Aerosol detection system

Abstract

This invention provides an aerosol detection system that allows for the determination of when the light source needs to be replaced by monitoring the light emitted from the light source. [Solution] An output monitoring unit 17 is positioned between the laid optical fiber 2 and the multiplexer / demultiplexer 12e. This output monitoring unit 17 consists of a pair of optical connectors 17a positioned on both sides and an optical adapter sandwiched between the pair of optical connectors. A portion of the laser light emitted from the light source unit 12a is reflected at the interface between the tip surfaces of the ferrules of the output monitoring unit 17 and is received by the light receiving unit 12b after a certain period of time. The reflected light intensity received by the light receiving unit 12b is compared with the replacement light intensity threshold, and the processing unit determines that it is time to replace the semiconductor laser when the number of detections in which the reflected light intensity in a predetermined time is less than or equal to the replacement light intensity threshold exceeds the detection threshold.

Description

Technical Field

[0001] The present invention relates to an aerosol detection system that emits light into an aerosol detection target space and receives reflected light from the aerosol to detect the aerosol in the aerosol detection target space.

Background Art

[0002] Patent Document 1 discloses a fire smoke detection device including a plurality of laser radar units arranged at predetermined intervals, for example, every 50 m, in the roadside strip in a tunnel in the extension direction which is the traveling direction into the tunnel, and a monitoring unit connected to these plurality of laser radar units via a communication line.

[0003] Scan data of scattered light received by the light receiving unit of the laser radar unit is transmitted to the monitoring unit side via the communication unit, and smoke derived from a fire is detected in the monitoring unit based on the data from the laser radar unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the semiconductor laser which is the light emitting unit of the laser radar unit has a lifespan and requires periodic replacement, and power supply is required for each installation location of the laser radar unit. Replacement of such a light emitting unit and installation of a power source etc. need to be carried out for each installation location of the laser radar unit, which is laborious. Furthermore, there is also a risk of fire in the tunnel due to sparking caused by a short circuit in the base etc. of the semiconductor laser.

[0006] Furthermore, semiconductor lasers change their characteristics with temperature, and high temperatures at the installation site can lead to reduced output, failure of the semiconductor laser, and adverse effects on its lifespan.

[0007] Therefore, even if the semiconductor laser is replaced, for example, every year, its service life may be less than one year depending on the installation environment. In such cases, the monitoring unit will detect an abnormality in the output of the semiconductor laser and perform the replacement work. In such cases, a problem arises in that smoke originating from a fire cannot be detected until the semiconductor laser is replaced.

[0008] The object of the present invention is to provide an aerosol detection system that simplifies the replacement of the light source by housing multiple light transmitting and receiving units, which are unitized light source and light receiving units, in a single housing, and that allows for the determination of when the light source needs to be replaced by monitoring the light emitted from the light source. [Means for solving the problem]

[0009] The aerosol detection system according to the present invention for achieving the above objective comprises an aerosol detection device for detecting aerosols floating in an aerosol detection target space, and a plurality of head units connected to the aerosol detection device via laid optical fibers and installed in the aerosol detection target space, wherein the housing of the aerosol detection device includes one or more light transmitting / receiving units connected to each head unit via the laid optical fibers, and one processing unit connected to the one or more light transmitting / receiving units for detecting the aerosols, and the light transmitting / receiving unit comprises a light source unit for emitting laser light, a light receiving unit for receiving the emitted light reflected by the aerosol, a multiplexer / demultiplexer for bundling the light transmitting optical fiber from the light source unit and the light receiving optical fiber to the light receiving unit in a coaxial state, and an output monitoring unit installed between the multiplexer / demultiplexer and the laid optical fiber. The output monitoring unit is composed of a pair of optical connectors arranged on both sides and an optical adapter sandwiched between the pair of optical connectors, and the processing unit determines whether to replace the light source based on the reflected light intensity received by the light receiving unit after a certain period of time, which is the reflection of a portion of the laser light emitted from the light source unit at the interface between the tip surfaces of the ferrules of the pair of optical connectors, and a replacement light intensity threshold. It is characterized by the following.

[0010] The aerosol detection system according to the present invention for achieving the above objective comprises an aerosol detection device for detecting aerosols floating in an aerosol detection target space, and a plurality of head units connected to the aerosol detection device via laid optical fibers and installed in the aerosol detection target space, wherein the housing of the aerosol detection device includes one or more light transmitting and receiving units connected to each head unit via the laid optical fibers, and one processing unit connected to the one or more light transmitting and receiving units for detecting the aerosols, and the light transmitting and receiving unit includes a light source unit that emits laser light and a light receiving unit that reacts with the aerosols The system comprises a pair of first and second light-receiving units that receive emitted light, a first multiplexer / demultiplexer that splits the light-transmitting optical fiber through which the laser light emitted from the light source propagates into first and second branched optical fibers, a second multiplexer / demultiplexer that splits the reflected light from the first laid optical fiber into the first branched optical fiber and a first light-receiving optical fiber that propagates to the first light-receiving unit, and a third multiplexer / demultiplexer that splits the reflected light from the second laid optical fiber into the second branched optical fiber and a second light-receiving optical fiber that propagates to the second light-receiving unit, with first and second output monitoring units arranged between the second and third multiplexer / demultiplexers and the first and second laid optical fibers, respectively. The output monitoring unit is composed of a pair of optical connectors arranged on both sides and an optical adapter sandwiched between the pair of optical connectors, and the processing unit determines whether to replace the light source based on the reflected light intensity received by the light receiving unit after a certain period of time, which is the reflection of a portion of the laser light emitted from the light source unit at the interface between the tip surfaces of the ferrules of the pair of optical connectors, and a replacement light intensity threshold. It is characterized by the following. [Effects of the Invention]

[0011] According to the aerosol detection system of the present invention, by housing multiple light-transmitting and light-receiving units, which are unitized light-emitting and light-receiving units, in a single housing, the replacement work of the light-emitting unit is simplified, temperature control of the light-emitting unit is made easier, and only the light-emitting unit can be replaced from the light-transmitting and light-receiving unit, allowing the replacement work to be performed in one location. Furthermore, by providing an output monitoring unit in the light-transmitting and light-receiving unit and monitoring the light emitted from the light-emitting unit, it is possible to easily determine whether the power of the emitted light is sufficient or whether the light-emitting unit has reached the time for replacement. [Brief explanation of the drawing]

[0012] [Figure 1]This is a block diagram of an aerosol detection system according to an embodiment of the present invention. [Figure 2] This is a block diagram of the light transmitting / receiving unit and the head unit. [Figure 3] This is an explanatory diagram of the output monitoring section when a pair of optical connectors are connected to an optical adapter. [Figure 4] This is a block diagram of the light transmitting / receiving unit and head unit of another embodiment. [Figure 5] This is a block diagram of the light transmitting / receiving unit and head unit of another embodiment. [Figure 6] This is an explanatory diagram of the firing beam of the head unit with the first and second lenses positioned. [Figure 7] This is an explanatory diagram of the firing beam of a head unit with only the first lens positioned. [Figure 8] This is an explanatory diagram of the firing beam of a head unit with a first lens arranged in another embodiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 is a block diagram of an aerosol detection system according to an embodiment of the present invention. The aerosol detection system consists of an aerosol detection device 1 that detects aerosol particles, and a plurality of head units 3 that are connected to the aerosol detection device 1 via laid optical fibers 2 and installed in the space where aerosol detection is to be performed.

[0014] Aerosols are a general term for tiny liquid or solid particles suspended in the air, and include water droplets that make up fog, fine particles of combustion products that make up smoke, and fine particles that make up dust.

[0015] Inside the housing 11 of the aerosol detection device 1, there are a plurality of light transmitting and receiving units 12 (Smoke X Unit) connected via the laid optical fiber 2 for each head unit 3, a processing unit 14 connected to these plurality of light transmitting and receiving units 12 via a集线 device 13 such as a hub to determine the detection of aerosol, and a power supply unit 15 that converts AC power from a commercial power supply into DC power and supplies it to each device including this processing unit 14.

[0016] Also, between the light transmitting and receiving unit 12 and the集线 device 13, and between the集线 device 13 and the processing unit 14, they are connected by a signal line 16 such as a USB cable. The processing unit 14 uses, for example, a general-purpose PC, and internal communication applications, aerosol detection applications, status display applications, waveform display applications, external communication applications, contact applications, life and death monitoring applications, etc. are pre-installed on this PC.

[0017] The processing unit 14 is connected to an alarm unit 4, which is an external device via a serial cable or the like, and performs warning displays such as lamp flashing when aerosol is detected or when the light source output decreases during the light source output monitoring described later, and a display unit 5 that displays these warning contents and the state of the aerosol detection target space on the screen.

[0018] Furthermore, the processing unit 14 is connected to a network N such as a LAN, and a plurality of aerosol detection devices 1 and a central monitoring unit C that centrally monitors the plurality of aerosol detection devices 1 are connected to this network N.

[0019] Figure 2 is a block configuration diagram of the light transmitting and receiving unit 12 and the head unit 3, and the number of the light transmitting and receiving units 12 can be increased or decreased up to a maximum of 20 for one housing 11.

[0020] The light transmitting and receiving unit 12 includes a light source unit 12a that emits laser light from the head unit 3 via the laid optical fiber 2, a light receiving unit 12b that receives the emitted beam B reflected by aerosols S such as smoke particles floating in the aerosol detection target space A via the head unit 3 and the laid optical fiber 2, and a multiplexer / demultiplexer 12e that splits the reflected light from the laid optical fiber 2 into a light transmitting optical fiber 12c and a light receiving optical fiber 12d. The light receiving unit 12b also receives emitted light used for monitoring the output of the light source unit 12a, which will be described later.

[0021] The multiplexer / demultiplexer 12e, which consists of an optical fiber coupler, is a 1x2 coupler formed by fusion splicing and stretching two optical fibers. One end has a laid optical fiber 2, and the other end has a transmitting optical fiber 12c through which the laser light from the light source unit 12a propagates, and a receiving optical fiber 12d through which the reflected light propagates to the light receiving unit 12b. Because the cores of the two optical fibers in the multiplexer / demultiplexer 12e are close together, the laser light propagating through one optical fiber is coupled to the other optical fiber and propagated through it.

[0022] The light source unit 12a employs a laser light source such as a semiconductor laser, i.e., a laser diode (LD), or an LED, which has a wavelength ranging from just before visible light to infrared light, from 300 nm to 1700 nm. Furthermore, laser light with frequencies from 200 Hz to 1 MHz can be appropriately used. The wavelength of the light source is not limited to a single wavelength; multiple wavelengths are also possible.

[0023] An output monitoring unit 17 is positioned between the laid optical fiber 2 and the multiplexer / demultiplexer 12e. This output monitoring unit 17 consists of a pair of optical connectors 17a positioned on both sides and an optical adapter 17b sandwiched between the pair of optical connectors 17a. The ferrules 17c at the ends of the optical connectors 17a are in contact with each other within the optical adapter 17b.

[0024] Furthermore, the light source unit 12a is replaceable. When the light source unit 12a needs to be replaced due to aging or other reasons, the optical fiber section is separated from the connection unit 12f, replaced with a new light source unit 12a, and the optical fiber section continuous with the new light source unit 12a is connected to the connection unit 12f. In this way, it is possible to replace only the light source unit 12a from the light transmitting and receiving unit 12.

[0025] Figure 3 is an explanatory diagram of the output monitoring unit 17 in which a pair of optical connectors 17a are connected to an optical adapter 17b. The tips of the ferrules 17c of the pair of optical connectors 17a abut against each other at the connection surface 17d and are covered by a split sleeve 17e. This split sleeve 17e makes it possible to align the central axes of the ferrules 17c.

[0026] Then, as the tips of the ferrules 17c are pressed together in the direction of the arrows shown in Figure 3, the laser light emitted from the light source unit 12a is not transmitted through because the tip shape is elastically deformed, but is partially reflected and received by the light receiving unit 12b.

[0027] Furthermore, since the amount of reflected light changes depending on the elastically deformed shape of the tip of the ferrule 17c, a predetermined elastic deformation is performed in advance so that the amount of reflected light becomes a predetermined value. In this way, in this embodiment, output monitoring at the light source unit 12a can be performed without providing a special reflective member.

[0028] Figure 4 is a block diagram of the light transmitting / receiving unit and head unit of another embodiment, in which a multiplexer / demultiplexer 12e that connects the laser light from the light source unit 12a and the reflected light from the light receiving unit 12b in a coaxial state is not installed.

[0029] The head unit 3' includes a connection section 31a that propagates laser light from the light source section 12a through the laid optical fiber 2, a ferrule 31b extending from the connection section 31a, a lens section 31c that allows the emitted beam B emitted from the ferrule 31b to pass through, and a connection section 32a, ferrule 32b, and lens section 32c that propagate the reflected light to the light receiving section 12b.

[0030] In head unit 3', the orientation of the lens sections 31c and 32c needs to be adjusted according to the aerosol detection target space A, whereas this adjustment is not necessary in the configurations shown in Figures 2 and 5 where the transmitted and received light are coaxial.

[0031] Furthermore, by separately arranging a multiplexer / demultiplexer, which serves as an output monitoring unit, on the optical path of the light-transmitting optical fiber 12c, and connecting one of the branched ends to the connection unit 12f and the laid optical fiber 2, and arranging a light-receiving unit separate from the light-receiving unit 12b on the other branched end, it is also possible to monitor the deterioration of the light source unit 12a over time. If the branching ratio of the multiplexer / demultiplexer is set to, for example, 99:1, the processing unit 14 will determine whether to replace the light source unit 12a based on the light intensity received by the light-receiving unit as described above.

[0032] Figure 5 is a block diagram of the light transmitting / receiving unit and head unit of another embodiment, in which two head units 31 and 32 can be connected to one light transmitting / receiving unit 12''.

[0033] The light transmitting and receiving unit 12'' includes a light source unit 12a, a pair of head units 31, 32 and a pair of laid optical fibers 2', 2'' which receive the emitted beam B reflected by aerosols S from a fire floating in the aerosol detection target space A, and a first and second light receiving unit 12b', 12b'' which branches the light transmitting optical fiber 12c through which the laser light emitted from the light source unit 12a propagates into first and second branch optical fibers 12g', 12g''. The system includes a multiplexer / demultiplexer 12h, a second multiplexer / demultiplexer 12e' that splits the reflected light from one laid optical fiber 2' into a first branch optical fiber 12g' and a first light-receiving optical fiber 12d' that propagates to the first light-receiving unit 12b', and a third multiplexer / demultiplexer 12e" that splits the reflected light from the other laid optical fiber 2'' into a second branch optical fiber 12h'' and a second light-receiving optical fiber 12d'' that propagates to the second light-receiving unit 12b''.

[0034] The second and third multiplexers 12e' and 12e'' are connected to the laid optical fiber 2 and head units 31 and 32 via the first and second output monitoring units 17' and 17'', respectively. The head units 31 and 32 each have a connecting portion 3a for connecting the ends of the laid optical fiber 2, a ferrule 3b extending from the connecting portion 3a, and a lens portion 3c for passing the emitted beam B emitted from the ferrule 3b.

[0035] Furthermore, for the lens sections 3c of head units 31 and 32, since the transmission and reception of laser light are coaxial, adjustment of the orientation of the lens section 3c is unnecessary. In addition, the connection sections 3a of head units 3, 3', 31, and 32 and the connection sections 12f of the light transmission and reception units 12, 12', and 12'' are all connected to an optical adapter with a pair of optical connectors, similar to the output monitoring unit 17, and the optical connectors can be attached to and detached from the optical adapter as needed.

[0036] Figure 6 is an explanatory diagram of the emitted beam B of the head unit 3, which has a lens section 3c consisting of first and second lenses 3d and 3e. The first lens 3d has a curved surface that curves only in the vertical direction so as to refract the vertical emitted beam B, which spreads out in a fan shape from the ferrule 3b, into parallel light.

[0037] The second lens 3e expands in a fan shape from the ferrule 3b and has a concave surface that further expands the horizontal emission beam B that has passed through the first lens 3d, only in the horizontal direction. Note that the horizontal emission beam B passing through the first lens 3d and the vertical emission beam B passing through the second lens 3e are not bent.

[0038] Figure 7 is an explanatory diagram of the firing beam B of the head unit 3 with a lens section 3c consisting only of the first lens 3d, and is the same configuration as the head unit 3 shown in Figure 6 but with the second lens 3e removed.

[0039] The emission beam B, with the lens arrangement shown in Figures 6 and 7, is narrow in the vertical direction, but is emitted from the head unit 3 towards the aerosol detection target space A in a fan shape in the horizontal direction.

[0040] When a warehouse, a container ship carrying vehicles, and a multi-story parking garage are designated as the aerosol detection target space A, the head unit 3 is installed near the ceiling to emit the emission beam B horizontally, making it possible to detect aerosols of smoke particles from vehicle fires, etc., without obstruction.

[0041] Figure 8 is an explanatory diagram of the emission beam B of a head unit 3 with a first lens arranged in another embodiment, wherein the lens portion 3c, consisting of the first lens 3d', has a curved surface that curves vertically and horizontally so as to refract the vertical and horizontal emission beam B that spreads out in a fan shape from the ferrule 3b into parallel light.

[0042] When a corridor in a hotel or similar building is designated as the aerosol detection target space A, the head unit 3 is installed near the ceiling to emit a beam B horizontally. This allows the beam B to pass through the first lens 3d' and become a straight beam, enabling the detection of aerosols of smoke particles caused by fires, etc.

[0043] Furthermore, the head unit 3 does not require a power supply. After fixing the head unit 3 near the ceiling or elsewhere as described above, the installation of the head unit 3 is completed by connecting the optical connector at the end of the laid optical fiber 2 to the optical adapter at the connection part 3a.

[0044] In this manner, head units 3 are installed in each room of the warehouse, on each floor of the container ship and multi-story parking garage, and on each floor of the hotel, while aerosol detection devices 1 are installed in the control rooms of the warehouse, container ship, multi-story parking garage, and hotel.

[0045] The aerosol detection method in the processing unit 14 detects aerosol S floating in the aerosol detection target space A based on the time difference between the emission of pulsed laser light from the light source unit 12a to the reception of the light by the light receiving unit 12b, for pulsed laser light emitted from the light source unit 12a at predetermined intervals.

[0046] The processing unit 14 may determine that an aerosol S has been detected when the number of detections in a predetermined time exceeds a detection threshold, taking into consideration false detections of the aerosol S by the light receiving unit 12b.

[0047] In the control room, the administrator can constantly monitor the status of the aerosol detection target space A displayed on the display unit 5. When the processing unit 14 detects an aerosol S, the alarm unit 4 will flash a lamp, a warning sound will be emitted, and the detection location will be displayed on the display unit 5.

[0048] Furthermore, the processing unit 14 also monitors the output of the light source unit 12a, and if the output of the reflected light from the output monitoring unit 17, which is input via the light receiving unit 12b, falls below the replacement light intensity threshold, it determines that the light source unit 12a has reached its replacement time and issues a warning to the alarm unit 4 and the display unit 5 prompting replacement.

[0049] The method for determining the replacement of the semiconductor laser in the processing unit 14 based on the reflected light from the output monitoring unit 17 utilizes the fact that the distance from the light source unit 12a to the output monitoring unit 17 is constant.

[0050] A portion of the laser light emitted from the light source unit 12a is reflected at the interface between the tip surfaces of the ferrules 17c of the output monitoring unit 17, and is received by the light receiving unit 12b after a certain period of time.

[0051] For example, if the interface between the tip surfaces of the ferrules 17c of the output monitoring unit 17 is located 1.5 m away from the light source unit 12a via the optical fiber 12c and the multiplexer / demultiplexer 12e, then 10 nS after the laser beam is emitted from the light source unit 12a, the light receiving unit 12b will receive the reflected light reflected from the interface between the tip surfaces of the ferrules 17c.

[0052] The processing unit 14 compares the reflected light intensity received by the light receiving unit 12b 10 nS after the emission of laser light from the light source unit 12a with the replacement light intensity threshold. If the number of times the reflected light intensity is detected to be less than or equal to the replacement light intensity threshold over a predetermined period of time exceeds the detection threshold, the processing unit 14 determines that it is time to replace the semiconductor laser.

[0053] The light receiving unit 12b can also detect the reflected light intensity from the connection part 3a of the head unit 3, and the connection part 3a can be used as a backup output monitoring unit. Considering noise in the reflected light, it is preferable to install the output monitoring unit 17 near the multiplexer / demultiplexer 12e as shown in the figure.

[0054] Furthermore, regarding the first and second output monitoring units 17' and 17'' in the light transmitting / receiving unit 12' shown in Figure 5, the first output monitoring unit 17' is primarily used for replacement determination, and the second output monitoring unit 17'' is used as a backup for replacement determination in the event of a malfunction in the first output monitoring unit 17'.

[0055] Furthermore, the central monitoring unit C, which centrally monitors multiple aerosol detection devices 1 via the network N, receives notifications from the processing unit 14 regarding aerosol detection and replacement of the light source unit 12a, enabling it to quickly arrange for fire trucks and other necessary equipment, as well as the replacement of the light source unit 12a.

[0056] While preferred embodiments of the present invention have been described, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist.

[0057] For optical fibers that propagate laser light, it is preferable to use single-mode optical fibers. By using single-mode optical fibers with a reduced core diameter, transmission loss is reduced, and it becomes possible to emit and receive a directional and stable laser beam, beam B.

[0058] Furthermore, a multimode optical fiber may be used instead of a single-mode one. By using a multimode fiber, the output of the laser light from the light source unit 12a can be increased, making it possible to set the aerosol detection target space A to a greater distance.

[0059] Furthermore, it is possible to configure some parts in single mode and others in multi-mode, meaning that the connection between the head unit 3 and the transmitting / receiving unit 12 can be in single mode, while the inside of the transmitting / receiving unit 12 can be in multi-mode.

[0060] As described above, the aerosol detection system according to the present invention simplifies the replacement of the light source unit 12a and facilitates temperature control of the light source unit 12a by housing multiple light transmitting and receiving units 12, which are unitized with a light source unit 12a and a light receiving unit 12b, in a single housing 11. Only the light source unit 12a can be replaced from the light transmitting and receiving unit 12, and the replacement work can be performed in one location. In addition, by providing an output monitoring unit 17 in the light transmitting and receiving unit 12, it is possible to easily determine whether or not the light source unit 12a has reached the time for replacement. [Explanation of symbols]

[0061] 1. Aerosol detection device 2. Laying optical fibers 3, 3', 31, 32 Head Unit 11 cabinets 12, 12', 12" Transmit / Receiver Unit 12a Light source section 12b, 12b', 12b” light receiving part 12c optical fiber for optical transport 12d, 12d'12d" Optical fiber for light reception 12e, 12e'12e", 12g multiplexer / demultiplexer

Claims

1. An aerosol detection system comprising an aerosol detection device that detects aerosols floating in a space to be detected, and a plurality of head units connected to the aerosol detection device via laid optical fibers and installed in the space to be detected, The housing of the aerosol detection device includes one or more light transmitting and receiving units connected to each head unit via the laid optical fiber, and one processing unit connected to the one or more light transmitting and receiving units for detecting the aerosol. The light transmitting and receiving unit comprises a light source unit that emits laser light, a light receiving unit that receives the emitted light reflected by the aerosol, a multiplexer / demultiplexer that bundles the light transmitting optical fiber from the light source unit and the light receiving optical fiber to the light receiving unit in a coaxial state, and an output monitoring unit installed between the multiplexer / demultiplexer and the laid optical fiber. The output monitoring unit consists of a pair of optical connectors located on both sides and an optical adapter sandwiched between the pair of optical connectors. The aerosol detection system is characterized in that the processing unit determines the replacement of the light source based on the reflected light intensity received by the light receiving unit after a certain period of time, which is obtained when a portion of the laser light emitted from the light source unit is reflected at the interface between the tip surfaces of the ferrules of the pair of optical connectors, and a replacement light intensity threshold.

2. An aerosol detection system comprising an aerosol detection device that detects aerosols floating in a space to be detected, and a plurality of head units connected to the aerosol detection device via laid optical fibers and installed in the space to be detected, The housing of the aerosol detection device includes one or more light transmitting and receiving units connected to each head unit via the laid optical fiber, and one processing unit connected to the one or more light transmitting and receiving units for detecting the aerosol. The light transmitting and receiving unit comprises a light source unit that emits laser light, a pair of first and second light receiving units that receive the emitted light reflected by the aerosol, a first multiplexer / demultiplexer that branches the light transmitting optical fiber through which the laser light emitted from the light source unit propagates into first and second branch optical fibers, a second multiplexer / demultiplexer that branches the reflected light from the first laid optical fiber into the first branch optical fiber and a first light receiving optical fiber that propagates to the first light receiving unit, and a third multiplexer / demultiplexer that branches the reflected light from the second laid optical fiber into the second branch optical fiber and a second light receiving optical fiber that propagates to the second light receiving unit. The first and second output monitoring units are arranged between the second and third multiplexers and the first and second laid optical fibers, respectively. The output monitoring unit consists of a pair of optical connectors located on both sides and an optical adapter sandwiched between the pair of optical connectors. The aerosol detection system is characterized in that the processing unit determines the replacement of the light source based on the reflected light intensity received by the light receiving unit after a certain period of time, which is obtained when a portion of the laser light emitted from the light source unit is reflected at the interface between the tip surfaces of the ferrules of the pair of optical connectors, and a replacement light intensity threshold.

3. The aerosol detection system according to claim 2, characterized in that the processing unit compares the reflected light intensity with the replacement light intensity threshold, and determines that the time for replacing the light source has been reached when the number of detections in which the reflected light intensity in a predetermined time is less than or equal to the replacement light intensity threshold exceeds the detection threshold.

4. The aerosol detection system according to claim 3, characterized in that when the processing unit determines that the light source unit needs to be replaced, it issues a warning to the alarm unit prompting replacement.

5. The aerosol detection system according to claim 1 or 2, characterized in that the optical fiber is single-mode.

Images