PON system, management server, OLT, and method for determining position movement

Abstract

To prevent an optical network unit (ONU) from being used outside its installation location by appropriately detecting the positional movement of the ONU.SOLUTION: A passive optical network (PON) system 1 includes at least an optical line terminal (OLT) 30 which is a station-side device, and an optical network unit (ONU) 20 that is a home-side equipment connected to the OLT 30 by an optical fiber, and executes detection processing for detecting a change in a distance between the OLT 30 and the ONU 20, determination processing for determining whether the position of the ONU 20 has been moved on the basis of the change in distance detected by the detection processing, and output processing for performing output according to the determination result by the determination processing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a PON system, a management server, an OLT, and a method for determining position movement.

Background Art

[0002] Conventionally, in services such as FTTH (Fiber to the Home), a PON (Passive Optical Network) system that branches an optical signal into a plurality and shares a single optical fiber among a plurality of users has been used (see, for example, Patent Document 1). In the PON system, for example, an OLT (Optical Line Terminal) is used as a station-side device and an ONU (Optical Network Unit) is used as a home-side device, and an optical coupler that multiplexes and demultiplexes an optical signal is provided between the OLT and the ONU, so that a plurality of ONUs are connected to one OLT.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, in the case of a CATV (Community Antenna Television) operator or the like operating FTTH with a service using a PON system, the ONU is managed for each subscriber. In such a case, it is necessary to ensure that the ONU installed at the subscriber's home does not move to another place without permission. In particular, when providing a telephone service, it is required that a telephone notification be made from the ONU installed at the correct subscriber's home so as to avoid emergency calls and frauds from malicious subscribers.

[0005] In order to prevent the above-described situation, for example, a shape different from the general shape (plus or minus) is used for the housing of the ONU (such as Torx, self-developed screw, etc.) so that it cannot be physically replaced. However, in this case, from the perspective of the installation contractor, the management of screws and drivers becomes complicated. Moreover, not only is it complicated, but for example, if the ONU is replaced by some means, when the ONU moves within the same PON, there is no means to notice that the ONU has moved.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to prevent the ONU from being used outside the installation location by appropriately detecting the position movement of the ONU.

Means for Solving the Problems

[0007] A PON system according to an aspect of the present invention includes at least an OLT which is a station-side device and an ONU which is a home-side device connected to the OLT by an optical fiber, and includes a detection process for detecting a change in the distance between the OLT and the ONU, a determination process for determining whether or not the position movement of the ONU has been carried out based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process.

[0008] A management server according to an aspect of the present invention is a management server provided separately from an OLT which is a station-side device connected to an ONU which is a home-side device by an optical fiber, and includes a detection process for detecting a change in the distance between the OLT and the ONU, a determination process for determining whether or not the position movement of the ONU has been carried out based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process.

[0009] An OLT according to an aspect of the present invention is an OLT, which is a central office side device connected to an ONU, which is a customer side device, by an optical fiber, and includes a detection process for detecting a change in the distance from the ONU, and a determination process for determining whether or not the ONU has been relocated based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process.

[0010] A relocation determination method according to an aspect of the present invention is a method for determining the relocation of an ONU, which is a customer side device, implemented by a PON system, and includes a step of detecting a change in the distance between an OLT, which is a central office side device, and the ONU, a step of determining whether or not the ONU has been relocated based on the change in the distance detected in the detecting step, and a step of performing an output according to the determination result in the determining step.

Advantages of the Invention

[0011] According to the above, by appropriately detecting the relocation of the ONU, it is possible to prevent the ONU from being used outside the installation location.

Brief Description of the Drawings

[0012]

Figure 1

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Embodiments for Carrying Out the Invention

[0013] [Description of Embodiments of the Present Invention] First, embodiments of the present invention will be listed and described. A PON system according to one aspect of the present invention includes at least an OLT which is a station-side device and an ONU which is a home-side device connected to the OLT by an optical fiber, and includes a detection process for detecting a change in the distance between the OLT and the ONU, a determination process for determining whether or not the ONU has been moved based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result of the determination process.

[0014] In a PON system according to one aspect of the present invention, a change in the distance between the OLT and the ONU is detected, and it is determined whether or not the ONU has been moved based on the change in the distance. Then, in this PON system, an output according to the determination result (for example, a notification that the ONU has been moved) is performed. According to such a PON system, the movement of the ONU can be specified appropriately and with high accuracy based on the change in the distance between the OLT and the ONU. And, for example, when it is determined that the ONU has been moved, since that fact is output in the output process, the operator (such as a CATV operator) and subscribers of the service using the PON system can be appropriately informed of the movement of the ONU, and actions for preventing "the ONU being used outside the installation location" can be prompted. As described above, according to the PON system according to one aspect of the present invention, by appropriately detecting the movement of the ONU, it is possible to prevent the ONU from being used outside the installation location.

[0015] In the above PON system, in the detection process, the round-trip time between the OLT and the ONU may be obtained, and a change in the distance may be detected based on the change in the round-trip. By considering the round-trip, the distance between the OLT and the ONU can be specified appropriately. Thereby, it becomes possible to appropriately detect the movement of the ONU.

[0016] In the above PON system, in the detection process, the round-trip time between the OLT and the ONU is obtained by at least one of the following (a) or (b). (a) Repeated at a predetermined timing, (b) After the ONU restarts. In the determination process, when the absolute value of the difference between the acquired value, which is the value of the round-trip time obtained in the detection process, and the appropriate value of the pre-set round-trip time is greater than a predetermined first threshold value, it is determined that the ONU has been relocated. In the output process, when the ONU has been relocated, it may be notified that the relocation has been carried out. In this way, the round-trip time is obtained at a specific timing, compared with the appropriate value of the round-trip time (the value when the ONU is in the correct location), and when the difference from the appropriate value is greater than the predetermined first threshold value, it is notified that the ONU has been relocated. Thus, at the timing when the ONU has been relocated, the operator (such as a CATV operator) and subscribers of the service using the PON system can be appropriately informed of the relocation of the ONU. Thereby, it is possible to more reliably prevent the ONU from being used outside the installation location.

[0017] In the above PON system, in the detection process, when the absolute value of the difference between the first value, which is the value of the round-trip time between the OLT and the ONU obtained first, and the second value, which is the value of the round-trip time obtained after the acquisition of the first value, is smaller than a predetermined second threshold value, the second value may be determined as the appropriate value. In this way, by confirming that the difference between the successively acquired values of the round-trip time is small and setting the round-trip time as the above appropriate value, an appropriate round-trip time that is not a false detection or the like can be set as the appropriate value. That is, it becomes possible to detect the relocation of the ONU with higher accuracy.

[0018] In the above PON system, in the detection process, the round-trip time between the OLT and the ONU may be obtained at the timing when the ONU receives a notification that it has become online. At the timing when the ONU's position movement is performed, it is assumed that the ONU is restarted. Therefore, by obtaining the round-trip time at the timing when the ONU becomes online (restarted) and performing the determination related to the above-described position movement, it becomes possible to detect the position movement of the ONU immediately after the position movement of the ONU is performed.

[0019] The above PON system may further perform an intensity acquisition process for acquiring the intensity of the light transmitted from the ONU toward the OLT, and in the determination process, may further determine whether the ONU's position movement has been performed in consideration of the intensity of the light acquired in the intensity acquisition process. For example, when determining the position movement of the ONU only from the change in distance based on the round-trip time or the like, there is a possibility that the position movement of the ONU cannot be appropriately detected when the distance between the OLT and the ONU does not change much even though the position movement of the ONU is being performed. In this regard, by further considering the intensity of the light, for example, even when the change in the distance between the OLT and the ONU is small, based on the fact that the intensity of the light changes due to a change in the number of couplers in the optical path or the like, it becomes possible to appropriately detect the position movement of the ONU. That is, according to such a configuration, the position movement of the ONU can be more appropriately detected.

[0020] The above PON system may further include a management server provided separately from the OLT, and the management server may perform the detection process, the determination process, and the output process. Thereby, for example, even when the vendors of the OLT and the ONU are different, it is possible to appropriately detect the position movement of the ONU by the management server provided separately from the OLT.

[0021] The management server according to one aspect of the present invention is a management server provided separately from the OLT, which is a station-side device connected to the ONU, which is a home-side device, by an optical fiber. The management server is configured to perform a detection process for detecting a change in the distance between the OLT and the ONU, a determination process for determining whether or not the ONU has been moved based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process. According to the management server according to one aspect of the present invention, by appropriately detecting the movement of the ONU, it is possible to prevent the ONU from being used outside the installation location.

[0022] The OLT according to one aspect of the present invention is an OLT, which is a station-side device connected to the ONU, which is a home-side device, by an optical fiber. The OLT is configured to perform a detection process for detecting a change in the distance from the ONU, a determination process for determining whether or not the ONU has been moved based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process. According to the OLT according to one aspect of the present invention, by appropriately detecting the movement of the ONU, it is possible to prevent the ONU from being used outside the installation location. Further, by the OLT performing various processes, a simple device configuration can be achieved without providing a server (management server) separate from the OLT.

[0023] The position movement determination method according to one aspect of the present invention is a method for determining the position movement of the ONU, which is a home-side device, implemented by a PON system. The method includes a step of detecting a change in the distance between the OLT, which is a station-side device, and the ONU, a step of determining whether or not the ONU has been moved based on the change in the distance detected in the detecting step, and a step of performing an output according to the determination result in the determining step. According to the position movement determination method according to one aspect of the present invention, by appropriately detecting the movement of the ONU, it is possible to prevent the ONU from being used outside the installation location.

[0024] [Details of Embodiments of the Present Invention] A specific example of the PON system according to the embodiment of the present invention will be described below with reference to the drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant descriptions are omitted.

[0025] FIG. 1 is a system configuration diagram of the PON system 1 according to the present embodiment. The PON system 1 is a system operated by an operator such as a CATV (Community Antenna TeleVision) operator. The PON system 1 is a network system that branches an optical signal into a plurality of signals and shares a single optical fiber among a plurality of users in providing an FTTH (Fiber to the Home) service. As shown in FIG. 1, the PON system 1 includes a plurality of home-side devices ONU 20, a central-office-side device OLT 30, and a management server 40. The OLT 30 and the plurality of ONUs 20 are connected to each other via an FTTH network.

[0026] As shown in FIG. 1, the management server 40 and the OLT 30 are provided, for example, in the center of a CATV operator. Also, the plurality of ONUs 20 are provided, for example, in each subscriber's home. Terminals 80 such as a telephone 70 and a PC can be connected under the ONU 20 via an HGW (Home Gateway) 60.

[0027] The management server 40 is a server provided separately from the OLT 30, and is a server that manages information on each component included in the PON system 1 and controls each component. The management server 40 has a database 41. The database 41 holds a management list in which information on each component included in the PON system 1 is recorded.

[0028] FIG. 2 is a table showing an example of a management list recorded in the database 41 of the management server 40. In the example shown in FIG. 2, in the management list, ONU identification information, OLT identification information, distance information, time information, model discrimination, optical power (light intensity), and ONU status are managed in association with each other. These pieces of information are managed for each ONU 20. The ONU identification information is information that uniquely identifies the ONU 20, for example, a MAC address. The OLT identification information is information that uniquely identifies the OLT 30 to which the ONU 20 specified by the ONU identification information is connected, for example, a MAC address. The distance information is the value of the RTT (Round-Trip Time) between the OLT 30 and the ONU 20, and includes an initial value that is an appropriate value and an acquired value (details will be described later). The time information is information indicating the date and time when the distance information was acquired. Note that when it is determined that the ONU 20 has moved outside the installation location (details will be described later), the time information includes the movement date and time. The model discrimination is the model code of the ONU 20. The optical power is information indicating the upstream received light level (light intensity) from the ONU 20. The ONU status is information indicating whether the ONU 20 is in an online state where data communication is possible or an offline state.

[0029] The management server 40 implements a position movement determination method for determining the position movement (movement from the installation location) of each ONU 20. As processing related to the position movement determination of each ONU 20, the management server 40 implements detection processing, intensity acquisition processing, determination processing, and output processing.

[0030] In the detection process, the management server 40 detects changes in the distance between the OLT 30 and the ONU 20. Specifically, the management server 40 may obtain the RTT (Round Trip Time) between the OLT 30 and the ONU 20, and detect changes in the distance based on changes in the RTT. In this case, an initial value, which is an appropriate value of the RTT corresponding to the installation location of the ONU 20, is preset, and in the determination process described later, the movement of the ONU 20 is determined according to the difference from the initial value. The initial value of the RTT is determined as follows. That is, for the ONU 20 in the online state, when the absolute value of the difference between the first value, which is the value of the RTT obtained first, and the second value, which is the value of the RTT obtained after the acquisition of the first value, is smaller than a predetermined second threshold value (that is, when the difference between the continuously acquired RTT values is small), the management server 40 determines the second value as the initial value (appropriate value) of the RTT. By confirming that the difference between the two continuously acquired RTT values is small, it is possible to avoid setting an incorrect RTT value as the initial value due to false detection. The determined initial value of the RTT is managed as distance information in the management list of the database 41.

[0031] Then, in the state where the above-described initial value of the RTT is set, the management server 40 periodically obtains the RTT between the OLT 30 and the ONU 20 at a predetermined time interval. In addition, in the detection process, the management server 40 may obtain the RTT at the timing when it receives a notification from the OLT 30 that the ONU 20 has become online, separately from (independently of) the periodic RTT acquisition. This process is carried out because it is assumed that the ONU 20 becomes online (restarts) at the timing when the position of the ONU 20 is moved. The obtained RTT value is managed as distance information in the management list of the database 41. In addition, the acquisition date and time of the RTT are managed as time information in the management list of the database 41.

[0032] In the intensity acquisition process, the management server 40 acquires the intensity of the light transmitted from the ONU 20 toward the OLT 30. The acquired light intensity is managed as optical power in the management list of the database 41. Note that the intensity acquisition process does not necessarily have to be performed.

[0033] In the determination process, the management server 40 determines whether the ONU 20 has been relocated based on the change in the distance detected by the detection process. Specifically, the management server 40 determines that the ONU 20 has been relocated when the absolute value of the difference between the acquired value, which is the value of the RTT acquired in the detection process, and the initial value (appropriate value) of the preset round-trip time is greater than a predetermined first threshold. When it is determined that the ONU 20 has been relocated, the acquisition date and time of the RTT are managed as the relocation date and time included in the time information in the management list of the database 41.

[0034] The management server 40 may further determine whether the ONU 20 has been relocated in consideration of the light intensity (upward received light level from the ONU 20) acquired in the intensity acquisition process. For example, when determining the relocation of the ONU 20 only based on the change in the distance based on the RTT, there is a possibility that the relocation of the ONU 20 cannot be appropriately detected when the distance between the OLT 30 and the ONU 20 does not change much even though the ONU 20 has been relocated. In this regard, by further considering the light intensity, it becomes possible to appropriately detect the relocation of the ONU 20 based on the change in the light intensity due to, for example, a change in the number of couplers in the optical path even when the change in the distance between the OLT 30 and the ONU 20 is small.

[0035] In the output process, the management server 40 performs an output according to the determination result of the determination process. When it is determined in the determination process that the ONU 20 has been relocated, the management server 40 notifies (reports) that the relocation has been performed. Specifically, the management server 40 notifies the subscriber management personal terminal 90 that the relocation has been performed, for example, by email or the like.

[0036] Next, with reference to FIG. 3, the initial registration process in the PON system 1 according to this embodiment will be described. The initial registration process here is a process in which the ONU 20 is first connected to the OLT 30 and an initial value, which is an appropriate value of the RTT, is determined (set). FIG. 3 is a sequence diagram showing the initial registration process in the PON system 1. As a prerequisite for the execution of the process shown in FIG. 3, in the management server 40, settings and registrations such as MIB (Management Information Base) and CLI (Command Line Interface) for monitoring the states of each component are performed.

[0037] As shown in FIG. 3, first, the power of the ONU 20 is turned on (step S1). When the power of the ONU 20 is turned on, the ONU 20 transmits an ONU authentication request to the OLT 30 (specifically, the function related to EPON in the OLT 30) (step S2). When the OLT 30 receives the ONU authentication request, the OLT 30 transmits an ONU authentication response to the ONU 20 (step S3). Thereby, the authentication (registration) of the ONU 20 is completed, and the OLT 30 and the ONU 20 are associated (connected). The function related to EPON in the OLT 30 transmits an ONU registration completion notification to the dedicated software (virtual cable modem) in the OLT 30 (step S4).

[0038] The OLT 30 transmits a DHCP information request to the DHCP server included in the management server 40 (step S5). When the DHCP server receives the DHCP information request, it transmits a DHCP information response to the OLT 30 (step S6). As a result, the OLT 30 obtains the IP address of the ONU 20 from the DHCP server. Subsequently, the OLT 30 transmits a configuration file request to the TFTP server included in the management server 40 (step S7) and downloads the configuration file from the TFTP server (step S8). The OLT 30 performs ONU settings based on the content of the configuration file on the ONU 20 (step S9). As a result, the IP address and MAC address of the ONU 20 are linked and set, the ONU 20 becomes link-up capable, and online data communication becomes possible in the ONU 20 (step S10).

[0039] Subsequently, the OLT 30 transmits a notification (Trap) to the effect that the ONU 20 has become online to the management server 40 (step S11). The management software of the management server 40 registers various information related to the ONU 20 in the management list of the database 41 (step S12).

[0040] Then, the management software of the management server 40 acquires the information of the RTT's MIB by SNMP (Simple Network Management Protocol) (step S13). That is, the RTT between the OLT 30 and the ONU 20 is acquired (step S14) and transmitted to the management software of the management server 40. Subsequently, the management software of the management server 40 performs an RTT consistency confirmation process (step S15). Specifically, the RTT between the OLT 30 and the ONU 20 is acquired again (step S16), and the management software determines whether the difference between the value of the RTT acquired for the first time and the value of the RTT acquired for the second time is not greater than a predetermined value (i.e., whether there is consistency). If the difference between the value of the RTT acquired for the first time and the value of the RTT acquired for the second time is not greater than a predetermined threshold value (the second threshold value) and the RTT value is consistent, the RTT value is registered in the management list of the database 41 in association with the MAC address of the ONU 20 as an initial value (appropriate value) (step S17). The above is an example of the initial registration process.

[0041] Next, referring to FIG. 4, the periodic process in the PON system 1 according to the present embodiment will be described. The periodic process here is a process that is periodically performed to detect the movement of the ONU 20. FIG. 4 is a sequence diagram showing the periodic process in the PON system 1. It is assumed that the above-described initial registration process has been performed as a premise for the process shown in FIG. 4.

[0042] As shown in FIG. 4, when the power of the ONU 20 is turned off (step S101), the OLT 30 sends a notification (Trap) to the management server 40 indicating that the power of the ONU 20 is turned off and the link is disconnected (step S102). In this case, the management software of the management server 40 registers information indicating that the ONU 20 is in an offline state in the "ONU status" of the management list of the database 41 (step S103).

[0043] After the power of the ONU 20 is turned on (step S105), an ONU online sequence (step S106: the processes of steps S3 to S8 described above) is performed, ONU settings are performed (step S107), and the ONU 20 enters the online state (step S108). In this case, the OLT 30 sends a notification (Trap) to the management server 40 indicating that the ONU 20 has entered the online state (step S109), and the management software of the management server 40 registers information indicating that the ONU 20 is in the online state in the "ONU status" of the management list in the database 41 (step S110).

[0044] Then, the management software of the management server 40 periodically (for example, at a cycle of once a day) performs a polling process on the ONU 20 via the OLT 30 (step S111). In the polling process, the management server 40 acquires the RTT between the OLT 30 and the ONU 20. That is, the RTT between the OLT 30 and the ONU 20 is acquired (step S112) and sent to the management software of the management server 40. Subsequently, the management software of the management server 40 compares the acquired RTT value with the initial value (appropriate value) of the RTT registered in the management list of the database 41 (step S113), and determines that the position of the ONU 20 has moved when the absolute value of the difference between them is greater than a predetermined threshold (first threshold).

[0045] When the management software of the management server 40 determines that the position of the ONU 20 has moved, it sends a failure notification email notifying the subscriber management personal terminal 90 that the position has moved (step S114). Also, the management software of the management server 40 may send a file such as a CSV file recording the acquired RTT value to the subscriber management personal terminal 90 so that the acquired RTT value can be referenced if necessary (step S115). The above is an example of the periodic process.

[0046] Next, the above-described initial registration process, periodic process, and ONU restart process will be described in detail. The ONU restart process is a process that is executed separately (independently) from the periodic process, and is a process that is executed to detect the position movement of the ONU 20 when the ONU 20 restarts. Note that the above-described periodic process is a process of periodically acquiring the RTT, but the RTT only needs to be repeatedly acquired at a predetermined timing, and may be repeatedly acquired irregularly, for example.

[0047] FIG. 5 is a flowchart showing details of the initial registration process. In the initial registration process, the value of the first acquired RTT is set as the first value (RTT(A)) (step S1001). Thereafter, the ONU 20 is reset (step S1002), becomes online again (step S1003), and the value of the acquired RTT is set as the second value (RTT(B)) (step S1004). Then, it is determined whether the absolute value of the difference between the first value and the second value is smaller than a predetermined second threshold value (step S1005). If the absolute value of the difference between the first value and the second value is smaller than the predetermined second threshold value, the value of the second value is set as the initial value (RTT(C)) which is the appropriate value of the RTT (step S1006). On the other hand, if the absolute value of the difference between the first value and the second value is not smaller than the predetermined second threshold value, the processes after step S1002 are executed again.

[0048] FIG. 6 is a flowchart showing details of the ONU restart process. When the ONU 20 is restarted, the management server 40 receives a notification (start completion Trap) indicating that the ONU 20 has become online (step S2001). Then, at the timing when the management server 40 receives the start completion Trap, it acquires the RTT (step S2002) and stores the acquired RTT value (RTT(D)) in the database 41 (step S2003). Then, it is determined whether the absolute value of the difference between the acquired RTT value (RTT(D)) and the initial value (RTT(C)) is smaller than a predetermined first threshold (step S2004). If the absolute value of the difference between RTT(D) and RTT(C) is not smaller than the predetermined first threshold, it is determined that the ONU 20 has been relocated, and the operator and subscribers of the service are notified of the relocation of the ONU 20 by Trap reporting and email reporting, etc. (step S2005). On the other hand, if the absolute value of the difference between RTT(D) and RTT(C) is smaller than the predetermined first threshold, it is determined that the ONU 20 has not been relocated, and the initial value (RTT(C)) is also maintained as an appropriate value (step S2006).

[0049] FIG. 7 is a flowchart showing details of the periodic process. In the periodic process, polling processing (periodic polling) is periodically performed on the ONU 20 via the OLT 30 (step S3001). The management server 40 acquires the RTT by periodic polling (step S3002), and stores the acquired RTT value (RTT(D)) in the database 41 (step S3003). Then, it is determined whether the absolute value of the difference between the acquired RTT value (RTT(D)) and the initial value (RTT(C)) is smaller than a predetermined first threshold value (step S3004). If the absolute value of the difference between RTT(D) and RTT(C) is not smaller than the predetermined first threshold value, it is determined that the ONU 20 has been relocated, and the relocation of the ONU 20 is notified to the service operator and subscribers by Trap reporting, email reporting, etc. (step S3005). On the other hand, if the absolute value of the difference between RTT(D) and RTT(C) is smaller than the predetermined first threshold value, it is determined that the ONU 20 has not been relocated, and the initial value (RTT(C)) is also maintained as an appropriate value (step S3006).

[0050] Next, the operation and effect of the PON system 1 according to the present embodiment will be described.

[0051] The PON system 1 according to the present embodiment includes at least an OLT 30 which is a station-side device and an ONU 20 which is a home-side device connected to the OLT 30 by an optical fiber, and performs a detection process for detecting a change in the distance between the OLT 30 and the ONU 20, a determination process for determining whether the ONU 20 has been relocated based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process.

[0052] In such a PON system 1, a change in the distance between the OLT 30 and the ONU 20 is detected, and it is determined whether or not the ONU 20 has been moved based on the change in the distance. Then, in this PON system 1, an output according to the determination result (for example, a notification that the ONU 20 has been moved) is implemented. According to such a PON system 1, the movement of the ONU 20 can be specified appropriately and with high precision based on the change in the distance between the OLT 30 and the ONU 20. And, for example, when it is determined that the ONU 20 has been moved, since this is output in the output process, the operator of the service using the PON system 1 (such as a CATV operator) and the subscriber can be appropriately informed of the movement of the ONU 20, and actions for preventing "the ONU being used outside the installation location" can be promoted. As described above, according to the PON system 1 according to this embodiment, by appropriately detecting the movement of the ONU 20, it is possible to prevent the ONU 20 from being used outside the installation location. In such a PON system 1, it is possible to detect the movement of the ONU 20 without using physical fixtures such as screws.

[0053] In the above PON system 1, in the detection process, the RTT between the OLT 30 and the ONU 20 may be acquired, and based on the change in the RTT, a change in the distance may be detected. By considering the RTT, the distance between the OLT 30 and the ONU 20 can be specified appropriately. Thereby, it becomes possible to appropriately detect the movement of the ONU 20.

[0054] In the above PON system 1, in the detection process, the RTT between the OLT 30 and the ONU 20 is periodically acquired at a predetermined time interval. In the determination process, when the absolute value of the difference between the acquired value, which is the value of the RTT acquired in the detection process, and the proper value of the preset RTT is greater than a predetermined first threshold value, it is determined that the position of the ONU 20 has moved. In the output process, when the position of the ONU 20 has moved, it may be notified that the position has moved. In this way, the RTT is periodically acquired and compared with the proper value of the RTT (the value when the ONU 20 is in the correct position). When the difference from the proper value is greater than the predetermined first threshold value, it is notified that the position of the ONU 20 has moved. Thus, at the timing when the position of the ONU 20 has moved, the operator (such as a CATV operator) and subscribers of the service using the PON system 1 can be appropriately informed of the position movement of the ONU 20. Thereby, it is possible to more reliably prevent the ONU 20 from being used outside the installation location. Also, for example, when the vendors of the ONU 20 and the OLT 30 are different from each other, simply considering the absolute value of the RTT cannot appropriately derive the distance between the OLT 30 and the ONU 20, and there is a risk that the position movement of the ONU 20 cannot be appropriately detected. In this regard, in the PON system according to the present embodiment, since the position movement is detected by the difference from the proper value of the RTT, even when the vendors of the ONU 20 and the OLT 30 are different from each other regardless of the absolute value of the RTT, the position movement of the ONU 20 can be appropriately detected.

[0055] In the above PON system 1, in the detection process, when the absolute value of the difference between the first value, which is the value of the RTT between the OLT 30 and the ONU 20 acquired first, and the second value, which is the value of the RTT acquired after the acquisition of the first value, is smaller than a predetermined second threshold value, the second value may be determined as the proper value. In this way, by confirming that the difference between the continuously acquired RTT values is small and setting the RTT as the proper value, an appropriate RTT that is not a false detection or the like can be set as the proper value. That is, it becomes possible to detect the position movement of the ONU 20 with higher accuracy.

[0056] In the PON system 1 described above, in the detection process, the RTT between the OLT 30 and the ONU 20 may be acquired at the timing when the ONU 20 receives a notification that it has become online. At the timing when the position movement of the ONU 20 is carried out, it is assumed that the ONU 20 is restarted. Therefore, by acquiring the RTT at the timing when the ONU 20 becomes online (restarted) and performing the determination related to the above-described position movement, it becomes possible to detect the position movement of the ONU 20 immediately after the position movement of the ONU 20 is carried out.

[0057] The PON system 1 further performs an intensity acquisition process of acquiring the intensity of the light transmitted from the ONU 20 toward the OLT 30. In the determination process, the determination may be made as to whether or not the position movement of the ONU 20 has been carried out by further considering the intensity of the light acquired in the intensity acquisition process. For example, when determining the position movement of the ONU 20 only from the change in distance based on the RTT or the like, there is a possibility that the position movement of the ONU 20 cannot be appropriately detected when the distance between the OLT 30 and the ONU 20 does not change so much even though the position movement of the ONU 20 is being carried out. In this regard, by further considering the intensity of the light, for example, even when the change in the distance between the OLT 30 and the ONU 20 is small, based on the fact that the intensity of the light changes due to a change in the number of couplers in the optical path or the like, it becomes possible to appropriately detect the position movement of the ONU 20. That is, according to such a configuration, the position movement of the ONU 20 can be detected more appropriately.

[0058] The PON system 1 further includes a management server 40 provided separately from the OLT 30, and the management server 40 may perform the detection process, the determination process, and the output process. Thereby, for example, even when the vendors of the OLT 30 and the ONU 20 are different, it is possible to appropriately detect the position movement of the ONU 20 by the management server 40 provided separately from the OLT 30. Also, for an operator of a service such as a CATV operator, there is an advantage that the position movement of the ONU 20 can be detected by operating only the management server 40.

[0059] As described above, the PON system according to this embodiment has been explained. However, the present invention is not limited to these, and various modifications can be applied. Also, the disclosed embodiments should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

[0060] For example, although the management server 40 has been described as performing detection processing, determination processing, and output processing, it is not limited thereto. For example, the OLT 30 may perform these processes. By having the OLT 30 perform various processes, a simple device configuration can be achieved without providing a server (management server 40) separate from the OLT 30. Also, according to the present invention, since it is possible to prevent the ONU from being used outside the installation location, it is possible to relax the device (torque screw, uniquely developed screw, etc.) for preventing replacement in the ONU housing, and it is also possible for the customer to attach and detach the ONU regardless of the installation contractor.

Explanation of Reference Numerals

[0061] 1...PON system, 20...ONU, 30...OLT, 40...management server.

Claims

1. Comprising at least an OLT which is a network-side device and an ONU which is a customer-premises device connected to the OLT by an optical fiber, a detection process for detecting a change in the distance between the OLT and the ONU, a determination process for determining whether or not the ONU has been relocated based on the change in distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process, and configured to perform the above processes, in the detection process, obtaining a round-trip time between the OLT and the ONU, and detecting the change in distance based on the change in the round-trip time, in the detection process, obtaining the round-trip time between the OLT and the ONU by at least one of the following (a) or (b): (a) Repeating at a predetermined timing (b) After the ONU restarts in the determination process, when the absolute value of the difference between the acquired value which is the value of the round-trip time obtained in the detection process and the appropriate value of the pre-set round-trip time is greater than a predetermined first threshold value, it is determined that the ONU has been relocated, in the output process, when the ONU has been relocated, notifying that the relocation has been performed, in the detection process, when the absolute value of the difference between the first value which is the value of the round-trip time between the OLT and the ONU obtained first and the second value which is the value of the round-trip time obtained after the acquisition of the first value is smaller than a predetermined second threshold value, determining the second value as the appropriate value, a PON system.

2. In the detection process, obtaining the round-trip time between the OLT and the ONU at the timing when a notification indicating that the ONU has become online is received, the PON system according to Claim 1.

3. Further performing an intensity acquisition process for obtaining the intensity of the light transmitted from the ONU towards the OLT, in the determination process, further considering the intensity of the light obtained in the intensity acquisition process to determine whether or not the ONU has been relocated, the PON system according to Claim 1 or Claim 2.

4. Further comprising a management server provided separately from the OLT, the management server performing the detection process, the determination process, and the output process, the PON system according to any one of Claims 1 to 3.

5. A management server provided separately from an OLT, which is a station-side device connected to an ONU, which is a home-side device, by an optical fiber, a detection process for detecting a change in the distance between the OLT and the ONU, a determination process for determining whether or not the ONU has been relocated based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process, and is configured to perform the processes, In the detection process, a round-trip time between the OLT and the ONU is acquired, and a change in the distance is detected based on a change in the round-trip time, In the detection process, the round-trip time between the OLT and the ONU is acquired by at least one of the following (a) or (b): (a) Repeated at a predetermined timing (b) After the ONU restarts In the determination process, when the absolute value of the difference between the acquired value, which is the value of the round-trip time acquired in the detection process, and the appropriate value of the pre-set round-trip time is greater than a predetermined first threshold value, it is determined that the ONU has been relocated, In the output process, when the ONU has been relocated, it notifies that the relocation has been performed, In the detection process, when the absolute value of the difference between the first value, which is the value of the round-trip time between the OLT and the ONU acquired first, and the second value, which is the value of the round-trip time acquired after the acquisition of the first value, is smaller than a predetermined second threshold value, the second value is determined as the appropriate value. A management server.

6. An OLT, which is a station-side device connected to an ONU, which is a home-side device, by an optical fiber, a detection process for detecting a change in the distance from the ONU, a determination process for determining whether or not the ONU has been relocated based on the change in the distance detected by the detection process, and an output process for performing an output according to the determination result by the determination process, and is configured to perform the processes, In the detection process, the round-trip time between the OLT and the ONU is acquired, and a change in the distance is detected based on a change in the round-trip time, In the detection process, the round-trip time between the OLT and the ONU is acquired by at least one of the following (a) or (b): (a) Repeated at a predetermined timing (b) After the ONU restarts In the determination process, when the absolute value of the difference between the acquired value, which is the value of the round-trip time obtained in the detection process, and the appropriate value of the round-trip time set in advance is greater than a predetermined first threshold value, it is determined that the ONU has been relocated. In the output process, when the ONU has been relocated, it notifies that the relocation has been performed. In the detection process, when the absolute value of the difference between the first value, which is the value of the round-trip time between the OLT and the ONU acquired first, and the second value, which is the value of the round-trip time acquired after the acquisition of the first value, is smaller than a predetermined second threshold value, the second value is determined as the appropriate value. OLT. [

7. ] A method for determining the relocation of an ONU, which is a customer-side device implemented by a PON system, comprising: detecting a change in the distance between an OLT, which is a central-office-side device, and the ONU; determining whether the ONU has been relocated based on the change in the distance detected in the detecting step; performing an output according to the determination result in the determining step, In the detecting step, the round-trip time between the OLT and the ONU is acquired, and based on the change in the round-trip time, the change in the distance is detected. In the detecting step, the round-trip time between the OLT and the ONU is acquired by at least one of the following (a) or (b): (a) Repeating at a predetermined timing (b) After the ONU restarts In the determining step, when the absolute value of the difference between the acquired value, which is the value of the round-trip time obtained in the detecting step, and the appropriate value of the round-trip time set in advance is greater than a predetermined first threshold value, it is determined that the ONU has been relocated. In the outputting step, when the ONU has been relocated, it notifies that the relocation has been performed. In the detecting step, when the absolute value of the difference between the first value, which is the value of the round-trip time between the OLT and the ONU acquired first, and the second value, which is the value of the round-trip time acquired after the acquisition of the first value, is smaller than a predetermined second threshold value, the second value is determined as the appropriate value. Relocation determination method.

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