Phase-Coded Millimeter-Wave Waveform Generation Using a Spatially Discrete Chirped Fiber Bragg Grating

An all-optical approach to generating phase-coded millimeter-wave (mm-wave) waveforms based on optical pulse shaping, using a spatially discrete chirped fiber Bragg grating (SD-CFBG) is proposed and experimentally demonstrated. Since no electro-optical modulator is used, the system is simpler and less costly. In the proposed system, the spectrum of an optical pulse is spectrally sliced by a sinusoidal comb filter. The SD-CFBG is then used as a special dispersive element to map the shaped spectrum to a temporal waveform based on dispersive Fourier transform, and at the same time, to introduce the desired time delay jumps, which are translated to phase shifts. A simplified system without using the comb filter is also studied, in which a single SD-CFBG is employed to simultaneously perform spectral slicing, frequency-to-time mapping, and temporal coding. The proposed technique is validated by two experiments in which two phase-coded mm-wave waveforms at 28.5 GHz and 47.2 GHz with, respectively, a 7-bit and 11-bit Barker code are generated.