Performance comparison of high temperature sensor based on non‐adiabatic silica microfiber and single mode‐multimode‐single mode fiber structure

Abstract

A fiber‐based temperature sensor operating at high temperature was demonstrated using multimode interference effect and its performance was compared with that of two different probes based on a non‐adiabatic microfiber and singlemode‐multimode‐singlemode (SMS) fiber structure. Interference fringes of the output red‐shifted as the temperature increased due to the change in the effective refractive index of the multiple modes inside both structures. The sensor probes were able to measure the temperature variation up to 400°C with a linearity of more than 90%. The temperature sensitivity of the microfiber and SMS sensors is 6.0 pm/°C and 11.1 pm/°C, respectively. Our proposed sensors are simple, relatively cheap to be fabricated, and could operate at high temperatures above 300°C.

Highly sensitive temperature sensor based on multimode‐interference fiber structure with gel cladding

“…In the SMS structure, where the cladding comprises either silica or air, the wavelength shift is determined by the thermo‐optic effect in n eff instead of the thermal expansion effects on D eff and L MM. 15,16 Meanwhile, in the SMS structure with gel cladding, the length of the evanescent field in the cladding is highly sensitive to temperature since the index‐matching gel has a TOC of −3.5 × 10 −4 /°C. To evaluate the thermo‐optic effects on parameters D eff and n eff , we calculated and n eff with respect to Δ n .…”

“…This implies that environmental changes shift specific wavelengths through the parameters of the SMS structure. In this scheme, all‐silica MMI‐based sensors can be used at high temperatures up to 1000°C 14‐16 . However, the wavelength shift mechanism is due to the thermo‐optic coefficient (TOC) of the silica core, which is on the order of 10 −6 /°C.…”

Refractive index sensing properties of microfiber cascaded‐long‐tapers

“…By guiding the optical signal to transmit in the optical fiber, the spatial optical structure can become more compact, which is conducive to the development of optical systems or devices with compact structures. 1,2 The Mach-Zehnder interferometer (MZI) can usually be designed by cascade-welding different kinds of optical fibers, such as noncore-fiber (NCF), 3 multimode fiber (MMF), 4 hollow-core fiber (HCF), 5 thin core fiber (TCF), 6 seven-core fiber (SCF), 7 and so forth, wherein different light beams or optical transmission modes will be produced in the Mach-Zehnder interference way and used for determining the refractive index (RI), temperature, and other environmental parameters. However, the introduction of these special fibers results in a more complex structure and higher cost.…”

Strain-Insensitive Biocompatible Temperature Sensor Based on DNA Solid Film on an Optical Microfiber

“…O PTICAL fiber sensors are immune to electromagnetic interference, mechanically flexible, light-weighted, and can be miniaturized with a small footprint. With these advantages, optical fiber sensors have found various types of applications in measurement and monitoring physical properties [1]- [3] such as temperature [4], strain [5], refractive index (RI) [6], and humidity [7], to name a few. Especially, temperature sensing has been based on key fiber optic technologies including fiber Bragg grating (FBG) [8], photonic crystal fiber (PCF) [9], [10], external Fabry-Perot interferometer on fiber tip (EFPI) [11] and tapered micro/nanofiber [12], which are still being actively pursued in recent years.…”