In optical communication network, signal travels through fibers in
every large distances without significant attenuation. However, when it
comes to the distance up to hundreds of kilometers, to amplify the
signal during transit becomes rather essential. In this case, an optical
fiber amplifier is required to achieve signal amplification in long
distance optical communication. This article aims to give a brief
introduction to the most deployed fiber [amplifier— Erbium doped fiber
amplifier
(EDFA)](https://www.4fiber.com/wdm-optical-network/edfa.html?lipi=urn%3Ali%3Apage%3Ad_flagship3_pulse_read%3BzkwpjuCWQbyowJSDogVyyg%3D%3D).
What is EDFA?
An
EDFA is an optical or IR repeater that amplifies a modulated laser beam
directly, without opto-electronic and electro-optical conversion.
Generally speaking, it is an optical repeater device that is used to
boost the intensity of optical signals being carried through a fiber
optic communications system.
Working Principle of EDFA
EDFA
serves as a kind of optical amplifier which is doped with the rare
earth element erbium so that the glass fiber can absorb light at one
frequency and emit light at another frequency. An external semiconductor
laser couples light into the fiber at infrared wavelengths of either
980 or 1480 nanometers. This action excites the erbium atoms. Additional
optical signals at wavelengths between 1530 and 1620 nanometers enter
the fiber and stimulate the excited erbium atoms to emit photons at the
same wavelength as the incoming signal. This action amplifies a weak
optical signal to a higher power, effecting a boost in the signal
strength. The following picture shows 13dBm output C-band 40 channels
booster EDFA for DWDM Networks.
The Advantages of EDFA
The
EDFA obtains the advantages of high gain, wide bandwidth, high output
power, high pumping efficiency, low insertion loss, and it is not
sensitive to the polarization state.
It provides in-line
amplification of signal without requiring electronics, and the signal
does not need to be converted to electrical signal before amplification.
The amplification is entirely optical.
It provides high power transfer efficiency from pump to signal power.
The amplification is independent of data rate.
The
gain is relatively flat so that they can be cascaded for long distance
use. On the debit side, the devices are large. There is gain saturation
and there is also the presence of amplified spontaneous emission (ASE).
The Applications of EDFA
The
EDFA was the first successful optical amplifier and a significant
factor in the rapid deployment of fiber optic networks during the 1990s.
By adopting it in conventional optical digital communication system
applications, we can save a certain amount of optical repeaters.
Meanwhile, the distance relay could also be increased significantly,
which is vital for the long-haul fiber optic cable trunking systems. The
EDFA is usually employed in these circumstances:
EDFA can be
employed in the high-capacity and high-speed optical communication
system. It offers a constructive and ideal solution for handling low
sensitivity of receivers and short transmission distances because of a
lack of OEO repeater.
In addition, EDFA can be adopted in
long-haul optical communication system, such as land trunk optical
transmission system and the submarine optical fiber cable transmission
system. It helps to lower construction cost dramatically by reducing the
quantity of regenerative repeaters.
Moreover, EDFA can also be
employed in wavelength-division multiplexing (WDM) system, especially
dense wavelength-division multiplexing (DWDM) system. It enables the
problems of insertion loss to be solved successfully and reduces the
influences of chromatic dispersion.
Conclusion
By
far, being the most advanced and popular optical amplifier, EDFA has
been widely adopted in the optical fiber communication networks.
Featured by flat gain over a large dynamic gain range, low noise, high
saturation output power and stable operation with excellent transient
suppression, it surely will capture a rather vital and indispensable
position in optical communication in the near future.
Sample [EDFA products](www.4fiber.com)