OPTICAL LATTICE-TYPE ADD-DROP MULTIPLEXING FILTERS AND THEIR USE IN WDM NETWORKS

This paper examines the use of optical lattice filters as wavelength a dd/drop devices in WDM ring or bus networks. Various filter design met hodologies are investigated, including methods to produce passband-fla ttened low sidelobe filters. The effects of cascading such devices are examined from the viewpoint of net transmission bandwidth and coheren t or ''in-band'' crosstalk and are compared with the use of pairs of 1 :n wavelength multiplexer/demultiplexers to perform the add/drop funct ion. We find that the use of optical lattice-type add/drop filters res ults in a much broader net transmission bandwidth than even the use of pairs of passband-flattened 1:n wavelength multiplexer/demultiplexers . The use of passband-flattened optical lattice filters with correspon dingly broad stopbands helps to significantly broaden the coherent cro sstalk-limited bandwidth. The characteristics of a four-channel add/dr op filter fabricated using silica waveguide technology and the perform ance of a three-node 3 x 2.5 Gbps WDM ring network built using a numbe r of these devices are reported. (C) 1998 Academic Press.