Simultaneous demodulation comparison of fiber-optic Fabry–Perot sensors connected in parallel and series

In this work, the spectra of two fiber-optic Fabry–Perot sensors in parallel and series connection were studied. The spectrum of the parallel structure is a simple superposition of the two sensors’ spectrum, and that of the series structure can be regarded as the interference occurring in two Fabry–Perot sensors successively. The sensors’ optical path difference can be obtained and separated by using the theoretical formula to fit the normalized spectrum of parallel or series structure, which showed that two or more Fabry–Perot sensors can be simultaneously demodulated by the spectrum fitting method.