PDF of this tutorial- A number of optical transmitters
- An optical multiplexer
- Spans of optical transmission fiber, such as standard single-mode fiber (SSMF)
- Optical amplifiers, usually erbium-doped fiber amplifiers (EDFAs)
- Dispersion compensating devices, like spans of dispersion compensating fiber (DCF) or chirped fiber Bragg gratings (FBGs)
- An optical demultiplexer
- A number of optical receivers
Figure 1 shows the layout of such a WDM system.
Figure 1. Typical WDM Transmission Link
The dramatically increasing service demand driven by the rapid growth of the Internet generates new challenges for WDM system designers. Common design approaches reach their limits, and the usage of comprehensive modeling techniques becomes more and more important. Additionally, to achieve the demanding targets created by the application-oriented business developments, future systems must comply with upgraded performance criteria, such as the following:
- Transmission of higher total data capacities through increased channel bit rates and number of wavelength-multiplexed channels
- Cost-reduction by allowing longer amplifier spacing and, thus, reduction of the number of EDFAs per optical link
- Reduction of signal distortion to allow transmission over longer all-optical transmission links
There are several new design approaches to meet these criteria, including the following:
- New transmission windows in wavelength domain
- New types of optical amplifiers covering a very high signal bandwidth to increase data capacity
- Bidirectional WDM transmission allowing suppression of nonlinear fiber interactions
All of these techniques require a thorough understanding of the underlying physical effects and the interplay between diverse optical devices to judge their impact on system performance measures, using numerical simulation tools.
