Distortionin Multi-tone Modulation Fiber Systems

This paper analyzes the analog CATV transmission systems to investigate the interfering distortions. Here, it is considered distortions such as the composite second order, composite triple beat, and intermodulation distortion. In optical fiber-based analog CATV transmission systems, there is usually one wavelength used for the signal transmission with multiple analog RF channels modulated onto it. While BER is the most common performance metric in a digital transmission system, measurement of distortion is the critical metrics in an analog transmission system. The results of this study contains the simulations of distortion for a two tones direct modulated analog transmission system, a two tones externally modulated analog transmission system, three frequencies directly modulated together and 20-channel analog CATV system. It is shown that the modulation distortion can be considerably diminished at special frequencies if the overlap of frequencies is truly adjusted by the modulator characteristic parameters. Afterward, the optical attenuators or optical filters can serve to remove the sidebands with low intensities.