Transcript Practical Optical Packet Routers

Practical Optical Packet Routers
Masataka Ohta
Graduate School of Information Science and Engineering
Tokyo Institute of Technology
[email protected]
1
Why Optical Computers are
Impractical?
• Must compute optically
– Logical AND/OR operations are non-linear
– Optical devices have little non-linearity
– Long interaction of highly concentrated light is
necessary
• Not very fast
• Must memorize optically
– Light can not stop
2
Why Optical Routers are
Practical
• May not control optically
– As long as payload is switched optically
• No one complains if optical routers are controlled
electrically with electric header processing
• May not memorize optically
– Buffers are to avoid packet collisions at output
ports
• Delaying with FDLs (fiber delay lines) is enough
3
Timing Considerations
• 1Tbps is fast enough
– to make fiber delay lines short
• 1500B packet is 12ns long or 3.6m long in vacuum
• 1Tbp is slow enough
– to allow for electric control
• FPGA 2ns, external SERDES enables finer control
• SRAM for L3 route look up 3.3ns
– to allow for optical switching
• Optical switches works within 100ps
4
Many Wavelengths enables
Wideband 1Tbps Packets
• To Encode a Packet at 1Tbps
– Simultaneously modulate 100 Wavelengths
each at 10Gbps
Wavelength
Wavelength
time
Single Wavelength Packets
time
Many Wavelength Packets
5
Optical Packet Format of
Many Wavelength Packets
for (Almost-all) Optical Switches
Header
Wavelength
Payload
Time
Wavelengths to
be processed, updated
& switched electrically
Wavelengths to
be switched
optically
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Routing Table
Control Logic
Original
Header
Electric
Optical
Modified
Header
ADM
ADM
Buffer
ADM
ADM
Buffer
ADM
ADM
Buffer
Structure of an Optical Packet Switch with Many-Wavelength Packets
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Very Small Amount of Buffer is
Required at the Backbone
• Backbone Traffic is Poisson, if
– backbone speed is much faster than access
• 1Tbps backbone is much faster than most, if not all,
access
– Paced TCP is used
• Exceptional hosts with exceptionally fast access
should use paced TCP
• An Optical Buffer with 15 or 31 Fiber
Delay Lines is Enough
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Experiments on Many
Wavelength Packets at NICT
• Buffering with 31 FDLs
– S. Shinada, H. Furukawa, and N. Wada, "Investigation of Optical
Buffer Capacity using Large-scale Fiber Delay Lines for Variablelength Optical Packet Switching," ECOC2013, Th. 1.A.1, Sep.
2013.
• 50km transmission of 12.8Tbps packet
– S. Shinada, J. M. D. Mendinueta, S. L. Ruben, and N. Wada,
"Operation of a 12.8 Tbit/s DWDM Polarization Division
Multiplexing 16-QAM Optical Packet Switching Node after 50-km
of Fiber Transmission," ECOC2014, p. We.3.5.4, Sep. 2014.
• Stable daily operation at 10Gbps*10wavelengths with
2FDLs
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Estimated Power Consumption
• 1Tbps*4port optical routers with 15 FDLs
can be constructed, for example, with
– 476 2:2 optical switches (2.5dB loss)
• Each consumes 10mW
– 128 10dB EDFAs (2.4mW optical output)
• Each consumes 40mW
– About 10W of power
• 100Gbps*36port infiniband chip: 83W
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