Optical amplifiers are the critical technology for the optical communication networks, enabling the transmission of many terabits of data over distances from a few hundred kilometers to thousands of kilometers by overcoming the fiber loss limitation. As the first optical amplifier commonly used in optical communications systems, EDFA has resulted in a dramatic growth in transmission capacity with the deployment of WDM systems. Be equipped with the features of high output power, high gain, wide bandwidth, polarization independence and low noise figure, EDFAs have become one of the key components used in the new-generation optical communication system.
What Is EDFA?
An EDFA, also called optical amplifier or an erbium-doped fiber amplifier or erbium amplifier, is an optical or IR (Infrared Radiation) repeater that amplifies a modulated laser beam directly, without opto-electronic and electro-optical conversion. The device uses a short length of optical fiber doped with the rare-earth element erbium. When the signal-carrying laser beams pass through this fiber, external energy is applied, usually at IR wavelengths. This so-called pumping excites the atoms in the erbium-doped section of optical fiber, increasing the intensity of the laser beams passing through. The beams emerging from the EDFA retain all of their original modulation characteristics, but are brighter than the input beams.
An erbium-doped fiber amplifier
There are three three major applications for optical fiber amplifiers: booster amplifier, in-line amplifier, and pre-amplifier. These applications are described in more details below:
Booster amplifiers are placed directly after the optical transmitter. In this application, booster amplifier is adopted to compensate for the losses of optical elements between the laser and optical fibers so that the increased transmitter power can be used to go further in the link.
In-line amplifiers or in-line repeaters are placed along the transmission link to compensate for the losses incurred during propagation of optical signal. They take a small input signal and boost it for re-transmission down the fiber. Here it should also be pointed out that to control the signal performance and the noise added by the EDFA is important, because noise added by amplifier will limit the system length.
Pre-amplifiers are placed just before the receiver to increase the signal level before the photodetection takes place in an ultra-long haul system so as to improve receiver sensitivity. By placing a pre-amplifier, a much larger signal can be presented to the receiver, thus easing the demands of the receiver design.
Optical amplifiers in a fiber optic data link
As EDFA performs as the most widely used optical amplifier, EDFA technology proves to be the most advanced one that holds the dominant position in the market. With the deployment of WDM systems and the increasing aggregate bandwidth of optical fibers, WDM system integrated with EDFA will gain more benefits.
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