DWDM (Dense Wavelength Division Multiplexing) has been implemented throughout the world by telecommunication carriers as a measure to cope with the increasing data traffic. Rather than deploying cables to increase the fiber capacity, DWDM to a great extent can take care of the increase in demand for high bandwidth and high transmission rates. Proper components for DWDM is the key to the successful implementation of a DWDM system.
Component selection and careful deployment are essential to make sure the proper functioning of the deployed DWDM system.
There are a few key things to take care of when installing a DWDM system. These include ensuring that all the components in the DWDM system are selected and adjusted for the operation at specified wavelengths. In addition, transmitters and receivers should operate at the right wavelengths.
Careful selection and installation of components should assure that crosstalk between channels is low. It is important that adverse effects such as chromatic dispersion, polarization mode dispersion, and non-linear effects are suitably managed.
One of the good reference sources for determining the requirements for frequency deviation, frequency drift, frequency wander, jitter, and chirp is ITU recommendation G.692.
Below are the specific key performance parameters of a DWDM system;
Receiver Sensitivity: Detector and diagnostic equipment should be able to detect very low signal levels. The system components should add very little noise to the system. Otherwise, full characterization of the system performance may not be possible
Optical Rejection: Optical rejection is also called the dynamic range and it is essential that the system design and the diagnostic tools used with it are able to sense small signals in the presence of large signals in adjacent channels. Strength differences might be as much as 35dB.
Resolvable Bandwidth: Test equipment must be able to resolve the signals from closely spaced wavelength bands. For some modern DWDM system, this means being able to resolve 12.5 GHz channel spacings, and these days much much smaller than the 12.5 GHz.
Wavelength Accuracy: We must be assured that all components in the DWDM system as well as test equipment, are calibrated accurately. Without such calibration, the likelihood of Channel-to-Channel conflict is dramatically increased.