| 摘要 |
PURPOSE:To make it possible to perform detection highly sensitively, by synthesizing the signals which are the results of the amplitude modulation of the light beams that have passed through a pair of light transmitting paths, making the synthesized output zero, and detecting the change in the conditins of the physical environment on the light transmitting paths based on the change in the synthesized output. CONSTITUTION:Optical fiber paths 4 and 5 are connected by photo coupler 7. Light from a light source 2 is modulated by a signal (a) from a modulator 1. The modulated photo signal is split and inputted to the optical fiber paths 4 and 5. At this time, a photo attenuator 6 is adjusted and the length of the optical fiber path 5 is adjusted. The two signals are made to pass the optical fiber paths 4 and 5, combined in the photo coupler 7, and detected by a detector 8. The amplitudes of the two signals are made to equal and the phases of the signals are shifted by 180 degrees. Then the output of the detector 8 becomes zero. The change in the output is observed on an oscilloscope 9. In this system, when temperature change occurs on one path of the optical fiber paths 4 and 5, the transmission delay and the amount of signal attenuation are changed, the balanced state of the output of the detector 8 is collapsed, and the output signal is generated. Thus it is found that the temperature change occurs on the optical fiber path 4 or 5. |
