Wang Yutian, Xin Ronghuan, Fu Songnian, Tang Ming, Liu Deming
Opt Express. 2020 Mar 30;28(7):9642-9652. doi: 10.1364/OE.387560.
Although fruitful investigations of carrier phase estimation (CPE) have been conducted for a traditional coherent fiber optical transmission, there are few studies on the CPE for a nonlinear Fourier transform (NFT) based transmission. A laser linewidth induced phase noise leads to a phase rotation of the nonlinear spectra and the scattering data, which is similar to its effect on the linear spectra. Here, we first identify that both feed forward the M-th power, and the blind phase search (BPS)-based CPE can function well in the nonlinear frequency division multiplexing (NFDM) transmission with discrete spectrum modulation. Then, a performance comparison between two CPE schemes is presented for various modulation formats under the scenario of a single eigenvalue NFDM transmission. Our simulation results indicate that the laser linewidth tolerances of 2 GBaud quadrature phase shift keying (QPSK), 8-phase shift keying (8-PSK), and 16-amplitude phase shift keying (16-APSK) are 2.3 MHz, 1.05 MHz, and 250 KHz, respectively, given a 1-dB optical signal to noise ratio (OSNR) penalty at BER = 10. Finally, the BPS algorithm is experimentally verified under the same scenario of a 2 GBaud back-to-back transmission, due to the use of a semiconductor laser with a 100 KHz linewidth.
尽管针对传统相干光纤光传输已经开展了关于载波相位估计（CPE）的卓有成效的研究，但对于基于非线性傅里叶变换（NFT）的传输的CPE研究却很少。激光线宽引起的相位噪声会导致非线性谱和散射数据的相位旋转，这与其对线性谱的影响类似。在此，我们首先确定前馈第M次幂以及基于盲相位搜索（BPS）的CPE在具有离散谱调制的非线性频分复用（NFDM）传输中都能良好运行。然后，针对单特征值NFDM传输场景下的各种调制格式，给出了两种CPE方案的性能比较。我们的仿真结果表明，在误码率BER = 10时，1 dB光信噪比（OSNR）代价下，2 GBaud正交相移键控（QPSK）、8相移键控（8-PSK）和16幅度相移键控（16-APSK）的激光线宽容限分别为2.3 MHz、1.05 MHz和250 KHz。最后，由于使用了线宽为100 KHz的半导体激光器，在2 GBaud背靠背传输的相同场景下对BPS算法进行了实验验证。
