Priority-based alternate routing (PAR) and dynamic priority-based alternate routing (DPAR) are introduced for multiple classes of traffic in intelligent optical networks. A discrete event simulation platform was implemented to compare the performance of different priority schemes. As usual, the call interarrival and holding time for each class of traffic were assumed to be exponentially distributed in the simulation. The results show that PAR can significantly decrease the blocking probability of optical networks, especially for traffic with low priority. Because the weights of links of the network in DPAR increase with the increment of wavelength occupation, links with more idle wavelengths are more easily chosen as part of the shortest path. This mechanism benefits to the load balance of the network and as a result, DPAR has better performance than PAR. In order to utilize the advantage of the wavelength reservation-based priority scheme (RES), which provides low blocking for traffic with high priority, the combination of DPAR and RES was also investigated. The simulation results show that DPAR with the proper RES provides the lowest blocking probability for every class of service compared to the corresponding class of other priority schemes.
Blocking probability is one of the key factors to evaluate the routing and wavelength algorithms for intelligent optical network. Two kinds of Dynamic K-Shortest Path (DKSP) Algorithms were designed. One is based on Linear Link Weight Function (LW) and the other is based on Piecewise Linear Link Weight Function (PLW). It was found that the two kinds of DKSP can significantly decrease the blocking probability of optical network comparing to the static KSP for the same number of alternate routes. Compared to routing with LW, the coefficient of PLW has larger effect on the blocking probability of optical network when the number of alternate route is small, but the effect is weakened with the increase of the number of alternate route. As far as the two kinds of DKSP algorithms are concerned, DKSP with PLW has some advantage over DKSP with LW on decreasing the blocking probability. It was also found that the optimized performance can almost be got by DKSP with only 2~4 alternate routes for NSFNET.
With the drastic increasing of data traffic, the optical transport network will be adjusted to be services-oriented networks. Its traffic engineering system should be able to dynamically react to traffic changes while at the same time fulfilling QoS requirements for different classes of service. So the next generation optical network will handle priority, preemption mechanisms, and traffic rerouting in order to concurrently accommodate the largest amount of traffic. At the same time, transport networks need to evolve so as to drastically reduce both deployment costs and operating expenses. One of a reasonable strategy to achieve the goals is to simplify the network architecture by reducing the number of layers. GMPLS protocols enable the coordination between the IP and the optical layers and provide classified services. The collaboration of both layers in the routing process leads to optimization of network performance. Simulation results show the results of different strategy for resource allocation.
Thin Film Filters (TFFs) are minimum phase filters, and the Hilbert Transform law is related to the relationship between a TFF's amplitude and phase response. It should be possible to obtain the phase response from the amplitude response by this law, but the Cauchy Integral is too complex to calculate the phase response directly. In this paper, a method to reconstruct the phase response from the amplitude response was proposed, and then the group velocity delay and the chromatic dispersion of a TFF could also be obtained just by simple calculations. An experimental setup based on the RF modulation was designed. The test results were in good agreement with the theoretical value within passband, as determined by contrast analysis, and the validity of the method was proven. In addition, the dispersion characteristic of TFFs was also analyzed.
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