Receiver and fire alarm system

Abstract

To provide a receiver and a fire alarm system which can increase a measurement period, reliably identify a point of measurement, and is not affected by noise in fire determination.SOLUTION: A fire alarm system that detects a fire and performs an alarm comprises a sensor including: an optical fiber cable installed on a fire detection target; and a detection unit that transmits predetermined pulse light to the optical fiber cable, detects a temperature at each position on the fire detection target from Brillouin scattered light, which is reflected light from the optical fiber cable, and performs a fire determination on the basis of the temperature at each position detected. A receiver connected to the sensor delivers information such as fire alarm on the basis of the fire determination from the sensor.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a receiver and a fire alarm system.

Background Art

[0002] Conventionally, there has been known a fire alarm system that uses an optical fiber cable as a temperature sensor to determine and notify a fire.

[0003] In a conventional optical fiber fire alarm system, a repeater detects the reflected light of pulsed light incident on an optical fiber cable laid in a building such as a building to be detected for fire, and the repeater measures the reflected light to detect the temperature and determine a fire, and a receiver that receives the fire determination gives a fire alarm.

[0004] Furthermore, in a conventional optical fiber fire alarm system, as the reflected light from the optical fiber cable, the intensity of Raman scattered light, particularly anti-Stokes light, which depends on the temperature of the optical fiber, is measured to obtain temperature information at each measurement point.

[0005] Since the anti-Stokes light of Raman scattered light has the property that its intensity changes with the temperature change at the place where it is generated, temperature information can be obtained by utilizing this property.

[0006] Such a conventional optical fiber fire alarm system has the following problems.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In a conventional optical fiber fire alarm system that measures Raman scattered light to obtain temperature information, since the Raman scattered light is very weak, data averaging processing is required to obtain reliable measurement accuracy, resulting in a slow measurement cycle.

[0009] In a conventional optical fiber fire alarm system, a repeater detects the reflected light of the pulsed light incident on the optical fiber cable laid in a building, the repeater measures the reflected light to detect the temperature and make a fire judgment, and the receiver that receives the fire judgment input issues a fire alarm. Therefore, the receiver cannot obtain the temperature information of each measurement point of the optical fiber cable and cannot identify the measurement point.

[0010] In a conventional optical fiber fire alarm system, since the receiver receives the fire judgment signal from the repeater via a power line, noise may be added to the fire judgment signal, and the fire judgment may be affected by the noise.

[0011] Also, a conventional optical fiber fire alarm system has problems such as the core diameter of the multimode GI fiber (graded index fiber) used for the optical fiber being as large as 50 μm, so the monitoring distance cannot be made as long as about 1 Km.

[0012] Furthermore, when trying to increase the monitoring distance, a high-power light source needs to be used, resulting in problems such as the need for an expensive and large housing.

[0013] The present invention has been made in view of the above problems. Since the receiver detects Brillouin scattered light from the optical fiber cable to make a fire judgment, the measurement cycle can be shortened, the measurement point can be surely identified, the fire judgment is not affected by noise, and a receiver and a fire alarm system that can achieve a long monitoring distance are provided.

Means for Solving the Problems

[0014] The first invention is a receiver that acquires temperature information from the frequency change of Brillouin scattered light from an optical fiber cable laid on a fire detection target, and determines a fire from the acquired temperature information. When the temperature information shows a temperature change of a predetermined amount or more within a first unit time, and the temperature change of the predetermined amount or more continues for a second unit time or more that is shorter than the first unit time, it is determined that a fire has occurred, or when the temperature information shows a temperature of a predetermined value or more, and the temperature of the predetermined value or more continues for a third unit time or more, it is determined that a fire has occurred. Then, a predetermined pulsed light is sent to the optical fiber cable, the temperature at each location of the fire detection target is detected from the Brillouin scattered light which is the reflected light from the optical fiber cable, information such as a fire alarm is transmitted based on the detected temperature at each location, an optical fiber detector for measuring the temperature of each measurement region in the optical fiber cable is provided, a fire determination is made based on the temperature information received from the optical fiber detector, and when a fire is determined, a reception processing unit for performing a fire alarm display is provided. The optical fiber detector monitors the temperature measurement accuracy, and constantly measures and calculates whether the deviation between the measured temperature by the optical fiber and the temperature sensor built in the optical fiber detector is within a predetermined threshold range to detect an abnormality. When the abnormality is detected, temperature measurement accuracy degradation information is transmitted to the reception processing unit, and the reception processing unit is configured to perform a failure display of the optical fiber detector based on the temperature measurement accuracy degradation information It is a receiver.

[0015] The second invention is in the receiver according to the first invention, The optical fiber detector includes an acousto-optic modulator, a time delay device, and an interferometer. The Brillouin scattered light from the optical fiber cable is branched into two, and each of the branched Brillouin scattered lights is input to the acousto-optic modulator and the time delay device. The first branched light frequency-shifted by the acousto-optic modulator and the second branched light delayed by a predetermined delay time by the time delay device are input to the interferometer to obtain a corresponding beat signal, and the temperature information is obtained based on the frequency change of the Brillouin scattered light based on the phase change of the obtained beat signal It is a receiver.

[0016] The third invention is in the receiver according to any one of the first invention and the second invention, The reception processing unit includes a display unit for displaying a fire display, an operation status, a status monitoring diagram, a trend graph, a history list, various abnormalities, etc., and an operation unit for performing operations such as recovery, main sound stop, test, inspection, etc It is a receiver.

[0017] The fourth invention is In any one of the first invention to the third invention in the receiver described above, The optical fiber cable is a single-mode fiber, and a wavelength band of 1.55 μm is used as the light source of the predetermined pulsed light sent to the optical fiber cable It is a receiver.

[0018] The fifth invention is A fire alarm system for detecting and alarming a fire, comprising an optical fiber cable laid on a fire detection target, sending a predetermined pulsed light to the optical fiber cable, and obtaining temperature information of each location of the fire detection target from a frequency change of Brillouin scattered light which is reflected light from the optical fiber cable, and a receiver that transmits information such as a fire alarm based on the obtained temperature information of each location. The receiver determines that a fire has occurred when the temperature information shows a temperature change of a predetermined level or more within a first unit time and the temperature change of the predetermined level or more continues for a second unit time or more which is shorter than the first unit time. Or the receiver determines that a fire has occurred when the temperature information shows a temperature of a threshold value or more and the temperature of the threshold value or more continues for a third unit time or more. The receiver has an optical fiber detector that measures the temperature of each measurement area in the optical fiber cable. The receiver has a reception processing unit that makes a fire determination based on the temperature information received from the optical fiber detector and performs a fire alarm display when a fire is determined. The optical fiber detector monitors the temperature measurement accuracy, and constantly measures and calculates whether a deviation between the measurement temperature by the optical fiber and the temperature sensor built in the optical fiber detector is within a predetermined threshold range to detect an abnormality. When the abnormality is detected, temperature measurement accuracy reduction information is transmitted to the reception processing unit, and the reception processing unit is configured to perform a failure display of the optical fiber detector based on the temperature measurement accuracy reduction information. A fire alarm system as follows.

[0019] The sixth invention is In the fire alarm system according to the fifth invention, the reception processing unit includes an acousto-optic modulator, a time delay device, and an interferometer. The Brillouin scattered light from the optical fiber cable is branched into two, and each of the branched Brillouin scattered lights is input to the acousto-optic modulator and the time delay device. The first branched light frequency-shifted by the acousto-optic modulator and the second branched light delayed by a predetermined delay time by the time delay device are input to the interferometer to obtain a corresponding beat signal, and the temperature information is obtained based on the frequency change of the Brillouin scattered light based on the phase change of the obtained beat signal. A fire alarm system configured as such as follows.

[0020] The seventh invention is a fire alarm system that detects and alarms a fire, comprising an optical fiber cable laid on a fire detection target, a unit that sends predetermined pulsed light to the optical fiber cable, and detects the temperature at each location of the fire detection target from the frequency change of Brillouin scattered light, which is reflected light from the optical fiber cable, and a detector that determines whether a fire has occurred based on the detected temperature at each location. The detector determines that a fire has occurred when the temperature information shows a temperature change of a predetermined amount or more within a first unit time and the temperature change of the predetermined amount or more continues for a second unit time or more, which is shorter than the first unit time. Alternatively, the detector determines that a fire has occurred when the temperature information shows a temperature of a predetermined value or more and the temperature of the predetermined value or more continues for a third unit time or more. A light fiber cable is laid on the fire detection target, and a detection unit that sends a predetermined pulsed light to the light fiber cable and detects the temperature of each location of the fire detection target from Brillouin scattered light, which is reflected light from the light fiber cable, and performs a fire determination based on the detected temperature of each location. A receiver that transmits information such as a fire alarm based on the fire determination from the sensor. The detection unit monitors the temperature measurement accuracy, and constantly measures and calculates whether the deviation between the measured temperature by the optical fiber and the temperature sensor built in the detection unit is within a predetermined threshold range to detect an abnormality. When the abnormality is detected, temperature measurement accuracy degradation information is transmitted to the receiver, and the receiver is configured to display a failure of the detection unit based on the temperature measurement accuracy degradation information. A fire alarm system.

[0021] The eighth invention is According to any one of the fifth to seventh inventions In a fire alarm system, The optical fiber cable is a single-mode fiber, and a wavelength band of 1.55 μm is used as a light source for a predetermined pulsed light sent to the optical fiber cable. A fire alarm system.

Effect of the Invention

[0026] According to the present invention, a receiver detects Brillouin scattered light from an optical fiber cable to make a fire judgment. Raman scattering, especially anti-Stokes light, has a change in the intensity of light due to a temperature change, while Brillouin scattered light has a change in the frequency of light due to a temperature change. Therefore, the measurement period can be shortened, the measurement points can be surely specified, the fire judgment is not affected by noise, and a receiver and a fire alarm system that can achieve a long monitoring distance can be provided.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0028] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0029] FIG. 1 is an overall configuration diagram of the first embodiment of the fire alarm system according to the present invention.

[0030] As shown in FIG. 1, the fire alarm system 1 performs a fire alarm using the optical fiber cable 3, and includes the optical fiber cable 3 laid in a building such as a building to be detected for fire, and a receiver 5 to which one end of the optical fiber cable 3 is connected. The receiver 5 sends predetermined pulsed light to the optical fiber cable 3, detects the temperature at each location from the reflected light from the optical fiber cable 3, and transmits information such as a fire alarm based on the detected temperature at each location.

[0031] One end of the optical fiber cable 3 is connected to the receiver 5, and a termination box 9 is connected to the other end of the optical fiber cable 3. As will be described later, measurement regions of Brillouin scattered light are set at predetermined intervals in the optical fiber cable 3.

[0032] The optical fiber cable 3 uses a single-mode fiber. Since the optical fiber cable 3 is a single-mode fiber, the monitoring distance can be set to 5 Km. The optical fiber cable 3 is made of a silica-based optical fiber.

[0033] As will be described later, based on the operation of the operation unit 5n, the receiver 5 detects Brillouin scattered light from the optical fiber cable 3 to obtain temperature information, and displays an alarm or the like on the display unit 5m.

[0034] Figure 2 is an internal configuration diagram of the receiver 5 shown in Figure 1.

[0035] First, the connection relationship of the internal configuration of the receiver 5 will be described.

[0036] As shown in Figure 2, the receiver 5 includes a reception processing unit 5a composed of a panel PC, an optical fiber detector 5b composed of an optical fiber sensor connected to the reception processing unit 5a, a signal input / output device 5c composed of an I / O module connected to the reception processing unit 5a, an AC input unit 5d that receives an AC input, a voltage conversion circuit 5e connected to the AC input unit 5d, an indicator lamp output circuit 5f connected to the voltage conversion circuit 5e, a normal / standby power supply switching circuit 5g that is connected to the voltage conversion circuit 5e and is also connected to the reception processing unit 5a, the optical fiber detector 5b, and the signal input / output device 5c, a standby battery 5h connected to the normal / standby power supply switching circuit 5g, a main acoustic output circuit 5i connected to the signal input / output device 5c, a buzzer 5j connected to the main acoustic output circuit 5i, a transfer report output circuit 5k connected to the optical fiber detector 5b and the signal input / output device 5c, a local acoustic output circuit 5l connected to the optical fiber detector 5b and the signal input / output device 5c, a display unit 5m composed of a liquid crystal monitor or the like connected to the reception processing unit 5a, and an operation unit 5n for performing various operations connected to the reception processing unit 5a.

[0037] The indicating lamp output circuit 5f is connected to the indicating lamp 9, the optical fiber detector 5b is connected to the optical fiber cable 3, the signal input / output unit 5c is connected to the transmitter 11, the transfer report output circuit 5k is connected to the related equipment 13, and the local sound output circuit 5l is connected to the local sound device 15.

[0038] Next, the functions of each part of the receiver 5 will be described.

[0039] The reception processing unit 5a controls each part within the receiver 5 and external devices connected to the receiver 5 in order to monitor the state of the fire alarm system 1.

[0040] The reception processing unit 5a performs a fire determination as described later based on the temperature information received from the optical fiber detector 5b by controlling the receiver 5 and external devices connected to the receiver 5. When a fire is determined, a fire alarm display is performed.

[0041] The reception processing unit 5a outputs main sound, local sound, and transfer report output control signals to the signal input / output unit 5c, records event (fire, failure) information, and displays the event information by operation. Further, the reception processing unit 5a records temperature information for a certain period and displays temperature trend information, etc. of a specified point by operation.

[0042] For this purpose, the reception processing unit 5a has a display unit 5m for displaying fire displays, operation status, status monitoring diagrams, trend graphs, history lists, various abnormalities, etc., and an operation unit 5n for performing operations such as recovery, main sound stop, tests (fire, backup battery), inspections (transfer report stop, local sound stop), etc.

[0043] The optical fiber detector 5b measures the temperature of each measurement region in the optical fiber cable 3 described later, and has a function of transmitting the temperature information of each measurement region in the optical fiber cable 3 to the reception processing unit 5a. The optical fiber detector 5b further has a function of detecting a disconnection in the optical fiber cable 3 and transmitting the disconnection information in the optical fiber cable 3 to the reception processing unit 5a. The reception processing unit 5a gives a fault indication (alarm) of the optical fiber cable disconnection based on the disconnection information.

[0044] The disconnection in the optical fiber cable 3 is determined, for example, by the fact that Brillouin scattered light is no longer detected after a certain position in the optical fiber cable 3, and the position is specified as the disconnection position. The disconnection position is calculated from the arrival delay time of the Brillouin scattered light with respect to the incident light.

[0045] The optical fiber detector 5b monitors the temperature measurement accuracy, and constantly measures and calculates whether the deviation (standard deviation: 1σ) of the measured temperature by the optical fiber and the temperature sensor built in the optical fiber detector 5b is within a predetermined threshold range to detect an abnormality. When an abnormality is detected, it has a function of transmitting temperature measurement accuracy degradation information to the reception processing unit 5a. The reception processing unit 5a gives a fault indication (alarm) of the optical fiber detector 5b based on the temperature measurement accuracy degradation information.

[0046] The detailed configuration and operation of the optical fiber detector 5b will be described later.

[0047] The signal input / output unit 5c outputs an operation signal from the transmitter 11, which is an external device, to the reception processing unit 5a, outputs a ringing signal to the main acoustic output circuit 5i according to a control signal from the reception processing unit 5a, outputs a ringing control signal for the local acoustic device 15 according to a control signal from the reception processing unit 5a, and controls the ON / OFF output of the transfer signal according to a control signal from the reception processing unit 5a.

[0048] The voltage conversion circuit 5e converts the AC input from the AC input section 5d into a power supply for the in-receiver circuit (DC24V), converts the AC input from the AC input section 5d into a power supply for the backup power charging circuit (DC48V), and converts the AC input from the AC input section 5d into a power supply for the indicator lamp (AC24V).

[0049] The normal / backup power supply switching circuit 5g automatically switches the power supply for the receiver circuit from the normal power supply to the backup power supply when the AC power supply is interrupted, and automatically switches from the backup power supply to the normal power supply after the AC power supply is restored. Also, the normal / backup power supply switching circuit 5g charges the backup battery 5h at a constant current according to the backup power supply capacity.

[0050] The normal / backup power supply switching circuit 5g has a function of detecting abnormal voltages in the receiver circuit and the backup battery, and transmitting an abnormal voltage signal to the reception processing unit 5a when the voltage value is less than 20.4V. In the reception processing unit 5a, a failure display (alarm) is performed as a circuit abnormality due to the abnormal voltage signal.

[0051] In addition, when an emergency power supply using an inverter power supply method is always provided outside the receiver, since the AC power supply is input from the emergency power supply even when the AC is interrupted, the normal / backup power supply switching circuit 5g and the backup battery 5h in the receiver may be unnecessary.

[0052] Figure 3 is an internal configuration diagram of the optical fiber detector 5b shown in Figure 1.

[0053] As shown in Figure 3, the optical fiber detector 5b has, as a light source, a semiconductor laser 5b1 that generates continuous light and outputs it to the optical fiber cable 3, and an optical transmission processor 5b3. The optical pulse from the optical transmission processor 5b3 is incident on the optical fiber cable 3 via the circulator 5b5. Here, a wavelength band of 1.55μm is used as the light source composed of the semiconductor laser 5b1 and the optical transmission processor 5b3. Thereby, as will be described later, the loss in the optical fiber cable 3 can be reduced, and the monitoring distance can be made longer.

[0054] When an optical pulse is incident on the optical fiber cable 3, Brillouin scattering occurs in the optical fiber cable 3, and a part of it returns to the incident side as Brillouin scattered light.

[0055] The optical fiber detector 5b, as an optical fiber measurement unit, has an optical reception processor 5b7 and an optoelectronic converter 5b9.

[0056] The Brillouin scattered light returning from the optical fiber cable 3 is input to the optical reception processor 5b7 via the circulator 5b5. The optical reception processor 5b7 refers to the optical signal from the semiconductor laser 5b1 and converts the optical frequency to an intermediate frequency in the GHz band that can be measured as an electrical signal by heterodyne detection. The Brillouin scattered light converted into an electrical signal is used by the optoelectronic converter 5b9 to measure the gain spectrum of the Brillouin scattered light. The measurement is obtained every few nanoseconds using the optoelectronic converter 5b9 such as a high-speed electrical spectrum analyzer. The acquired gain spectrum is analyzed by the signal processor 5b10, and the frequency shift of the Brillouin scattered light is obtained from the peak frequency of the gain spectrum and converted into temperature information, and the result is sent to the reception processing unit 5a.

[0057] Generally, the frequency shift of the Brillouin scattered light is about 11 GHz with respect to the input light, and it has a frequency shift of 1.18 MHz / °C.

[0058] Next, with reference to FIG. 4, the fire alarm method in the fire alarm system 1 described above will be explained.

[0059] FIG. 4 is a flowchart of the fire alarm method in the fire alarm system 1 shown in FIG. 1.

[0060] In step 101, based on the control of the reception processing unit 5a in the receiver 5, an optical pulse is incident on the optical fiber cable 3 from the optical fiber detector 5b.

[0061] Continuous light is generated by the semiconductor laser 5b1 in the optical fiber detector 5b, and the continuous light is converted into optical pulses by the optical transmission processor 5b3 and then incident on the optical fiber cable 3 through the circulator 5b5. As the incident optical pulses travel through the optical fiber cable 3, weak scattered light is generated.

[0062] Here, the measurement regions of Brillouin scattered light separated at predetermined intervals set in the optical fiber cable 3 will be described.

[0063] FIG. 5 is an explanatory diagram of each measurement region in the optical fiber cable 3 shown in FIG. 1.

[0064] As shown in FIG. 5, the optical fiber cable 3 is divided into a plurality of measurement regions R1 to RN at predetermined intervals. The predetermined interval is, for example, when the optical fiber cable 3 is 1600 m, it is divided every 2 m. Thereby, the position information of each 2 - m area can be obtained from the optical fiber cable 3 arranged in a building or the like, and temperature information based on the position information can be obtained. The position information is obtained based on the delay time from when the optical pulse is incident on the incident end 3a of the optical fiber cable 3 until the Brillouin scattered light returns to the incident end 3a, as will be described later.

[0065] In step 103, based on the control of the reception processing unit 5a in the receiver 5, the optical fiber detector 5b detects the Brillouin scattered light generated during the process of traveling through the optical fiber cable 3.

[0066] The Brillouin scattered light returned from the optical fiber cable 3 is input to the optical reception processor 5b7 through the circulator 5b5. The optical reception processor 5b7 refers to the optical signal from the semiconductor laser 5b1 and converts the optical frequency into an intermediate frequency in the GHz band that can be measured as an electrical signal by heterodyne detection, and measures the gain spectrum of the Brillouin scattered light. The gain spectrum of the Brillouin scattered light is acquired every several nanoseconds by the optoelectronic converter 5b9.

[0067] In step 105, the signal processor 5b10 of the optical fiber detector 5b acquires the position information of each measurement region in the optical fiber cable 3 based on the gain spectrum of the detected scattered light.

[0068] As shown in FIG. 5, based on the delay time from when the optical pulse is incident on the incident end 3a of the optical fiber cable 3 until the Brillouin scattered light returns to the incident end 3a, the signal processor 5b10 obtains the distance from the measurement regions R1 to RN where the backscattered light generated by the input optical pulse is generated to the incident end 3a as the position information.

[0069] In step 107, the signal processor 5b10 of the optical fiber detector 5b acquires the temperature information of each measurement region in the optical fiber cable 3 based on the gain spectrum of the detected scattered light.

[0070] Since the frequency of the Brillouin scattered light changes with the temperature change at the location where it is generated, here, the frequency change of the Brillouin scattered light in each measurement region of the optical fiber cable 3 is detected to obtain the temperature information of each measurement region.

[0071] The optical reception processor 5b7 converts the Brillouin scattered light returned from the optical fiber cable 3 via the circulator 5b5 into an intermediate frequency in the GHz band where the optical frequency can be measured as an electrical signal by heterodyne detection with reference to the optical signal from the semiconductor laser 5b1, and acquires it every few nanoseconds by the optoelectronic converter 5b9 as the gain spectrum. Here, the gain spectrum of the Brillouin scattered light at each position information obtained in step 105 becomes the temperature information of each measurement region R1 to RN.

[0072] In step 109, the temperature information of each measurement region R1 to RN in the optical fiber cable 3 is sent from the optical fiber detector 5b to the reception processing unit 5a via a predetermined interface, and in the reception processing unit 5a, temperature information processing such as fire determination is performed based on the temperature information of each measurement region R1 to RN in the optical fiber cable 3.

[0073] Here, the predetermined interface is a ModBus interface. Also, the fire determination based on the temperature information in each measurement area R1 to RN of the optical fiber cable 3 is performed by switching between a predetermined differential spot type algorithm or a constant temperature spot type algorithm or the like. The fire determination function based on the temperature information in each measurement area R1 to RN of the optical fiber cable 3 may be installed in the optical fiber detector 5b as a sensitivity fixing device.

[0074] The fire determination by a differential spot type algorithm or a constant temperature spot type algorithm or the like will be described below.

[0075] The differential spot type algorithm operates based on the rate of temperature rise in a certain unit time, and the sensed temperature does not remain constant. In the case of this machine, temperature information is collected at a sampling rate of 1 second. When there is a temperature change of 18°C or more within 15 seconds and the temperature change of 18°C or more continues for 5 seconds or more, it is determined as a fire. Or, when there is a temperature rise of 7°C or more (7°C / min) compared to the temperature 1 minute before, a temperature rise of 10.5°C or more compared to 1 minute and 30 seconds before 30 seconds later, and a temperature rise of 14°C or more compared to 2 minutes before 30 seconds later, it is determined as a fire.

[0076] The constant temperature spot type algorithm senses when a certain temperature is reached. In the case of this machine, when the measured value is equal to or higher than the set temperature (60°C) for 10 seconds or more, it is determined as a fire.

[0077] Finally, in step 111, the receiver 5 performs various alarm operations such as displaying a fire alarm based on the result of the temperature information processing.

[0078] The reception processing unit 5a of the receiver 5 displays the temperatures of the respective measurement areas R1 to RN in the display unit 5m based on the temperature information of the respective measurement areas R1 to RN in the optical fiber cable 3 from the optical fiber detector 5b, and issues a fire alarm when there is a temperature exceeding a predetermined temperature among the temperatures of the respective measurement areas R1 to RN.

[0079] When issuing a fire alarm, the reception processing unit 5a of the receiver 5 causes the display unit 5m to display an alarm for the measurement area where the temperature exceeds a predetermined temperature. For example, when the measurement area where the temperature exceeds the predetermined temperature is R3, the measurement area R3 is displayed in a red alarm color. At the same time, the reception processing unit 5a generates an alarm sound from the buzzer 5j via the signal input / output device 5c and the main audio output circuit 5i.

[0080] As described above, in the fire alarm system implementing the present invention, since the receiver 5 obtains the temperature information of each measurement area R1 to RN in the optical fiber cable 3 from the Brillouin scattered light returned from the optical fiber cable 3 and makes a fire determination, the following effects can be obtained.

[0081] It is possible to provide a fire alarm system and a fire alarm method capable of shortening the measurement period, surely identifying the measurement points, and making the fire determination unaffected by noise.

[0082] The effect of shortening the measurement period will be described.

[0083] In the present invention, since the frequency change of the Brillouin scattered light returned from the optical fiber cable 3 is measured, data averaging processing or the like required to obtain reliable measurement accuracy in the measurement of conventional Raman scattered light is no longer necessary, and the measurement period can be shortened.

[0084] The effect of surely identifying the measurement points will be described.

[0085] In a conventional optical fiber fire alarm system, a repeater detects the reflected light of the pulsed light incident on the optical fiber cable laid in a building, the repeater measures the reflected light to detect the temperature and makes a fire determination, and the receiver that inputs the fire determination issues a fire alarm. Therefore, the receiver cannot obtain the temperature information of each measurement point of the optical fiber cable and cannot identify the measurement points.

[0086] In contrast, in the present invention, the receiver 5 obtains the temperature information of each measurement region R1 to RN in the optical fiber cable 3 from the Brillouin scattered light returned from the optical fiber cable 3. Therefore, the receiver 5 can directly obtain the temperature information and identify the measurement points based on the temperature information.

[0087] The effect that the fire determination is not affected by noise will be described.

[0088] In the conventional optical fiber fire alarm system, since the receiver receives the fire determination signal via the power line from the repeater, noise is added to the fire determination signal, and the fire determination may be affected by the noise.

[0089] In contrast, in the present invention, inside the receiver 5, the optical fiber detector 5b obtains the temperature information from the Brillouin scattered light returned from the optical fiber cable 3, and sends the temperature information to the reception processing unit 5a via the ModBus interface. Therefore, no noise is added to the temperature information, and the fire determination is not affected by the noise.

[0090] Also, in the embodiment of the present invention, a wavelength of 1.55 μm is used as the light source composed of the semiconductor laser 5b1 and the optical transmission processor 5b3.

[0091] FIG. 7 is a graph showing the loss wavelength dependence of the silica-based optical fiber used in the embodiment of the present invention.

[0092] As can be seen from FIG. 7, since a wavelength of 1.55 μm is used as the light source, the loss in the optical fiber cable 3 becomes the lowest value. Thus, since the loss in the optical fiber cable 3 can be reduced, the monitoring distance of the optical fiber cable 3 can be extended accordingly.

[0093] Next, with reference to FIG. 6, a modification of the first embodiment of the present invention will be described.

[0094] FIG. 6 is an internal configuration diagram of the optical fiber detector 5b in a modification of the first embodiment. In the modification, the configuration operation of the optical fiber detector 5b in the receiver 5 is different. Since other configuration operations are the same as those of the first embodiment described above, redundant explanations are omitted.

[0095] As shown in FIG. 6, the optical fiber detector 5b in the modification has, as a transmission unit, a semiconductor laser 5b1 that generates continuous light and outputs it to the optical fiber cable 3, and an optical transmission processor 5b3. The optical pulse from the optical transmission processor 5b3 is incident on the optical fiber cable 3 via the circulator 5b5.

[0096] When an optical pulse is incident on the optical fiber cable 3, Brillouin scattering occurs in the optical fiber cable 3, and a part of it returns to the incident side as Brillouin scattered light.

[0097] The optical fiber detector 5b has, as an optical fiber measurement unit, an acousto-optic modulator 5b11, a time delay device 5b13, an interferometer 5b15, a frequency oscillator 5b17, and a phase comparator 5b19.

[0098] The Brillouin scattered light returning from the optical fiber cable 3 is input to the acousto-optic modulator 5b11 and the time delay device 5b13 via the circulator 5b5. The outputs of the acousto-optic modulator 5b11 and the time delay device 5b13 are input to the interferometer 5b15, and the output of the interferometer 5b15 is input to the phase comparator 5b19.

[0099] One of the Brillouin scattered light branched by the circulator 5b5 is frequency-shifted by the acousto-optic modulator 5b11, and the other of the Brillouin scattered light branched by the circulator 5b5 is given a predetermined delay time by the time delay device 5b13, and both of them are input to the interferometer 5b15.

[0100] In the interferometer 5b15, a beat signal corresponding to a frequency shift is obtained, and the frequency change of the Brillouin scattered light is detected and output as a phase change of the beat signal. In the phase comparator 5b19, the beat signal with the phase shift information from the interferometer 5b15 is converted into an intensity signal, and then converted into a frequency shift amount. The obtained frequency shift amount is sent from the phase comparator 5b19 to the signal processor 5b10 and converted into temperature information, and the result is sent to the reception processing unit 5a.

[0101] As described above, in the modification of the first embodiment, the Brillouin scattered light is branched into two, and the frequency change of the Brillouin scattered light is detected as a phase change in the beat signal by the interferometer 5b15. By extracting this phase change by the phase comparator 5b19, the Brillouin frequency shift amount can be calculated without requiring frequency sweeping. Compared with the first embodiment, the frequency shift amount of the Brillouin scattered light can be obtained without measuring the gain spectrum of the Brillouin scattered light, so the measurement time can be shortened by the time required for frequency sweeping compared with the frequency sweeping method, and the measurement can be speeded up.

[0102] Also, for example, the temperature accuracy can be improved by taking the moving average of the temperature information for five regions (RN-2 to RN+2) in the measurement region, and even in this case, a short measurement time can be achieved.

[0103] Referring to FIGS. 8 to 12, a second embodiment of the fire alarm system according to the present invention will be described.

[0104] FIG. 8 is an overall configuration diagram of a second embodiment of the fire alarm system according to the present invention.

[0105] In the fire alarm system 21 of the second embodiment, a sensor 20 that senses a fire using an optical fiber cable 20a is connected to a receiver 5 that issues an alarm for the fire sensed by the sensor 20.

[0106] As shown in FIG. 8, the fire alarm system 21 has a detector 20. The detector 20 includes an optical fiber cable 20a laid in a building such as a building to be detected for a fire, and a detection unit 20b that measures the temperature of each measurement area in the optical fiber cable 20a and determines a fire from the temperature information of each measurement area in the optical fiber cable 3.

[0107] When the detector 20 determines a fire, the fire determination is sent to the receiver 5, and the receiver 5 issues a fire alarm.

[0108] The configuration of the detector 20 will be described.

[0109] As shown in FIG. 8, one end of the optical fiber cable 20a is connected to the detection unit 20b, and a termination box 20c is connected to the other end of the optical fiber cable 20a. In the optical fiber cable 20a, measurement areas of Brillouin scattered light separated at predetermined intervals are set as will be described later.

[0110] The optical fiber cable 20a uses a single-mode fiber. Since the optical fiber cable 20a is a single-mode fiber, the monitoring distance can be set to 5 km. The optical fiber cable 20a is made of a silica-based optical fiber.

[0111] The detection unit 20b of the detector 20 will be described.

[0112] FIG. 9 is an internal configuration diagram of the detection unit 20b of the detector 20 shown in FIG. 8.

[0113] The detection unit 20b has a function of measuring the temperature of each measurement area in the optical fiber cable 20a, determining a fire from the temperature information of each measurement area in the optical fiber cable 20a, and transmitting the fire determination information to the receiver 5. The detection unit 20b further has a function of detecting a disconnection in the optical fiber cable 20a and transmitting the disconnection information in the optical fiber cable 20a to the receiver 5. The receiver 5 performs a failure display (alarm) of the optical fiber cable disconnection based on the disconnection information.

[0114] The disconnection in the optical fiber cable 20a is determined, for example, by the fact that Brillouin scattered light is no longer detected after a certain position in the optical fiber cable 20a, and the position is specified as the disconnection position. The disconnection position is calculated from the arrival delay time of the Brillouin scattered light with respect to the incident light.

[0115] The detection unit 20b monitors the temperature measurement accuracy, and constantly measures and calculates whether the deviation (standard deviation: 1σ) of the measured temperature by the optical fiber and the temperature sensor built in the detection unit 20b is within a predetermined threshold range to detect abnormalities. When an abnormality is detected, it has a function of transmitting temperature measurement accuracy degradation information to the receiver 5. The receiver 5 performs a failure display (alarm) of the detection unit 20b based on the temperature measurement accuracy degradation information.

[0116] As shown in FIG. 9, the detection unit 20b includes a semiconductor laser 20b1 that generates continuous light and outputs it to the optical fiber cable 20a, and an optical transmission processor 20b3 as a light source. A power supply of AC100v or higher is supplied to the semiconductor laser 20b1 via the power supply unit 20b15.

[0117] The optical pulse from the optical transmission processor 20b3 is incident on the optical fiber cable 20a via the circulator 20b5. Here, a wavelength band of 1.55 μm is used as the light source composed of the semiconductor laser 20b1 and the optical transmission processor 20b3. Thereby, as will be described later, the loss in the optical fiber cable 20a can be reduced, and the monitoring distance can be made longer.

[0118] When the laser light is incident on the optical fiber cable 20a, Brillouin scattering occurs in the optical fiber cable 20a, and a part of it returns to the incident side as Brillouin scattered light.

[0119] The detection unit 20b includes an optical reception processor 20b7 and an optoelectronic converter 20b9 as a measurement unit.

[0120] The Brillouin scattered light returned from the optical fiber cable 20a is input to the optical reception processor 20b7 via the circulator 20b5. The optical reception processor 20b7 refers to the optical signal from the semiconductor laser 20b1 and converts the optical frequency to an intermediate frequency in the GHz band where the optical frequency can be measured as an electrical signal by heterodyne detection, and measures the gain spectrum of the Brillouin scattered light.

[0121] The detection unit 20b has, as a fire determination unit, a photoelectric converter 20b9, a signal processor 20b10, a contact switch 20b11, and an I / O unit 20b13.

[0122] The measured gain spectrum is acquired every several nanoseconds by the photoelectric converter 20b9. The acquired gain spectrum is analyzed by the signal processor 20b10 to obtain the frequency shift of the Brillouin scattered light from the peak frequency of the gain spectrum and is converted into temperature information, and is input to the contact switch 20b11 and the I / O unit 20b13, and a fire determination is made by the contact switch 20b11.

[0123] The fire determination process in the contact switch 20b11 will be described in detail later.

[0124] The result of the fire determination by the contact switch 20b11 is sent to the signal input / output unit 5c of the receiver 5.

[0125] Generally, the frequency shift of the Brillouin scattered light is about 11 GHz with respect to the input light and has a frequency shift of 1.18 MHz / °C.

[0126] The receiver 5 will be described.

[0127] FIG. 10 is an internal configuration diagram of the receiver 5 shown in FIG. 8.

[0128] As shown in FIG. 10, the receiver 5 includes a reception processing unit 5a composed of a panel PC, a signal input / output device 5c composed of an I / O module connected to the reception processing unit 5a, an AC input unit 5d that receives an AC input, a voltage conversion circuit 5e connected to the AC input unit 5d, an indicator lamp output circuit 5f connected to the voltage conversion circuit 5e, a normal / backup power supply switching circuit 5g that is connected to the voltage conversion circuit 5e and is also connected to the reception processing unit 5a and the signal input / output device 5c, a backup battery 5h connected to the normal / backup power supply switching circuit 5g, a main audio output circuit 5i connected to the signal input / output device 5c, a buzzer 5j connected to the main audio output circuit 5i, a transfer message output circuit 5k connected to the signal input / output device 5c and the normal / backup power supply switching circuit 5g, a local audio output circuit 5l connected to the signal input / output device 5c and the normal / backup power supply switching circuit 5g, a display unit 5m composed of a liquid crystal monitor or the like connected to the reception processing unit 5a, and an operation unit 5n for performing various operations connected to the reception processing unit 5a.

[0129] The detection unit 20b of the sensor 20 and the transmitter 11 are connected to the signal input / output device 5c, the indicator lamp 9 is connected to the indicator lamp output circuit 5f, the related equipment 13 is connected to the transfer message output circuit 5k, and the local audio device 15 is connected to the local audio output circuit 5l.

[0130] The functions of each part of the receiver 5 will be described.

[0131] The reception processing unit 5a controls each part within the receiver 5 and external devices connected to the receiver 5 in order to monitor the state of the fire alarm system 1.

[0132] Based on the fire determination received from the sensor 20 by controlling the receiver 5 and external devices connected to the receiver 5, the reception processing unit 5a performs a fire alarm display.

[0133] The reception processing unit 5a outputs the main sound, local sound, and transfer report output control signal to the signal input / output unit 5c, records the event (fire, failure) information, and displays the event information by operation. Further, the reception processing unit 5a records the temperature information for a certain period and displays the temperature trend information of a specified point, etc. by operation.

[0134] For this purpose, the reception processing unit 5a has a display unit 5m for displaying fire displays, operation status, status monitoring diagrams, trend graphs, history lists, various abnormalities, etc., and an operation unit 5n for performing operations such as recovery, main sound stop, tests (fire, backup battery), inspections (transfer report stop, local sound stop), etc.

[0135] The signal input / output unit 5c outputs the operation signal from the transmitter 11, which is an external device, to the reception processing unit 5a, outputs a ringing signal to the main sound output circuit 5i according to the control signal from the reception processing unit 5a, outputs a ringing control signal for the local sound device 15 to the local sound output circuit 5l according to the control signal from the reception processing unit 5a, and controls the ON / OFF output of the transfer report signal to the transfer report output circuit 5k according to the control signal from the reception processing unit 5a.

[0136] The voltage conversion circuit 5e converts the AC input from the AC input unit 5d into a power supply for the receiver internal circuit (DC24V), converts the AC input from the AC input unit 5d into a power supply for the backup power charging circuit (DC48V), and converts the AC input from the AC input unit 5d into a power supply for the indicator lamp (AC24V).

[0137] The normal / backup power supply switching circuit 5g automatically switches the power supply for the receiver circuit from the normal power supply to the backup power supply when the AC power supply is cut off, and automatically switches from the backup power supply to the normal power supply after the AC power supply is restored. Also, the normal / backup power supply switching circuit 5g charges the backup battery 5h at a constant current according to the backup power supply capacity.

[0138] The normal / backup power supply switching circuit 5g has a function of detecting abnormal voltages in the receiver circuit and the backup battery, and transmitting an abnormal voltage signal to the reception processing unit 5a when the voltage value is less than 20.4V. In the reception processing unit 5a, a failure display (alarm) is performed as a circuit abnormality according to the abnormal voltage signal.

[0139] When an emergency power supply with an inverter power supply method is always provided outside the receiver, since the AC power is input from the emergency power supply even when the AC is cut off, the normal / backup power supply switching circuit 5g and the backup battery 5h in the receiver may not be necessary.

[0140] Referring to FIG. 11, the fire alarm method in the second embodiment of the above-described fire alarm system 1 will be described.

[0141] FIG. 11 is a flowchart of the fire alarm method in the second embodiment of the fire alarm system 1 shown in FIG. 8.

[0142] In step 201, an optical pulse is incident on the optical fiber cable 3 from the detection unit 20b.

[0143] Continuous light is generated from the semiconductor laser 20b1 in the detection unit 20b, and the continuous light is converted into an optical pulse by the optical transmission processor 20b3 and is incident on the optical fiber cable 20a through the circulator 20b5. In the process of the incident optical pulse traveling through the optical fiber cable 20a, weak scattered light is generated.

[0144] Here, the measurement regions of the Brillouin scattered light separated at predetermined intervals set in the optical fiber cable 20a will be described.

[0145] Since each measurement region of the optical fiber cable 20a in the second embodiment is the same as the explanatory diagram of each measurement region of the optical fiber cable 3 in the first embodiment shown in FIG. 5, it will be described with reference to FIG. 5.

[0146] As shown in FIG. 5, the optical fiber cable 20a is divided into a plurality of measurement regions R1 to RN at predetermined intervals. The predetermined interval is, for example, when the optical fiber cable 20a is 1600 m, it is divided every 2 m. Thus, the position information of the area every 2 m can be obtained by the optical fiber cable 20a disposed in a building or the like, and the temperature information based on the position information can be obtained. The position information is obtained based on the delay time from when the optical pulse is incident on the incident end 3a of the optical fiber cable 20a until the Brillouin scattered light returns to the incident end 3a, as will be described later.

[0147] In step 203, the detection unit 20b detects the Brillouin scattered light generated in the process of the optical pulse traveling through the optical fiber cable 20a.

[0148] The Brillouin scattered light returned from the optical fiber cable 20a is input to the optical reception processor 20b7 via the circulator 20b5. The optical reception processor 20b7 refers to the optical signal from the semiconductor laser 20b1 and converts the optical frequency to an intermediate frequency in the GHz band that can be measured as an electrical signal by heterodyne detection, and measures the gain spectrum of the Brillouin scattered light. The gain spectrum of the Brillouin scattered light is acquired every several ns by the optoelectronic processor 20b9.

[0149] In step 205, the fire determination process by the detection unit 20b is performed.

[0150] Referring to FIG. 12, the fire determination process by the detection unit 20b will be described.

[0151] FIG. 12 is a flowchart of the fire determination process by the detection unit 20b in step 205 of FIG. 11.

[0152] In step 205a of FIG. 12, the I / O unit 20b13 of the detection unit 20b is initialized. In step 205b, the signal processor 20b10 acquires the position information of each measurement region in the optical fiber cable 20a.

[0153] The signal processor 20b10 of the detection unit 20b acquires the position information of each measurement region in the optical fiber cable 20a based on the gain spectrum of the detected scattered light.

[0154] More specifically, as shown in FIG. 5, the signal processor 20b10 obtains the distance from the measurement regions R1 to RN where the backscattered light generated by the input optical pulse to the incident end based on the delay time from when the optical pulse is incident on the incident end of the optical fiber cable 20a until the Brillouin scattered light returns to the incident end, and uses it as the position information.

[0155] The signal processor 20b10 acquires the temperature information of each measurement region in the optical fiber cable 20a based on the gain spectrum of the detected scattered light.

[0156] Since the frequency of the Brillouin scattered light changes with the temperature change at the location where it is generated, here, the frequency change of the Brillouin scattered light in each measurement region of the optical fiber cable 20a is detected to obtain the temperature information of each measurement region.

[0157] The optical reception processor 20b7 converts the Brillouin scattered light returned from the optical fiber cable 20a via the circulator 20b into an intermediate frequency in the GHz band where the optical frequency can be measured as an electrical signal by heterodyne detection with reference to the optical signal from the semiconductor laser 20b1, and acquires it as a gain spectrum every few nanoseconds by the optoelectronic converter 20b9. Here, the gain spectrum of the Brillouin scattered light at each obtained position information becomes the temperature information of each measurement region R1 to RN.

[0158] In step 205c, it is asked whether a fire has occurred and a fire determination is made. If a fire determination is made in step 205c (YES in step 205c), in step 205d, the contact switch 20b11 makes a fire determination.

[0159] The contact switch 20b11 performs a fire determination for each measurement area R1 to RN of the optical fiber cable 20a based on the temperature information of each measurement area in the optical fiber cable 20a sent from the signal processor 20b10 via a predetermined interface, and the fire occurrence location is specified.

[0160] Here, the contact switch 20b11 consists of a computer and performs a fire determination for each measurement area R1 to RN of the optical fiber cable 20a based on the temperature information of each measurement area in the optical fiber cable 20a.

[0161] That is, the contact switch 20b11 determines that a fire has occurred when there is a temperature exceeding a predetermined temperature among the temperatures of each measurement area R1 to RN based on the temperature information of each measurement area R1 to RN in the optical fiber cable 20a.

[0162] Here, the predetermined interface is a ModBus interface. Also, the fire determination based on the temperature information of each measurement area R1 to RN of the optical fiber cable 20a is performed by switching between a predetermined differential spot type algorithm or a constant temperature spot type algorithm, etc.

[0163] The fire determination by a differential spot type algorithm or a constant temperature spot type algorithm, etc. will be described below.

[0164] The differential spot type algorithm operates based on the rate of temperature rise in a certain unit time, and the sensed temperature does not remain constant. In the case of this machine, temperature information is collected at a sampling rate of 1 second. When there is a temperature change of 18°C or more within 15 seconds and the temperature change of 18°C or more continues for 5 seconds or more, it is determined as a fire. Or, when there is a temperature rise of 7°C or more compared to the temperature 1 minute ago (7°C / min), and there is a temperature rise of 10.5°C or more compared to 1 minute and 30 seconds ago 30 seconds later, and further there is a temperature rise of 14°C or more compared to 2 minutes ago 30 seconds later, it is determined as a fire.

[0165] The constant-temperature spot-type algorithm senses when a certain temperature is reached. In the case of this machine, when the measured value is equal to or higher than the set temperature (60°C) for 10 seconds or more, it is determined that there is a fire.

[0166] In step 205e, the contact switch 20b11 issues an output command for the area where a fire has occurred to the I / O unit 20b13. In step 205f, it is determined whether a recovery signal input has been received from the I / O unit 20b13.

[0167] If a recovery signal input is received from the I / O unit 20b13 in step 205f (YES in step 205f), in step 205g, it is determined whether the fire detection has ended. If the fire detection has ended (YES in step 205g), the fire determination process by the detection unit 20b is terminated.

[0168] If NO in the above steps 205c and 205f, the process returns to step 205b. If NO in step 205g, the process returns to step 205a.

[0169] Returning to Fig. 11, finally, in step 207, the receiver 5 performs various alarm operations such as displaying a fire alarm based on the fire determination information from the detection unit 20b of the sensor 20.

[0170] The reception processing unit 5a of the receiver 5 issues a fire alarm for the area determined to have a fire within each measurement area R1 to RN based on the fire information from the detection unit 20b.

[0171] That is, when issuing a fire alarm, the reception processing unit 5a of the receiver 5 causes the display unit 5m to display an alarm for the measurement area where the temperature exceeds the predetermined temperature. For example, if the measurement area where the temperature exceeds the predetermined temperature is R3, the measurement area R3 is displayed in a red alarm color. At the same time, the reception processing unit 5a generates an alarm sound from the buzzer 5j via the signal input / output unit 5c and the main audio output circuit 5i.

[0172] Thus, in the second embodiment of the fire alarm system according to the present invention, the sensor 20 obtains temperature information of each measurement region R1 to RN in the optical fiber cable 20a based on the Brillouin scattered light returned from the optical fiber cable 20a, and makes a fire determination. Since the receiver 5 issues an alarm based on the fire determination, the following effects can be obtained.

[0173] It is possible to speed up the measurement cycle, reliably identify the measurement points, and provide a fire alarm system and a fire alarm method in which the fire determination is not affected by noise.

[0174] First, the effect of speeding up the measurement cycle will be described.

[0175] In the present invention, since the frequency change of the Brillouin scattered light returned from the optical fiber cable 20a is measured, data averaging processing and the like required to obtain reliable measurement accuracy in the measurement of conventional Raman scattered light are not necessary, and the measurement cycle can be speeded up.

[0176] The effect of being able to reliably identify the measurement points will be described.

[0177] In a conventional optical fiber fire alarm system, a repeater detects the reflected light of the pulsed light incident on the optical fiber cable laid in a building, the repeater measures the reflected light to detect the temperature and makes a fire determination, and the receiver that receives the fire determination issues a fire alarm. Therefore, the receiver cannot obtain the temperature information of each measurement point of the optical fiber cable and cannot identify the measurement points.

[0178] On the other hand, in the second embodiment of the fire alarm system according to the present invention, the sensor 20 obtains temperature information of each measurement region R1 to RN in the optical fiber cable 20a based on the Brillouin scattered light returned from the optical fiber cable 20a, and makes a fire determination. Since the receiver 5 issues an alarm based on the fire determination, the receiver 5 can directly obtain the fire information and can issue a fire alarm based on the fire information.

[0179] In the embodiment, a wavelength of 1.55 μm is used as the light source composed of the semiconductor laser 5b1 and the optical transmission processor 5b3.

[0180] FIG. 7 is a graph showing the loss wavelength dependence of the silica optical fiber used in the second embodiment of the present invention.

[0181] As can be seen from FIG. 7, since a wavelength of 1.55 μm is used as the light source, the loss in the optical fiber cable 3 becomes the lowest value. Thus, since the loss in the optical fiber cable 20a can be reduced, the monitoring distance of the optical fiber cable 20a can be increased accordingly.

[0182] The present invention is not limited to the embodiments of the invention described above, and can be implemented in other aspects by making appropriate changes.

Explanation of Signs

[0183] 1... Fire alarm system, 3, 20a... Optical fiber cable, 5... Receiver, 5a... Reception processing unit, 5b... Optical fiber detector, 5c... Signal input / output device, 5d... AC input unit, 5e... Voltage conversion circuit, 5f... Indicator light output circuit, 5g... Normal / backup power supply switching circuit, 5h... Backup battery, 5i... Main acoustic output circuit, 5j... Buzzer, 5k... Forwarding message output circuit, 5l... District acoustic output circuit, 5m... Display unit, 5n... Operation unit, 20... Sensor 20b... Detection unit

Claims

1. A receiver that acquires temperature information from the frequency change of Brillouin scattered light from an optical fiber cable laid on a fire detection target and determines a fire from the acquired temperature information, when the temperature information shows a temperature change of a predetermined amount or more within a first unit time and the temperature change of the predetermined amount or more continues for a second unit time or more that is shorter than the first unit time, it is determined that a fire has occurred, or or, when the temperature information shows a temperature of a predetermined value or more and the temperature of the predetermined value or more continues for a third unit time or more, it is determined that a fire has occurred, sends predetermined pulsed light to the optical fiber cable, detects the temperature of each location of the fire detection target from the Brillouin scattered light that is the reflected light from the optical fiber cable, and transmits information such as a fire alarm based on the detected temperature of each location, has an optical fiber detector that measures the temperature of each measurement region in the optical fiber cable, has a reception processing unit that determines a fire based on the temperature information received from the optical fiber detector and performs a fire alarm display when a fire is determined, the optical fiber detector monitors the temperature measurement accuracy, constantly measures and calculates whether the deviation between the measurement temperature by the optical fiber and the temperature sensor built in the optical fiber detector is within a predetermined threshold range to detect an abnormality, and when the abnormality is detected, transmits temperature measurement accuracy degradation information to the reception processing unit, and the reception processing unit is configured to perform a failure display of the optical fiber detector based on the temperature measurement accuracy degradation information.

2. The optical fiber detector according to claim 1, comprising an acousto-optic modulator, a time delay device, and an interferometer, branches the Brillouin scattered light from the optical fiber cable into two, inputs each of the branched Brillouin scattered light into the acousto-optic modulator and the time delay device, inputs the first branched light frequency-shifted by the acousto-optic modulator and the second branched light delayed by a predetermined delay time by the time delay device into the interferometer to obtain a corresponding beat signal, and is configured to obtain the temperature information based on the frequency change of the Brillouin scattered light based on the phase change of the obtained beat signal.

3. The receiver according to claim 1 or claim 2, wherein the reception processing unit includes a display unit for displaying fire indications, operation status, status monitoring diagrams, trend graphs, history lists, various abnormalities, etc., and an operation unit for performing operations such as restoration, main sound stop, test, inspection, etc.

4. The receiver according to any one of claims 1 to 3, wherein the optical fiber cable is a single-mode fiber, and a wavelength band of 1.55 μm is used as a light source of predetermined pulsed light to be sent to the optical fiber cable.

5. A fire alarm system that detects and alarms a fire, an optical fiber cable laid on a fire detection target, a receiver that sends predetermined pulsed light to the optical fiber cable, obtains temperature information of each location of the fire detection target from a frequency change of Brillouin scattered light that is reflected light from the optical fiber cable, and transmits information such as a fire alarm based on the obtained temperature information of each location, comprising: the receiver determines that a fire has occurred when the temperature information shows a temperature change of a predetermined amount or more within a first unit time, and the temperature change of the predetermined amount or more continues for a second unit time or more that is shorter than the first unit time, or the receiver determines that a fire has occurred when the temperature information shows a temperature equal to or higher than a threshold value, and the temperature equal to or higher than the threshold value continues for a third unit time or more, the receiver has an optical fiber detector that measures the temperature of each measurement area in the optical fiber cable, the receiver has a reception processing unit that performs a fire determination based on the temperature information received from the optical fiber detector, and performs a fire alarm display when a fire is determined, the optical fiber detector monitors the temperature measurement accuracy, constantly measures and calculates whether a deviation between the measurement temperature by the optical fiber and the temperature sensor built in the optical fiber detector is within a predetermined threshold range to detect an abnormality, and when the abnormality is detected, transmits temperature measurement accuracy degradation information to the reception processing unit, and the reception processing unit is configured to perform a failure display of the optical fiber detector based on the temperature measurement accuracy degradation information.

6. The reception processing unit includes an acousto-optic modulator, a time delay device, and an interferometer. The Brillouin scattered light from the optical fiber cable is branched into two, and each of the branched Brillouin scattered lights is input to the acousto-optic modulator and the time delay device. The first branched light frequency-shifted by the acousto-optic modulator and the second branched light delayed by a predetermined delay time by the time delay device are input to the interferometer to obtain a corresponding beat signal, and the temperature information is obtained based on the frequency change of the Brillouin scattered light based on the phase change of the obtained beat signal. The fire alarm system according to claim 5, which is configured as such.

7. A fire alarm system that detects and alarms a fire, an optical fiber cable laid on a fire detection target, a predetermined pulsed light is sent to the optical fiber cable, the temperature of each location of the fire detection target is detected from the frequency change of the Brillouin scattered light, which is the reflected light from the optical fiber cable, and a detector that performs a fire determination based on the detected temperature of each location is provided, when the temperature information shows a temperature change of a predetermined amount or more within a first unit time and the temperature change of the predetermined amount or more continues for a second unit time or more, which is shorter than the first unit time, the detector determines that a fire has occurred, or when the temperature information shows a temperature of a predetermined value or more and the temperature of the predetermined value or more continues for a third unit time or more, the detector determines that a fire has occurred, an optical fiber cable laid on the fire detection target, a predetermined pulsed light is sent to the optical fiber cable, and a detector that detects the temperature of each location of the fire detection target from the Brillouin scattered light, which is the reflected light from the optical fiber cable, and performs a fire determination based on the detected temperature of each location is provided, a receiver that transmits information such as a fire alarm based on the fire determination from the detector, the detector monitors the temperature measurement accuracy, constantly measures and calculates whether the deviation between the measured temperatures by the optical fiber and the temperature sensor built in the detector is within a predetermined threshold range to detect an abnormality. When the abnormality is detected, temperature measurement accuracy degradation information is transmitted to the receiver, and the receiver is configured to display a failure of the detector based on the temperature measurement accuracy degradation information. The fire alarm system is configured as such.

8. The optical fiber cable is a single-mode fiber, and the fire alarm system according to any one of Claims 5 to 7, which uses a wavelength band of 1.55 μm as a light source of predetermined pulsed light to be sent to the optical fiber cable.

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