Optical Module Flexible Printed Circuit Crosstalk Reduction
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Solution Overview
Problem
Conventional optical modules face issues with high wiring density leading to crosstalk and deteriorated bending properties due to the close arrangement of radio-frequency and bias lines, which complicates signal isolation and mounting on circuit boards.
Innovation Solution
The optical module incorporates a flexible printed circuit with dielectric layers, featuring ground conductor patterns and wiring patterns that face each other through these layers, allowing for reduced wiring density without compromising bending properties, ensuring effective line isolation and reducing crosstalk by positioning at least one ground conductor between the wiring patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the wiring density of the flexible printed circuit is increased to accommodate multiple channels, then the electrical connection capability is improved, but the radio-frequency and bias lines cross each other causing crosstalk and oscillation
Solution Approach 1:
The patent transitions from planar wiring arrangement to a three-dimensional stacked configuration where RF lines and bias lines are arranged in different layers separated by dielectric substrates. This vertical stacking in multiple dimensions allows both signal types to coexist without crossing, eliminating crosstalk while maintaining high wiring density.
Solution Approach 2:
The flexible printed circuit is segmented into multiple independent wiring layers, each dedicated to specific signal types (RF or bias). This segmentation isolates the signal paths physically, preventing interference between adjacent channels while allowing high-density connectivity.
2Reliability
If a multilayer structure is used to reduce wiring density, then the isolation between lines is improved, but the bending property of the flexible printed circuit is deteriorated
Solution Approach 1:
The patent employs thin flexible printed circuit boards with carefully controlled layer thicknesses that maintain flexibility while providing adequate isolation between wiring layers. The use of flexible substrates and thin dielectric layers ensures the circuit can be bent and mounted without compromising structural integrity or signal isolation.
Solution Approach 2:
The patent optimizes parameters such as dielectric layer thickness, wiring layer configuration, and material properties to achieve the minimum necessary isolation distance while maintaining flexibility. By adjusting these parameters, the design achieves line isolation equivalent to thicker multilayer structures without sacrificing bending properties.
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 configuration effectively reduces wiring density and maintains the flexibility of the printed circuit, ensuring reliable signal isolation and improved mounting properties by suppressing electromagnetic interference and crosstalk.
Implementation Method 1
The flexible printed circuit has an end of one surface stuck onto an entire surface of the feedthrough by an anisotropically conductive adhesive. The flexible printed circuit has connection pads disposed at positions that face the electric terminals of the feedthrough. Here, the anisotropically conductive adhesive is thermally cured while being crimped under pressure, to thereby exhibit conductivity only between the surfaces facing each other.
Implementation Method 2
a flexible printed circuit fixed to the feedthrough, in which the flexible printed circuit includes: dielectric layers; a first pattern facing portion including a first ground conductor pattern and a first wiring pattern electrically connected to the electric terminal, which are facing each other through the dielectric layer
Data Source
AI summary
Provided is an optical module in which wiring density may be reduced to ensure isolation between lines to reduce crosstalk. A flexible printed circuit includes: dielectric layers; a first pattern facing portion including a first ground conductor pattern and a first wiring pattern electrically connected to an electric terminal, which are facing each other through the dielectric layer; and a second pattern facing portion including a second ground conductor pattern and a second wiring pattern electrically connected to the electric terminal, which are facing each other through the dielectric layer, the second pattern facing portion facing the first pattern facing portion, in which when the dielectric layer is bent along a portion between the first pattern facing portion and the second pattern facing portion, at least one of the first ground conductor pattern and the second ground conductor pattern is located between the first wiring pattern and the second wiring pattern.