Abstract

AM-VSB CATV transport systems can use wavelength-division-multiplexing (WDM) technique to increase channel capacity. However, there exists several crosstalk between optical channels in WDM transport systems.¹⁻² The crosstalk is mainly caused by the stimulated Raman scattering (SRS) and cross-phase modulation (XRM) interaction. The crosstalk for the system with channel spacing >4 nm is dominated by the SRS interaction. SRS-induccd crosstalk will be deteriorated by increasing the channel spacing because of larger Raman gain. And the crosstalk for the system with channel spacing <4 nm is dominated by the XPM interaction. As a result of FM-AM conversion due to fiber dispersion, XPM interaction between optical channels will introduce large crosstalk in WDM transport systems. XPM-in-duced crosstalk will be increased by decreasing the channel spacing because of more XPM interaction. The simulation of XPM-induced crosstalk of −48 dBc in a two-wavelength WDM transport system with 13 dBm optical power per wavelength, 2 nm channel spacing and 20 km singlemode fiber (SMF) has been reported.³ However, technique for reducing the XPM-induced crosstalk in WDM transport systems has not addressed. In recent studies, chirped fiber grating (CFG) has been used as a dispersion compensation device in digital and analog lightwave transport systems.⁴⁻⁵ However, its applications in WDM transport systems are not seen. CFG, which has negative dispersion, is expected to have low crosstalk in a two-wavelength WDM transport system. In this letter, the study presents a technique by using the CFG as a dispersion compensation device to reduce the XPM-induced crosstalk in a two-wavelength WDM transport system.

© 2002 Optical Society of America