OXC based on fast digitally tunable optical filters for OBS networks

Abstract

Summary form only given. In optical burst switching (OBS) networks, a short switching time is very important for handling fine grain packets such as TCP ACK packets, which are only 40 bytes in length. At data rate of 10 Gbps, such a data burst will occupy a period of only 32 ns. Therefore OXC (optical cross connector) with fast switching speed, for example < 100 ns, are generally required for OBS networks. There are many methods to configure an OXC. Tunable optical filters may used to build large scale OXC. In an optical filter, the tuning ability is usually achieved by introducing extra phase shift via the electro optic, thermo optic, or piezoelectric effect, etc. Up to date, the most commonly used tunable filter structures are interferometric such as Fabry-Perot (FP) and Mach-Zehnder (MZ) interferometers. They are usually poor in the performance of passband flatness and the crosstalk, and require robust electronics to stabilize the central wavelength. Hence, they are rarely practically used as switching elements in the dense wavelength division multiplexing (DWDM) optical networks. In recent years, digitally tunable optical filter (DTOF) has received increasingly attention. Structures based on the arrayed waveguide grating (AWG) and on-off switches have been reported. DTOF based on AWG may require precision thermal control for AWG usually suffers the problem of temperature dependence. In this talk, we present a novel approach to realize the DTOF (digitally tunable optical filter) based on DWDM thin film filters (TTF) and semiconductor optical amplifier (SOA). Apart from the outstanding feature being consistent with the wavelength comb suggested by international telecommunication union-telecommunication (ITU-T), the proposed DTOF is very stable in temperature performance. Furthermore it requires less SOAs in comparison with the reported structures.