An in-line fiber Mach-Zehnder interferometer (MZI) based on twin-hole fiber for humidity sensing was proposed and experimentally demonstrated. The twin-hole fiber was filled in black phosphorus (BP) by capillary absorption method, and then was sandwiched in between two single mode fibers (SMFs) to form intermodal interference. Utilizing the sensitivity of BP to ambient humidity, the MI could realize humidity measurement. Experiment results reveal that the interference intensity changes in the RH range of 20-80%RH, and the sensitivity was -0.028 dB/%RH. This sensor has great potential for application in chemical and biology fields.
An in-fiber Michelson interferometer based on core mismatching for liquid refractive index sensing is proposed and demonstrated. The sensor can be simply fabricated by fusion splicing a section of thinned core fiber (TCF) to a standard single mode fiber (SMF) without any reflection coating. The experimental results show that the sensor possesses RI sensitivity of -111.58 dB/RIU in the RI range of 1.333-1.380 RIU. The liquid temperature cross-sensitivity is experimentally analyzed and reveals that the measurement error of the liquid RI caused by temperature is -0.89×10-6 RIU/℃ in water temperature range of 25℃-80℃. The advantages of easy fabrication, high sensitivity, working on reflective intensity detection and compact size make the proposed sensor can offer promising applications in chemical, biomedical and petrochemical fields.