A Novel U-Shaped and Microchanneled Optical Fiber Temperature Sensor Fabricated by LIGA-Like Process

This paper developed a U-shaped, microchanneled optical fiber temperature sensor based on macrobending-induced whispering gallery mode (WGM). The proposed novel U-shaped, microchanneled optical fiber temperature sensor is fabricated by a LIGA-like process to obtain the microstructure molds on the wafer for the replica molding method. This process can be used for mass production such that the cost of the sensors can be reduced significantly. In temperature sensing experiments, the resonant wavelengths of the WGM sensor exhibited blue shifts as the temperature increased. The temperature sensitivity of the sensor can reach 0.624 nm/°C, with a maximum linearity of 0.994. The results of a system repeatability analysis show a standard deviation of 0.00547 nm/°C in sensitivity following three heating cycles, indicating superior repeatability. Therefore, the WGM temperature sensor possesses superior stability and repeatability.

I. Introduction

Temperature sensing is especially important and indispensable as an engineering application. Normally, a thermocouple, which consists of two dissimilar metals joined together at one end, is used in temperature sensing. The disadvantages of a thermocouple, however, include poor resistance to both electromagnetic interference and corrosion. As such, with its high sensitivity, small size, and effective electromagnetic resistance, the optical fiber sensor is more applicable to temperature sensing [1]–[6]. The most common optical temperature sensing techniques include the utilization of fiber Bragg grating (FBG) [7]–[9], long period fiber grating (LPFG) [10]–[12], interferometric fiber, and photonic crystal fiber temperature sensors [13], [14]. The disadvantages of these methods include the need for expensive apparatus and that the components involved are complex and unsuitable for mass production. To overcome these disadvantages, in this study we propose a novel U-shaped, microchanneled WGM optical fiber temperature sensor that is simple, low in cost, and robust.