Title :
Overmodulation in subcarrier multiplexed video FM broad-band optical networks
Author :
Mendis, Frederick V C ; Tan, B.T.
Author_Institution :
Dept. of Electr. Eng., Nat. Univ. of Singapore, Singapore
fDate :
9/1/1990 12:00:00 AM
Abstract :
The probability of an SCM (subcarrier multiplexed) signal falling outside the linear region of a laser diode is calculated in order to determine the overmodulation that may be practically employed for multichannel video distribution in single-octave SCM networks. The overmodulation is predicted as a function of the number of subcarriers in single-octave SCM systems supporting up to about 70 FM video channels, for SNRs (signal-to-noise ratios) of 47 dB (I/PAL), and 56 dB (M/NTSC). The RMS optical modulation index (OMI) is demonstrated to be a more useful performance parameter than the linear OMI in SCM systems carrying a large number of channels. A 47 dB weighted SNR (with 4 dB margin) is deemed sufficient for acceptable picture quality in cable distribution systems, whereas a 56 dB value would be required for long-distance point-to-point optical links. RMS OMI values of around 70 and 50, respectively, can be employed
Keywords :
broadband networks; cable television; carrier communication; frequency modulation; multiplexing; optical links; optical modulation; video signals; 47 dB; 56 dB; FM video channels; I/PAL; M/NTSC; RMS optical modulation index; broadband optical networks; cable distribution systems; laser diode; long distance optical links; multichannel video distribution; overmodulation; picture quality; signal-to-noise ratios; subcarrier multiplexing; weighted SNR; Diode lasers; Frequency modulation; Intelligent networks; Laser noise; Optical distortion; Optical fiber networks; Optical modulation; Passive optical networks; Semiconductor lasers; Signal to noise ratio;
Journal_Title :
Selected Areas in Communications, IEEE Journal on