Low-Coherence Fiber Differential Interferometer With Adjustable Measurement Range

A low-coherence fiber differential interferometer with adjustable measurement range is presented in this letter. The interferometer is based on an all fiber Mach-Zehnder and Sagnac hybrid interferometer. Results show that the measurement range of the differential interferometer is related to the delay fiber length, which can be adjusted by an optical switch. The experimental results demonstrate that the phase demodulation resolution is $3.37\times 10^{-5}$ rad and the maximum measuring amplitude is 419 rad with a signal frequency of 1 kHz. This scheme can be used to measure many kinds of parameters, such as vibration and electrical current.