Fiber loop ringdown strain sensor with photonic crystal fiber based Mach-Zehnder interferometer

Abstract

A highly sensitive strain sensor is demonstrated by inserting a photonic crystal fiber (PCF) based Mach-Zehnder interferometer (MZI) in a cavity ringdown fiber loop as the lossy sensing element. The MZI consists of a piece of PCF spliced to single-mode fibers, in which the PCF air holes are collapsed over a short region at two splicing points for coupling the core and cladding modes. By measuring the decay constants of the fiber ringdown loop, a high strain sensitivity of ~0.21 μs-1/mε and a minimum detectable strain of ~3.6 με were obtained.