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146 Chapter 6

Not Everyone Is Convinced

Despite the momentum built by MEMS technology by Nortel and
Lucent, MEMS has not won over everyone. MEMS is a viable tech-
nology and a good way to do a scalable switch solution. However,
early implementations of MEMS-based switches were very lossy
when passing a signal through a WDM system, through an optical
switch, and through a DWDM system.

Agilent Does Optical Switching

Differently
TEAMFLY

Optical cross-connects (OXCs) will be used to route wavelengths
between inputs and outputs while adding and dropping local traffic.
Many carriers expect to need nodes with several thousand input and
output wavelengths within a few years.When considering this entire
scenario, 25 fibers times 160 wavelengths per fiber implies a 4,000
4,000 OXC.
From an engineer’s standpoint, the most flexible architecture is
the opaque wavelength interchange cross-connect (WIXC) shown in
Figure 6-13. In the WIXC, all wavelengths are received and retrans-
mitted at the cross-connect by transponders at each port. In this
architecture, any wavelength can be switched to any other wave-
length on any fiber through transponder wavelength conversion.
However, long-haul transmitter and receiver costs at these nodes for
10- and 40-Gbps data rates may be considerable.

Single Big Fabric or Multiple Smaller
Fabrics?

Ultra-long-haul transmission systems will enable unregenerated
transmission over very long distances and thus the possibility of
transparent cross-connects that eliminate expensive OEO conver-
sions. Eliminating transponders does away with wavelength conver-

®
Team-Fly