Highly sensitive salinity and temperature measurement based on tapered-SHF MZI fiber laser structure

Abstract

A novel Mach-Zehnder interferometer (MZI) based on tapered-side-hole-fiber (SHF) fiber laser structure, which has obvious advantages in salinity and temperature measurement sensitivity, is analysed both theoretically and experimentally. The tapered-SHF structure is used as a sensing element and an optical filter, which is connected to the erbium-doped fiber (EDF) to form a fiber ring laser (FRL). Based on the linear correspondence between the output spectra of the FRL and the salinities, the salinity around the sensing area is measured by the MZI. The FRL has the unique advantages of high resolution, narrow line width, high optical signal-to-noise ratio (OSNR), and high stability. Compared with the transmission spectrum of conical SHF in the broadband light source (BBS), these advantages are more suitable for sensing applications. The experimental results show that the finer the taper diameter, the higher the sensitivity of salinity and temperature. When the taper diameter is 8.23 μm, the salinity sensitivity of the sensor can reach 0.3347 nm/‰, and the temperature sensitivity can reach -0.4270 nm/℃.

Dual-Parameter Fiber Sensors for Salinity and Temperature Measurement Based on a Tapered PMF Incorporated With an FBG in Sagnac Loop

“…𝑙 represents the effective length of interferometer. The dip wavelength can be given as 𝜆 𝑑𝑖𝑝 = 2∆𝑛 𝑒𝑓𝑓 𝑙 (2𝑚 + 1) ⁄ , 𝑙 is fixed, and 𝑚 is an integer [26]. Therefore, the RI sensitivity 𝑆 𝑅𝐼 can be expressed to [27]:…”

The Structure and Applications of Fused Tapered Fiber Optic Sensing: A Review

“…Optical tweezers capture microparticles by adjusting laser power, featuring advantages such as low cost and high efficiency, and are widely used in particle manipulation and levitation on a microscopic scale [27,28]. The Mach-Zehnder Interferometer (MZI) achieves high sensitivity sensing by measuring relative phase changes, suitable for measuring optical path differences [29,30]. The Fiber Loop Ringdown (FLRD) forms a light ring by connecting two optical couplers, achieving stable signal attenuation for rapid response and high sensitivity measurements [31,32].…”

Adaptive Fiber Ring Laser Based on Tapered Polarization Maintaining Fiber in Sagnac Loop for Temperature and Salinity Sensing

“…However, the sensitivity for long-term operation will decrease due to the timeliness of the long-term composite of gold film and optical fiber. To achieve dual sensing of temperature and salinity, Zhao et al proposed employing a Mach Zender interferometer structure with tapered side hole optical fiber [15]. Nevertheless, due to the construction of special optical fiber, their air holes are vulnerable to collapsing while being drawn.…”