JP2011128128A - Optical fiber sensor head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that manufacturing is hard in an optical fiber sensor head, making optical interference signal output sensor signal, which needs to convert external pressure used as signal into a change of optical phase in such a way that the optical phase is made to be changed as one method by a strain of the plate surface by spirally sticking optical fiber strand on diaphragm surface. <P>SOLUTION: The optical fiber sensor head wherein the cylinder is strained to turn its flatness varied by applying the external pressure used as signal to the cylinder with elasticity, so that the optical phase passing through it is varied by making the optical fiber undergo expansion/contraction in such a manner that a tension of the optical fiber wound on it varies. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical fiber sensor head that utilizes characteristics that change the phase of an optical signal passing through an optical fiber due to an external pressure.

  The advantage of the optical fiber sensor is that it can be used in a harsh environment because the sensor head portion can be powered off and the sensor signal can be transmitted stably over a long distance.

  As a high-performance optical sensor system, there is an optical interference system that detects a change in optical phase.

  An example of a sensor that employs an optical interference method is an acceleration sensor that detects seismic waves and the like.

  As a conventional acceleration sensor, there is a method that detects the phase change of light from the change in the distance of the diaphragm due to mechanical vibration, but there is a problem with long-term stability due to the loss of light and the light coming into space. It was.

  As another conventional sensor, there is a method in which an optical fiber is expanded and contracted by applying an external pressure to the optical fiber, and the phase of light passing therethrough is changed. This is a method with excellent stability, and there is a method in which the optical fiber is stretched by pasting the optical fiber in a spiral shape on the vibration plate surface and distorting the plate surface with external pressure. There were difficulties in manufacturing technology, such as pasting in a shape.

In the present invention, by applying external pressure to the optical fiber, the optical fiber is expanded and contracted,
A method of changing the optical phase passing therethrough is adopted.

  In the present invention, as a method for expanding and contracting the optical fiber, by changing the external pressure to the tension applied to the optical fiber, it is possible to eliminate difficult operations such as attaching the strands of the optical fiber in a spiral shape.

  In the optical fiber sensor head of the present invention, elastic metal or resin cylinders are attached to both ends of a weight that is moved by acceleration such as seismic waves, and the cylinders attached to both ends of the weight are pressed from the attached outer frame and pressure is applied. By receiving, the flat shape is made normal.

  The optical fiber is wound around a position where the cross-section side of the flattened cylindrical portion of the flattened cylinder is one round, and tension is applied in the normal state.

  When the weight moves due to acceleration such as seismic waves, the flatness of the cylinders at both ends thereof changes differentially, and the tension of the wound optical fiber also changes differentially.

  The wound optical fiber expands and contracts due to a change in tension of the optical fiber.

  The optical phase (light delay time) passing through the optical fiber changes due to the expansion and contraction of the optical fiber.

  In the present invention, by wrapping and fixing the optical fiber in the direction of the cross section of the cylinder, the flatness of the cylinder changes, the distance of the flat cross section changes, and the tensile strength applied to the optical fiber changes. It is not necessary to cause the optical fiber to expand and contract and to stick the optical fiber in a spiral shape.

  In the present invention, by increasing the number of turns of the optical fiber, sensitivity can be increased and sensitivity variation can be improved.

  In the present invention, the cylinder having elasticity may be a cylinder obtained by processing a leaf spring into a cylindrical shape, and may be a cylindrical shape that can maintain elasticity even if it is made of metal or resin.

  The cylinders attached to both ends of the weight of the present invention can be prevented from moving from the side and the directivity in the acceleration direction can be increased by attaching the cylinders to the weight with a 90 ° angle shift.

  Since the expansion and contraction of the optical fiber wound around both cylinders in the present invention operates differentially, the sensitivity can be enhanced by using both optical signals.

Fig. 1 is a structural diagram of an optical fiber sensor head according to the present invention. Front is a structural diagram viewed from the front. Side is a structural diagram viewed from the side. Bottom is a structural diagram viewed from the bottom. Is an operation explanatory diagram of the optical fiber sensor head of the present invention. The resting state (acceleration 0) is the operating state when no acceleration is applied. When the acceleration is applied, the operating state when the weight is moved by the acceleration.

FIG. 1 is a structural diagram of an optical fiber sensor head of the present invention.
FIG. 2 is an operation explanatory diagram of the optical fiber sensor head of the present invention.

  In the optical fiber sensor head of the present invention, the cylinders 1 and 2 having elasticity are fixed to the upper and lower sides of the weight, and when the cylinders 1 and 2 are pressed from the outer frame, pressure is applied to the cylinders 1 and 2 and the flat state is set for elasticity Is done.

  The cylinders 1 and 2 fixed to the top and bottom of the weight are fixed at a 90 ° angle as shown on the front and side surfaces.

  The optical fibers 1 and 2 are wound around the flat portions of the cylinders 1 and 2 in a tensioned state and fixed to the cylinders.

  When the weight fluctuates up and down, the flatness of the cylinders 1 and 2 changes, the tension applied to the optical fibers 1 and 2 changes, the optical fibers 1 and 2 expand and contract, and the optical phase of light passing through (optical delay time) To change.

  The operation of the optical fiber sensor head of the present invention will be described with reference to FIG.

  In FIG. 2, for the sake of explanation, it is assumed that the upper and lower cylinders 1 and 2 appear on the same surface.

  In the stationary state (acceleration 0), the weight is stationary at the center, and the flatness of the upper and lower cylinders 1 and 2 does not change.

  When acceleration is applied, when the weight moves relatively upward, the pressure applied to the cylinder 2 decreases, the flatness of the cylinder 2 decreases, and the distance decreases. Therefore, the tension of the optical fiber wound there is The optical fiber length is reduced, the optical fiber length is shortened, the delay time of light passing through it is changed in a decreasing direction, the pressure applied to the cylinder 1 is increased, the flatness of the cylinder 1 is increased, and the distance is increased. The tension of the optical fiber wound around the fiber increases, the optical fiber length increases, and the delay time of the light passing therethrough increases.

  The present invention is suitable for a sensor head of an optical fiber sensor system installed in a remote place such as a seafloor seismic observation, a place where power cannot be supplied, a place susceptible to electromagnetic noise, and a place where the temperature environment is severe.

Claims (6)

  An optical fiber sensor head characterized in that two cylinders having elasticity are fixed to both ends of a weight with their attachment directions shifted by 90 degrees from each other.   It has means for fixing the cylinders attached to both ends of the weight constituted by “Claim 1” in one frame, and the cylinder is distorted and fixed in a flat state by the force applied from the frame. Features and optical fiber sensor head.   The weight composed of “claim 2” is moved in the cylinder direction at both ends by the acceleration applied from the outside, and the flatness is changed differentially by changing the force applied to the cylinders at both ends. An optical fiber sensor head.   [Claim 3] The optical fiber is fixed to both ends of each cylinder whose flatness changes differentially, and the tension of the optical fiber fixed thereto is changed according to the change of the flatness. Optical fiber sensor head.   The optical fiber sensor head according to claim 4, wherein the optical fiber fixed to the optical fiber is expanded or contracted by a change in tension applied to the optical fiber.   The optical fiber sensor head according to claim 5, wherein the optical phase passing through the optical fiber is changed by the expansion and contraction of the optical fiber.

Images