1. Overview of WDM Upgrade Capacity of fiber
Extremely narrow spectral width light source
Various optical channel can support different transmission formats

2. Operational Principal of WDM
Transmission bandwidth allow the use of many simultaneous channels for sources with narrow spectral width.

3. Implementation of WDM Network

4. Passive Optical Coupler
Couplers with 64 inputs and outputs are possible, more commonly the size tends to be less than 10
Basic Star Coupler for combining or splitting optical power

5. The 2x2 Coupler
Numerical based on these formulae

6. Symmetric/ asymmetric couplers7

7. Fig. 10-11: Fused-fiber star coupler

8. 8x8 star coupler 12

9. Isolators Allow light to pass through them in only one direction.
Keep backward travelling light from entering a laser diode and possibly causing instabilities in the optical output.
Simplest one depend on state of polarization of input light.
Results in 3dB loss

10. Circulators
Multi-port passive device that directs light sequentially from port ot port in only one direction.

11. Fiber Grating Filters Combining and Separating individual wavelengths
Transmitting or Reflecting Grating
Basic Parameters in reflection grating
ϴi= Incident angle
ϴd= diffracted angle
Λ = period of grating
Pitch of grating: spacing between two adjacent slits

12. FBG Applications
Simple De-Mux Function

13. Optical Fiber Amplifiers

14. Basic Operation of Generic Optical Amplifier

15. SOA: Semiconductor Optical Amplifiers
Creating population inversion
They can be easily integrated on the same substrate as other optical devices and circuits (e.g. couplers, optical isolators and receiver circuits)
More rapid gain response order of 1 to 100 ps.

16. EDA: Erbium Doped Fiber Amplifier

17. DFA Ability to pump the devices at several different wavelengths
Low coupling loss
Very low dependence of gain on light polarization
Requires specially constructed fiber.

18. Raman Amplifiers
Based on Stimulated Raman Scattering occurs at high optical powers.
Gain mechanism can be achieved through a pumped or distributed amplifier.
Lumped Raman Amplifier:
A spool of about 80 m of small core fiber along with appropriate pump lasers
Distributed Raman Amplifier:
One or more Raman Pump lasers convert the final km of transmission fiber into a preamplifier.