Abstract

There is an urgent need to find an inexpensive way to increase a transmission capacity to respond to the rapid and global spread of the Inter-net. An effective approach is to install wavelength division multiplexing (WDM) systems with a narrower channel spacing and higher port counts by using relatively low-cost electronics. However, such low-cost systems have severe optical filter specifications, and this makes the filters expensive. An interleave filter, which divides dense WDM signals into two groups of even and odd channels, is attractive because it can relax the specification requirements for demultiplexers in WDM systems.Various interleave filter structures have been proposed and demonstrated.^1–5 Of these, a lattice-type waveguide interleave filter composed of cascaded Mach-Zehnder interferometers (MZIs) is promising since it is fabricated using planar lightwave circuit (PLC) technology. Moreover, it can be mass-produced cost-effectively and is both highly reliable and capable of high density integration. To reduce costs further, we must improve the production yield, which is mainly decided by the path length and coupling ratio errors in the MZIs. Although the path errors can be compensated for by using heaters, ⁶ there is no effective way to compensate for the coupling error.

© 2002 Optical Society of America