Multi-channel optical filter design using superimposed Bragg gratings

In recent years, designing of multi-channel optical filters has become an essential and inseparable part of wavelength-division-multiplexing (WDM) and dense wavelength division multiplexing (DWDM) systems. In this paper, efficient design of multi-channel optical filters using superimposed Bragg gratings is investigated. We use Transfer Matrix Method (TMM) for designing where resulted reflection spectrum is apodized with sinc function. For loss compensation, by choosing suitable sinc parameter (k = 0.3), sidemode suppression ratios (SMSRs) of approximately 60 and 55 dB are computed for single-peak and 9-peak filters respectively. The rest of specifications of designed filter are: 9 channels with 1.55 mu m central wavelength and 1 nm channel spacing. We show that superimposed Bragg grating can be used to design efficient multi wavelength optical filters with arbitrary characteristics.