Optical generation of linearly chirped microwave pulses using fiber Bragg gratings

Photonic generation of low phase noise arbitrary chirped microwave waveforms with large time-bandwidth product

“…Compared with the conventional electrical approaches, photonic techniques, benefiting from the intrinsic advantages of modern photonics such as ultra-high bandwidth, high-speed, compactness, and electromagnetic interference immunity [13,14], are promising approaches for generating low phase noise and broadband frequency-chirped MW and sub-THz signals. Many photonic techniques aiming at the generation of chirped signals have been proposed and demonstrated during the past few years [15][16][17][18][19][20][21]. One most popular method is based on the heterodyne beating between two optical carriers of different frequency sweeping features.…”

“…One most popular method is based on the heterodyne beating between two optical carriers of different frequency sweeping features. Such optical carriers can be produced through various approaches such as underlying their corresponding dispersive elements with different dispersions [18][19][20] or directly from two independent frequency-swept lasers of varied wavelengths [21]. However, for the former approach, the especially fabricated dispersive elements impair the tunability and flexibility in terms of arbitrary waveform, time-bandwidth product, chirp rate and temporal duration, while for the latter approach, besides the compromise among chirp rate and bandwidth, the uncorrelated noises characteristic and the instability of the independent carriers lead to drastically deterioration in noise performance.…”

Photonic analog-to-digital conversion and photonic microwave signal generation

“…Over the last two decades, there has been considerable interest in developing Early photonic techniques to generate high frequency CW microwave signals include optical heterodyning [59][60][61][62][63], external modulation [64][65][66][67][68][69][70] and dualwavelength laser [71][72][73][74][75][76]. As for arbitrary waveform generation, the popular photonic techniques include direct space-to-time (DST) pulse shaping [77][78][79], temporal pulse shaping [80][81][82][83], optical line-by-line pulse shaping [84][85][86][87], and lastly, optical spectral shaping and wavelength-to-time mapping [88][89][90][91][92][93]. A detailed discussion on the generation of CW microwave signals as well as generation of arbitrary waveform can be found in [1] and [94], respectively.…”

“…Among the four widely-used techniques depicted earlier in Fig. 1.5, the optical spectral shaping and wavelength-to-time mapping technique has shown much flexibility in generating chirped microwave signals whose centre frequency and/or chirp rate can be tuned [90][91][92][93]. Moreover, this technique does not require any modulators, microwave sources, microwave filters and it offers higher potential for integration as compared to the other three techniques.…”

“…An early demonstration of the above technique involved the use of two linearlychirped FBGs (LCFBGs) with different chirp rates in an unbalanced Mach-Zehnder Interferometer (MZI) as an optical spectral-shaper [90]. The major limitation of this approach is that the LCFBGs, once fabricated, are not reconfigurable and, as a result, the chirp rate is not tunable.…”