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Figure 9. Mean packet delay in multi-passive-combiner hub and AWG hub.(a) Uniform traffic. (b)
Non-uniform traffic (
f
=2). (c) Non-uniform traffic (
f
=5, i.e., traffic is more non-uniform than that in
Figure. 9(b)).
f
=
. For non-
uniform traffic, the AWH hub has longer mean delay because of its inherent uniform channel
allocation within the hub, while the multi-passive-combiner hub has smaller mean delay
(which does not exceed the given requirement
2
Figure 9(b) shows the mean packet delay under non-uniform traffic at
*
Delay
=
) because it can have non-
uniform channel assignment to fit the non-uniform traffic pattern. Figure 9(c) shows that
when the traffic is more non-uniform with
2s
f
=
, the multi-passive-combiner hub has even
better performance than the AWG hub. These results show that the multi-passive-combiner
hub is more effective when the traffic load is heavy or the traffic pattern is non-uniform.
5
C
ONCLUSION
We described our recent design of multi-passive-combiner hubs for metro WDM
networks. A multi-passive-combiner hub is only composed of passive optical components
(namely, passive combiners and demultiplexers) and it assigns wavelength channels to the
input-output pairs based on the traffic load and patterns while avoiding wavelength conflict.
As a result, the multi-passive-combiner hub offers three major advantages: i) it has low cost
and high reliability because it only uses passive optical components, ii) it can efficiently
transport non-uniform metro traffic via non-uniform channel assignment within the hub, and
iii) it can easily be scaled up to provide more channels for the ever-increasing traffic load.
R
EFERENCES
[1]
Y. W. Leung, “Multipassive-star-coupler hub for metro WDM networks,”
IEEE
Photonic Technology Letters,
vol. 18, no. 15, pp. 1621-1623, August 2006.
[2]
Y. W. Leung, “Channel assignment for a metro hub under nonuniform traffic,”
IEEE
Photonic Technology Letters,
vol. 20, no. 21, pp. 1787-1789, November 2008.
