Study on the Sensitivity of Bare Fiber Bragg Grating for Ultrasonic Frequencies Response under Various Temperature

This work presents a study on the sensitivity of bare fiber Bragg grating (FBG) to detect ultrasonic frequencies under various temperature. Two infrared (IR) laser with excitation wavelength, λ=1310nm and λ=1550nm were employed. Various types of FBG with operating wavelength of 1546nm, 1550nm and 1554nm were used to identify the optimum design of sensor in detecting range of ultrasonic frequencies between 5kHz until 30kHz under various surrounding temperature from 20°C until 30°C. The principle of FBG vibration detection lies in the fact that spectral shift would occur due to the acoustic-induced variations in the medium. In this study, the ultrasonic signal had been investigated by monitoring the amplitude of optical output power. At 30°C, the bare FBG with operating wavelength of 1554nm using 1310nm light source exhibits the optimum performance in detecting ultrasonic vibration frequency, in which its sensitivity was obtained as P=0.10dBm. We believe that the sensitivity of the proposed sensor can be enhanced by introduce nanomaterials onto the FBG or by altering the physical structure of FBG. © Published under licence by IOP Publishing Ltd.