KR20150144273A - Wavelength tuning sequences for tunable ONUs in time and wavelength division multiplexing - passive optical network - Google Patents

Abstract

Disclosed is a method for changing a wavelength of wavelength-variable optical network unit (ONU) at a time and wavelength division multi-passive optical network (TWDM-PON). The wavelength changing method, according to an embodiment of the present invention, includes: a step for transmitting a wavelength change request message in which a source optical line terminal (OLT), providing service to the ONU through a first wavelength, requests for a wavelength change into a second wavelength serviced by a target OLT; and a step for the ONU to respond to the wavelength change request message, and transmits a wavelength change response message, regarding the possibility of the wavelength change, to the source OLT. The wavelength change request message performs as an identification information, including one among system ONU IDs, channel ONU IDs, and individual ONU IDs, in order to specify an ONU for performing the wavelength change.

Description

[0001] The present invention relates to wavelength tuning sequences for tunable ONUs and wavelength division multiplexing in passive optical networks,

The present invention relates to a time and wavelength division multiplexing passive optical network (TWDM-PON), and more particularly, to a time and wavelength division multiplexing-passive optical network As shown in FIG.

As a result of the development of optical communication technology and the rapid increase of Internet service demand, basic researches on the optical access network have been conducted since the early 2000s. As a result, FTTH (Fiber To The Home (FTTO), and Fiber To The Office (FTTO). At the same time, the proliferation of mobile IP terminals such as smart phones and tablet computers, the commercialization of IPTV services, and the proliferation of multimedia broadcasting / streaming services over the Internet, In order to cope with traffic increase, researches on next generation high-speed, high-capacity optical access network technology are being actively carried out.

Time Division Multiplexing (TDM) scheme and wavelength division multiplexing (WDM) schemes are applied to optical network technology to efficiently provide services to more subscribers with limited network resources have. Recently, researches on TWDM-PON link technology, in which TDM technique and WDM technique are applied together, are actively researched. The TWDM-PON link technology can satisfy the bandwidth expansion requirement of the network, provides a high-speed communication service to a large number of subscribers, and facilitates extension of the communication capacity and the number of subscribers.

1 is a diagram showing a schematic configuration of a TWDM-PON system. Referring to FIG. 1, a TWDM-PON system includes N optical line terminals (OLTs), optical distribution units (ODNs), and M optical network units (ONUs). The N OLTs share a WDM MUX for multiplexing downlink signals and transmitting the upstream signals to M ONUs and further separating upstream signals from M ONUs into corresponding OLTs. In this case, each ONU should be able to receive only downlink signals of wavelengths allocated thereto from wavelength multiplexed downlink signals, and to transmit uplink signals of a predetermined wavelength. Therefore, the ONU is equipped with a wavelength selectable transceiver, that is, a tunable transceiver.

The TWDM-PON link technology used in such a TWDM-PON system is based on the existing XG-PON (10gigabit-capable-PON) based frame technology and WDM capable of transmitting N (e.g., N can be 4 or 8) Technology to provide broadband services to subscribers. Utilizing the TWDM-PON link technology, it provides transmission bandwidth of 10Gbps downlink and 2.5Gbps upstream of WDM wavelength, and it can provide downlink 40Gbps and uplink 10Gbps transmission over link (N = 4).

In the TWDM-PON system, a procedure for wavelength change of the ONU is described through the ITU-T G.989.3 draft which is currently being standardized. Tuning_Control "," Tuning_Response "," US_WLCH_INFO ", and" Complete_d "are used to change the wavelength of the ONU and new wavelength recognition for the ONU. And so on. Further, a calibration mode field is newly defined in the existing "Serial_Number_ONU" PLOAM message for recognizing the upstream wavelength.

Using the wavelength change procedure of the ONU, the following services can be provided in the TWDM-PON system.

- Energy saving service: The TWDM-PON system can provide services to subscribers by operating only some wavelength channels among the available wavelength channels when the bandwidth used is small. If it is necessary to do so, a channel change is performed to the ONUs receiving the service using the wavelength channel that is not operated.

- Load Balancing Service: The TWDM-PON system allows the channel change to be performed so that some of the ONUs use different wavelength channels in order to provide quality of service when ONUs are concentrated in a specific wavelength channel.

- Protection switching service: The TWDM-PON system allows the ONUs that are using the wavelength channel to perform the channel change when a specific wavelength channel fails or the link fails.

- Multicast service: when it is necessary to assign the same wavelength channel to a plurality of ONUs requiring a multicast service, it is necessary to perform a change to a new channel for all the ONUs or to change the channel to some ONUs which are using different wavelength channels .

Depending on the type of service and / or service operation policy among the above services, only a part of ONUs may need to be changed, or all ONUs using the corresponding channel may have to change channels. Alternatively, there may be a case where the entire ONU of the TWDM-PON system needs to change the channel. For example, in the case of an energy saving service, a protection switching service, or a multicast service, the channel change of all ONUs using a specific channel may be required. However, in the current ITU-T G.989.3 draft, the ONU prescribes that the wavelength change procedure is individually performed, so that the entire ONU of the channel or the entire ONU of the system is inefficient to perform the channel change.

A problem to be solved by the present invention is to provide a wavelength changing procedure in which all ONUs of a system or all ONUs of a specific channel in the TWDM-PON system can efficiently change wavelengths.

According to an aspect of the present invention, there is provided a method of changing a wavelength of a wavelength tunable optical network unit (ONU) in a time division multiplexing and passive optical network (TWDM-PON) according to an embodiment of the present invention, Transmitting a wavelength change request message requesting a wavelength change to a second wavelength in which a source OLT provides a service, and transmitting the wavelength change request message to the ONU in response to the wavelength change request message And transmitting a wavelength change response message to the source OLT indicating whether or not the wavelength change is possible. The wavelength change request message includes one of a system ONU ID, an ONU ID for each channel, and an individual ONU ID as identification information for specifying an ONU to perform wavelength change.

According to an embodiment of the present invention, the wavelength change request message is a Tuning Control PLOAM message, the wavelength change response message is a Tuning Response Response PLOAM message, and the identification information may be included in an ONU-ID field of the Tuning Control PLOAM message. In this case, the Tuning Control PLOAM message may include a target wavelength field containing information of the second wavelength and a source wavelength field containing information of the first wavelength. The ONU compares the wavelength information contained in the source wavelength field with the wavelength information of the ONU and transmits the Tuning_Response PLOAM message only when the wavelength information matches the wavelength information.

According to another aspect of the present invention, the source OLT and the target OLT, which have received the wavelength change response message, periodically transmit a wavelength change acknowledgment message and uplink time allocation information, The source OLT and the target OLT may adaptively determine a period of transmitting the wavelength change acknowledgment message and uplink time allocation information based on the wavelength tuning time information.

For example, the wavelength change request message is a Tuning Control PLOAM message, the wavelength change response message is a Tuning Response (PLOAM) message, the wavelength tuning time information includes a PMD (Physical Media Dependence) tuning class information included in the Tuning_Response PLOAM message, Convergence layer tuning time information. The PMD tuning class information can be displayed using 2 bits according to the time required for wavelength tuning of the ONU. In this case, if the PMD tuning class information is '01', the source OLT and the target OLT transmit the wavelength change acknowledgment message and uplink time allocation information at a period of 125 μs, and if the PMD tuning class information is '10' The source OLT and the target OLT transmit the wavelength change acknowledgment message and the uplink time allocation information in a predetermined period in a range of 125 占 퐏 to 2ms and if the PMD tuning class information is 11, The target OLT transmits the wavelength change acknowledgment message and the uplink time allocation information in a predetermined period in a range of 2 ms to 100 ms and if the PMD tuning class information is '00', the source OLT and the target OLT transmit the wavelength change acknowledgment Message and uplink time allocation information may be determined based on the TC layer tuning time information. Also, the TC layer tuning time information can be displayed using a 2-byte value expressed in units of 125 mu s. And the wavelength of the light is changed.

As another example, the ONU may further include receiving a wavelength change acknowledgment message and uplink time allocation information from the target ONU, wherein the ONU includes a predetermined range of physical It is possible to find the physical synchronization signal of the second wavelength within the synchronization window. In this case, the physical synchronization window may have a range of 64 bits.

According to another aspect of the present invention, there is provided a method of changing a wavelength of a wavelength tunable optical network unit (ONU) in a time division multiplexing and passive optical network (TWDM-PON) Transmitting a wavelength change request message requesting a wavelength change to a second wavelength in which a source OLT provides a service, in response to the wavelength change request message Transmitting a wavelength change response message indicating whether a wavelength change is possible to the source OLT; and transmitting the wavelength change acknowledgment message and the upstream time allocation information periodically to the source OLT and the target OLT, Wherein the wavelength change response message includes wavelength tuning time information of the ONU, Target OLT may be the wavelength tuning time information to adaptively determine the frequency of transmitting the wavelength change confirmation message and an uplink allocation information based on the time.

According to the embodiments of the present invention described above, wavelength tuning procedures for a plurality of ONUs which are provided in the TWDM-PON system and / or a plurality of ONUs which are provided through a specific channel can be efficiently and rapidly performed have. And the transmission time allocation of the upstream signal can be dynamically adjusted based on the wavelength tuning performance of the ONU, for example, the time actually spent on the wavelength change. According to this, it is possible not only to significantly reduce the overhead on the OLT in changing wavelengths for a plurality of ONUs such as a system ONU or a channel-specific ONU, but also to satisfy the service quality of the link protection switching service In addition, energy saving can be achieved efficiently.

1 is a diagram showing an example of a configuration of a TWDM-PON system.
2 is a diagram showing a wavelength changing procedure described in the current ITU-T G.989.3 draft.
3 is a diagram showing a structure of a downward FS (Frmae Synchronization) frame described in the current draft ITU-T G.989.3.
FIG. 4 is a flowchart showing in more detail the process of steps S12 and S14 of FIG. 2 when the downlink FS frame of FIG. 3 is used.
5 is a diagram illustrating a configuration of a Tuning Control PLOAM message according to an embodiment of the present invention.
6 is a diagram illustrating an example of the structure of a downlink FS (Frmae Synchronization) frame according to an embodiment of the present invention.
7 is a diagram illustrating a configuration of a Tuning Response (PLOAM) message according to an embodiment of the present invention.
FIG. 8 is a flowchart illustrating a process of transmitting PLOAMu grant information and a Tuning Control (Confirm) PLOAM message according to an exemplary embodiment of the present invention. Referring to FIG.
9 is a diagram for explaining a PSync restoration procedure that can be applied to a wavelength tuning procedure according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The terms used in this specification are terms selected in consideration of functions in the embodiments, and the meaning of the terms may vary depending on the user, the intention or custom of the operator, and the like. Therefore, the meaning of the terms used in the following embodiments is defined according to the definition when specifically defined in this specification, and unless otherwise defined, it should be interpreted in a sense generally recognized by those skilled in the art. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the technical concept of the present invention unnecessarily obscure.

FIG. 2 is a block diagram of the ITU-T Recommendation G.989.3 (for Consent, 4), which is a draft of the current ITU-T G.989.3, more specifically G.989.3, which is being standardized in the ITU- April 2014). ≪ / RTI > The wavelength change procedure shown in FIG. 2 is a procedure in which the ONU 1 performs a service in the first OLT or the second OLT or OLT port 2 (OLT-port 2) at a wavelength? 1d, u at which the OLT- And the wavelength is changed by the provided wavelength? 2d, u.

2, an OLT-port 1 providing a service with a first wavelength lambda 1 d, u is a message requesting a wavelength change to a second wavelength lambda 2 d, u serving as a service of the OLT-port 2, I.e., a Tuning_Control (Request) PLOAM message to the ONU 1 (S10). In this case, the request message includes information (start count = 2 in FIG. 2) indicating the start point of wavelength change execution and information (? 2d, u in FIG. 2) for identifying a changed wavelength such as a wavelength number. Whether or not the message is sent to the ONU 1 is specified by the ONU-ID included in the Tuning_Control (Request) PLOAM message.

Upon receiving the request message from the OLT-port1, the ONU 1 determines whether the wavelength can be changed and transmits a response message including the determination result, i.e., a Tuning Response (ACK, NACK) PLOAM message to the OLT-port1 (S11). When the ONU 1 can perform the wavelength change request, it responds with a Tuning Response (ACK) PLOAM message. If it can not perform the wavelength change request, it responds with a Tuning Response (NACK) PLOAM message. . Upon receiving the response message from the ONU 1, the OLT-port 1 informs the OLT-port 2 of whether or not a response message is received (ACK notification).

2, the OLT-port1 and the OLT-port2 are connected to each other at a predetermined time interval (at a time point indicated by tuning starts here in Fig. 2) (downstream frame (Frame Synchronization) frame interval of 125us in Fig. 2) (PLOAM) grant information, which is time information allocated for a response of the ONU, together with a Tuning Control (Confirm) PLOAM message for confirming the wavelength change, for example, PLOAM grant information (S12). After ONU 1 transmits a Tuning Response (ACK) PLOAM message to OLT-port 1 in step S11, tuning of a Transmission Convergence (TC) layer is performed from the start point of wavelength change execution (S13). Tuning of the transmission convergence layer includes wavelength tuning (i.e., physical media dependence (PMD) tuning) for the wavelengths to be changed of the optical module and synchronization to the downlink channel, i.e., synchronization recovery at the physical layer. For wavelength tuning of the optical module, OLT-port1 and OLT-port2 allocate PLOAMu grant time to ONU1 every 125us cycles. When wavelength tuning of the optical module of the ONU 1 is completed, the ONU 1 obtains 64-bit physical synchronization (PSync) information and acquires synchronization for the downlink channel.

The ONU 1 that has completed the synchronization for the downlink channel recognizes the Tuning_Control (Confirm) PLOAM message and the PLOAMu grant time transmitted from the OLT-port 2, and responds to the OLT-port 2 with the Tuning_Response (Complete_u) PLOAM message (S14). Upon receiving the response message from the ONU 1, the OLT-port 2 stops the Tuning Control (Confirm) PLOAM message and the PLOAM grant time allocation and transmits the Complete_d PLOAM message to the ONU 1 (S15). When the ONU 1 receives the Complete_d PLOAM message from the OLT-port 2, the wavelength change procedure is completed. After that, the ONU 1 receives the service (transmission and reception of Downstream Data and Upstream Data) through the OLT-port 2 (S16).

3 is a diagram showing a structure of a downward FS (Frmae Synchronization) frame described in the current draft ITU-T G.989.3. Referring to FIG. 3, the downlink FS frame includes an FS header, an FS payload, and an FS trailer. The FS header includes a variable size two partitions, a bandwidth map (BWmap) field and a downward PLOAM (PLOAMd) field, together with a fixed size HLend structure. That is, the BWmap field and the PLOAMd field each include N (N is an integer of 1 or more) allocation structures and N Tuning Control (Request) PLOAM messages within the maximum size limit of the downlink FS frame.

In the downlink FS frame structure, when a wavelength change is requested to a plurality of ONUs, an OLT (OLT-port1 in the flowchart of FIG. 2) allocates as much as the number of ONUs requesting wavelength change to the BWmap field and the PLOAMd field, (Request) PLOAM message. Each of the allocation structure and the Tuning_Control (Request) PLOAM message includes ONU-ID, which is information for specifying an ONU targeted by the downlink FS frame. That is, the transmission of the Tuning Control (Request) PLOAM message transmitted in step S10 of FIG. 2 to the ONU 1 is specified through the ONU-ID. In order to identify an ONU to be a service target by using the ONU-ID and request a wavelength change to a plurality of ONUs, for example, 256 ONUs, time allocation information for receiving a Tuning Response (ACK, NACK) PLOAM message, Allocation structure information should be specified for ONUs, and 256 bytes of PLOAMd message must be included for transmission of the Tuning Control (Request) PLOAM message. As a result, the FS header uses 14,436 bytes to request wavelength change for 256 ONUs, which may result in downlink continuous mode data transmission.

FIG. 4 is a flowchart showing in more detail the process of steps S12 and S14 of FIG. 2 when the downlink FS frame of FIG. 3 is used. Referring to FIG. 4, a process of periodically transmitting PLOAMu grant information and a Tuning Control (Confirm) PLOAM message, which are time information allocated for a response of an ONU, in order to confirm whether a wavelength change procedure of an ONU is completed is shown in more detail . In FIG. 4, a source OLT-port indicates an OLT providing a service before a wavelength change as in the OLT-port 1 of FIG. 2, and a target OLT-port indicates a wavelength change To the OLT.

Referring to FIG. 4, the source OLT-port and the target OLT-port repeatedly transmit PLOAM grant information and a Tuning Control (Confirm) PLOAM message every cycle of 125 때 until the TC layer tuning time of the ONU is completed S12a). The ONU that has completed the synchronization for the downlink channel recognizes the Tuning_Control (Confirm) PLOAM message and the PLOAMu grant time transmitted from the target OLT-port, and responds to the target OLT-port with the Tuning_Response (Complete_u) PLOAM message (S14a).

As described with reference to FIG. 3, the TC layer tuning time of the ONU includes a time for requesting a wavelength change command from the ONU to the optical module, a tuning time of the optical module, and a time for searching for the Psync again in the channel in which the ONU is changed. The PLOAMu grant information and the Tuning_Control (Confirm) PLOAM message are included in the FS header for each of the corresponding ONUs. Accordingly, as the number of ONUs receiving the request increases, the area of the FS frame payload shown in FIG. 3 becomes smaller. In this case, it may cause an adverse effect on downlink service transmission, It is possible to waste up the transmission bandwidth of the uplink service.

Downward overhead and uplink overhead due to transmission including PLOAMu grant information and Tuning Control (Confirm) PLOAM message for each of a plurality of ONUs can be calculated as follows.

Downstream overhead = (8 bytes Allocation Structure + 48 bytes Tuning_Control) x number of ONUs x (TC layer tuning time / FS frame period)

Upstream overhead = (8 byte Allocation Structure) x number of ONUs x (TC layer tuning time / FS frame period)

In this way, when the wavelength tuning procedure shown in FIG. 2 is performed using the downlink FS frame of the structure shown in FIG. 3, the downward overhead and the uplink overhead increase as the number of ONUs increases. In order to perform the wavelength change for 256 ONUs, the number of ONUs allocated for the PLOAM grant is required as much as the number of ONUs. As a result, the overall time required to complete the wavelength tuning is increased. This may be a limitation in meeting a fast and stable service, for example, a service that requires protection switching within 50ms.

Next, the wavelength tuning procedure of the ONU according to the embodiment of the present invention will be described. The wavelength tuning procedure according to the embodiment of the present invention can basically be applied to the wavelength tuning procedure of the ONU described above with reference to FIG. However, as described later, in the embodiment of the present invention, the configuration of the Tuning Control PLOAM message, the operation mechanism of the ONU, the configuration of the Tuning Response PLOAM message, and the operation mechanism of the ONU and the OLT are different from the existing wavelength tuning procedure have.

5 is a diagram illustrating a configuration of a Tuning Control PLOAM message according to an embodiment of the present invention. The Tuning Control PLOAM message is a message transmitted from the source OLT-port to the ONU in order to confirm whether the wavelength channel is changed to the wavelength to which the target OLT-port provides the service or whether the wavelength channel is changed (S10 and S12 Reference). 5, the Tuning Control PLOAM message includes an ONU-ID field (octet 1-2), a message type field (octet 3), a sequence number field (octet 4), an operation code field (octet 5) octet 7-8, a downstream start count field octet 9-10, a rollback field octet 11, a target wavelength field octet 12, a source wavelength field octet 13, a padding field octet 14-40, And Message Integrity Check (MIC) fields (octets 41-48).

The configuration of the Tuning Control PLOAM message shown in FIG. 5 differs from that of the existing Tuning Control PLOAM message (see the above-mentioned current ITU-T G.989.3 draft) in the following points.

In the prior art, only a value for identifying or specifying one ONU in the 2-byte ONU-ID field, that is, an individual ONU ID is included. Here, the ONU-ID field contains ONU identification information for specifying an ONU to be subjected to wavelength change. On the other hand, according to the embodiment of the present invention, the ONU ID field, which is a value for specifying all the ONUs (hereinafter, referred to as 'system ONU') receiving service through the TWDM-PON system and / A channel-specific ONU ID, which is a value for specifying all ONUs (hereinafter, referred to as 'ONUs per channel') receiving a service through a channel, may be included. 5 shows a case where "0x3FF" is used as an example of a value indicating a system ONU and "0x3FE" is used as an example of a value for identifying an ONU for each channel.

Secondly, only one request mode is included in the operation code field of one byte. On the other hand, according to the embodiment of the present invention, the 1-byte operation code further includes a confirm mode. The confirm mode can be used to check whether the ONU has completed the change of the wavelength channel according to the Tuning_Control PLOAM message of the transmitted request mode (refer to S12 in FIG. 2).

Finally, the existing Tuning_Control PLOAM message did not include the source wavelength field. On the other hand, according to the embodiment of the present invention, the Tuning Control PLOAM message includes the source wavelength field. In Figure 5, one byte of the source wavelength field is shown as being included in the thirteenth octet of the Tuning Control PLOAM message, but this is only exemplary. The source wavelength field is for providing information on each of the down channel and the up channel of the source channel. For example, the lower 3 bits [2: 0] of the source wavelength field may be used to represent the value for the up channel and the upper 3 bits [6: 4] may be used to represent the value for the down channel.

Part of the wavelength tuning procedure using the Tuning_Control PLOAM message of this new configuration (steps S10 and S11 in FIG. 2) can be performed in the following manner.

1. Upon receipt of a Tuning_Control (Request) PLOAM message including 0x3FF in the ONU-ID field, all ONUs receiving services in the corresponding TWDM-PON system transmit Tuning_Response (ACK) to the source OLT- PLOAM message or a Tuning_Response (NACK) PLOAM message.

2. Upon reception of the Tuning_Control (Request) PLOAM message including 0x3FE in the ONU-ID field, all ONUs receiving the service from the source OLT-port transmit Tuning_Response (ACK) to the source OLT- PLOAM message or a Tuning_Response (NACK) PLOAM message. In this case, according to the embodiment, the ONU receiving the Tuning_Control (Request) PLOAM message with the ONU-ID of 0x3FE compares the source channel information included in the received message with its own channel information, It may respond to the source OLT-port using a Tuning_Response (ACK) PLOAM message or a Tuning_Response (NACK) PLOAM message depending on whether the wavelength can be changed or not.

3. Upon receipt of a Tuning_Control (Request) PLOAM message including an individual ONU-ID value in the ONU-ID field, only the corresponding ONU sends a Tuning_Response (ACK) PLOAM message or Tuning_Response (NACK ) PLOAM message.

FIG. 6 is a diagram showing an example of the structure of a downlink FS (Frmae Synchronization) frame according to an embodiment of the present invention. In the structure of the Tuning Control PLOAM message of FIG. 5, a system ONU or an ONU for each channel is indicated in an ONU- Value is included. 6, a downlink FS frame according to an embodiment includes an FS header, an FS payload, and an FS trailer, as in the conventional frame configuration (see FIG. 3) The FS header includes a variable size two partitions, a bandwidth map (BWmap) field and a PLOAMd field, together with a fixed size HLend structure.

However, when requesting a wavelength change to a system ONU or an ONU for each channel, the downlink FS frame according to an exemplary embodiment includes an allocation structure as much as the number of ONUs requesting wavelength change in the BWmap field, while one Tuning_Control Only PLOAM messages are included. That is, even if a plurality of ONUs are requested to change wavelengths, only one 48-byte Tuning Control PLOAM message is included in the PLOAMd field. In this case, one Tuning Control PLOAM message is a value indicating that the ONU-ID, which is the information for specifying the ONU targeted by the downlink FS frame, indicates the system ONU (this value is indicated by the broadcast ONU-ID in FIG. 6 ) Or a value indicating a channel-specific ONU. According to this, even if the wavelength change is simultaneously requested to 256 ONUs, only 2,030 bytes are included in the FS frame header, which can reduce the overhead of about 85% compared to the conventional method described with reference to FIG.

7 is a diagram illustrating a configuration of a Tuning Response (PLOAM) message according to an embodiment of the present invention. The Tuning_Response PLOAM message is a message transmitted by the ONU to the source OLT-port or the target OLT-port in response to the received Tuning Control PLOAM message (see S11 and S14 in FIG. 2). 7, the Tuning_Response PLOAM message includes an ONU-ID field (octet 1-2), a message type field (octet 3), a sequence number field (octet 4), an operation code field (octet 5) 6, the wavelength tuning result field octet 7, the target wavelength field octet 8, the tuning class field octet 9, the tuning time field octet 10-11, the padding field octet 24-40, Message Integrity Check) fields (octets 41-48).

The configuration of the Tuning_Response PLOAM message shown in FIG. 7 differs from that of the existing Tuning_Response PLOAM message (see the above-mentioned draft ITU-T G.989.3 draft) in that it includes a tuning class field and a tuning time field . The tuning class field includes the PMD (Physical Media Dependence) tuning class information of the ONU. This PMD tuning class information can be displayed using a predetermined number of bits according to the time or time range required for tuning, and can be displayed, for example, by two bits. FIG. 7 shows an example of displaying the PMD tuning class information with these two bits. The tuning time field may include the TC layer tuning time information of the ONU. For example, the TC layer tuning time information can be displayed using a 2-byte value in units of 125 microseconds. The PMD tuning class information and the TC layer tuning time information of this ONU can be used alone or together to indicate the wavelength tuning time of the ONU.

According to the present embodiment, the source OLT-port receiving the Tuning_Response PLOAM message of FIG. 7 from the ONU must deliver the received message or the information included therein to the target OLT-port. Accordingly, the target OLT-port can transmit PLOAMu grant information and Tuning Control (Confirm) PLOAM message at the same period as the source OLT-port. And

Part of the wavelength tuning procedure using the Tuning_Response PLOAM message of this new configuration (steps S11 and S12 in FIG. 2) can be performed in the following manner.

1. Upon receipt of a Tuning_Response (ACK) PLOAM message indicating "01" in the tuning class field in step S11 (corresponding to class 1 and less than 10 占 퐏 tuning time of the ONU in FIG. 7), the source OLT- And / or the target OLT-port periodically sends a PLOAM grant and a Tuning Control PLOAM message to the ONU at every 125 占 퐏 in step S12.

2. Upon receipt of a Tuning_Response (ACK) PLOAM message indicating "10" in the tuning class field in step S11 (which corresponds to class 2 and the ONU tuning time is in the range of 10 mu s to 25 mu s in FIG. 7) In step S12, the OLT-port and / or the target OLT-port periodically sends PLOAMu grant information and a Tuning Control PLOAM message to the ONU within a range of 125 mu s to 2 ms at predetermined time intervals.

3. Upon receipt of a Tuning_Response (ACK) PLOAM message indicating "11" in the tuning class field in step S11 (corresponding to class 3 and the ONU tuning time is in the range of 25 mu s to 1 ms in FIG. 7) -port and / or the target OLT-port periodically sends PLOAMu grant information and a Tuning Control PLOAM message to the ONU at a predetermined time interval within a range of 2 ms to 100 ms in step S12.

4. Upon receipt of a Tuning_Response (ACK) PLOAM message indicating "00" (corresponding to "Not Use" in the tuning class field) in step S11, the source OLT-port and / or the target OLT- Dynamically periodically sends PLOAMu grant information and Tuning Control PLOAM message to the ONU in step S12.  At this time, the time interval of sending the PLOAMu grant information and the Tuning Control PLOAM message can be determined by the source OLT-port and / or the target OLT-port based on the value displayed in the tuning time field. At this time, the tuning time value of the ONU can be counted by 1 every 125 μs as in the conventional case.

FIG. 8 is a flow chart specifically illustrating a process of transmitting PLOAMu grant information and a Tuning Control (Confirm) PLOAM message according to an embodiment of the present invention, wherein a Tuning_Response (ACK) PLOAM message with "11" Is received. The flowchart shown in Fig. 8 corresponds to the process of steps S12 and S14 of Fig. As described above, the PLOAM grant information includes time information allocated for a response of the ONU to check whether the wavelength change procedure of the ONU is completed.

Referring to FIG. 8, an ONU that has transmitted a Tuning Response (ACK) PLOAM message having "11" in the tuning class field has a TC layer tuning time of 1 second. The source OLT-port and the target OLT-port receiving this information periodically transmit PLOAMu grant information and a Tuning Control (Confirm) PLOAM message in a range of 2 ms to 100 ms until the TC layer tuning time (1 second) of the ONU is completed, (S12b). According to the conventional method (refer to FIG. 4), OLTs that do not refer to the TC layer tuning time of the ONU periodically transmit PLOAMu grant information and Tuning_Control (Confirm) PLOAM message every 125 us, As well as being able to utilize upstream resources efficiently. The ONU that has completed the synchronization for the downlink channel recognizes the Tuning_Control (Confirm) PLOAM message and the PLOAMu grant time transmitted from the target OLT-port, and responds to the target OLT-port with the Tuning_Response (Complete_u) PLOAM message (S14b).

9 is a diagram for explaining a PSync restoration procedure that can be applied to a wavelength tuning procedure according to an embodiment of the present invention. As described above, the ONU must complete the TC layer tuning in order to receive the PLOAMu grant information transmitted from the target OLT and the Tuning Control (Confirm) PLOAM message. The TC layer tuning of the ONU includes PMD tuning as well as physical synchronization recovery. The ONU's physical synchronization recovery process is a process of finding 64-bit Psync information. However, according to the existing method, that is, the method described in the draft ITU-T G.989.3, it is necessary to find the Psync information for a time of at least 250 μs. According to this, although the PMD tuning takes only several tens of microseconds, the total time required for tuning the TC layer of the ONU is at least several hundreds of microseconds. However, according to the embodiment of the present invention shown in FIG. 9, a PSync Window (POW) of 64 bits or less is set and the PSync recovery process searches 64 bits of Psync information in this interval . This utilizes the fact that the transmission time of the Psync information between the channels (λ1, λ2, λ3, λ4) is almost the same in the TWDM-PON system, so that 64 bits of PSync information You can find it quickly. According to the embodiment of the present invention, the time required for the physical synchronization restoration process can be shortened from a minimum of 250 μs to a maximum of 6.4 ns.

The above description is only an example of the present invention, and the technical idea of the present invention should not be interpreted as being limited by this embodiment. The technical idea of the present invention should be specified only by the invention described in the claims. Therefore, it is apparent to those skilled in the art that the above-described embodiments may be modified and embodied in various forms without departing from the technical spirit of the present invention.

Claims (12)

A method for changing wavelength of a wavelength tunable optical network unit (ONU) in a time-division multiplexed multi-passive optical network (TWDM-PON)
Transmitting a wavelength change request message requesting a wavelength change to a second wavelength at which a source OLT provides a service to a source optical line terminal (OLT) providing a service to the ONU with a first wavelength; And
Transmitting, by the ONU, a wavelength change response message to the source OLT indicating whether wavelength change is possible in response to the wavelength change request message,
Wherein the wavelength change request message includes one of a system ONU ID, an ONU ID for each channel, and an individual ONU ID as identification information for specifying an ONU to perform wavelength change. The method according to claim 1,
Wherein the wavelength change request message is a Tuning Control PLOAM message and the wavelength change response message is a Tuning Response Response PLOAM message,
Wherein the identification information is included in an ONU-ID field of the Tuning Control PLOAM message. 3. The method of claim 2,
Wherein the Tuning Control PLOAM message includes a target wavelength field containing the information of the second wavelength and a source wavelength field containing the information of the first wavelength. The method of claim 3,
Wherein the ONU compares the wavelength information contained in the source wavelength field with the wavelength information of the ONU and transmits the Tuning_Response PLOAM message only when the wavelength information matches the wavelength information. The method according to claim 1,
Further comprising the step of periodically transmitting the wavelength change acknowledgment message and the uplink time allocation information to the source OLT and the target OLT that have received the wavelength change response message,
Wherein the wavelength change response message includes wavelength tuning time information of the ONU, and the source OLT and the target OLT adaptively transmit the wavelength change acknowledgment message and the uplink time allocation information to the target OLT based on the wavelength tuning time information, Is determined as the wavelength of the light. 6. The method of claim 5,
Wherein the wavelength change request message is a Tuning Control PLOAM message and the wavelength change response message is a Tuning Response Response PLOAM message,
Wherein the wavelength tuning time information includes at least one of PMD (Physical Media Dependence) tuning class information and TC (Tunneling Convergence) layer tuning time information included in the Tuning_Response PLOAM message. The method according to claim 6,
Wherein the PMD tuning class information is displayed using 2 bits according to a time required for wavelength tuning of the ONU. 8. The method of claim 7,
If the PMD tuning class information is '01', the source OLT and the target OLT transmit the wavelength change acknowledgment message and uplink time allocation information at a cycle of 125 μs,
If the PMD tuning class information is '10', the source OLT and the target OLT transmit the wavelength change acknowledgment message and the uplink time allocation information in a predetermined cycle ranging from 125 μs to 2 ms,
If the PMD tuning class information is '11', the source OLT and the target OLT transmit the wavelength change acknowledgment message and the uplink time allocation information at a predetermined period in a range of 2 ms to 100 ms,
When the PMD tuning class information is '00', the source OLT and the target OLT determine a period for transmitting the wavelength change acknowledgment message and uplink time allocation information based on the TC layer tuning time information. How to change. The method according to claim 6,
Wherein the TC layer tuning time information is displayed using a 2-byte value expressed in units of 125 mu s. 6. The method of claim 5,
Further comprising the step of the ONU receiving a wavelength change acknowledgment message and uplink time allocation information from the target ONU,
Wherein the ONU finds the physical synchronization signal of the second wavelength within a predetermined range of the physical synchronization window based on the position of the physical synchronization signal of the first wavelength. 11. The method of claim 10,
Wherein the physical synchronization window has a range of 64 bits. A method for changing wavelength of a wavelength tunable optical network unit (ONU) in a time-division multiplexed multi-passive optical network (TWDM-PON)
Transmitting a wavelength change request message requesting a wavelength change to a second wavelength at which a source OLT provides a service to a source optical line terminal (OLT) providing a service to the ONU with a first wavelength;
Transmitting, by the ONU, a wavelength change response message to the source OLT indicating whether wavelength change is possible in response to the wavelength change request message; And
And periodically transmitting the wavelength change acknowledgment message and the uplink time allocation information to the source OLT and the target OLT, which have received the wavelength change response message,
Wherein the wavelength change response message includes wavelength tuning time information of the ONU, and the source OLT and the target OLT adaptively transmit the wavelength change acknowledgment message and the uplink time allocation information to the target OLT based on the wavelength tuning time information, Is determined as the wavelength of the light.

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