Multi-parameter sensor based on dumbbell stepped fiber core structure with the composite interferometric effect

Based on the composite interference structure, fiber optic multiparameter sensors can be constructed, however, this type of sensor has two bottlenecks, which are difficult to fabricate and the parameters interfere with each other. This paper proposes to simultaneously measure force, temperature, and salinity using a compact sensor with minimal signal crosstalk. The sensor structure consists of three cascaded Mach-Zehnder interferometers (MZI). The use of different diameter fiber cores fused together creates a dumbbell Stepped taper-like structure, which ensures that more higher order modes are excited while maintaining the mechanical integrity of the sensor. By creating detecting regions of various sizes, signal interference between parameters is reduced. Theoretical and experimental findings demonstrate that sensors with the dumbbell structure provide a good foundation for three-parameter sensing. and its force, temperature, and salinity sensitivity can reach −2593 dB/N, 53 pm/°C and −145.4nm/RIU. The two bottlenecks mentioned above are effectively resolved by the proposed dumbbell stepped sensor, which may also be applied to multi-parameter measurements for structural health monitoring.