Photonic Network Communications, 8:2, 209±221, 2004
# 2004 Kluwer Academic Publishers.Manufactured in The Netherlands.
Design of Translucent Optical Networks: Partitioning and Restoration
Department of Electrical and Electronics Engineering, Bilkent University, TR-06800 Ankara, Turkey
Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, CA 92093-0407, USA
Received July 24, 2003; Accepted November 7, 2003
Abstract. We discuss the problem of designing translucent optical networks composed of restorable, transparent subnetworks interconnected
via transponders.We develop an integer linear programming (ILP) formulation for partitioning an optical network topology into subnetworks,
where the subnetworks are determined subject to the constraints that each subnetwork satis®es size limitations, and it is two-connected.A
greedy heuristic partitioning algorithm is proposed for planar network topologies.
We use section restoration for translucent networks where failed connections are rerouted within the subnetwork which contains the failed
link.The network design problem of determining working and restoration capacities with section restoration is formulated as an ILP problem.
Numerical results show that ®ber costs with section restoration are close to those with path restoration for mesh topologies used in this study.It
is also shown that the number of transponders with the translucent network architecture is substantially reduced compared to opaque networks.
Keywords: translucent optical networks, subnetwork partitioning, section restoration
Multiwavelength optical networks are currently
widely deployed in long-distance core networks.
There are several architectures suitable for optical
networks, each involving complex combinations of
optical and electronic devices.All these architectures
have the optical ®ber as the transmission medium and
contain some form of optical cross-connects (OXC)
interconnecting these ®bers.
In transparent or all-optical networks architecture, a
connection goes through the network over a com-
pletely optical path [1,2].This path consists of point-
to-point optical links interconnected by all-optical
nodes.Wavelength selective cross-connects (WSXC)
can switch an incoming connection on some wave-
length onto the same wavelength in any of its outgoing
®bers.In transparent networks utilizing WSXCs,
connections must satisfy the wavelength continuity
constraint, that is, a connection must remain on the
same wavelength on all links along its path.On the
other hand, wavelength interchanging cross-connects
(WIXC) employ optical wavelength conversion in
order to switch an incoming connection onto any
wavelength in any outgoing ®ber.As such, they enable
more ef®cient packing of wavelengths onto the ®bers
by eliminating wavelength con¯icts.Optical wave-
length converter technologies have relatively high
costs, making WIXCs signi®cantly more expensive
compared to WSXCs .Performance of all-optical
networks with and without wavelength converters
have been studied extensively in the literature [4±6].
A second type of optical networks is the opaque
network architecture .In opaque networks, a
connection passes through optical/electronic/optical
converters, called transponders, at each node.Opaque
networks may utilize optical or electronic form of
switching at intermediate nodes.Optical networks
that are deployed today are typically opaque, and they
use electronic cross-connects (EXC) .
One of the main advantages of all-optical net-
works is transparency.There are various levels of