Abstract
In this paper, we present a time domain method for extracting coefficients of nonlinear Volterra-series kernels for white light-emitting diodes (LED) used both for illumination and visible light communications. We show that this method may have several advantages over the thus far more popular frequency domain method. We successfully apply the measured kernel coefficients up to the 3rd order for the modeling of nonlinear distortion impact on advanced modulation formats: pulse amplitude modulation, carrierless amplitude phase and orthogonal frequency division multiplexing. The impact of blue filtering on dynamic nonlinearity is also presented.
Highlights
Light-Emitting Diode (LED) communication is an attractive and low-cost solution for free space communication systems [1] and transmission in polymer optical fibers (POF) [2]
Unlike inter-symbol interference (ISI), nonlinearity cannot be overcome by well-established methods of linear equalization and may become the major transmission rate limiting factor, especially for spectrally efficient advanced modulation formats, which require a high signal-to-noise ratio (SNR) at the receiver
The choice of the roll-off is a tradeoff between spectrum flatness, total symbol duration and peak to average power ratio (PAPR), which increases for lower roll-off values
Summary
Light-Emitting Diode (LED) communication is an attractive and low-cost solution for free space communication systems [1] and transmission in polymer optical fibers (POF) [2]. Both solutions impose either power or noise enhancement penalties [5,6] This problem is avoided in the second kind of lighting LED, which consists of three or more chips of different colors (e.g., RGB). Regardless the LED type, LEDs are nonlinear devices, i.e., the emitted optical signal power a nonlinear function of the modulating current. This nonlinearity can have both static and dynamic characteristics. Unlike inter-symbol interference (ISI), nonlinearity cannot be overcome by well-established methods of linear equalization and may become the major transmission rate limiting factor, especially for spectrally efficient advanced modulation formats, which require a high signal-to-noise ratio (SNR) at the receiver. The Volterra model has already been used for LED nonlinearity identification [9,10,11] and has successfully been applied to LED nonlinearity compensation for single-carrier [12] and multicarrier modulation formats [13]
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