Methods for protecting data signals which are being transmitted via optical conductors are disclosed. At least one operational optical conductor set that is connected at both ends to optical switching devices is provided for the purpose of bi-directional transmission of the data signals. A stand-by optical conductor set is also connected at both ends to the optical switching devices. In the event of interference on at least one optical conductor of the operational optical conductor set, such as a signal failure determined at the receiving end, there is a switchover at the receiving end from the respective operational optical conductor set to the stand-by optical conductor set. Consequently, there is a signal failure at the opposite end, and immediately thereupon there is also a similar switchover at the opposite end to the stand-by optical conductor set.