High-sensitivity multipoint refractive index measurement system composed of multimode interference sensors and arrayed waveguide wavelength filters

A multipoint sensing measurement system with high sensitivity was developed by combining multimode interference (MMI) sensors and a wavelength selection configuration. MMI optical fibers and an arrayed waveguide (AWG) wavelength filter work as refractive index sensors and wavelength selector, respectively. They were operated with a fine calibration technique using dual AWG wavelength filters and defined wavelength light from a tunable laser source. By employing narrow-core single-mode fibers for the input and output ports of the MMI, the optical fiber improved the average sensitivity up to 820 dB/RIU under multipoint sensing conditions.