Noise reduction of 20 Gbit/s pulse train using spectrally filtered optical solitons

Abstract

The ‘particle-like’ nature of optical solitons is attractive for realizing several types of optical functionality. The application of solitons to long distance optical transmission has been studied intensively [1]. On the other hand, optical solitons are also useful for realizing optical signal processing, such as all-optical switching. Recently, photon number squeezing has been demonstrated by spectrally filtering of the pulses whose energy is slightly larger than that of the fundamental soliton [2]. It is not easy to take advantage of the sub-Poissonian state generated by squeezing in real optical transmission systems at present because of the intrinsic finite noise figure of the widely used Er3+ doped fiber amplifier (EDFA). However, the spectrally filtered soliton scheme should be useful for reducing noise caused by intersymbolic interference or amplified spontaneous emission (ASE) in EDFAs. In this paper, we demonstrate that the spectrally filtered soliton scheme is effective in improving the signal to noise ratio in optical communication equipment.