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How does the EDFA Optical Amplifier Work?
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How does the EDFA Optical Amplifier Work?

Views:0     Author:Site Editor     Publish Time: 2021-05-20      Origin:Site

How does the EDFA Optical Amplifier Work?

EDFA is the miniaturization of an erbium-doped fiber amplifier, which is a device to amplify an optical signal. It is mainly used to compensate for the loss caused by devices and lines, so that the optical signal can propagate for a longer distance. EDFA optical amplifier was first successfully invented by the University of Southampton in 1985. It is one of the greatest inventions in optical fiber communication. Since the late 1980s, the research of erbium-doped fiber amplifier (EDFA) has made great breakthroughs. At present, EDFA has become the most widely used optical amplifier in optical fiber communication.


Here is the content list:

What are the basic structures of EDFA optical amplifiers?

How does the EDFA optical amplifier work?

What are the categories of EDFA optical amplifiers?


What are the basic structure of EDFA optical amplifiers?

EDFA optical amplifier is usually composed of erbium-doped fiber (EDF), pump light source (PUMP-LD), optical coupler, optical isolator and optical filter. Erbium-doped fiber refers to a section of quartz fiber with a length of about 10-100m, in which the core is injected with rare-earth erbium ions Er3+. The pump light source is a semiconductor laser with an output power of about 10~100mw and an operating wavelength of about 0.98 μm. An optical coupler is a passive optical device that mixes the input light signal with the output light wave of the pump light source. It usually uses a wavelength division multiplexer (WDM). An optical isolator is a device that prevents reflected light from affecting the operational stability of the optical amplifier and ensures that optical signal can only be transmitted forward. The function of the optical filter is to filter the noise of the optical amplifier, reduce the influence of the noise on the system and provide the signal-to-noise ratio of the system.

EDFA optical amplifier 

How does the EDFA optical amplifier work?

The reason why EDFA optical amplifier can amplify the optical signal is that under the action of the pump light source, the particle number inversion distribution appears in the erbium-doped fiber, resulting in stimulated radiation, and finally the optical signal is amplified. This is the working principle of the EDFA optical amplifier.

The erbium ion has three working levels: ground state, metastable state and excited state. When the fiber is continuously excited by the pump source laser, the ground state particles gain energy and then transfer to the high energy level. Because the particle is unstable at the high energy level of the excited state, it will rapidly drop to the metastable state through the non radiative transition process, and the lifetime of the particle at this level is relatively long. At this point, the number of particles in the metastable state level is increasing due to the continuous excitation of the pump source, while the number of particles in the ground state level is decreasing. Through this method, the inversion of the particle number distribution in erbium-doped fiber is realized, which provides the conditions for optical amplification.

When the photon energy of the input optical signal is equal to the energy difference between the metastable state and the ground state, the metastable particles will jump to the ground state in the form of stimulated radiation and emit the same photons as the photons in the input optical signal. In this way, the number of photons in erbium-doped fiber increases greatly, the input optical signal becomes a strong output optical signal, and the optical signal is amplified.


What are the categories of EDFA optical amplifiers?

EDFA optical amplifier is a kind of optical fiber amplifier, which is composed of semiconductor optical amplifier and nonlinear optical fiber amplifier. Moreover, the EDFA optical amplifier itself can be classified according to the different pumping modes of the pumping light source, which can be divided into three different structural forms.

1. Co-direction pumping structure

The co-direction pumping structure means that both the pump source and the input signal are injected into the erbium-doped fiber from the same direction.

2. Reverse pump structure

Reverse pump structure means that the pump source and input signal are injected into the erbium-doped fiber from two opposite directions.

3. Bidirectional pumping structure

Bidirectional pumping structure refers to EDFA optical amplifier with both CO and reverses pumping.


The unique advantages of the EDFA optical amplifier have been recognized by the world, and more and more widely used. Hengchi Electronic Equipment Co., Ltd. is committed to the production of stable performance products through the design of optical fiber and electronic circuits, and has been highly appraised for a long time. If you are interested in EDFA optical amplifier industry or have purchase demand, you can consider our cost-effective products.

Our engineers has over 14 years experience designing complex fiber optic and electronic circuits.




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