APPARATUS AND METHOD FOR MEASURING STRAIN OF OPTICAL FIBER DUE TO BENDING OF OPTICAL CABLE

摘要

PURPOSE:To measure the distribution of the strain of an optical fiber due to the bending of the optical fiber, by measuring the max. value and min. value in the extension and contraction amount of the optical fiber by gradually bending the same in definite radius of curvature and taking the difference of both values. CONSTITUTION:Light modulated at frequency F=950MHz is incident to a coated optical fiber 1 from an electrooptical converter 8 by a high frequency signal generator and received by a photoelectric converter 9. The signals from the photoelectric converter 9 and the signal generator 10 are guided to a vector voltmeter 11. The voltmeter 11 detects the phase change of the signal from the photoelectric converter 9 in reference to the phase of the signal from the signal generator 10 to drawn the same on a recorder 12. An optical cable 3 is bent by using an optical cable bending apparatus 7 so as to gradually increase the bending angle thereof from 0 deg. and the phase amount at this time is read from the recorder 12. The max. value and min. value of this phase amount are calculated to calculate the difference of both values. Predetermined operation is performed on the basis of this difference to calculate a strain amount.