无论是光路交换还是光突发交换,都离不开有光开关矩阵组成的光交叉连接节点(OXC)。OXC节点是组建波分复用光网络的基本单元,OXC节点引入的串扰成为限制其投入实用的主要原因。理论分析了基于扩展Benes(DB)结构和改进扩展Benes(GMDB)结构的三种典型OXC结构中的带内串扰,结果表明基于DB结构和GMDB结构的OXC节点可以完全消除低于二阶的各类串扰。数值模拟了基于两种结构的OXC节点中带内串扰的积累特性,发现基于GMDB结构的OXC节点能大大降低串扰引起的功率代价,实验测量了8×8DB结构和GMDB结构中串扰的影响,实验结果证实了GMDB结构的低串扰特点。同时与基于DB结构的OXC节点相比,基于GMDB结构的OXC节点对光开关串扰系数的要求放宽了5 dB,大大降低了对光开关隔离度的要求。

Optical cross-connects (OXCs) are key elements in all-optical WDM networks. OXC nodes generally consist of demultiplexers (DMUXs), space switching networks and multiplexers (MUXs). These nonideal devices give rise to signal leakage to the unintended channels and lead to the generation of crosstalk. Optical crosstalk imposes a major limit to the practical implementation of optical cross-connects. Intraband crosstalk characteristics of OXC composed by dilated Benes (DB) network and generally modified dilated Benes (GMDB) network are studied. Results show that OXC composed by DB and GMDB network can remove first order crosstalk successfully. At the same time, the power penalty induced by intraband crosstalk is studied by numerical simulation. Compared with DB network, GMDB network can eliminates crosstalk effectively. Simulations have been followed by experimental measurements. Experiments have confirmed and highlighted the beneficial effect of realizing OXCs architectures with GMDB networks. The crosstalk level of optical devices required in GMDB network is about 5 dB lower than that in DB network to keep the power penalty below 1 dB at the bit error rate of 10-9.