Dispersive Fourier Transformation for Versatile Microwave Photonics Applications

Abstract: Dispersive Fourier transformation (DFT) maps the broadband spectrum of an ultrashort optical pulse into a time stretched waveform with its intensity profile mirroring the spectrum using chromatic dispersion. Owing to its capability of continuous pulse-by-pulse spectroscopic measurement and manipulation, DFT has become an emerging technique for ultrafast signal generation and processing, and high-throughput real-time measurements, where the speed of traditional optical instruments falls short. In this paper, the principle and implementation methods of DFT are first introduced and the recent development in employing DFT technique for widespread microwave photonics applications are presented, with emphasis on real-time spectroscopy, microwave arbitrary waveform generation, and microwave spectrum sensing. Finally, possible future research directions for DFT-based microwave photonics techniques are discussed as well

Modelling and Measurement of Diffraction Patterns to Characterize Next- Generation Optical Systems in CMB Cosmology

HonorsPhysicsUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/162636/1/josaitis.pd

Detection Schemes with Low-Resolution ADCs and Spatial Oversampling for Transmission with Higher-Order Constellations in the Terahertz Band

In this work, we consider Terahertz (THz) communications with low-resolution uniform quantization and spatial oversampling at the receiver side. We compare different analog-to-digital converter (ADC) parametrizations in a fair manner by keeping the ADC power consumption constant. Here, 1-, 2-, and 3-bit quantization is investigated with different oversampling factors. We analytically compute the statistics of the detection variable, and we propose the optimal as well as several suboptimal detection schemes for arbitrary quantization resolutions. Then, we evaluate the symbol error rate (SER) of the different detectors for a 16- and a 64-ary quadrature amplitude modulation (QAM) constellation. The results indicate that there is a noticeable performance degradation of the suboptimal detection schemes compared to the optimal scheme when the constellation size is larger than the number of quantization levels. Furthermore, at low signal-to-noise ratios (SNRs), 1-bit quantization outperforms 2- and 3-bit quantization, respectively, even when employing higher-order constellations. We confirm our analytical results by Monte Carlo simulations. Both a pure line-of-sight (LoS) and a more realistically modeled indoor THz channel are considered. Then, we optimize the input signal constellation with respect to SER for 1-bit quantization. The results show that the minimum SER can be lowered significantly for 16-QAM by increasing the distance between the inner and outer points of the input constellation. For larger constellations, however, the achievable reduction of the minimum SER is much smaller compared to 16-QAM.Comment: 14 pages, 19 figures, submitted for possible journal publicatio