Optical device for compensation of multiple wavelengths and working distances in dual-fiber collimators

A particular focusing arrangement in a dual fiber collimator improves the transmission efficiency and ease of alignment of the collimator. In particular, the collimator includes two optical fibers mounted in a dual-fiber ferrule. The fiber end-faces are co-planar with the angle-polished end-face of the ferrule and displaced along the optical axis of the ferrule. The collimator unit also includes a first focusing element centered along the optical axis of the ferrule and positioned such that its back front focal point is between the two end faces of the fibers. An advantage provided by this arrangement is that by changing the fiber polish angle and polish azimuth, relative to a line connecting the fiber centers, superior coupling from one fiber to the other can be achieved, even with different working distances and at various wavelengths.