Optical Cable Resin Thermal Expansion Matching
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Solution Overview
Problem
Optical communication cables with plastic optical fibers (POFs) are prone to cracking under high-temperature and high-humidity conditions due to thermal expansion of adhesives, which applies excessive stress to the POFs.
Innovation Solution
The optical communication cable design includes a POF with a covering layer, a connector, and a resin that satisfies a specific coefficient of linear expansion ratio between the resin and the POF, ensuring the resin's thermal expansion does not excessively stress the POF, thereby preventing cracking. The resin is strategically placed to contact the POF and housing components, with a coefficient of linear expansion within a defined range (35 to 70 ppm/°C) to mitigate thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive is used to fix the optical cord end portion to the housing, then the connection is maintained, but thermal expansion of the adhesive under high temperature and humidity applies excessive stress to the POF causing cracking
Solution Approach 1:
The patent changes the material parameter (coefficient of linear expansion) of the resin from conventional high-expansion materials to a specific resin with a coefficient of linear expansion of 35 to 70 ppm/°C, which matches the POF's expansion characteristics. This parameter change ensures that the resin and POF expand and contract at similar rates under thermal stress, preventing excessive stress concentration on the POF while maintaining reliable connection.
2Strength
If the optical cord end portion is fully covered with covering layer, then protection is provided, but the resin cannot contact the POF directly to control thermal expansion
Solution Approach 1:
The patent divides the optical cord into two distinct regions: a first end region where the covering layer is not formed and the POF is exposed for direct resin contact, and a second end region where the covering layer is formed for protection. This segmentation allows the resin to directly contact the POF in the first region to control thermal expansion, while the second region maintains protective coverage, thus resolving the contradiction between protection and thermal management.
3Weight of stationary object
If reduction in weight and thickness of opto-electric compound transmission modules is pursued, then miniaturization is achieved, but the risk of POF cracking under thermal stress increases
Solution Approach 1:
The patent addresses the reliability issue in miniaturized modules by changing the material parameter of the resin to have a coefficient of linear expansion of 35 to 70 ppm/°C, which closely matches the POF's expansion coefficient. This ensures that even in compact designs where thermal stress concentration may be higher, the resin and POF expand and contract together, preventing cracking while allowing weight and thickness reduction.
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 effectively suppresses the occurrence of cracking in POFs during high-temperature and high-humidity conditions, ensuring the optical communication cable's durability and reliability.
Implementation Method 1
when exposed to high temperature and/or high humidity, an adhesive that fixes an end portion of an optical cord, a housing (in other words, a case), and the like is thermally expanded to apply stress to a POF of the optical cord
Data Source
AI summary
The optical communication cable includes an optical cord, a connector, a first housing, a second housing, and a resin for fixing the optical cord. An end portion of the optical cord for connection to the connector has a first end region and a second end region. A tip portion of the plastic optical fibers in the first end region is connected to the connector. The resin is disposed so as to be in contact with the end portion of the optical cord and the second housing. Expression is satisfied:t1≤t2+5(1)where t1 is the coefficient of linear expansion of the resin and t2 is the coefficient of linear expansion of the plastic optical fibers.