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Potential Low Cost Optical Waveguide Routing Switch

IP.com Disclosure Number: IPCOM000104797D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 112K

Publishing Venue

IBM

Related People

Ramaswami, R: AUTHOR [+2]

Abstract

Proposed is a low-cost optical switch for application in a wavelength routing network. The switch consists of wave-length demultiplexers, electronic switches and laser array with laser elements emitting multiple wavelengths.

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Potential Low Cost Optical Waveguide Routing Switch

       Proposed is a low-cost optical switch for application in a
wavelength routing network.  The switch consists of wave-length
demultiplexers, electronic switches and laser array with laser
elements emitting multiple wavelengths.

      Recently, wavelength routing has been proposed as a means for
obtaining very high-capacity (terabits/second) wide-area optical
networks (see [1]  for a tutorial overview).  Such a network consists
of many wavelength-routing nodes interconnected by point-to-point
fiber-optic links.  Each node has a few input ports and a few output
ports.  Each input port receives data at several optical wavelengths.
The node must be able to route a data stream at a certain wavelength
at an input port to any output port, independent of the other
wavelengths.  Such a node is called a wavelength routing switch.

      Two methods of implementing such a switch have been proposed.
Figure 1 shows one implementation of a 3-port, 2-wavelength switch.
In general, suppose the switch has Delta input ports and M
wavelengths per port.  Each input port is connected to a wavelength
demultiplexer that separates the wavelengths.  Wavelength lambda sub
i from each port is then sent to a Delta % X % Delta optical switch.
Each output of a switch is connected to a different wavelength
multiplexer.  The wavelength multiplexer combines the signals at
different wavelengths on each of its input ports into a single output
port.  However, this wavelength routing switch if built out of
discrete components is very expensive.  Moreover optical switches are
generally lossy and polarization dependent and building large
switches is difficult.

      The second approach [2]  uses tunable acoustooptic filters.  An
acoustooptic filter is a two input, two output, device and serves
directly as a wavelength routing switch.  However the number of
wavelengths it can switch is very limited, typically 2 or 3, and it
is also a very expensive device to fabricate.  Moreover many filters
must be cascaded in order to build larger switches.

      We first describe a switch with two input ports and two output
ports.  (This can easily be seen to work with an arbitrary number of
ports.)  There are thus two input fibers and two output fibers, each
of which carry an identical set of wavelengths.  For example, data on
wavelength lambda sub 1 in input fiber 1 can be switched to output
fiber 2, while data on w...