Abstract

Dense WDM terabit systems with a 40-Gbit/s capacity per channel are required as the next generation of fiber transmission systems because of their high signal spectral efficiency and low cost.¹ However, compared to 10-Gbit/s/ch WDM systems, these systems have a number of problems in terms of their optical signal-to-noise ratio (OSNR), chromatic dispersion, nonlinear effect, and polarization-mode dispersion (PMD). In particular, the small chromatic dispersion tolerance of these systems is a serious problem. Because the repeater spacing varies from span to span, a change in the transmission distance of only several kilometers can result in exceeding the dispersion tolerance. Furthermore, not only the chromatic dispersion but also the dispersion slope of transmission fiber and that of dispersion compensating fiber (DCF) have distribution due to manufacturing limitation. Moreover, the chromatic dispersion in the installed fiber of terrestrial systems fluctuates depending on the environmental conditions such as changes in temperature. The dispersion compensation using only DCF requires DCF of many different lengths, and cannot be adapted to temporal changes in dispersion. Therefore, adaptive dispersion compensation using only one kind of variable dispersion compensators is needed. We have already developed a 40-Gbit/s variable dispersion compensator using a Virtually Imaged Phased Array (VIPA)^2,3 and have demonstrated its large tunable dispersion compensation range with high group delay flatness.

© 2002 Optical Society of America