Room-temperature operated fast reversible ammonia sensor based on hybrid optical fiber structure with temperature compensated function

An optical fiber ammonia (NH3) sensor based on multi-mode interference (MF) and anti-resonance (AR) principle is proposed, which can detect the NH3 and increase the function of temperature measurement to avoid the influence of ambient temperature. The sensor is made of single-mode fiber (SMF) - hollow core fiber (HCF) - SMF - coreless fiber (NCF) -SMF welding, wherein NCF deposited graphene oxide gas response coating by dip-coating method. HCF and NCF can excite AR valley and MF valley simultaneously in the same spectrum. Experimental results show that for NH3 gas sensing, MF valley exhibits a NH3 sensitivity of 3.28 pm/ppm with a response time of 60 s and a recovery time of 30 s, while AR valley is not sensitive. For temperature sensing, MF valley and AR valley are sensitive to temperatures of -12.63 pm/℃ and 15.57 pm/℃, respectively. The simultaneous detection of NH3 and temperature can be realized through spectral demodulation. The gas sensor offers several advantages, including straightforward preparation, cost-effectiveness, and low operating temperature. Most importantly, it solves the problem of temperature interference that is often ignored in fiber optic gas sensors, and the hybrid fiber structure is suitable for many multi-parameter measurement occasions and has important practical application significance.