Comparison of sensitivity and thermal response of chirped fiber Bragg gratings at various degrees of bending

Abstract

The development of optical fiber sensors based on Fiber Bragg Grating (FBG) has driven the need for a deeper understanding of sensor characteristics under mechanical deformation conditions. This study is motivated by the limited investigations specifically examining the simultaneous interaction between bending and thermal response in chirped FBG. This research aims to analyze the effect of bending degree on the sensitivity and thermal response of Chirped Fiber Bragg Grating (CFBG), to observe Bragg wavelength (λB) shifts and transmission power variations, and to determine the optimal bending configuration. Measurements were conducted using a dual laser source at wavelengths of 1310 nm and 1550 nm, with bending angle variations of 0°, 10°, 20°, 30°, and 40°, across a temperature range of 35°C to 49°C representing human physiological conditions. Results demonstrate that bending degree exerts a substantially more dominant influence on transmission power than temperature variation, with inter-angle power differences exceeding 12 dB. Bending angles of 20° and 30° consistently yielded the highest transmission power, with sensitivity values reaching 1555.72% and 1527.37% respectively at 1550 nm. The 1310 nm wavelength exhibited slightly higher sensitivity, whereas the 1550 nm demonstrated better thermal response stability. This research contributes to establishing optimal operating conditions for CFBG sensors in wearable health monitoring applications requiring high sensitivity and reliable thermal stability.