PURPOSE: To make accurate measuring even in case an external vibration is applied to optical fiber by furnishing an optical fiber between a laser beam source and an interfering mechanism part, and casting a laser beam having an adjusted polarization plane into the optical fiber.
CONSTITUTION: An optical fiber 4 and the second and the third lens system L2, L3 are installed between a laser source 11 in a body mechanism part 1 and a polarized beam splitter(PBS) 21a in an interfering mechanism part 2, wherein the lens systems L2, L3 are located on the PBS side and laser beam source side, respectively. Accordingly the frequency change in the incident laser beam due to vibration of the optical fiber 4 acts evenly on the reference light and measuring light, which are thus set off and do not affect the measurement, at all. An adjusting means 15 furnished between beam source 11 and lens system L3 adjusts the polarization plane of laser beam having linear polarization so that it mates with the polarization plane of the optical fiber 4 which makes transmission while holding the polarized state of incident beam. Accordingly the transmission takes place with the polarized state of the incident laser beam held as it is even though the optical fiber 4 vibrates. Thus accurate measuring is achieved.
ICHIKAWA SADAYOSHI
TAKAHASHI TOMOTAKA
| JP1167607B |