JP2021132297A - Control apparatus, and control program - Google Patents

Abstract

To provide a control apparatus capable of reducing a time from out-of-frame-synchronism to frame synchronism establishment with a station-side termination device after switching in the case where wavelength switching occurs in a transmission wavelength used for a communication between the station-side termination device and a subscriber-side termination device, and a control program.SOLUTION: A control apparatus includes: a processing unit which processes a frame exchanged with a station-side termination device; a holding unit which holds a first frame counter value indicating a wavelength switching time; a reading unit which reads a second frame counter value indicating a wavelength switching implementation time reported from the station-side termination device included in the frame processed by the processing unit in a synchronous state; a determination unit which determines whether or not the first frame counter value held by the holding unit and the second frame counter value read by the reading unit are coincident when the wavelength switching implementation time is reported from the station-side termination device; and a state control unit which shifts a state of a subscriber-side termination device from the synchronous state to a hunt state in the case where the determination is an affirmative determination.SELECTED DRAWING: Figure 2

Description

In recent years, a service called FTTH (Fiber To The Home) using an optical fiber for a transmission line has become widespread for the purpose of providing a high-speed and wide-band broadband service to general private homes. For the provision of broadband services by FTTH, an optical access network called a passive optical network (PON) is often used.

One PON is an optical network unit (OLT) and a plurality of optical network units (ONUs) using an optical passive element called an optical splitter (optical coupler). It is configured by connecting one-to-many by branching the optical cable of. In PON, the FTTH service can be economically provided by sharing an optical fiber, an OLT, or the like with a plurality of subscribers.

There is a PON called XGS-PON (10-Gigabit-capable passive passive optical network) (Non-Patent Document 1). In XGS-PON, TDMA (Time Division Multiplex Access) technology is used for communication (uplink communication) from ONU to OLT to avoid signal collision from each ONU. A PON that uses this TDMA technology is also called a TDM-PON.

Furthermore, in order to meet the increasing communication demand in future optical access networks, there is a PON called NG-PON2 (40-Gigabit-capable symmetrical passive network) as a next-generation PON whose transmission rate exceeds 10-Gigabit (40-Gigabit-capable passive optical network). Non-patent document 2). Among NG-PON2, a plurality of TDM-PONs are constructed on one PON infrastructure by WDM (Wavelength Division Multiplexing) technology. Are better.

FIG. 8A shows the basic configuration of the TWDM-PON system. As shown in FIG. 8 (a), in the TWDM-PON system, a plurality of NG-PON2 OLT20-1, OLT20-2 ... The wavelength division multiplexing / separating device 30 for wavelength division multiplexing / separation includes a plurality of NG-PON2 ONU10-1, 10-2, ... 10-m (hereinafter, collectively referred to as "ONU10", an optical coupler 31, an optical fiber 32). For uplink communication (communication in the direction from ONU10 to OLT20), the reception wavelength of the optical transmitter / receiver of each OLT20 is fixedly assigned so that the reception wavelengths of the OLT20s do not overlap. In this case, by changing the transmission wavelength of the optical transmitter / receiver of the ONU 10, the uplink connection of the ONU 10 to the OLT 20 can be dynamically switched. Further, the downlink communication (communication in the direction from the OLT 20 to the ONU 10) is also uplink. Similar to communication, the transmission wavelength of the optical transmitter / receiver of each OLT20 is fixedly assigned, and the reception wavelength of the optical transmitter / receiver of the ONU10 is changed, so that the downlink connection between the OLT20 and the ONU10 can be dynamically switched.

On the other hand, when the wavelength of the wavelength that connects the ONU 10 and the OLT20 is switched, a temporary communication interruption occurs. Therefore, in order to reduce data loss and communication delay due to the switching, it is desired that the switching can be performed in the shortest possible time. ..

By the way, in TWDM-PON, prior to the start of communication between the OLT20 and the ONU10, the ONU10 first receives the downlink signal transmitted from the OLT20, detects the frame synchronization pattern in the downlink signal, and performs frame synchronization. Need to be established. As a method of establishing this frame synchronization, there is a method shown in Non-Patent Document 3. Hereinafter, a conventional frame synchronization method based on Non-Patent Document 3 will be described with reference to FIGS. 8 (b) and 9.

FIG. 8B shows an example of the frame configuration. In the downlink signal from the OLT20, the PHY frame shown in FIG. 8B is repeatedly transmitted every 125 μs (microseconds). The first 24 bytes of the PHY frame are an area called PSBd. PSBd is composed of PSsync, SFC (Superframe counter) structure, and OC structure regions, of which PSsync is an 8-byte frame synchronization pattern. On the other hand, the SFC structure is composed of a 51-bit Superframe counter and a 13-bit HEC (Hybrid Error Control), and HEC performs error-correctable coding up to 1 bit. Further, the Superframe counter is added by 1 for each PHY frame of 125 μsec, and is transmitted from the OLT20 to the ONU10. The ONU 10 holds the Superframe counter in a locally provided counter each time it receives the Superframe counter. By the above operation, the ONU 10 can be synchronized with the OLT 20 in time. The ONU 10 also uses the PSsync and SFC structure described above to establish frame synchronization with the OLT20. The "Superframe counter" is an example of the "frame counter" according to the present invention.

FIG. 9 shows a state transition diagram of the ONU 10 for establishing frame synchronization. Initially, the state of ONU10 in which frame synchronization has not been established is the hunt state shown in FIG. In the hunt state, the two signal states of Exact_PSlink and SFC_usable are monitored. Exact_PSsync is a signal that becomes true when a position where all 64 bits are the same is detected by comparing with the frame synchronization pattern while shifting the downlink signal by 1 bit, and becomes false otherwise. Further, the detected 64 bits are determined to be the PSsync region. SFC_usable is a signal that determines that the 64 bits after the PSsync region are the SFC structure region and performs HEC calculation on the SFC structure region, and if there is no error or error correction is possible, the signal becomes true, and the other signals become false.

In the hunt state, when Exact_PSSync is true and SFC_usable is true, the ONU 10 transitions to the pre-synchronous state. At this time, the ONU 10 holds the super frame counter value locally, that is, the super frame counter value is stored in a storage unit or the like (not shown by the ONU 10).

In the pre-synchronization state, the two signal states of PSync_Det and SFC_Val are monitored. PSsync_Det determines that 64 bits 125 μs after the position determined to be the PSsync region last time is the next PSsync region, compares the 64 bits with the frame synchronization pattern, and if 62 to 64 bits match, true, otherwise false. It is a signal that becomes. SFC_Val determines that the 64 bits after the PSsync area are the SFC structure area, and as a result of HEC calculation of the SFC structure area, there is no error or error correction is possible, and 1 is added to the locally held superframe counter value. It is a signal that becomes true when the value obtained and the SFC structure value in the SFC structure region are the same, and false otherwise.

In the pre-synchronization state, the ONU 10 transitions to the synchronization (Sync) state when PSsync_Det is true and SFC_Val is true. At this time, the superframe counter value is held locally. In other cases, it transitions to the hunt state.

The synchronization state is a state in which frame synchronization can be normally established in the ONU 10. In the synchronous state, the two signal states of PSync_Det and SFC_Val are monitored. In the synchronous state, the ONU 10 transitions to the synchronous state when PSync_Det is true and SFC_Val is true. At this time, the superframe counter value is held locally. In other cases, the state transitions to the synchronous protection (Re-Sync) state.
At this time, the synchronous protection state continuation counter is set to 1. The synchronous protection state continuation counter is a counter for counting how many times the transition to the synchronous protection state has been performed, and is represented by a variable M in the present embodiment. The recommended value of M in the standard is 3, and it is set to 3 as an example in this embodiment.

In the synchronous protection state, the three signal states of PSync_Det, SFC_Val, and Considentive_Chk are monitored. Consident_Chk is a signal that becomes true when the synchronous protection state continuation counter value is M-1 (that is, 2 in the present embodiment) or more, and false otherwise. The ONU 10 transitions to the synchronous state when PSsync_Det is true and SFC_Val is true in the synchronous protection state. At this time, the superframe counter value is held locally. In other cases, that is, when PSync_Det is false or SFC_Val is false, 1 is added to the synchronous protection state continuation counter value to transition to the synchronous protection state. Further, when Constubive_Chk is true, the state transitions to the hunt state.

Next, the frame synchronization process according to the prior art will be described with reference to FIGS. 10 to 13. 10 to 13 are flowcharts showing the flow of frame synchronization processing according to the prior art, and are views in which the state transition diagram shown in FIG. 9 is modified into a flowchart.

The transition from the hunt state to the pre-synchronization state will be described with reference to FIG.

In step S600, 64 bits are extracted from the frame of the downlink signal.

In step S601, the 64-bit extracted in step S600 is compared with the frame synchronization pattern (that is, PSsync in the PSBd region). If all the bits match in the comparison, the process proceeds to step S602, and if even one bit does not match, the process proceeds to step S606.

In step 602, the extraction position is shifted by 64 bits, and in step S603, 64 bits are extracted from the downlink signal and the HEC operation is executed. That is, the SFC structure is extracted from the downlink signal, and the HEC operation is executed on the extracted SFC structure.

In step S604, the HEC calculation result is determined. If there is no error in the determination or the error can be corrected, the process proceeds to step S605, the value of SFC (Superframe counter) is extracted from the HEC calculation result, and the value is held locally. After that, it transitions to the pre-synchronization state.

On the other hand, in step S606, the extraction position is shifted by 1 bit, and then the process returns to step S600 to continue the 64-bit extraction.

If the result of the determination in step S604 is uncorrectable, the process proceeds to step S607 to return the extraction position by 63 bits, and then returns to step S600 to continue extraction of 64 bits.

Next, the transition from the pre-synchronization state to the synchronization state or the hunt state will be described with reference to FIG.

In step S700, the position 125 μs after the previous synchronization pattern detection position is set as the extraction position.

In step S701, 64 bits are extracted from the frame of the downlink signal.

In step S702, the frame synchronization pattern is compared with the 64-bit extracted in step S701. If 62 to 64 bits match in the comparison, the process proceeds to step S703. On the other hand, if 3 bits or more do not match in the comparison, the transition to the hunt state occurs.

In step S703, the extraction bit is shifted by 64 bits, and in the following step S704, 64 bits are extracted from the downlink signal and the HEC operation is executed. That is, the SFC structure is extracted from the downlink signal, and the HEC operation is executed on the extracted SFC structure.

In step S705, the HEC calculation result is determined. If there is no error in the determination or the error can be corrected, the process proceeds to step S706, and if the error cannot be corrected, the process proceeds to the hunt state.

In step S706, the value of SFC (Superframe counter) is extracted from the HEC calculation result.

In step S707, the SFC value extracted in step S706 is compared with the SFC value obtained by adding 1 to the locally held SFC value. If the results of the comparison match, the process proceeds to step S708 to locally retain the extracted SFC value, and then the process proceeds to the synchronous state. On the other hand, if the comparison results in step S707 do not match, the state transitions to the hunt state.

Next, the transition from the synchronous state to the synchronous protection state will be described with reference to FIG.

In step S800, the position 125 μs after the previous synchronization pattern detection position is set as the extraction position.

In step S801, 64 bits are extracted from the frame of the downlink signal.

In step S802, the 64-bit extracted in step S801 is compared with the frame synchronization pattern. If 62 to 64 bits match in the comparison, the process proceeds to step S803. On the other hand, if 3 bits or more do not match in the comparison, the process proceeds to step S809.

In step S803, the extraction bit is shifted by 64 bits, and in the following step S804, 64 bits are extracted from the downlink signal and the HEC operation is executed. That is, the SFC structure is extracted from the downlink signal, and the HEC operation is executed on the extracted SFC structure.

In step S805, the HEC calculation result is determined. If there is no error in the determination or the error can be corrected, the process proceeds to step S806, and if the error correction is not possible, the process proceeds to step S809.

In step S806, the value of SFC (Superframe counter) is extracted from the HEC calculation result.

In step S807, the SFC value extracted in step S806 is compared with the SFC value obtained by adding 1 to the locally held SFC value. If the results of the comparison match, the process proceeds to step S808, the extracted SFC value is held locally, and then the process returns to step S800. That is, the synchronization state is continued. On the other hand, if the comparison results in step S807 do not match, the process proceeds to step S809.

On the other hand, in step S809, 1 is added to the locally held SFC value, and in the following step S810, the counter value of the synchronous protection state continuation counter (denoted as “synchronous protection counter” in FIG. 12) is initially set to 1. And then transition to the synchronous protection state.

Next, the transition from the synchronous protection state to the synchronous state or the hunt state will be described with reference to FIG.

In step S900, the position 125 μs after the previous synchronization pattern detection position is set as the extraction position.

In step S901, 64 bits are extracted from the frame of the downlink signal.

In step S902, the 64-bit extracted in step S901 is compared with the frame synchronization pattern. If 62 to 64 bits match in the comparison, the process proceeds to step S903. On the other hand, if 3 bits or more do not match in the comparison, the process proceeds to step S909.

In step S903, the extraction bits are shifted by 64 bits, and in the following step S904, 64 bits are extracted from the downlink signal and the HEC operation is executed. That is, the SFC structure is extracted from the downlink signal, and the HEC operation is executed on the extracted SFC structure.

In step S905, the HEC calculation result is determined. If there is no error in the determination or the error can be corrected, the process proceeds to step S906, and if the error correction is not possible, the process proceeds to step S909.

In step S906, the value of SFC (Superframe counter) is extracted from the HEC calculation result.

In step S907, the SFC value extracted in step S906 is compared with the SFC value obtained by adding 1 to the locally held SFC value. If the results of the comparison match, the process proceeds to step S908 to locally hold the extracted SFC value, and then transition to the synchronous state. On the other hand, if the comparison results in step S907 do not match, the process proceeds to step S909.

In step S909, the value of the synchronous protection state continuation counter (denoted as “synchronous protection counter” in FIG. 13) is compared with (M-1). In the comparison, when the synchronous protection state continuation counter value ≥ (M-1), the state transitions to the hunt state. On the other hand, in the determination, when the synchronous protection state continuation counter value <(M-1), the process proceeds to step S910, 1 is added to the locally held SFC value, and synchronous protection is performed in the subsequent step S911. 1 is added to the state continuation counter value, and the process returns to step S900.

ITU (International Telecommunication Union) -TG. 9807.1 ITU (International Telecommunication Union) -TG. 989.1 ITU (International Telecommunication Union) -TG. 989.3

Here, when the wavelength switching is performed in the TWDM-PON, the downlink signal received by the ONU 10 is switched to the downlink signal of the OLT20 transmitted at the wavelength after the switching. Normally, the transmission timing of the PSBd of the downlink signal does not match between the OLT20s, so if wavelength switching occurs in ONU10 where frame synchronization has been established, in the conventional frame synchronization method, synchronization is once performed from the synchronization state. It transitions to a protected state and a hunt state, then goes through a pre-synchronization state, becomes a synchronization state, and frame synchronization with the OLT20 after switching is established. When the value of the synchronization protection state continuation counter M is set to 3, five state transitions are required from the occurrence of wavelength switching to the time when ONU10 establishes frame synchronization with the OLT20 after switching, and the state transitions are repeated. It will take 625 μs (125 μs × 5) or more to establish the synchronization. Here, the five state transitions are the transition from the synchronous state to the synchronous protection state (1 time), the continuation of the synchronous protection state (2 times), the transition from the hunt state to the pre-synchronization state (1 time), and before synchronization. There are a total of 5 transitions from the state to the synchronous state (1 time).

The present invention has been made in view of the above-mentioned problems, and in a wavelength division multiplexing passive optical subscriber network system, wavelength switching is performed to a transmission wavelength used for communication between a station-side terminal device and a subscriber-side terminal device. It is an object of the present invention to provide a control device and a control program capable of reducing the time from the loss of frame synchronization to the establishment of frame synchronization with the station-side termination device after switching when the above occurs.

In order to achieve the above-mentioned object, the control device according to the present invention is a control device of a subscriber side termination device in a passive optical subscriber network system, and a frame to be exchanged with the station side termination device. The processing unit to be processed, the holding unit holding the first frame counter value indicating the time when the wavelength switching is performed, and the subscriber-side termination device are included in the frame processed by the processing unit in the synchronized state. A reading unit that reads a second frame counter value indicating the wavelength switching execution time notified from the station-side termination device, and the holding unit holds the frequency switching execution time when the station-side termination device notifies the frequency switching execution time. A determination unit that determines whether or not the first frame counter value and the second frame counter value read by the reading unit match, and if the determination of the determination unit is an affirmative determination, the addition. It includes a state control unit that transitions the state of the terminal unit on the user side from the synchronous state to the hunt state.

In order to achieve the above-mentioned object, the control device of another aspect according to the present invention is a control device of the subscriber side termination device in the passive optical subscriber network system, and is exchanged with the station side termination device. A processing unit that processes the frame to be processed, a holding unit that holds a frame counter value indicating the time when the wavelength switching is performed, a determination unit that determines whether or not synchronization has been established by the synchronization pattern of the frame, and the subscriber. When the station side termination device notifies the wavelength switching execution time when the side termination device is in the synchronous state, the frame counter value included in the frame and the frame counter value held in the holding unit match, and the synchronization pattern When the switching timing retroactively reaches the first predetermined period from the scheduled arrival time, the subscriber-side termination device is transitioned from the synchronous state to the downlink signal switching state, and the second switching timing is performed. When the determination result by the determination unit is affirmative within a predetermined period, the state control unit that shifts the state of the subscriber side termination device from the downlink signal switching state to the synchronous state.
Is included.

In order to achieve the above-mentioned object, the control program according to the present invention is a control program of a subscriber side terminal device in a passive optical subscriber network system, and a computer mounted on the subscriber side terminal device is used. In a state in which the processing means for processing frames sent and received between the station-side terminating device, the holding means for holding the first frame counter value indicating the time when the wavelength switching is performed, and the subscriber-side terminating device are in a synchronized state. , The reading means for reading the second frame counter value indicating the wavelength switching execution time notified from the station-side termination device included in the frame processed by the processing means, and the wavelength switching execution from the station-side termination device. When the time is notified, the determination means for determining whether or not the first frame counter value held by the holding means and the second frame counter value read by the reading means match, and the above-mentioned If the determination of the determination means is an affirmative determination, the purpose is to function as a state control means for transitioning the state of the subscriber-side termination device from the synchronous state to the hunt state.

According to the present invention, in a wavelength division multiplexing passive optical subscriber network system, when wavelength switching occurs in the transmission wavelength used for communication between the station side terminal device and the subscriber side terminal device, the frame synchronization is switched from the out-of-frame synchronization. It is possible to provide a control device and a control program capable of reducing the time until the frame synchronization is established with the later station-side termination device.

It is a block diagram which shows an example of the structure of the PON system which concerns on embodiment. It is a state transition diagram for demonstrating the frame synchronization method which concerns on 1st Embodiment. It is a flowchart which shows the flow of the frame synchronization processing which concerns on 1st Embodiment. It is a state transition diagram for demonstrating the frame synchronization method which concerns on 2nd Embodiment. It is a part of the flowchart which shows the flow of the frame synchronization processing which concerns on 2nd Embodiment. It is a part of the flowchart which shows the flow of the frame synchronization processing which concerns on 2nd Embodiment. (A) is for explaining the operation of the ONU when the PSBd of the switching destination is delayed, (b) is for explaining the operation of the ONU when the PSBd of the switching destination is early, and (c) is for explaining the operation of the ONU when the frame synchronization pattern cannot be detected. It is a time chart of. (A) is a block diagram for explaining the configuration of the TWDM-PON system, and (b) is a diagram for explaining the configuration of the frame. It is a state transition diagram for demonstrating the frame synchronization method which concerns on the prior art. This is a part of a flowchart showing the flow of frame synchronization processing according to the prior art. This is a part of a flowchart showing the flow of frame synchronization processing according to the prior art. This is a part of a flowchart showing the flow of frame synchronization processing according to the prior art. This is a part of a flowchart showing the flow of frame synchronization processing according to the prior art.

Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings, but each figure is merely schematic to the extent that the present invention can be understood. Further, although a preferable configuration example of the present invention will be described below, numerical conditions and the like are merely suitable examples. Therefore, the present invention is not limited to the following embodiments, and many modifications or modifications can be made that can achieve the effects of the present invention without departing from the scope of the constitution of the present invention. In the following description, wavelength switching occurs in a PON system capable of dynamically switching the transmission wavelength used for communication between the station side terminating device and the subscriber side terminating device in the control device and the control program according to the present invention. In this case, a mode applied to the establishment of frame synchronization in the subscriber-side termination device will be described as an example.

[First Embodiment]
The control device and the control program according to the present embodiment will be described with reference to FIGS. 1 to 3.

FIG. 1 shows an example of the configuration of the PON system 1 according to the present embodiment. In the present embodiment, a TWDM-PON system will be illustrated as an example of the PON system 1.
Since the basic configuration of the PON system 1 shown in FIG. 1 is the same as that of the TWDM-PON system shown in FIG. 8A, the same reference numerals are given to the same configurations, and detailed description thereof will be omitted.

As shown in FIG. 1, the PON system 1 includes a plurality of ONU10s (in FIG. 1, two units of ONU10-1 and 10-2 are exemplified) and a plurality of OLT20s (in FIG. 1, OLT20-1, 20-). 2 is illustrated), a wavelength division multiplexing separator 30, an optical coupler 31, and an optical fiber 32 are included. Each of OLT20-1 (denoted as "OLT # 1" in FIG. 1) and OLT20-2 (denoted as "OLT # 2" in FIG. 1) is assigned a unique wavelength.

As shown in FIG. 1, ONU10-1 (denoted as "ONU # 1" in FIG. 1) and ONU10-2 (denoted as "ONU # 2" in FIG. 1) are each of the wavelength switching unit 11, O. It includes a / E (optical / electrical conversion unit) 12, a frame synchronization unit 13, and a PON terminal unit 14. The O / E12 converts an optical signal as a downlink signal into an electric signal. The frame synchronization unit 13 detects a frame included in the downlink signal and establishes synchronization in communication with the OLT20. The PON termination unit 14 is a portion that terminates PON-type communication with the OLT 20 according to a protocol. The wavelength switching unit 11 is a portion for switching the wavelength of the optical signal received by the O / E12, and when the wavelength switching with the OLT20 occurs, the ONU 10 switches the wavelength with the wavelength switching unit 11 to switch the wavelength. Connect with OLT20. For example, when the wavelength λ1 is assigned to the OLT20-1 and the wavelength λ2 is assigned to the OLT20-2, the ONU10-1 switches the wavelength to λ1 by the wavelength switching unit 11 to switch to the OLT20-1 and the wavelength λ2. Communication with OLT20-2 becomes possible. The frame synchronization unit 13 corresponds to the main part of the control device according to the present embodiment.

Here, in the synchronization establishment method according to the above-mentioned prior art, five state transitions are required from the occurrence of wavelength switching to the establishment of frame synchronization with the OLT20 after switching. It is desirable that the time until this frame synchronization is established is as short as possible. Therefore, in the frame synchronization establishment method according to the present embodiment, a state transition that transitions from the synchronization state to the hunt state at the time of wavelength switching is added to the synchronization establishment method according to the conventional technique having the state transition shown in FIG. ing.

The frame synchronization method according to the present embodiment will be described with reference to FIG. When performing wavelength switching, the OLT20 to ONU10 are usually notified of the switching destination wavelength and the switching execution time (superframe counter value for performing wavelength switching).

In the synchronous state, the ONU 10 further monitors the DS_Tuning_Start_Time signal state in addition to the two signal states of PSync_Det and SFC_Val in the present embodiment. DS_Tuning_Start_Time is a signal that becomes true when the superframe counter value locally held by ONU10 matches the switching execution time, and false otherwise. As shown in FIG. 2, the ONU 10 transitions to the hunt state when DS_Tuning_Start_Time becomes true in the synchronous state. Other state transitions are the same as the conventional state transitions.

The frame synchronization process according to the present embodiment will be described with reference to FIG. The frame synchronization process shown in FIG. 3 is a process in which a process corresponding to monitoring of the DS_Tuning_Start_Time signal state is added to the frame synchronization process shown in FIG. That is, steps S100 to S108 and steps S110 to S111 shown in FIG. 3 are the same as steps S800 to S808 and steps S809 to S810 shown in FIG. 12, except that step S109 is added.

In step S109, the value of the locally held SNES counter (SFC) is compared with the SFC value notified from the OLT20 as the time when the downlink signal switching is performed. If the comparison results match, the state shifts to the hunt state, and if they do not match, the process returns to step S100. That is, as compared with the frame synchronization process shown in FIG. 12, since the route that directly transitions from the synchronization state to the hunt state is added, the time until the frame synchronization is established is shortened.

As described in detail above, according to the control device and the control program according to the present embodiment, in the frame synchronization method in which the ONU 10 establishes the frame synchronization with the OLT20 at the time of wavelength switching, the hunt state is entered at the same time as the wavelength switching occurs. Since the state transition is performed, the frame synchronization can be established in the ONU 10 after the wavelength switching can be realized by three state transitions, so that the frame resynchronization can be established in 3/5 of the time as compared with the conventional case. Here, the three state transitions are the transition from the synchronous state to the hunt state (1 time), the transition from the hunt state to the pre-synchronous state (1 time), and the transition from the pre-synchronous state to the synchronous state (1 time). ), A total of 3 times.

[Second Embodiment]
The control device and the control program according to the present embodiment will be described with reference to FIGS. 4 to 7.

The frame synchronization method according to the present embodiment will be described with reference to FIG. FIG. 4 shows a state transition diagram of the frame synchronization method according to the present embodiment. In the frame synchronization method according to the present embodiment, as shown in FIG. 4, a downlink signal switching (DS Tuning) state is added to the state transition diagram according to the prior art shown in FIG. Further, in the frame synchronization method according to the present embodiment, it is preferable to match the transmission timing of PSBd between the OLT20s and to make the superframe counter value of PSBd transmitted at the same timing the same value.

On the other hand, the position of the PSBd of the downlink signal from each OLT20 received by the ONU 10 is deviated by 1 bit due to an error in adjusting the transmission timing of the PSBd, a difference in the transmission distance from the OLT20 to the optical coupler 31, and the like. It is extremely difficult to fit them together. Therefore, at the time of wavelength switching, the frame synchronization method according to the present embodiment defines the time (guard_time: guard time, protection time) for detecting the frame synchronization pattern. Further, as described above, when the wavelength switching is performed, the OLT20 to the ONU10 are usually notified of the switching destination wavelength and the switching execution time (superframe counter value for performing the wavelength switching).

As shown in FIG. 4, the ONU 10 monitors the DS_Tuning_Start_Time signal state in addition to the two signal states PSync_Det and SFC_Val in the synchronous state. In DS_Tuning_Start_Time, the superframe counter value locally held by ONU10 matches the switching execution time, and the frame synchronization pattern detection time (guard_time) goes back from the time when the next PSBd is predicted to be received. It is a signal that becomes true when the time comes, and false otherwise. In the synchronous state, the ONU 10 transitions to the downlink signal switching state when DS_Tuning_Start_Time becomes true.

In the downlink signal switching state, three signal states of Exact_PSsync, SFC_Val, and Time_Out are monitored. Time_Out is a signal that becomes true when the time (guard_time × 2, that is, twice the protection time) elapses from DS_Tuning_Start_Time, and false otherwise. In the downlink signal switching state, the ONU 10 transitions to the synchronous state when Exact_PSsync is true and SFC_Val is true. At this time, the superframe counter value is held locally. In addition, Time_Out transitions to the hunt state by true. Since the state transitions other than the state transitions related to the downlink signal switching state are the same as the state transitions of the frame synchronization method according to the prior art shown in FIG. 9, detailed description thereof will be omitted.

Next, the frame synchronization process according to the present embodiment will be described with reference to FIGS. 5 and 6. 5 and 6 describe the state transitions related to the downlink signal switching state. Since other state transitions are the same as the frame synchronization processing according to the prior art shown in FIGS. 10 to 13, detailed description thereof will be omitted.

FIG. 5 shows a frame synchronization process in the case of transitioning from the synchronization state to the downlink signal switching state and the synchronization protection state. Since steps S200 to S208 and steps S213 to S214 shown in FIG. 5 are the same as steps S800 to S808 and steps S809 to S810 shown in FIG. 12, detailed description thereof will be omitted.

In step S209, the value of the locally held SNES counter (SFC) is compared with the value of the SFC notified from the OLT20 as the time when the downlink signal switching is performed. If the comparisons do not match, the process returns to step S200, and if they match, the process proceeds to step S210.

In step S210, the time after (125 μs-guard_time (protection time)) from the detection position of the frame synchronization pattern is set as the downlink signal switching start time of the ONU 10. In other words, the downlink signal switching start time can be said to be the time retroactive by the guard_time (protection time) from the next detection position of the frame synchronization pattern. The "downlink signal switching start time" is an example of the "switching timing" according to the present invention.

In step S211 and wait until the time of ONU 10 coincides with the ONU downlink signal switching start time. Here, the ONU time means the time by the clock locally provided in the ONU 10.

The time elapsed (guard_time (protection time) × 2) from the ONU downlink signal switching start time is set as the ONU downlink signal switching expiration time, and then the downlink signal switching state is entered. Here, the time between the ONU downlink signal switching signal start time and the ONU downlink signal switching expiration time is set to (guard_time (protection time) × 2) as the detection position of the frame synchronization pattern in step S210, as will be described later. This is because the protection time is set to be equal before and after. The protection time on the side earlier than the detection position of the frame synchronization pattern may be referred to as "forward protection time", and the protection time on the later side may be referred to as "rear protection time".

Next, with reference to FIG. 6, the frame synchronization process in the case of transitioning from the downlink signal switching state to the hunt state and the synchronization state will be described.

In step S300, the ONU downlink signal switching expiration time and the ONU time are compared. If the results of the determination are in agreement, the process proceeds to the hunt state, and if the results are inconsistent, the process proceeds to step S301.

In step S301, 64 bits are extracted from the frame of the downlink signal.

In step S302, the 64-bit extracted in step S301 is compared with the frame synchronization pattern. If the result of the comparison is a match for all bits, the process proceeds to step S303. On the other hand, if even one bit does not match, the process proceeds to step S307, the extraction position is shifted by one bit, and then the process returns to step S300.

In step S303, the extraction position is shifted by 64 bits, and in the next step S304, 64 bits are extracted from the downlink signal and the HEC operation is executed. That is, the SFC structure is extracted from the downlink signal, and the HEC operation is executed on the extracted SFC structure.

In step S305, the result of the HEC calculation executed in step S304 is determined.
If it is determined in the determination that there is no error or that the error can be corrected, the process proceeds to step S306.

In step S306, the SFC value is extracted from the HEC calculation result, the extracted SFC value is held locally, and then the synchronization state is entered.

On the other hand, if it is determined in step S305 that error correction is not possible, the process proceeds to step S308, the extraction position is returned by 63 bits, and then the process returns to step S300.

Next, with reference to the time chart shown in FIG. 7, the operation of the ONU 10 when the transmission timing of PSBd (area including the frame synchronization pattern PSsync) deviates between the OLT20s and the frame synchronization cannot be established will be described. do.

FIG. 7A shows an operation when the PSBd of OLT # 2 is delayed in the wavelength switching from OLT # 1 to OLT # 2. OLT # 1_Tx represents a downlink transmission signal from OLT # 1, and OLT # 2_Tx represents a downlink transmission signal from OLT # 2. The State of ONU10 indicates the state in the state transition diagram shown in FIG. 4, and the local SFC indicates the Superframe counter value locally held by ONU10.

When the switching destination wavelength (wavelength of OLT # 2) and the switching execution time (superframe counter = n) are notified from OLT # 1, the ONU 10 goes back by the guard_time time from the beginning of the next (superframe counter = n + 1) PSBd. The time is set to DS_Tuning_Start_Time, and when that time is reached, the state transitions from the synchronous (Sync) state to the downlink signal switching (DS_Tuning) state. That is, the wavelength switching unit 11 of the ONU 10 switches the wavelength from the wavelength of the switching source OLT # 1 to the wavelength of the switching destination OLT # 2. After that, the O / E 12 receives the downlink signal from the OLT # 2, and the frame synchronization unit 13 starts the frame synchronization pattern detection operation. When the frame synchronization pattern is detected within the period of (guard_time (protection time) × 2) and the effectiveness of the SFC region (SFC_Val == true) is confirmed, the superframe counter is held in the local SFC and synchronized (Sync). Transition to the state.

FIG. 7B shows the operation when the PSBd of OLT # 2 is accelerated in the wavelength switching from OLT # 1 to OLT # 2. The operation of the ONU 10 shown in FIG. 7 (b) can be understood according to FIG. 7 (a).

FIG. 7C shows the ONU10 operation when the frame synchronization pattern cannot be detected due to the wavelength switching from OLT # 1 to OLT # 2. In FIG. 7C, after transitioning to the downlink signal switching (DS Tuning) state, the downlink signal from OLT # 2 is received and the frame synchronization pattern detection operation is started. Since the frame synchronization pattern could not be detected within the period, Time_Out becomes true and the state transitions to the hunt state.

As described in detail above, according to the control device and the control program according to the present embodiment, in the frame synchronization method in which the ONU 10 establishes the frame synchronization with the OLT20 at the time of wavelength switching, it temporarily descends at the same time as the wavelength switching occurs. The state transitions to the signal switching (DS Tuning) state. As a result, it is possible to transition to the synchronous (Sync) state by detecting the frame synchronization pattern of the downlink signal after switching within a certain period of time, so that it is less than 1/5 of the state transition according to the prior art shown in FIG. In this time, it becomes possible to establish frame resynchronization. Further, by matching the PSBd output timings from each OLT20 as much as possible, the frame synchronization pattern detection time (guard_time) can be reduced as much as possible, so that frame resynchronization can be established in an extremely short time as compared with the conventional case. Is possible. That is, for example, in FIG. 7A, if the PSBd transmission timing of OLT # 1 and the PSBd transmission timing of OLT # 2 are close to each other, both PSBds are likely to be within the period of (guard_time (protection time) × 2). Also, the closer the timings of both PSBds are, the shorter the detection time of the frame synchronization pattern included in the downlink signal from OLT # 2.

In the present embodiment, as shown in FIG. 7, a mode in which the front protection time and the rear protection time are equalized with respect to the frame synchronization pattern detection position has been described as an example, but the present invention is not limited to this, and the front protection time and the rear protection time are defined. Each may have a different time. Further, only one of the front protection time and the rear protection time may be set.

In each of the above embodiments, the control device and the control program according to the present invention are applied to the TWDM-PON system as an example, but the present invention is not limited to this, and the PON system is a type that does not use wavelength division multiplexing. It may be in the form applied to.

1 PON system 10, 10-1, 10-2, ..., 10-m ONU
11 Wavelength switching unit 12 O / E
13 Frame synchronization unit 14 PON terminal unit 20, 20-1, 20-2, ..., 20-n OLT
30 Wavelength Division Multiplexer 31 Optical Coupler 32 Optical Fiber

To achieve the above object, engagement Ru control apparatus of the present invention is a control apparatus of the subscriber side terminating device in a passive optical network system, are exchanged between the station-side termination apparatus It is determined whether or not synchronization is established by the processing unit that processes the frame, the holding unit that holds the first frame counter value notified from the station-side termination device as the wavelength switching execution time, and the synchronization pattern of the frame. When the first frame counter value is held in the holding unit while the determination unit and the subscriber side terminating device are in a synchronized state, the first frame counter value and the frame received from the station side terminating device are used. At the switching timing that goes back by the first predetermined period from the scheduled arrival time of the next synchronization pattern that matches the second frame counter value that is the count value of the frame included in the above. The subscriber side termination device is transitioned from the synchronous state to the downlink signal switching state, and when the determination result by the determination unit is affirmative within a second predetermined period from the switching timing, the subscriber side termination device is used. A state control unit that transitions the state of the device from the downlink signal switching state to the synchronous state,
Is included.

In order to achieve the above-mentioned object, the control program according to the present invention is a control program of a subscriber side terminal device in a passive optical subscriber network system, and a computer mounted on the subscriber side terminal device is used. Synchronization of the frame with a processing means for processing a frame sent and received between the station-side terminal device and a holding means for holding a first frame counter value notified from the station-side terminal device as a wavelength switching execution time. When the determination means for determining whether or not synchronization is established by the pattern and the first frame counter value are held by the holding means while the subscriber-side termination device is in the synchronization state, the first frame counter value is used. , The first predetermined time from the scheduled time when the next synchronization pattern that matches the count value of the frame included in the frame received from the station-side termination device and the second frame counter value is scheduled to arrive. At the switching timing retroactive to the specified period, the subscriber-side termination device is transitioned from the synchronous state to the downlink signal switching state, and the determination result by the determination means is affirmatively determined within a second predetermined period from the switching timing. When becomes, the purpose is to function as a state control means for transitioning the state of the subscriber-side termination device from the downlink signal switching state to the synchronous state.

Claims (6)

A control device for a subscriber-side termination device in a passive optical subscriber network system, and a processing unit that processes frames sent and received between the station-side termination device and the processing unit.
A holding unit that holds a first frame counter value indicating the time when wavelength switching is performed, and
When the subscriber-side termination device is in a synchronous state, a reading unit that reads a second frame counter value indicating a wavelength switching execution time notified from the station-side termination device, which is included in the frame processed by the processing unit, and
When the wavelength switching execution time is notified from the station-side termination device, does the first frame counter value held by the holding unit match the second frame counter value read by the reading unit? Judgment unit that determines whether or not
If the determination of the determination unit is affirmative, the state control unit that transitions the state of the subscriber-side termination device from the synchronous state to the hunt state,
Control device including. A control device for a subscriber-side termination device in a passive optical subscriber network system, and a processing unit that processes frames sent and received between the station-side termination device and the processing unit.
A holding unit that holds a frame counter value indicating the time when wavelength switching is performed, and
A determination unit that determines whether or not synchronization has been established based on the synchronization pattern of the frame, and
When the station-side termination device notifies the wavelength switching execution time in the synchronous state of the subscriber-side termination device, the frame counter value included in the frame and the frame counter value held in the holding unit match, and the above-mentioned When the switching timing retroactively reaches the first predetermined period from the scheduled arrival time of the synchronization pattern, the subscriber-side termination device is transitioned from the synchronization state to the downlink signal switching state.
A state in which the state of the subscriber-side termination device is changed from the downlink signal switching state to the synchronous state when the judgment result by the judgment unit is affirmative within a second predetermined period from the switching timing. Control unit and
Control device including. When the determination result by the determination unit is not affirmative within the second predetermined period, the state control unit changes the state of the subscriber side termination device from the downlink signal switching state to the hunt state. The control device according to claim 2, wherein the transition is performed. The control device according to claim 2 or 3, wherein the state control unit sets the switching timing by using a time measuring unit included in the subscriber-side termination device. The control according to any one of claims 2 to 4, wherein the state control unit switches the wavelength received by the subscriber-side termination device from the wavelength of the switching source to the wavelength of the switching destination at the switching timing. Device. A control program for a subscriber-side termination device in a passive optical subscriber network system, and a computer mounted on the subscriber-side termination device.
A processing means for processing frames sent and received between the station side terminal device and
A holding means for holding a first frame counter value indicating the time when wavelength switching is performed, and
A reading means for reading a second frame counter value indicating a wavelength switching execution time notified from the station-side termination device, which is included in the frame processed by the processing means while the subscriber-side termination device is in a synchronous state.
When the wavelength switching execution time is notified from the station-side termination device, does the first frame counter value held by the holding means match the second frame counter value read by the reading means? Judgment means to judge whether or not
If the determination of the determination means is an affirmative determination, the state control means for transitioning the state of the subscriber-side termination device from the synchronous state to the hunt state, and
A control program to function as.

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