The routing and spectrum assignment (RSA) is one of the key problems in flexible optical networks. When in a gridless
fashion, the shortest-path RSA algorithms have exponential computational complexity, and are thus not suitable to be
employed in real networks. On the other hand, today most optical components cannot support fully gridless tunability,
which also limits the application of gridless RSA schemes. In this paper, we propose a novel grid-based spectrum-scan
routing (SSR) scheme in flexible optical networks. The SSR scheme achieves optimal routing with a polynomial
computational complexity. Compared with other RSA schemes, SSR has shorter computation time, lower blocking
probability, and higher resource utilization.
Bandwidth-variable (BV) optical networks have obvious advantages to provide spectrum-efficient transportation.
Previous research showed that the BV-supported adaptive routing (AR-BV) had lower blocking probability than the
BV-supported fixed routing (FR-BV), when signaling blocking is not considered. In order to study the overall blocking
probability, we propose a BV extension to RSVP-TE signaling protocol, and implement it on our large-scale ASON
test-bed. Results show that due to the flooding process, AR-BV has a higher signaling blocking probability compared
with the FR-BV, especially in a highly dynamic network scenario, and this weakens its advantage in overall blocking
We discuss the influence of the seams between the liquid crystal pixels on the signals that transmits through the LCoSbased
switching node in the elastic optical path network. It is found that the seams will bring repetitions of the signal in
time domain. Also, the spacing and amplitudes of these repetitions are determined respectively by the spectral spacing
and the shapes of the frequency slots implemented by the liquid crystal pixels. By simulating with an LCoS-based
switching node model, we propose a feasible approach to reduce this influence.
In this study, we investigate the dynamic connection provisioning problem in mixed-line-rate (MLR) optical networks.
Fast heuristic algorithms are proposed for both fixed and tunable node architectures. Results show that our algorithm can
significantly reduce the blocking probability and save the transceivers under tunable node architecture.
We propose a concurrent collision avoidance scheme based on wavelength rotation (WR) in optical WDM networks. By
introducing wavelength cost during the path computation process, the proposed scheme can significantly reduce the
concurrent blocking probability (BP), without introducing additional connection setup delay compared with the time-threshold-
based concurrent RWA schemes.
This paper proposes an inter-domain routing algorithm for multi-domain WDM networks based on hierarchical PCE
architecture. The proposed algorithm presents a strategy of selecting k random paths in parent PCE. The simulation
indicates that the proposed algorithm outperforms previous methods in term of blocking probability and resource
We propose an improved postponed lightpath teardown (PLT) strategy by introducing a lightpath splitting mechanism in
multi-layer optical networks. Based on the original PLT strategies, this paper introduces a mechanism to split the
unoccupied shortest lightpaths into shorter ones when the network operates in a steady state. Results show that the
improved strategy achieves higher utilizations of both wavelength-links and transceivers under different scenarios of
load and transceiver number, and significantly reduce the blocking probability (CBP).
A Postponement strategy for short lightpath teardown in wavelength-routed WDM mesh networks under dynamic traffic is proposed for the first time. This strategy postpones the teardown process of the short lightpaths when there is no traffic on them. In this way, the average hop number of lightpaths will be reduced and thus more lightpaths may be set up to reduce the overall blocking probability. Moreover, since the proposed strategy extends the average holding time of lightpaths, it can help reduce the signaling flow in the optical control plane. Continuous-time system (CTS) simulation shows that the strategy is capable of reducing the overall blocking probability and the signaling flow in the optical control plane.
Our proposed soft preemptive scheme was demonstrated highly effective at reducing the blocking probability and meanwhile guaranteeing the existing traffics' quality of service in wavelength-routed networks. In this paper, we focus our study on combining Soft Preemption and Wavelength Conversion. The performance analysis shows that the introduction of Wavelength Conversion can help enhance the advantages of Soft Preemption in reducing blocking and improving other performance metrics.
In this paper, a soft preemptive scheme for providing service differentiation in wavelength-routed networks is proposed and it is shown that the scheme is capable of reducing the call blocking probability of high-priority connections while keeping low-priority connections unaffected.