Erbium Doped Fiber Amplifiers: State Of Art

The field of optics has a drastic impact in the field of electronics and communication. With the rising need for higher data transfer rate, optical advancements have served this purpose. Optical amplifiers play a crucial role in the amplification of signal at regular intervals to avoid loss of data. Erbium doped fiber amplifiers (Erbium Doped Fiber Amplifier) carry out the amplification by stimulated emission and spontaneous emission and are known to provide a higher gain when compared to other optical amplifiers in this domain. This paper throws light on state of art results of the EDFA based on several experiments to measure their gain and noise figure. It is found that it provides better results for amplification of optical signals. ———————————————————— INTRODUCTION The advancement in the field of optical fiber communications has been increasing with every passing day as a result of new optoelectronic technologies that aim at utilizing the wide bandwidth of optical fiber. When setting up a Fiber Optic link, certain parameters like Power budget, Sensitivity of the receiver, link quality & path loss are to be considered for effective error free communication between the transmitter and the receiver. To establish a communication link of several kilometers repeaters are added at regular distances to amplify the signal to overcome the path loss and other associated losses. The conventional method employed for these types of repeaters are Optical to Electrical Converters (O/E Converters). These O/E Converters introduce noise in the signal level and consume more power. Hence this process of O/E and E/O is best suited for low to moderate speed signals of single wavelength. To overcome the problem associated with the above, Optical amplification was introduced. In Optical amplification, the optical signal will be amplified in the same optical domain itself without doing any conversion and hence it is simpler. The introduction of noise in the signal will be eliminated by this optical amplification. There are several different physical mechanisms that can be used to amplify a light signal, which correspond to the major types of optical amplifiers. In doped fiber amplifiers and bulk lasers, stimulated emission in the amplifier's gain medium causes amplification of incoming light. In semiconductor optical amplifiers (SOAs), electron-hole recombination occurs. In Raman amplifiers, Raman scattering of incoming light with phonons in the lattice of the gain medium produces photons coherent with the incoming photons. Parametric amplifiers use parametric amplification. There are two popular types of optical amplifiers viz. Semiconductor Optical Amplifier (SOA) and Erbium Doped Fiber Amplifier (EDFA). The SOAs are based on a semiconductor gain medium. They consume less power and have fewer components than EDFA and are very compact. But the disadvantages of SOA are higher noise, lower gain, polarization dependant and highly nonlinear for a high speed signals. Doped fiber amplifiers use a doped optical fiber as a gain medium as opposed to semiconductor in SOA. Amplification of the input signal is carried out by the stimulated emission of the photons from the dopant ions in the doped fiber and an external pump sources is used to get the stimulated emission of the doped fiber. This stimulated emission is responsible for the amplification of the input signal. These amplifiers can be doped by small amount of any rare earth element like Erbium, neodymium, ytterbium, thulium or praseodymium into the optical fiber, the optical amplification is achieved.