A novel multiband filter design based on ring resonators and DSP approach

This paper proposes a novel ring resonator based optical filter that has an outstanding multi narrow band response due to adopting quasi structures such as Thue-Morse sequence as the radius-pattern. This capability introduces this design approach as an effective method for the design of filters for emerging dense wavelength division multiplexing networks. The design process incorporates analysing through the transfer matrix method and the powerful discrete-time signal processing techniques. Giving an adequate overview of analysing basic optical building blocks in the Z-domain, the procedure develops to analysing any optical structure imposed by mathematical sequences. The proposal is discussed employing pole-zero diagrams, discrete-time signal processing approach including apodization techniques. The point of the discrete-time signal processing approach is that the effect of dominant optical parameters over operation is clarified through the pole-zero position. Features like number of poles, bandwidth, and position of stop-bands can be controlled using ring diameter ratio. Finally, apodization of coupling coefficients attains a filter with an FWHM of 0.3 nm.