Abstract

The generation of flat-top (square-like) temporal waveforms is highly desired for a range of non-linear optical switching and frequency conversion applications, of specific interest for optical communications [1]. From the practical point of view, all-fiber technologies offer the key advantages of simplicity, low insertion loss, compactness and full compatibility with fiber optics systems. Flat-top temporal pulses were already generated using all-fiber technologies using, e.g., fiber Bragg gratings (FBGs) [1]). FBG devices generally serve as linear filtering devices to re-shape an input Gaussian-like optical pulse into a pulse with sinc-like spectral characteristics. Recently, we suggested a new principle for flat-top pulse generation that is based on optical differentiation [2]. We implemented this technique using a long- period fiber grating (LPG), which allows for the flat-top generation in the picosecond and sub-picosecond regimes [2], (Sub-)picosecond flat-top temporal pulses are sensitive to dispersion, especially due to their large bandwidth. In addition, they may suffer from non-linear interactions when propagated through a low-dispersion material (e.g., zerodispersion optical fiber). Thus, some dispersion management, in which the light propagates through regions of relative high positive and negative dispersion, is needed to deliver these pulses to a desired distant point (from the generation point) using, e.g., optical fibers. However, existing compensation techniques increase complexity of the set-up (e.g., chirped Bragg gratings) or give rise to additional, detrimental non-linear effects (e.g., dispersion compensating fibers).

© 2007 IEEE