Sagnac Ring Humidity Sensor With a Melting Cone Based on Graphene Properties

This study proposes a new type of fused cone Sagnac ring humidity sensor based on graphene properties. First, the single-mode optical fiber (SMF) is fused with the photonic crystal fiber (PCF) to form SMF-PCF-SMF interference. Then, the SMFs at both ends of the PCF are folded in half to form a ring. The ring is placed on the fiber pulling cone translation platform for pulling cone coupling. A Sagnac interferometer that connects the PCF is formed by applying the birefringence effect of melting cone coupling. The prepared interferometer is placed on a special optical platform, and graphene is coated on the fused cone area and the PCF. The excellent properties of graphene are utilized to measure humidity. Experimental results show that sensitivity to humidity is within the range of 36.0% relative humidity (RH)-75.3% RH, reaching 340.13pm/% RH. The sensor proposed in this study exhibits the characteristics of a simple structure, easy manufacturing, and low cost. It can be used as reference for the design and development of new sensors.