Optical Fiber Bragg Grating Pressure Sensor Based on Dual-Frequency Optoelectronic Oscillator

A dual-frequency optoelectronic oscillator (OEO) for high sensitivity pressure sensing is proposed and experimentally demonstrated. The oscillation frequency of the OEO is determined by a dual-passband microwave photonic filter in the OEO loop, which is implemented using phase shifted fiber Bragg gratings (PSFBGs) written in side-hole fiber to perform phase-modulation to intensity-modulation conversion. When the PSFBGs are experiencing a pressure, the wavelength difference between the two notches of the PSFBGs is slightly changed, which leads to a large frequency change of the two oscillating frequencies. Since the beat frequency between the two microwave signals is linearly proportional to the pressure, the high sensitivity pressure measurement can be realized through monitoring the beat frequency. The proposed approach is experimentally evaluated. High sensitivity pressure sensing with a sensitivity of 418.8 MHz/MPa is experimentally demonstrated. In addition, the sensing is insensitive to the variations of the environmental temperature.