Multipoint Refractometer Based on Combined Correlation and Frequency Multiplexing

We demonstrate a new simple multi-point refractometer using Fresnel reflection at the fiber tip with closely spaced interferometer for intensity reference. A combined technique for simultaneous interrogation and multiplexing of identical sensor heads was developed to obtain multipoint operation with a standard continuous-wave DFB diode laser as light source. The technique is based on the combination of coherent optical frequency division reflectometry and coherent correlation optical time-domain reflectometer. Feasibility of accurate operation for multipoint refractive index measurements is demonstrated in proof-of-concept experiments. The proposed refractometer could be useful for sensing in chemical and biological applications.