JPS645359B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new fire detection system for detecting fire, which includes fire detection means and detection signal means constructed using optical fibers.

Conventional fire detection methods include those that use heat detectors that detect heat and those that use flame detectors that detect radiation unique to flames, but the detection part,
Since both the detection signal transmission part undergoes electrical processing, if there is a source of electrical noise in these detection systems, such as power supply wiring, nearby, the electrical noise will be picked up and the noise signal will be generated. The problem is that the signal becomes a detection signal.

The present invention has been made in order to eliminate the drawbacks of the conventional devices as described above.The fire detector and the detection signal transmission line are constructed of optical fibers, and the fire detection section is provided with coherent light emitted from, for example, a laser light source device. to form interference fringes, and the difference between the above-mentioned interference fringe state in a normal state without a fire and the above-mentioned interference fringe state when mechanical stress is applied to the fire detection part due to a temperature change when a fire occurs. The purpose of the present invention is to provide a fire detection method using optical fibers that can accurately detect the location of a fire.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram showing a fire detection system according to an embodiment of the present invention. In the figure, 1 is, for example, a laser light source device, which emits coherent light Sl.
2a, 2b, 2c, and 2d are respective parts of optical fibers forming a closed circuit, and 3 is a fire detector.
A splitter 4 that branches the optical fiber 2a into two paths 2b and 2c, a coupler 5 that overlaps the two paths 2b and 2c to form interference fringes Rl, and one of the branched optical fibers 2b and 2c. For example, a shape memory alloy 6 disposed on an optical fiber 2c. 7 is a light receiver; 8 is an interference fringe displacement detector that includes the light receiver 7 and outputs an output signal v;
It is configured to detect movement and changes in the interference fringes RI that have passed through and been emitted.

Figures 2 and 3 are the fire detector 3 shown in Figure 1.
FIG. FIG. 2 shows a case where there is no fire, and there is no change in the shape of the shape memory alloy 6, so the optical fiber 2c placed thereon is
Since no mechanical stress is applied to , the interference fringe pattern superimposed by the coupler 5 does not change, and this state is considered to be a normal state. on the other hand,
What is shown in FIG. 3 is the case where a fire occurs. When heat is applied to the shape memory alloy 6, which memorizes its shape, it deforms as shown in FIG. The interference fringe pattern is obtained by superimposing the light passing through the optical fiber 2c and the light passing through the other paired optical fiber 2b by the coupler 5. The above interference fringe pattern when there is no fire is moved and changed, thereby making it possible to detect that the temperature around the fire detector 3 has increased.

Based on the above configuration, the operation of one embodiment of the present invention will be described.

First, the coherent light Sl emitted from the light source device 1 passes through the optical fiber 2a, and at the splitter 4 of the fire detector 3, the light passing through the optical path of the optical fiber 2b and the optical fiber in which the shape memory alloy 6 is arranged are connected. The light passing through the optical path 2c is once branched, and further superimposed by the coupler 5 to form an interference fringe pattern Rl.
The light is input to the optical fiber 2d. Then, the interference fringe pattern is emitted after passing through the optical fiber 2d.
Rl is transmitted to the interference fringe displacement detector 8 via the light receiver 7, where the movement and change of the interference fringe pattern Rl is detected, but when there is no fire, the shape memory alloy provided in the fire detector 3 Since the shape of the optical fiber 2c does not change, there is no displacement of the optical fiber 2c, and therefore no movement or change in the interference fringe pattern Rl is detected, and a normal detection signal vo is output. On the other hand, when a fire occurs, heat is applied to the shape memory alloy 6 as shown in FIG. The interference fringe pattern Rl of the lights superimposed by the above-mentioned interference fringe pattern Rl when there is no fire moves and changes, and the interference fringe displacement detector 8 detects this minute displacement, Outputs a detection signal v′ when a fire occurs,
A fire can be detected by determining the difference between this and the detection signal vo during normal operation.

As explained above, according to the fire detection method of the present invention, the fire detection section and the detection signal transmission path are constructed of optical fibers, and the fire detection section is formed with an interference fringe pattern of coherent light, so that no fire can be detected. Accurately detects the location of a fire by detecting the difference between the above interference fringe state during normal operation and the above interference fringe state when mechanical stress is applied to the fire detection section due to temperature rise when a fire occurs. As a result, it is possible to eliminate the electrical noise in the detector section and the signal transmission path, which was a drawback in the conventional method, and the reliability of fire detection is dramatically improved, which is a great practical effect.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram according to an embodiment of the present invention;
Figures 2 and 3 show the -
FIG. DESCRIPTION OF SYMBOLS 1... Light source device, 2... Optical fiber, 3... Fire detector, 4... Branch, 5... Coupler, 6...
Shape memory alloy, 7... Light receiver, 8... Interference fringe displacement detector.

Claims (1)

[Claims] 1. A light source device that emits coherent light including a laser beam to an optical fiber, a branching device disposed on the optical fiber that branches the coherent light into two paths, and one of the two branched paths, due to a temperature change. A fire detector comprising: a detection means arranged so that stress is applied to the optical fiber as a result of the deformation of a substance whose shape is deformed; and a coupler that rejoins the two branched paths; Equipped with an interference fringe displacement detector that detects the movement or change of the interference fringe shape pattern formed by the emitted light and outputs an abnormal signal, and by detecting the movement or change of the interference fringe pattern when a fire occurs. A fire detection method using optical fiber, which is characterized by detecting fire.