基于复合衍射全息图的多路涡旋光解调技术

Demodulation for multi vortex beams based on composite diffraction hologram

将高斯光束入射到加载有复合衍射全息图的空间光调制器(spatial light modulator,SLM)上可一次生成多个涡旋光(optical vortex,OV);反之,将相应的涡旋光入射到相同全息图上,便可还原为高斯光,实现涡旋光的解调.由于传统的涡旋光通信系统中一个全息图只能解调一路入射涡旋光,故提出了一种基于复合衍射全息图的涡旋光解调法,该方法能利用一个全息图解调多路入射涡旋光,具有较好的应用前景.搭建了一个实验系统,实现了16QAMOFDM(quadrature amplitude modulation-orthogonal frequency division multiplexing,正交振幅调制-正交频分复用)光信号的涡旋光生成、传输和解调,将解调后的高斯光经过一系列离线处理得到了OFDM信号的星座图和各个子载波的误码率.实验结果表明,所有子载波的误码率均在前向纠错(forward error correction,FEC)门限之下,说明该方法具有良好的系统性能.

When projecting a Gauss beam onto the spatial light modulator （SLM） loaded with a composite hologram, several vortex beams are generated simultaneously. On the contrary, when projecting the corresponding vortex beam onto a hologram, the Gauss beam can be restored, realizing demodulation of the vortex beam. Traditionally, a hologram can only demodulate one incident vortex beam. In this paper a vortex beam demodulation method based on composite diffraction hologram that can demodulate several incident vor- tex beams with only one hologram is proposed, thus having a good chance of applications. An experimental system is set up to achieve generation, transmission and demodulation of vortex beams with 16 quadrature amplitude modulationworthogonal frequency division multiplexing （QAM-OFDM） signals. After offiine processing on the demodulated Gauss beam, constellation and bit error rate of each subcarrier for OFDM signals are acquired. The experiment results show that the bit error rates of all subcarriers are below the forward error correction （FEC） threshold.