Fiber-tip-integrated High-sensitivity Refractive Index and High-precision Liquid Level Sensor Based on Surface Plasmon Resonance

A refractive index (RI) and liquid level sensing scheme based on a multimode-no-core fiber tip with high sensitivity and precision is proposed and experimentally demonstrated by fusing a tapered no-core fiber (NCF) with a segment of multimode fiber.A gold film is plated on the side surface of the uniform waist region of the tapered NCF to stimulate surface plasmon resonance.The as-fabricated sensor achieves RI sensitivities of 16500 and 24000 nm/RIU (refractive index unit) in the RI ranges of 1.34 to 1.38 and 1.39 to 1.41, respectively.High-precision liquid level sensing with a range from 0.1 to 2.0 mm is obtained simultaneously.The designed sensing structure in this work offers simplicity and ease of implementation, which makes it a promising option for high-sensitivity and high-precision sensing applications.