Strain Sensor Based on Fiber Ring Cavity Laser With Photonic Crystal Fiber In-Line Mach–Zehnder Interferometer

We experimentally demonstrated a strain sensor based on fiber ring cavity laser with a photonic crystal fiber (PCF) in-line Mach-Zehnder interferometer (MZI) structure, which is used as an optical band-pass filter and acts as the strain sensing component. The fiber ring cavity laser plays the role of enhancing the visibility of the resonant spectrum and narrowing the corresponding 3-dB bandwidth, thus improving the comprehensive sensing performance. The induced axial strain on the structure is measured by monitoring the central wavelengths of the laser output. A high strain sensing sensitivity of 2.1 pm/με is successfully achieved in the linear strain range of 0-2100 με. A parameter Q value describing the overall sensing performance is introduced by including the strain sensing sensitivity, sensing sensitivity relative to 3-dB bandwidth of the resonant spectrum and the corresponding visibility. Comparing with the reported strain measurements based on a PCF in-line MZI structure, the experimental results based on fiber ring cavity laser sensor present more than nine times larger Q value.