Characteristics of EDFA Amplifier

Characteristics of EDFA Amplifier
The working principle of fiber amplifiers is very similar to that of solid-state lasers. The relevant energy levels, absorption and gain spectra of erbium ions (Er ³ ⁺) in quartz optical fibers are shown in Figure 2. The amorphous properties of quartz broaden the energy levels of erbium ions into bands, and many transitions can be used to pump erbium ions, with the most effective pump wavelengths being 980 nm and 1480 nm.
The working wavelength of EDFA Amplifier falls precisely within the optimal wavelength range of 1330-1600nm for fiber optic communication. EDFA Amplifier working in the C-band (1530-1565nm) with the lowest fiber loss window have been widely used. In order to fully utilize the bandwidth resources of optical fibers, people are also committed to developing EDFAs in the L-band (1570-1610nm). The L-band is located at the tail of the EDFA gain spectrum, so the L-band EDFAs must use longer fibers and higher pump power, or use highly doped fibers.
EDFA Optical Amplifier has high gain (greater than 30-50dB) and provides flat gain over a wide frequency band (up to 30nm), making it suitable for amplifying signals in multiple optical channels, especially in dense wavelength division multiplexing (DWDM) systems. Low noise (4-8dB), approaching the quantum limit. When applied to WDM systems, the crosstalk between channels is minimized and multiple amplifiers can be cascaded. Having a high saturation output power (10-20 dBm), it can be used as a power amplifier after the transmitter to increase the transmission distance or allocated number of optical nodes without relay lines. The required pump power is low (tens of milliwatts). The gain is independent of the polarization state of the fiber, so it has good stability. Easy to couple with transmission optical fibers, with low coupling loss (<1dB). Except for the pump source, EDFA Optical Amplifier is composed of passive components. Therefore, compared with complex and expensive electronic regenerative relays, the system cost is significantly reduced and the reliability is improved.
In addition, the amplification characteristics of EDFA Amplifier are independent of the system bit rate and data format, so it can amplify and transmit both digital and analog information. The disadvantages of erbium doped fiber amplifier are: large size; The lifespan of the pump source is not long; It cannot be integrated with other devices, which limits the application of erbium doped fiber amplifier in optoelectronic integration (OEIC). In addition, the gain bandwidth of EDFA Amplifier only covers a part of the low loss window of quartz single-mode fiber, which limits the number of wavelength channels that the fiber can accommodate, which is also its shortcoming.