FIELD: optics.
SUBSTANCE: invention relates to fibre optics. Method consists in the fact that probing pulses from a source of laser radiation of receiving-transmitting unit are fed into transport fibre and then to sensitive element, both ends of which are connected to splitter to form a loop from two identical opposite paths of shared part of the probing pulse power in the opposite direction. Pulses are passed through each other without interaction and sent to the input splitter in reverse direction. After splitter the separated pulses are summed up, and in the presence of phase shift between them pulses interfere with each other. Then pulses are directed to the receiving-transmitting unit at the same transport path in reverse direction, where returned pulses and conversion into digital code are measured. Dynamics of variation of laser pulses amplitude serve as a base for determining presence of exposure and its effect on the sensitive element. Part of the probing pulse power is controlled so that the returned signal does not exceed the maximum allowable level at the input of receiving-transmitting device.
EFFECT: possibility to use low-power part of the probing pulse tapped to sensitive element for producing clearly identified information on signals of reflection or return.
1 cl, 2 dwg
