Low-complexity frequency domain frame synchronization for short-reach IM/DD optical fiber transmission systems.

We propose a low-complexity frequency domain frame synchronization method for short-reach intensity modulation and direct detection (IM/DD) systems. A four-level pulse amplitude modulation-training sequence (PAM4-TS) is specially designed for the proposed method, which has an obvious peak in the amplitude spectrum that is higher than the normal signal. The proposed method comprises a coarse synchronization stage and a fine synchronization stage.

Compensation schemes for uneven illumination and LED light-emitting instability in optical camera communication system.

In order to increase the data rate of the optical camera communication (OCC) system, the 8-composite-amplitude-shift-keying modulation (8CASK) OCC system is used in this work. However, if the static decision thresholds are employed to demodulate multi-level ASK signal, uneven illumination of LED lamps and LED light-emitting instability lead to the fluctuation of the gray range in the picture and degrade the bit-error-rate (BER) performance. In this work, we propose and demonstrate a demodulation scheme, using the uneven illumination compensation algorithm, the pixel matrix threshold overall update algorithm and the secondary decision algorithm, to mitigate the impact of illumination unevenness and LED light-emitting instability.