544
13 Fiber Optic Communication Networks
Fig. 13.28 Optical cross-connect architecture using optical space switches and no wavelength
converters
mesh networks that are interconnected through many hundreds of optical fibers, each
carrying dozens of wavelength channels. At such a junction an OXC can dynamically
route, set up, and take down very high-capacity lightpaths [28, 29].
To visualize the operations of an OXC, consider first the OXC architecture shown
in Fig. 13.28 that uses a switching matrix for directing the incoming wavelengths
that arrive on a series of M input fibers. The switch matrix can operate electrically
or optically; that is, it can switch the incoming signals in either the electric or the
optical domain. Each of the M input fibers carries N wavelengths, any or all of which
could be added or dropped at a node. For illustration simplicity, here assume M =
2 and N = 4. At each fiber input, the arriving aggregate of N signal wavelengths
is demultiplexed and then enters the switch matrix. The switch matrix directs the
channels either to one of the eight output lines if it is a through-traveling signal, or
to a particular receiver attached to the OXC at output ports 9 through 12 if it has
to be dropped to a user at that node. Signals that are generated locally by a user
get connected electrically via the digital crossconnect matrix (DXC) to an optical
transmitter. From here the wavelengths enter the switch matrix, which directs them to
the appropriate output line. The M output lines, each carrying separate wavelengths,
are fed into a wavelength multiplexer to form a single aggregate output stream.
An optical amplifier to boost the signal level for transmission over the trunk fiber
normally follows the multiplexer.
13 Fiber Optic Communication Networks
Fig. 13.28 Optical cross-connect architecture using optical space switches and no wavelength
converters
mesh networks that are interconnected through many hundreds of optical fibers, each
carrying dozens of wavelength channels. At such a junction an OXC can dynamically
route, set up, and take down very high-capacity lightpaths [28, 29].
To visualize the operations of an OXC, consider first the OXC architecture shown
in Fig. 13.28 that uses a switching matrix for directing the incoming wavelengths
that arrive on a series of M input fibers. The switch matrix can operate electrically
or optically; that is, it can switch the incoming signals in either the electric or the
optical domain. Each of the M input fibers carries N wavelengths, any or all of which
could be added or dropped at a node. For illustration simplicity, here assume M =
2 and N = 4. At each fiber input, the arriving aggregate of N signal wavelengths
is demultiplexed and then enters the switch matrix. The switch matrix directs the
channels either to one of the eight output lines if it is a through-traveling signal, or
to a particular receiver attached to the OXC at output ports 9 through 12 if it has
to be dropped to a user at that node. Signals that are generated locally by a user
get connected electrically via the digital crossconnect matrix (DXC) to an optical
transmitter. From here the wavelengths enter the switch matrix, which directs them to
the appropriate output line. The M output lines, each carrying separate wavelengths,
are fed into a wavelength multiplexer to form a single aggregate output stream.
An optical amplifier to boost the signal level for transmission over the trunk fiber
normally follows the multiplexer.