In their early days, submarines were isolated from centralized command centers. Communications capabilities connecting them to command-and-control systems have made consistent improvements and, most recently, China has used inductive coupling and underwater acoustic communication technologies to boost real-time high-capacity data sharing between deep ocean transponders and satellite systems. One scientist who worked on the projected reported that “this technology…significantly increases the safety, independence and reliability of deep ocean data transmission. The transponder…at a depth of 6,000 meters, has been safely in operation for more than a month now and it is working well.” Once adjusted and developed, this technology would prove highly valuable for nuclear submarines, where current communications, at least those that do not easily give away positions, are extremely limited. 

Source: Chinese scientists make progress on nuclear submarine communication | South China Morning Post