Optical Module Package Design with Folded Waveguides
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Solution Overview
Problem
Existing optical modules face challenges in achieving a smaller size while maintaining mechanical reliability and optical characteristics due to thermal stress caused by differing thermal expansion coefficients between materials, leading to increased fiber bending loss and reduced reliability.
Innovation Solution
The optical module incorporates a package design with folded waveguides in planar lightwave circuits (PLCs) that connect optical fibers directly from the same surface, eliminating the need for extra fiber length and reducing thermal stress by distributing connection points, thus allowing for a more compact size without compromising reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical fibers are fixed at two points (connecting part and pipe section) in conventional packages, then mechanical stability is achieved, but thermal stress causes position variation and reduced reliability
Solution Approach 1:
The patent changes the thermal expansion parameter by replacing the metal package with a silica glass package that has a thermal expansion coefficient matching the optical fibers and PLC. This parameter change eliminates thermal stress caused by differential expansion between materials, thereby improving mechanical reliability while fixing fibers at two points
Solution Approach 2:
The patent employs composite material selection where the package, PLC, and fiber connecting parts are all made from silica glass-based materials. This creates a homogeneous material system with matched thermal expansion coefficients, eliminating thermal stress and improving reliability without compromising mechanical stability
2Reliability
If extra fiber length is provided for buckling to absorb position variation, then thermal stress is compensated, but package size increases
Solution Approach 1:
By changing the thermal expansion parameter of the package material to match the fibers and PLC (using silica glass throughout), the patent eliminates the need for fiber buckling compensation. This parameter change allows the package size to be reduced while maintaining optical fiber reliability
Solution Approach 2:
The patent extracts and eliminates the unnecessary extra fiber length that was previously required for thermal compensation. By removing this redundant fiber length, the package size is reduced while reliability is maintained through material parameter matching
3Reliability
If metal package is used for reliability and gas barrier, then protection is achieved, but thermal expansion mismatch with glass and semiconductor materials causes thermal stress
Solution Approach 1:
The patent applies composite material principle by selecting silica glass as the package material that is compatible with both the glass PLC and optical fibers. This creates a homogeneous material system where thermal expansion coefficients are matched, eliminating thermal stress while maintaining protection and gas barrier properties
Solution Approach 2:
The patent achieves homogeneity by making the package, PLC, and fiber connecting parts all from silica glass-based materials. This homogeneous material composition ensures matched thermal expansion characteristics, eliminating thermal stress while preserving the protective functions
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
This design achieves a reduced package size, improved workability, and enhanced mechanical reliability by minimizing thermal stress and fiber bending loss, while maintaining optical waveguide characteristics similar to conventional modules.
Implementation Method 1
a folded waveguide for connecting a light waveguide formed in the optical functional element to optical fibers
Implementation Method 2
optical functional element with an electro-optic effect
Data Source
AI summary
Even in the case of an optical module including a multi-chip integrated device, an optical module having a smaller size in consideration of the connection to optical fibers. An optical module having a package containing a multi-chip integrated device integrated with an optical functional element having both ends connected to planar lightwave circuits (PLCs) is provided. Each of the PLCs includes a folded waveguide for connecting a light waveguide formed in the optical functional element to optical fibers. The optical module comprises a connecting part connected to each of the PLCs for connecting the optical functional element to the optical fibers in the same face. The optical fibers are taken out from opposed surfaces of the package.