Evaluation of optical channelizers in terms of RF performance

The demonstration of RF photonic links with bandwidths of 100 GHz or more is expected in the near future, due to rapid and continuing progress in modulator and detector technology. Since it is very difficult to electronically process such a large bandwidth after photodetection, photonic approaches that reduce the burden on the electronics are increasingly relevant. One such approach is an optical channelizer, where an RF modulated optical carrier is optically dispersed onto a detector array. Each element of the array only sees a portion of the original wideband RF spectrum. We analyze the RF performance of optical channelizers in terms of crosstalk and uniformity of response. Both direct detection and heterodyne channelizers will be considered. Analysis of this kind is necessary for our application, since the usual parameters of a dispersive optical system, such as resolution, resolving power or filter linewidth do not provide enough information to determine the RF performance. The analysis has shown that a Fabry-Perot filter based channelizer cannot provide adequate RF performance, while a grating-based channelizer can. For channelization to 1 GHz channels with a -70 dB crosstalk specification, a total grating length of roughly 80 cm is required, so a multiple bounce geometry is necessary to obtain a reasonably compact system.