Fiber collimators are upstream components of optical communication components and are a fundamental component of optical communication systems.

　　The fiber collimator places the end face of the fiber at the focus of the collimating lens, collimates the beam, and then fine-tunes the fiber end face near the focus to achieve the desired working distance. Therefore, the working distance of the collimator is related to the spacing between the lens and the tip of the fiber. The direct isolation distance between any fiber and fiber exceeds a few hundred microns, which introduces large insertion loss into the system, optical collimator elements incorporate lenses into the fiber and space regions such that optical transmissions do not have large insertion loss at tens or even hundreds of millimeters.

　　The autofocus lens in the fiber collimator is a graded index cylindrical optical lens with focusing and imaging capabilities. The difference between the self-focusing lens and the ordinary lens is that the refractive index distribution of the material of the self-focusing lens gradually decreases in the radial direction, so that the light transmitted in the axial direction can be continuously refracted, thereby, the emitted light can be smoothly and continuously concentrated to one point.

　　Grin-Lens is the first collimating lens to be used as a fiber collimator. Later, C-Lens was introduced into the fiber collimator. C-Lens can increase the working distance by increasing the radius of curvature of the end face, which is easier to change parameters than Grin-Lens. Therefore, it has advantages in long working distance applications, and in general applications, it is also very popular due to its cost advantage. However, in the filter type WDM, the lens needs to be coated, and the G-Lens has an absolute advantage because its end face is flat.