Assessment of a Plastic Optic Fiber Sensor for the Measurement of Static and Dynamic Strains

Abstract

Optical sensor offers remarkable advantage compared with traditional sensor, such as electromagnetic immunity, small size, and light weight. A low-cost intensity-based plastic optical fibre (POF) sensor is presented in this paper to measure both static and dynamic strain on a cantilevered beam. The principle of measurement is that the intensity of transmitted light changes as strain changes. By detecting the transmitted light intensity, the change of strain can be measured. First, the principle and design of the sensor are presented. Three POF sensors made using three types of housings (silicon rubber tube, rubber tube and PTFE tube) are evaluated to compare their performance, such as sensitivity, resolution and linearity. A comparison of the strain response of these sensors in static test shows that the soft material (silicon rubber and rubber tube) offers better sensitivity than that of hard material (PTFE tube). However, in dynamic test, PFTE tube gives faster response time compared with rubber tube which is not suitable for high speed test (1k Hz). Both static and dynamic test results have shown that all sensors offer excellent agreement with electrical strain gauge readings and the sensitivity of POF sensor can be up to 20 μ strain. Strain transfer function is also conducted to examine the ability of optical sensors in detection of vibration modes of a cantilevered beam. A PCB piezoelectric accelerometer sensor is attached to the beam as well to measure the acceleration transfer function of the beam, which is used as a reference signal. The results also showed the possibility that POF sensors can be used for structural health monitoring.