Qingji Zeng

A new optimal algorithm for multipump sources of distributed fiber Raman amplifier

The most important feature of the Raman-gain spectrum is that the peak-gain wavelength only depends on the pump wavelength (fixed shift about 100 nm). Using this feature, a new optimal algorithm for multipump sources of a distributed fiber Raman amplifier is designed. The numerical analysis results show that the optimal algorithm is simple and effective.

Numerical analysis of concentration quenching model of Er/sup 3+/-doped phosphate fiber amplifier

Based on the homogenous model and inhomogeneous model of concentration quenching of erbium-doped fiber amplifier with high doping concentration, the rate equation and power evolution equation of erbium-doped phosphate fiber are solved numerically and analyzed. The dependence of the calculated gain and noise figure on pump power is compared with experimental data, and the results indicate that the combined model of the two models is in good agreement with experimental data. The relative number of clusters in erbium-doped phosphate fibers is estimated from the numerical analysis, and the optimal doping concentration and length of erbium-doped phosphate fibers are proposed in this paper. By numerical analysis, the results show that with 200-mW/980-nm pump power, an erbium-doped phosphate fiber amplifier with a doping concentration of 4.0/spl times/10/sup 26/ ion/m/sup 3/ and length of 10 cm may reach 27.0-dB gain.

Differentiated integrated QoS control in the optical Internet

In order to facilitate convergence of networks and services, this article investigates a new hybrid and integrated QoS control scheme that combines electrical IP layer features with reconfigurable optical layer, and addresses cross-layer design on QoS control in optical Internet (i.e., IP/WDM networks). The proposed integrated QoS control scheme can not only provide appropriate transport service for various types of traffic relating to different service categories in a cost-effective way, but also maintain high flexibility/scalability for integrated services provisioning, which seems to be preferred for QoS provisioning in the next-generation multiservice integrated optical Internet.

Dynamic Survivability in WDM Mesh Networks Under Dynamic Traffic

Network survivability is a crucial requirement in WDM mesh networks. In this paper, we systematically consider the problem of dynamic survivability with dynamic single link failure in WDM networks under dynamic traffic demands. Specifically, we investigate various protection schemes, such as dedicated path protection (DPP), shared path protection (SPP), dedicated link protection (DLP), shared link protection (SLP), and two restoration schemes, path restoration (PR) and link restoration (LR). Moreover, two new shared protection methods are proposed, i.e., SRLG-based shared link protection (SRLG-SLP) and SRLG-based shared path protection (SRLG-SPP). The SRLG (shared risk link group) constraint defines the availability of protection resources to a working path, which requires that any two working paths sharing the same risk of failure (or in the same SRLG) cannot share the same protection resources. Furthermore, in our study, we consider a more practical dynamic single-link failure model, in which the link-failure-interarrival time and link-failure-holding time are considered as two independent parameters. Based on this link-failure model, extensive simulations are done to analyze and compare the dynamic survivable performance of various protection and restoration schemes. Resource utilization, protection efficiency, restoration efficiency, and service disruption ratio are employed as survivable performance metrics versus traffic load, link-failure frequency, and link-failure reparation time to evaluate the survivable performance. Many meaningful results are given. In addition, we show that the developed SRLG-SLP and SRLG-SPP protection schemes perform very well in terms of protection efficiency and service disruption ratio, while sacrificing some performance in terms of resource utilization.

Improved gain performance of high concentration Er/sup 3+/-Yb/sup 3+/-codoped phosphate fiber amplifier

The rate equations and power evolution equations of erbium/ytterbium codoped phosphate fiber amplifiers are solved numerically and its results are compared with measured data in literature. Based on the numerical analysis, optimal erbium and ytterbium codoping concentrations are supposed, and with a pump power of 224 mW and a fiber length of 3.6 cm, the internal gain of 31.0 dB and gain per unit length of 8.6 dB/cm may be achieved in the fiber with the optimal codoping concentrations.

Multi-Layer Differentiated Integrated Survivability for Optical Internet

In this paper, we study the problem of multi-layer integrated survivability (MLIS) for efficiently provisioning reliable traffic connections of arbitrary bandwidth granularities in the integrated optical Internet. We decompose the MLIS problem into three sub-problems: survivable strategies design (SSD), spare capacity dimensioning (SCD), and dynamic survivable routing (DSR). First, a review of network survivability in multi-layer IP/WDM networks is provided. Then, multi-layer survivability strategies are proposed and it is observed how these strategies could be applied to the integrated optical Internet architecture. We also present an enhanced integrated shared pool (ISP) method for solving the static MLIS problem (i.e., the SCD sub-problem) and the priority-based integer programming formulations are also given. Moreover, we design a novel scheme called the differentiated integrated survivability algorithm (DISA) to solve the dynamic MLIS problem (i.e., the DSR sub-problem), which employs flexible survivable routing strategies according to the priority of the traffic resilience request. Performance simulation results of DISA show that our adaptive survival schemes perform much better in terms of traffic blocking ratio, spare resource requirement, and average traffic recovery ratio compared with other solutions in the optical Internet.

The impacts of burst assembly on the traffic properties in optical burst switching networks

Optical burst switching (OBS) is regarded as one of the most promising solutions for the next generation backbone. Burst assembly in the edge nodes is an important issue to be addressed in OBS networks. In this paper, the impacts of burst assembly using different schemes on the Poisson traffic properties are investigated and simulated. The results are shown that the intervals of assembled burst arrivals are short dominant, but their service time distributions are much different from each other due to different assembly schemes. When the timer-based scheme is used, a normal-like distribution is obtained, while a long dominant one is obtained when threshold-based scheme is adopted. In addition, the product of the traffic load and time rate keeps invariable in both cases.

GMPLS-based hierarchical optical routing switching architecture

With the development of Generalized Multi-Protocol Label Switching (GMPLS: an optical extension to traditional Multi-Protocol Label Switching) by IETF, we envision that todays static optical networks will evolve towards dynamic optical networks with a intelligent, flexible and scalable control plane software. In this paper we firstly describes a novel IP-Centric optical network architecture called Hierarchical Optical Routing Switching Architecture (HORSA) based on GMPLS--a flexible, highly scalable IP over WDM optical network architecture for the delivery of public network IP services. Two kinds of node including Optical Core Router (OCR) and Optical Edge Router (OER) are involved in this optical network architecture. In this section we also discuss some issues such as routing, signaling and management of HORSA. Secondly, we mainly focus on the design issues of OCR and OER including multi-granularity switching fabrics, intelligent OTU, control plane software and etc. Finally, we reach conclusions that HORSA based on GMPLS is suitable for current hybrid network environment and optimistic for IP traffic transfer, it can be scaled to pure optical IP over WDM architecture based on Optical Packet Switch (OPS).

Improved gain characteristics of high concentration erbium-doped phosphate fiber amplifier

Both cooperative up-conversion and pair-induced concentration quenching of erbium-doped phosphate fiber with high doping concentration are considered for the first time in this letter. The dependence of the calculated gain on pump power is compared with measured data, and the results show that ion pair may exist in erbium-doped phosphate fiber with doping concentration of 3.8/spl times/10/sup 26/ ion/m/sup 3/. For several erbium-doped phosphate fibers with different lengths, improved gain may be obtained with higher doping concentration.

High-Performance Hybrid-Switching Optical Router for IP over WDM Integration

Because pure electrical routers with their bandwidth limitations can hardly keep up with the tremendous traffic growth in the Internet, optical routers based on various optical switching techniques including optical wavelength switching (OWS), optical burst switching (OBS), and optical packet switching (OPS) have been suggested to cope with this problem. However, because OBS and OPS are both in their early experimental phase and OWS only provides coarse granularity switching, a hybrid-switching optical router with combined OWS and electrical packet switching is a necessity in order to accommodate the entire multi-granularity traffic with multi-service requirements in a cost-effective manner. Its coordination capability of optical circuit switching and electrical packet switching enables efficient/intelligent usage of network resources. In this paper, we first review research and developments of such IP routers employing optical switching/interconnection techniques and examine how these techniques can be used inside routers to scale node capacity and to improve optical Internet performance. We also present and study the performance of a terabit optical router with an optical-electrical hybrid-switching fabric. The node architecture is based on the idea of IP over WDM integration with Generalized Multi-Protocol Label Switching (GMPLS). The network-level performance evaluations show that the proposed hybrid-switching optical router is a cost-effective solution for building the next generation GMPLS-based multi-granularity optical Internet.