Station side optical line terminal device and registration method

Abstract

A station-side optical line terminal device comprises: a communication unit for communicating with a plurality of subscriber-side optical line terminal devices; and a control unit for dynamically changing at least one of a time width of a specific period and a cycle of the specific period, wherein the specific period is a period during which an authentication request signal is accepted from a new subscriber-side optical line terminal device via the communication unit.

Description

Technical Field

[0001] The invention relates to a station side optical line terminal device and a registration method. Background Art

[0002] As one of the optical access systems, a PON (Passive Optical Network) system including a station-side optical line terminal device (hereinafter referred to as “OLT”) and a subscriber-side optical line terminal device (hereinafter referred to as “ONU”) has been proposed.

[0003] Fig.10 1 is a diagram showing a configuration example of a conventional PON system 1000. The PON system 1000 includes an OLT 100 and a plurality of ONUs 200-1 to 200-N (N is an integer greater than or equal to 2). The OLT 100 and the ONUs 200-1 to 200-N are connected to each other so as to be communicable via an optical multiplexer / demultiplexer 300 including an optical transmission path and a splitter. In addition, when each of the plurality of ONUs 200-1 to ONUs 200-N is not distinguished, they are simply referred to as "ONUs 200".

[0004] In downstream communication from OLT 100 to ONU 200, OLT 100 transmits downstream signal 110 as continuous light to ONU 200. Each ONU 200 selectively receives a signal of an arbitrary time slot allocated to each ONU 200 among downstream signal 110 transmitted from OLT 100 via optical multiplexer / demultiplexer 300.

[0005] In the upstream communication, which is the communication from the ONU 200 to the OLT 100 , each ONU 200 transmits an upstream signal 210 , which is a burst signal intermittently in time, in a time slot allocated in advance by the OLT 100 according to the bandwidth requested by each ONU 200 .

[0006] In a case where the unauthenticated ONU 200 is communicably connected to the OLT 100 , an authentication process of the unauthenticated ONU 200 is performed. Fig.11 This is a diagram illustrating authentication processing and uplink communication on a conventional timeline.

[0007] The authentication process of ONU200 is performed periodically by OLT100, for example, to search for unconnected ONU200. During this period, data communication in upstream communication cannot be performed. Specifically, OLT100 sends a terminal authentication signal called a discovery gate to ONU200. ONU200 sends an authentication request signal called a register request to OLT100 along with the reception of the terminal authentication signal. Here, the unauthenticated ONU200 is not time-synchronized with OLT100 or other ONU200. Therefore, if each unauthenticated ONU200 receives a terminal authentication signal and simultaneously sends an authentication request signal to OLT100, the terminal authentication signal may conflict in the optical multiplexer / demultiplexer 300. Therefore, each unauthenticated ONU200 randomly delays the time of sending the authentication request signal, thereby suppressing the conflict of the terminal authentication signal. In addition, the time for randomly delaying the sending timing of the authentication request signal is called a random delay time.

[0008] If OLT100 receives the authentication request signal during a specific period called the discovery window, the ONU200 that sent the authentication request signal is registered by authenticating it. The specific period has a predetermined time width and is periodically set on the time axis. For example, the specific period is set by a value that includes the difference between the minimum and maximum values ​​of the propagation delay between OLT100 and ONU200 and the maximum value of the random delay time assigned to ONU200, the delay time of the processing of ONU200 or OLT100, and the like (for example, refer to non-patent document 1).

[0009] Prior art literature

[0010] Non-patent literature

[0011] Non-patent document 1: G.989.3: 40-Gigabit-capable passive optical networks (NG-PON2): Transmission convergence layer specification.

[0012] Non-patent document 2: R.Koma, M.Fujiwara, J.Kani, K.Suzuki and A.Otaka, "Burst-modedigital signal processing that pre-calculates FIR filter coefficients for digital coherent pon upstream," in IEEE / OSA Journal of Optical Communications and Networking, vol.10, no.5, pp.461-470, May 2018. Summary of the invention

[0013] Problems to be solved by the invention

[0014] However, if Fig.12 As shown in FIG. 1 , if the number of unauthenticated ONUs 200 increases, a conflict with authentication request signals sent by other ONUs 200 occurs. Therefore, there is a case where the time width of the specific period for accepting authentication request signals is increased in advance (for example, refer to non-patent document 2). However, in the conventional OLT 100, since the time width and cycle of the specific period once set cannot be changed, the time band in which upstream communication cannot be performed increases due to the time width of the set specific period, and the bandwidth utilization efficiency of upstream communication decreases.

[0015] In view of the above situation, an object of the present invention is to provide a technology capable of improving the bandwidth utilization efficiency of uplink communication.

[0016] Solutions to Solve Problems

[0017] One embodiment of the present invention is a station-side optical line terminal device, which includes: a communication unit that communicates with a plurality of subscriber-side optical line terminal devices; and a control unit that dynamically changes at least one of a time width of a specific period and a cycle of the specific period, wherein the specific period is a period during which an authentication request signal is accepted from a new subscriber-side optical line terminal device via the communication unit.

[0018] One embodiment of the present invention is a registration method for a station-side optical line terminal device to register a new subscriber-side optical line terminal device, wherein the registration method includes: a changing step of dynamically changing at least one of a time width of a specific period for accepting an authentication request signal from the new subscriber-side optical line terminal device and a cycle of the specific period; and a registration step of registering the subscriber-side optical line terminal device that sent the accepted authentication request signal when the authentication request signal is accepted from the new subscriber-side optical line terminal device within the specific period changed by the changing step.

[0019] Effects of the Invention

[0020] According to the present invention, the bandwidth utilization efficiency of uplink communication can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a diagram showing a configuration example of the optical communication system in the first embodiment.

[0022] Figure 2 This is a diagram showing an example of random delay information in the first embodiment.

[0023] Figure 3 This is a diagram showing the random delay information in the first embodiment in a table format.

[0024] Figure 4 It is a diagram for explaining the calculation method of the period T in the first embodiment.

[0025] Figure 5 This is a diagram showing an example of a trend of the timing of new authentication of an ONU in the past in the first embodiment.

[0026] Figure 6 This is a diagram showing the flow of the ONU registration method in the first embodiment.

[0027] Figure 7 This is a diagram for explaining a specific period in the first embodiment.

[0028] Figure 8 It is a diagram showing a modification example of the OLT of the first embodiment.

[0029] Fig. 9 It is a diagram showing a configuration example of an optical communication system in the second embodiment.

[0030] Fig.10 This is a diagram showing a configuration example of a conventional PON system 1000 .

[0031] Fig.11 This is a diagram illustrating authentication processing and uplink communication on a conventional timeline.

[0032] Fig.12 This is a diagram for explaining problems in conventional authentication processing. DETAILED DESCRIPTION

[0033] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0034] [First embodiment]

[0035] Figure 1 1 is a diagram showing a configuration example of an optical communication system 1 according to the first embodiment. The optical communication system 1 according to the first embodiment is, for example, a PON system.

[0036] The optical communication system 1 includes an OLT (Optical Line Terminal: station-side optical line terminal device) 10 and a plurality of ONUs (Optical Network Unit: subscriber-side optical line terminal device) 20-1 to 20-N. The OLT 10 and the ONUs 20-1 to 20-N are connected to each other so as to be communicable via an optical multiplexer / demultiplexer 30 including an optical transmission path and a splitter. In addition, when each of the plurality of ONUs 20-1 to ONUs 20-N is not distinguished, they are simply referred to as "ONU 20". The direction from the ONU 20 to the OLT 10 is called the upstream direction, and the direction from the OLT 10 to the ONU 20 is called the downstream direction.

[0037] The OLT 10 performs uplink communication or downlink communication with the ONU 20. The communication method of the uplink communication or the downlink communication is not particularly limited, and either a time division multiplexing method or a wavelength division multiplexing method can be used. In the downlink communication, the OLT 10 sends a downlink signal to the ONU 20. In the uplink communication, the OLT 10 receives an uplink signal from the ONU 20. In the case where an unauthenticated ONU 20 is communicatively connected to the OLT 10, the OLT 10 performs an authentication process of the unauthenticated ONU 20 to register the ONU 20. The authentication process of the ONU 20 is performed by the OLT 10, for example, periodically to search for the unconnected ONU 20. During this period, data communication in the uplink communication cannot be performed. Here, when performing the authentication process of the ONU 20, the OLT 10 dynamically changes at least one of the time width Δt and the period T of a specific period called the discovery window. As a result, the OLT 10 can improve the bandwidth utilization efficiency of the uplink communication.

[0038] Each ONU 20 selectively receives a signal of an arbitrary time slot allocated to each ONU 20 among the downlink signals transmitted from the OLT 10 via the optical multiplexer / demultiplexer 30. In the communication from the ONU 20 to the OLT 10, i.e., the uplink communication, each ONU 20 transmits an uplink signal as a temporally intermittent burst signal in a time slot previously allocated by the OLT 10 according to the bandwidth requested by each ONU 20.

[0039] Hereinafter, a schematic configuration of the OLT 10 for executing the authentication process according to the first embodiment will be described.

[0040] The OLT 10 includes a communication unit 11 and a control unit 12. Part or all of the control unit 12 may be implemented by, for example, a processor such as a CPU (Central Processing Unit) executing a program stored in a storage unit 13, or may be implemented using hardware such as an LSI (Large Scale Integration) or an ASIC (Application Specific Integrated Circuit).

[0041] The communication unit 11 transmits and receives optical signals with the ONU 20. For example, the communication unit 11 transmits a terminal authentication signal indicating an authentication request to the ONU 20. For example, the communication unit 11 receives an authentication request signal from the ONU 20.

[0042] When executing the authentication process of ONU20, the control unit 12 dynamically changes at least one of the time width Δt of a specific period and the period T of the specific period, wherein the specific period is a period during which an authentication request signal is received from a new ONU20 via the communication unit 11. As an example, the control unit 12 dynamically changes at least one of the time width Δt and the period T based on the authentication status of the plurality of ONU20. The authentication status of the plurality of ONU20 refers to information related to the authentication of the ONU20, including the time change of the number of unauthenticated ONU20 (hereinafter referred to as "unauthenticated number") and the number of newly authenticated ONU20 (hereinafter referred to as "new authenticated number"), etc.

[0043] Hereinafter, an example of the configuration of the control unit 12 will be described. The control unit 12 includes, for example, a storage unit 13, an authentication unit 14, a calculation unit 15, and a change unit 16.

[0044] The storage unit 13 stores a setting value of the time width Δt of the specific period (hereinafter referred to as a “first setting value”) and a setting value of the cycle T (hereinafter referred to as a “second setting value”).

[0045] The authentication unit 14 reads the first set value and the second set value stored in the storage unit 13. The authentication unit 14 accepts the authentication request signal from the unauthenticated ONU 20 during a specific period when the time width Δt is the first set value and the period T is the second set value. The authentication unit 14 does not accept the authentication request signal from the unauthenticated ONU 20 outside the specific period. When the authentication unit 14 accepts the authentication request signal during the specific period, it authenticates the ONU 20 that is the transmission source of the accepted authentication request signal, and registers the information of the authenticated ONU 20 in the storage unit 13.

[0046] The calculation unit 15 acquires the information on the authentication status of the ONU 20 from the authentication unit 14. Then, the calculation unit 15 calculates at least one of the time width Δt and the cycle T based on the information on the authentication status of the ONU 20.

[0047] The change unit 16 changes the first setting value stored in the storage unit 13 to the calculated value of the time width Δt calculated by the calculation unit 15. The change unit 16 changes the second setting value stored in the storage unit 13 to the calculated value of the period T calculated by the calculation unit 15. However, the change unit 16 only needs to change at least one of the first setting value and the second setting value, and does not need to change both setting values. That is, the change unit 16 changes either or both of the first setting value and the second setting value.

[0048] The change unit 16 sends a terminal authentication signal including information of the first setting value and the second setting value after the setting change from the communication unit 11 to each ONU 20. However, this is not limited to this. For example, the change unit 16 may also send a terminal authentication signal including the maximum value of the random delay time corresponding to the first setting value after the setting change and the second setting value after the setting change from the communication unit 11 to each ONU 20. For example, the change unit 16 may also set the random delay time of each unauthenticated ONU 20 corresponding to the first setting value after the setting change, and send a terminal authentication signal including the random delay time and the second setting value from the communication unit 11 to each ONU 20.

[0049] Furthermore, when the OLT 10 sends the information of the first setting value and the second setting value to the ONU 20, the information may be sent using a communication path different from the main signal of the uplink signal or the downlink signal. For example, the OLT 10 may send the information of the first setting value and the second setting value after the setting change to the ONU 20 using a different communication path such as a control signal superimposed on a frequency different from the main signal or wireless communication.

[0050] The following describes a schematic configuration of the ONU 20 for executing the authentication process of the present embodiment. The ONU 20 of the present embodiment includes a communication unit 21 , a control unit 22 , and a storage unit 23 .

[0051] The communication unit 21 transmits and receives optical signals with the communication unit 11. For example, the communication unit 21 receives a terminal authentication signal from the communication unit 11. The communication unit 21 transmits an authentication request signal to the communication unit 11 at a timing when a random delay time set in the storage unit 23 has passed after receiving the terminal authentication signal.

[0052] The control unit 22 stores the random delay time corresponding to the terminal authentication signal received by the communication unit 21 in the storage unit 23. For example, the control unit 22 changes the setting value of the random delay time stored in the storage unit 23 to the random delay time corresponding to the first setting value or the maximum value of the random delay time and the second setting value included in the terminal authentication signal.

[0053] The setting value of the random delay time is stored in the storage unit 23 . The setting value is updated by the control unit 22 .

[0054] Next, a method for calculating the time width Δt and the cycle T in the calculation unit 15 will be described. First, a method for calculating the time width Δt will be described.

[0055] (Calculation method of time width Δt)

[0056] The time width Δt includes a propagation delay amount and a random delay amount. The propagation delay amount refers to the time that takes into account the propagation delay between OLT100 and each ONU20, for example, the difference between the minimum value and the maximum value in each propagation delay is set as the initial value. The random delay amount is the maximum value of the random delay time set in the next specific period (authentication phase). Furthermore, the time width Δt may also include the delay time of the processing of ONU20 or OLT100. For example, the calculation unit 15 changes the value of the random delay amount based on the information of the authentication status of ONU20, thereby changing the time width Δt.

[0057] For example, the calculation unit 15 calculates the random delay amount in such a way that the probability P of the number of ONUs 20 expected to be authenticated in a specific period becomes greater than a preset threshold value Pth relative to the current unauthenticated number n. For example, the probability P is the probability of the number of ONUs 20 expected to be authenticated in the next specific period relative to the current unauthenticated number n.

[0058] The unauthenticated number n is the difference between the maximum number of authenticatable ONUs 20 and the number of authenticated ONUs 20. The maximum number of authenticatable ONUs 20 can be set to any value or can be set based on the number of users assigned to the OLT 100 from the operating system that describes service provision information.

[0059] The probability P is calculated as the expected value E(n) of the number of authenticated ONUs 20 by, for example, the following equation (1). The probability P may be calculated by, for example, the method described in Reference 1.

[0060] (Reference 1: Glen Kramer "Ethernet Passive Optical Networks" Communications Engineers, 28 / 04 / 2005.) However, the present invention is not limited to this, and for example, the probability P may be a value obtained by dividing the expected value E(n) by the current authentication number n.

[0061] [Formula 1]

[0062]

[0063] In the formula (1), W is the maximum value of the random delay time of the current unauthenticated ONU 20. In the formula (1), M is the signal length of the uplink signal, and n is the current unauthenticated number.

[0064] As an example, the calculation unit 15 has random delay information in advance that associates the probability P with the random delay amount for each unauthenticated number n. The random delay information may be determined experimentally or theoretically, for example. The random delay information may be in the form of a calculation formula, a table, or other forms.

[0065] Figure 2 This is a diagram showing an example of random delay information. Figure 2 In the graph, the horizontal axis is the random delay amount, and the vertical axis is the value of the probability P(E(n) / n) in percentage. Figure 2 In FIG. 1 , as an example of random delay information, the relationship between the probability P and the random delay amount for five unauthenticated numbers n1, n2, n3, n4, and n5 is shown. The magnitude relationship of the five unauthenticated numbers n is n1<n2<n3<n4<n5. Figure 3 is a graph that represents random delay information in table form. Figure 2 and Figure 3 As shown, in the random delay information, as the number of unauthenticated persons n increases, the probability P becomes a random delay amount greater than the threshold value Pth. In other words, it is shown that as the number of unauthenticated persons n decreases, the probability P satisfies the threshold value Pth. Therefore, if the authentication process is performed several times and the number of unauthenticated persons n gradually decreases, the random delay amount becomes a smaller value.

[0066] The calculation unit 15 obtains information about the current number of unauthenticated persons n from the authentication unit 14, and calculates the random delay amount in which the probability P becomes greater than the probability Pth in the obtained current number of unauthenticated persons n, based on random delay information in a table format, for example. Thus, as an example, the calculation unit 15 can calculate the time width Δt corresponding to the authentication status of the ONU 20. For example, the calculation unit 15 uses the propagation delay amount as an initial value and the random delay amount as a calculated value to calculate the time width Δt. However, the present invention is not limited thereto, and the calculation unit 15 can also change the time width Δt by making the propagation delay amount variable. For example, the calculation unit 15 can calculate the propagation delay amount based on the maximum transmission distance set by the user / operator. In this case, the calculation unit 15 can use the propagation delay amount as a calculated value and the random delay amount as a calculated value or a maximum value W to calculate the time width Δt. Furthermore, the calculated value of the random delay amount calculated by the calculation unit 15 can be any random delay amount in which the probability P is greater than the probability Pth, but it is preferred that the random delay amount is small.

[0067] (Calculation method of period T)

[0068] The cycle T of a specific period is calculated based on the time change of the number of new authentications. For example, the calculation unit 15 may extend the interval of the authentication phase when the number of new authentications is below the threshold value Uth in the preset time interval ΔK, that is, calculate a cycle longer than the currently set cycle T (second set value) as the cycle T. In addition, the case where the number of new authentications is below the threshold value Uth includes the case where the number of new authentications is zero.

[0069] For example, when the new authentication number U is less than the threshold Uth in the time interval ΔK from when the new authentication number greater than the threshold Uth exists to when a certain time has passed, the calculation unit 15 calculates the cycle T of the specific period so that the interval of the next authentication phase is wider than the interval of the current authentication phase.

[0070] Figure 5 2 is a diagram showing an example of the trend of the timing of new authentication of ONU 20 in the past. Figure 5 As shown, in the case where the timing of the new authentication of ONU 20 has periodicity, the calculation unit 15 can calculate the period T of the specific period according to the trend of the timing of the new authentication. For example, the calculation unit 15 can obtain information showing the trend of the timing of the new authentication of ONU 20 in each predetermined period such as every day or every hour in advance, and calculate the period T in a manner such that the specific period is set at the timing when the new authentication of ONU 20 exists and the specific period is not set at the timing when the new authentication of ONU 20 does not exist.

[0071] (ONU registration method flow)

[0072] Next, the flow of the registration method of the ONU 20 in the first embodiment will be described. Figure 6 1 is a diagram showing the flow of the registration method of the ONU 20 in the first embodiment. For example, the optical communication system 1 repeats steps S101 to S105, and changes at least one of the time width Δt and the cycle T every specific period. Figure 6 In the description of , as an example, both the time width Δt and the cycle T are changed.

[0073] The OLT 10 calculates the time width Δt and the cycle T of the specific period according to the authentication status of the ONU 20 (step S101). The OLT 10 sets and changes the first setting value and the cycle T stored in the storage unit 13 to the calculated values ​​calculated in step S101 (step S102). Figure 7 As shown, the time width Δt and cycle T of the specific period of the present embodiment are dynamically changed for each specific period, for example, instead of being fixed values. Thus, the OLT 10 can improve the bandwidth utilization efficiency of the upstream communication.

[0074] The OLT 10 transmits a terminal authentication signal including the calculated values ​​of the time width Δt and the cycle T calculated in step S101 to the ONU 20 (step S103 ).

[0075] ONU 20 receives the terminal authentication signal from OLT 10, and sends an authentication request signal at a random delay time corresponding to each calculated value included in the received terminal authentication signal (step S104). When OLT 10 accepts the authentication request signal within the specific period in which the time width Δt and the cycle T are changed in step S102, it registers (discovers) the ONU 20 that sent the accepted authentication request signal (step S105).

[0076] As described above, the OLT 10 in the first embodiment dynamically changes at least one of the time width Δt and the cycle T of the specific period during which the authentication request signal is received from the new ONU 20. Thus, the OLT 10 can reduce the time band during which upstream communication is disabled and improve the bandwidth utilization efficiency of upstream communication.

[0077] (Variation Example)

[0078] Figure 8 FIG. 1 is a diagram showing a modified example of the OLT 10 of the first embodiment. Figure 8 As shown, the OLT 10 may further include a monitoring control unit 40. Hereinafter, the modified example of the OLT 10 is referred to as OLT 10A.

[0079] The OLT 10A includes a communication unit 11, a control unit 12A, and a monitoring control unit 40. The control unit 12A includes a storage unit 13, an authentication unit 14, a calculation unit 15A, and a change unit 16, for example.

[0080] The monitoring control unit 40 sends an initialization signal to the control unit 12A when a failure of the OLT 10A is detected. The monitoring control unit 40 detects a restart of the OLT 10A, and sends an initialization signal to the control unit 12A when a restart is detected. The monitoring control unit 40 sends an initialization signal to the control unit 12A when a signal interruption of at least one of the uplink signal and the downlink signal is detected.

[0081] The calculation unit 15A has the same function as the calculation unit 15. When the calculation unit 15A receives an initialization signal from the monitoring and control unit 40, it performs an initialization action. The initialization action refers to an action of changing the time width Δt of a specific period and the cycle T of the specific period to a preset value. For example, when the calculation unit 15A receives an initialization signal from the monitoring and control unit 40, it changes the time width Δt of the specific period to the maximum value of the settable time width Δt and changes the cycle T of the specific period to the minimum value of the settable cycle. Thus, when it is predicted that a plurality of new ONUs 20 are connected to the startup of the OLT 10 at the same time, the OLT 10A can authenticate more new ONUs 20 by performing the initialization action.

[0082] [Second embodiment]

[0083] Fig. 9 1 is a diagram showing a configuration example of an optical communication system 1B in the second embodiment. In the optical communication system 1B in the second embodiment, OLT 10 and ONU 20 communicate using multiple wavelengths. In the following description, for parts having the same functions as those described in the first embodiment, the same names and symbols are marked, and specific descriptions related to the functions are omitted.

[0084] The optical communication system 1B includes an OLT 10B and a plurality of ONUs 20B-1 to 20B-N. The OLT 10B and the ONUs 20B-1 to 20B-N are connected to each other so as to be communicable via an optical multiplexer / demultiplexer 30 including an optical transmission path and a splitter. When each of the plurality of ONUs 20B-1 to 20B-N is not distinguished, they are simply referred to as "ONUs 20B".

[0085] For example, OLT10B and a plurality of ONU20B-1 to 20B-N communicate by a communication method using wavelength division multiplexing technology. Therefore, ONU20B-1 to 20B-N transmit optical signals of different wavelengths. Furthermore, it is not necessary for all ONU20B-1 to 20B-N to transmit optical signals of different wavelengths, and some of them may transmit optical signals of different wavelengths. In the following description, the case where all ONU20B-1 to 20B-N transmit optical signals of different wavelengths is used as an example for description.

[0086] like Fig. 9 As shown, the OLT 10B includes a communication unit 11B and a control unit 12B. Part or all of the control unit 12B may be implemented by, for example, a processor such as a CPU executing a program stored in a storage unit 13B, or may be implemented using hardware such as an LSI or an ASIC.

[0087] The communication unit 11B communicates bidirectionally with the ONU 20B using wavelength division multiplexing technology. For example, the communication unit 11B includes a plurality of optical transceivers 50 and a multiplexer / demultiplexer 60 .

[0088] The plurality of optical transceivers 50 are connected to the control unit 12B. The plurality of optical transceivers 50 generate optical signals of different wavelengths and transmit them to the multiplexer / demultiplexer 60. The plurality of optical transceivers 50 receive the optical signals demultiplexed for each wavelength from the multiplexer / demultiplexer 60.

[0089] The multiplexer / demultiplexer 60 multiplexes a plurality of optical signals of different wavelengths generated by a plurality of optical transceivers 50 to generate a downstream WDM signal. The downstream WDM signal is transmitted to ONU20B-1 to 20B-N. The multiplexer / demultiplexer 60 receives an upstream WDM signal obtained by multiplexing the upstream signals from each ONU20B by the optical multiplexer / demultiplexer 30. Then, the multiplexer / demultiplexer 60 demultiplexes the upstream WDM signal and outputs it to each optical transceiver 50.

[0090] The control unit 12B has the same structure as the control unit 12. The control unit 12B may also include the above-mentioned monitoring control unit 40. Here, the control unit 12B may manage the number of ONUs 20B registered for each wavelength, and set the time width Δt and the cycle T of a specific period based on the authentication status of the ONUs 20B managed by it. In this case, the control unit 12B may, for example, set the unauthenticated number n to a value obtained by dividing the number of ONUs 20B of the entire optical communication system 1B by the number of wavelengths. In the OLT 10B, the maximum number of registered ONUs 20B for each wavelength may also be registered in advance. The number of ONUs 20B registered in the OLT 10B may also be the sum of all wavelengths, and the control unit 12B may also control the time width ΔT and the cycle T in general.

[0091] The following describes a schematic configuration of the ONU 20B for executing the authentication process of the present embodiment. The ONU 20B of the present embodiment includes a communication unit 21B, a control unit 22 , and a storage unit 23 .

[0092] The communication unit 21B transmits and receives optical signals with the communication unit 11B. For example, the communication unit 21B communicates with the communication unit 11B by a communication method using wavelength division multiplexing technology.

[0093] The calculation method of the time width Δt and the cycle T in the second embodiment is the same as that in the first embodiment, and thus the description thereof is omitted. The flow of the registration method of the ONU 20B in the second embodiment is the same as that in the first embodiment, and thus the description thereof is omitted.

[0094] As described above, the OLT 10B in the second embodiment achieves the same effects as those of the first embodiment.

[0095] The functions of part of the OLT 10, 10A, 10B and ONU 20, 20B in the above-mentioned embodiment can be realized by a computer. In this case, a program for realizing the function can be recorded in a computer-readable recording medium, and the computer system can read the program recorded in the recording medium and execute it, thereby realizing the functions of part of the OLT 10, 10A, 10B and ONU 20, 20B in the above-mentioned embodiment. In addition, the "computer system" mentioned here includes hardware such as OS and peripheral devices. In addition, the "computer-readable recording medium" refers to a removable medium such as a floppy disk, a magneto-optical disk, a ROM, a CD-ROM, and a storage device such as a hard disk built into the computer system. Furthermore, the "computer-readable recording medium" can also include a medium that dynamically retains the program for a short period of time, such as a communication line when the program is transmitted via a network such as the Internet or a communication line such as a telephone line, and a medium that retains the program for a certain period of time, such as a volatile memory inside a computer system that becomes a server or client in this case. In addition, the above-mentioned program can be a program for realizing a part of the aforementioned functions, or a program that can realize the aforementioned functions by combining with a program already recorded in a computer system, or a program realized using a programmable logic device such as FPGA.

[0096] As mentioned above, although the embodiment of the present invention is described in detail with reference to the drawings, the specific structure is not limited to this embodiment, and includes designs and the like within the scope that does not depart from the gist of the present invention.

[0097] Throughout the specification, when a part “includes,” “has,” or “has” a certain constituent element, this means that other constituent elements are not excluded and the part may further include other constituent elements unless there is a particular description to the contrary.

[0098] In addition, the term "unit" described in the specification means a unit that processes at least one function or action, which can be embodied as hardware or software, or a combination of hardware and software.

[0099] Industrial Applicability

[0100] The present invention can be applied to a station-side optical line terminal device that communicates with a plurality of subscriber-side optical line terminal devices.

[0101] Description of Reference Numerals

[0102] 1…Optical communication system

[0103] 10, 10A, 10B…OLT

[0104] 11, 11B…Communications Department

[0105] 12, 12A, 12B…control unit

[0106] 13… Storage

[0107] 14…Certification Department

[0108] 15, 15A…Calculation Department

[0109] 16…Change Department

[0110] 20, 20B…ONU.

Claims

1. A station-side optical line terminal device, wherein: have: a communication unit that communicates with a plurality of subscriber-side optical line terminal devices; and a control unit that dynamically changes at least one of a time width of a specific period and a cycle of the specific period, wherein the specific period is a period during which an authentication request signal is received from the new subscriber-side optical line terminal device via the communication unit, The control unit changes at least one of a time width of the specific period and a cycle of the specific period based on the authentication status of the plurality of subscriber-side optical line terminal devices. The control unit changes the time width so that a probability of the number of subscriber optical line terminal devices to be authenticated relative to unauthenticated subscriber optical line terminal devices, that is, the number of unauthenticated subscriber optical line terminal devices, during one specific period becomes equal to or larger than a preset threshold.

2. The station-side optical line terminal device according to claim 1, wherein: The control unit changes the cycle of the specific period based on a temporal change in the number of subscriber-side optical line terminal devices that are newly authenticated.

3. The station-side optical line terminal device according to claim 2, wherein: The control unit changes the cycle of the specific period to a cycle longer than the current cycle when the number of subscriber-side optical line terminal devices newly authenticated in a preset time interval is equal to or smaller than a threshold value.

4. The station-side optical line terminal device according to any one of claims 1 to 3, wherein: The communication unit transmits at least one of the time width and the cycle changed by the control unit to the subscriber-side optical line terminal device.

5. The station-side optical line terminal device according to claim 1, wherein: The communication unit communicates with the plurality of subscriber-side optical line terminal devices using a plurality of wavelengths, The control unit manages the number of the subscriber optical line terminal devices for each wavelength, and changes at least one of a time width and a cycle of the specific period based on the managed authentication status of the subscriber optical line terminal devices.

6. A registration method for a station-side optical line terminal device to register a new subscriber-side optical line terminal device, wherein: The registration method includes: a changing step of dynamically changing at least one of a time width of a specific period for accepting an authentication request signal from a new subscriber-side optical line terminal device and a cycle of the specific period; and a registering step of registering the subscriber side optical line terminal device that sent the accepted authentication request signal when the authentication request signal is accepted from the new subscriber side optical line terminal device within the specific period after the change step; In the changing step, at least one of a time width of the specific period and a cycle of the specific period is changed based on the authentication status of a plurality of subscriber-side optical line terminal devices. In the changing step, the time width is changed so that the probability of the number of subscriber optical line terminal devices to be authenticated relative to the number of unauthenticated subscriber optical line terminal devices during the specific period becomes equal to or larger than a preset threshold.

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