From element automatic control view, we propose a configuration algorithm for three-level cross-connects in data plane to handle with bypass, grooming and local add/drop traffic of fiber-level, band-level and wavelength-level by a abstract bipartite graph of MG-OXC and bandwidth utilization spectra graph. The configuration algorithm is evaluated by computer simulation as well as validated by experiment on our flexible Multi-functional Optical Switching Testbed (MOST).
Scalability performance of optical node is an important issue in the design of optical cross-connect (OXC) architecture. A practical architecture is expected to be scalable easily with low cost. However, when OXC employed with wavelength converter (WC) to support virtual wavelength path (VWP), the OXC scalability degrade due to the limit number of the WCs and partial sharing characteristic. In this paper, we proposed a new scheme to expand a kind of limit wavelength conversion OXC, share-per-wavelength architecture, which shares the WC within the same wavelength. This scalable scheme is analyzed in detail through comparing various wavelength grouping methods. Furthermore, their blocking performance is studied by using discrete event simulation. The results of the simulation show that our scheme has comparable blocking performance to the architecture without scalability. The small improvement at high initial occupation is because small wavelength grouping lead to a little better sharing efficiency under high load. But when the group becomes too small, for example less than the number of WCs, the repeated WCs will reduce its performance.
In order to reduce the complexity of the optical switching nodes at a reasonable level and increase its capacity at the same time, the concept of multi-granularity was proposed. With the utilization of multi-granularity switching, the number of ports for the optical switching matrices can be decreased. In this paper, we consider the two-stage multiplexing that includes the wavelength multiplexing and waveband multiplexing. A simple algorithm that can realize the grouping from wavelengths into wavebands efficiently is proposed. As the decreased number of the optical switching matrices' ports is determined partially by the number of the nodes passing the waveband path, the length of the waveband path is considered in this algorithm. To group as more wavelengths as possible into wavebands, all the wavelength paths will be evaluated in the algorithm as long as they have common sub-path. This algorithm is also tested in two networks with six nodes, and the saving number of the switching matrices' ports is compared with which using only the one-stage wavelength multiplexing.
The optical signal along the light-path in the optical network will traverse a cascade of optical filters. The equivalent pass-band ofthe cascaded filters decreases in comparison with a single filter, and it is required that the light sources should be much more stable. In this paper, we investigated the cascaded characteristics of FILM filters that are widely used in WDM systems due to their flat pass-band and low insertion loss. Both the influence of amplitude response and the influence of phase response are considered together. Firstly, we give two equations of the pass-band characters and the phase response of FILM filters, and then calculate the variation of the cascaded FILM filters' bandwidth versus the number of the cascaded filters. We evaluated the influence of the filters' phase nonlinearity in more detail. The simulation results imply that the frequency range ofthe cascaded FILM filters under the condition of zero power penalty decreases, and the power penalty curve caused by phase nonlinearity fluctuates more drastically than that without the consideration ofthe phase response.
In common electro-optic modulators (EO), the inherent velocity mismatching between the optical wave and microwave is the major factor hampering efficient modulation. In this paper, we briefly compare periodically reversed electrode and domain reversal scheme (two ways of achieving quasi-velocity- matching), then we give the design principle of the EO modulator using domain reversal scheme. At last, we conclude that the bulk LiTaO3 EO modulator can obtain quasi- velocity-matching at special frequency and make the modulation index increase proportionally to the interaction length. As an experiment, we use a 1.06 micrometer laser as a light source and a modulating microwave source at 6 GHz (16 W). We can expect that we will get at least 3.0 rads of modulation index.
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