Normally, you would use a separate fibre for transmit and receive, so two fibres for bi-directional transmission. You can purchase BiDi transceivers, which allow you to use a single fibre for both transit and receive. These transceivers use Wave Division Multiplexing and modulate the transmit and receive onto different wavelengths so that they do not interfere which each-other. An example of this would be Cisco SFP-10G-BXD-I or SFP-10G-BXU-I transceivers, which both allow for 10GBASE over a single strand of fibre.