Optical fiber sensors based on photonics crystal fiber loop mirrors

We summarize various sensors based on photonic crystal fiber loop mirrors proposed by our research team, including strain sensors, temperature sensors and curvature sensors. Both of highly birefringent and lowly birefringent photonic crystal fibers (PCFs) have been inserted into fiber loop mirrors (FLMs) as the sensing elements. A temperature-insensitive strain sensor with highly birefringent PCF based FLM has been realized and it has a strain sensitivity of 0.23 pm/µε in the range of 0–30 mε. For a low-cost, a demodulation is proposed by using a distributed-feedback (DFB) laser as the light source and an optical power meter instead of an expensive OSA. Strain and curvature sensors based on FLMs are also demonstrated by using a lowly birefringent PCF, which has a strain sensitivity of 0.457 pm/µε and a curvature sensitivity of 0.337 nm/ m⁻¹, respectively. Further, a novel and compact temperature sensor based on a FLM combined with an alcohol-filled highly birefringent PCF is proposed and experimentally demonstrated and it has a high sensitivity as high as 6.6 nm/°C.