Precoding-enabled OFDM-ROF transmission system with self-pumping structure

Precoding-enabled orthogonal frequency division multiplexing (OFDM) is proposed in radio-over-fiber (ROF) system based on a flexible self-pumping structure. Different from the use of two lasers, one laser-driven Mach-Zehnder modulator generates multiple spectra and forms self-pumping structures by selecting signal and pump light, which can effectively reduce the system cost and eliminate the laser phase conversion noise. The signal-to-noise ratio (SNR) of OFDM-ROF fluctuates wildly induced by non-ideal frequency response of optical/electrical devices and channel fading effects, and the BER performance is severely deteriorated. Therefore, seven common channel-independent precoding techniques are used and evaluated for the OFDM-ROF systems. The analysis of the results shows that seven precoding techniques can equalize uneven SNR on data subcarriers. Meantime, constant amplitude zero autocorrelation sequence-based matrix transform (CAZACT), Zadoff-Chu matrix trans-form (ZCT), discrete Fourier transform (DFT) have significant advantages in reducing the peak-to-average power ratio (PAPR). When the received optical power (ROP) is-3dBm, the BERs of the system under the seven pre -coding schemes are all lower than the hard decision -forward error correction threshold (HD-FEC). In addition, receiver sensitivity and comb flatness gain can also be achieved by the precoded OFDM compared to the con-ventional OFDM.