Abstract

A planar waveguide lattice filter architecture based on ring resonators has been investigated. A potential application is for very narrowband fdters in WDM systems and networks. The merits of the architecture are described, and practical considerations for realizing such filters are dscussed including the design for non-zero waveguide loss and compensation of fabrication variations. The proposed architecture is shown in Fig. 1 for a third order filter. The architecture is similar to fiber architectures [1,2]; however, the waveguide layout minimizes the ring length so that the maximum Free Spectral Range (FSR) can be achieved given the bend radius limit for a particular fabrication process. When described in the 2-domain, the transfer functions for E_ol/ E_il and E_o2/E_i2 are Autoregressive (AR) responses having only poles, while E_ol/E_i2 and E_o2/E_i1 are Autoregressive Moving Average (ARMA) responses having both poles and zeroes. The architecture is general in the sense that it can be extended to any number of stages and the location of the poles can be set by determining appropriate coupling ratios and phases for each stage using a filter synthesis algorithm previously described [3].

© 1996 Optical Society of America