Study on the effects of organic bonding agent and low-temperature glass solder process on the performance of compact packaged fiber optic temperature sensors

In this study, organic bonding agent and low-temperature glass solder bonding are selected to prepare compact fiber Bragg grating (FBG) temperature sensors, and then temperature characterization experiments are conducted separately. Specifically, the effects on the temperature sensitivity of encapsulated FBGs of different bonding materials are derived through theoretical analysis and simulation. Two different bonding materials are selected for the preparation and measurement of the temperature sensors, and the reproducibility of their preparation is analyzed. By comparing the temperature characteristics with the bare FBG, the results show that the sensitivity of the organic adhesive encapsulation is 30.32 pm/°C and that of the low-temperature glass solder encapsulation is 27.48 pm/°C within the range of 0-50°C, and both of them reach a linearity of 0.9999, which is one order of magnitude higher than that of the bare FBG. The response rates all reach within 1s, and the sensor encapsulated with low-temperature glass solder has better anti-interference ability. Finally, the long-term stability of the two encapsulation materials was evaluated, and the wavelength of the organic adhesive encapsulation structure drifted and the temperature sensitivity decreased, while the low-temperature glass solder encapsulation structure performed well, which indicated that the performance of the fiber optic FBG temperature sensors prepared by the low-temperature glass solder bonding process was better than that of the organic adhesive.