Simultaneous wavelength and frequency encoded microstructure based quasi-distributed temperature sensor

Xiaolei Li,Duan Liu,Perry Ping Shum,Jianghai Wo,Deming Liu,Ruibing Liang,Qizhen Sun,Jiejun Zhang

doi:10.1364/oe.20.012076

Abstract

A novel microstructure based temperature sensor system using hybrid wavelength-division-multiplexing /frequency-division-multiplexing (WDM/FDM) is proposed. The sensing unit is a specially designed microstructure sensor both frequency and wavelength encoded, as well as low insertion loss which makes it have the potential to be densely multiplexed along one fiber. Moreover, the microstructure can be simply fabricated by UV light irradiation on commercial single-mode fiber. Assisted with appropriate demodulation algorithm, the temperature distribution along the fiber can be calculated accurately. In theory, more than 1000 sensors can be multiplexed on one fiber. We experimentally demonstrated the feasibility of the scheme through building a sensor system with 9 microstructures multiplexing and with temperature resolution of 0.4°C.

Highlights

Optical fiber sensor (OFS) has attracted a lot of attentions over the past two decades
intrinsic Fabry-Pérot interferometric (IFPI) sensors, which are constructed inside the optical fiber itself, reduce the bonding difficulties experienced in extrinsic Fabry-Pérot interferometric (EFPI) sensor fabrication
According to the pitch of the phase masks employed in the fabrication process, the sensors can be divided into three groups: 1054.86nm (Group 1), 1065.20nm (Group 2), and 1075.55nm (Group 3) which are marked with different colors of red, green and blue, respectively

Summary

Introduction

Optical fiber sensor (OFS) has attracted a lot of attentions over the past two decades. IFPI sensors, which are constructed inside the optical fiber itself, reduce the bonding difficulties experienced in EFPI sensor fabrication They provide good merits such as miniature size, continuous geometry, robust structure, and versatile installation. FBGs play an important role in OFS because of their intrinsic nature and advantages such as wavelengthencoded operation [14,15,16] These in-line fiber reflectors can form the IFPI sensor system without the coupling and alignment efforts. High finesse and wide spectral widths could be achieved with superimposed chirped Bragg gratings This technique was expensive and complicated due to the fabrication of chirped FBGs. In this paper, we proposed a microstructure temperature sensor which can be simultaneously wavelength and frequency encoded. An optical spectrum analyzer (OSA) connected to the port 3 is used to monitor the reflect spectrum by the microstructure in order to control the reflectivity and the band width

Sensing principle

Multiplexing principle

Data processing method

Experimental results and discussion

Conclusion