This article provides a detailed introduction to the structures, working principles, and performance characteristics of all-polarization-maintaining mode-locked fiber lasers based on different mode-locking mechanisms, such as SESAMs, two-dimensional materials, nonlinear. This article provides a detailed introduction to the structures, working principles, and performance characteristics of all-polarization-maintaining mode-locked fiber lasers based on different mode-locking mechanisms, such as SESAMs, two-dimensional materials, nonlinear. Owing to their excellent resistance to environmental interference and high stability, all-polarization-maintaining mode-locked fiber lasers hold significant application value in various fields, including industrial processing, communications, medical applications, and military applications. This. In fiber optics, polarization-maintaining optical fiber (PMF or PM fiber) is a single-mode optical fiber in which linearly polarized light, if properly launched into the fiber, maintains a linear polarization during propagation, exiting the fiber in a specific linear polarization state; there is. How measured fiber parameters help to choose the best coupling and collimation optics. A stable measurement setup is fundamental for any successful measurement. A major cause of frustration and error is the need to continuously readjust optomechanical equipment because of continuous instabilities. This method creates a simple, rugged, compact method of splitting or combining. Polarization-maintaining (PM) fiber couplers are critical components in advanced optical communication and sensing systems.