Linearized Optical Discriminator

We present design optimization techniques for linear optical frequency discriminator filters using cascaded lattice Mach-Zehnder interferometers (CLMZI). We propose a simple method for reducing the deviation in amplitude linearity, which relies on a slight reduction of the filter's full bandwidth utilization (BWU). It is shown that a reduction in BWU as low as 5% can result in an order of magnitude improvement in the corresponding amplitude linearity. Additionally, by employing a generalized CLMZI (g-CLMZI) filter architecture with geometrically increasing delays, high linearity can be realized. For example, a three-stage (sixth order) g-CLMZI can provide deviation in linearity of less than 0.5% across the desired bandwidth. Both g-CLMZI and CLMZI architectures are optimized using nonlinear optimization techniques. Design examples of both filter types are given.