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We propose and validate experimentally a time-delay to intensity mapping process based on second-order optical integrators. This mapping provides dynamic control of the intensity modulation profile of a waveform based on a purely passive and linear process. In particular, we can realize linear intensity control by tuning the time-delay between two optical pulses launched into a second-order optical integrator. We suggest and experimentally prove the use of this mapping process for reconfigurable optical arbitrary waveform generation.

In this paper, a photonic temporal integrator based on an active Fabry-Perot (F-P) cavity is proposed and theoretically investigated. The gain medium in the F-P cavity is a semiconductor optical amplifier (SOA) with high gain coefficient. Key feature of the proposed photonic integrator is that the length of integration time window is widely tunable and could be ideally extended to infinitely long when the injection current is approaching lasing condition. Based on an F-P cavity with practically feasible parameters, a photonic temporal integrator with an integration time window of 160 ns and an operation bandwidth of 180 GHz is achieved. The time-bandwidth product of this photonic temporal integrator is 28,800, which is about two-orders of magnitude higher than any previously reported results. Gain recovery effect has been also considered and analyzed for the impact on performance of the photonic integrator, followed by the simulation results of the impact of gain recovery.

A superluminal space-to-time mapping process is reported and numerically validated in grating-assisted (GA) co-directional couplers, e.g. fiber/waveguide long-period gratings (LPGs). We demonstrate that under weak-coupling conditions, the amplitude and phase of the grating complex apodization profile of a GA co-directional coupling device can be directly mapped into the device's temporal impulse response. In contrast to GA counter-directional couplers, this mapping occurs with a space-to-time scaling factor that is much higher than the propagation speed of light in vacuum. This phenomenon opens up a promising new avenue to overcome the fundamental time-resolution limitations of present in-fiber and on-chip optical waveform generation (shaping) and processing devices, which are intrinsically limited by the achievable spatial resolution of fabrication technologies. We numerically demonstrate the straightforward application of the phenomenon for synthesizing customized femtosecond-regime complex optical waveforms using readily feasible fiber LPG designs, e.g. with sub-centimeter resolutions.

We introduce a universal figure of merit to evaluate the processing speed (operation bandwidth) performance of arbitrary-order optical differentiators. In particular, we define the maximum-to-minimum bandwidth ratio (MMBR) as a main figure of merit of these devices, which essentially informs about the broadness of the acceptable input pulse bandwidth range. We derive and numerically confirm a general analytical expression for the MMBR of an arbitrary optical differentiator, showing that this can be expressed simply as a function of the differentiator's amplitude resonance depth. The device MMBR can be improved by increasing the filter's resonance depth, depending also on the differentiation order; in particular, the MMBR quickly deteriorates as the differentiator order is increased. In our analysis, photonic differentiators are considered in two main groups, namely (i) non-minimum phase and (ii) minimum phase optical filtering implementations. The derived analytical expression for the device MMBR is generalized for these two different solutions, and the validity of the obtained analytical estimates is verified through numerical simulations, including results for the cases of 1st-, 2nd-, and 3rd-order differentiators.

We propose and experimentally demonstrate asynchronous optical differential phase-shift-keying (DPSK) pattern recognition using a fully reconfigurable technique. The proposed method uses optical phase-to-bipolar intensity conversion through all-optical differentiation in conjunction with an incoherent time-spectrum convolution system where the pattern to be recognized is implemented directly in the spectral domain through optical amplitude-only linear filtering. Full reconfigurability in terms of bit rate, pattern sequence, and pattern length is achieved using electronically programmable optical filters. We demonstrate dynamically switching recognition of different 64 bit patterns in a continuous 12 Gb/s DPSK pseudorandom optical bit stream with contrast ratio up to 3.8 dB.