| 摘要 |
PURPOSE:To increase the length of an optical fiber which can be measured by superposing pulse laser light beams from semiconductor lasers one over the other, increasing the quantity of light incident on the fiber to be measured, and improving the detection levels for backward scattered light and Raman scattered light. CONSTITUTION:The two semiconductor lasers 1 and 4 are so installed that the polarizing directions of the projected pulse laser light beams cross each other at right angle. The light beams which are collimated by lenses 2 and 3 are multiplexed by a polarization beam splitter 10 which is an optical multiplexer, passed through an acousto-optic element 7 in an input signal in turned off state, and coupled with the fiber 6 to be measured. The light entered into the fiber 6 generates the backward scattered light and Raman scattered light, parts of which return in the opposite direction from the incidence direction. Then the return light from the fiber 6 is collimated by a lens 5, diffracted by the element in an input signal is turned on state, and guided to a lens 8 and a fiber 9 for detection. The detected light is processed electrically to obtain a measured value. |
