Improved slow-light performance of 10 Gb/s NRZ, PSBT and DPSK signals in fiber broadband SBS

Lilin Yi,Weisheng Hu,Sébastien Bigo,Yves Jaouen,Yikai Su

doi:10.1364/oe.15.016972

Abstract

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-shiftkeying (DPSK). The SBS gain bandwidth is broadened by using current noise modulation of the pump laser diode. The gain shape is simply controlled by the noise density function. Super-Gaussian noise modulation of the Brillouin pump allows a flat-top and sharp-edge SBS gain spectrum, which can reduce slow-light induced distortion in case of 10-Gb/s NRZ signal. 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 because of its high spectral efficiency and strong dispersion tolerance. The sensitivity of the 10-Gb/s PSBT signal is 5.2 dB better than the NRZ case with a same 35-ps delay. The maximal delay of 51 ps with error-free operation has been achieved. Futhermore, 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.

Highlights

Slow light based on the group velocity control of signal propagation, has attracted much interest due to potential applications in future optical communication networks, such as optical buffering and data synchronization
In this paper we especially focus on minimizing the signal distortions and improving the system performances of 10-Gb/s signals in stimulated Brillouin scattering (SBS) based slow light for different modulation formats: non-return-to-zero (NRZ), phase-shaped binary transmission (PSBT) and differential phase-shifted-keying (DPSK)
We have analyzed the signal distortions of the SBS-based slow light, and presented solutions to minimize them for improving the signal quality after delay

Summary

Introduction

Slow light based on the group velocity control of signal propagation, has attracted much interest due to potential applications in future optical communication networks, such as optical buffering and data synchronization. The relevant research topics mainly focus on three aspects: (i) broadening the SBS gain bandwidth to support high-speed data delay by modulating the Brillouin pump [3,4,5]; (ii) improving the fractional delay to increase the storage capability by cascading SBS based delay-lines [6] or combining the Brillouin gain and loss spectra of two different SBS pumps [7]; (iii) minimizing the signal distortions to improve the signal quality after delay by using multi-line Brillouin pump [8]. The distortions in SBS based slow-light process mainly come from two aspects: filtering effect of the SBS gain and dispersion accompanied with the slow-light

Methods

Results

Conclusion