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.
"A photonic microwave temporal differentiator could be achieved based on PM and PM-IM conversion in an FBG serving as a frequency discriminator , . A temporal differentiator using other schemes such as the XGM  and the XPolM  in a SOA has also been reported. "
[Show abstract][Hide abstract] 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.
"First-order and higher order differentiators of complex optical signals have been successfully demonstrated –; coherent differentiation has shown to be of scientific and practical significance for a wide range of applications, including generation of high-order Hermite–Gaussian pulse waveforms –, ultrashort pulse shaping –, and direct phase reconstruction of arbitrary optical signals –. On the other hand, incoherent photonic differentiators, operating on intensity time waveforms, have proven particularly useful for ultrawideband (UWB) microwave signal generation and processing –, –. These last types of photonic differentiators can be considered as a direct all-optical equivalent to conventional electronic temporal differentiators since amplitude-only signals are actually processed in the electronic domain. "
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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 · 1.23 Impact Factor
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