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Optical Networks Optical Circuit Switching (OCS)
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Page 1: Optical Networks Optical Circuit Switching (OCS).

Optical NetworksOptical Circuit Switching (OCS)

Page 2: Optical Networks Optical Circuit Switching (OCS).

Cheyns: Optical packet switched... AWG

● Results from the EU IST-project STOLAS● Optical packet/burst switches requires fast (ns)

reconfigurable switching matrixes. ● AWG with fast tunable wavelength converters is an

alternative.

Page 3: Optical Networks Optical Circuit Switching (OCS).

Arrayed waveguide Grating● 1 X N or N X N coupler spreads the light in N

waveguides with different lengths ● Waveguides are merged and create interference● Each wavelength will constructively recombine at

only one given output port and cancel out on the others, due to the phase difference

Page 4: Optical Networks Optical Circuit Switching (OCS).

AWG switching principle● Cyclic

– F fibres , W wavelengths– Same output for j as for j + W

● Table: Given input port and wavelength, the output port is found from the table.

Page 5: Optical Networks Optical Circuit Switching (OCS).

Simple AWG node architecture● Internal blocking when two inputs with the same to the same

fibre– No conversion at output – Conversion range at input: 0 to 3 required– Limits which output port the input can be connected to =>

blocking– Internal blocking may be relaxed by smart choices of output

wavelengths for converters and many wavelengths.

0

Page 6: Optical Networks Optical Circuit Switching (OCS).

No blocking version● Input converters must be able to convert to seven

different wavelength converters: Larger wavelength range.

● Fixed wavelength at output converters for multiplexing● Only one wavelength for each output. ● Potential problems with scaling, size of AWG.

Page 7: Optical Networks Optical Circuit Switching (OCS).

Using smaller AWGs● Future networks have many wavelengths: Scalability

– Simple to add an extra input: Add extra input on optical coupler (cheap).

● AWG with W input/output ports– Two inputs which is combined can not be converted to the

same : Contention● Couplers at output ports

– Same blocking properties as the first design. (Same setting)

– Scales with W rather than F*W (first design)

Page 8: Optical Networks Optical Circuit Switching (OCS).

Small AWG, many internal wavelengths

● Nonblocking● F*W internal

wavelengths● 2F multiplexers with

size F*W● Several wavelengths

on each output port. – W*F2 TWC’s with

conversion grade W

● Tunable converters at output

Page 9: Optical Networks Optical Circuit Switching (OCS).

Alternative solution (multiport):● Reduced size of muxes and number of converters● Still nonblocking

– Still FW internal wavelengths – FW fixed output wavelength converters– W demultiplexers, but F smaller/cheaper

Foretrukket!

Page 10: Optical Networks Optical Circuit Switching (OCS).

Optical Pan European Network (The OPEN project)

● Broadcast & Select switching architecture, non-blocking ● Multicast is simple● Scaling a problem, attenuation in couplers.

All inputs available for all outputs

Page 11: Optical Networks Optical Circuit Switching (OCS).

Norway-Denmark field trial

Norway

Denmark

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140

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Kristiansand

Page 12: Optical Networks Optical Circuit Switching (OCS).

Field trial● OXC, wavelength conversion, Optical Add/drop● Mix of SDH and Pseudo Random Bit sequences (PRBS)● Different fibre types, Dispersion Compensating Fiber

(DCF), amplifiers, transponders