JP7400973B2 - Optical communication systems and optical line termination equipment - Google Patents

Description

The present invention relates to an optical communication system and an optical line termination device.

In optical access mobile fronthaul (MFH) and mobile backhaul (MBH), in order to achieve frequency and time synchronization, GPS (Global Positioning System) or GNSS (Global Navigation Satellite System), etc. Communication is performed using, for example, PTP (Precision Time Protocol: time synchronization) or SyncE (synchronous Ethernet: frequency synchronization), which receives a synchronization reference signal from the network and distributes the synchronization reference signal (synchronization signal) to lower-level devices.

For example, a synchronization reference signal is input from a GPS receiver to an OLT (Optical Line Terminal), and the frequency and time are synchronized from the UNI (User Network Interface) of an ONU (Optical Network Unit). Techniques for providing signals to users are known (for example, see Non-Patent Documents 1 and 2).

Takayoshi Tashiro and 6 others, "10G-EPON system compatible with frequency and time synchronization functions for mobile backhaul applications", IEICE Transactions B, 2013, Vol.J96-B No.3 pp.321- 329 “Time synchronization function”, ANSL R&D Times No. 93 (2016_09), [online], NTT Access Service Systems Laboratories, [Retrieved June 16, 2020], Internet <URL: https://www.ansl .ntt.co.jp/j/times/093/01/04.html〉

However, in the past, when base stations of multiple different carriers were each equipped with a GMC (Grand Master Clock) and connected to a PON (Passive Optical Network), there was a problem that different synchronization reference signals would be mixed. .

An object of the present invention is to provide an optical communication system and an optical line termination device that can efficiently distribute synchronization reference signals even when a plurality of base stations using different synchronization reference signals are connected.

An optical communication system according to one aspect of the present invention is an optical communication system in which a synchronization signal is distributed via an optical line from an optical line termination device to which base stations of a plurality of carriers are respectively connected to a plurality of optical network units. The optical line termination device includes one or more slave processing units that process synchronization signals transmitted from each of the base stations as slaves, a distribution unit that distributes one of the plurality of synchronization signals as a master clock, and one one or more correction sections that correct the synchronization signal processed by the slave processing section based on the master clock distributed by the distribution section, and a different identifier for each carrier for the synchronization signal corrected by the correction section; one or more conversion units that convert the synchronization signal so that the conversion unit attaches the synchronization signal, and synchronization signal processing that processes the synchronization signal converted by the conversion unit so as to transmit the synchronization signal converted by the conversion unit to the optical network unit that is different for each carrier via an optical line based on the identifier. It is characterized by having a part.

Further, the optical line termination device according to one aspect of the present invention includes one or more slave processing units that process synchronization signals transmitted from each of the base stations of a plurality of carriers as a slave, and one or more of the plurality of synchronization signals. a distribution unit that distributes the synchronization signal as a master clock; one or more correction units that correct the synchronization signal processed by the one or more slave processing units based on the master clock distributed by the distribution unit; one or more conversion units that convert the synchronization signal to be assigned a different identifier for each carrier, and the synchronization signal converted by the conversion unit is connected to an optical network unit that is different for each carrier based on the identifier. and a synchronous signal processing unit that performs processing to transmit data via the synchronous signal processing unit.

According to the present invention, even if a plurality of base stations using different synchronization reference signals are connected, the synchronization reference signal can be efficiently distributed.

1 is a diagram illustrating a configuration example of an optical communication system according to an embodiment. FIG. 2 is a diagram illustrating an example of functions that the OLT has and its surroundings. FIG. 3 is a diagram illustrating synchronization signal information held by a synchronization signal database. It is a diagram showing an example of the configuration of an ONU. It is a figure which illustrates the setting pattern table which the setting pattern DB holds. FIG. 2 is a diagram illustrating the flow of downlink communication performed by the optical communication system, focusing on the operation of the OLT. FIG. 2 is a diagram illustrating the flow of downlink communication performed by the optical communication system, centering on the operations of ONUs. FIG. 2 is a diagram illustrating the flow of uplink communication performed by the optical communication system, focusing on the operation of the ONU. FIG. 2 is a diagram illustrating the flow of uplink communication performed by the optical communication system, focusing on the operation of the OLT. FIG. 2 is a diagram illustrating an example of the hardware configuration of an OLT. FIG. 2 is a diagram showing the configuration of an optical communication system as a comparative example.

In explaining the optical communication system according to one embodiment, first, the background of the invention will be explained.

In an optical communication system, for example, a base station master station (DU) and a base station slave station (RU) are connected for each mobile carrier (carrier) using a synchronization signal protocol such as PTP or SyncE. A PON system may be inserted to configure a system in which a plurality of carriers coexist.

At this time, it is assumed that the supply source of the synchronization signal between the DU and the RU is independent for each carrier. Further, it is assumed that the OLT and DU are connected during construction work, and ONUs and RUs are additionally added in accordance with user demand. Further, it is assumed that the setting of the synchronization signal between the DU and the RU will not be changed due to the introduction of the PON system.

In this case, the optical communication system may have a configuration in which the OLT is connected to DUs of multiple carriers, accommodating a combination of multiple ONUs and RUs, and a configuration in which synchronization signals of multiple carriers are transmitted through the same optical fiber.

Depending on the frame structure of the synchronization signal, it may be difficult to identify the carrier from the synchronization signal, such as when the destination MAC addresses are the same. On the other hand, if the OSU is divided for each carrier within the OLT, the wiring efficiency of optical fibers will deteriorate.

FIG. 11 is a diagram showing the configuration of an optical communication system 10 as a comparative example. The optical communication system 10 includes, for example, three base station master units (base station master station: DU) 2-1 to 2-3 and three base station slave units (base station slave station: RU) 3-1 to 2-3. 3-3.

The base station base units 2-1 to 2-3 are operated by different mobile operators (carriers), and receive different synchronization reference signals (synchronization signals) from the GMCs 4-1 to 4-3. GMC4-1 to GMC4-3 are devices that each receive a synchronization signal using a GPS (GNSS) receiver or the like, and distribute the synchronization signal, such as PTP or SyncE, to lower-level devices.

The OLT 50 includes OSUs (Optical Subscriber Units) 51-1 to 51-3. The base station master units 2-1 to 2-3 are connected to the base station slave units 3-1 to 3-3 via OSUs 51-1 to 51-3 and ONUs 70-1 to 70-3, respectively. . Furthermore, the base station slave units 3-1 to 3-3 include TSCs (Time Slave Clock) 8-1 to 8-3, respectively, which supply time to end applications, for example.

In this case, the base station base unit 2-1 transmits the synchronization signal received by the GMC 4-1 to the base station slave unit 3-1 via the OSU 51-1 and ONU 70-1. The base station slave unit 3-1 performs time and frequency synchronization with the base station 2-1 via the TSC 8-1 within the base station slave unit 3-1.

Similarly, the base station base unit 2-2 transmits the synchronization signal received by the GMC 4-2 to the base station slave unit 3-2 via the OSU 51-2 and ONU 70-2. Furthermore, the base station base unit 2-3 transmits the synchronization signal received by the GMC 4-3 to the base station slave unit 3-3 via the OSU 51-3 and ONU 70-3. Note that the ONUs 70-1 to 70-3 may be BC (Boundary Clock).

In other words, in the optical communication system 10, the base station master units 2-1 to 2-3, each equipped with a different GMC, and the base station slave units 3-1 to 3-3 perform synchronous signal communication such as PTP or SyncE. In this case, the ONUs 70-1 to 70-3 accommodated in the OLT 50 are separated for each carrier in order to prevent different synchronization signals from being mixed. In the optical communication system 10, only base station slave units of the same carrier are arranged under the OSU of each carrier.

Therefore, in the optical communication system 10, the OSU is divided for each carrier within the OLT 50, resulting in poor optical fiber wiring efficiency.

Next, an optical communication system 1 according to an embodiment will be described. FIG. 1 is a diagram showing a configuration example of an optical communication system 1 according to an embodiment.

As shown in FIG. 1, the optical communication system 1 includes, for example, three base station master units (base station master stations: DU) 2-1 to 2-3, and three base station slave units (base station slave stations: RU) 3-1 to 3-3, OLT 5, optical splitter 6, and ONU 7-1 to 7-3. In other words, the optical communication system 1 has a configuration in which a PON section is inserted between the base station master units 2-1 to 2-3 and the base station slave units 3-1 to 3-3.

The base station base units 2-1 to 2-3 are operated by different mobile operators (carriers), and receive different synchronization reference signals (synchronization signals) from the GMCs 4-1 to 4-3. GMC4-1 to GMC4-3 are devices that each receive a synchronization signal using a GPS (GNSS) receiver or the like, and distribute the synchronization signal, such as PTP or SyncE, to lower-level devices.

The OLT 5 transmits signals input from the base station base units 2-1 to 2-3 to the base station slave units 3-1 to 3-3 via the optical splitter 6 and the ONUs 7-1 to 7-3. . Furthermore, the base station slave units 3-1 to 3-3 include TSCs (Time Slave Clocks) 8-1 to 8-3, respectively, for synchronizing time between the DU and the RU, for example.

Note that the OLT 5 is enabled to recognize the unicast connection state with a specific ONU by using authentication data (ONU authentication table) at the time of connection of the ONUs 7-1 to 7-3.

Hereinafter, unless one of the plurality of configurations is specified, such as base station master units 2-1 to 2-3, it will simply be abbreviated as base station master unit 2, etc.

FIG. 2 is a diagram showing an example of functions that the OLT 5 has and its surroundings. The OLT 5 includes, for example, a master CLK reception section 501, a master CLK distribution section 502, slave processing sections 503-1, 503-2, time correction sections 504-1, 504-2, conversion sections 505-1, 505-2, and a synchronization signal. It includes a database (DB) 506, an authentication database (DB) 507, section synchronization processing units 508-1 and 508-2, and a synchronization signal processing unit 509. Note that the OLT 5 has not only the time synchronization signal processing function shown in FIG. 2 but also other functions that OLTs generally have.

Further, the OLT 5 is configured to transmit and receive signals via interfaces (I/F) 500-1 to 500-3 or an interface (I/F) 510 serving as SNI (Service Node Interface) ports. The I/Fs 500-1 to 500-3 can transmit and receive not only main signals but also S-plane signals such as time synchronization signals and frequency synchronization signals. Each I/F 510 is a PON port.

The OLT 5 uses a synchronization signal output from any of the base station base units 2-1 to 2-3 as a master CLK. Further, the OLT 5 may be supplied with the master CLK from the outside.

Here, it is assumed that the I/F 500-1 of the OLT 5 receives a synchronization signal inputted from a master CLK supply section 200 provided externally (or the base station main unit 2-1) as a master CLK. Further, in the OLT 5, the I/F 500-2 receives the time synchronization signal A and the frequency synchronization signal A' distributed by the master distribution unit 202-1 provided in the base station base unit 2-2. Further, in the OLT 5, the I/F 500-3 receives the time synchronization signal B and the frequency synchronization signal B' distributed by the master distribution unit 202-2 provided in the base station base unit 2-3.

Master CLK receiving section 501 receives master CLK supplied by master CLK supplying section 200 via I/F 500-1, and outputs it to master CLK distribution section 502.

Master CLK distribution section 502 distributes master CLK input from master CLK reception section 501 to time correction sections 504-1 and 504-2. That is, the master CLK distribution section 502 functions as a distribution section that distributes any one of the plurality of synchronization signals as a master clock.

The slave processing unit 503-1 has a function as a BC (Boundary Clock) that processes and distributes the synchronization signal transmitted by the base station base unit 2-2 via the I/F 500-2 as a slave, and transmits the synchronization signal. It is output to the time correction section 504-1.

The slave processing unit 503-2 has a function as a BC (Boundary Clock) that processes and distributes the synchronization signal transmitted by the base station base unit 2-3 via the I/F 500-3 as a slave, and transmits the synchronization signal. It is output to the time correction section 504-2.

The time correction unit 504-1 compares the master CLK input from the master CLK distribution unit 502 and the synchronization signal input from the slave processing unit 503-1, and corrects the synchronization signal (time) using the difference. , outputs the corrected synchronization signal to the converter 505-1. That is, the time correction section 504-1 has a function as a correction section that corrects the synchronization signal processed by the slave processing section 503-1 based on the master clock distributed by the master CLK distribution section 502.

The time correction unit 504-2 compares the master CLK input from the master CLK distribution unit 502 and the synchronization signal input from the slave processing unit 503-2, and uses the difference to correct the synchronization signal (time). , outputs the corrected synchronization signal to the converter 505-2. That is, the time correction section 504-2 has a function as a correction section that corrects the synchronization signal processed by the slave processing section 503-2 based on the master clock distributed by the master CLK distribution section 502.

The conversion unit 505-1 uses the synchronization signal corrected by the time correction unit 504-1 and the synchronization signal information held by the synchronization signal database 506 to convert an identifier that makes the carrier identifiable. The results are output to the synchronization signal database 506 and the section synchronization processing section 508-1. For example, the conversion unit 505-1 converts the synchronization signal corrected by the time correction unit 504-1 so as to attach a different identifier to each carrier.

The conversion unit 505-2 uses the synchronization signal corrected by the time correction unit 504-2 and the synchronization signal information held by the synchronization signal database 506 to convert an identifier that makes the carrier identifiable. The results are output to the synchronization signal database 506 and the section synchronization processing section 508-2. For example, the conversion unit 505-2 converts the synchronization signal corrected by the time correction unit 504-2 so as to attach a different identifier to each carrier.

The synchronization signal database 506 is a database that holds information (synchronization signal information) that associates a transmission source of a synchronization signal with each SNI port of the OLT 5. Here, it is assumed that the synchronization signal database 506 holds synchronization signal information that refers to the ONU authentication table held by the authentication database 507.

For example, the synchronization signal database 506 is used as design data when constructing the base station base units 2-1 to 2-3 and the OLT 5, and is used when connecting the base station base units 2-1 to 2-3 to the OLT 5. It is adapted to store synchronization signal information.

FIG. 3 is a diagram illustrating synchronization signal information held by the synchronization signal database 506. For example, when the synchronization signals are PTP and SyncE, the synchronization signal database 506 includes the user ID, SNI port number, synchronization signal identifier, PORT identity, PON section PTP domain number, reserved 4 bits of the PON section QL-TLV field, and Original PTP. It holds management items such as domain number and Original QL-TLV reserved 4bit.

For example, the synchronization signal database 506 uses the user ID included in the ONU authentication table held by the authentication database 507 as an index to enable unicast transfer that identifies the carrier in the PON section.

Specifically, the synchronization signal database 506 enables unicast transfer of PON sections using slots, ports, PON-VIDs (VLAN IDs), LLIDs (Logical Link IDs), and the like.

In addition, the management item A shown in FIG. 3 is an identifier converted by the conversion units 505-1 and 505-2 when transmitting a signal to the ONUs 7-1 to 7-3, for example, in order to identify the synchronization signal for each carrier. It is. For example, the conversion units 505-1 and 505-2 embed the management item of A as an identifier in the TIMESYNC message included in PTP and the ESMC message included in SyncE.

Furthermore, the management item B shown in FIG. 3 holds values set for each carrier by the synchronization signal input from the SNI port in order to write to the ONU authentication table held by the authentication database 507. . For example, the converting units 505-1 and 505-2 write back the management item of B when receiving signals from the ONUs 7-1 to 7-3, and store it in the synchronization signal database 506.

The section synchronization processing sections 508-1 and 508-2 perform processing for synchronizing signals in the PON section using the identifiers converted by the conversion sections 505-1 and 505-2, and transmit the processing results to the synchronization signal processing section. Output to 509.

The synchronous signal processing unit 509 identifies the carrier when processing an uplink signal, identifies the PON port to which the signal is distributed when processing a downlink signal, and sends the processing results to the I/F 510. Output.

Furthermore, the synchronization signal processing unit 509 searches the ONU authentication table held in the authentication database 507 using the user ID of the synchronization signal information held in the synchronization signal database 506 as a key, and distributes the synchronization signal to the unicast LLID. It has the function of

In addition, the synchronization signal processing unit 509 transmits synchronization signals for each unicast LLID so that synchronization signals can be simultaneously distributed to multiple base station units (RUs) connected to the ONUs 7-1 to 7-3. It has the ability to copy and distribute synchronization signals.

That is, the synchronization signal processing section 509 has a function of processing the synchronization signals converted by the conversion sections 505-1 and 505-2 so as to transmit them to different ONUs 7 for each carrier via the optical splitter 6 based on the identifier. At this time, the synchronization signal processing unit 509 identifies the carrier based on the synchronization signal database 506 and the authentication database 507, and performs unicast transfer.

The I/F 510 is a PON port for connecting the synchronization signal processing unit 509 and the ONUs 7-1 to 7-3, and may be one or more.

FIG. 4 is a diagram showing an example of the configuration of the ONU 7. As shown in FIG. The ONU 7 includes a section synchronization processing section 701, a time correction section 702, a conversion section 703, a setting pattern database (DB) 704, and a master processing section 705. Further, the ONU 7 is configured to transmit and receive signals via an interface (I/F) 700 and an interface (I/F) 706.

The section synchronization processing unit 701 acquires the synchronization signal via the I/F 700, transmits and receives the synchronization signal to and from the OLT 5, performs processing to synchronize the signals in the PON section, and converts the processing result including the synchronization signal to the time. It is output to the correction unit 702.

The time correction section 702 corrects the synchronization signal input from the section synchronization processing section 701 and outputs the corrected synchronization signal to the conversion section 703.

The conversion unit 703 refers to the setting pattern table held in the setting pattern DB 704, converts an identifier that makes the synchronization signal identifiable, and outputs the conversion result to the master processing unit 705.

The setting pattern DB 704 is a database that holds a setting pattern table for each ONU service. FIG. 5 is a diagram illustrating a setting pattern table held by the setting pattern DB 704.

As shown in FIG. 5, the setting pattern table includes, for example, when the synchronization signal is PTP and SyncE, PON-VID, carrier (mobile operator) identifier, PORT identity, PTP domain number, and reserved 4 bits of the QL-TLV field. , Original PTP domain number, and Original QL-TLV reserved 4bit.

In addition, the setting pattern table is distributed from the OLT 5 as an identifier to the TIMESYNC message included in PTP and the ESMC message included in SyncE in order to identify the synchronization signal for each carrier in the management item A shown in Figure 5. Retains the value. For example, the conversion unit 703 overwrites the PTP domain number when transmitting a signal to the OLT 5.

Furthermore, the management item B shown in FIG. 5 in the setting pattern table holds values set for each carrier for transmitting and receiving PTP/SYNCE to the UNI side. For example, the conversion unit 703 writes back the management item of B when transmitting the synchronization signal to the base station handset 3.

The master processing unit 705 performs master processing to generate a synchronization signal for the RU using the identifier converted by the conversion unit 703, and transmits the generated synchronization signal to each of the base station slave units 3 that are users via the I/F 706. Send to.

Then, by adding an item of synchronization signal information held by the OLT 5 to the setting pattern used for authentication and settings when connecting from the OLT 5 to the ONU 7, the ONU 7 can determine the source of the synchronization signal within the PON section. identify. Further, the ONU 7 may hold information that identifies the carrier of the synchronization signal transmission source of the base station handset 3 to be connected, and the values before and after conversion of the synchronization signal converted by the OLT 5.

Next, an example of the operation of the optical communication system 1 will be described, focusing on the operations of the OLT 5 and ONU 7. FIG. 6 is a diagram illustrating the flow of downlink communication performed by the optical communication system 1, focusing on the operation of the OLT 5.

As shown in FIG. 6, when the base station base units 2-1 to 2-3 transmit a synchronization signal to the OLT 5 (S100), the slave processing unit 503 of the OLT 5 receives the synchronization signal (S102).

The time correction unit 504 determines whether the synchronization signal input from the slave processing unit 503 is synchronized with the external CLK serving as the master CLK (S104). If the time correction unit 504 determines that they are not synchronized (S104: No), the process proceeds to S106, and if it determines that they are synchronized (S104: Yes), the process proceeds to S108.

In the process of S106, the OLT 5 transmits, for example, CLK Class=248 in the PTP ANNOUCE message and QL-DUS in the SyncE ESMC message to the SNI port, indicating that it is in an asynchronous state.

In the process of S108, the OLT 5 transmits Delay Req from the slave processing unit 503 to the master side.

The slave processing unit 503 determines whether or not, for example, a PTP Delay resp message has been received (S110). For example, if the slave processing unit 503 determines that a PTP Delay resp message has not been received (S110: No), the slave processing unit 503 proceeds to the process of S112; for example, if it determines that a PTP Delay resp message has been received (S110: If Yes), the process advances to S114.

In the process of S112, the OLT 5 determines that it is in an asynchronous state, for example, as CLK Class=248 in the PTP ANNOUCE message, and as QL-DUS in the SyncE ESMC message, and proceeds to the process of S116.

In the process of S114, the time correction unit 504 compares the master CLK input from the master CLK distribution unit 502 and the synchronization signal input from the slave processing unit 503, corrects the time using the difference, and 505.

When the conversion unit 505 performs conversion to rewrite the identifier of the synchronization signal (S116), the section synchronization processing unit 508 transmits the synchronization signal to the synchronization signal processing unit 509 (S118).

The synchronization signal processing unit 509 searches the ONU authentication table held in the authentication database 507 to determine whether or not there is a user ID of the synchronization signal information held in the synchronization signal database 506 (S120). When the synchronization signal processing unit 509 determines that there is no user ID (S120: No), the process proceeds to S122, and when it determines that there is a user ID (S120: Yes), the process proceeds to S124.

In the process of S122, the OLT 5 does not distribute the synchronization signal. In the process of S124, the OLT 5 selects a unicast transfer destination from the authentication database 507.

Then, the OLT 5 transmits a synchronization signal from the PON port to the destination ONU 7 of the unicast LLID (S126).

FIG. 7 is a diagram illustrating the flow of downlink communication performed by the optical communication system 1, focusing on the operation of the ONU 7.

As shown in FIG. 7, when the ONU 7 receives a PON synchronization signal from the PON port (S200), the section synchronization processing unit 701 receives the synchronization signal (S202). Then, the section synchronization processing unit 701 transmits, for example, a PTP Delay req message to the OLT 5 (S204).

The ONU 7 determines whether or not, for example, a PTP Delay resp message has been received from the PON port (S206). For example, when the ONU 7 determines that the PTP Delay resp message has not been received (S206: No), the ONU 7 proceeds to the process of S208, and for example, when it determines that the PTP Delay resp message has been received (S206: Yes). The process proceeds to S210.

In the process of S208, the ONU 7 determines that it is in an asynchronous state, for example, as CLK Class=248 in the PTP ANNOUCE message, and as QL-DUS in the SyncE ESMC message, and proceeds to the process of S212.

When the conversion unit 703 performs conversion to write back the identifier of the synchronization signal (S212), the master processing unit 705 transmits the synchronization signal to the UNI port (S214).

FIG. 8 is a diagram illustrating the flow of uplink communication performed by the optical communication system 1, focusing on the operation of the ONU 7. As shown in FIG.

As shown in FIG. 8, when the ONU 7 receives a synchronization signal from the base station unit (RU) 3 through the UNI port (S300), the master processing unit 705 transmits, for example, a PTP Delay resp message to the UNI port (S302). ).

The conversion unit 703 performs conversion to rewrite the identifier for each carrier so as to identify the carrier (S304).

Then, when the time correction unit 702 performs a correction to correct the time difference (S306), the section synchronization processing unit 701 determines whether or not, for example, a PTP Delay resp message has been received (S310). For example, if the section synchronization processing unit 701 determines that a PTP Delay resp message has not been received (S310: No), the section synchronization processing unit 701 proceeds to the process of S312; for example, if it determines that a PTP Delay resp message has been received (S310: :Yes), the process advances to S314.

In the process of S312, the ONU 7 determines that it is in an asynchronous state, for example, as CLK Class=248 in the PTP ANNOUCE message, and as QL-DUS in the SyncE ESMC message, and proceeds to the process of S314. Then, the ONU 7 transmits a PON synchronization signal from the PON port (S314).

FIG. 9 is a diagram illustrating the flow of uplink communication performed by the optical communication system 1, focusing on the operation of the OLT 5. As shown in FIG.

As shown in FIG. 9, when the OLT 5 receives a synchronization signal from the PON port (S400), the OLT 5 searches the ONU authentication table held by the authentication database 507 to determine whether or not there is a user ID with the SNI port number. (S402). If the OLT 5 determines that there is no user ID (S402: No), the process proceeds to S404, and if it determines that the user ID exists (S402: Yes), the process proceeds to S406.

In the process of S404, the OLT 5 transmits the asynchronous state to the PON port, for example, as CLK Class=248 in the PTP ANNOUCE message, and as QL-DUS in the SyncE ESMC message, for example.

In the process of S406, the OLT 5 transmits the synchronization signal to the conversion source synchronization signal processing unit 509 based on the identifier of the synchronization signal. Further, the OLT 5 transmits, for example, a PTP Delay resp message from the interval synchronization processing unit 508 to the synchronization signal processing unit 509 (S408). Then, the conversion unit 505 rewrites the carrier identifier in the synchronization signal (S410).

The time correction unit 504 determines whether the synchronization signal input from the slave processing unit 503 is synchronized with the external CLK serving as the master CLK (S412). If the time correction unit 504 determines that they are not synchronized (S412: No), the process proceeds to S414, and if it determines that they are synchronized (S412: Yes), the process proceeds to S416.

In the process of S414, the OLT 5 transmits the asynchronous state to the SNI port, for example, as CLK Class=248 in the PTP ANNOUCE message, and as QL-DUS in the SyncE ESMC message, for example.

In the process of S416, the section synchronization processing unit 508 of the OLT 5 transmits, for example, a PTP Delay Req message.

The slave processing unit 503 determines whether or not, for example, a PTP Delay resp message has been received from the SNI port (S418). For example, if the slave processing unit 503 determines that a PTP Delay resp message has not been received (S418: No), the slave processing unit 503 proceeds to the process of S420; for example, if it determines that a PTP Delay resp message has been received (S418: If Yes), the process advances to S422.

In the process of S420, the OLT 5 determines that it is in an asynchronous state, for example, as CLK Class=248 in the PTP ANNOUCE message, and as QL-DUS in the SyncE ESMC message, and proceeds to the process of S424.

In the process of S422, the time correction unit 504 compares the master CLK input from the master CLK distribution unit 502 and the synchronization signal input from the slave processing unit 503, corrects the time using the difference, and 505.

When the conversion unit 505 performs conversion to write back the identifier for identifying the carrier of the synchronization signal (S424), the slave processing unit 503 transmits the synchronization signal (S426).

In this way, the optical communication system 1 can reduce the number of optical fibers, and can efficiently distribute synchronization reference signals even when a plurality of base stations each using different synchronization reference signals are connected. Specifically, in the optical communication system 1, one OLT 5 can efficiently transmit and receive synchronization reference signals (synchronization signals) used by a plurality of carriers between the plurality of ONUs 7.

Note that each function of the base station base unit 2, base station slave unit 3, OLT 5, and ONU 7 is partially or entirely configured by hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array). It may be configured as a program executed by a processor such as a CPU.

For example, the optical communication system 1 according to the present invention can be realized using a computer and a program, and the program can be recorded on a storage medium or provided through a network.

FIG. 10 is a diagram showing an example of the hardware configuration of the OLT 5. As shown in FIG. As shown in FIG. 10, for example, the OLT 5 has an input section 900, an output section 910, a communication section 920, a CPU 930, a memory 940, and an HDD 950 connected to each other via a bus 960, and has a function as a computer. Further, the OLT 5 is capable of inputting and outputting data to and from a computer-readable storage medium 970.

The input unit 900 is, for example, a keyboard and a mouse. The output unit 910 is, for example, a display device such as a display. The communication unit 920 is, for example, an interface used for a wired network interface and a PON.

The CPU 930 controls each part constituting the OLT 5 and performs predetermined processing. The memory 940 and the HDD 950 are storage units that store data and the like. For example, the HDD 950 stores in advance a synchronization signal database 506 that includes different identifiers for each carrier, and an authentication database 507 that authenticates the ONU 7 and users.

The storage medium 970 is capable of storing programs and the like that cause the OLT 5 to execute functions. Note that the architecture configuring the OLT 5 is not limited to the example shown in FIG. 10. Further, the base station master device 2, the base station slave device 3, and the ONU 7 may also have the same hardware configuration as the OLT 5.

The term "computer" used herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable storage medium" refers to storage devices such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and other portable media.

Furthermore, a "computer-readable storage medium" refers to a storage medium that dynamically stores a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It may also include something that retains a program for a certain period of time, such as a volatile memory inside a computer that is a server or client in that case.

Although the embodiments of the present invention have been described above with reference to the drawings, it is clear that the above-described embodiments are merely illustrative of the present invention, and that the present invention is not limited to the above-described embodiments. be. Therefore, additions, omissions, substitutions, and other changes to components may be made without departing from the technical spirit and scope of the present invention.

1... Optical communication system, 2-1 to 2-3... Base station master unit, 3-1 to 3-3... Base station slave unit, 4-1 to 4-3... GMC, 5...OLT, 6...Optical splitter, 7-1 to 7-3...ONU, 8-1 to 8-3...TSC, 200...Master CLK supply unit, 202-1, 202-2... Master distribution unit, 500-1 to 500-3, 510... Interface (I/F), 501... Master CLK reception unit, 502... Master CLK distribution unit, 503-1 , 503-2... Slave processing unit, 504-1, 504-2... Time correction unit, 505-1, 505-2... Conversion unit, 506... Synchronization signal database, 507... Authentication database, 508-1, 508-2... section synchronization processing section, 509... synchronization signal processing section, 700, 706... interface (I/F), 701... section synchronization processing section, 702 ...Time correction section, 703...Conversion section, 704...Setting pattern database, 705...Master processing section, 900...Input section, 910...Output section, 920...Communication section , 930... CPU, 940... Memory, 950... HDD, 960... Bus, 970... Storage medium

Claims (5)

In an optical communication system, a synchronization signal is distributed via optical lines from an optical line termination device to which base stations of multiple carriers are connected to multiple optical network units.
The optical line termination device is
one or more slave processing units that process synchronization signals transmitted from each of the base stations as slaves;
a distribution unit that distributes one of the plurality of synchronization signals as a master clock;
one or more correction units that correct the synchronization signal processed by the one or more slave processing units based on the master clock distributed by the distribution unit;
one or more conversion units that convert the synchronization signal corrected by the correction unit so as to attach a different identifier to each carrier;
An optical communication system comprising: a synchronization signal processing unit that processes the synchronization signal converted by the conversion unit so as to transmit the synchronization signal converted by the conversion unit to the optical network unit that differs for each carrier via an optical line based on the identifier. The optical line termination device is
further comprising a storage unit that stores in advance a synchronization signal database including a different identifier for each carrier, and an authentication database for authenticating the optical network unit and the user;
The synchronous signal processing section
The optical communication system according to claim 1, wherein unicast transfer is performed based on the synchronization signal database and the authentication database. The synchronous signal processing section
The optical communication system according to claim 2, wherein a carrier is identified based on the synchronization signal database and the authentication database. The optical network unit includes:
The optical communication system according to any one of claims 1 to 3, further comprising a master processing unit that processes the synchronization signal transmitted from the optical line termination device so as to transmit it to each user. one or more slave processing units that respectively process synchronization signals transmitted from base stations of a plurality of carriers as slaves;
a distribution unit that distributes one of the plurality of synchronization signals as a master clock;
one or more correction units that correct the synchronization signal processed by the one or more slave processing units based on the master clock distributed by the distribution unit;
one or more conversion units that convert the synchronization signal corrected by the correction unit so as to attach a different identifier to each carrier;
An optical line termination device comprising: a synchronization signal processing unit that processes the synchronization signal converted by the conversion unit so as to transmit the synchronization signal converted by the conversion unit to a different optical network unit for each carrier via an optical line based on the identifier.

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