Optical node and inundation detection system

Abstract

An optical node N1 comprises a first housing 61 and a second housing 62 housed in the first housing 61. The first housing 61 and the second housing 62 have waterproofness. Active devices 30, 40, 50 of the optical node N1 are disposed in the second housing 62, and a passive device 50 of the optical node N1 is disposed inside the first housing 61 and outside the second housing 62.

Description

Optical Node and Water Flooding Detection System

[0001] The present disclosure relates to optical nodes and water intrusion detection systems.

[0002] In an optical fiber network, for example, an access network that connects communication equipment installed in a communication building with a user's communication terminal, when a communication route is opened or maintained, switching from one optical fiber core to another is performed at a predetermined frequency in order to build a new communication route or change to a different communication route.

[0003] Although such switching work is usually performed manually by an operator on-site, a technology for remotely switching optical fiber cores has been proposed (Non-Patent Document 1).A technology for optically feeding power to multiple optical nodes has also been proposed (Non-Patent Document 2).

[0004] "Remote Optical Path Switching Nodes Operating in Multistage Loop Optical Access Networks", 2021 IEICE Society Conference, BK-2-3, 2021 "A Study on Serial Connection Methods for Remote Optical Path Switching Nodes", 2022 IEICE General Conference, B-13-28, 2022 "Development of Underground Optical Closure to Improve Assembly and Water-tightness", International Wire & Cable Symposium, Proceedings of the 58th IWCS / IICIT, p101-104 "Improvement of Water Detection Modules", IEICE Technical Report OFT2009-60

[0005] Optical nodes are expected to be installed outdoors, such as in underground manholes. When optical nodes are installed outdoors, rainwater, groundwater, etc. may enter the optical node, and various devices housed in the optical node may become wet and malfunction.

[0006] Non-Patent Document 3 describes a technology for improving the waterproofing of optical closures placed underground. Also, Non-Patent Document 4 proposes a technology for detecting water intrusion into optical closures. However, even with the underground optical closure of Non-Patent Document 3, water may enter a manhole and flow into the underground optical closure through an opening / closing part or a through-hole, causing flooding.

[0007] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a technology that prevents components of a device installed outdoors from breaking down due to exposure to water.

[0008] In order to achieve the above object, one aspect of the present disclosure is an optical node comprising a first housing and a second housing stored within the first housing, the first housing and the second housing being waterproof, an active device of the optical node being disposed within the second housing, and a passive device of the optical node being disposed inside the first housing and outside the second housing.

[0009] One aspect of the present disclosure is a water-immersion detection system comprising an optical node and an optical pulse tester, wherein the optical node comprises a first housing, a second housing stored within the first housing, and a water-immersion detection module attached to an optical fiber located inside the first housing and outside the second housing, the water-immersion detection module causing bending loss to the optical fiber when submerged in water, the first housing and the second housing being waterproof, an active device of the optical node being located inside the second housing, and a passive device of the optical node being located inside the first housing and outside the second housing, the optical pulse tester emitting an optical pulse into the optical fiber and detecting bending of the optical fiber using the reflected light of the optical pulse, thereby detecting water immersion of the optical node.

[0010] According to the present disclosure, it is possible to provide a technique for preventing breakdowns caused by components of a device installed outdoors becoming wet with water.

[0011] FIG. 1 is a diagram showing an example of a network configuration of an optical fiber network according to an embodiment. FIG. 2 is a diagram showing an example of a configuration of an off-site node. FIG. 3 is a diagram showing an example of a configuration of an on-site node and an off-site node. FIG. 4 is a diagram showing a schematic diagram of an off-site node according to a second embodiment. FIG. 5 is a diagram showing an example of a configuration of an optical node system according to a third embodiment. FIG. 6 is a diagram showing a schematic diagram of a water intrusion detection module. FIG. 7 is a diagram showing an example of a configuration of an optical node system according to a third embodiment. FIG. 8 is a diagram showing an example of a configuration of an optical node system according to a fourth embodiment. FIG. 9 is a flowchart showing the control of a controller. FIG. 10 is a diagram showing an example of a hardware configuration.

[0012]

[0023] Embodiments of the present disclosure will be described with reference to the accompanying drawings. The embodiments described below are examples of the present disclosure, and the present disclosure is not limited to the following embodiments. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0013] <First embodiment> Fig. 1 is a diagram showing an example of a network configuration of an optical fiber network. The illustrated optical fiber network is a multistage loop type optical fiber network (optical access network) including multiple loop networks. The optical fiber network includes an upper loop network LP0 that passes through a communication building or the like, and at least one lower loop network LP1 to LP3 that is connected to the upper loop network LP0. In the example shown in Fig. 1, three lower loop networks LP1 to LP3 are shown, but the number of lower loop networks is not limited to this.

[0014] Node N0 is located in the upper loop network LP0. Nodes N1 to N3 are located at the connection points between the upper loop network LP0 and each of the lower loop networks LP1 to LP3. The optical cross-connects of nodes N1 to N3 allow the two loops to share the same optical fiber core wire, making it possible to switch the optical fiber core wire. This makes it possible to reduce the need for additional optical cable installation work due to fluctuations in demand. Hereinafter, "optical fiber core wire" will also be referred to as "optical fiber."

[0015] Node N0 is an on-site node (optical node) installed in an environment where commercial power is available, for example, in a communication building. Nodes N1 to N3 are off-site nodes (optical nodes) installed outdoors, for example. In this embodiment, the direction from the off-site nodes N1 to N3 to the on-site node N0 is referred to as the "upstream direction," and the direction from the on-site node N0 to the off-site nodes N1 to N3 is referred to as the "downstream direction."

[0016] In an optical fiber network comprising a plurality of nodes N0 to N3, a single laser installed in the on-site node N0 supplies power to the off-site nodes N1 to N3 via optical fiber power feeding and controls the switching of the optical fibers of the off-site nodes N1 to N3. The off-site nodes N1 to N3 mutually switch the optical fibers for communication between them on an optical fiber-by-optical-line basis under remote control from the off-site node N0.

[0017] The on-site node N0 coordinates the operation of the off-site nodes N1 to N3 installed outdoors. The on-site node N0 outputs power supply light and communication light to the off-site nodes N1 to N3 via optical fibers. The on-site node N0 performs signal processing to superimpose a control signal on the power supply light output from the light source. The on-site node N0 can remotely control the off-site nodes N1 to N3.

[0018] 2 shows a schematic configuration of the off-site node N1. The configurations of the off-site nodes N2 and N3 are similar to that of the off-site node N1, so a description thereof will be omitted. The off-site node N1 comprises a remote control unit 20, an optical cross-connect 30, and an optical port monitoring unit 40.

[0019] The remote control unit 20 photoelectrically converts the power supply light and stores it in a power storage unit, and uses this stored power to drive the optical cross connect 30 and the optical port monitoring unit 40. The remote control unit 20 also controls the optical cross connect 30 using a control signal superimposed on the power supply light to switch optical fibers. The remote control unit 20 also controls the optical port monitoring unit 40 to detect transmitted light and measure the power of the transmitted light.

[0020] The optical cross connect 30 switches optical fibers from a plurality of routes under the control of the remote control unit 20. The optical port monitor 40 extracts a portion of the optical signal passing through each port of the off-site node N1 and measures the optical power.

[0021] In this way, the off-site node N1 can operate using power supplied by the optical power supply from the on-site node N0 without using a commercial power source. In other words, the off-site node N1 can be installed in a wide range of outdoor locations where there is no commercial power source.

[0022] 3 shows an example of the configuration of an optical node system including an on-site node N0 and an off-site node N1. The on-site node N0 shown in the figure is installed in an environment where power is available (for example, in a communications building) and provides optical fiber power feeding. Specifically, the on-site node N0 outputs light for power feeding to the off-site node N1 via an optical fiber 9. That is, the on-site node N0 switches the optical switch 21 to direct downstream light output from the optical fiber 9 to the off-site node to be powered, thereby supplying power to the off-site node.

[0023] The illustrated local node N0 includes a light source 11 that outputs light, a modulator 12, an optical circulator 13, a light receiver 14, and a controller 15. Note that light will also be referred to as an optical signal in the following description.

[0024] The optical circulator 13 branches an optical signal in the downstream direction (hereinafter referred to as the "downstream signal") and an optical signal in the upstream direction (hereinafter referred to as the "upstream signal"). The downstream signal and the upstream signal are branched through the optical circulator 13, and a single optical fiber 9 can connect the on-site node N0 and the off-site node N1.

[0025] The light source 11 outputs light to the off-site node N1 via the optical fiber 9. The light source 11 is, for example, a laser diode, and emits laser light. The light emitted from the light source 11 is input to the optical fiber 9 via a modulator 12 and an optical circulator 13. In this embodiment, the power supply light source 11 is used to transmit and receive downstream signals (control signals) and upstream signals.

[0026] The modulator 12 (intensity modulator) modulates the light output from the light source 11 under the control of the controller 15 to generate a downstream signal, which is then superimposed on the power supply light and output to the off-site node N1. In the example shown in the figure, an external modulation method is used in which the light source 11 and the modulator 12 are separate, but a direct modulation method may also be used. For example, the light source 11 may be configured as an internally modulated laser with a modulation function.

[0027] The optical receiver (photoelectric converter) 14 receives the upstream signal output from the off-site node N1 via the optical fiber 9, converts it into an electrical signal, and outputs it to the controller 15. The optical receiver 14 uses a light-receiving element such as a photodiode.

[0028] The controller 15 controls the on-site node N0 and the off-site node N1. For example, the controller 15 controls the optical power supply to the off-site node N1. The controller 15 also sends a modulated signal to the modulator 12 and superimposes a control signal (downstream signal) to the off-site node N1 onto the power supply light output by the light source 11. The control signal may be, for example, an instruction to switch the power supply destination, an instruction to drive the optical cross-connect 30 and the port monitor 40, etc. The controller 15 also receives an upstream signal output from the optical receiver 14 and may transmit information included in the upstream signal to another system (not shown).

[0029] The off-site node N1 is connected to the on-site node N0 via an optical fiber 9 and is a device capable of storing power through optical power feeding. As described above, the off-site node N1 includes the remote control unit 20, the optical cross-connect 30, and the port monitoring unit 40.

[0030] The off-site node N1 of this embodiment is housed in outdoor housings 61, 62 that protect the off-site node N1 installed outdoors. The illustrated off-site node N1 includes a first housing 61 and a second housing 62 housed within the first housing 61, and the first housing 61 and the second housing 62 are waterproof. Active devices (active components, active elements) 20, 30, and 40 of the off-site node N1 are disposed within the second housing 62, and a passive device (passive component, passive element) 50 of the optical node N1 is disposed inside the first housing 61 and outside the second housing 62. The first housing 61 and the second housing 62 have through-holes 611, 621 for connecting an optical fiber 9.

[0031] There are no limitations on the shapes of the first housing 61 and the second housing 62. In other words, as long as the second housing 62 fits inside the first housing 61, the first housing 61 and the second housing 62 may have any shape and any size.

[0032] 3 shows an example of a two-tiered outdoor enclosure in which a second enclosure 62 is housed within a first enclosure 61, but this is not limiting. For example, the outdoor enclosure may include three or more enclosures of similar shape but different sizes, with the largest first enclosure housing the other enclosures in turn (a so-called nested structure). That is, the off-site node N1 may include at least one third enclosure (not shown) housed within the first enclosure 61 and housing the second enclosure 62.

[0033] Each of the housings 61, 62 has a waterproof and openable structure. For example, each of the housings 61, 62 may include a first case and a second case, and waterproofness may be ensured by sealing the peripheries of the first case and the second case with a sealing member such as a packing or a gasket.

[0034] Each of the housings 61, 62 has through-holes 611, 621 with an outer diameter large enough to pass an optical fiber 9 (optical fiber cable) through to the outside, and has a structure that provides waterproofing between the through-holes and the optical fiber 9. For example, waterproofing (water-stopping) may be ensured by embedding a sealing member such as a packing or a gasket between the through-holes 611, 621 and the optical fiber 9. It is preferable to pass the optical fiber 9 through the through-holes in advance during the manufacture of the off-station node N1, rather than passing the optical fiber 9 through the through-holes after the off-station node N1 is installed on-site. It is preferable to provide one through-hole 611, 621 for each of the housings 61, 62.

[0035] In the off-site node N1, active devices are placed (housed) in the innermost second enclosure 62. In the illustrated example, the active devices are the remote control unit 20, the optical cross connect 30, and the optical port monitoring unit 40.

[0036] A passive device 50 of the optical node N1 is placed (housed) inside the outermost first housing 61 and outside the second housing 62. The passive device 50 is, for example, a device that does not immediately fail even if submerged in water, such as an excess length of optical fiber 9. The excess length of optical fiber 9 housed outside the second housing 62 includes, for example, an excess length of fusion-spliced ​​optical fiber 9.

[0037] In addition, a space may be provided in the innermost second housing 62 to store the excess length of the optical fiber 9 connected using an optical connection part such as an optical connector that generally does not have waterproof properties.

[0038] In this embodiment, the active devices 20, 30, 40, which are easily damaged by flooding, are arranged in the innermost second housing 62 of the off-site node N1. As a result, in this embodiment, even if the outermost first housing 61 is damaged and the inside of the first housing 61 is flooded, the active devices will not be flooded unless the water reaches the inside of the second housing 62, and failures of the off-site node N1 due to flooding can be reduced.

[0039] Furthermore, if the off-site node N1 is stored in the first housing 61 and has at least one third housing (not shown) that stores the second housing 62, even if the first housing 61 and the third housing are damaged, the active device will not be flooded unless the water reaches the inside of the second housing 62, thereby further improving waterproofing.

[0040] The remote control unit 20 shown in Fig. 3 will now be described. The remote control unit 20 includes an optical switch 21, optical couplers 22A and 22B, an opto-electric conversion unit 23, an optical circulator 24, a light receiving unit 27, an upstream communication unit 28, a microcomputer 29, power storage units 25A and 25B, and boost circuits 26A and 26B.

[0041] The optical coupler 22A (first optical coupler) branches the light output from the local node N0 into two. The optical coupler 22A is a multiplexer / demultiplexer that can multiplex / demultiplex downstream light and upstream light. The optical coupler 22A is a branching ratio coupler that branches a larger portion of the optical power of the downstream light output from the local node N0 to the optical switch 21 with a branching ratio of, for example, 90:10. The light branched by the optical coupler 22A and having the smaller optical power is guided to the optical circulator 24.

[0042] The optical switch 21 switches the light output from the on-site node N0 and branched by the optical coupler 22A to its own node or another downstream off-site node N2. In other words, the optical switch 21 can switch the optical power supply direction used for power storage between its own node and another downstream off-site node. The optical switch 21 can be, for example, a 1×2 optical switch. This allows one light source 11 in the on-site node N0 to supply power to multiple off-site nodes N1 and drive the multiple off-site nodes N1.

[0043] Photoelectric conversion unit 23 converts the light output from optical switch 21 into electricity and stores the electricity in storage units 25A and 25B. Photoelectric conversion unit 23 uses a photoelectric conversion element capable of receiving the wavelength of the laser light emitted by light source 11. The photoelectric conversion element can be an easily available element suitable for the long wavelength band of 1300 nm to 1600 nm used for communications, such as an element made of indium gallium arsenide, with an open circuit voltage of 5 V or less and a conversion efficiency of approximately 30%. The wavelength of the light emitted by light source 11 is set to a wavelength that corresponds to the photoelectric conversion element of photoelectric conversion unit 23 used.

[0044] The optical circulator 24 separates the other light branched from the optical coupler 22A into a downstream signal and an upstream signal.

[0045] The optical coupler 22B (second optical coupler) branches the light separated by the optical circulator 24. The light branched by the optical coupler 22B is guided to a light receiving unit 27 that receives the light as a downstream signal and an upstream communication unit 28 that generates an upstream signal. The optical coupler 22B is a branching ratio coupler that branches the light at a branching ratio of, for example, 50:50.

[0046] The optical receiver 27 receives one of the lights branched from the optical coupler 22B as a downstream signal. A light receiving element such as a photodiode is used for the optical receiver 27. The downstream signal includes a control signal transmitted by the local node N0.

[0047] The upstream communication unit 28 modulates the other light branched by the optical coupler 22B to generate modulated light and outputs the modulated light to the local station node N0. Specifically, the upstream communication unit 28 includes a reflective optical switch (not shown) that performs modulation synchronized with a signal from a microcomputer 29, which will be described later. The generated modulated light is output to the local station node N0 via the optical fiber 9 as an upstream signal to the local station node N0. The upstream communication unit 28 preferably operates at a low voltage and with low power consumption of several μW or less; for example, an electrostatically driven MEMS optical switch can be used.

[0048] The off-station node N1 of this embodiment includes multiple power storage units 25A, 25B depending on the application. Here, the off-station node N1 is described as including two power storage units 25A, 25B as an example, but the number of power storage units may be one or three or more. For example, electric double layer capacitors or the like may be used for the power storage units 25A, 25B.

[0049] The power storage unit 25A stores the electrical energy converted by the photoelectric conversion unit 23. The electrical energy stored in the power storage unit 25A serves as a power source for the remote control unit 20, including the microcomputer 29, the optical switch 21, and the upstream communication unit 28. The power storage unit 25B stores the electrical energy converted by the photoelectric conversion unit 23. The power storage unit 25B serves as a power source for the optical cross connect 30 and the port monitoring unit 40.

[0050] It should be noted that the voltage supplied to each of the active devices 20, 30, 40 can be adjusted appropriately by boost circuits 26A, 26B (DC / DC converters, etc.).

[0051] The microcontroller 29 (hereinafter referred to as "microcomputer") controls active devices such as the optical switch 21, the upstream communication unit 28, the optical cross-connect 30, and the port monitoring unit 40. The microcomputer 29 may be, for example, a microprocessor.

[0052] The microcomputer 29 mainly has the following functions.

[0053] (1) Downstream signal analysis function The microcomputer 29 analyzes the downstream signal received by the optical receiver 27. The light output from the light source 11 of the local node N0 is intensity-modulated as output laser light under the control of the controller 15, and becomes a downstream signal such as a serial communication signal. The downstream signal includes various control signals, such as a switching instruction for the optical switch 21 to switch the power supply destination, and an instruction to drive the optical cross-connect 30 and the port monitor 40.

[0054] (2) Upstream Signal Generation Function The microcomputer 29, in cooperation with the downstream signal analysis function, generates an upstream signal by modulating the optical switch provided in the upstream communication unit 28.

[0055] (3) Operation Control Function In cooperation with the downstream signal analysis function, the microcomputer 29 switches the optical switch 21 in accordance with a control signal from the local node N0, and also drives the optical cross-connect 30 and the port monitoring unit 40. The microcomputer 29 may measure the voltage of the power storage units 25A and 25B using an AD converter (not shown) or the like provided in the microcomputer 29, generate an upstream signal including the measured voltage using the upstream communication unit 28, and transmit the upstream signal to the local node N0.

[0056] The components of the off-site node N1 are connected via power lines and / or signal lines.

[0057] In FIG. 3, multiple off-site nodes N1 and N2 are connected in series to on-site node N0 via optical fiber 9, but the number of off-site nodes N1 connected to on-site node N0 may be three or more.

[0058] Second Embodiment FIG. 4 is a diagram schematically illustrating an off-site node N1 according to a second embodiment.

[0059] The off-station node N1 of this embodiment is the off-station node N1 of the first embodiment (see FIG. 3) equipped with at least one water sensor, and is otherwise similar to the off-station node N1 of the first embodiment.

[0060] The off-site node N1 shown in the figure accommodates a remote control unit 10, an optical cross connect 30, and an optical port monitoring unit 40 as active devices in a second housing 62. The second housing 62 may also accommodate an excess length 51 of optical fiber 9 connected using an optical connection unit that generally does not have waterproof properties, such as an optical connector. Inside the first housing 61, but outside the second housing 62, a passive device 50 is accommodated, for example, an excess length 50 of fusion-spliced ​​optical fiber 9.

[0061] In this embodiment, the off-site node N1 includes at least one water sensor 71, 72 located inside the first housing 61 and outside the second housing 62. The water sensors 71, 72 detect water (moisture) entering the first housing 61 due to flooding, water leakage, or the like. The water sensors 71, 72 are capable of communicating with an external device (e.g., the on-site node N0) via wired or wireless communication. When the water sensors 71, 72 detect water, they transmit a detection signal to the external device. This allows the external device to detect that the off-site node N1 is flooded. By performing work such as draining water accumulated in the off-site node N1 when the external device detects flooding, it is expected that malfunctions of active devices housed in the second housing 62 due to flooding can be prevented.

[0062] If power is required to operate the water sensors 71 and 72, commercially available batteries may be used, or the power stored in the power storage units 25A and 25B stored in the remote control unit 20 by optical power supply may be used.

[0063] The water sensors 71, 72 are preferably installed in locations where water is likely to enter from the outside. One example of a location where water can enter is the through-hole 611 through which the optical fiber 9 is inserted into the first housing 61. Therefore, the water sensor 71 may be installed on the inner wall surface of the first housing 61, below the through-hole 611. This allows for early detection of water (leakage) that has entered through the through-hole 611. The water sensor 72 may also be installed on the bottom surface of the first housing 61. This allows for detection of water entering the first housing 61.

[0064] While FIG. 4 illustrates an example of installing two water sensors 71 and 72, the number of water sensors may be one or more. For example, the off-site node N1 may include multiple water sensors located inside the first housing 61 and outside the second housing 62, and the multiple water sensors may be installed at different heights from the bottom of the first housing 61. Specifically, by installing multiple water sensors at different heights on the inner wall of the first housing 61, the amount of water accumulating in the vertical direction of the first housing 61 (flooding height) can be estimated from the water sensors. For example, when each water sensor detects water, it transmits a detection signal including its own identification number to an external device. The external device can estimate the water level accumulated inside the first housing 61 by previously storing the identification number of each water sensor and the installation position (height from the floor) of the water sensor.

[0065] <Modification of Second Embodiment> As a modification of the second embodiment, at least one humidity sensor may be used instead of the water sensor to detect water intrusion inside the first housing 61. The humidity sensor is installed inside the first housing 61 but outside the second housing 62, and measures the humidity inside the first housing 61. Like the water sensor, the humidity sensor can communicate with an external device (e.g., the in-house node N0) via wire or wirelessly, and transmits a detection signal to the external device when it detects humidity above a predetermined value. If power is required to drive the humidity sensor, a commercially available battery may be used, or the power stored in the power storage units 25A and 25B may be used.

[0066] When the humidity sensor detects humidity equal to or higher than a predetermined value, it transmits a detection signal to the external device. This allows the external device to detect that the inside of the off-site node N1 is flooded. Each of the off-site nodes N1, N2, and N3 may also be equipped with a humidity sensor, and the humidity sensor may include the measured humidity and identification information of the off-site node in the detection signal. When the external device receives detection signals from multiple off-site nodes, it may determine the order of maintenance of the off-site nodes based on the humidity included in the detection signals and display this on an output device such as a display. For example, the external device may determine the order of maintenance so that the off-site nodes with the highest humidity are maintained first.

[0067] The off-site node N1 may include at least one of a water sensor and a humidity sensor that is disposed inside the first housing 61 and outside the second housing.

[0068] <Third embodiment> Fig. 5 is a diagram showing the configuration of an optical node system according to a third embodiment. The optical node system shown in Fig. 5 differs from the optical node system shown in Fig. 3 in that it includes an optical coupler 81, an optical time domain reflectometer 82 (OTDR), and a water submersion detection module 83, but is otherwise similar to the optical node system shown in Fig. 3.

[0069] In this embodiment, water ingress within the first housing 61 is detected using a water ingress detection module 83 and a pulse tester 82. That is, the water ingress detection system in this embodiment includes an off-station node N1 and an optical pulse tester 82. The off-station node N1 includes a first housing 61, a second housing 62 housed within the first housing 61, and a water ingress detection module 83 attached to an optical fiber 9 located inside the first housing 61 but outside the second housing 62, and which applies bending loss to the optical fiber 9 when submerged in water. The first housing 61 and the second housing 62 are waterproof, and the active devices 20, 30, and 40 of the off-station node N1 are located within the second housing 62, and the passive device 50 of the off-station node N1 is located within the first housing 61 but outside the second housing 62.

[0070] 6 is a schematic diagram of the water ingress detection module 83. The illustrated water ingress detection module 83 includes an expansion agent 831 and a bending portion 832. The water ingress detection module 83 is configured to sandwich the optical fiber 9. When the first housing 61 is flooded with water, the expansion agent 831 in the water ingress detection module 83 reacts to the water and expands, causing the bending portion 832 to bend the optical fiber 9 (cored optical fiber), resulting in optical loss. In other words, when water is ingressed, the water ingress detection module 83 applies lateral pressure to the sandwiched optical fiber 9, bending the optical fiber 9 (Non-Patent Document 4).

[0071] 5 shows a series connection of multiple off-site nodes N1, N2, ... connected in series to the power supply and control optical fiber 9. In this case, the water ingress detection module 83 is preferably installed in the first position 84A, which is upstream of the optical switch 21 and the optical coupler 22A. Water ingress detection is possible even when the water ingress detection module 83 is installed in the second position 84B, which is downstream of the optical switch 21. However, if the optical switch 21 becomes inoperative for some reason while facing the photoelectric conversion unit 23, water ingress in the first housing 61 cannot be detected if the water ingress detection module 83 is installed in the second position 84B. In contrast, when the water ingress detection module 83 is installed in the first position 84A, water ingress can always be detected using the water ingress detection module 83, regardless of the orientation of the optical switch 21.

[0072] Furthermore, it is preferable to attach the water ingress detection module 83 to the optical fiber 9 (optical fiber core) for power supply and control from the off-site node N1. By sharing the optical fiber for power supply and control and the optical fiber for water ingress detection, it is possible to reduce the number of optical fiber cores used for purposes other than communication among the optical fibers drawn into the off-site node N1. It is desirable to use as many optical fibers as possible for their intended purpose, communication, when installing optical fibers outdoors. Since using optical fibers for power supply and control and water ingress detection is not their intended purpose, it is possible to reduce the number of optical fibers used for purposes other than their intended purpose.

[0073] The optical pulse tester 82 emits an optical pulse into the optical fiber 9 and detects bending of the optical fiber 9 using the reflected light of the optical pulse (for example, the backscattered light level), thereby detecting water damage at the off-site node N1.

[0074] The optical pulse tester 82 is connected to the optical fiber 9 via an optical coupler 81. In this example, the optical coupler 81 is inserted into the power supply / control optical fiber 9 near the in-station node N0, and the optical pulse tester 82 is connected to the optical coupler 81. In this way, a pulse test can be performed on the power supply / control optical fiber 9. That is, the optical pulse tester 82 periodically measures the optical fiber 9 to detect any submerged off-station node N1.

[0075] In this embodiment, if water flooding occurs inside the first housing 61 of the off-site node N1, the water flooding detection module 83 expands, bending the optical fiber 9, and the bending is detected by a pulse test using the optical pulse tester 82, making it possible to detect water flooding inside the first housing 61 of the off-site node N1.

[0076] If it is desired to check whether or not there is flooding at multiple off-site nodes, the optical switch 21 can be switched sequentially and a pulse test performed by the pulse tester 82 can be performed to detect whether or not there is flooding at each off-site node.

[0077] <Fourth Embodiment> Fig. 7 is a diagram showing the configuration of an optical node system according to a fourth embodiment. The optical node system shown in Fig. 7 differs from the optical node system shown in Fig. 5 in that it includes wavelength blocking filters 85A and 85B, but is otherwise similar to the optical node system shown in Fig. 5. In this embodiment, water intrusion in the first housing 61 is detected using a water intrusion detection module 83, an optical pulse tester 82, and wavelength blocking filters 85A and 85B. That is, the water intrusion detection system according to this embodiment includes an off-site node N1, an optical pulse tester 82, and wavelength blocking filters 85A and 85B. In this embodiment as well, the water intrusion detection module 83 is attached to an optical fiber for power supply and control.

[0078] In the third embodiment, when a control signal is being transmitted and received from the on-site node N0 to the off-site node N1 through the power supply and control optical fiber, if a pulse test is performed by the pulse tester 82, the control signal light and the optical pulse may overlap, making it impossible to transmit and receive the control signal.

[0079] For this reason, in this embodiment, different wavelengths are used for the power supply laser of the light source 11 of the local node N0 and the optical pulse (test light) of the optical pulse tester 82. For example, the wavelength of the power supply laser may be 1490 nm, and the wavelength of the optical pulse tester 82 may be 1650 nm.

[0080] 7, the off-site node N1 of this embodiment includes a wavelength blocking filter 85A arranged before the optical coupler 81 and a wavelength blocking filter 85B arranged before the optical receiver 27. The wavelength blocking filters 85A and 85B block only the wavelength band of the optical pulse from the optical pulse tester 82.

[0081] In this embodiment, the control signal is superimposed on the power supply light and transmitted through a single optical fiber for power supply and control, but different optical fibers may be used for power supply and control. In this case, by attaching a water immersion detection module 83 to the control optical fiber, it is possible to avoid a situation in which the control signal light and the optical pulse are superimposed, preventing the control signal from being transmitted or received.

[0082] In this manner, in the water flood detection system of this embodiment, the water flood detection module 83 is attached to an optical fiber that transmits a control signal to the off-site node N1, and the optical pulse tester 82 emits an optical pulse into the optical fiber via the optical coupler 81, and the wavelength of the light of the control signal is different from the wavelength of the optical pulse.The system is equipped with a wavelength blocking filter 85B (first wavelength blocking filter) that is placed in front of the light receiving unit 27 of the active device and blocks the wavelength of the optical pulse, and a wavelength blocking filter 85A (second wavelength blocking filter) that is placed in front of the optical coupler 81 and blocks the wavelength of the optical pulse.

[0083] As a result, in this embodiment, the optical pulses from the pulse tester 82 are blocked by the wavelength blocking filter 85B and do not reach the optical receiver 27, thereby preventing them from affecting the transmission and reception of control signals between the in-station node N0 and the off-station node N1. Also, the reflected light from the pulse tester 82 is blocked by the wavelength blocking filter 85A and does not reach the optical receiver 14, preventing them from affecting the transmission and reception of upstream signals between the in-station node N0 and the off-station node N1. This allows the pulse tester 82 to perform testing regardless of whether control signals and upstream signals are being transmitted or received.

[0084] If the off-site node N1 does not transmit an upstream signal, the wavelength blocking filter 85A may be omitted.

[0085] When the pulse tester 82 is in use, the test light from the pulse tester 82 can also be converted into light that can be received by the photoelectric conversion unit 23, so that the test light can also contribute to the power supply as power supply light.

[0086] Fifth Embodiment Fig. 8 is a diagram showing the configuration of an optical node system according to a fifth embodiment. The optical node system shown in Fig. 8 differs from the optical node system shown in Fig. 5 in that the controller 15 of the on-site node N0 controls the operation of the optical pulse tester 82, but is otherwise similar to that shown in Fig. 5. In this embodiment, water ingress within the first housing 61 is detected using a water ingress detection module 83, an optical pulse tester 82, and a controller 15. That is, the water ingress detection system in this embodiment includes an off-site node N1, an optical pulse tester 82, and a controller 15. In this embodiment as well, the water ingress detection module 83 is attached to an optical fiber for power supply and control. That is, the water ingress detection module 83 is attached to an optical fiber that transmits a control signal to the off-site node N1.

[0087] In the fourth embodiment, the use of wavelength blocking filters 85A and 85B has the disadvantage that the power of the optical power supply that can be received at the off-site node N1 is reduced, and the loss due to the blocking filters is added to the power budget for transmitting and receiving control signals, thereby reducing the distance over which control communication is possible.

[0088] 8, in this embodiment, a pulse tester 82 is connected to the controller 15 of the on-site node N0, and the controller 15 controls the timing of the test by the pulse tester 82. Specifically, the controller 15 drives the pulse tester 82 when no control signals are being transmitted or received between the on-site node N0 and the off-site node N1.

[0089] 9 shows a flowchart of the control process of the controller 15. For example, the controller 15 periodically drives the pulse tester 82 to perform a test. At the timing of the periodic test, the controller 15 checks whether a control signal (downstream signal) from the off-station node N1 to the off-station node N1 or an upstream signal from the off-station node N1 to the off-station node N1 is being transmitted or received (S11). If transmission or reception is being performed (S11: YES), the controller 15 waits for a certain period of time (e.g., several tens of seconds to several minutes) (S12) and returns to S11.

[0090] If no transmission or reception is taking place (S11: NO), the controller 15 transmits a test execution instruction to the pulse tester 82, causing the pulse tester 82 to execute the test (S12). The pulse tester 82 executes the test in accordance with the instruction from the controller 15. The controller 15 may also be configured not to transmit or receive a control signal from the on-site node N1 to the off-site node N1 while the pulse tester 82 is executing the test.

[0091] In this way, in the water flood detection system of this embodiment, the water flood detection module 83 is attached to an optical fiber that transmits a control signal to the off-site node N1, and is equipped with a controller 15 that drives the optical pulse tester 82 when no control signal is being sent or received.

[0092] As a result, in this embodiment, the overlapping of the timing of the transmission and reception of the test light from the pulse tester 82 and the timing of the transmission and reception of the control signal can be avoided without being affected by the wavelength blocking filters 85A and 85B, which are used in the fourth embodiment, causing a reduction in the power of the power supply light.

[0093] The off-site node N1 of the embodiment described above comprises a first housing 61 and a second housing 62 stored in the first housing 61, the first housing 61 and the second housing 62 being waterproof, the active devices 30, 40, 50 of the optical node N1 being arranged in the second housing 62, the passive device 50 of the optical node N1 being arranged inside the first housing 61 and outside the second housing 62, and the first housing 61 and the second housing 62 having through-holes for connecting optical fibers 9.

[0094] As a result, in this embodiment, it is possible to prevent the active devices of the off-site node N1, which is installed outdoors, from breaking down due to exposure to water.

[0095] The controller 15 described above can be, for example, a general-purpose computer system as shown in Fig. 10. The computer system shown in the figure includes a CPU (Central Processing Unit, processor) 901, a memory 902, a storage 903 (HDD: Hard Disk Drive, SSD: Solid State Drive), a communication device 904, an input device 905, and an output device 906. The memory 902 and the storage 903 are storage devices. In this computer system, the CPU 901 executes a predetermined program loaded on the memory 902, thereby realizing the functions of the controller 15.

[0096] The controller 15 may be implemented in one computer or in multiple computers. The controller 15 may also be a virtual machine implemented in a computer. The controller 15 program may be stored in a computer-readable recording medium such as a HDD, SSD, USB (Universal Serial Bus) memory, CD (Compact Disc), or DVD (Digital Versatile Disc), or may be distributed via a network. The computer-readable recording medium may be, for example, a non-transitory recording medium.

[0097] The present disclosure is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist thereof. For example, while the multiple housings 61 and 62 in the above-described embodiment are housings for accommodating off-site nodes, the present disclosure is not limited thereto and may be outdoor housings for preventing water from entering devices installed outdoors. That is, the present disclosure may provide an outdoor housing for preventing water from entering devices installed outdoors, the outdoor housing including multiple housings of different sizes, the multiple housings being waterproof, a first housing being the largest of the multiple housings, the other multiple housings being sequentially stored within the first housing, an active device of the device being located within the second housing stored within the innermost of the multiple housings, and a passive device of the device being located within the first housing and outside the second housing.

[0098] N0: In-station node N1 to N3: Off-station nodes (optical nodes) 11: Light source 12: Modulator 13: Optical circulator 14: Optical receiver 15: Controller 20: Remote control unit 21: Optical switch 22A, 22B: Optical coupler 23: Photoelectric conversion unit 24: Optical circulator 25A, 25B: Power storage unit 26A, 26B: Boost circuit 27: Optical receiver unit 28: Upstream communication unit 29: Microcomputer 30: Optical cross-connect 40: Optical port monitoring unit 50, 51: Excess optical fiber length 61: First housing 62: Second housing 71, 72: Water sensor 82: Pulse tester 83: Water intrusion detection module 85A, 85B: Wavelength blocking filter

Claims

1. An optical node comprising a first housing and a second housing housed within the first housing, the first housing and the second housing being waterproof, an active device of the optical node being disposed within the second housing, and a passive device of the optical node being disposed inside the first housing and outside the second housing.

2. The optical node according to claim 1, wherein the first housing and the second housing have through holes for connecting optical fibers.

3. The optical node according to claim 1, further comprising at least one third housing housed within the first housing and housing said second housing.

4. The optical node according to claim 1, further comprising at least one of a water sensor and a humidity sensor disposed inside said first housing and outside said second housing.

5. The optical node according to claim 1, further comprising a plurality of water sensors disposed inside the first housing and outside the second housing, the plurality of water sensors being installed at different heights from the bottom surface of the first housing.

6. A water-immersion detection system comprising an optical node and an optical pulse tester, wherein the optical node comprises: a first housing; a second housing stored within the first housing; and a water-immersion detection module attached to an optical fiber located inside the first housing and outside the second housing, the water-immersion detection module causing bending loss to the optical fiber when submerged in water, wherein the first housing and the second housing are waterproof, an active device of the optical node is disposed within the second housing, and a passive device of the optical node is disposed inside the first housing and outside the second housing, and the optical pulse tester detects water immersion of the optical node by emitting an optical pulse to the optical fiber and detecting bending of the optical fiber using the reflected light of the optical pulse.

7. A water submersion detection system as described in claim 6, wherein the water submersion detection module is attached to an optical fiber that transmits a control signal to the optical node, the optical pulse tester emits the optical pulse to the optical fiber via an optical coupler, and the water submersion detection system further comprises: a first wavelength blocking filter that is different in wavelength from the light of the control signal and that is arranged in front of the light receiving unit of the active device and that blocks the wavelength of the optical pulse; and a second wavelength blocking filter that is arranged in front of the optical coupler and that blocks the wavelength of the optical pulse.

8. The water-immersion detection system according to claim 6, wherein the water-immersion detection module is attached to an optical fiber that transmits a control signal to the optical node, and further comprises a controller that drives the optical pulse tester when the control signal is not being transmitted or received.

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