Introduction of EDFA

Before talking about Erbium-doped fiber amplifier (EDFA), we must have a simple understanding about optical amplifier (OA). OA is a device that amplifiers an optical signal directly, without the need to first convert it to an electrical signal. It is an important component in optical communication. There are usually 3 different types of OA, including erbium-doped fiber amplifier (EDFA), semiconductor optical amplifier (SOA) and Raman amplifier. EDFA is just one type of OA but plays an important role in a long-haul optical fiber communication. Now I’d like to make a detailed introduction of EDFA.

EDFA is an optical repeater device. It is usually used to improve the intensity of optical signals being carried through a fiber optical communication system. An optical fiber is doped with the rare earth element erbium so that the glass fiber could absorb light at one frequency and emit light at another frequency. With its features of high power transfer efficiency and large dynamic range, as well as low noise figure and polarization independent, it is an ideal solution for Wavelength Division Multiplex (WDM) applications and long-haul applications. In addition, a particular advantage of EDFA is its large gain bandwidth, which is typically tens of nanometers and thus actually more than enough to amplify data channels with the highest data rates.

EDFA sample

Now let us learn the basic principle of EDFA. EDFA is a high gain amplifier. It usually has two used pumping bands 980nm and 1480nm. This action amplifies a weak optical signal to a higher power, effecting a boost in the signal strength. The 980nm band has a higher absorption cross-section and is generally used where low-noise performance is required. The absorption band is relatively narrow so that wavelength stabilised laser sources are typically needed. The 1480nm band has a lower, but broader, absorption cross-section and is generally used for higher power amplifiers. In practice, a combination of 980nm and 1480nm pumping bands is usually used in EDFA.

The following picture shows us the working principle of EDFA. In optical fiber communication system, a relatively high-powered beam of light is mixed with the input signal using a wavelength selective coupler. The input signal and the excitation light must be at different wavelengths. The mixed light is guided into a section of fiber with erbium ions included in the core. This high-powered light beam excites the erbium ions to their higher-energy state. When the photons belonging to the signal at a different wavelength from the pump light meet the excited erbium atoms, the erbium atoms give up some of their energy to the signal and return to their lower-energy state. A significant point is that the erbium gives up its energy in the form of additional photons which are exactly in the same phase and direction as the signal being amplified. So the signal is amplified along its direction of travel only. Thus, all of the additional signal power is guided in the same fiber mode as the incoming signal. There is usually an isolator placed at the output to prevent reflections returning from the attached fiber. Such reflections disrupt amplifier operation and in the extreme case can cause the amplifier to become a laser.

principle of EDFA

By this blog, we have learnt that what is EDFA and its basic principle. If you have any requirements, welcome to visit or contact us over Fiberstore is a professional supplier in this field. It can offer EDFA for you with high quality and competitive price.