Wavelength Swapping Using Tunable Laser for Fractional Lambda Switching

1
Wavelength Swapping Using Tunable
LaserforFractional Lambda Switching
IEEE 14th LANMAN Workshop

• Viet-Thang Nguyen, Renato Lo Cigno, Yoram Ofek
• University of Trento Italy
• Mario Baldi
• Politecnico di Torino - Italy

2
Outline

• Overview
• F?S principles
• Tunable laser
• F?S designs using tunable laser
• Fixed Connection-F?S architecture
• Wavelength Router-F?S architecture
• Broadcast and Select-F?S architecture
• Scheduling feasibility
• Comparisons between designs
• Discussion

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F?S principles

• IP switching
• Header processing
• Buffering and unpredictable jitter and delay
• Time-driven switching of IP packets
• No header processing
• Time label switching using UTC
• constant jitter and no loss
• Related works
• Optical Burst Switching
• Optical Packet Switching
• Both require header processing
• Both may have packet loss due to congestion

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F?S principles TDS in optical layer

• Common Time References
• For freq. and phase synchronization
• UTC (GPS) or the likes

Link channel 10Gbps, 1000 TFs per time-cycle, 80
time-cycle per super cycle, then 1TF capacity -
per time-cycle 10Mbps - per super cycle
125Kbps

• See animation

5
F?S principles TDS in optical layer

• Forwarding schemes based on the coordination of
  UTC signal
• Immediate Forwarding (IF) scheme
• Non-IF scheme (little buffering)

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Tunable lasers and ? Swapping

• Tunable laser
• Receive on one predefined wavelength
• Transmit light signal on a range of wavelengths

Source M. Kauer et.al. in the Photonics
Technology Letters, Vol. 15, No. 3, Mar. 2003

• Wavelength swapping
• As label switching, e.g. change the color of TFs

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FC-F?S architecture (fabric-less)

• Facts
• Fixed connection network of p-2-p links from TLs
  to out-port MUXs
• TLs are controlled to tune every TF such that no
  conflict is allowed
• The color of a TF after being switched defines
  the route of that TF

The Pros - Low HW cost - Low control overhead
and Cons - Rigid routing - Low scheduling
flexibility
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WR-F?S architecture

• Facts
• The same design for OBS first introduced in JSAC
  Sep 03.
• Dif. in-ports use dif. sets of channels to reach
  the same out-port.
• Connection ratio r C/N is the size

• The Pros
• Simple design (still only TLs are active devices)
• No internal conflict (nature of static WRs)

• and Cons
• Scheduling flexibility is limited by the factor r

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BS-F?S architecture (Clos equivalency)

• Facts
• 1 TL 1 BSS per input channel.
• BSS
• 1-to-N star coupler
• N simple ON/OFF elements
• Strictly non blocking space design (wavelength
  time)
• If NC, the HW complexity (i.e. of switching
  elements) is Clos equivalency

• and Cons
• OO elements are controlled and coordinated using
  UTC signal ? higher OH

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Scheduling Unavailability (Blocking?)
Exact Results (using combinatorial analysis)
UTC
BS non blocking design
Outlet channel
Inlet channel
1
k
2
1
k
2
Inlet
Outlet
1
2
3
4
5
6
7
8
9
10
11
12
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Scheduling feasibility

• For comparison, we define

Scheduling feasibility definition a function of
forwarding method (IF or NIF), k, h, C and N to
measure the max. availability of schedules along
the route path for 1-TF fractional lambda pipe,
given zero load

• Scheduling feasibility
• Computation based on hop-based combinatorial
  analysis
• Relation with blocking performance?!
• higher the scheduling feasibility is, the less
  probable that a TF is blocked at scheduling time.

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Comparisons
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Discussion

• Three novel switch designs that are based on the
  use of tunable lasers, in which two are
  interesting
• FC design is fabric-less
• BS design is strictly non-blocking with Clos
  equivalency if of channels/port of ports
  (CN)
• Analytical result 'scheduling feasibility' that
  measures the total number of possible different
  schedules for each switch design, given zero
  load.
• But not blocking performance!
• Scheduling unavailability measures blocking
  probability while scheduling TFs
• Exp. growth of scheduling feasibility implies
  that optimum scheduling to fulfill the long-route
  F?P setup is not trivial ?heuristic algorithms.

14

• More info
• IP-FLOW project (EU funds)
• http//dit.unitn.it/ip-flow/index.html
• Yoram Ofek ofek_at_dit.unitn.it (project
  coordinator)
• or nguyen_at_dit.unitn.it (for this work)
• Thank you!
• QA

15
References

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