Performance Analysis of Ti and Cu Rich SMA-Coated Optical Fiber Sensors for Low and High-Temperature Condition Monitoring of Systems

Abstract

Solid state sensor characteristics of NiTi and Cu based shape memory alloys (SMAs) are reported for both high and low temperatures (−50 ℃ to 250 ℃). The effect of two different alloys on the martensitic transformation (MT) are demonstrated at low and high temperature ranges. The sensor was fabricated with novel technique of SMA coating on optical fiber through flash evaporation process. The morphology, phase transformation, and actuation characteristics of such coated optical fibers were studied through optical microscopy, differential scanning calorimetry, and laser displacement sensor respectively. The effects of different materials on characteristic transformation temperatures, enthalpy and entropy values were investigated. During heating we have observed that both SMA coated fiber straightened with respect to the initial state. However, more bending was observed during cooling for the SMA coated fibers. Such sensing behavior arises due to induced strain of thin SMA coating on optical fiber during exposure at different temperature ranges. We have observed maximum actuation of ~8 mm during heating and ~5 mm during cooling for NiTi rich samples, whereas ~4 mm during heating and ~12 mm during cooling was detected for Cu rich SMAs. This sensing behavior of the SMA coated optical fiber affects the intensity of optical signal passing through it. NiTi rich SMA coated fiber shows better sensitivity during heating while Cu rich SMA shows better response for cooling cycles. Hence, we can conclude that SMA coated optical fiber can potentially be used for sensing and monitoring applications at varying temperature ranges. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.