With large-scale new energy generation plants and multi-infeed HVDC transmission becoming involved in the grid, the development of AC and DC power grids has higher requirements on the scale of power system simulation. The current main method to expand the scale of simulation is to use customized proprietary protocols to form a SGI high-performance computer cluster. However, the method of expanding simulation resources through direct interconnection is limited by the number of hardware interfaces of the SGI-customized inter-machine communication device, and is also limited by the incompatibility of new and old versions of the communication protocol. In order to solve this problem, this paper proposes a decoupled line interface model based on the communication interface of the universal transparent protocol and the waveguide equation, using the OP5607 optical fiber interface and Aurora protocol. Two sets of different versions of SGI are jointly simulated through decoupling lines. The results verify its feasibility. Finally, engineering verification is carried out on the Yu-E engineering model. This work is supported by the Science and Technology Project of State Grid Corporation of China “Research on Real-time Simulation Method of Large-scale Power Grid Cross-platform Electromagnetic Transient State”.