Free space optical communication is plagued by interruptions in the connections caused by atmospheric phenomena, such as weather. A wireless beam transmission system includes at least one transmitter (110) and accommodates several wavelengths, and at least one transmission wavelength is arranged to be chosen based on spectral absorption measurements of the atmosphere in the carrier beam path of communication. The invention concerns also a transceiver for repeating wireless optical communication signals. The long range and high reliability of spectroscopically sensitive light beams at a penetrating frequency allow the affordable provisioning of high bandwidth optical or IR communication connections to devices and buildings that were previously either very expensively connected to the fiber optic backbone networks, expensive low bandwidth radio or microwave networks, or unreachable by traditional free space optics solutions.