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The authors demonstrate the use of cascaded uniform fiber Bragg gratings (FBGs) for the generation of periodic optical pulses with arbitrary waveform. It is a significantly simplified structure compared to complex FBG shapes. The pulse shaping is based on splitting of the input pulses by low-reflecting FBGs into a number of replicas and their superposition with proper amplitude, time delay, and phase shift that depend on the FBG parameters. The reflection amplitude and phase of each grating are unambiguously determined by the needed pulse shape. This method was experimentally verified for converting sinusoidally phase-modulated radiation of continuous-wave laser diode into a Gaussian pulse train with a pulsewidth of 30 ps. A method for controlling the parameters of FBGs during their fabrication process is also presented. It is done by measuring the spectral interference between the reflections from the FBGs and the fiber end by an optical spectrum analyzer and performing a fast Fourier transform. The method allows correction of the FBGs until the needed parameters are obtained during the writing process, as well as at any time after that. [ABSTRACT FROM PUBLISHER]

An interesting method for broadband arbitrary waveform generation is based on the frequency upshifting of a narrowband microwave signal. In this technique, the original microwave signal is imaged into a temporally compressed replica using a simple and practical fiber-based system. Recently, it has been shown that the conventional limitations of this approach (e.g., bandwidth limitations) can be overcome by exploiting a temporal self-imaging (Talbot) effect in fiber. This effect can be used whenever the signal to be imaged is a quasi-periodic waveform (e.g., microwave tones or any arbitrary periodic waveform). This paper provides a comprehensive study of the microwave frequency upshifting technique with special focus on the Talbot-based approach. Following a theoretical analysis of the design constraints of the conventional approach, the Talbot-based solution is theoretically investigated in detail. In particular, the design specifications of a Talbot-based microwave upshifting system are derived, and the practical capabilities and constraints of these systems (e.g., in terms of achievable bandwidth) are stated and examined. The theoretical findings are confirmed by means of numerical simulations. Moreover, a numerical study of the influence of higher-order (second-order) dispersion terms on system performance is presented, and some additional design rules to minimize the associated detrimental effects are given. The results show that microwave frequencies up to a few hundreds of gigahertz over nanosecond temporal windows can be easily obtained with the described technique using input optical bandwidths in the terahertz range. This has been experimentally confirmed. [ABSTRACT FROM PUBLISHER]

We derive an expression for the temporal fractional Talbot effect in delay lines with arbitrary orders of dispersion. We then demonstrate, experimentally and by numerical simulations, that a simple device consisting of a number of uniform fiber Bragg gratings or of waveguides can serve for such a tailored dispersive delay line for periodic optical pulses. The device produces temporally delayed and phase-shifted replicas of the original pulses, similarly to what happens in dispersive delay lines in the fractional Talbot effect. Such devices can be useful for compensation for the nonquadratic spectral phase of diode lasers, of dispersive elements in systems used for temporal imaging, real-time spectral analysis, and periodic pulse generation. [ABSTRACT FROM PUBLISHER]