Optically tunable compensation of nonlinear signal distortion in optical fiber by end-span optical phase conjugation.

We demonstrate a nonlinear signal processing approach for compensating nonlinear distortion caused by the Kerr effect in optical fiber transmission. The concept relies on propagating the signal through a separate all-optical module outside the link to apply tunable nonlinear distortion and phase-conjugation in series. We show this uniquely enables tunable regeneration of phase-encoded 40 Gb/s signals of different data-formats and number of WDM channels, to allow significantly higher transmission powers through single and multi-span fiber links. An improvement in the receiver power penalty by 3~4 dB for a bit-error-rate (BER) of ≈10⁻⁵ is achieved.