## 1 Introduction  
Due to the development of space technology in recent years, the service cycle of spacecraft has become much longer in a harsher environment. Long-term operation in such an environment invites numerous serious challenges, including space radiation, micrometeoroid impacts, and impacts from space debris, all of which can cause surface structure wear, buckling, and possibly the extrusion of internal structures. Spacecraft are at risk of being damaged, and it is possible for a space mission to fail as a result. At present, a surveillance network can only monitor debris larger than 10 cm in diameter, and cannot detect tiny fragments smaller than 1 cm. In order to timely discover and prevent potential impacts to the compression state of the internal structure of the spacecraft caused by small debris, it is urgent to carry out spacecraft pressure detection research [1; 2; 3; 4]. In the case of a space station, it is essential for the space station to monitor the structural condition of the load-bearing components, the pressure capsule skin, and other components during service in order to prevent structural fatigue or damage. Additionally, large space structures such as space stations need to be docked and rendezvoused many times during their service, and the impact of docking on the structure needs to be tested. However, for spacecraft, working in the space environment, which contains strong magnetic noise and floating charged particles, poses great challenges to traditional electronic sensors. Optical fiber sensing technology has been developing along with optical fiber communication technology in recent decades. Fiber Bragg Gratings (FBG) are one of the most widely used fiber sensors due to their optical selectivity. Compared with traditional sensors, FBG have unique advantages in space, such as strong anti-electromagnetic interference performance, small size and wide measurement ranges [5]. FBG can monitor the temperature, strain and other parameters of spacecraft structure with high precision and stability in real time under a complex environment, and sense the state data of a spacecraft structure in an all-round way so as to effectively ensure the normal operation of spacecraft and the life safety of astronauts, and improve the reliability and safety of space missions. In 2022, [PERSON] et al. [6] used a wide-range FBG strain sensor with a surface-attached carbon fiber matrix to measure strain and load on aircraft landing gear, and the strain sensitivity was 1.14 pm/\(\mu\epsilon\). [PERSON] et al. [7] pasted FBG onto a test piece and combined the data collected by the sensor with machine learning to achieve real-time damage classification and structural health monitoring requirements. These were monitored based on FBG axial stress changes. However, FBG will be affected by lateral stress in practical application. In general, in order to detect all the strain information of the structure, it is necessary to deploy multiple optical fiber sensors inside the material with their vertical axes in the same direction as the stress. Obviously, it is very difficult to lay out these huge fiber Bragg grating sensors, and directly leads to increases in system cost, a more complex structure, and even potentially the weakening of the main material, causing influence or even damage to it [8; 9; 10; 11; 12; 13]. In addition, this method needs to process a large amount of data when applied to large-scale systems, which greatly limits the application of fiber Bragg gratings in engineering. Therefore, in view of the difficulties in lateral force monitoring of spacecraft, fiber Bragg gratings' radial stress characteristics are considered for sensing. [PERSON] et al. [14] proposed the fabrication of overlapping Bragg gratings on polarization-maintaining fiber; that is, two gratings with different center wavelengths are written at the same position to realize lateral strain measurement. Because of the birefringence effect, four Bragg peaks will be output.