To provide a method for optimizing a residual strain value of an optical fiber unit wire which is designed to eliminate effects onto forming a cable or installing a cable on the basis of a residual strain optimum value, by recognizing the residual strain optimum value of the optical fiber unit wire beforehand.
A plurality of optical fiber units are prepared. A residual strain of each of the prepared optical fiber units is measured by a residual strain- measuring apparatus 1. At the same time, each of a high-temperature test, a hydraulic test and a bending test is also carried out to each of the optical fiber units whose residual strain is measured. The optical fiber unit having the measured value of each test within a permissible value is extracted from the result of the three tests. When the residual strain measured value measured by the residual strain-measuring apparatus 1 of the extracted optical fiber unit is within a preset permissible value, the residual strain measured value is made the optimum value.
HAYANO TETSUO
MITSUHASHI KEIKO
SHIMOMICHI TAKESHI
OHASHI KEIJI
