Up to now, there have been no complete theoretical researches and field experiment reports on the fiber fusion loss at high altitude. Therefore, we have conducted an exploratory study on the fiber splicing loss at high altitude, and firstly analyze the influence of mode field diameter mismatch, axial offset, angle tilt or end face gap affected by high altitude on splice loss, and then discuss the influence of fusion-splicing parameters on splice loss. Besides, a mathematical model for reducing the splicing loss of single-mode fiber at high altitude is established by combining the effects of temperature, humidity, oxygen content, atmospheric pressure, gale and gravity. We have conducted repeated field fusion experiments in different altitude areas (53, 2980, 4000, 4200, 4300, 5020, and 5200 m) more than once, hence obtaining a large number of field experimental data, making a deep comparison between typical “plain” area and typical “high altitude” area. The splice loss of most fusion points achieved successfully has been reduced by at least 0.07 dB. The simulation results are basically consistent with the theoretical analysis. Ultimately, the method proposed has been directly applied to on-site splicing engineering in high altitude environment and achieves good results.

Up to date, there has been no complete theoretical research and no field experimental reports on the fiber fusion strength in high altitude environments. Therefore, we have conducted an exploratory study on the fiber fusion strength at high altitudes, and firstly analyzed the crack growth characteristics of splicing points, and then considered the influence of fusion variables and parameters on fusion strength. A mathematical model to improve the fiber fusion strength in high altitude environment is established by pondering over the joint effect of temperature, humidity, oxygen content, atmospheric pressure, high wind and gravity. Furthermore, we have implemented multiple field fusion experiments in different altitude areas (53, 2980, 4000, 4200, 4300, 5020 and 5200m). The simulation results are basically consistent with the theoretical analysis. Ultimately, the method proposed has been directly used in the splicing projects at high altitudes, achieving good results.

In extremely cold regions, OPGW optical cables are prone to anomalies due to icing, especially when their internal fiber length is easily depleted, which then seriously affects the normal operation of the entire power communication system. Therefore, this paper proposes a nonlinear inversion analysis method that couples catenary theory with biaxial statics to monitor the variation of the FEL under extreme icing conditions. First, the quantitative mapping relationship between BFS and the dynamic evolution of FEL has been established, and a three-dimensional response model, encompassing tension, ice thickness, and FEL has been constructed. Subsequently, an inversion algorithm for ice thickness based on BOTDR frequency shift signals has been developed by introducing horizontal tension as a key intermediate physical quantity. When the FEL decreases from 0.2% to 0.1%, the corresponding EIT can evolve from 0.08 m to 0.16 m approximately, indicating that the system has entered a warning zone characterized by a sharp increase in strain. The proposed model has successfully achieved the transition of distributed monitoring theory from physical perception to quantitative inversion, thereby providing theoretical support for early ice warning and disaster prevention assessments of in-service power optical cables.