Intermodulation distortion in 48 TV channel FM-FDM optical transmission

The effect of dispersive fibers on multichannel FM video transmission characteristics is experimentally investigated. A directly modulated 1.5 mu m distributed feedback laser diode (DFB-LD) and a LiNbO/sub 3/ external modulator with a continuous-wave (CW) 1.55 mu m DFB-LD are used as optical signal sources. When the 1.3 mu m single-mode fiber (SMF) is used, directly modulated DFB-LDs suffer from second-and third-order intermodulation distortion (IMD). The external modulator realizes good transmission characteristics irrespective of the fiber's dispersion value. This means that external modulators can realize multichannel FM television signal transmission systems that use the standard 1.3 mu m SMF already installed in fiber optic subscriber loops.<>