[slide 1]
Claim Construction Tutorial — Plaintiff's Submission
Claim Construction Tutorial — Plaintiff's Submission
Optiwave Semiconductor Corp. v. Lumicore Technologies, Inc.
Case No. 2:24-cv-00319-JRG
United States District Court for the Eastern District of Texas
Before the Honorable Judge James R. Gilstrap
Prepared by Calderwood & Harkness LLP on behalf of Plaintiff Optiwave Semiconductor Corp.
Markman Hearing Scheduled: March 14, 2025
Prepared in coordination with Dr. Caroline Ashford, Professor of Electrical Engineering & Photonics, Northfield Institute of Technology
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Agenda / Roadmap
I. Introduction to Silicon Photonics
II. Optical Waveguides and Waveguide Multiplexing
III. Coherent Optical Transceivers
IV. Thermal Management in Photonic Integrated Circuits
V. Polarization-Diverse Grating Couplers
VI. Mapping Technology Concepts to the Asserted Patents
VII. Person of Ordinary Skill in the Art (POSITA)
VIII. Summary and Key Takeaways
[slide 3]
The Asserted Patents at a Glance
'847 Patent (U.S. 10,234,847): 'Multi-Channel Silicon Photonic Waveguide Multiplexer with Low Insertion Loss' — Filed Sept. 14, 2016; Issued Mar. 19, 2019
'193 Patent (U.S. 10,891,193): 'High-Bandwidth Coherent Optical Transceiver Integrated on Silicon Substrate' — Filed Apr. 7, 2017; Issued Jan. 12, 2021
'562 Patent (U.S. 9,678,562): 'Method for Thermal Management of Photonic Integrated Circuits Using Embedded Micro-Channel Heat Sinks' — Filed Nov. 22, 2014; Issued June 13, 2017
'015 Patent (U.S. 11,402,015): 'Polarization-Diverse Grating Coupler for Silicon Photonic Transceivers' — Filed Aug. 30, 2019; Issued Aug. 2, 2022
The '562 and '847 Patents are in the same patent family (continuation relationship)
The '193 and '015 Patents share a common provisional application (Prov. App. No. 62/499,117, filed Apr. 7, 2017)
Original assignee of '562 Patent was Solara Optics, Inc.; assigned to OWS via asset purchase agreement dated June 15, 2018
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The Accused Products
LumiLink 400G-ZR+ — launched Q3 2022; accused of infringing the '847, '193, and '562 Patents
LumiLink 800G-DR8 — launched Q1 2023; accused of infringing the '847, '193, '562, and '015 Patents
LumiEdge 1600G-LR — launched Q4 2023; accused of infringing the '193 and '015 Patents
All three product lines are silicon-photonics transceiver modules sold by Defendant Lumicore Technologies, Inc. for hyperscale data-center interconnect applications
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Section I: Introduction to Silicon Photonics — What It Is
Silicon photonics: the technology of building optical (light-based) devices on silicon chips using standard semiconductor fabrication processes
Merges the data-carrying capacity of light with the manufacturing scale and cost advantages of silicon chip fabrication
Key advantage: optical signals can carry vastly more data than electrical signals over the same distance, with less energy loss
Enables high-speed communication links inside and between data centers
All four asserted patents relate to silicon photonics technologies
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Section I: How Silicon Photonics Works — Key Components
Laser source: generates the light signal (often an external laser coupled onto the chip)
Optical waveguide: a tiny channel etched into the silicon chip that guides light, analogous to a wire guiding electricity
Modulator: encodes data onto the light signal by varying its properties (intensity, phase, polarization)
Photodetector: converts the incoming light signal back into an electrical signal at the receiver end
Grating coupler: a structure that couples light between an optical fiber and the on-chip waveguide
Multiplexer/demultiplexer: combines or separates multiple light signals of different wavelengths onto/from a single waveguide
Photonic Integrated Circuit (PIC): a chip that integrates multiple photonic components onto a single silicon substrate
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Section I: The Data Center Application
Modern hyperscale data centers contain hundreds of thousands of servers that must communicate at very high speeds
Optical transceivers are pluggable modules that convert data from electrical signals to optical signals (and back) for transmission over fiber-optic cables
Transceiver speed designations (400G, 800G, 1600G) refer to the data rate in gigabits per second
Both OWS and Lumicore sell transceiver modules into this market
Industry is rapidly scaling from 400G to 800G and 1600G, driven by AI and cloud computing workloads
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Section II: Optical Waveguides — The Foundation
An optical waveguide confines and guides light along a defined path on the chip
Made by creating a region of higher refractive index (the 'core') surrounded by lower refractive index material (the 'cladding')
In silicon photonics, the waveguide core is typically silicon (refractive index ~3.5) and the cladding is silicon dioxide (refractive index ~1.45)
Light is confined by total internal reflection — the same principle that keeps light inside an optical fiber
Waveguide dimensions are typically on the order of hundreds of nanometers, enabling dense integration on chip
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Section II: Wavelength Division Multiplexing (WDM) — The Concept
Different colors (wavelengths) of light can travel through the same waveguide simultaneously without interfering with each other
Each wavelength carries an independent data stream — like multiple radio stations broadcasting on different frequencies
Wavelength Division Multiplexing (WDM) combines multiple wavelengths onto one waveguide to increase total data capacity
A 'multiplexer' combines signals; a 'demultiplexer' separates them
Dense WDM (DWDM) uses many closely spaced wavelengths; Coarse WDM (CWDM) uses fewer, more widely spaced wavelengths
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Section II: What Is a 'Waveguide Multiplexer'?
A waveguide multiplexer is an optical device that combines multiple optical signals of different wavelengths onto a single waveguide
Multiple implementation architectures exist, including: arrayed waveguide gratings (AWGs), Echelle gratings, cascaded Mach-Zehnder interferometers, and ring-resonator-based multiplexers
All share the common function of combining (multiplexing) wavelength channels into a single waveguide
The specific architecture (e.g., AWG vs. ring resonator) is a design choice, not a definitional requirement
'Insertion loss' refers to the amount of optical power lost when a signal passes through the multiplexer — lower is better
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Section II: Arrayed Waveguide Grating (AWG) — One Type of Waveguide Multiplexer
An AWG uses an array of waveguides with carefully designed length differences to create constructive interference at specific wavelengths
Components: input waveguide → input slab coupler → arrayed waveguide array (with incremental path-length differences) → output slab coupler → output waveguides
Each output waveguide receives a different wavelength channel
AWGs are well-known in the art and are one common implementation of a waveguide multiplexer
But an AWG is not the only type of waveguide multiplexer
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Section II: Other Waveguide Multiplexer Architectures
Ring-resonator-based multiplexer: uses micro-ring resonators that each selectively couple a specific wavelength from a bus waveguide
Echelle grating multiplexer: uses a reflective diffraction grating etched into a slab waveguide to separate/combine wavelengths
Cascaded Mach-Zehnder interferometer (MZI) multiplexer: uses a series of interferometric stages to filter and combine wavelengths
Each architecture has different trade-offs in size, bandwidth, insertion loss, and manufacturing complexity
A person of ordinary skill in the art (POSITA) would understand 'waveguide multiplexer' to encompass all of these architectures
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Section III: Optical Transceivers — Overview
An optical transceiver is a device that both transmits and receives optical signals
Transmit side: electrical data in → modulated onto a laser's light → output to fiber
Receive side: light from fiber → detected by photodetector → converted back to electrical data
Pluggable form factors (e.g., QSFP-DD, OSFP) allow transceivers to be inserted into network switches
Key performance metrics: data rate, reach (distance), power consumption, and cost
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Section III: Coherent vs. Direct-Detect Transceivers
Direct detection: photodetector simply measures the intensity (brightness) of the incoming light — simpler but limited in performance
Coherent detection: the received signal is mixed with a local oscillator (reference laser) to extract both amplitude and phase information
Coherent detection enables higher spectral efficiency (more data per wavelength), longer reach, and advanced modulation formats
Coherent transceivers are essential for high-capacity data-center interconnects at 400G and above
The '193 Patent claims a coherent optical transceiver integrated on a silicon substrate
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Section III: 'Integrated on a Silicon Substrate' — What It Means
Integration on a silicon substrate means that optical and electronic components are fabricated on or within a silicon-based wafer using semiconductor fabrication processes
This includes both monolithic integration (all components on a single die) and hybrid/heterogeneous integration (combining different materials bonded to a silicon substrate)
Monolithic: everything fabricated in one process on one wafer (e.g., silicon waveguides, germanium photodetectors grown on silicon)
Hybrid/heterogeneous: separately fabricated components (e.g., III-V laser dies) bonded or attached to a silicon photonic chip
Both approaches are well-recognized in the field as 'integration on a silicon substrate'
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Section III: The Coherent Detection Module
A coherent detection module comprises: a local oscillator laser, an optical hybrid (90° or 2×4), balanced photodetectors, and signal processing electronics
The optical hybrid mixes the incoming signal with the local oscillator to extract in-phase (I) and quadrature (Q) signal components
Balanced photodetectors cancel common-mode noise, improving signal quality
Different implementations exist: discrete coherent receivers, integrated coherent receivers (ICRs), and fully monolithic coherent PICs
Function: recover both amplitude and phase of the optical signal to reconstruct the transmitted data
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Section IV: Thermal Management in Photonic Integrated Circuits — The Problem
Photonic components (lasers, modulators, multiplexers) are extremely sensitive to temperature changes
Temperature shifts cause changes in refractive index, which shifts the operating wavelength of waveguides and multiplexers
Even a 1°C change can cause a wavelength shift sufficient to degrade performance in a dense WDM system
High-power lasers and electronic driver circuits generate significant heat in a compact transceiver module
Effective thermal management is essential to maintain stable, reliable operation
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Section IV: 'Micro-Channel Heat Sink' — The Technology
A micro-channel heat sink is a heat-dissipating structure containing channels with a hydraulic diameter of less than 1 mm
Coolant (liquid or gas) flows through the micro-channels, absorbing and carrying away heat from the photonic circuit
Micro-channels can be etched directly into the silicon substrate beneath or adjacent to the photonic components
Smaller channels provide greater surface-area-to-volume ratio, improving heat transfer efficiency
The '562 Patent claims embedding these micro-channel heat sinks within or beneath the photonic integrated circuit
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Section IV: Micro-Channel Heat Sink — Design Variations
Channel geometries: rectangular, trapezoidal, circular, or irregular cross-sections
Cooling medium: liquid (water, dielectric fluids) or gas (air, nitrogen)
Flow configuration: single-pass, multi-pass, manifold-fed, or recirculating (closed-loop)
Channel dimensions: can range from a few micrometers to several hundred micrometers in hydraulic diameter
Integration methods: channels etched directly into the substrate, channels formed in a separate heat-sink layer bonded to the PIC, or channels created within interposer layers
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Section V: Grating Couplers — Coupling Light Between Fiber and Chip
A grating coupler is a periodic structure etched into a waveguide that diffracts light between an optical fiber (arriving from above/below) and the on-chip waveguide (propagating horizontally)
Grating couplers solve the size-mismatch problem: an optical fiber core (~9 µm) is much larger than a silicon waveguide (~0.5 µm)
The grating's periodicity, etch depth, and geometry determine which wavelengths and angles of light are coupled efficiently
Grating couplers are widely used in silicon photonics because they allow wafer-level testing and flexible fiber attachment
Limitation: standard grating couplers are polarization-sensitive — they efficiently couple only one polarization state of light
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Section V: Polarization of Light — A Brief Primer
Light is an electromagnetic wave; its electric field oscillates in a plane perpendicular to the direction of travel
Polarization describes the orientation of this oscillation: horizontal (TE), vertical (TM), or any angle in between
In an optical fiber, the polarization state is random and changes unpredictably due to fiber bending and environmental factors
Silicon waveguides handle TE and TM modes differently — they have different propagation speeds and losses
For reliable data transmission, a transceiver must handle both polarization states — this is 'polarization diversity'
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Section V: 'Polarization-Diverse Grating Coupler' — The Innovation
A polarization-diverse grating coupler is a grating coupler capable of coupling light of two orthogonal polarization states (TE and TM)
One approach: a two-dimensional (2D) grating that diffracts TE light into one on-chip waveguide and TM light into another, perpendicular waveguide
Another approach: a specially designed 1D grating with a polarization-splitting element
The result: regardless of the incoming polarization, essentially all of the light is captured and routed to the appropriate processing path on chip
This eliminates the ~3 dB polarization-dependent loss of a standard grating coupler
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Section V: The 'Two-Dimensional Sub-Wavelength Grating' Limitation
A sub-wavelength grating has a period smaller than the operating wavelength of light, preventing higher-order diffraction
In a 2D sub-wavelength grating, the pattern is periodic in two dimensions on the chip surface
Sub-wavelength features allow engineering of the grating's effective refractive index and coupling characteristics
This enables more uniform coupling efficiency across a wider bandwidth and for both polarizations
Claim 12 of the '015 Patent recites a 'two-dimensional sub-wavelength grating' element
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Section VI: Mapping Technology to the Asserted Patents — Summary Table
'847 Patent — Waveguide Multiplexing: Key term: 'waveguide multiplexer' (Section II)
'193 Patent — Coherent Transceivers: Key terms: 'integrated on a silicon substrate,' 'coherent detection module' (Section III)
'562 Patent — Thermal Management: Key term: 'micro-channel heat sink' (Section IV)
'015 Patent — Polarization-Diverse Grating Couplers: Key terms: 'polarization-diverse grating coupler,' 'two-dimensional sub-wavelength grating' (Section V)
All 14 disputed claim construction terms relate to these four technology areas
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Section VII: Person of Ordinary Skill in the Art (POSITA)
A person of ordinary skill in the art (POSITA) at the time of each patent's filing would have:
An M.S. or Ph.D. in electrical engineering, photonics, optical engineering, or a closely related field
At least 3 years of experience in silicon-photonic integrated circuit design, fabrication, or characterization
Familiarity with semiconductor fabrication processes, waveguide design, optical modulation and detection, thermal management of integrated circuits, and fiber-optic coupling techniques
This level of skill reflects the advanced but not inventive knowledge expected in this specialized field
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Section VIII: Summary and Key Takeaways
Silicon photonics enables high-speed optical communication using standard semiconductor manufacturing
A 'waveguide multiplexer' is any optical device combining multiple wavelengths onto a single waveguide — not limited to AWGs
'Integrated on a silicon substrate' encompasses fabrication on a silicon wafer, including both monolithic and heterogeneous approaches
A 'micro-channel heat sink' is a heat-dissipating structure with sub-millimeter channels — not limited to closed-loop liquid-cooling systems
A 'polarization-diverse grating coupler' is any grating coupler that couples both TE and TM polarization states — not limited to 2D gratings with a specific polarization-splitting element
The claim terms should be given their ordinary and customary meaning to a POSITA, informed by the intrinsic record
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Glossary of Technical Terms
AWG — Arrayed Waveguide Grating
CWDM — Coarse Wavelength Division Multiplexing
DWDM — Dense Wavelength Division Multiplexing
ICR — Integrated Coherent Receiver
MZI — Mach-Zehnder Interferometer
PIC — Photonic Integrated Circuit