| 摘要 |
PURPOSE:To obtain a distribution type fiber sensor which has good sensitivity and high position resolution by entering linear polarized light beams which are perpendicular to X and Y axes as two characteristic axes of polarization of a polarization plane maintaining optical fiber which has its terminal coated with a reflecting film. CONSTITUTION:A delay optical path 17 which is variable in delay distance is provided to one incidence optical path and a frequency shifter 18 which makes a frequency shift by a constant quantity is provided to the other incidence optical path. Further, a light source 1 is provided with plural filters 2 which differ in transmission frequency width replaceably. Light from the light source 1 is split into two pieces of luminous flux, which are propagated as two mode beams in the polarization plane maintaining optical fiber 12 after passing through the optical path 17 and a shifter 18. Here, if an external force, e.g. pressure P is applied to the fiber 12 lengthwise to perform conversion from the X axis to the Y axis, the two pieces of luminous flux which differ in frequency are put together in the fiber 12 to cause interference. For the purpose, modulation is imposed on the optical path 17 and then a signal detection system 19 detects the interference signal between the light converted from the X axis to the Y axis and light propagated along the Y axis.
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