Fiber Amplifier, High-speed Optical Fiber Communication Systems

Fiber amplifier is an all-optical amplifier device. Owning the properties of high reliability, low loss and wide bandwidth, it has been widely used in high-speed optical fiber communication systems. It is also one of important devices in large-capacity all-optical communication systems. Because of more types of fiber amplifiers, the study based on fiber amplifiers themselves is very rich. For some technology more mature fiber amplifiers(for example, erbium-doped fiber amplifier(EDFA)), it is essential to improve the efficiency and quality of signal amplification by studying their performance.At the first of this article, domestic and foreign research on fiber amplifiers is expounded in detail, and working principle and performance indicators of fiber amplifiers are introduced. The mathematical model of optical fiber and fiber amplifier is set up and verified. The working principle, structure and working characteristics of fiber amplifiers are almost comprehensively summarized , and the direction of development of fiber amplifiers is discussed. As single ultrashort optical pulse is magnified by EDFA, it is also influenced by high-order nonlinear effect, especially by the Raman scattering. This influence is studied. The numerical results show that the pulse can get effectively compressed and magnified at the beginning phase after transmitted without the influence of intrapulse Raman scattering; However, under the influence of intrapulse Raman scattering , pusles form a delay pulse and an ahead pulse, and the ahead pulse will continue to split into a new delay pulse and a new ahead pulse, and finally form a delay pulse sequence with roughly same direction of transmission, pulse width and amplitude. It is also show that the intrapulse Raman scattering can be weakened to some extent after inputting chirped pulse. The amplification of ultrashort optical pulses in EDFA is researched. The numerical results show that if the initial distance of near optical pulses is short,the two optical pulses will attract each other and produce a new pulse in the course of amplification. As a result, the efficiency of optical pulses amplification will be lower. After enlarging the initial distance, the efficiency of optical pulses amplification will not improve effectively. The transmission of optical pulses introduced initial chirp in EDFA is researched. The results show that after introducing suitable initial chirp, the negative impacts from optical pulses intercation will reduce , the quality of amplification can improve.