the divergence angle is practically inversely
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`proportional to the waist radius.
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`36. Lenses alter optical beams by imposing spatially varying delays on the
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`wavefronts incident upon them. The graphic below shows a diverging Gaussian
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`beam being substantially collimated by a converging lens:
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`The thick part of the lens at its axis delays light more than the thinner parts away
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`from the axis, and reduces the curvature of the phase fronts of the beam. A beam
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`with greater focusing power would transform the incident diverging beam to a
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`converging beam.
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`Inter Partes Review of USPN RE42,678
`Declaration of Timothy J. Drabik, Ph.D.
`37. Radially symmetric Gaussian beams are not the most general type of
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`Gaussian beam. Gaussian beams can have elliptical cross section, and beam waists
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`in orthogonal directions may occur at different positions along th