We demonstrate reconfigurable and tunable flat-top microwave photonic filters based on an optical comb source and a dispersive medium. Complex taps allowing flexible and tunable filter characteristics are implemented by programming the amplitude and phase of individual comb lines using an optical line-by-line pulse shaper. First, we implement a flat top filter by applying positive and negative weights across the comb lines, then tune the filter center frequency by adding a phase ramp onto the tap weights.
We present a programmable multitap microwave photonic filter with an arbitrary phase response operating over a broad bandwidth. Complex coefficient taps are achieved by optical line-by-line pulse shaping on a 10 GHz flat optical frequency comb using a novel interferometric scheme. Through high-speed real-time measurements, we demonstrate programmable chirp control of a waveform via phase filtering. This achievement enables us to compress broadband microwave signals to their corresponding bandwidth-limited pulse duration.
Microwave photonic filters with arbitrary phase response can be achieved by merging high-repetition-rate electro-optic frequency comb technology with line-by-line pulse shaping. When arranged in an interferometric configuration, the filter features a number of programmable complex-coefficient taps equal to the number of available comb lines. In this work, we use an ultrabroadband comb generator resulting in a microwave photonic phase filter with >100 complex-coefficient taps. We demonstrate the potential of this filter by performing programmable chirp control of ultrawideband waveforms that extend over long (>10 ns) temporal apertures. This work opens new possibilities for compensating realistic linear distortion impairments on ultrabroadband wireless signals spanning over dozens of nanosecond temporal apertures.
A new simple method to obtain real-time high-resolution three-dimensional (3D) images based on a static unitary detector (STUD) is reported. The STUD consists of a common bias network, a partitioned photodetector, a preamplifier array and a combiner, which makes it possible to easily increase the effective photo-detection area for a wider 3D image acquisition without affecting the ability to detect short laser pulses for high-resolution 3D images. From an implemented experimental prototype based on a STUD, the intensity and 3D images with a very high resolution (320 pixels × 240 pixels) were obtained. The achieved range resolution and the spatial resolution of remote 3D objects at 50 m were measured to be <0.3 and 1.1 cm, respectively.
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