About the WDM model
The for WDM uses object classes that represent each type of element to populate the
VMware Smart Assurance
repository
that models the topology of the WDM network being managed. This, in turn, is used to build the codebook, which is the basis for root-cause analysis. The for WDM also uses the
relationships in the topology to calculate the impact that a root-cause problem in one element has on the elements and services that are connected to, or depend on it. The model for WDM is more granular than that for
SONET/SDH because there are fiber connections inside devices that are potential failure points and must therefore be part of the model.
As an example of what needs to be modeled in a WDM device, Schematic of
a terminal end amplifier is a schematic of a WDM Transmit End Terminal device. This illustrates how the various
components are connected together to take a number of incoming SONET/SDH services, convert them each to a WDM signal on a wavelength, and then combine the wavelengths onto a single fiber.
Schematic of
a terminal end amplifier

Each incoming client signal is converted
to an
Optical Channel (OCH)
, which carries the signal on a specific wavelength and adds a WDM header. A number of wavelengths are combined into a single fiber using a Multiplexer
. Due to physical limitations, several stages
of multiplexing are required to, for instance, combine 160 wavelengths onto a single fiber. In the example shown, 80 wavelengths in the C-band are combined in two stages of multiplexing, and are then combined with 80 other wavelengths in the L-band.
The Optical Supervisory Channel (OSC),
which carries management information on an additional wavelength, is added in the optical amplifier that is in each band’s path in front of the Band Multiplexer
.A WDM Receive
End Terminal performs the reverse function in a similar arrangement. Other functions, such as in-line amplifiers and back-to-back amplifiers are made up of combinations of similar components.