Study On Several Key Technologies In Nodes For Asynchronous Optical Packet Switch

As the widespread use of the Internet and broadband WDM technology realization, the network bottleneck is shifting from transporting layer to switching layer. Especially assuming that transmission line rates will continue to increase beyond 10Gb/s, optical switch techniques are expected to assist in releasing the network from undesirable latencies related to O/E/O conversions at the switching nodes. In order to switch the all-optical packet, transmit packets from source to destination all-optically, it is crucial to transmit and switch the packets in the all-optical domain from source to destination.Optical packet is the smallest switching granularity for asynchronous optical packet switching (AOPS) network. AOPS is the new generation of all-optical switching network fulfilling the diverse service application, which bandwidth is assigned agilely according to the user's actual need with high bandwidth utility and supporting multi-granularities data service. But there have many technical difficult problem needing to solution for realizing the OPS technology, such as optical packet contention resolution, the scheduling strategy and algorithm for the AOPS node, optical header processing, optical packet assembling mechanism, etc. The other key technology for realizing AOPS include the all-optical logical devices realization, optical packet routing algorithm, optical packet coding scheme, optical channel protection and resumption mechanism, etc.Based on the above analysis, this dissertation mainly covers the following topics'research: optical packet service bursty features; optical packet contention resolution; optical channel scheduling strategy; optical header extraction in the optical domain.1) Considering the IP traffic is bursty and self-similar, we analyzied its performance influence establishing service description model and theoretic analysis mode for asynchronous OPS network. Then, how the three typical optical packets length distribution influence on the OPS performance is studied in the chapter 2 also. The results show that the OPS edge node need to reshape the service flow to make the service with low bursty coefficient entering the OPS core node and to achieve the optimal packet loss ratio (PLR) performance.2) The features of conventional FDL feedback buffering resolution are analyzed in the chapter 3. Considering the probability of asynchronous OPS packet conflicting is larger, the concept of FDL buffering virtual occupation and switch buffer are studied. The approximate expressions for OPS PLR performance are derivated under shared feedback FDL buffering configuration and wavelength converter with shared feedback FDL buffering configuration respectively. The contention resolution which FDL is used as primary buffer and electronical RAM is used as supplementary buffer and photoelectric hybrid First-Fit-Void-Filling (FF-VF) channel scheduling algorithm are put forward for the first time in chapeter 3.3) There have much TCP and UDP data having the strict transmission delay restriction in the IP service network. The OPS node performance with input queue worked on the virtual output queue is studied in the chapter 4. The realization way and flow of difference long length packet and short length packet is proposed in this chapter. The OPS node structure with long length packet and short length packet queue respectively is designed. A simple, effective, flexible and with low time complexity algorithm, namely preemptive short packet first (PSPF) scheduling is proposed for the OPS node. The algorithm stipulates the short packet have the hightest scheduling priority and the scheduler scheduling the short packet first through fair and foul, even if the long length packets are transmitting, the short length packets can preempt the long packet transmission time.4) The concept of packet FDL sorting is researched in the chapter 5. Due to the packet buffer sorting resolving the FDL internal contention and increasing the delay restriction, the probability of packets scheduling success is large. So, three packet buffer sorting schemes are studied. All-sorting shortest packet first (ASPF) scheme let the shortest packet occupy the shortest FDL with higest calculation complexity; Weak-sorted shorter packet first (WSPF) scheme let the shorter packet occupy the shortest FDL with the lesser complexity by only compareing W wavelength channel delay for one input fiber. The third packet buffer sorting scheme is partial-sorted longer packet first (PLPF) which let longer packet occupy first the shortest FDL. The packet buffer sorting imporves the OPS performance at the cost of system calculation complexity. The study result indicates that the performance of 10 percent packets buffer sorting correspond to the performance of 100 percent packets buffer sorting. Therefore, the scheme, which utilizes a small quantitiy of short packet buffer sorting and other packets with first-come-first-serve buffer management using limited number of FDL, can achieve perfect PLR performance.5) The feature of SOA and delay interferometer is analzied in the chapter 6. A novel all-optical packet header extraction scheme and structure based on SOA and improved tiny adjustable D-I interferometer is studied. By setting parameter suitably, such as header bit time interval, payload bit time interval, SOA carrier life time, guarantee time between header and payload, the scheme can achieve more than 15dB contrast ratio for the optical packet header extraction when the rates of header and payload are 2.5Gb/s and 40Gb/s respectively. The parameters of improved SOA and delay interferometer are analyzed and studied to optimize the performance of optical packet header extraction with the proposed scheme. In addition, the system structure is simple, highly scalable and photonic integration.