STRAIN MEASUREMENT SYSTEM USING DOUBLE-PASS MACH-ZEHNDER INTERFEROMETER AND FIBER GRATING SENSOR

摘要

A strain measurement system using a double-pass mach zehnder interferometer and a fiber grating sensor are provided to sample phase difference at the intervals of pi/2 regardless of the external influence by executing all measurement operations with one signal and to reduce the size by excluding an external trigger. A strain measurement system using a double-pass mach zehnder interferometer and a fiber grating sensor is composed of the mach zehnder interferometer having a first arm part(221) formed between first and second optical combining units(211,212) and a second arm part(222) having a phase modulation unit(223) modulating phase by using a phase modulation signal; a broad band source(201) outputting an optical signal to the first optical combining unit; a reflecting unit(240) connected to the second optical combining unit to reflect a portion of the signal outputted through the mach zehnder interferometer, to the mach zehnder interferometer again; a sensor grating unit(290) reflecting a signal with the specific wavelength of the signal outputted from the mach zehnder interferometer through the second optical combining unit; a first optical detecting unit(231) detecting a signal outputted from the sensor grating unit; a unidirectional waveguide unit(226) installed between the second optical combining unit and the sensor grating unit to prevent a signal reflected from the sensor grating unit from being transmitted to the second optical combining unit; a second optical detecting unit(232) detecting a signal reflected by the reflecting unit and outputted from the first optical combining unit through the mach zehnder interferometer; and a calculation unit(270) calculating strain by using phase change of the signal reflected from the sensor grating unit. The calculation unit executes sampling in a signal detected in the first optical combining unit, by using points where zero crossing is generated in the signal detected in the second optical combining unit.