Optical communication device, control method, and control program

Abstract

To make it possible to communicate with an ONU that requires a transmission preparation time.SOLUTION: An ONU 100 is included in an optical communication system that includes an ONU 200 and an OLT 300, and prepares to transmit a report frame to the OLT 300 in a period of time from after completion of transmitting a data frame to before transmitting the report frame. The ONU 100 includes: a storage unit 110 that stores data: a communication unit 120 that receives a normal gate frame including a first transmission start clock time and a first transmission time from the OLT 300; and a control unit 130 that changes the first transmission time to a second transmission time shorter than the first transmission time. When receiving the normal gate frame, the communication unit 120 transmits a data frame based on the data to the OLT 300 during the second transmission time from the first transmission start clock time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an optical communication device, a control method, and a control program. [Background technology]

[0002] A PON (Passive Optical Network) system is known as an optical communication system. A PON system includes an optical communication device (also called a master station) installed in a telecommunications carrier's central office and multiple optical communication devices (also called slave station devices) on the subscriber side (also called slave station side). The master station is called an OLT (Optical Line Termination). The slave station is called an ONU (Optical Network Unit). The OLT also includes an OSU (Optical Subscriber Unit). The OSU is also called an optical line terminal.

[0003] PON systems provide FTTH (Fiber To The Home) services, in which data is transferred between an upper network and a user network connected to an ONU. In a PON system, time division multiplexing is used to prevent collisions between optical signals. Time division multiplexing technology has been disclosed (see Patent Document 1).

[0004] Also, the MPCP (Multi-Point Control Protocol) process is known as a method for preventing collisions of optical signals. The MPCP process will be explained below. The OSU performs dynamic bandwidth allocation (DBA). During the dynamic bandwidth allocation process, the OSU transmits a Normal Gate frame to the ONU at each bandwidth update period. When the ONU receives a Normal Gate frame, it generates a Report frame based on the amount of data stored in the ONU. The ONU transmits the Report frame to the OSU. When the OSU receives a Report frame, it generates a Normal Gate frame based on the amount of data and the bandwidth used. The Normal Gate frame includes a transmission start time (GST: Grant Start Time) and a transmission time (GL: Grant Length). The OSU transmits the Normal Gate frame to the ONU. When the ONU receives a Normal Gate frame, it transmits a Report frame and a Data frame based on the data stored in the ONU to the OSU based on the transmission start time and transmission time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-13424 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, a PON system may contain a mixture of ONUs that require transmission preparation time and ONUs that do not. For ONUs that require transmission preparation time, the OSU must determine the transmission start time taking the transmission preparation time into consideration. However, the OSU cannot distinguish between ONUs that require transmission preparation time and ONUs that do not require transmission preparation time. Furthermore, determining the transmission start time in a PON system requires extensive development. Furthermore, since the management method becomes complicated, it is difficult to equip the OSU with the management function. As such, various problems arise when communicating with ONUs that require transmission preparation time. Therefore, unless these problems are resolved, communication with ONUs that require transmission preparation time cannot be achieved.

[0007] The purpose of this disclosure is to communicate with ONUs that require transmission preparation time. [Means for solving the problem]

[0008] An optical communication device according to one aspect of the present disclosure is provided. The optical communication device is included in an optical communication system including a master station device and a slave station device that does not prepare to transmit first information to the master station device, the first information being information used by the master station device to determine data transmission timing for the slave station device, between the completion of transmission of a data frame and the transmission of the first information, and the slave station device that performs the preparation between the completion of transmission of the data frame and the transmission of the first information. The optical communication device includes a storage unit that stores data, a communication unit that receives second information from the master station device, the second information including a first transmission start time and a first transmission duration, and In order to ensure time for the above preparations, and a control unit that changes the first transmission time to a second transmission time that is shorter than the first transmission time. When the communication unit receives the second information, the communication unit transmits a data frame based on the data to the master station device from the first transmission start time until the second transmission time. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to communicate with an ONU that requires transmission preparation time. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a PON system according to a first embodiment. [Figure 2] 2 is a diagram illustrating hardware included in an ONU according to the first embodiment. FIG. [Figure 3] 2 is a block diagram showing the functions of an ONU according to the first embodiment. FIG. [Figure 4] 10A and 10B are diagrams showing examples of timing charts according to the first embodiment. [Figure 5] 10 is a flowchart illustrating an example of processing executed by an ONU according to the first embodiment. [Figure 6] FIG. 10 is a block diagram showing the functions of an ONU according to a second embodiment. [Figure 7] 10 is a flowchart illustrating an example of processing executed by an ONU according to the second embodiment. [Figure 8] FIG. 11 is a block diagram showing the functions of an ONU according to a third embodiment. [Figure 9] 11 is a flowchart illustrating an example of processing executed by an ONU according to the third embodiment. [Figure 10] FIG. 10 is a block diagram showing the functions of an ONU according to a fourth embodiment. [Figure 11] 10A and 10B are diagrams showing examples of timing charts according to the fourth embodiment. [Figure 12] 13 is a flowchart illustrating an example of processing executed by an ONU according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings. The following embodiments are merely examples, and various modifications are possible within the scope of the present disclosure.

[0012] Embodiment 1 1 is a diagram showing a PON system according to the first embodiment. The PON system includes ONUs 100_1, . . . , 100_n, ONUs 200_1, . . . , 200_n, and an OLT 300. The PON system uses the MPCP process. The ONUs 100_1, . . . , 100_n, the ONUs 200_1, . . . , 200_n, and the OLT 300 communicate with each other via optical splitters 400_1, . . . , 400_n. OLT300 includes OSUs 310_1, . . . , 310_n.

[0013] In the following description, ONUs 100_1, . . . , 100_n will be collectively referred to as ONU100, ONUs 200_1, . . . , 200_n will be collectively referred to as ONU200, and OSUs 310_1, . . . , 310_n will be collectively referred to as OSU310.

[0014] The ONU 100 and the ONU 200 receive data from terminal devices via a user network. The terminal devices are not shown in the figure. The ONU 100 and the ONU 200 store the received data.

[0015] Here, the difference between ONU100 and ONU200 will be explained. ONU100 is an ONU that requires transmission preparation time. ONU200 is an ONU that does not require transmission preparation time. The difference between ONU100 and ONU200 will be explained in detail. ONU100 prepares to transmit a Report frame to OLT300 during the period from after completion of transmission of a Data frame to before transmission of a Report frame. ONU100 is an ONU that requires transmission preparation time because it makes preparations during this period. On the other hand, ONU200 does not make preparations to transmit a Report frame to OLT300 during the period from after completion of transmission of a Data frame to before transmission of a Report frame. ONU200 is an ONU that does not require transmission preparation time because it does not make preparations during this period.

[0016] The Report frame is information used when the OLT 300 determines the data transmission timing of the ONU. The Report frame is also referred to as first information.

[0017] Based on the Report frame, OLT300 (more specifically, OSU310) determines the transmission start time and transmission duration of the Report frame and the transmission start time and transmission duration of the Data frame. OLT300 (more specifically, OSU310) transmits a Normal Gate frame, which includes the transmission start time and transmission duration of the Report frame and the transmission start time and transmission duration of the Data frame, to ONU100 and ONU200. Here, the Normal Gate frame is also referred to as second information.

[0018] ONU100 and ONU200 receive the Normal Gate frame. Based on the transmission start time and transmission duration included in the Normal Gate frame, ONU100 and ONU200 transmit a Report frame and a Data frame based on data stored in their own device to OSU310.

[0019] The OSU 310 is connected to an upper network, and when the OSU 310 receives a data frame, it transmits the data frame to the upper network.

[0020] Next, the hardware of the ONU 100 will be described. FIG. 2 is a diagram illustrating hardware included in the ONU according to the first embodiment. The ONU 100 includes a processor 101 , a volatile storage device 102 , and a non-volatile storage device 103 .

[0021] The processor 101 controls the entire ONU 100. For example, the processor 101 is a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array). The processor 101 may be a multiprocessor. The ONU 100 may have a processing circuit instead of the processor 101. The processing circuit may be a single circuit or a composite circuit.

[0022] The volatile storage device 102 is a main storage device of the ONU 100. For example, the volatile storage device 102 is a random access memory (RAM). The nonvolatile storage device 103 is an auxiliary storage device of the ONU 100. For example, the nonvolatile storage device 103 is a flash memory, a hard disk drive (HDD), or a solid state drive (SSD).

[0023] Next, the functions of the ONU 100 will be described. 3 is a block diagram showing the functions of the ONU according to the first embodiment. The ONU 100 is a device that executes the control method. The ONU 100 includes a storage unit 110, a communication unit 120, a control unit 130, and a UNI (User Network Interface) function unit 140.

[0024] The storage unit 110 may be realized as a storage area secured in the volatile storage device 102 or the non-volatile storage device 103 . Some or all of the communication unit 120, the control unit 130, and the UNI function unit 140 may be realized by a processing circuit. Also, some or all of the communication unit 120, the control unit 130, and the UNI function unit 140 may be realized as a program module executed by the processor 101. For example, the program executed by the processor 101 is also referred to as a control program. For example, the control program is recorded on a recording medium.

[0025] The storage unit 110 stores various information, such as data received via a user network. The communication unit 120 communicates with the OSU 310. The communication unit 120 also converts optical signals received from the OSU 310 into electrical signals. The communication unit 120 then converts the electrical signals into optical signals and transmits the converted optical signals to the OSU 310.

[0026] The communication unit 120 receives from the OSU 310 a Normal Gate frame including the transmission start time of the Report frame, the transmission duration of the Report frame, the transmission start time of the Data frame, and the transmission duration of the Data frame. The control unit 130 changes the transmission time of the Data frame to a transmission time that is shorter than the transmission time. The detailed function of the control unit 130 will be described later. The UNI function unit 140 communicates with terminal devices via a user network.

[0027] Next, a timing chart in the PON system will be described. 4(A) and (B) are diagrams showing examples of timing charts according to the first embodiment. FIG. 4(A) shows a case where one ONU 100 is included in a PON system. FIG. 4(A) shows a bandwidth update cycle (DBA_cycle) for dynamic bandwidth allocation processing. The ONU 100 transmits a Report frame and a Data frame to the OSU 310 within the bandwidth update cycle.

[0028] The above describes the differences between the ONU 100 and the ONU 200. The differences between the ONU 100 and the ONU 200 will be explained again with reference to FIG. The ONU 100 prepares to transmit a Report frame in DBA_cycle(n+1) to the OSU 310 during the period from when the Data frame transmission in DBA_cycle(n) is completed until the Report frame transmission in DBA_cycle(n+1) begins. This preparation will be described in detail. The ONU 100 checks the amount of data in the storage unit 110. The ONU 100 generates a Report frame including the checked amount of data. The generated Report frame is transmitted at the transmission start time GST1(n+1).

[0029] On the other hand, ONU200 does not prepare to transmit a Report frame to OSU310 between DBA_cycle(n) and DBA_cycle(n+1). ONU200 prepares to transmit a Report frame to OLT300 during DBA_cycle(n). This preparation will be explained in detail. ONU200 subtracts the amount of data in the Data frame transmitted during DBA_cycle(n) from the amount of data in the memory unit of ONU200. ONU200 generates a Report frame including the amount of data obtained by the subtraction. Thus, there is a difference between ONU100 and ONU200.

[0030] Returning to the explanation of the ONU 100, the processing executed by the ONU 100 will be specifically explained below. The ONU 100 receives from the OSU 310 a Normal Gate frame including a transmission start time GST1(n), a transmission time GL1(n), a transmission start time GST2(n), and a transmission time GL2(n)_a.

[0031] ONU100 transmits a Report frame to OSU310 from transmission start time GST1(n) to transmission time GL1(n). ONU100 changes transmission time GL2(n)_a to transmission time GL2(n)_b. ONU100 transmits a Data frame to OSU310 from transmission start time GST2(n) to transmission time GL2(n)_b.

[0032] In the following description, the transmission time GL2(n)_a may be considered as the transmission time GL(n)_a. The transmission time GL2(n)_b may be considered as the transmission time GL(n)_b. The transmission time GL(n)_b is calculated using the following formula (1). Note that c indicates the transmission preparation time.

[0033]

number

[0034] The transmission preparation time c is calculated using the following equation (2). Here, d is the actual measurement time. For example, actual measurement time d is the time from checking the amount of data in memory 110 before receiving a Normal Gate frame including transmission start time GST1(n) to generating a Report frame that was transmitted before receiving a Normal Gate frame including transmission start time GST1(n). In other words, actual measurement time d is the time from checking the amount of data in memory 110 to generate the previously transmitted Report frame (i.e., the Report frame transmitted at transmission start time GST1(n)).

[0035] e is an offset. For example, the offset e is stored in the storage unit 110. For example, the offset e is a preset fixed value. Also, for example, the offset e is the difference between the amount of data transmitted from the transmission start time GST2(n) before transmitting the Data frame and the amount of data scheduled to be transmitted this time. The offset e may also be the difference between the amount of data transmitted last time and the amount of data scheduled to be transmitted this time. The reason for adding the offset e to the transmission preparation time c is to provide some leeway in the transmission preparation time.

[0036]

number

[0037] If the specifications of the PON system require that a minimum amount of data transmission be guaranteed, a lower limit may be set for the transmission time GL(n)_b. The transmission preparation time c tends to be longer as the transmission time GL(n)_a is longer. Therefore, Fig. 4(A) shows that the transmission preparation time c is long.

[0038] 4A, the shortened transmission time of the Data frame allows the ONU 100 to secure the transmission preparation time c. The ONU 100 prepares to transmit the Report frame to the OSU 310 during the transmission preparation time c.

[0039] Furthermore, during DBA_cycle(n), ONU100 receives a Normal Gate frame including transmission start time GST1(n+1), transmission time GL1(n+1), transmission start time GST2(n+1), and transmission time GL2(n+1) from OSU310. ONU100 transmits a Report frame generated during transmission preparation time c at transmission start time GST1(n+1).

[0040] Figure 4(B) shows a case where a PON system includes multiple ONUs, including ONU 100. "R" in Figure 4(B) indicates a Report frame. "D" in Figure 4(B) indicates a Data frame.

[0041] As in Figure 4(A), the transmission time of the Data frame becomes shorter. When the number of ONUs included in the PON system is large, the transmission time allocated to each ONU (for example, transmission time GL(n)_a) becomes shorter. Figure 4(B) shows that the transmission preparation time c is short. The shorter the transmission time (for example, transmission time GL(n)_a), the shorter the transmission preparation time c tends to become. Here, when the transmission preparation time c is long, the time to transmit the Data frame becomes shorter, and the communication utilization efficiency (in other words, bandwidth utilization efficiency) decreases. When the transmission preparation time c is short, the decrease in communication utilization efficiency can be minimized compared to when the transmission preparation time c is long.

[0042] The bandwidth used in a PON system changes dynamically depending on the number of ONUs and the usage status of the communication bandwidth. As the bandwidth changes, the transmission preparation time c can change dynamically.

[0043] 4, since the transmission preparation time c is secured, the OSU 310 can communicate with the ONU 100. Furthermore, communication by the ONU 100 improves the bandwidth utilization efficiency of the PON system.

[0044] Next, the processing executed by the ONU 100 will be explained using a flowchart. FIG. 5 is a flowchart illustrating an example of a process executed by the ONU according to the first embodiment. (Step S11) The control unit 130 sets the maximum possible transmission preparation time as the initial value to the actual measurement time d. The reason for setting the initial value to the actual measurement time d is that the actual measurement time d is not measured in the initial state. The reason for setting the maximum value is to ensure that the transmission preparation time is secured. The control unit 130 stores the actual measurement time d in the storage unit 110.

[0045] (Step S12) The communication unit 120 receives a Normal Gate frame from the OLT 300 (specifically, the OSU 310) that includes the transmission start time and transmission time of the Report frame, the transmission start time GST(n) of the Data frame, and the transmission time GL(n)_a of the Data frame. Here, the transmission start time GST(n) is also referred to as the first transmission start time, and the transmission time GL(n)_a is also referred to as the first transmission time.

[0046] (Step S13) The communication unit 120 transmits the Report frame to the OLT 300 (specifically, the OSU 310) from the transmission start time of the Report frame until the transmission time of the Report frame. (Step S14) The control unit 130 calculates the transmission preparation time c by adding the actual measurement time d and the offset e.

[0047] (Step S15) The control unit 130 calculates the transmission time GL(n)_b using the transmission time GL(n)_a, the transmission preparation time c, and the formula (1). Here, the transmission time GL(n)_b is also referred to as the second transmission time.

[0048] (Step S16) The communication unit 120 receives a Normal Gate frame including the transmission start time of the Report frame, the transmission duration of the Report frame, the transmission start time of the Data frame, and the transmission duration of the Data frame from the OSU 310. For example, the transmission start time of the Report frame may be considered to be the transmission start time GST1(n+1) in FIG. 4(A).

[0049] (Step S17) The communication unit 120 transmits a Data frame based on the data stored in the storage unit 110 to the OLT 300 (specifically, the OSU 310) during the transmission time GL(n) from the transmission start time GST(n) to the transmission time GL(n)_b.

[0050] (Step S18) The control unit 130 checks the amount of data in the memory unit 110. The control unit 130 generates a Report frame including the checked amount of data. Alternatively, the control unit 130 may generate the Report frame by the following process. Based on the amount of data in the memory unit 110, the control unit 130 calculates the amount of data that the control unit 130 wants to transmit to the OSU 310. The control unit 130 generates a Report frame including the calculated amount of data. The control unit 130 sets the actual measurement time d to the time from when the amount of data in the storage unit 110 is confirmed until the Report frame is generated. That is, the control unit 130 updates the actual measurement time d.

[0051] Then, the process proceeds to step S13. The Report frame is transmitted at the transmission start time of the Report frame included in the Normal Gate frame received in step S16.

[0052] The Normal Gate frame received in step S16 may be received between steps S13 and S17. Furthermore, the transmission start time and transmission duration of the Data frame contained in the Normal Gate frame received in step S16 may be considered to be the transmission start time GST(n) and transmission duration GL(n)_a of the Data frame in step S17, which is executed after step S18.

[0053] In equation (2), the transmission preparation time c is calculated by adding the actual measurement time d and the offset e. However, when calculating the transmission preparation time c, it is not necessary to add the offset e. In other words, the actual measurement time d may be the transmission preparation time c.

[0054] According to the first embodiment, the ONU 100 shortens the transmission time of a Data frame to ensure sufficient transmission preparation time. Because the ONU 100 shortens the transmission time, the OSU 310 does not need to determine the transmission start time for the ONU 100, taking the transmission preparation time into consideration. Therefore, the OSU 310 does not need to distinguish between the ONU 100 and the ONU 200 when determining the transmission start time. Furthermore, the first embodiment can be realized by developing only the ONU 100, so extensive development is not required. Furthermore, because the first embodiment is realized by processing by the ONU 100, the OSU 310 does not need to have a function for performing complex management. In this way, even in a PON system in which ONUs 100 and 200 coexist, OSU 310 can communicate with both ONUs 100 and 200 without any problems.

[0055] Embodiment 2 Next, a second embodiment will be described. In the second embodiment, differences from the first embodiment will be mainly described. In the second embodiment, descriptions of commonalities with the first embodiment will be omitted. In the second embodiment, reference will be made to FIGS. 1 to 4.

[0056] In the first embodiment, a case has been described in which the transmission time included in a Normal Gate frame is changed every time. In the second embodiment, a case will be described in which the transmission time is changed only when necessary.

[0057] Fig. 6 is a block diagram showing the functions of the ONU according to embodiment 2. The components in Fig. 6 that are the same as those shown in Fig. 3 are assigned the same reference numerals as those shown in Fig. 3. The ONU 100a includes a control unit 130a, the function of which will be described in detail later.

[0058] Next, the process executed by the ONU 100a will be explained using a flowchart. FIG. 7 is a flowchart illustrating an example of processing executed by the ONU according to the second embodiment. (Step S21) The control unit 130a sets the maximum possible transmission preparation time as the initial value for the actual measurement time d. The control unit 130a stores the actual measurement time d in the storage unit 110. (Step S22) The communication unit 120 receives from the OSU 310 a Normal Gate frame including the Report frame transmission start time, the Report frame transmission duration, the Data frame transmission start time GST(n), and the Data frame transmission duration GL(n)_a.

[0059] (Step S23) The communication unit 120 transmits the Report frame to the OSU 310 from the transmission start time of the Report frame to the transmission time of the Report frame. (Step S24) The control unit 130a calculates the transmission preparation time c by adding the actual measurement time d and the offset e.

[0060] (Step S25) The communication unit 120 receives a Normal Gate frame from the OSU 310, which includes the transmission start time of the Report frame, the transmission duration of the Report frame, the transmission start time of the Data frame, and the transmission duration of the Data frame. The transmission start time of the Report frame is the transmission start time of the Report frame that is transmitted after the transmission of the Data frame in step S27 or step S29 is completed. The transmission start time of the Report frame is called the transmission start time GST(n+1) or the second transmission start time.

[0061] (Step S26) The control unit 130a determines whether the value calculated by "GST(n+1)-(GST(n)+GL(n)_a)" is equal to or greater than the transmission preparation time c. In this calculation, the transmission start time is converted as follows. For example, if the transmission start time is "10:00", the transmission start time is converted to "1000". If the condition is met, the transmission preparation time is secured, so the process proceeds to step S27. If the condition is not met, the process proceeds to step S28.

[0062] (Step S27) The communication unit 120 transmits a Data frame to the OSU 310 from the transmission start time GST(n) to the transmission time GL(n)_a. Then, the process proceeds to step S30. (Step S28) The control unit 130a calculates the transmission time GL(n)_b using the transmission time GL(n)_a, the transmission preparation time c, and the formula (1). (Step S29) The communication unit 120 transmits a Data frame to the OSU 310 from the transmission start time GST(n) to the transmission time GL(n)_b.

[0063] (Step S30) The control unit 130a checks the amount of data in the storage unit 110. The control unit 130a generates a Report frame including the checked amount of data. The control unit 130a sets the time from when the amount of data in the storage unit 110 is checked to when the Report frame is generated as the actual measurement time d. That is, the control unit 130a updates the actual measurement time d. Then, the process proceeds to step S23. The Report frame is transmitted at the transmission start time of the Report frame included in the Normal Gate frame received in step S25.

[0064] Also, the Normal Gate frame received in step S25 may be received before step S24.

[0065] Furthermore, the transmission start time and transmission duration of the Data frame contained in the Normal Gate frame received in step S25 may be considered to be the transmission start time GST(n) and transmission duration GL(n)_a of the Data frame used in the processing in step S26 executed after step S30.

[0066] According to the second embodiment, the OSU 310 does not need to determine the transmission start time for the ONU 100a, taking into account the transmission preparation time. Therefore, the OSU 310 can communicate with the ONU 100a. Furthermore, the ONU 100a changes the transmission time only when necessary. This improves the bandwidth utilization efficiency of the PON system.

[0067] Embodiment 3 Next, a third embodiment will be described. In the third embodiment, differences from the first embodiment will be mainly described. In the third embodiment, descriptions of commonalities with the first embodiment will be omitted. In the third embodiment, reference will be made to FIGS. 1 to 4. In the third embodiment, the method of calculating the transmission preparation time differs from the method of calculating the transmission preparation time in the first embodiment. The third embodiment will be described in detail below.

[0068] 8 is a block diagram showing the functions of an ONU according to embodiment 3. The components in FIG. 8 that are the same as those shown in FIG. 3 are assigned the same reference numerals as those shown in FIG. The ONU 100b includes a control unit 130b, the function of which will be described in detail later.

[0069] For example, the timing chart showing the operation of ONU 100b in the third embodiment is the same as the timing chart shown in Fig. 4(A). The method of calculating the transmission time GL(n)_b in the first embodiment is different from the method of calculating the transmission time GL(n)_b in the third embodiment. Therefore, the method of calculating the transmission time GL(n)_b will be described. The ONU 100b calculates the transmission time GL(n)_b using the following equation (3).

[0070]

number

[0071] The transmission preparation time c is calculated using the following equation (4). Note that f is the number of Data frames generated based on the amount of data scheduled to be transmitted this time. g is the transmission time per Data frame. Information on the transmission time g is stored in the storage unit 110, for example.

[0072]

number

[0073] For example, the ONU 100b calculates the number of Data frames f based on the transmission time GL(n)_a and the transmission time g. Furthermore, for example, ONU 100b may calculate the number of Data frames f using the following equation (5). Here, h is the processing time required on the transmission path. For example, the processing time h is SyncTime, Laser_ON / OFF, etc. i is information related to one Data frame. For example, the information i is InterFrameGap, the header length of the Data frame, etc. j is the shortest frame length in the PON system.

[0074]

number

[0075] In equation (5), the shortest frame length j is used. The reason for using the shortest frame length j is as follows. The transmission preparation time c is calculated based on the number of Data frames f. The greater the number of Data frames f, the longer the transmission preparation time c. The case where the transmission preparation time c is the longest (i.e., when the limit of the transmission preparation time c is taken into consideration) is when the number of Data frames for the shortest frame length j is the greatest. For this reason, in equation (5), the shortest frame length j is used. And, by using the shortest frame length j, the possibility of insufficient transmission preparation time c can be reduced.

[0076] Note that equations (4) and (5) are examples where the transmission preparation time c depends on the number of Data frames f. If the transmission preparation time c varies due to other factors, ONU 100b may calculate the transmission preparation time c using a different equation. For example, the other factors may be a processing circuit. For example, equations (4) and (5) may be modified as appropriate to take the other factors into consideration.

[0077] Next, the process executed by the ONU 100b will be explained using a flowchart. FIG. 9 is a flowchart illustrating an example of processing executed by the ONU according to the third embodiment. (Step S31) The communication unit 120 receives from the OSU 310 a Normal Gate frame including the transmission start time of the Report frame, the transmission duration of the Report frame, the transmission start time GST(n) of the Data frame, and the transmission duration GL(n)_a of the Data frame.

[0078] (Step S32) The communication unit 120 transmits the Report frame to the OSU 310 from the transmission start time of the Report frame to the transmission time of the Report frame. (Step S33) The control unit 130b calculates the number of Data frames f. For example, the control unit 130b calculates the number of Data frames f using equation (5). (Step S34) The control unit 130b calculates the transmission preparation time c using the number of Data frames f, the transmission time g, and equation (4).

[0079] (Step S35) The communication unit 120 receives a Normal Gate frame including the transmission start time of the Report frame, the transmission duration of the Report frame, the transmission start time of the Data frame, and the transmission duration of the Data frame from the OSU 310. The transmission start time of the Report frame is called the transmission start time GST(n+1) or the second transmission start time.

[0080] (Step S36) The control unit 130b determines whether the value calculated by "GST(n+1)-(GST(n)+GL(n)_a)" is equal to or greater than the transmission preparation time c. If the condition is met, the transmission preparation time is secured, so the process proceeds to step S37. If the condition is not met, the process proceeds to step S38.

[0081] (Step S37) The communication unit 120 transmits a Data frame to the OSU 310 from the transmission start time GST(n) to the transmission time GL(n)_a. The control unit 130b generates a Report frame, which is transmitted at the transmission start time of the Report frame included in the Normal Gate frame received in step S35. Then, the process proceeds to step S32.

[0082] (Step S38) The control unit 130b calculates the transmission time GL(n)_b using the transmission time GL(n)_a, the transmission preparation time c, and equation (3). (Step S39) The communication unit 120 transmits a Data frame to the OSU 310 from the transmission start time GST(n) to the transmission time GL(n)_b. The control unit 130b generates a Report frame, which is transmitted at the transmission start time of the Report frame included in the Normal Gate frame received in step S35. Then, the process proceeds to step S32.

[0083] The Normal Gate frame received in step S35 may be received between steps S33 and S35.

[0084] Furthermore, the transmission start time and transmission duration of the Data frame contained in the Normal Gate frame received in step S35 may be considered to be the transmission start time GST(n) and transmission duration GL(n)_a of the Data frame used in the processing in step S36 executed after step S37 or step S39.

[0085] According to the third embodiment, the OSU 310 does not need to determine the transmission start time taking into account the transmission preparation time for the ONU 100b, and therefore the OSU 310 can communicate with the ONU 100b. Furthermore, if the transmission preparation time is secured, the ONU 100b does not change the transmission time, thereby preventing a decrease in bandwidth utilization efficiency in the PON system.

[0086] Embodiment 4 Next, a fourth embodiment will be described. In the fourth embodiment, differences from the first embodiment will be mainly described. In the fourth embodiment, descriptions of commonalities with the first embodiment will be omitted. In the fourth embodiment, reference will be made to FIGS. 1 to 3. In the first embodiment, a case has been described in which the transmission time included in a Normal Gate frame is changed every time. In the fourth embodiment, a case will be described in which the transmission time is changed only when necessary using a threshold value.

[0087] Fig. 10 is a block diagram showing the functions of an ONU according to embodiment 4. The components in Fig. 10 that are the same as those shown in Fig. 3 are assigned the same reference numerals as those shown in Fig. 3. The ONU 100c includes a control unit 130c. The control unit 130c acquires a threshold value. For example, the control unit 130c acquires the threshold value from the storage unit 110. Alternatively, for example, the control unit 130c acquires the threshold value from an external device connectable to the ONU 100c. Note that the threshold value is, for example, a value obtained by subtracting the maximum transmission preparation time that can be taken based on the performance of the ONU 100c from the maximum possible transmission time included in a Normal Gate frame in the PON system.

[0088] If the transmission time of the Data frame is equal to or greater than the threshold, the control unit 130c changes the transmission time to a transmission time that is shorter than the threshold. For example, the control unit 130c changes the transmission time to a transmission time that is the same as the threshold.

[0089] Next, a timing chart in the PON system will be described. 11A and 11B are diagrams showing examples of timing charts according to the fourth embodiment. Fig. 11A shows a case where one ONU 100c is included in a PON system.

[0090] The ONU 100c receives a Normal Gate frame including a transmission start time GST2(n) and a transmission time GL2(n)_a from the OSU 310. The transmission time GL2(n)_a is equal to or greater than a threshold. Therefore, the ONU 100c changes the transmission time GL2(n)_a to a transmission time GL2(n)_b. The ONU 100c then transmits a Data frame to the OSU 310 from the transmission start time GST2 to the transmission time GL2(n)_b. Note that an upper limit may be set for the threshold.

[0091] Figure 11(B) shows a case where a PON system includes multiple ONUs, including ONU 100c. "R" in Figure 11(B) indicates a Report frame. "D" in Figure 11(B) indicates a Data frame.

[0092] The ONU 100c receives a Normal Gate frame including a transmission start time GST2(n) and a transmission time GL2(n)_a from the OSU 310. The transmission time GL2(n)_a is smaller than a threshold. If the transmission time GL2(n)_a is smaller than the threshold, the transmission preparation time is secured. Therefore, the ONU 100c does not change the transmission time GL2(n)_a. The ONU 100c transmits a Data frame to the OSU 310 from the transmission start time GST2 to the transmission time GL2(n)_a.

[0093] Next, the process executed by the ONU 100c will be explained using a flowchart. FIG. 12 is a flowchart illustrating an example of processing executed by the ONU according to the fourth embodiment. (Step S41) The control unit 130c stores the threshold value transmitted by the OSU 310 in the storage unit 110. (Step S42) The communication unit 120 receives from the OSU 310 a Normal Gate frame including the Report frame transmission start time, the Report frame transmission duration, the Data frame transmission start time GST(n), and the Data frame transmission duration GL(n)_a. (Step S43) The communication unit 120 transmits the Report frame to the OSU 310 from the transmission start time of the Report frame to the transmission time of the Report frame.

[0094] (Step S44) The communication unit 120 receives from the OSU 310 a Normal Gate frame including the transmission start time of the Report frame, the transmission duration of the Report frame, the transmission start time of the Data frame, and the transmission duration of the Data frame.

[0095] (Step S45) The control unit 130c acquires the threshold value from the storage unit 110. The control unit 130c compares the transmission time GL(n)_a with the threshold value. (Step S46) The control unit 130c determines whether the transmission time GL(n)_a is smaller than the threshold. If the transmission time GL(n)_a is smaller than the threshold, the process proceeds to step S47. If the transmission time GL(n)_a is equal to or greater than the threshold, the process proceeds to step S48.

[0096] (Step S47) The communication unit 120 transmits a Data frame to the OSU 310 from the transmission start time GST(n) to the transmission time GL(n)_a. The control unit 130c generates a Report frame, which is transmitted at the transmission start time of the Report frame included in the Normal Gate frame received in step S44. Then, the process proceeds to step S43.

[0097] (Step S48) The control unit 130c changes the transmission time GL2(n)_a to the transmission time GL2(n)_b, which is the same value as the threshold value. (Step S49) The communication unit 120 transmits a Data frame to the OSU 310 from the transmission start time GST(n) to the transmission time GL(n)_b. The control unit 130c generates a Report frame, which is transmitted at the transmission start time of the Report frame included in the Normal Gate frame received in step S44. Then, the process proceeds to step S43.

[0098] Furthermore, the transmission start time and transmission duration of the Data frame contained in the Normal Gate frame received in step S44 may be considered to be the transmission start time GST(n) and transmission duration GL(n)_a of the Data frame after step S47 or step S49.

[0099] When changing the transmission time GL2(n)_a to the transmission time GL2(n)_b, the control unit 130c may change the transmission time GL2(n)_a to the transmission time GL2(n)_b using equations (1) and (2) in embodiment 1 or equations (3) and (4) in embodiment 3.

[0100] According to the fourth embodiment, the OSU 310 does not need to determine the transmission start time taking into account the transmission preparation time for the ONU 100c, and therefore the OSU 310 can communicate with the ONU 100c. Furthermore, the ONU 100c does not change the transmission time if the transmission preparation time is secured, which prevents a decrease in bandwidth utilization efficiency in the PON system.

[0101] The features of the above-described embodiments can be combined with each other as appropriate. [Explanation of symbols]

[0102] 100,100_1,···,100_n ONUs, 101 processor, 102 volatile storage device, 103 non-volatile storage device, 110 storage unit, 120 communication unit, 130,130a,130b,130c control unit, 140 UNI function unit, 200,200_1,···,200_n ONUs, 300 OLTs, 310,310_1,...,310_n OSUs, 400_1,···,400_n optical splitters.

Claims

1. An optical communication device is included in an optical communication system including a master station device and a slave station device that does not prepare to transmit first information to the master station device, the first information being information used by the master station device to determine data transmission timing for the slave station device, between completion of transmission of a data frame and before transmission of the first information, the slave station device making the preparation between completion of transmission of the data frame and before transmission of the first information, a storage unit for storing data; a communication unit that receives second information including a first transmission start time and a first transmission duration from the master station; a control unit that changes the first transmission time to a second transmission time that is shorter than the first transmission time in order to ensure time for the preparation; and when the communication unit receives the second information, the communication unit transmits a data frame based on the data to the master station device during the second transmission time period from the first transmission start time; Optical communication equipment.

2. the control unit calculates the second transmission time based on a transmission preparation time including an actual measurement time that is a time from checking the amount of data in the storage unit before receiving the second information to generating the first information that is transmitted before receiving the second information, and the first transmission time.

2. The optical communication device according to claim 1.

3. the transmission preparation time is a preset fixed value or a value calculated based on the difference between the amount of data transmitted before transmitting a data frame based on the data and the amount of data scheduled to be transmitted this time, and the actual measurement time.

3. The optical communication device according to claim 2.

4. the communication unit receives a second transmission start time that is a transmission start time of the first information to be transmitted after completion of transmission of a data frame based on the data; the control unit changes the first transmission time to the second transmission time when a value calculated based on the second transmission start time, the first transmission start time, and the first transmission time is smaller than the transmission preparation time.

4. The optical communication device according to claim 2 or 3.

5. when a value calculated based on the second transmission start time, the first transmission start time, and the first transmission time is equal to or longer than the transmission preparation time, the communication unit transmits a data frame based on the data to the master station device during a period from the first transmission start time to the first transmission time; 5. The optical communication device according to claim 4.

6. the control unit acquires a threshold value, and when the first transmission time is equal to or greater than the threshold value, changes the first transmission time to the second transmission time; 2. The optical communication device according to claim 1.

7. When the first transmission time is shorter than the threshold, the communication unit transmits a data frame based on the data to the master station device during the first transmission time from the first transmission start time.

7. The optical communication device according to claim 6.

8. the first information is a Report frame, the second information is a Normal Gate frame; The optical communication device according to any one of claims 1 to 7.

9. The present invention is included in an optical communication system including a master station device and a slave station device that does not prepare to transmit first information to the master station device, the first information being used by the master station device to determine data transmission timing for the slave station device, between the completion of transmission of a data frame and the transmission of the first information, and the optical communication device that is a slave station device that makes the preparation between the completion of transmission of the data frame and the transmission of the first information, receiving second information including a first transmission start time and a first transmission duration from the master station device; changing the first transmission time to a second transmission time that is shorter than the first transmission time in order to ensure time for making the preparations; When the second information is received, a data frame based on the data stored in the storage unit is transmitted to the master station device during the second transmission time period from the first transmission start time. Control method.

10. The present invention is included in an optical communication system including a master station device and a slave station device that does not prepare to transmit to the master station device first information, which is information used when the master station device determines a data transmission timing for a slave station device, between the completion of transmission of a data frame and the transmission of the first information, and the optical communication device that is a slave station device that makes the preparation between the completion of transmission of the data frame and the transmission of the first information, receiving second information including a first transmission start time and a first transmission duration from the master station device; changing the first transmission time to a second transmission time that is shorter than the first transmission time in order to ensure time for making the preparations; When the second information is received, a data frame based on the data stored in the storage unit is transmitted to the master station device during the second transmission time period from the first transmission start time. A control program that executes processing.

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