A balanced fiberoptic communication link featuring laser RIN cancellation

Abstract

The authors present a novel scheme for a balanced optical communication link intended to reduce the effect of the transmitter laser relative intensity noise (RIN) on the total noise figure and dynamic range of the link. The method is based on splitting the laser's power into two fibers, and modulating only one branch by the RF signal. Maintaining perfect amplitude and phase balancing allows complete cancellation of the laser RIN. In practice, to achieve 20 dB of laser noise reduction an amplitude balancing of 0.5 dB or phase balancing of 6 degrees is required. The balanced scheme presented enables practically a RIN reduction of around 20 dB, which greatly improves the noise floor of the link, which is dominated by laser RIN for a single-ended link. >