Optical Interposer for Multi-Chip Module Coupling
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Solution Overview
Problem
Existing multi-chip modules face challenges in achieving high-fidelity signaling across a multi-chip geometry due to high insertion losses in optical couplers, which are attributed to alignment errors, light clipping, backscattering, and mode mismatch, leading to increased performance and cost requirements for other components.
Innovation Solution
A multi-chip module design that incorporates an optical interposer with an optical channel surrounded by an interposer substrate to guide optical signals between optical couplers, reducing spatial expansion and preserving the optical mode, thereby minimizing optical losses and facilitating low-loss coupling and broadband transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If existing optical couplers (mirror-reflecting, diffraction-grating, butt-coupled, lens couplers) are used to couple optical signals between substrates, then optical coupling between chips is achieved, but insertion losses are high (2.8-4.5 dB per coupler hop) due to alignment errors, light clipping, back scattering, and mode mismatch
Solution Approach 1:
The patent introduces an optical interposer as an intermediary component between the first and second substrates. This interposer includes an optical channel that receives optical signals from the first substrate's optical coupler and transmits them to the second substrate's optical coupler. The interposer acts as a mediator that reduces spatial expansion of the optical signal, thereby reducing insertion losses and improving signal fidelity compared to direct coupling approaches.
Solution Approach 2:
The patent transitions from planar (2D) optical coupling to three-dimensional (3D) vertical stacking architecture. By positioning substrates in vertical layers and using an optical interposer to bridge them, the system achieves optical coupling across multiple dimensions. This 3D architecture enables wavelength-division multiplexed optical links that route signals in orthogonal directions, reducing spatial expansion and minimizing losses.
2Ease of manufacture
If high insertion losses are accepted in optical couplers, then simpler coupling mechanisms can be used, but the optical link budget is severely impacted and performance requirements of other components must be significantly increased
Solution Approach 1:
The optical interposer serves as a mediator that enables relatively simple coupling mechanisms while achieving low insertion losses. Instead of requiring complex alignment and coupling structures, the interposer provides a controlled optical path that reduces spatial expansion, allowing simpler couplers to achieve better performance.
Solution Approach 2:
The patent changes key parameters of the optical transmission path by introducing the optical interposer with specific optical channel characteristics. These parameter changes include reduced spatial expansion, preserved optical modes, and minimized back scattering, which collectively reduce insertion losses without requiring complex coupling mechanisms.
3Adaptability or versatility
If multiple optical coupler hops are used in a multi-chip geometry, then connectivity between chips is achieved, but cumulative losses increase severely impacting the optical link budget
Solution Approach 1:
The patent implements 3D vertical chip stacking with optical interposers that enable connectivity in the vertical dimension. This allows multiple chips to be interconnected through wavelength-division multiplexed optical links that route signals in orthogonal directions, achieving high connectivity while minimizing the number of coupler hops and cumulative losses through efficient spatial routing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves reduced optical insertion losses of less than 1.5 dB per optical-proximity-coupler hop, enhancing the performance of multi-chip modules in applications like high-performance computing by maintaining high-fidelity signaling and reducing the need for costly component upgrades.
Implementation Method 1
an optical interposer, positioned between the first surface and the second surface, to guide the optical signal between the first optical coupler and the second optical coupler
Implementation Method 2
the optical channel transports the optical signal within the optical interposer using total internal reflection
Implementation Method 3
optical couplers, such as optical proximity couplers (OP×Cs), couple the distributed processors to optical routing layers
Implementation Method 4
a first optical coupler to couple an optical signal between a plane of the first optical waveguide and a direction out of the plane of the first optical waveguide
Data Source
AI summary
In an MCM, an optical signal is conveyed by an optical waveguide disposed on a surface of a first substrate to a first optical coupler. This first optical coupler redirects the optical signal out of the plane of the optical waveguide. Then, an optical interposer guides the optical signal between the first optical coupler and a second optical coupler on a surface of a second substrate, thereby reducing spatial expansion of the optical signal between the optical couplers. Moreover, the second optical coupler redirects the optical signal into a plane of an optical waveguide disposed on a surface of the second substrate, which then conveys the optical signal.