SBS based slow-light performance comparison of 10-Gb/s NRZ, PSBT and DPSK signals

We have demonstrated error-free operations of slow-light via stimulated Brillouin scattering (SBS) in optical fiber for 10-Gb/s signals with different modulation formats, including non-return-to-zero (NRZ), phase-shaped binary transmission (PSBT) and differential phase-shift-keying (DPSK). By directly modulating the pump laser diode (LD) using current noise source, the SBS gain bandwidth and profile can be simply controlled by the peak-to-peak value and power density distribution of the current noise. Super-Gaussian noise modulation of the Brillouin pump LD allows a flat-top and sharp-edge SBS gain spectrum, which can reduce slow-light induced distortion in case of 10-Gb/s NRZ and PSBT signals. For the 10-Gb/s NRZ signal, the error-free slow-light operation has been achieved for the fist time and the corresponding maximal delay-time with error-free operation is 35 ps. Then we propose the PSBT format to minimize distortions resulting from SBS filtering effect and dispersion accompanied with slow light owing to its high spectral efficiency and strong dispersion tolerance. The maximal delay of 51 ps with error-free operation has been achieved. Furthermore, the DPSK format is directly demodulated through a Gaussian-shaped SBS gain, which is achieved using Gaussian-noise modulation of the Brillouin pump. The maximal error-free time delay after demodulation of a 10-Gb/s DPSK signal is as high as 81.5 ps, which is the best demonstrated result for 10-Gb/s slow-light.