Why Is EDFA (Erbium Doped Fiber Amplifier) Essential To DWDM System?
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Why Is EDFA (Erbium Doped Fiber Amplifier) Essential To DWDM System?

Posted on by FS.COM

EDFA (Erbium-doped fiber amplifier) is the state-of-the-art solution for amplifying optical signals in optical transmission systems. In optical communication network, signal travels through fibers in every large distances without significant attenuation. However, when it comes to the distance beyond hundreds of kilometers, EDFA amplifier becomes rather essential to amplify the signal during transition in long distance optical communication in this case. Erbium doped fiber amplifier is a revolutionary breakthrough in the field of optical fiber communication, which makes long-distance, large-capacity and high-rate optical fiber communication possible. EDFA optical amplifier becomes an inseparable device in WDM system, future high-speed system and optical communication.


What Is EDFA?

EDFA, short for Erbium Doped Fiber Amplifier, 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 , of which the core is doped with the rare-earth element Erbium. By using the erbium ions to higher energy levels, we can achieve amplification of signals at 1550 nm and allow high bit-rate transmission over long distance. Erbium-doped fiber amplifier provides a new life to optical fiber transmission as it efficiently makes up the signal attenuation during the long-haul transmission.

Three Types of EDFA In DWDM Link

According to the functions, EDFA usually has three types: booster amplifier, in-line amplifier and pre-amplifier.

Erbium Doped Fiber Amplifier

Booster Amplifier

A booster amplifier operates at the transmission side of the link, designed to amplify the signal channels exiting the transmitter to the level required for launching into the fiber link. It’s not always required in single channel links, but is an essential part in DWDM link where the multiplexer attenuates the signal channels. It has high input power, high output power and medium optical gain. The common types are 20dBm Output C-band 40 Channels 26dB Gain Booster EDFA, 16dBm Output C-band 40 Channels 14dB Gain Booster EDFA and so on.

In-line Amplifier

An in-line amplifier is generally set at intermediate points along the transmission link in a DWDM link to overcome fiber transmission and other distribution losses. Optical line amplifier is designed for optical amplification between two network nodes on the main optical link. In-line amplifiers are placed every 80-100 km to ensure that the optical signal level remains above the noise floor. It features medium to low input power, high output power, high optical gain, and a low noise figure.


A pre-amplifier operates at the receiving end of a DWDM link. Pre-amplifier is used to compensate for losses in a demultiplexer near the optical receiver. Placed before the receiver end of the DWDM link, pre-amplifier works to enhance the signal level before the photo detection takes place in an ultra-long haul system, hence improving the receive sensitivity. It has relatively low input power, medium output power and medium gain.

Working Principle

Basically, EDFA consists of a length of EDF, a pump laser, and a WDM combiner. The WDM combiner is for combining the signal and pump wavelength, so that they can propagate simultaneously through the EDF. EDFA can be designed that pump energy propagates in the same direction as the signal (forward pumping), the opposite direction to the signal (backward pumping), or both direction together. The pump energy may either by 980nm pump energy or 1480nm pump energy, or a combination of both. The most common configuration is the forward pumping configuration using 980nm pump energy. Because this configuration takes advantage of the 980nm semiconductor pump laser diodes, which feature effective cost, reliability and low power consumption. Thus providing the best overall design in regard to performance and cost trade-offs.

Why EDFA Is Essential To DWDM System?

We know that when transmitting over long distance, the signal is highly attenuated. Therefore it is essential to implement an optical signal amplification to restore the optical power budget. This is what EDFA commonly used for: it is designed to directly amplify any input optical signal, which hence eliminates the need to firstly transform it to an electronic signal. It simply can amplify all DWDM channels together. Nowadays, EDFA optical amplifier rises as a preferable option for signal amplification method for DWDM systems, owing to its low-noise and insensitive to signal polarization. Besides, EDFA deployment is relatively easier to realize compared with other signal amplification methods.

Notices When Buying EDFA For Your DWDM System

To ensure the required level of amplification over the frequency band used for transmission, it is highly important to choose the optimal configuration of the EDFA. Before you buy an erbium doped fiber amplifier, keep in mind that the flatness and the level of the obtained amplification, and the amount of EDFA amplifier produced noise are highly dependent on each of the many parameters of the amplifier.

FS.COM DWDM EDFA For Long-Haul DWDM Networks

FS.COM DWDM EDFA optical amplifiers compromise 26dB Gain C-band 16dBm Output Pre-Amplifier DWDM EDFA, 22dBm Output C-band 24dB Gain Booster DWDM EDFA and 17dBm Output C-band 17dB Gain In-Line DWDM EDFA. All features plug-in card type designed for FS.COM Multi-Service Transport (FMT) system. The FS.COM DWDM EDFA is a low-noise, gain-flattened C-band optical erbium doped fiber amplifier designed to extend the distance in DWDM optical infrastructure. It provides customers with the capability to extend their 100GHz, up to 40 channels, 2.5Gbps, or 10Gbps optical infrastructure over greater distances. The three kinds of cards have been designed as a Multi-Service Transport System, allowing network administrators to deploy the chassis in a wide range of networks. Besides EDFA, FMT system also includes other devices like OEO, DCM and OLP to build a long-haul DWDM network together. For these devices, FS.COM designed them into small plug-in cards and provides a centralized rack unit and a free software for easier deployment, management and monitoring.


FS.COM mainly provides three types of DWDM EDFAs which have several output options (12dBm-35dBm). EDFA price ranges from $1500 to $1900, relatively leveling off with or lower than market prices. Besides, FS.COM is very professional in optical amplifiers. Whatever doubts you have, they can give you a clear reply. Here is FS.COM EDFA specification for your reference.

ID Type Wavelength Connector Optical Gain Input Power Saturated Output Power Single Channel Input Power Single Channel Output Power
36524 Pre-Amplifier 1528nm~1564nm LC/UPC 26dB -30dBm~-5dBm ≤16dBm -26dBm (Typical) 0dBm (Typical)
36592 In-line Amplifier 1528nm~1564nm LC/UPC 17dB -20dBm~+5dBm ≤17dBm -16dBm (Typical) 1dBm (Typical)
36501 Booster Amplifier 1528nm~1564nm LC/UPC 24dB -25dBm~0dBm ≤22dBm -18dBm (Typical) 6dBm (Typical)
Notes:Return loss of all modules above is <-45dB; Noise figure is 4.5dB (Typical). All types of amplifier listed above can be customized for your specific requirements.


Among the various technologies available for optical amplifiers, EDFA technology proves to be the most advanced one that holds the dominate position in the market. In future, the DWDM system integrated with high performance erbium-doped fiber amplifier, as well as the demand for more bandwidth at lower costs have made optical networking an attractive solution for advanced networks.

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