All-optical differentiator and high-speed pulse generation based on cross-polarization modulation in a semiconductor optical amplifier.
ABSTRACT We propose an all-optical intensity differentiation scheme based on cross-polarization modulation (XPolM) in a semiconductor optical amplifier (SOA) while demonstrating the absolute value of differential signal that can be obtained by the SOA-based XPolM of two parts with relative delay from the input signal and well extracted by the polarization filter. The differentiation errors and eye diagrams versus sampling time Delta are investigated for data rate at 12.5 Gbits/s, and the minimal error approximately 0.06 is achieved at Delta=0. Owing to a much faster polarization response, our scheme bears great potential for all-optical signal processing over 100 Gbits/s. By application of the differentiator, we further obtain the 20 GHz short pulse train with a pulse width of approximately 10 ps.
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ABSTRACT: A microwave bandpass differentiator implemented based on a finite impulse response (FIR) photonic microwave delay-line filter with nonuniformly-spaced taps is proposed and experimentally demonstrated. To implement a microwave bandpass differentiator, the coefficients of the photonic microwave delay-line filter should have both positive and negative coefficients. In the proposed approach, the negative coefficients are equivalently achieved by introducing an additional time delay to each of the taps, leading to a π phase shift to the tap. Compared with a uniformly-spaced photonic microwave delay-line filter with true negative coefficients, the proposed differentiator features a greatly simplified implementation. A microwave bandpass differentiator based on a six-tap nonuniformly-spaced photonic microwave delay-line filter is designed, simulated, and experimentally demonstrated. The reconfigurability of the microwave bandpass differentiator is experimentally investigated. The employment of the differentiator to perform differentiation of a bandpass microwave signal is also experimentally demonstrated.Journal of Lightwave Technology 11/2011; 29(22):3470-3475. DOI:10.1109/JLT.2011.2169939 · 2.86 Impact Factor
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ABSTRACT: A reconfigurable photonic signal processing system for arbitrary-order temporal differentiation of broadband microwave waveforms, with bandwidths up to a few tens of gigahertz, is proposed and experimentally demonstrated. This technique enables full programmability of the differentiation operator to be applied on the input microwave signal, including any desired linear differential-equation operator, by suitably reshaping the incoherent power spectrum according to the corresponding finite-difference time-domain (FDTD) equations obtained from the Euler's approximation. Successive photonic time derivatives of Gaussian-like pulse intensity waveforms with pulse widths of 42 and 72 ps were accurately achieved up to the second and the fourth order, respectively, using the same photonic processing platform. A more general operator, conceived to directly emulate the second-order differential-equation modeling a high-frequency series resistor, inductor, and capacitor (RLC) circuit, was also implemented and successfully tested.IEEE Photonics Journal 01/2011; DOI:10.1109/JPHOT.2010.2091115 · 2.33 Impact Factor
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ABSTRACT: In this paper, a method for generating ultra-short optical pulses in the sub-picosecond regime is presented and numerically demonstrated using a nonlinear nanoporous silicon waveguide followed by a Mach-Zehnder interferometer configuration based on the GaInP photonic crystal waveguide. Research results show that an optimal output pulse with sub-picosecond time duration can be achieved from ~16.65-ps input pulses by selecting suitable system parameters such as initial intensity and waveguide length which will significantly influence the optical properties of the output pulse, including its time domain waveform, frequency spectrum, and phase chirp. The time duration of the corresponding autocorrelation trace can also reach as little as ~1.0-ps at the end of the device.The European Physical Journal D 12/2011; 65(3). DOI:10.1140/epjd/e2011-20376-8 · 1.40 Impact Factor