Abstract

Beyond 10 Gbit/s, the fiber dispersion becomes an increasingly difficult barrier to overcome. A number of optical techniques have been demonstrated to overcome the dispersion limitations. The most straightforward is the use of dispersion-shifted fiber. In a number of applications, however, this is not a feasible solution, for example, if the system is using an existing fiber plant or if multiple wavelengths are used. In prechirping techniques for dispersion compensation, the optical data pulses are chirped at the source so that fiber dispersion results in an initial pulse compression that substantially extends the transmission range. Prechirping has been demonstrated using external modulators¹ and used for 40-Gbit/s transmission over 64 km². A variation of this technique used a sinusoidally modulated (chirped) laser source combined with an external amplitude modulator to achieve 10 Gbit/s transmission over 100 km.³ Prechirping has also been demonstrated using self-phase modulation in semiconductor laser amplifiers and used for 16 Gbit/s pulse train transmission over 70 km⁴. Although the prechirp techniques can extend the transmission distance substantially, it is not extendable over several span lengths as would be desirable in amplified systems.

© 1992 Optical Society of America