Add-drop multiplexer with UV-written Bragg gratings and directional coupler in SiO2-Si integrated waveguides

The needs of wavelength multiplexers is growing and therefore optical add-drop multiplexers (OADMs) become key components for the advanced high bit rate telecommunication networks. Currently, one of the solutions to make OADMs use fiber Bragg gratings and circulators. In order to take advantage of integrated optics and to avoid the use of expensive circulators, we perform this kind of OADM in ridge silica waveguide on silicon. This technology makes possible short based directional coupler (DC) device. In previous work, we firstly realized an OADM which involves a symmetrical directional coupler combined with two Bragg gratings inside the coupling zone. The results meet difficult tradeoff between a high extinction ratio and a narrow spectral width of the rejection band. This paper reports some fabrication improvements for DC-OADM that lead to more efficient components, progress results from a lot of works concerning both the photo-writing process of Bragg gratings and the lowering of the waveguide internal stresses. Thus, we show that apodization of gratings and low birefringence in the waveguides enables us to achieve DC-OADM with an extinction ratio of 30 dB and a spectral bandwidth less than 1.5 nm