Research On Key Techniques In Optical Packet Switching Networks

The exponential growth of Internet traffic will require high capacity networks capable of efficiently routing various types of data format packets.Optical packet switching networks are expected to provide the required capacity and flexibility for high-speed networks, and thus become one of the major research areas in optical communication systems.Two of the key techniques in OSP network:all-optical packet clock recovery and 1×N optical packet switching node are investigated in this thesis.In the researches of optical packet clock recovery, we propose a packet clock extractor, which comprises a Fabry-Perot (F-P) filter and a Semiconductor optical amplifier (SOA).Low Finesse F-P filter is used to directly extract the packet clock from the data stream which ensures that the clock locks fast and vanishes quickly. The clock, amplitude modulated as a result of low-Q filter, then goes into SOA to reduce the low-frequency amplitude noises.The effect of the finesse of the F-P filter, the self-gain-modulation (SGM) and self-phase-modulation (SPM) effect of SOA on the locking and unlocking time of the packet clock is theoretically analyzedWe demonstrate instantaneous 10GHz and 40GHz packet clock extraction experimentally with low time jitter, short locking and unlocking time.We also propose a novel technique to fasten the unlocking time of the packet clock using the SPM effect of SOA. We obtain packet clock with locking time of 200ps and unlocking time of 600ps,which is the fastest as far as we know. Moreover, a multi-rate all-optical packet clock recovery is demonstrate with two polarization interferometers (PIs),which provides a low cost choice in multi-rate optical networks.In the researches of 1×N optical packet switch, we demonstrate two kinds of switches. First, we propose an optical packet switch employing in-band labeling, norrow bandwidth fiber Bragg gratings (FBGs) as label extractor, simple electronic combinatory network as label processor and LiNbO3 gates in broad-and-select configuration as switching matrix.Experimental results shows the effectivity of the in-band labeling as well as the transparent routing of packets with multiple data formats and data bit-rate.Several high speed data streams with diffirent data formats and data bit-rate, including 160 Gb/s RZ OOK packets,320 Gb/s multi-wavelength NRZ packes,120Gb/s multi-wavelength DPSK packets and 480Gb/s multi-wavelength OFDM packets, are dynamically routed without the need to reconfigure the label processor and the switch. We also show in the experiment the cascadibility of our optical packet switch. In summary, the optical packet switch is demonstrated to be high speed, with large capacity, transparent in term of modulation format and bit-rate, scalible, with low lantency and low power comsumption.Another kind of optical packet switch is build with photonic integrated switch matrix based on arrayed phase shifters.Unlike cascaded devices,the phased-array switch enables 1×N switching using a single phase modulation stage, thus offers potential advantages in terms of size and optical insertion loss for large N.We show error-free operation with maximum penalties of 0.7 dB for 160 Gb/s RZ-OOK and 0.6 dB for 120 Gb/s multi-wavelength DPSK packets.