Distortion and cnr characteristics in fm-fdm optical catv transmission

✍ Scribed by Mikio Maeda

• Book ID: 102819162
• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 800 KB
• Volume: 76
• Category: Article
• ISSN: 8756-6621
• DOI: 10.1002/ecja.4410761203

✦ Synopsis

Abstract

In the multichannel frequency division multiplex (FDM) optical transmission, the intermodulation distortion generated by the nonlinearity of the LD is a problem. In this paper, it is analyzed that for the number of transmission channel, N, and the optical modulation index per channel, m, the CSO and CTB are constant for a different value of N if the effective optical modulation index, is maintained. The results are compared with experiments. In the present analysis, two types of nonlinearity of the current‐to‐optical conversion characteristics are considered. One of them is the nonlinearity near the bias current of the LD and is predominant in the region of a small effective optical modulation index. Another is the nonlinearity at the threshold value of the LD and is dominant when the effective optical modulation index is large. It is shown by means of the probability density function that the CSO and CTB degrade suddenly if the effect of the nonlinearity of the threshold value appears. In the FM‐FDM optical transmission, many distortions in the transmission bandwidth behave as the white noise due to frequency modulation when the carrier is frequency modulated by a video signal. Hence, the CN ratio is effectively degraded. In this paper, it is further presented that the CN ratio degraded by the distortions can be derived from the CSO and CTB by taking into consideration the frequency allocation of the FM signal.