Regenerative SPM-Based Wavelength Conversion and Field Demonstration of 160-Gb/s All-Optical 3R Operation

In this paper, we describe a 160-Gb/s all-optical 3R regenerator consisting of a wavelength converter based on self-phase-modulation (SPM) and a non-linear optical loop mirror (NOLM). Particularly, we focus on the simple method to improve the performance of dual-stage wavelength conversion. The dual-stage configuration is useful to alleviate pulse-to-pulse interaction, which degrades both conversion bandwidth and regenerative effect. Total conversion performance, however, strongly depends on waveform distortion at the 1st-stage conversion. Against this, we found that when setting the wavelength shifts of the 1st -stage: ????₁ and the 2nd-stage: ????₂ to be ????₁????₂ < 0, i.e., reversing a wavelength shift at the 2nd-stage, the impact of waveform distortion was suppressed and the conversion performance was dramatically improved in comparison with a monotonic shift over both stages (????₁????₂ > 0). The physical mechanism proving the benefit of the proposed conversion scheme is discussed through both numerical simulations and wavelength conversion experiments. The 3R performance assisted by the regenerative wavelength converter was evaluated by 160-Gb/s field transmission experiments which were conducted in the optical test-bed of Japan Gigabit Network II (JGN II). At a 3R-interval of 380 km, a Q-factor improvement of greater than 7 dB was achieved by applying the wavelength-converter assisted all-optical 3R regenerator.