High-birefringence fiber loop mirror sensor using a WDM fused fiber coupler

Abstract

An intensity-based highly birefringent (Hi-Bi) fiber loop mirror (FLM) sensor is proposed which uses a wavelength-division multiplexing (WDM) fiber coupler. The effect of integrating the WDM coupler in a FLM configuration is first studied. A section of Hi-Bi (bow-tie) fiber of length 0.26 m is then placed in the fiber loop, making the spectral response of the device simultaneously dependent on the Hi-Bi fiber section and WDM coupler characteristics. When strain is applied to the sensing head, the spectral signal is modulated in amplitude, in contrast with the conventional Hi-Bi FLM sensors in which there are wavelength shifts. The sensor was characterized in strain and a sensitivity of (-2.2±0.4)×10(-3) με(-1) for a range of 300 με was attained. The self-referenced character of the sensor is noted.

Wavelength interrogation of fiber Bragg grating sensors based on crossed optical Gaussian filters

“…Other proposals involve interferometric techniques, where the wavelength-to-intensity conversion occurs immediately in either a coherent [8] or an incoherent interference [9]. It is similarly necessary for these cases that the Bragg wavelength should shift in the linear range of the interferometric response, the whole of which typically follows a sinusoidal trend [8][9][10].…”

Semi-reciprocal polarization maintaining fibre coupler with distinctive transmission characteristics

“…Optical couplers are also important elements of optical sensor systems, such as optical gyroscopes, optical hydrophones, and optical current sensors, etc. 3 4 5 6 . To date, several types of optical couplers with different materials or different transmission characteristics 7 8 9 , such as waveguide couplers 10 , fused-taper single mode fibre couplers 11 , fused-taper polarization maintaining fibre (PMF) couplers, and photonic crystal fibre couplers have been reported 12 13 14 15 16 17 18 .…”