Characteristics of Single-Carrier Fiber-Optic Transmission Systems using Optical Amplifiers,

The capability of a very long-distance transmission using erbium-doped fiber amplifiers EDFAs has been demonstrated by using a circulating loop.1,2 In a single-carrier long-distance fiber transmission system, the signal wavelength will usually be tuned to the zero dispersion wavelength of the fiber to avoid the pulse waveform distortion due to chromatic dispersion. It has also been reported that when the signal wavelength is located exactly at the zero dispersion wavelength, the mixing of the signal with the spontaneous emission from the optical amplifiers will produce fourwave mixing sidebands.3 However, in the practical systems, the fiber chromatic dispersion varies along the long transmission path and may alleviate the effect of the four-wave mixing.3 We have investigated the effect of the dispersion variations on long-distance optical amplifiers transmission by numerical simulations. The results show that variation of the fiber dispersion well maintain the signal quality. In addition, this consequence was confirmed by a circulating loop experiment including the fibers with - 1pskmnm dispersion.