Optical amplifier: it has the transparency of optical signal format and bit rate. It operates in 1550 nm region with high gain, high optical output power and low noise index. According to different applications, optical amplifier has the following three types:
Booster Amplifier, BA
Pre-Amplifier, PA
Line Amplifier, LA
At present, most of the optical amplifiers used in multi wavelength DWDM systems are EDFA, which mainly consists of an erbium-doped fiber, a pump laser and a DWDM module. EDFA can directly amplify 1550 nm region without the use of electronic regenerator, and can provide flat gain in a considerable wavelength range. That is to say, a single EDFA can provide gain of multiple wavelength paths at the same time, which has replaced most of regenerator applications and become a component of long-distance optical fiber network.
DWDM terminal with optical amplifier can be used in optical transmission network. At the transmitting end, it can accept optical signal input of multiple wavelengths and convert it into optical signal conforming to ITU-T g.692 fixed wavelength. After multiplexer mixing and optical amplification, it is transmitted to optical transmission network. At the receiving end, the signal from optical transmission network can be received and output after optical preamplifier, demultiplexer and optical filter.
There are two types of DWDM terminals:
(1) Open system: commonly known as the transponder based DWDM, there is a frequency converter between SDH and DWDM equipment, which can mediate SDH equipment from different manufacturers.
(2) Integrated system: commonly known as passive DWDM, SDH equipment has the interface function of ITU-T g.692.
