ALL-OPTICAL FIBER SIGNAL-PROCESSING AND REGENERATION FOR SOLITON COMMUNICATIONS

Ultrafast all-optical signal processing techniques are expected to pla y a major role in future ultrafast single-carrier soliton systems, bec ause they remove the electronics bottleneck. In this paper, two all-op tical devices, the nonlinear optical loop mirror (NOLM) and the Kerr f iber modulator (KFM), are used to achieve major functions related to h igh bit rate soliton links. At the interface with existing networks, c onversions from data at the nonreturn-to-zero (NRZ) format to return-t o-zero (RZ) and soliton data, and vice-versa are required, These two c onversions are demonstrated through NOLM's, and their limitations inve stigated, However, the main part of this paper is devoted to in-line s oliton regeneration through synchronous modulation, Synchronous modula tion requires both clock recovery and inline optical modulation, In th e following, all-optical approaches for these two functions are consid ered separately, before being associated in a true all-optical regener ator, All-optical clock recovery techniques are first reviewed, An exp erimental implementation of one of these techniques is described, On t he other hand, all-optical modulation can be done either with intensit y or phase modulators. We initially proposed the NOLM as all-optical i ntensity modulator, We analyze it theoretically, both from the compone nt and the system application viewpoints. A modified configuration of the NOLM, having two optical controls, removes some limitations pertai ning to the single-control configuration, yielding even higher perform ance, The other all-optical synchronous modulator considered here is t he KFM, which is a pure phase modulator, Its potential is demonstrated in a 20-Gb/s soliton transmission experiment, when driven by an optoe lectronic optical clock generation device, Issues specific to the impl ementation of both types of all-optical fiber-based modulators are dis cussed. Finally, a true all-optical synchronous regenerator, combining all-optical clock recovery circuit and KFM, is tested in an actual so liton transmission experiment at 20 Gb/s.