Intensity measurement of a temperature-insensitive strain sensor based on a highly birefringent photonic crystal fiber loop

An intensity measurement of a temperature-insensitive strain sensor is proposed based on a highly birefringent photonic crystal fiber loop mirror(HiBi-PCF-FLM). The strain sensor is realized by using a short length of highly birefringent photonic crystal fiber(PCF) as the sensing element inserted in a fiber loop mirror(FLM). Due to the ultralow thermal sensitivity of the PCF, the proposed strain sensor is inherently insensitive to temperature. When a DFB laser as a light source passes through the FLM, the output power is affected by the transmission spectral change of the FLM which is only caused by the strain applied on the PCF. Based on intensity measurement, an optical power meter is adequate to deduce the strain information and an expensive optical spectrum analyzer(OSA) is not needed. Experimental results show that the relationship between the applied stain and the output intensity is approximately quadratic polynomial for strains from 0 to 5770 μΕ when the DFB laser is at a wavelength of 1547 nm, and the fitting degree of the relationship curve is obtained highly as 0.9995.