Open-loop signal detecting method and device of an all-optical current transformer

The invention discloses an all-fiber current transformer open loop signal detection method which comprises the following steps: employing an asymmetric square wave with a period of 2t and an amplitude of Vpi/2 as a modulation signal, carrying out phase modulation on an optical signal, wherein the t is a transit time of the all-fiber current transformer; after the optical signal after phase modulation is subjected to interference, converting the optical signal into an electric signal; subjecting the electric signal to a sampling treatment; in a period 2t, calculating difference between sampling sum of electric signal positive half cycle and sampling sum of electric signal negative half cycle, defining a difference result as S1, defining sampling sum of the electric signal as S2, dividing S1 by S2, and defining a divide resultant as an open loop signal detection result of the all-fiber current transformer. An embodiment of the invention also discloses an all-fiber current transformer open loop detection apparatus. Since the asymmetric square wave is employed as a modulation signal, in a demodulation process, factors related to light source power and circuit gain in an interference output result are eliminated through a specific algorithm, thus the open loop signal detection result is only related to Faraday phase shift, and accuracy of a measuring result is raised.