Effect of optical fiber reflections on the performance of sub-carrier-multiplexed (SCM) lightwave systems

Hybrid analog/digital Sub-Carrier-Multiplexing (SCM) technique is effective for broadband optical access networks designed for video broadcasting and interactive services. These systems are flexible in service management and channeling can be optimized to exploit the available bandwidth. A significant impairment in these systems is introduced by optical fiber multiple reflections, which give rise to an interferometric noise affecting the performance. So far, this effect has been evaluated assuming that the delay between transmitted and reflected optical signals is so large that such signals can be considered uncorrelated. In this paper, the interferometric noise due to optical fiber reflections is analyzed in SCM hybrid analog/digital systems independently of the position of the reflection points. The proposed model leads to a closed expression for the power spectral density of such noise source, which provides useful information for the system design and permits an accurate performance evaluation.