Refractive index and temperature sensor based on fiber ring laser with tapered seven core fiber structure in 2 μm band

A weakly-coupled taper-based seven core fiber (TSCF) structure sensor for refractive index (RI) and temperature measurement with a fiber ring cavity laser in 2 mu m band was proposed and demonstrated. The TSCF fiber structure acts as both the sensing head and the filter of the laser. Compared with the conventional broadband sensing system, the laser sensing system we proposed has a higher optical signal to noise ratio (OSNR) of similar to 40 dB and a narrower 3 dB bandwidth of similar to 0.05 nm. By exposing the TSCF segment to the increasing RI solutions, the output wavelength will have a redshift. A sensitivity of 549.599 nm/RIU was obtained with the RI of NaCl solution changing from 1.3325 to 1.3793. While for temperature measurement, a sensitivity of -4 pm/degrees C was achieved with the temperature ranging from 35 degrees C to 70 degrees C. Notably, the sensing system we proposed shows the merits of marrow 3 dB bandwidth, easy construction, high resolution, high signal-to-noise ratio, and easier to monitor.