Which of the following is NOT an exchange medium for Link 11B?

The correct choice reflects that radio is indeed a fundamental medium for Link 11B communications. Link 11B is a tactical data link used for sharing situational awareness and command and control information among military forces. It primarily utilizes radio waves for its operations, allowing for real-time data exchange across various platforms.

The other mediums listed, such as fiber optics, satellite, and infrared, do not typically serve as exchange media for Link 11B. Fiber optics can be used in other communications systems due to its high bandwidth and resistance to electromagnetic interference, but it is not relevant to Link 11B. Satellite communications may serve other systems that require long-range capabilities but are not associated with Link 11B's operational design. Infrared is more commonly used in targeting and sensor applications rather than as a medium for tactical data links like Link 11B.

This context clarifies that the primary mechanism for Link 11B is indeed radio, making it the correct answer as it highlights the key role of radio in the functionality of Link 11B compared to the other options.