Fiber optic Components are optical fiber processed into optoelectronic devices with certain functions. Among them, fiber optic devices based on single-mode fiber are widely used. The fiber optic devices that can be applied in fiber optic communication mainly include fiber amplifier, fiber laser, fiber coupler, fiber polarizer and fiber filter. Their main functions are to realize direct light amplification, generate laser, distribute or combine the optical signal power among different optical fibers, turn the input light into linearly polarized light and select or filter out specific wavelengths of light waves from different wavelengths. With the advantages of low additional loss, high reliability and easy operation