High speed all-optical packet switching router employing single and multiple PPM based routing tables

Chiang, Ming-Feng (2009) High speed all-optical packet switching router employing single and multiple PPM based routing tables. Doctoral thesis, Northumbria University.

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Abstract

All-optical packet switched networks with flexibility and capability to deal with the bursty traffic is one solution to deal with the ever increasing demand for bandwidth. To fully utilise the potential of such networks and to ensure that high-speed packets, passed through a number of nodes, are faithfully delivered to their intended destination with minimum delay times, packet header processing and routing decision needs to be carried out in the optical domain not in the electrical domain. This is to avoid the speed bottleneck imposed by the slow response of currently available electronic devices beyond 40 Gb/s. At present, packet header recognition is carried out by sequentially correlating the incoming packet header address with every entry of a local routing table. For a small size network, with a reasonable size routing table, sequential correlation is viable both in terms of processing speed and implementation complexity. However, for a large size network with a very large size routing table of hundreds or thousands of entries, the cost, complexity and processing time does become a real issue. The latter will lead to a noticeable increase in the packet processing time at every router, which could be significantly reduced by a non- conventional signal formatting. In this thesis, an all-optical 3-input AND gate and an all-optical 1 x2 switch with high contrast ratio are proposed as an essential element in all-optical routers. New routing schemes employing pulse position modulation (PPM) packet header format as well as single and multiple PPM based routing tables (PPRTs) are proposed and investigated. The main advantage of the proposed scheme is reduced size routing table leading to a faster router processing time compared to the routers with conventional routing tables (CRTs). The correlation-time gains offered by the proposed schemes are given by theoretical calculations. For optical packets with 4-bit binary address, all-optical 1x3 routers employing single and multiple PPRTs with an entry slot of 6.25 ps offer — 100 and — 400 times faster processing times when compared to the routers employing CRT, respectively. The performance of the proposed routers employing single and multiple PPRTs are assessed in terms of optical signal-to-noise ratio (OSNR) in multi-hop routing by means of numerical simulations and theoretical analysis. It is shown that predicted and simulated OSNR decreases by —2 dB after each hop. New packet header address formats proposed offers reduced complexity of nodes by employing single or multiple PPM based routing tables. Adopting a hybrid header address format, it is shown that routers with multiple PPRTs can operate at 160 Gb/s with the output intra-channel crosstalk of -18 dB and with output packet power fluctuation of 2 dB. Finally, a WDM router employing a single PPRT, capable of processing packets at different wavelengths simultaneously, is proposed and its inter-channel crosstalk performance is investigated. At 160 Gb/s, results obtained show an inter-channel crosstalk of — -27 dB at a channel spacing of greater than 0.4 THz and a demultiplexer bandwidth of 500 GHz.

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