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*F 2 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
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