Patent ID: 7992440

Claim:
An optical fiber vibration sensor, comprising: a light source, an optical receiver, an optical dividing/coupling unit, a signal processing unit for processing a signal received from the optical receiver, a fiber loop portion for propagating lights divided by the optical dividing/coupling unit as a counter clockwise light and a clockwise light, and a housing for accommodating the light source, the optical receiver, the optical dividing/coupling unit, the signal processing unit, and a part of the fiber loop portion, wherein one end of the optical dividing/coupling unit is connected to the light source and the optical receiver, and another end of the optical dividing/coupling unit is connected to the fiber loop portion, wherein the optical dividing/coupling unit comprises a first optical coupler to which the light source and the optical receiver are connected, a polarizer for polarizing a light output from the first optical coupler, a second optical coupler for dividing the light output from the polarizer to be inputted into the fiber loop portion and coupling the light output from the fiber loop portion, wherein the fiber loop portion comprises a phase modulator, wherein a part of an optical fiber composing the fiber loop portion is provided in the housing as an optical fiber for delay, while another part of the optical fiber composing the fiber loop portion is installed outside the housing as a vibration detecting optical fiber, wherein the vibration detecting optical fiber comprises two parallel portions of the fiber loop portion, which are accommodated in a single flexible tube, wherein the fiber loop portion is folded to provide the two parallel portions of the fiber loop portion to provide a uniform sensitivity to detect vibration along a longitudinal direction, and wherein a middle point of the optical fiber that forms the optical fiber loop portion is located outside the flexible tube.