Optical amplifier
In telecommunication, an optical amplifier is a device that amplifies an optical signal directly, without the need to convert it to an electrical signal, amplify it electrically, and reconvert it to an optical signal.
Fiber amplifiers are optical amplifiers which use a doped optical fiber, which bears the communication signal, and is optically pumped with a laser having a high-powered continuous output at an optical frequency slightly higher than that of the communication signal. The signal is intensified by Raman amplification. For this reason, this type of amplifier is sometimes called a Raman amplifier.
Because neither optical-electrical conversion nor electrical amplification takes place, this type of amplifier is well suited for a wide variety of applications, both digital and analog.
Because this type of amplifier does not require extraordinary frequency (wavelength) control of the pumping laser, it is relatively simple.
A fiber amplifier is capable of amplifying a complete wavelength-division multiplexed set of signals as a single wideband optical signal. In this way, an all-optical infrastructure equipped with fiber amplifiers is capable of supporting future modulation and WDM standards, in a way that systems with optical-electrical-optical regeneration cannot. This has led to all-optical infrastructure becoming the standard for long-haul networks, wherever physically possible.
Care must be taken to avoid saturating fiber amplifiers, as this will cause incorrect operation. To prevent this, the power levels of all the signals in a WDM group must be kept carefully balanced.
The most common dopant used in fiber amplifiers is erbium, and such a fiber amplifier is known as an erbium-doped fiber amplifier, or EDFA.
Note: The text of an earlier version of this article was taken from the public domain Federal Standard 1037C.Doped fiber amplifiers
Erbium-doped fiber amplifiers
