Design of four-wave mixing frequency-shift-free amplitude regenerators

Abstract

Abstract-Frequency-shift-free all-optical amplitude regenerators based on fiber-four-wave mixing were investigated by means of simulations. These regenerators, comprised of two stages of highly nonlinear dispersion-shifted fiber, were designed using a heuristic procedure that implements a routine based on a genetic algorithm to optimize the device performance. A bit error rate improvement of up to four orders of magnitude was found as compared to a previous design approach discussed in the literature. It was due to a proper choice of the pump signal frequency regarding to the input signal that brings about a trade-off between four-wave mixing optical reshaping and four-wave mixing crosstalk leading to optimal optical regeneration. The proposed design method might be applied to other parametric devices that rely on four-wave mixing.Index Terms-optical regeneration, four-wave mixing, heuristic procedure, crosstalk. I. INTRODUCTIONOptical signals propagating along metropolitan area networks (MAN) may be significantly impaired by the accumulating effects of chromatic dispersion, fiber nonlinearities, and amplified spontaneous emission (ASE). Consequently, they will need to be regenerated, for example, during transmission or before interconnecting with other networks. MANs, because of their typical reaches and even for economic reasons [1], still benefit from using non-returning-to-zero on-off keying (NRZ-OOK) modulation format. Furthermore, researchers have been looking for all-optical regeneration strategies that are transparent to the bit rate. Notably, schemes that use nonlinear effects in dielectric media have attracted much attention [1-9], especially four-wave mixing (FWM) fiber-based regenerators [4][5][6][7][8][9]. Recently [7], it was experimentally demonstrated a FWM regenerator that exhibited significant amplitude and phase noise suppression for returning-to-zero differential shift keying (RZ-DPSK) signals. A parametric regenerator for 43 Gb/s returning-to-zero on-off-keying (RZ-OOK) signals, tunable over a 20 nm range, was implemented using a highly nonlinear dispersion shifted fiber (HNL-DSF) [8]. It has also been shown that a setup using FWM phase-sensitive design approach has not been yet reported in the literature and it is shown to be advantageous as compared to one discussed in [3]. The device stages were considered to be implemented with HNLDSFs. Finally, we observe a frequency-shift-free regenerator would prevent any network management concern regarding transmission channel reallocation, since the device maintains the input signal carrier. II. FUNDAMENTALS OF 2R ALL-OPTICAL REGENERATION A. S-like Transfer FunctionAll-optical reshaping and reamplification (2R All-Optical Regeneration) of NRZ-OOK signals rely on the implementation of an S-like optical power transfer function ( Fig. 1) in a device (regenerator).As far as the input signal noise amplitude does not exceed the lower (A) or higher (B) transfer function steps, the regenerator will output a reshaped version of the original signal. Many dif...

Contribution to the Study of 2R Regenerators in Optical Transmission Link into Account the PMD

“…There are three 2R regeneration modes: 2R regeneration self-phase modulation (SPM), 2R regeneration cross-phase modulation (XPM), and 2R regeneration four-wave mixing (FWM) [23][24]. In the following sections we are only interested in the first two types of regeneration.…”