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Patent Searching and Data


Title:
MEASURING METHOD OF DIFFERENCE IN OPTICAL PATH LENGTH
Document Type and Number:
Japanese Patent JPS6141932
Kind Code:
A
Abstract:

PURPOSE: To measure a difference in optical path length with high precision by measuring a low and a high frequency twice successively.

CONSTITUTION: A modulation frequency f1 is so selected that laser light beams with wavelengths λ1 and λ2 from LE light sources 3 and 5 have a phase difference θ1 of ≤180° after propagating in a single-mode fiber 7 having length L. Then, the 1st measurement is taken at the sufficiently low frequency f1 and the phase difference θ1 is obtained from a rough standard; and the frequency is raised to f2 to read a position meter within a range of ±180°, and the read value is corrected by an integral multiple of 360° estimated from the phase difference θ2=θ1×f2/f1 expected at the frequency f2 to calculate a phase difference θ2. Thus, the phase difference is measured precisely even on a condition where the phase difference exceeds ±180°.


Inventors:
TANAKA SHIGERU
NOGUCHI KAZUHIRO
Application Number:
JP1984000163998
Publication Date:
February 28, 1986
Filing Date:
August 04, 1984
Export Citation:
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Assignee:
SUMITOMO ELECTRIC INDUSTRIES
NIPPON TELEGRAPH & TELEPHONE
International Classes:
G01J7/00; G01N21/41; (IPC1-7): G01J9/00