Double- Tube Enhanced Packaging of Optical Fiber Sensors

Under current embedded fiber optic packaging technology, when a mechanical structure is subjected to alternating loads such as temperature or force over a long period, the different thermal expansion coefficients between the fiber optic and metal can lead to loosening and sliding of the connection surface. To solve this problem, this study proposes a double quartz tube symmetrical stepped fiber structure based on the principle of mechanical connection. This structural design enables a more reliable connection between the stepped fiber optic and metal. Based on the theory of thermoelasticity, a theoretical analysis was conducted on stepped optical fibers, and a reasonable preparation process for stepped optical fibers was proposed. The controlled variable method was used to analyze experimentally the various process parameters to improve their tensile strength. A metallized stepped fiber Bragg grating (FBG) was successfully prepared, and the effectiveness of the stepped structure was verified through experimental comparison. Experimental results show that the tensile strength of the double quartz tube symmetrical stepped optical fiber is improved by processing technology and can reach 750 MPa, which is 9. 25 degrees o higher than that of the bare optical fiber obtained by mechanical removal of the coating layer (686. 5 MPa). The temperature sensitivity of the prepared metallized stepped FBG reaches 15. 59 pm/degrees C at a temperature resolution of 0. 064 degrees C/pm. The results show that metallized stepped FBG exhibits a more stable temperature sensing performance than the metallized FBG without reducing temperature sensitivity.