Chin Hou-Man, Thakur Manoj P, Thomsen Benn C, Savory Seb J
Opt Express. 2014 Oct 20;22(21):25506-15. doi: 10.1364/OE.22.025506.
The deployment of coherent transceivers in legacy networks requires significant investment in installation. We propose a method enabling autonomous (re-)configuration of an optical channel, which would be advantageous in legacy networks and necessary in proposed future networks utilizing a flexible frequency grid and software defined components such as reconfigurable optical add drop multiplexers (ROADM). We consider potential interfering optical channels propagating with the prospective channel along part of the fiber link which are dropped before arrival at the receiver. The method uses a commercially available line card transmitting a 40Gbit/s polarization multiplexed quadrature phase shift keying (PM-QPSK) probe channel to characterize an optical channel. The power of the nearest neighboring channels is then inferred by examining its bit error rate (BER) which is impacted by cross phase modulation (XPM) from the aggressor channels. In a 4 node network with 2 ROADMs using up to 6 aggressor OOK channels, we successfully deduce the neighboring channel power down to -2 dBm, and an extra improvement down to -3.5 dBm is gained, by measuring at an offset to the international telecommunication union (ITU) grid which also reveals inequality in neighbor channel powers.
在传统网络中部署相干收发器需要在安装方面投入大量资金。我们提出了一种能够对光信道进行自主（重新）配置的方法，这在传统网络中具有优势，并且在所提议的未来网络中是必要的，这些未来网络将利用灵活的频率网格和软件定义组件，如可重构光分插复用器（ROADM）。我们考虑了沿着光纤链路的一部分与预期信道一起传播的潜在干扰光信道，这些干扰信道在到达接收器之前被分插。该方法使用一块商用线路卡发送一个40Gbit/s的偏振复用正交相移键控（PM-QPSK）探测信道来表征一个光信道。然后，通过检查其受来自干扰信道的交叉相位调制（XPM）影响的误码率（BER）来推断最近邻信道的功率。在一个具有2个ROADM且使用多达6个干扰开关键控（OOK）信道的4节点网络中，我们成功地将相邻信道功率推断到-2dBm，并且通过在相对于国际电信联盟（ITU）网格的偏移处进行测量，还获得了额外的改进，使相邻信道功率降至-3.5dBm，这也揭示了相邻信道功率的不平等。
