Optical Coherence-Multiplexed Sensors Based on In-Fiber Michelson

We propose an optical low-coherent interrogation scheme for multiplexed sensors based on in-fiber Michelson interferometers. In the interferometer, a long period fiber grating (LPG) works as a wavelength-dependant coupler and the fiber core and cladding of a section of the fiber (with a highly-reflective mirror at the end) work as two arms of the interferometer. The optical path difference (OPD) induced in such an interferometer is proportional to the interval of the grating-center to the end-mirror of the fiber. By presetting these intervals with different values, the signals from the multiple sensors can be obtained and distinguished by an optical low-coherence reflectometry (OLCR). Through measuring environmental temperature, the good performance of our system is demonstrated. The system also has some potential applications in distributed sensing for chemical or biological parameters.