Succesful Operation of a Subcarrier-Multiplexed Passive Optical Network in the Presence of Optical Beat Interference

Passive Optical Networks (PONs) are widely viewed as attractive approaches for Fiber-in-the-Loop (FITL) systems since they increase the sharing of expesive optelectronic components and can eliminate active components in the field. sup [1] In such networks, subcarrier multiplexing (SCM) can be used for the upstream transmission (from the subscriber to the head-end), since it eliminates the need for careful control on subscriber timer or wavelength that would be required in time-division multiplexed (TDM) or wavelength-division multiplexed (WDM) systems. sup[2] sup[3] However, such SCM systems, where light from several user's individual lasers are summed in a star coupler, exhibit an impairment called Optical Beat Interface (OBI). sup [4] sup [5] This occurs when two or more subcarrier lasers operate at closely-spaced wavelengths.