Booster Amplifier
A booster amplifier operates at the link's transmission side, designed to amplify the signal channels exiting the transmitter to the level required for launching into the fiber link. It's not always needed in single-channel relations but is an essential part of the 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. The in-line EDFA is designed for optical amplification between two network nodes on the main optical link. In-line EDFAs 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.
Pre-amplifier
A pre-amplifier EDFA operates at the receiving end of a DWDM link. The pre-amplifier is used to compensate for losses in a demultiplexer near the optical receiver. Before the receiver end of the DWDM link, pre-amplifier EDFA works to enhance the signal level before the photodetection occurs in an ultra-long-haul system, hence improving the receive sensitivity. It has relatively low input power, medium output power, and medium gain.
Advantages and Drawbacks of EDFA
Nowadays, EDFA optical amplifier rises as a preferable option for signal amplification methods for DWDM systems, owing to its low-noise and insensitivity to signal polarization. If you are troubled about choosing the amplifier, the advantages and disadvantages will give you clues.
Advantages
1.EDFA has high pump power utilization (>50%).
2.EDFA directly and simultaneously amplifies a broad wavelength band (>80nm) in the 1550nm region, with a relatively flat gain.
Gain-flattening optical filters can improve 3.Flatness.
