WDM FSO network with turbulence-accentuated interchannel crosstalk

A wavelength division multiplexing (WDM) access network using high-speed free-space optical (FSO) communication for the distribution link is proposed. Combining FSO communication with optical fiber can reduce the system cost and provide high-bandwidth access in regions where optical fiber installation is problematic. The WDM channels suffer from interchannel crosstalk, while the FSO communication performance in a clear atmosphere is limited by atmospherically induced scintillation. These impairments, plus the amplified spontaneous emission noise from optical amplification, combine in a potentially problematic way, particularly in the upstream direction, which is investigated here. This turbulence-accentuated crosstalk effect is considered for the cases of 1) signal turbulent but crosstalk not and 2) crosstalk turbulent but signal not. Error floors are obtained in each case. The FSO link length that can be supported in the general case of the hybrid network is investigated.