Electronic Dispersion Compensation | previous | next | feedback |
(Acronym: EDC)
Definition: a method for mitigating the effects of chromatic dispersion in fiber-optic communication links with electronic components in the receiver
Systems for optical fiber communications can be affected by the effect of chromatic dispersion of the used fibers. Strictly, this effect can be removed only in the optical domain (see: dispersion compensation), and not after detecting the signal with a photodetector, because phase information is lost during detection. Nevertheless, the effect of dispersion can at least be mitigated in the electronic domain (i.e., after the photodetector) by schemes which are called electronic dispersion compensation. Such techniques can be more cost-effective than true optical dispersion compensation. An essential ingredient is the use of transversal filters, where portions of the electronic input signal are subject to different time delays and recombined after amplification with suitable levels. Provided that the settings are carefully optimized, the signal quality can be significantly improved, even though the full potential of true optical dispersion compensation can not be reached. For a given transmitter and fiber, electronic dispersion compensation may increase the transmission distances achieved by e.g. 50%. Alternatively, electronic dispersion compensation may allow the use of a cheaper type of transmitter (e.g. a directly modulated laser instead of a system with an external modulator) and thus lead to significant cost savings.
A technical challenge of great importance for applications is automatic adaptation of the parameters of the electronic dispersion compensator to the link properties, because the ideal parameter settings depend on the properties of the fiber link and the transmitter, and manual optimization is not cost-effective. Particularly in systems with multimode fibers, the optimum parameters may also drift with time.
See also: dispersion, dispersion compensation, optical fiber communications
