First Mile Access Networks and Enabling Technologies

Lenses and Mirrors in FSO

A lens is a transparent device made of glass or plastic that can refract light in such a way that the rays form an image. A mirror, on the other hand, forms images by using the principle of reflection as opposed to refraction in a lens. Both lenses and mirrors are used in FSO in assembly of transmitters and receivers.

There are basically two types of lenses: convex and concave (see Figure 6-12). A convex lens directs the light beam toward the central axis of the lens, whereas a concave lens directs the light beam away from the axis of the lens. By looking at the shape of the lens, one can easily determine whether the lens is concave or convex.

Figure 6-12. Concave and Convex Lenses

Note here that convex lenses are used ...