The attached narrated power point presentation will attempt to mention the benefits offered by WDM as well as the performance parameters associated with WDM. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.

1. 1
WDM Benefits and
Performance Parameters
MEC

2. 2
Contents
• Introduction.
• General WDM System Block Diagram.
• WDM Features.
• WDM Types.
• WDM Benefits.
• WDM Performance Parameters.
• Sample Eye Diagrams.

3. 3
Wavelength Division Multiplexing
Multiple wavelengths over a single fiber

4. 4
WDM System

5. 5
WDM System
• A number of multiplexers at the transmitter
end.
• Multiplexing more than one optical signal
onto a single fibre.
• Transmitter consists of a laser and a
modulator.
• Light source generates an optical carrier
signal at either fixed or a tuneable
wavelength.
• Amplification provided by looped EDFA
amplifier with adequate gain.

6. 6
WDM System
• Demultiplexers at the receiver to split
signals apart.
• Receiver photodiode detector converts
optical signal to electrical signal.
• Filtering of respective wavelengths at the
receiver after proper opto-electronic
conversion.

7. 7
Wavelength Division Multiplexing
• Carries multiple optical carrier signals on a
single fibre using different wavelengths of
laser light.
• Allows bidirectional communication over
one standard fibre with increased capacity.
• Splits network bandwidth into a number of
small bandwidth optical channels.
• Multiple data stream transfer along the
same fibre at the same time.

8. 8
Wavelength Division Multiplexing
• Increase in network capacity without laying
more fibres.
• More secure compared to other types of
communication from tapping.
• Immune to crosstalk.
• Efficient utilization of available optical fiber
bandwidth capabilities.

9. 9
WDM Types
• Utilizes 1300nm -1550nm window of low
attenuation.
• 3 Types:
- WDM (Wavelength Channel
Multiplexing).
- CWDM (Coarse Wavelength Division
Multiplexing).
- DWDM (Dense Wavelength Division
Multiplexing).

10. 10
WDM Types

11. 11
WDM Benefits
• Capacity Upgradation:
- efficient utilisation of available bandwidth.
- more data transmitted over the same
fiber.
- different wavelengths multiplexed onto a
single optical fibre.
- increase in system capability.

12. 12
WDM Benefits
• Transparency:
- data transmission at different bit rates.
- supports multiple protocols.
- no constraint on how we want to send
the data.
- high speed data transmission.

13. 13
WDM Benefits
• Wavelength Reuse:
- allows for wavelength routing.
- same wavelength may be used again in
a different fibre link.
- wavelength reuse increases capacity.
• Scalability:
- flexibility.
- modify the network when required.
- can add/drop extra processing units if
required.
- help serve more users.

14. 14
WDM Benefits
• Reliability:
- extremely reliable and secure.
- low cross talk.
- secure, less chance of tapping data.
- recovery from network failure.
- provision for path rerouting.
- less chance of data loss.

15. 15
Performance Parameters
• Give a measure of how good or bad the
transmission is.
• Bit Error Rate:
- percentage of bits in error relative to the
total number of bits received.
- expressed as ten to a negative power.
• Optical Signal to Noise Ratio (OSNR):
- ratio of optical signal power to the noise
power within the system.
- Higher the OSNR better the signal reception.

16. 16
Performance Parameters
• Q-Factor:
- compares the frequency at which a system
oscillates to the rate at which it dissipates
its energy.
- Q is 2π times ratio of total energy stored
to the energy lost in a single cycle.
- ratio of stored energy to the energy
dissipated per one radian of oscillation.

17. 17
Performance Parameters
• Eye Height:
- show parametric information about the
signal.
- height of the eye diagram from bottom to
top.
- larger the eye height, the better the
transmission.
- won’t show protocol/logical problems/bit
errors.

18. 18
Eye Diagrams

19. 19
Thank You