Mechanical Properties of a Polyimide Coat for Fiber-optic Sensors

Abstract

Long-term durability is essential for those fiber-optic sensors that detect changes of the optical properties due to the mechanical deformation of the sensing fiber. The lifetime of a sensing fiber determines the durability of the sensor, and the debonding of the polyimide coat to the fiber affects the fiber lifetime. We report in this paper the debonding property of a water-resistant polyimide coat under high temperature and humidity. We found that the adhesion property of the polyimide film improved when an adhesion promoter was added. We also found the optical fiber showed an excellent adhesion property after being exposed to 85°C and 85% relative humidity for 1000 h . This protective coating of a water-resistant polyimide makes it possible to fabricate more reliable optical fiber sensors.