Transmitter pre-emphasis is one of the techniques proposed to improve the relatively poor frequency responses of light-emitting diodes (LEDs) used in visible light communications (VLC) as light sources. However, according to the communications theory in linear channels, pre-emphasis may only be as good as the not particularly efficient feed-forward equalizer (FFE). Given the increase in peak-to-average power ratio (PAPR) caused by pre-emphasis, its use in place of receiver equalization can be considered counterproductive. In this study, we show that the performance of the transmitter pre-emphasis is indeed equivalent to the FFE at low input powers, where the LED is a linear system. However, at higher modulation voltages, the transmitter pre-emphasis has a clear advantage over FFE, as it mitigates the nonlinear distortion of the LED. This mechanism is for the first time to our knowledge explained in both theory and experiment.
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The increasing traffic of intra-data center networks creates an urgent demand for low-cost and high-speed intensity modulation/direct detection (IM/DD) transmission. In this Letter, we propose a joint scheme combining nonlinear lookup table (NL-LUT) pre-distortion, digital pre-emphasis (DPE), and a digital resolution enhancer (DRE) to achieve high-speed and low-cost IM/DD optical links using a low-resolution digital-to-analog converter (DAC). The NL-LUT and DPE are responsible for the system nonlinear impairments and channel attenuation at high frequency, respectively, while DRE handles the quantization noise (QN) caused by high peak-to-average ratios (PAPRs) and low-resolution DAC.
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View Article and Find Full Text PDFTransmitter pre-emphasis is one of the techniques proposed to improve the relatively poor frequency responses of light-emitting diodes (LEDs) used in visible light communications (VLC) as light sources. However, according to the communications theory in linear channels, pre-emphasis may only be as good as the not particularly efficient feed-forward equalizer (FFE). Given the increase in peak-to-average power ratio (PAPR) caused by pre-emphasis, its use in place of receiver equalization can be considered counterproductive.
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Sensors (Basel)
September 2023
State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, China.
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