A wrapped carbon nanotube coating for enhanced high-temperature mechanical performance and rapid thermal response of optical fiber sensors

Optical fiber sensors, particularly fiber Bragg grating (FBG) sensors, are attractive for transient temperature monitoring in harsh environments but often suffer from limited high-temperature mechanical performance and slow thermal response due to conventional polymer coatings. To address these issues, a novel carbon nanotube (CNT) wrapping method was developed to simultaneously provide mechanical protection and enhance thermal conduction. Unidirectional CNT films were drawn from a vertically aligned CNT forest and helically wound around bare fibers with controlled winding angles and layer numbers to form an ultrathin protective coating. The CNT film adhered directly to the fiber surface through van der Waals interactions. After exposure to 500 °C for 1 hour and subsequent tensile testing at room temperature, the CNT-wrapped optical fibers exhibited a tensile strength of approximately 3 GPa, which is about four times higher than that of polymer-coated optical fibers, while maintaining high flexibility with a bending diameter of about 15 mm. Furthermore, the results of experiments to measure transient temperature changes with pulsed laser heating showed that the CNT-coated FBG sensor achieved a thermal response time of 20 ms, nearly three times faster than polymer-coated ones. This work demonstrates the superior high-temperature mechanical performance and the ultrafast thermal transfer capability enabled by the novel CNT coating. • A thin CNT film was wrapped onto bare optical fibers as a high-temperature coating • CNT-coated optical fibers retain high tensile strength after heating up to 500 °C • The CNT coating preserves fiber flexibility after high-temperature exposure • CNT-coated FBG sensors exhibit rapid and sensitive transient thermal response • Coating microstructure enables both mechanical protection and efficient heat transfer