How to Place EDFA for DWDM Distance Extension?

No matter where the EDFA optical amplifier is deployed in the DWDM link, the signal power can be always enhanced for making a longer DWDM system.Undoubtedly, the EDFA amplifier is an ideal choice for long-haul DWDM system. But how does it work for extending DWDM system?

Optic Amplifier Basics

The basic form of EDFA consists of a length of EDFA, a pump laser, and a WDM system for combining the signal and pump wavelength so that they can propagate simultaneously through the EDF.

When transmitting over long distance, the optical signal has to be amplified many times in between owing to the signal loss from fiber attenuation, connectivity losses, fiber splicing losses, etc. Before optical amplifier is invented, the optical signal has to be first converted into electrical signal, amplified, and then converted back to optical signal again. The process is very complicated and expensive. Optical amplifier has since been invented that can amplify signals directly, this process is significantly cheaper and started a fiber optic revolution. There are three fiber optic amplifier types: EDFA, Raman amplifier and semiconductor optical amplifier(SOA).

EDFA (Erbium Doped Fiber Amplifier) principle

EDFAs use a pump laser (980 nm or 1480 nm) to bring up electrons to a higher energy level. If signal amplification is achieved by emitted photons of the same signal wavelength with the help of stimulated emission.

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An erbium-doped fiber amplifier (EDFA) is a device that amplifies an optical fiber signal. It is used in the telecommunications field and in various types of research fields. An EDFA is “doped” with a material called erbium. The term “doping” refers to the process of using chemical elements to facilitate results through the manipulation of electrons.The EDFA was the first successful optical amplifier and a significant factor in the rapid deployment of fiber optic networks during the 1990s.

The EDFA rate, or amplification window, is based on the optical wavelength range of amplification and is determined by the dopant ions’ spectroscopic properties, the optical fiber glass structure and the pump laser wavelength and power. As ions are sent into the optical fiber glass, energy levels broaden, which results in amplification window broadening and a light spectrum with a broad gain bandwidth of fiber optic amplifiers used for wavelength division multiplex communications. This single amplifier may be used with all optic fiber channel signals when signal wavelengths are in the amplification window. Optical isolator devices are placed on either side of the EDFA and serve as diodes, which prevent signals from traveling in more than one direction.

How Does EDFA Amplifier Work?

Placed at the Transmitting Side : A booster optical amplifier operates at the transmission side of the link, working to amplify aggregated optical input power for reach extension. Booster EDFA is designed to enhance the transmitted power level or to compensate for the losses of optical elements between the laser and optical fibers. It is usually adopted in a DWDM network where the multiplexer attenuates the signal channels. Booster optical amplifier features high input power, high output power, and medium optical gain.

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Placed at the Intermediate Points: as shown in the figure below, the EDFA in-line amplifier can be put at any intermediate point along the long transmission link. This kind of EDFA optical amplifier is designed with low input power, high output power, high optical gain and low noise figure, which are normally deployed every 80-100 km to amplify signals between any two link nodes on the main optical link, with the aim of compensating the loss caused by fiber transmission and other factors. Thereby, the optical signal level can stay above the noise floor.

 

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Placed at the Receiving Side: A pre-amplifier operates at the receiving end of a DWDM link. Pre-amplifiers are used for optical amplification to compensate for losses in a demultiplexer located 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 features medium to low input power, medium output power, and medium gain.

 

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Conclusion

The EDFA optical amplifier can be deployed as booster optical amplifier , in-line amplifier and pre-amplifier contributes to optimize network performance for extending the reach. It can also work as in-line amplifier at the intermediate point along the link for compensating the fiber loss in the transmission link.Which also increases data capacity required for current and future optical communication system. Optical Amplifiers provided by Fiber-Mart are designed for all network segments (access, metro, regional and long haul) and applications (telecom, cable and enterprise). any question pls not hesitate to contact us www.fiber-mart.com or E-mail: service@fiber-mart.com

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