1. Network Resources

2. Sublayers of Optical Networks

3. Functions of Layers Optical connection is carried on a l-channel
By assigning a wavelength
By establishing an optical path through a sequence of nodes
Role of NASs
Tune transceivers to the wavelength of l-channel
Establish an optical connection
Role of ONNs
Create an optical path on the wavelength
Establish a potential connection

5. Network Links Coarse and fine spectrum partitioning
Spectrum is divided into wavebands which are further divided into l-channels
Typical optical transceivers can handle signals with 10GHz channel spacing.
Current ONNs can recognize 100GHz spacing
Waveband routing vs. wavelength routing

9. Optical Network Nodes
By functionality of nodes: routing, switching, WC
Static nodes
Directional couplers
Static routers
Dynamic nodes
Permutation switch
Generalized switch
Linear divider-combiners
Waveband-space switch
Waveband-space-time switch
Wavelength interchanging switch

10. Physical topologies based on trees

11. Static Nodes

12. Directional Couplers Passive device
Power transfer matrix
Combining loss when used as a combiner
Excess loss due to device imperfection
Controllable(dynamic) directional coupler
Coupling parameter can be adjusted
Can be used as a permutation switch(a=0 or 1)
Can be used as an attenuator
Large size switches can be constructed

13. 16x16 star coupler

14. Static Router
Without wavelength selectivity, throughput of a BS switch is reduced by a factor of n compared to single fiber capacity
Node capacity can be expanded by wavelength routing (e.g., arrayed waveguide gratings)
Example of fixed routing
k=(i-j) mod n for input j, output i, l=k
Latin square
When used with tunable transceivers, static router can work as a permutation switch

16. Dynamic Nodes Space-division switch Optical cross connect(OXC)
Routes signals on each input to selected outputs
Two types
Permutation
Generalized switch
Linear divider and combiner
Any connection pattern, e.g., one-to-many
Can have the capability of connection termination
Without this property, a closed loop may exist

17. Permutation Switch Crossbar Point-to-point switch
Constructed using controllable couplers
Used for both permutation and generalized switches
Point-to-point switch
Banyan switch
Clos switch
Cost-effective permutation switch
Benes switch

18. Clos switch

19. Benes switch (p=m=2)

20. Blocking Characteristics
Rearrangeably non-blocking
Complex routing algorithm
Interrupt existing connections for new connection
Wide-sense non-blocking
Any connection pattern is possible with “intelligent algorithm”
Strict-sense non-blocking
Simple and most practical but not cost-effective
# of switches in middle stage: m=2p-1

21. Optical Switches
Compared to electronic switches, the size of optical switches is small (order of ten).
Due to small computational overheads, rearrangeably and wide-sense non-blocking switches can be considered.
Due to crosstalk problem, switch architectures may not have the minimum number of cross points.

22. Example
3x3 wide-sense nonblocking switch
state-transition diagram

23. Generalized Optical Switch

24. s-d linear divider and combiner with 2x2 controllable couplers

25. Waveband-Space Switch
Waveband-selective switch (WSS)
Three stage realization
Passive stages + dynamic stage
(n!)m connection states for permutation
Waveband-selective directional couplers
Most simple structure
Wavelength-selective cross-connect(WSXC)
More generally, waveband-space-time switch

27. Wavelength Converters
* (nm)! Connections with WC

28. Four Types of Wavelength Conversion
Computer Communications & Switching Lab.

29. Wavelength Routing Switch with Add/Drop
Computer Communications & Switching Lab.

30. * Derive the # of WSXCs and DFCs for general cases.
WIXC implementation
* Derive the # of WSXCs and DFCs for general cases.

31. Request Blocking in WDM Networks
In case there is no wavelength conversion A B C D F E G l 1 3 2
Call blocking at node C
Computer Communications & Switching Lab.

32. Computer Communications & Switching Lab.
Wavelength Reuse
Computer Communications & Switching Lab.

33. Network Access Station(NAS)

34. WADM-NAS Combination

35. TP and RP
Convert logical signals to transmission signals for modulating lasers in electronic domain
Subcarrier level modulation is often performed
PSK and FSK for digital signals; AM and FM for analog signals
Overlay processors
Regeneration
Wavelength conversion

36. Logical Network Overlay