Bidirectional control/sense signal transmission through optical fiber

A pair of signal transmission subsystems which share one optical fiber can be used to send the control signal from one site to the other and to send the response from the latter to the former. The control signal, consisting of multiple frequency signals, i.e. 200 kHz, 300 kHz, 400 kHz, 500 kHz, and 600 kHz, is generated and transmitted from the controller to a machine through the optical fiber. The response from the machine, which is given as a temperature in the range of 20°C to 70°C, or a DC voltage in the range of 0 to 5 V, is converted into a pulse frequency signal at 10 MHz (thermal data) or 1 MHz (voltage data) and then sent to the controller via the same optical fiber. The optical transmission system can be used for a home automation system or a factory control system, especially in an inferior operating environment