We report a 2R optical regenerator based on the Self-Phase Modulation and offset filtering technique in a bi-directional architecture for the simultaneous processing of two optical channels at 10 Gb/s within a single highly nonlinear fiber. Whereas excellent mitigation of the interchannel nonlinear crosstalk is experimentally demonstrated, we identify Rayleigh backscattering as the major source of crosstalk and show how it is related to the regenerator parameters and operational settings. Finally, we demonstrate that this crosstalk does not introduce any significant additional penalties as compared to single channel operation.