This repeater is intended to be used for TETRA indoor optical fibre systems. It is a compact and reliable unit, and it is especially advantageous to use it in areas where off-air transmission is not preferable. The base station side optical master unit can control and monitor the slave unit on the remote repeater side through the optical fibre. In order to provide redundancy, the slave has two independent optical connectors, and it can automatically switch between optical links, if it senses that one link is better than the other, based on user-defined conditions. This very economical solution can be installed easily, and the repeater can be monitored and controlled using the provided remote-control software.