Polarization-maintaining fibers (PMFs) serve as key optical components for maintaining polarization state stability, and their coating peel force is a core indicator for evaluating mechanical reliability and long-term durability. Conventional peel force testing methodologies suffer from insufficient stability and poor repeatability, while research efforts focusing on adaptability to humid and hot environments remain relatively scarce, which restricts the accuracy and reliability of performance evaluation. Therefore, developing a high-stability testing system and investigating the effects of temperature and humidity on the coating of panda-type polarization-maintaining fibers are crucial for bridging the technical gap and supporting engineering applications.

A specialized peel force testing system was designed to achieve precise regulation of key test parameters. The system integrated a rail groove structure with a vertical fixing mechanism to secure PMFs, ensuring a consistently controllable peel length of 4 cm. Two adjustable peel speeds (300 mm/min and 500 mm/min) and an initial tension range of 0.04 N to 0.08 N were configured to simulate actual peel conditions. Two types of panda-type PMFs with cladding diameters of 80 μm and 125 μm were selected as test specimens. For verifying the stability and repeatability of the testing system, 50 consecutive peel tests were conducted on the 80 μm PMFs under standard environmental conditions (23 ℃±2 ℃, 50% relative humidity). To explore the effects of temperature and humidity on peel force, the 125 μm PMFs were preconditioned under 25 different temperature-humidity combinations for 24 hours prior to testing. During the tests, peel force-displacement curves were recorded in real time, and the evolution patterns of shear stress during the peel process were analyzed by combining experimental data with theoretical derivation.

Stability verification results for the 80 μm PMFs yielded a standard deviation (Std) of 0.0196 N and a coefficient of variation (CV) of 2.49% (Table 1), indicating that the developed testing system exhibited low data dispersion and excellent stability and repeatability. Analysis of the peel force-displacement curves revealed three distinct stages during the PMF peel process: linear elasticity, yield softening, and debonding (Fig.2). Environmental factor tests showed that temperature and humidity exerted significant effects on the peel force of the 125 μm PMFs. Specifically, high-humidity environments weakened the interfacial adhesion between the fiber core and coating. With the increase in relative humidity, the peel force of PMFs decreased significantly. Under extreme high-humidity conditions (60 ℃, 90% relative humidity), the peel force decreased by about 10% compared to the standard environment. In contrast, the influence of temperature on peel force was relatively mild within the tested range, indicating that humidity was the dominant environmental factor.

The developed peel force testing system, by integrating a rail groove structure and a vertical fixing mechanism, achieves precise control of key test parameters and exhibits outstanding stability and repeatability. This study systematically reveals the evolution characteristics of shear stress during the PMF peel process and clarifies the significant influence of humidity on peel force by weakening interfacial adhesion. This study not only provides an important reference for the performance evaluation and quality control of PMFs but also offers a theoretical basis for the environmental reliability design and service life prediction of optoelectronic devices based on PMFs. This study contributes to improving the PMF evaluation technology system and promoting the wide application of PMFs under harsh environmental conditions.