Medium-Temperature Resistance Drawing-Tower Grating Array Fabrication

Drawing-tower grating (DTG) array is a popular choice for temperature sensing due to their networking capabilities and convenience. However, DTG exhibits poor stability in high-temperature environment. As a result, the current usage of DTG sensors is typically limited to below 200 °C. In this study, we investigated the temperature stability of DTG in the medium-temperature range of 400 °C–600 °C from the perspective of engineering practicability. Experimental results indicated that the DTG with post-hydrogen loading could exist at 450 °C for a long time. After hydrogen fixation at 300 °C for approximately 3 min, the mechanical strength of polyimide (PI)-coated fiber could be ensured, thereby ensuring excellent long-term temperature resistance of DTG. In addition, the signal of a 500-m DTG array was demodulated. The results indicated that the transmission loss of the DTG array after aging was about 5.4 dB/km@1550 nm, and the signal transmission within 500 m could be monitored. Furthermore, the experimental results indicated that PI-coated fiber had good mechanical strength after carbonization under the protection of inert gas. Consequently, the fiber optic cable designed with inert gas protection was expected to be developed for medium-temperature sensing in harsh environments, such as petrochemical and aerospace.