A Review of Microfiber-Based Temperature Sensors

2018 Sensors  
Optical microfiber-based temperature sensors have been proposed for many applications in a variety of industrial uses, including biomedical, geological, automotive, and defense applications. This increasing demand for these micrometric devices is attributed to their large dynamic range, high sensitivity, fast-response, compactness and robustness. Additionally, they can perform in-situ measurements remotely and in harsh environments. This paper presents an overview of optical microfibers, with a
more » ... focus on their applications in temperature sensing. This review broadly divides microfiber-based temperature sensors into two categories: resonant and non-resonant microfiber sensors. While the former includes microfiber loop, knot and coil resonators, the latter comprises sensors based on functionally coated/doped microfibers, microfiber couplers, optical gratings and interferometers. In the conclusions, a summary of reported performances is presented. Abstract: Optical microfiber-based temperature sensors have been proposed for many applications in a variety of industrial uses, including biomedical, geological, automotive, and defense applications. This increasing demand for these micrometric devices is attributed to their large dynamic range, high sensitivity, fast-response, compactness and robustness. Additionally, they can perform in-situ measurements remotely and in harsh environments. This paper presents an overview of optical microfibers, with a focus on their applications in temperature sensing. This review broadly divides microfiber-based temperature sensors into two categories: resonant and non-resonant microfiber sensors. While the former includes microfiber loop, knot and coil resonators, the latter comprises sensors based on functionally coated/doped microfibers, microfiber couplers, optical gratings and interferometers. In the conclusions, a summary of reported performances is presented. Sensors 2018, 18, 461 2 of 26 micron size using a flame and the resulting taper is then drawn down to submicron dimensions by pulling the taper around a heated 80 µm sapphire rod. This method allowed the fabrication of a taper with~440 nm radius and a 0.3 dB/m loss at the telecom wavelength λ = 1.55 µm. Lower losses, on the order of 0.001 dB/mm at λ~1.55 µm, were obtained by using the so-called flame brushing technique. The standard setup frequently used for fabricating MFs is shown in Figure 2 . The fiber is pulled by two translation stages that have submicron precision while a small region of the fiber is heated by either a flame (flame brushing technique) or by an electric microheater (modified flame brushing technique) [2]. Sensors 2018, 18, x FOR PEER REVIEW 2 of 24 Microfiber Manufacture MF fabrication is a relatively simple and low-cost process. Low loss, sub-micron diameter MFs were originally fabricated using a two-step technique [5] , where the optical fiber is firstly drawn to a micron size using a flame and the resulting taper is then drawn down to submicron dimensions by pulling the taper around a heated 80 μm sapphire rod. This method allowed the fabrication of a taper with ~440 nm radius and a 0.3 dB/m loss at the telecom wavelength λ = 1.55 μm. Lower losses, on the order of 0.001 dB/mm at λ ~ 1.55 μm, were obtained by using the so-called flame brushing technique. The standard setup frequently used for fabricating MFs is shown in Figure 2 . The fiber is pulled by two translation stages that have submicron precision while a small region of the fiber is heated by either a flame (flame brushing technique) or by an electric microheater (modified flame brushing technique) [2]. Figure 2. The flame brushing technique: a flame travels under an optical fiber clamped at its extremity onto two computer-controlled stages which are moving apart. Sensors 2018, 18, 461 3 of 26 of complex-shaped tapered fibers was based on controlling the motion of the heat source relative to the fiber, as well as its temperature distribution [12] .
doi:10.3390/s18020461 pmid:29401718 pmcid:PMC5855437 fatcat:tc655mj4czhpzlenfcad5dz2ma