Abstract: Exemplary embodiments of a communication system for a power electronic converter with a plurality of converter modules includes controllable power semiconductor switches and individually mountable onto a converter cabinet or frame. The communication system includes unguided transmission of optical signals between optical elements arranged on a converter module and on the converter cabinet, respectively. The communication system provides a free-space optical signal transmission between two distinct parts of the converter that combines the flexibility offered by radio transmission and the data rate and reliability of optical communication, while at the same time avoiding the complex and expensive cabling of optical fiber solutions.