JPS6350811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber temperature switch using a directional coupler made of optical fiber, and its purpose is to construct a temperature switch by using mercury in the tip reflection mechanism of the optical fiber switch. A fiber optic temperature switch is provided. FIG. 1 shows a so-called directional coupler constructed by bending a pair of optical fibers 1a and 1a' with a radius R so as to face each other, and polishing and abutting a portion of the opposing surfaces. In this directional coupler 1, light incident from one end A of one optical fiber 1a is split at a junction C, and the other end A ₁ of the other optical fiber 1a' is connected to the other end B of one optical fiber 1a. (Optical fiber 1
No output is output to B ₁ of a′). On the other hand, optical fiber 1
The light incident from B of a is output to _B1 and A (no output is output to _A1 ), and in these cases, the lights do not interfere with each other. By using this type of directional coupler 1 , a switch as shown in FIG. 2 can be constructed using one optical fiber. That is, this switch includes a light emitting circuit 2, a light emitting element 3 such as a light emitting diode that emits light in response to a signal from the light emitting circuit 2, and one optical fiber 1a through which light from the light emitting element 3 is propagated.
and a tip reflection mechanism section 4 having a mirror-like perfect reflection surface 4a and a non-reflection surface 4a' that face the end surface of the optical fiber 1a and reflect the propagated light, and the optical fiber 1a, 1a', a light receiving element 5 such as a photodiode that receives the light propagated through the directional coupler 1 , and a light receiving element 5 such as a photodiode that receives the light transmitted through the directional coupler 1 . a light receiving circuit 6 that converts an optical signal into an electrical signal;
It is comprised of a switch circuit 7 which performs a switch operation based on a signal from the light receiving circuit 6. FIG. 3 shows an example of the above-mentioned light emitting circuit 2, light receiving circuit 6 and switch circuit 7, where E is a DC power supply, _R1 is a current limiting resistor, _OP1 is an operational amplifier,
R _f is a feedback resistor, VR ₁ and VR ₂ are variable resistors that each set a predetermined voltage, OP ₂ is a comparator consisting of an operational amplifier, and R ₂ and R ₄ are each a resistor. In operation, first, the variable resistor VR ₁ is adjusted to set the point on the non-inverting input terminal side of the operational amplifier OP ₁ to a predetermined potential V ₁ . In this state, when the light receiving element 5 now receives light from the light emitting element 3 via the optical fiber 1a', the leakage current changes accordingly, is multiplied by R _f by the feedback resistor R _f , and is applied to the operational amplifier OP ₁ . An output of V ₁ +ΔV appears at the output terminal. If the potential of the point on the non-inverting input terminal side of the comparator OP ₂ is set via the variable resistor VR ₂ so as to perform a comparison based on the change in voltage ΔV, when light enters the light receiving element 5, the comparator
The output of OP ₂ changes from a voltage value close to the power supply to a voltage value close to zero, thereby turning on the transistor Tr and lighting the lamp L. The present invention relates to a temperature switch using an optical fiber as described above, and the present invention will be explained below with reference to the drawings. FIG. 4 shows an embodiment of the present invention, in which one end of an optical fiber 1a is coupled to the other end of an optical fiber 1a, into which an optical signal is input via the light emitting element 3 shown in FIGS. 2 and 3. A feature is that the tip reflection mechanism section 4 is constructed from a glass cylinder filled with mercury that expands depending on the temperature. That is, optical fiber 1
The tip end a is introduced into the glass cylinder 8. Furthermore, the end face of the tip of the introduced optical fiber 1a is cut perpendicularly to the length direction of the optical fiber 1a, and is finished with a mirror finish, and the bottom of the glass cylinder 8 is filled with mercury Hg. There is. Therefore, in operation, when light from a light source such as the light emitting element 3 is transmitted through the optical fiber 1a, for example, at normal ambient temperature, mercury Hg is located at the bottom of the glass cylinder 8, Therefore, the tip of the optical fiber 1a and the mercury Hg are separated from each other without coming into contact with each other. Therefore, the transmitted light is emitted from the tip of the optical fiber 1a, reflected by the mercury Hg, and returned to the optical fiber 1a.
There is almost no light returning to the inside of a. On the other hand, as the temperature rises, mercury Hg expands.
Then, when the upper surface of the mercury Hg reaches the tip end surface of the optical fiber 1a as shown in FIG. 5, the light that has been emitted up to now is reflected by the mercury Hg and returns through the optical fiber 1a as reflected light. When this reflected light is received by the light receiving element 5 through the directional coupler 1 as shown in FIGS. 1 and 2, the light receiving circuit 6 is activated, and thereby the switch circuit 7 is activated. It is a switch that can be turned on. As described above, according to the present invention, the tip of an optical fiber is introduced into a glass cylinder in which mercury, which expands as the temperature rises, is sealed, and when the temperature rises, the inside of the optical fiber flows through the mercury. Because it is configured to reflect the transmitted light,
The switching operation may be performed automatically in response to changes in the ambient temperature of the glass cylinder. Furthermore, by using a longer optical fiber if necessary, it is possible to increase the distance from the switch circuit to the tip reflection mechanism, making remote switch operation possible. Further, since only one transmission optical fiber is required from the light source to the tip reflection mechanism, and the structure as a whole is relatively simple, miniaturization can be achieved. In addition, conventional general electric switches electrically connect the switch operation part and the switch circuit part through lead wires, but in the present invention, an insulating optical fiber is used, and the tip part is electrically connected. Since there are no parts, it is explosion-proof and can be applied to the disaster prevention field. Furthermore, since the light is reflected by the mercury sealed in the glass cylinder, there are advantages such as less wear on the tip of the optical fiber.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a directional coupler made of optical fiber, Fig. 2 is a schematic explanatory diagram of the configuration of an optical fiber switch, Fig. 3 is an explanatory diagram showing an example of a circuit used in the above switch, and Fig. 4 is an embodiment of the present invention,
FIG. 5 is an explanatory diagram of the same operation as above. 1 ... Directional coupler, 1a, 1a'... Optical fiber, 2... Light emitting circuit, 3... Light emitting element, 4... Tip reflection mechanism section, 5... Light receiving element, 6... Light receiving circuit, 7 ...Switch circuit, 8...Glass cylinder, Hg...Mercury.

Claims (1)

[Claims] 1 A directional coupler is formed by abutting part of the opposing surfaces of optical fibers, and a light emitting circuit is provided at one end of one optical fiber, and a light receiving circuit is provided at one end of the other optical fiber, and The tip of the optical fiber provided with the light emitting circuit is introduced into a glass cylinder in which mercury, which expands as the temperature rises, is sealed, and the mercury, which expands as the temperature rises, flows into the tip of the optical fiber. An optical fiber temperature switch comprising a switch circuit that is controlled via the light receiving circuit by the reflected light transmitted through the optical fiber by contact with the optical fiber.