title: Highly sensitive liquid-level sensor based on dual-wavelength double-ring fiber laser assisted by beat frequency interrogation.
abstract: A highly sensitive liquid-level sensor based on dual-wavelength single-longitudinal-mode fiber laser is proposed and demonstrated. The laser is formed by exploiting two parallel arranged phase-shift fiber Bragg gratings (ps-FBGs), acting as ultra-narrow bandwidth filters, into a double-ring resonators. By beating the dual-wavelength lasing output, a stable microwave signal with frequency stability better than 5 MHz is obtained. The generated beat frequency varies with the change of dual-wavelength spacing. Based on this characteristic, with one ps-FBG serving as the sensing element and the other one acting as the reference element, a highly sensitive liquid level sensor is realized by monitoring the beat frequency shift of the laser. The sensor head is directly bonded to a float which can transfer buoyancy into axial strain on the fiber without introducing other elastic elements. The experimental results show that an ultra-high liquid-level sensitivity of 2.12 × 10(7) MHz/m within the measurement range of 1.5 mm is achieved. The sensor presents multiple merits including ultra-high sensitivity, thermal insensitive, good reliability and stability.
authors.affiliation: Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Dai
authors.forename: Qizhen
authors.initials: Q
authors.lastname: Sun
authors.forename: Sisi
authors.initials: S
authors.lastname: Tan
authors.forename: Jianghai
authors.initials: J
authors.lastname: Wo
authors.forename: Jiejun
authors.initials: J
authors.lastname: Zhang
authors.forename: Deming
authors.initials: D
authors.lastname: Liu
mesh_terms: D001671:Biochemistry / Q000295:instrumentation / Q000379:methods*; D004548:Elasticity; D004867:Equipment Design; D005336:Fiber Optic Technology / Q000295:instrumentation / Q000379:methods*; D007834:Lasers; D008872:Microwaves; D008962:Models, Theoretical; D055100:Optical Fibers; D012031:Refractometry / Q000295:instrumentation / Q000379:methods; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation