采用NPRO光源的零差相干光通信实验

Experiments on homodyne coherent optical communication with NPRO as light sources

在空间相干光通信应用中,针对传统激光器线宽较宽、相位噪声大、易导致锁相环路失锁的问题,研制了单频Nd:YAG非平面环形(NPRO)激光器,其线宽小于1 k Hz,相对强度噪声(RIN)低于-150 d B/Hz,具有窄线宽、低噪声的特点。搭建了光锁相环路,在信号光功率-67 d Bm的情况下实现了两台NPRO激光器的相位锁定。在此基础上开展了信号频率为10 MHz和1.25 GHz的模拟通信实验,在信号光功率分别为-60 d Bm和-53 d Bm时可观测到较理想的眼图。在2.5 Gbps数字通信实验中,接收灵敏度达到-50 d Bm,此时误码率为3.2×10-6。系统灵敏度可接近量子极限,明显优于传统的IM/DD方式,是一种适合长距离、大容量传输的空间通信方式。

In the application of coherent space optical communication, traditional lasers have the problems of wide linewidth and severe intensity noise, which tends to lead to losing lock of phase locking loop. Single-frequency Nd：YAG non-planar ring oscillators （NPROs） were developed, with linewidth smaller than 1 kHz and relative intensity noise （RIN） lower than -150 dB/Hz. An optical phase locking loop was constructed and phase locking of two NPRO lasers was realized with -67 dBm signal laser power. The analog communication experiment was conducted at the signal frequency is 10 MHz and 1.25 GHz. When the signal light power is -60 dBm or -53 dBm, respectively, relative ideal eye diagram could be observed. In the digital communication experiment, the receiver sensitivity is -50 dBm at 2.5 Gbps transmission rate, the bit error （BER） is 3.2 ×10^-6. System sensitivity of quantum limit could be approached, which is much better than that in traditional IM/DD mode. This performance is suitable for long distance, large capacity space communication.