The first is Single-Mode Fiber (SMF). Single-mode fibers have a small core diameter, typically 9 or 10 microns. Due to the small core diameter, light can only propagate in one path (that is, one mode) during transmission, making single-mode fiber with low signal attenuation and dispersion, suitable for long distance and high-speed transmission. Single-mode fiber is mainly used in optical communication fields, such as long-distance transmission, metropolitan area networks and data center networks.

The second is Multi-Mode Fiber (MMF). Multimode fibers have a larger core diameter, typically 50 or 62.5 microns. Due to the large core diameter, the multi-mode fiber can support the transmission of multiple modes, resulting in the dispersion and attenuation of the signal during the propagation process. Compared to single-mode fiber, multimode fiber has a shorter transmission distance and is commonly used in small-range communication applications such as local area networks (Lans), short-range communications, and data centers.

A Coupler Fiber (CF) is an optical fiber device that divides an input optical signal into multiple output channels. Split-beam couplers usually adopt Y or star structure, and are widely used in optical communication fiber network, distributed sensing, fiber measurement and biooptics.