Optical Transceiver FPC Layout for High-Frequency DSP Coupling
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Solution Overview
Problem
Existing optical transceivers face challenges in achieving ultra-high speed operation due to high-frequency signal loss and inefficient heat dissipation, particularly in co-package structures where the digital signal processor (DSP) and optical modules are closely mounted, leading to issues with thermal management and impedance mismatching.
Innovation Solution
The optical transceiver design incorporates a flexible printed circuit (FPC) that connects the DSP and optical modules using both surfaces of the FPC, aligning heat dissipation directions, and minimizing high-frequency signal path length through the use of a multilayer wiring circuit board and optimized PAD configurations to reduce impedance mismatching and heat sneaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a co-package structure is used to mount DSP and optical modules close together, then high-frequency signal loss is reduced, but thermal management becomes difficult due to heat generation from DSP
Solution Approach 1:
The patent divides the package into functionally independent regions: a first region for the optical module and a second region for the DSP. This spatial segmentation allows each component to have optimized thermal and electrical characteristics while maintaining close proximity for low-loss signal transmission.
Solution Approach 2:
The patent introduces a flexible wiring board as an intermediary connection medium between the optical module and DSP. This FPC serves as both an electrical connection path for high-frequency signals and a thermal isolation barrier, mediating between the conflicting requirements of signal integrity and thermal management.
2Ease of manufacture
If surface mount technology is used for optical module mounting, then ease of mounting is improved, but high-frequency transmission characteristics deteriorate due to VIA structure and impedance mismatching
Solution Approach 1:
The patent replaces the traditional rigid PCB VIA connection mechanism with a flexible wiring board connection system. This substitution eliminates the need for VIAs in the high-frequency signal path, thereby maintaining impedance continuity and improving high-frequency transmission characteristics while retaining ease of mounting through flexible board flexibility.
3Temperature
If DSP and optical module are mounted at separate locations on PCB, then thermal management is easier, but propagation loss increases limiting speed improvement
Solution Approach 1:
The patent merges the optical module and DSP into a single integrated package, combining functions that were previously separated on the PCB. This merging reduces the physical distance for signal transmission, minimizing propagation loss while the internal package design maintains adequate thermal management through regional separation and flexible board isolation.
Data Source
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AI summary
An optical transceiver is disclosed that implements smooth high frequency connection between a DSP and an optical module. The optical module may include an optical receiver module and an optical modulator module. The optical transceiver may include a single optical module in which functions of both the optical receiver and the optical modulator are integrated. The high frequency connection is implemented by a flexible circuit board (FPC), and the FPC electrically connects between a PAD on the upper surface of a DSP circuit board and a PAD of a package of the optical module. A connection PAD on one surface of the FPC is connected to the DSP circuit board side, and a connection PAD on the other surface is connected to the optical module side. A DSP chip may be mounted on the DSP circuit board, and the entire DSP may be covered with a lid except for a region of the DSP circuit board connected to the FPC.