Lens coupling is a special technique for coupling two optical fibers. In this coupling principle, which is used in the lens connector, the optical fibers to be coupled have a lens-shaped cut through which as much of the radiation as possible is fed into the second optical fiber at the transition point.
Lens coupling is also known as convex coupling. In this type of coupling, in contrast to oblique ground-glass coupling and face-to-face coupling, both optical fibers have a direct physical contact, Physical Contact( PC). Lens coupling uses an expanded beam technique. Here, the light beam at the end of the optical fiber is magnified and parallelized by a spherical lens. The second ball lens, which receives the light beam, focuses the broadened light beam so that the second optical fiber receives the light beam.
Compared to face-to-face coupling, lens coupling has the advantage of higher return loss, resulting in fewer reflections that reduce the light energy to be transmitted. However, it exhibits mechanical wear due to the direct contact of both optical fibers. The return loss reaches values around 30 dB when the two end faces are in physical contact. With precise mechanical grinding, values of 40 dB and more are achieved.
The EBO connector, whose lenses are spherical or hemispherical, has a certain similarity to the lens connector.