Apparatus and method for effecting data transfer between data systems

An apparatus for effecting data transfer between data systems comprising:

• a first transceiver having an input for receiving digital data from one of the data systems, an output for serially outputting digital data to the one of the data systems, at least one transmitter comprising a primary and a secondary transmitter for serially converting digital data received at the data input into optical signals, at least one receiver comprising a primary and secondary receiver for receiving optical signals and serially converting the received optical signals into digital data for output to the first transceiver output, the first transceiver further comprising detector circuitry for detecting the level of light of the optical signals received by the primary receiver of the transceiver, the detector circuitry outputting a control signal having a first state indicating the level of light of the received optical signals is above a predetermined threshold and a second state indicating the level of light of the received optical signals is below a predetermined threshold;
• a second transceiver having an input for receiving digital data from another one of the data systems, an output for serially outputting digital data to the another one of the data systems, at least one transmitter comprising a primary and secondary transmitter for serially converting digital data received at the input of the second transceiver into optical signals, at least one receiver comprising a primary and secondary receiver for receiving optical signals and serially converting the received optical signals to digital data for output to the second transceiver output, the second transceiver further comprising detector circuitry for detecting the level of light of the optical signals received by the primary receiver of the second transceiver, the detector circuitry outputting a control signal having a first state indicating the level of light of the received optical signals is above a predetermined threshold and a second state indicating the level of light of the received optical signals is below a predetermined threshold;
• an optical link connecting the first and second transceivers, the optical link optically linking the transmitter of the first transceiver to the receiver of the second transceiver and optically linking the receiver of the first transceiver to the transmitter of the second transceiver, the optical link comprising optical fibers that optically link the primary transmitter and primary receiver of the first transceiver to the primary receiver and primary transmitter, respectively, of the second transceiver, and optically link the secondary transmitter and secondary receiver of the first transceiver to the secondary receiver and secondary transmitter, respectively, of the second transceiver;
• and
• selection circuitry for selecting a first mode of operation wherein the primary transmitter of one transceiver and the primary receiver of the other transceiver transfers data between the data systems, or a second mode of operation wherein the secondary transmitter of one transceiver and the secondary receiver of the other transceiver transfers data between the data systems, the selection circuitry being responsive to the control signals outputted by the detector circuitry such that the selection circuitry selects the first mode when the control signal outputted by the detector has a first state and selects the second mode when the control signal has the second state.