Optical Networks Optical Circuit Switching (OCS)
Dec 16, 2015
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.
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
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.
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
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.
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)
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
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!
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
Norway-Denmark field trial
Norway
Denmark
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Oslo
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Arendal
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Hjørring Thisted
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Kristiansand