Proceedings Article | 20 December 2004
KEYWORDS: Wavelength division multiplexing, Fiber Bragg gratings, Waveguides, Polarization, Multiplexers, Optical design, Demultiplexers, Directional couplers, Silica, Dense wavelength division multiplexing
In wavelength division multiplexing (WDM) systems, such as the fiber-to-the-home (FTTH) service (e.g., wavelength 1.31/1.55/1.49 mm in the EPON and wavelength 1.31/1.545/1.5x mm in the APON), coarse and dense WDM are two key technologies. In general, it takes two steps to accomplish this mixing (coarse/dense) WDM functions. In order to make the WDM device compact and low loss, it is necessary to integrate these two WDM functions into one step. In this paper, we propose two typical designs of the coarse/dense multiplexers, which multiplex the coarse/dense-WDM (C/D-WDM) signals simultaneously. We believe that, although their operation principle is simple, the proposed structures simplify the design of integrated photonic devices and will be needed in future WDM systems, specially for the WDM filter in the FTTH service.
The proposed devices consist of a grating-assisted symmetrical or asymmetrical Mach-Zehnder interferometer with the wideband coupler (WBC) and/or the 3dB coupler. Depending on different operation principles, the WBC coupler operates as a 3dB coupler in two wavelength bands or operates as a 3dB coupler in one wavelength band and a cross-state coupler in another one. In this paper, firstly, the operation principles of the proposed C/D-WDM Multiplexers are demonstrated though an example of multiplexing three signals (l1/l2/l3) in two wavelength bands, where l1 (e. g., 1.31mm) belongs to the first band and l2/l3 (e. g., 1.55/1.5x mm) belong to the second band. Then, the design procedure and simulation results of those C/D-WDM multiplexers and related components such as the WBC coupler and planar gratings, which are based on the silica material, are given. Finally, some related issues such as polarizatin dependence and material dispersion are discussed.
