Title:
LOW COHERENCE REFLECTOMETER
Document Type and Number:
Japanese Patent JP3298373
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To allow components caused by residual reflection to be removed and obtain a highly sensitive reflectometer by providing a modulation optic system in an optical delay circuit and also providing a wave detection system corresponding to the modulation in a signal processing system.
SOLUTION: A phase modulator 21 whose refractive index periodically varies according to frequency (f) from a transmitter 22 is provided between a lens 13 and a reflecting mirror 15 of an optically variable delay circuit 7. Although a light beam 15 is subjected to phase modulation at a predetermined frequency f1 while it goes to and back from the modulator 21, residual reflection light may not be phase- modulated as it does not pass through the modulator 21. Therefore an interference signal between reference light reflected on the reflecting mirror 15 and back Rayleigh scattered light of a light waveguide 6 which has been phase-modulated at frequency (f) of a transmitter 12 includes a component which varies at frequency of f+f1, but an interference component of residual reflection light and reflection light varies only at frequency (f). Accordingly, by setting wave detection frequency f+f1 in a signal processing system 11 and adjusting a wave detection band width so that the frequency (f) component may not be mixed, the output caused by residual reflection can be removed.
Inventors:
Kazumasa Takada
Hiroo Yamada
Hiroo Yamada
Application Number:
JP21563695A
Publication Date:
July 02, 2002
Filing Date:
August 24, 1995
Export Citation:
Assignee:
Nippon Telegraph and Telephone Corporation
International Classes:
G01M11/02; G01M11/00; (IPC1-7): G01M11/00; G01M11/02
Domestic Patent References:
| JP2234042A | ||||
| JP63196829A | ||||
| JP2251730A | ||||
| JP2140639A |
Attorney, Agent or Firm:
Toshiro Mitsuishi (2 outside)