Optical Communications, 2nd Edition

2

OPTICAL FIELD RECEPTION

In optical receivers, the incoming light field in either a space or fiber system is generally collected or focused by front end optics on to the detecting surface, as was shown in Figures 1.4. In space systems, these front ends usually involve combinations of lenses that act to image the received field onto the photodetector, thereby creating a focused field that represents the actual field being observed. In fiber systems, the fiber field is generally coupled directly to the detector surface. To determine the performance of the overall link, it is first necessary to accurately describe these received fields and the manner in which they are converted to the photodetector field. This requires a review of basic lens and focusing equations.