All-optical graphene-oxide humidity sensor based on a side-polished symmetrical twin-core fiber Michelson interferometer

A high-sensitive graphene-oxide (GO) humidity sensor based on a side-polished twin-core fiber (SPTCF) Michelson interferometer (MI) has been demonstrated. The MI was fabricated by splicing a section of TCF to a standard single mode fiber (SMF) and tapering the splicing point. The exposed polished core has a stronger evanescent field and enhances the interaction between light and external environment. The GO-SPTCFMI can operate in the wavelength-and intensity-modulated sensor. The super-high humidity sensitivities of similar to 2.72 nm/RH% in the RH range of 40-75% and similar to 3.76 dB/RH% in the RH range of 60-62.1% are obtained experimentally. The high-performance GO-SPTCFMI is a promising candidate for potential applications, such as gas sensing and biochemical detection.