Abstract: A first photodetector is interconnected with a control unit equipped with a communication interface and powered by a power supply module. An output of a first optical filter is connected to an input of a first photodetector via a second optical filter, while a second output of the second optical filter is connected to an input of a second photodetector. An output of the second photodetector is connected to a control unit. A split branch of a third directional coupler is connected to the input of a third photodetector, the output of which is connected to the control unit. A split branch of a fourth directional coupler is connected to the input of a fourth photodetector, the output of which is connected to the control unit.