Long-Period Fiber Grating Sensor Based on a Conductive Polymer Functional Layer

Ching-Yu Hsu,Jing-Lun Chen,Chia-Chin Chiang,Hsin-Yi Wen,Tao-Hsing Chen,Jian-Jie Weng,Ya-Hui Chen

doi:10.3390/polym12092023

Ching-Yu Hsu, Jing-Lun Chen + Show 5 more

Open Access

https://doi.org/10.3390/polym12092023

Copy DOI

Abstract

A temperature sensor was fabricated with a functional conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coating on a long-period fiber grating (LPFG). The LPFG was fabricated by laser-assisted wet-chemical etching for controlling the grating depth of the LPFG after the treated surface of an optical fiber was inscribed by laser light. The functional conductive polymer acts as a temperature sustained sensing layer and enhances the grating depth of the LPFG sensor as a strain buffer at various temperatures. The sensor was subjected to three cycles of temperature measurement to investigate the sensor’s wavelength shift and energy loss when exposed to temperatures between 30 and 100 °C. Results showed that the sensor’s average wavelength sensitivity and its linearity were 0.052 nm/°C and 99%, respectively; average transmission sensitivity and linearity were 0.048 (dB/°C) and 95%, respectively.

Highlights

There has been considerable interest in fiber grating refractive index (RI) sensors because of their high sensitivity, efficiency, and light weight
laser-assisted-etching LPFG (LLPFG) sensor was subjected to temperatures ranging from 30 to 100 ◦ C to analyze its sensitivity
Our study proposed a PEDOT:PSS-coated LLPFG sensor with a diameter of 65 μm and a period of 620 μm and subjected it to three temperature test cycles with the aim of investigating the sensor’s wavelength shifts and transmission losses when exposed to temperatures between 30 and 100 °C

Summary

Introduction

There has been considerable interest in fiber grating refractive index (RI) sensors because of their high sensitivity, efficiency, and light weight. Close attention has been paid to long-period fiber gratings (LPFGs), to the way in which light at the resonant wavelength of an LPFG is coupled from the guided to the cladding modes, which causes energy loss depending on the difference between the RI of the guided and cladding modes. For this reason, the previous study proposes a laser-assisted-etching LPFG (LLPFG) sensor fabricated using an excimer laser and metal photomasks, examines the effects of temperature on wavelength drift and transmission loss, and explores the use of LLPFG sensors for temperature sensing [1,2]. In addition to the fabrication of a long-period grating structure through reactive ion etching, that study examined the relationship between the tapered optical fiber’s

Methods

Results

Conclusion