A cobalt carbonate hydroxide hydrate-based optics fiber sensor for humidity and temperature detection

A highly sensitive sensor based on a Mach-Zehnder interferometer (MZI) with “SMF-MMF-TCF-MMF-SMF” structure is proposed to measure temperature and humidity. To improve the sensitivity of this sensor, cobalt carbonate hydroxide hydrate nanosheet arrays were grown on the surface of TCF with a facile hydrothermal method. The sensor exhibits high sensitivity measurement of multiple parameters including 1.29 nm/°C in the temperature range of 24 °C–60 °C and 0.56 nm/%RH in the humidity range of 65 %–89 %. Through systematic experiments, results show that the fabricated MZI structure can measure one quantity only if other one is known. Based on this, a fiber Bragg grating could be used to eliminate the cross-sensitivity between temperature and humidity by a wavelength conversion method. In addition, this sensor also exhibits many other merits such as simple structure, compact volume, robust structure, good repeatability and stability. This all-fiber sensor is anticipated to be applied in various devices which could measure temperature and humidity in agriculture, chemical industry, semiconductor manufacturing, electricity and other fields.