Coherent LiDAR concepts for automotive or unmanned aerial vehicle (UAV) applications are of increasing interest due to their superior performance compared to standard pulse-based systems, especially at longer range. Proposed scanning methods include bulky and slow galvanometer- or polygon scanners that are often impractical for implementation in cars or UAVs. Here, micro-electro-mechanical-system (MEMS) mirrors can be used as an alternative compact scanning device. To merge the advantages of coherent LiDAR technology with the advantages of miniaturized scanning by MEMS mirrors, we present fiber-based frequency modulated continuous wave (FMCW) LiDAR point cloud generation using quasi-static MEMS mirrors. The unique feature of quasi-static MEMS mirrors is their ability to perform a point-to-point scanning and measurement process, while most conventional MEMS mirrors scan the scene continuously. Hence, they enable a compact monostatic system design. We demonstrate the operation of such a system for the first time, to the best of our knowledge. Here, we show the operating principle and design of those quasi-static MEMS mirrors. We also implement and test the generation of the mirror scan pattern using a digital IIR (infinite impulse response) filter method. Lastly, we show the LiDAR point cloud generation in an indoor environment and evaluate the point cloud output for different MEMS mirror sizes, angular resolutions, and ranges.
In this paper, we perform a comparison of three modulation formats: NRZ, duo binary and DMT in combination with the state of the art 850 and 910nm VCSELs for their application in short reach high speed optical links. The system for NRZ and DB utilizes feasible for deployment equalization including a 9-tap finite impulse response filter and raised cosine filtering in the transmitter and a 7-tap UI-spaced feed forward equalizer in the receiver. The 100 Gbit/s net link with DB modulation can be realized without applying receiver equalization. For DMT the highest gross data rate of 224 Gbit/s/lambda is achieved.
KEYWORDS: Analog electronics, Multiplexers, Telecommunications, Digital signal processing, Signal processing, Modulators, Clocks, Linear filtering, Signal to noise ratio, Multiplexing
In today’s fiber-optic communication systems, the bandwidth of the photonic components, i.e. modulators and photo diodes, is way greater than that of their electrical counterparts, i.e. digital-to-analog converters (DACs) and analog-to-digital converters (ADCs). In order to increase the transmission capacity, the bandwidth limitations need to be overcome. We review the progress and the recent results in the field of high-speed DACs, which are desirable for software-defined transmitters. Furthermore, we evaluate interleaving concepts regarding their ability to overcome the above mentioned limitations and demonstrate recent experimental results for a bandwidth interleaved DAC with 40 GHz analog electrical bandwidth.
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