TW201308921A - Optical communication system, communication device and band control method - Google Patents

Abstract

Within the optical communication system according to the present invention, a portion of the nodes among ring nodes are acted as OLT for executing upload band allocation process with respect to ONU, and the nodes acted as OLT comprise a first band allocation function for distributing upload band allocated to the present system to each of the ONU groups, where the ONUs under the same remote node are treated as one ONU group, based upon the upload band allocation demand from each ONU and the number of ONU belonging each ONU group, and a second band allocation function for re-allocating the upload band distributed by the first band allocation function to each ONU within the group with respect to each ONU group based upon the upload band allocation demand from each ONU.

Description

Optical communication system, communication device and frequency band control method

The present invention relates to an optical communication system constructed by a one-to-many connection side device and a subscriber side device (joiner terminal device).

A PON (Passive Optical Network) in the form of an optical communication system is disposed in a central office (OLT: Optical Line Terminal) and in a plurality of subscribers' homes. The subscriber terminal device (ONU: Optical Network Unit) performs a one-to-many connection with a star type coupler and an optical fiber, and the upload direction (from the subscriber to the central office) The direction is to perform time-division multiplex communication, and the downlink direction is continuous communication. The PON is widely used in the form of an economical communication system (for example, refer to Non-Patent Document 1), and has a function of filtering an ONU identifier given by a frame on a ONU side by a frame. Thereby, one OLT is used to accommodate a plurality of ONUs. In addition, in recent years, standardization of a 10 Gbps class PON for the purpose of increasing the communication capacity of an access network has been completed (for example, refer to Non-Patent Document 2). This standard is a 10 Gbps version of a 1 Gbps PON specified by the conventional IEEE 802.3, and specifies an OLT capable of mixing and accommodating a conventional 1 Gbps EPON and a 10 Gbps 10G-EPON ONU, and an ONU accommodated in the OLT. The function implemented. Similarly, standardization of 10 Gbps PON is also being developed in ITU-T.

When applying these international standards, the communication speed of the PON interval will be It becomes 10 times, and in this case, two merits can be considered. The first advantage is that the communication career can use the number of subscribers per OLT to form the same number of subscribers as the PON of the 1 Gbps class, thereby increasing the communication capacity of each subscriber. And the subscribers benefit from the maximum capacity of the PON interval. The second advantage is that the communication provider can provide the subscriber with 1 Gbps while reducing the operating cost by accommodating each OLT subscriber to accommodate more than 1 Gbps PON. Level PON equivalent or higher level service (communication capacity).

In general, a 1 Gbps class PON star coupler can use a maximum of 32 divergence to 64 divergence. Although the divergence above this level, the optical transmission caused by the difference between the communication capacity and the star coupler Road losses are almost impossible to achieve, but the number of differently divided ONUs has been reviewed since the beginning. For example, Patent Document 1 discloses a multi-division method in which a plurality of PON signals having different wavelengths disposed by a plurality of office-side devices installed in a central office are connected to perform multiplexing or for each wavelength thereof. Performing a split-wave WDM coupler, and multiplexing the wavelength-multiplexed signal at the WDM coupler with one fiber and a star coupler to a complex number of PON signals capable of transceiving wavelengths corresponding to a particular office-side device A transponder is connected, and the transponder and the plurality of ONUs are connected by one fiber and a star coupler, and the PON signal is transmitted and received in a time-sharing manner in the uploading direction.

Also, when considering the effective use of a 10 Gbps class PON device, it is more desirable to increase the number of communication per 1 compared to considering only the communication speed per 1 joiner. The number of participants in the OLT is increased, and the operating cost of the communication provider is reduced, and the degree of satisfaction of the subscriber is also improved.

Applicable to such an application form, and more entrants share the OLT, and as a result, it is closely related to reducing the power consumption of the OLT (the total power consumption of all OLTs on the local side), and also conforms to the low power consumption that is expanding in the world. The trend.

However, only the regulation specified by the international standard of 10 Gbps (the above-mentioned non-patent document 2) deteriorates the transmission quality due to the multi-division, and the distance between the central office and the subscriber's home in the current service cannot be shortened. It is difficult to achieve multiple divergence. For example, although it is also considered to increase the power of the transmitter of the OLT or the ONU, or to insert an amplifier in the optical fiber, etc., to simultaneously coexist the service distance and the multi-diversity method, when the transmission power of the OLT or the ONU changes When the time is high, the following operation or technical problem occurs: the hazard level of the access fiber laying operator becomes high, or it is difficult to use the amplifier to amplify the burst signal of the uploading direction. Wait.

Further, in the method disclosed in Patent Document 1, since the configuration of the office side device is different from the configuration of the prior art, and the transponder is newly inserted, it is possible to divergence, but it is difficult to reduce power consumption. The problem. Moreover, as a common problem in the conventional method, since the central office device and the subscriber device are connected by one optical fiber when the plurality of subscribers are served by one OLT, the central office device or the optical fiber (especially the trunk line) When there is a failure, there is a problem that the area of the obstacle is enlarged.

Therefore, in order to solve the problem as described above, the purpose is to provide a In a PON device of 10 Gbps or higher, while allowing the increase in the number of subscribers per OLT (multiple divergence), power is saved, and a redundant subscriber accommodating device can be obtained, and it is revealed that A method in which an OTN technology and a PON technology are combined to concentrate more than a conventional ONU on one OLT (for example, Non-Patent Document 3).

[Previous Technical Literature]

(Patent Document 1) Japanese Patent Laid-Open Publication No. 2008-206008

(Non-Patent Document 1) IEEE802.3

(Non-Patent Document 2) IEEE802.3av

(Non-Patent Document 3) IEICE Technical Report CS2010-9 (2010-7)

In the above non-patent document 3, a method of concentrating a PON function on an OLT and directly accommodating a signal of a PON in an OTN (Optical Transport Network) signal and transmitting and receiving the same is disclosed. A method of divergence, extension, improved network reliability, and low power consumption. However, in the prior art, there are methods, methods, and means for connecting an optical transmission network to a frequency band control of an access area network by an OLT (hereinafter referred to as a centralized OLT) disposed on an optical transmission network. Question. That is, in order to individually perform band control by the optical transmission network (memory network) and the access area network, if the transmission is performed from the access area network to the optical transmission network in a long period of time ( Traffic does not increase this level, but there will be an instant concentration of uploading traffic from the access area network. However, congestion occurs, and some of the traffic is discarded, and the problem of efficient use of the upload band cannot be achieved.

The present invention has been developed in view of the above problems, and an object thereof is to obtain a centralized OLT for connecting a metro network to an access network of an access network, and efficiently An optical communication system, a communication device, and a band control method using an upload band.

In order to solve the above problems and achieve the object, the present invention provides an optical communication system, which is characterized in that it comprises a plurality of ring nodes, a remote node and an ONU, and the plurality of ring nodes form a ring. And extracting signal light of a specific wavelength from the ring network and outputting to other nodes that do not form the ring network, and outputting signal light input from the other node to the ring network; The end node acts as the other node; the ONU is connected to the remote node through an optical coupler, and a part of the nodes on the ring is regarded as an OLT that performs processing for allocating an upload band to the ONU. The node operating as the OLT has a first band allocation function, and the ONUs under the same remote node are treated as one ONU group, and are assigned to the local system for uploading. The frequency band is allocated to each of the ONU groups based on the number of uplink bandwidth allocation requests from each ONU and the number of ONUs belonging to each ONU group; and the second band allocation function for each of the aforementioned ONU groups The upload band allocated by the first band allocation function is redistributed to each ONU in the group based on the upload band allocation request amount from each ONU.

According to the present invention, a plurality of remote nodes can share the same wavelength, and the frequency band in the ring can be dynamically allocated to a plurality of remote nodes in a manner of being linked to the amount of the frequency band allocated to the ONU, and can be compared with the conventional ones. The repeater network that allocates frequency bands in a quasi-static manner also has a soft access to the fusion type band allocation. As a result, it is obtained that an optical communication system that prevents congestion in the transmission path with the upper network and can efficiently utilize the upload band can be realized.

Hereinafter, embodiments of the optical communication system, the communication device, and the band control method of the present invention will be described in detail based on the drawings. Further, the present invention is not limited to the embodiment.

Embodiment 1. <System Composition>

First, the overall structure of the system will be explained. Fig. 1 is a view showing a configuration example of an optical communication system of the present invention. As shown in the figure, the optical communication system includes: a ring network formed by connecting a plurality of nodes (the OLT1 and the nodes 2 ₁ to 2 _n on the ring) to the duplexed fiber (the trunk fiber); The duplexed fiber is connected to the remote nodes (RN) 3 ₁₁ to 3 _1p , 3 ₂₁ to 3 _2q , ..., 3 _n1 to 3 _nr of the nodes 2 ₁ to 2 _n on the ring; and through the optical fiber and the optical coupler The (32 divergence coupler) 4 is connected to the ONU of the RN (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G.1G-ONU5 ₁₀₁ ). In addition, 10G-ONU5 _{10 is an} ONU capable of transmitting 10 Gbps of communication up and down bidirectionally (for example, as defined by IEEE 802.3av), and 1G-ONU 5 _{1 is an} ONU capable of transmitting 1 Gbps of communication up and down bidirectionally (for example, by IEEE 802. 3 stipulated), 10G. The 1G-ONU5 _{101 is an} ONU capable of uploading 1 Gbps and transmitting 10 Gbps of communication (for example, as defined by IEEE 802.3av). In the following description, when "ONU" is simply described, 10G-ONU5 ₁₀ , 1G-ONU5 ₁ and 10G are displayed. 1G-ONU5 ₁₀₁ . Further, an RN may be connected to the OLT 1 corresponding to the centralized OLT described above, and various ONUs may be connected to the RN. In the present embodiment, the case where the photocoupler 4 is a 32-difference coupler will be described, but other divergence numbers may be used. In addition, in FIG. 1, the communication means of the metropolitan area network is an OTU (Optical-Channel Transport Unit) frame (a frame used in the OTN) by continuous optical WDM. Transmission, but this is a purely illustrative illustration to aid in understanding the principles of the invention, and is not intended to limit the means of communication in the network in the network. The physical layer may also be, for example, OFDMA communication or digital coherent communication if it is a communication method that achieves the same effect.

In the optical communication system shown in FIG. 1, the OLT 1 is a communication device that connects the upper network and the ring network, and has a multiplex separation unit, two redundant OLT-IFs, a monitoring control unit, and ROADM (Reconfigurable Optical Add/Drop Multiplexer). Each of the nodes on the ring is a communication device having the same configuration, and has a ROADM unit, an OTN-XC (OTN Cross Connect) unit, and a repeater. Each RN is a communication device having the same configuration, and has a repeater and a monitoring control unit. In addition, OLT1 is in addition to the functions of the nodes on each ring. In addition, a communication device that functions as an OLT of a PON is also provided. The optical communication system according to the present embodiment is a communication device below the node on each ring (in the first figure, the location where each RN is placed) The OLT function (the function that operates as an OLT) that the communication device has is concentrated on one ring node and acts as an OLT1. In the optical communication system shown in Fig. 1, since the nodes on the respective rings have the OTN-XC unit, the same wavelength can be shared by a plurality of nodes on the ring.

In the multiplex separation unit of the OLT 1, the downlink signal light (frame) received from the upper network is output to either of the two OLT-IFs, and the uplink signal received from the OLT-IF is received. The light is output to the upper network. The OLT-IF performs various processes for the OLT to operate as a station side device of the PON. Further, one of the two OLT-IFs is set in the active system, and the other is set in the standby system. The monitoring control unit performs monitoring (fault detection) in the communication system and path switching in the case of failure detection. The ROADM unit of the OLT 1 and each ring node performs extraction and addition of a specific wavelength (output to the ring network) for a signal (light) flowing through the ring network. The transponder of each node on the ring performs wavelength conversion of the received signal light. Although the transponders of the RNs also perform wavelength conversion of the received signal light, in the uploading direction, a plurality of optical burst signals having different communication speeds are terminated and converted into at least one for communication between the RN and the OLT1. Processing of optical continuous signals of wavelengths above 1 wave. On the other hand, in the downlink direction, the signal of each transponder is extracted from the signal of the predetermined communication wavelength determined in advance by each RN, and the predetermined frame format is utilized by the wavelength inherent to the PON specified by the standard specification ( Frame format) To send a communication signal.

OLT1 and RN3 ₁₁ to 3 _1p (p is the number of RNs connected to the lower layer of the node 2 ₁ on the ring), RN3 ₂₁ to 3 _2q (q is the number of RNs connected to the lower layer of the node 2 ₂ on the ring), RN3 _n1 to 3 _nr ( r is the number of RNs connected to the lower layer of the node 2 _n on the ring), and is connected by more than one ring node 2 ₁ to 2 _n (n is the number of nodes on the ring constituting the ring network), and The communication speed between the RN and its lower ONUs (10G-ONU5 ₁₀ , 1G-ONU5 ₁ , 10G.1G-ONU5 ₁₀₁ ) and the high-speed transmission speed depend on the OTU frame transmission of the continuous optical WDM, thereby performing communication. On the other hand, the transponders accommodated in each RN and the ONUs connected to the lower layer are connected in a star topology like a conventional PON, and communicated by a conventional TDMA-PON method.

In the present embodiment, for simplification of description, an optical communication system in which one OLT function is integrated among nodes (communication devices) constituting a ring network is assumed as shown in FIG. . However, focusing on one node is not necessary. It can also be distributed over a part of the nodes to have OLT functionality.

<Overview of the composition and control of the OLT, the ring node and the remote node (RN)>

Figure 2 shows OLT1, ring node 2 (nodes 2 ₁ , 2 ₂ , ..., 2 _n on the ring) and RN3 (RN3 ₁₁ to 3 _1p , ..., RN3 _n1 to 3 _nr ) shown in Fig. 1 A diagram of the main points of the control method of the whole system. Here, as an example, it is assumed that in the present communication system, the OLT-IF performs all band allocation control in the system. Further, the OLT-IF performs band allocation control of a PON control protocol based on the IEEE standard between the RN and the ONU. In addition, in the second drawing, although the number of nodes on the ring 2 is one, as shown in Fig. 1, there are actually a plurality of stations. Since each RN3 has the same configuration, only one internal display configuration is shown, and the rest is omitted.

The OLT 1 includes the OLT-IF 11, the monitoring control unit 12, and the ROADM unit 13 as main components. In addition, for simplification of description, only one of the two OLT-IFs that have been redundant (set to the side of the active system) is described as the OLT-IF 11. Further, the description of the multiplex separation unit is omitted. The OLT-IF 11 includes a high integrated PON control unit, and is composed of an IF unit 111, an OTN mapper/demapper unit 112, a SER/DES unit 113, and an upload band allocation control unit 114; OptTRx section 115. The IF unit 111 is an interface with a multiplex separation unit (not shown). The OTN mapper unit/demapper unit 112 performs a process of multiplexing the main signal input from the IF unit 111 and the control signal input from the upload band allocation control unit 114, and the slave SER/ The process in which the main signal and the control signal of the multiplexed state input from the DES unit 113 are separated. The SER/DES unit 113 performs processing of converting serial data input from the OTN mapper unit/demapper unit 112 into parallel data, and from the OptTRx unit 115. The processing of inputting parallel data into serial data. The upload band allocation control unit 114 performs band allocation control in the metropolitan area network and the access area network. The OptTRx unit 115 performs transmission and reception of optical signals.

The monitoring control unit 12 performs monitoring in the communication system as described above. View (fault detection) and path switching (light path switching control) during fault detection. As described above, the ROADM unit 13 extracts and adds a specific wavelength (output to the ring network) for a signal (light) flowing through the ring network.

The ring node 2 includes the ROADM unit 21 and the OTN-XC unit 22 as main components. In addition, the description of the repeater is omitted. Similarly to the ROADM unit 13 of the OLT 1, the ROADM unit 21 extracts and adds an optical signal of a specific wavelength to a signal flowing through the ring network. The OT N-XC unit 22 has a function of temporarily converting a signal of a specific wavelength extracted by the ROADM unit 21 into an electric signal, and converting the signal to be transmitted to the RN 3, and then converting the signal into an optical signal and transmitting the same; The received signal of each RN3 in the connection is a function of placing light of the same wavelength and transmitting it to the optical transmission network side according to an indication from the OLT-IF.

The RN 3 includes an OptTRx unit 31, an OTN mapper/demapper unit 32, and a plurality of burst transponders 33 (hereinafter simply referred to as a repeater 33). In addition, the description of the monitoring control unit is omitted. Further, the configuration of each transponder 33 is the same. Therefore, the internal configuration is displayed only for one transponder 33, and the rest is omitted.

The OptTRx unit 31 performs transmission and reception of optical signals between the nodes 2 on the ring. The OTN mapper/demapper unit 32, in the upload direction (toward the node 2 on the ring), generates a frame that masks the input signals from the transponders 33 and processes them at the OTN (OTU frame) And output to the OptTRx section 31. On the other hand, in the down direction, proceed from OptTRx The OTU frame input by the unit 31 is decapsuleized, and the resulting signal of each transponder 33 is output to the corresponding transponder 33.

The repeater 33 includes an RTT management unit 331, a DOB CDR unit 332, a DOB Rx unit 333, a time stamp processing unit 334, a 1G/10G OptTx unit 335, a WDM coupler 336, and a local timer. 337. The RTT management unit 331 measures the RTT of the PON area (between the local device (the local repeater) and the lower ONUs), and manages the measurement result. Further, the OLT 1 in the management is notified of the RTT in management. The DOB CDR unit 332 and the DOB Rx unit 333 receive the uplink signal light having a communication speed of 1 Gbps and 10 Gbps via the WDM coupler 336, specifically, the received two-wavelength signal transmitted from the ONU, and the reproduction is performed as 1 Gbps and 10Gbps continuous signal. The time stamp processing unit 334 gives a time stamp indicating the time managed by the local timer 337 to the PON control frame generated by the OTN mapper/demapper 32 based on the control signal from the OLT. The 1G/10G OptTx unit 335 performs wavelength conversion on the frame (1 Gbps and 10 Gbps PON frame) input from the time stamp processing unit 334, and transmits it to the connected star coupler (optical coupler) through the WDM coupler 336. 4) The fiber side. Further, in the PON control frame input to the 1G/10G OptTx section 335, a time stamp indicating the time managed by the local timer 337 is embedded. The local timer 337 is constructed by a 32-bit granular counter that is available for use by the PON control standard and manages the local time of each repeater.

In each of the RNs configured as described above, the frame processing in the downward direction is performed. In the process, each transponder 33 recognizes the MPCP frame, and hereby gives a time stamp indicating the time (local time) managed by the local timer 337 of each transponder 33, and performs the information in the Gate frame. Correction. On the other hand, in the frame processing operation in the upload direction, each transponder 33 calculates the local timer value managed by the local timer 337 and the time stamp value printed in the received MPCP frame. The RTT of each logical link is maintained. Further, in Fig. 2, although the configuration example in which each of the transponders 33 is provided with the local timer 337 has been displayed, the transponder 33 or the RN 3 may be provided with a local timer and managed in accordance with the local timer. The transponder is activated at all times. In this way, the TDM-PON-specific time synchronization is controlled between the ONU 5 and the RN 3, and the PON control represented by the ONU Discovery or the band allocation control is concentrated on the OLT-IF 11 of the OLT 1. In other words, in the OLT 1 as the centralized OLT, although the control of the Discovery of the ONU 5 or the calculation of the allocation amount of the upload band to the ONU 5 is performed, the portion related to the time synchronization or the timing of the connection distance depending on the ONU 5 is terminated at the RN 3 . And centralize the main functions of PON control. Even in the case of such control, the bandwidth requirement of the ONU 5 is transmitted to the OLT-IF 11, so that the OLT-IF 11 can grasp the bandwidth requirement of the entire network, and can perform the connection in the following manner. Band allocation control.

<Dynamic band allocation method for the metropolitan area associated with the band control of the access zone>

In the optical communication system of the present embodiment, the OLT-IF11 of the OLT1, When the upload band is allocated to each ONU 5, the band allocation of the metropolitan area is first performed, and after this is completed, the band allocation of the access section is performed. In the frequency band allocation of the metropolitan area, the ONUs 5 accommodated in the same RN3 are treated as one group, and according to the uploading band requirements from each group (according to the uploading band required by the ONU 5 of the same group) The sum of the ONUs 5 belonging to each group, etc., and determining how to allocate the upload frequency bands allocated to the system to each group. Hereinafter, the band control method of the access section will be described in detail.

First, a method of setting a band allocation update period of a metropolitan area (a section between OLT1 and each RN3) will be described. Fig. 3 is a view showing an example of a method of setting a band update period in a metropolitan area. In this method, attention is paid to the fact that since the frequency band allocation of the metropolitan area can be expected to be statistically multiplexed, it is not necessary to perform dynamic allocation control by a shorter band update period as in PON control. Therefore, the OLT 1 is characterized in that a plurality of band update periods in the PON section (the section between each of the repeaters 33 and the ONUs 5 of the RN 3) are continuously monitored (monitor) the ONU requirement amount (REPORT amount) in the lower layer of each RN3. And calculating the integrated value of the band requirement amount by setting the obtained metropolitan area band allocation period L in a period longer than the band update period (the illustrated PON band allocation period I) of the PON section, and calculating the integrated value of the band requirement amount based on the integrated value The amount of band allocation within the metropolitan area network. In addition, although the band allocation period (L) in the metropolitan area network in FIG. 3 is a fixed period, it is also possible to change each period by monitoring the amount of fluctuation of the traffic. In this case, the minimum period of the band update period (the metropolitan area band allocation period) in the metropolitan area network is the band update period (PON) with the PON section. Band allocation period) the same period. As an example, the following control may be performed: in the temporary state in which the metropolitan area band transitions from the non-congested state to the congested state (or vice versa), the metropolitan area band allocation period L is shortened to improve the bandwidth allocation control pair access interval of the metropolitan area The tracking amount of the traffic increase is small, and in the state where the change of the traffic is small, the metropolitan area band allocation period L is set longer to reduce the processing amount of the OLT1.

Next, the band allocation method for the metropolitan area (the OTN-XC unit 22 of the node 2 on each ring) and the access section (each ONU 5) will be described with reference to Figs. 4 to 7 as a reference. In the following, in order to facilitate the understanding of the principle of the band allocation method of the present embodiment, a case where one RN 3 is connected to the ONT-XC unit 2 will be described. However, even when a plurality of RNs 3 are connected to the OTN-XC unit 2, the band allocation amount can be calculated in the same manner. Further, although the case where the RN 3 connected to the OLT 1 is not present has been described, the band allocation amount can be calculated in the same manner even when the RN 1 is connected to the OLT 1.

Fig. 4 is a flow chart showing an example of the overall operation of the band allocation control, and Fig. 5 and Fig. 6 are flowcharts showing an example of band allocation control for RN3, and Fig. 7 shows the case for each forwarding. A flowchart of an example of band allocation control of the unit 33.

As shown in FIG. 4, the band allocation control performed by the OLT 1 in the optical communication system according to the present embodiment includes RN _i band allocation processing (BW _i calculation) as a band allocation process for each RN 3; The transponder band allocation process (bw _ij calculation) of the band allocation process of the repeater 33; and the GNU band allocation process (calculated by nu_bw _ijk ) as the band allocation process for each ONU 5. Further, in the OLT 1, the upload band allocation control unit 114 performs band allocation.

In the band allocation control shown in Fig. 4, when the processing is started, it is confirmed whether or not the metropolitan area band period timer is full, that is, whether or not the metropolitan area band allocation period L shown in Fig. 3 has elapsed (step S1). When the metropolitan area band period timer is not full (step S1: NO), it is confirmed whether or not the access area band period timer is full, that is, whether the PON band allocation period I shown in Fig. 3 has elapsed (step S3). On the other hand, when the metropolitan area band period timer is full (step S1: YES), it is confirmed whether or not the pick-up area band allocation period timer is full after execution of the RN _i band allocation processing described later (step S2 → S3). . When the access zone band allocation cycle timer is not full (step S3: NO), the process returns to step S1 and it is confirmed whether the metro zone band cycle timer is full. On the other hand, when the access zone band cycle timer is full (step S3: YES), the repeater band allocation process and the ONU band allocation process described later are executed (steps S4 to S5), and the process returns to step S1. OLT1 performs band allocation control in this order and links the metropolitan area network to the band control of the access area network to achieve efficient utilization of the upload band.

Next, the band allocation method of the metropolitan area (the RN _i band allocation process of the above step S2) will be described using FIG. 5 and FIG. In addition, both FIG. 5 and FIG. 6 are diagrams showing an allocation band allocation method for RN3, and exclusively use this as the RN _i band allocation process of step S2. First, the processing shown in Fig. 5 will be described.

In Fig. 5, it is assumed that "B" indicates the maximum frequency band of the optical path, "Req(i, k)" indicates the upload band requirement amount of ONU _k from RN _i , and "N _i " indicates that it is connected to RN _i The number of users (the number of ONUs 5), "BW _i " indicates the allocated band for RN _i , and "L" indicates the band update period for the metropolitan interval. The number of RN3s in the system is n+1, and OLT1 performs the processing of steps S11 to S16 individually with respect to n+1 RN3 to determine the upload band BW _i assigned to each of RN3. In addition, the maximum frequency band B of the optical path refers to the maximum frequency band of the optical path between the OLT 1 and the upper network.

In the band allocation processing for RN3, it is first confirmed whether or not Σ _i Σ _k Req(i, k) [bit] / L [sec] ≦ B [bps] (where i = 0, 1, ..., n), That is, the time average value (hereinafter, referred to as "total required amount average value") in the metropolitan area band allocation zone period L based on the sum of the required upload band requirements of all ONUs 5 in the system is the maximum band B of the optical path. The following (step S11).

If the total required average value is below the maximum frequency band B (step S11: YES), the allocated frequency band BW _i for the i-th RN3 is determined as Σ _k Req(i, k) [bit] / L [sec], and The range of i=0 to n performs a process of setting the value of i to increment (steps S12 and S17). That is, in the metropolitan area band allocation period L, the time-averaged value based on the sum of the required amount of the upload band required by each ONU 5 of the lower layer of the i-th RN3 is regarded as BW _i . This shows that the frequency band is allocated as if it were required according to the upload band required by all ONUs 5 of the lower layer of the i-th RN3.

On the other hand, when the total required amount average exceeds the maximum band B (step S11: No), the allocated band BW _i for the i-th RN3 is temporarily determined as Σ _k Req(i, k) [bit] / L [sec] ] (step S13). Then, it is confirmed whether or not BW _i >N _i ×B/Σ _i N _i , that is, whether the temporarily determined BW _i is larger than the frequency band in which the maximum band B ratio is allocated to each RN 3 in accordance with the number of ONUs in the lower layer of each RN 3 ( Step S14).

When BW _i >N _i ×B/Σ _i N _{i is} established (step S14: YES), the maximum band B ratio is allocated to the frequency band of each RN3 in accordance with the number of ONUs in the lower layer of each RN3, N _i × B / Σ _i N _{i is} regarded as BW _i (step S15). That is, N _i × B / Σ _i N _{i is} assigned to the i-th RN3. On the other hand, when BW _i >N _i ×B/Σ _i N _{i is} not satisfied (step S14: NO), BW _i temporarily determined in the above-described step S13 is regarded as the final BW _i (step S16). That is, for the i-th RN3, the frequency band is allocated in the same manner as the required amount of the upload band required by all the ONUs 5 of the lower layer of the i-th RN3. After determining the allocated frequency band BW _i for the i-th RN3, the value of i is incremented (step S18), and if there is RN3 for which the frequency band is not allocated, the processing of steps S11 to S16 described above is repeated.

As described above, in the frequency band allocation for the metropolitan area, it is determined whether or not congestion occurs in the OLT 1 (the transmission path from the OLT 1 to the upper network), and if there is no congestion, the band from each ONU 5 is used. The frequency band corresponding to the sum of each RN3 of the required amount (the band requirement amount from the group of ONUs 5 below the RN3) is allocated to each RN3. On the other hand, if congestion occurs, it is determined whether or not congestion occurs when the maximum frequency band B is allocated to each RN 3 in accordance with the number of ONUs in the lower layer of each RN 3, and if congestion does not occur, The frequency band identical to the sum of the bandwidth requirements of the ONUs 5 from the lower layers of the RN3 is allocated to the RN3, and when there is congestion, the allocation is performed when the maximum frequency band B is allocated to each RN3 according to the number of ONUs of the lower RN3. The frequency band corresponding to the value. In other words, when there is congestion in the OLT 1, the frequency band when the maximum frequency band B is allocated to each RN 3 in accordance with the number of ONUs in the lower layer of each RN 3 is taken as the upper limit, and the sum of each RN 3 from the bandwidth requirement of the ONU 5 is used. The amount of allocation to the frequency band of each RN3 is determined. Therefore, for all RN3s, even if the total value of the band request amount from the lower layer ONU5 exceeds N _i × B / Σ _i N _i (= the maximum band B is allocated to each of the ONUs of the lower layers of each RN3) In the state of the value of RN3), the allocated frequency band BW _i for each RN 3 also becomes N _i × B / Σ _i N _i , and the sum of the allocated frequency bands BW _i for each RN 3 can be suppressed to the maximum frequency band of the optical path. B below. As a result, congestion can be prevented from occurring in the OLT 1, and the abandonment of the uploading of the traffic can occur.

Further, in the above method, as a result of allocating a frequency band to all RNs 3, when a residual frequency band occurs, the residual frequency band may be divided by the number of RN3 and equally distributed to each RN3. In addition, all the residual frequency bands may be provided to the RN, and are provided to each RN3 in sequence in each frequency band update period (the metropolitan area band allocation period). Also, the residual frequency band can be preferentially supplied to the RN 3 in the congestion (assuming RN3 of BW _i =N _i ×B/Σ _i N _i ). Further, it is also possible to allocate a residual band to the RN 3 having the smallest band allocation amount. When the residual frequency band is allocated to the RN 3 in congestion, the frequency band utilization efficiency can be further improved.

Further, in the above-described control shown in FIG. 5, although the BW _i =N _i ×B/Σ N _i (bps) control is uniformly provided for the RN 3 in the congestion, the control shown in FIG. 6 may be used. . The control shown in FIG. 6 adds a step S21 for calculating the congestion control amount x _i (t) as the frequency band allocated to the RN 3 in the congestion, and uses it as a decision to determine for the control shown in FIG. In the process of congestion of the allocated band BW _i of the RN 3, step S22 is performed instead of step S15. According to this control, the OLT 1 calculates the congestion control amount x _i (t) of each RN in advance, and performs band allocation based on the congestion control amount.

In step S21 shown in Fig. 6, the congestion control amount x _i (t) is calculated according to the following equation (1). In addition, "x _i (t) [bps]" displays the amount of congestion control for the current period of RN _i , and "y _i (t) [bps]" displays the average of RN _i up to the previous period. The band allocation amount, "y0 _i [bps]", shows the target value of the band allocation amount for RN _i . Further, it is assumed that: Δy _i (t) = y _i (t) - y0 _i , y0 _i = N _i × B / Σ Ni. The K _P system displays the proportional gain (gain), the K _I system shows the integral gain, and the K _D system shows the differential gain.

In the control shown in Fig. 6, when BW _i >N _i ×B/Σ _i N _{i is} established (step S14: YES), x _i (t) calculated in advance in step S21 is regarded as BW _i (step S22). ).

That is, the processing shown in Fig. 6 can be expressed by the following equation (2).

If{Σ _i Σ _k Req(i,k)>B and BW _i >y0 _i }then BW _i =x _i (t)else BW _i =Σ _k Req(i,k)/L (2)

In this processing, when the RN _{i is} congested, it is controlled such that the metropolitan area allocation band is close to the target frequency band y0 _i . In the band allocation at the time of congestion, since not only the control having the proportional term but also the control of the integral term and the derivative term is performed, the removal of the residual deviation and the improvement of the response speed can be achieved. In addition, the allocation of the control amount at the time of congestion may be performed by shuffling the RN number (i) every cycle while the fairness of the allocation amount is not maintained in the same order. Sub-replacement determines the order of BW _i ). Also, the differential term may not be applied to the control.

<How to allocate the frequency band of the access section>

Next, the method of band allocation in the access interval will be described.

In the OLT 1, when the bandwidth allocation of the metropolitan area depending on the order shown in Fig. 5 or Fig. 6 is completed, the bandwidth allocation of the access section is performed. In the frequency band allocation in the access section, how to allocate the frequency band allocated to each RN3 (the group of ONUs 5 under the same RN3) to each ONU 5 in the group, according to the ONU 5 connected to each transponder provided in RN3 The number is determined by the amount of the upload band required from the ONU 5, and the like. That is, it is determined how to allocate the frequency band (BW _i ) allocated to each RN 3 (group of ONUs 5 under the same RN 3) by the frequency band allocation of the metropolitan area to each transponder 33 in the RN 3, thereby determining how to allocate to The frequency band of each transponder 33 is allocated to each ONU 5 accommodated in the repeater 33 (step S5 of Fig. 4: ONU band allocation processing). In this way, by performing the band allocation of the access section within the range of the bandwidth allocation amount BW _i not exceeding the metropolitan area, the frequency band of the metropolitan area allocated to each RN3 and the frequency band of the access section can be obtained, so It is possible to avoid the transmission path between each PON and the machine accommodating each PON (the transmission path between each RN 3 and the node 2 on the ring) becomes a bottleneck. The band allocation operation in the access section becomes as follows.

In the frequency band allocation in the access section, the OLT 1 performs the processing shown in FIG. 7 for each RN 3, and determines the frequency band allocated to each of the repeaters 33. In the processing shown in FIG. 7, the i-th RN3 is targeted, and the frequency band bw _ij assigned to the jth (j=0, 1, ..., m) repeater 33 of the RN 3 is used. _Let BW _i ×n _ij /N _i (step S31). Further, "n _ij " indicates the number of users (the number of ONUs) connected to the j-th transponder among the transponders 33 included in the i-th RN 3 .

Further, by repeating the processing of the above-described step S31 while changing the value of j in step S32, the frequency band is allocated to all of the transponders 33 included in the i-th RN3. In other words, the frequency band BW _i allocated to the i-th RN 3 is proportionally distributed to each of the repeaters 33 in accordance with the number of users (the number of ONUs 5) accommodated in the repeater 33 included in the RN 3. Further, in step S33, the processing of steps S31 and S32 is repeatedly executed while changing the value of i, and the frequency band allocated to each of the repeaters 33 is determined for all RNs 3 in the system.

When the frequency bands allocated to all of the repeaters 33 in the system are determined according to the control of FIG. 7, the OLT 1 further calculates the number of the ONUs 5 from the plurality of ONUs 5 connected to the lower layers of the transponders 33. Band allocation amount of the access interval (allocation of the transmission band to each ONU 5). The amount of band allocation of the access zone may also be band allocation control as performed in a conventional PON. As an example, the methods include the following: When the amount of the sum of all the required ONU 5 of the lower band 33 from a transponder bw _ij below, provide the required amount of band for all ONU 5, and the ONU 5 of the exceeding bw _ij A method of allocating a residual frequency band by an arbitrary allocation algorithm after providing a predetermined amount of frequency band. Further, in the frequency band allocation of the access section, after all the frequency bands are allocated to the ONUs of the lower layer of the RN _i as described above, and when there is a residual frequency band, the ONU 5 of the lower layer of the transponder in the congestion may be added. A residual frequency band is provided.

According to such a control method and a calculation algorithm, since the bandwidth allocation of the metropolitan area and the access section can be made and flexible band allocation can be performed, efficient use of the upload band can be realized.

<Overview of the notification method of the band allocation result of the OLT and the transmission operation of the upload direction>

OLT1 is the header allocation information of the metropolitan area network in the bandwidth allocation of the metropolitan area network and the access area network calculated in the above-mentioned order. The OTN-XC unit 22 of the node 2 on each ring is notified. For example, the OLT 1 acquires the ID of the OTN-XC unit 22 in the network by an arbitrary protocol, and generates a band allocation result (band allocation amount) for each OTN-XC unit 22 and a notification destination. The OTU frame including the ID (ID obtained from each OTN-XC unit 22) is transmitted to the ring network. At this time, the OTU frame is transmitted with the optical signal of the wavelength assigned to the ring node 2, and the ring node 2 is provided with the OTN-XC unit 22 which is the notification destination of the band allocation amount. Further, the notified band allocation amount is the sum of the band allocation amount (BW _i ) for each RN 3 accommodated in the OTN-XC unit 22. In each of the ring nodes 2, the ROADM unit 21 extracts the optical signal of the wavelength assigned to the node on the local ring, and outputs the OTU frame included in the extracted optical signal to the OTN-XC unit 22. The OTN-XC unit 22 determines that the band allocation amount is a band allocation result for itself when the received OTU frame contains its own ID and band allocation amount. On the other hand, the ONU 5 is notified by the Gate frame of the MPCP (Multipoint Control Protocol) in terms of the band allocation amount for the ONU 5 determined by the band allocation of the access zone network. In addition, the Gate frame is generated by OLT1 and encapsulated in the interval to RN3 and transmitted as an OTU frame. Alternatively, the display of the display band allocation amount is transmitted from the OLT 1 to the RN 3 by the OTU frame, and the information of the transmitted band allocation amount is used to cause the RN 3 to generate a Gate frame and transmit it to the lower layer ONU 5.

Each of the OTN-XC unit 22 and each of the ONUs 5 that have received the notification of the band allocation result transmits the data to the OLT 1 in accordance with the notification content. Since the transmission operation of the ONU 5 is the same as that of the ONU of the general PON system, the description thereof will be omitted. When the OTN-XC unit 22 receives an upload signal from the ONU 5 via each of the lower RNs 3, the OTN-XC unit 22 stores and transmits an upload signal in an OTU frame of a size corresponding to the band allocation amount notified from the OLT 1.

As described above, in the optical communication system of the present embodiment, the OLT 1 operates as a band allocation control, and first collects the upload band request amount from all the ONUs 5 in the system, and the cycle is the same as the band update period in the PON section or The integer multiple of the period is determined according to the sum of the collected upload frequency band requirements, the sum of each collected RN3 of the collected upload frequency band requirements, and the number of users (ONU5) accommodated in each RN3. The upload frequency band of the RN3 unit (the group of ONUs 5 in the lower layer of the same RN3), and secondly, the frequency band update period in the PON section, based on the number of ONUs 5 connected to each transponder 33, how to allocate the uplink frequency band to the RN3 unit. It is allocated to each PON section (each transponder 33 included in each RN3), and it is determined how to allocate the transmission band allocated to each PON section to each ONU 5 based on the upload band request amount from each ONU 5.

Thereby, since the OLT 1 can be used to adjust the sum of the uploading traffic transmitted from each RN 3, the sum of the uploading traffic can be suppressed to be less than the maximum frequency band in the transmission path between the upper network connected to the OLT 1. It also prevents congestion in the OLT1 and the obsolescence of uploading traffic. As a result, it is possible to prevent the occurrence of retransmission caused by the occurrence of congestion, and it is possible to achieve efficient use of the upload band.

Further, in the present embodiment, when determining how to allocate the transmission band allocated to the RN 3 to each of the transponders 33, it is simply based on the number of ONUs 5 being connected (see Fig. 7). However, in the ONU 5, there are two speeds of 1 Gbps and 10 Gbps in the communication direction in the upload direction, and there is a possibility that fairness cannot be maintained when the number of ONUs 5 that are connected is determined. Therefore, the OLT 1 can also collect the type of the ONU 5 (the communication speed in the upload direction) at the same time as the upload band request amount, and determine the band allocation amount to each of the repeaters 33 in consideration of the type of each ONU 5. Further, the bandwidth allocation amount may be determined in accordance with the sum of the uplink bandwidth requirements from the ONUs 5 connected to the same transponder.

Embodiment 2.

In the system having the configuration described in the first embodiment, the OLT 1 operates as a centralized OLT, and allocates an upload band to all of the ONUs 5 in the system. Here, since the communication in the upload direction of the PON is performed in a time-sharing manner, the upload signals transmitted from the respective ONUs 5 are not flushed with each other. It is important to perform time synchronization management between OLT1 and each ONU 5. Therefore, in the present embodiment, a time synchronization management method between the OLT 1 and each of the ONUs 5 in the optical communication system described in the first embodiment will be described. In the optical communication system of the present embodiment, RTT (Round Trip Time) is managed by ranging (measurement of transmission path delay) in the order shown below, and is prevented from being different. The upload burst signals sent by the ONU 5 conflict with each other.

Fig. 8 is a view showing an example of a ranging procedure in the optical communication system having the configuration shown in Fig. 1. Here, as an example, the ranging procedure when the ONU is registered will be described. In the PON transmission section (between the RN and the ONU) shown in FIG. 8, the MPCP frame for PON control is transmitted and received. The MPCP frame is encapsulated in the PON transmission interval (between the OLT and the RN) and sent and received as an OTU frame. However, the description of the encapsulation/decapsulation operation in the RN will be omitted. Moreover, for simplification of description, the RN is described with a single transponder. Therefore, in the ranging method shown below, the processing performed by the RN is equivalent to the processing executed by the repeater in the RN. In addition, in the OTN transmission interval, the necessary information can also be taken out from the MPCP frame, and the necessary information is transmitted to the header of the OTU frame.

In the control shown in FIG. 8, first, the Discovery Gate frame information storing the relative value of the transmission start time (Grant start time, which is denoted as GST in the figure) is transmitted from the OLT to the RN (step S41). .

RN, the frame received from the OLT, the imprint is displayed on the machine The TS (time stamp) of the local time managed by the local timer is set, and the GST is corrected to the absolute time value (step S42), and the PON frame is generated as needed and transmitted to the ONU (step S43).

The ONU that has received the Discovery Gate frame confirms the TS value (absolute time) embedded in the received frame, and performs processing (TS synchronization) for synchronizing the value of the local timer (step S44). Thereafter, when the transmission start time (GST) designated by the Discovery Gate frame is changed, the Register Request frame of the TS in which the value of the local timer indicating the ONU is printed is transmitted to the OLT (steps S45 and S46). In addition, when the steps S45 and S46 are executed by executing step S44, the local time of the ONU is in a state of being consistent with the local time of the RN.

The RN, when receiving the Register Request frame, is based on the time when the Discovery Gate frame has been sent (the TS value given to the Discovery Gate frame), the TS value embedded in the received frame, and the reception of the frame. The RTT is calculated at the time (the local timer value at the time of reception) (step S47). Next, the RN includes the calculated RTT, and transmits the Register Request frame information to the OLT (step S48).

The OLT, when receiving the Register Request frame information including the RTT, updates the RTT of the corresponding logical link according to the received RTT (step S49). Further, a predetermined process (a process of assigning a logical link to the ONU, etc.) for registering the ONU of the frame transmission source is executed. Next, the OLT sends a message frame information indicating that the login processing of the ONU is completed (step S50), and the RN generates a PON frame as needed, and prints the TS message to the received message and transmits it to the ONU (step S51, S52). ONU, When receiving the Register frame, TS synchronization is performed in the same manner as in the above-described step S44 (step S53). Also, the settings inside the device are changed according to the information contained in the receiving frame. For example, grasp the logical link assigned to the local device and memorize its identification information (logical link ID).

The OLT further allocates a frequency band (Grant generation) for the ONU to send a response frame, and the response frame corresponds to the Register frame information sent in step S50, and sends a GATE frame information for notifying the band allocation result ( Steps S54, S55). In the Gate message, the ID of the logical link assigned to the ONU is embedded.

The RN, when receiving the message of the Gate frame, stamps the TS of the local time of the local device to replace the embedded TS, and corrects the GST according to the local time, and generates the PON frame as needed and transmits it to the ONU (step S56, S57).

When receiving the Gate frame information, the ONU performs TS synchronization in the same manner as the above-described steps S44 and S53 (step S58). Further, the TS is stamped and the Register Ack frame is transmitted (steps S59, S60). The Register Ack frame is transmitted using the frequency band notified by the above-mentioned Gate frame.

When receiving the Register Ack frame, the RN calculates the RTT in the same manner as the above-described step S47 (step S61), and transmits the Register Ack frame information including the calculated RTT (step S62). The OLT, when receiving the Register Ack frame information including the RTT, updates the RTT of the corresponding logical link (step S63).

In addition, the RN is not necessary to notify the OLT of the calculation result every time the RTT has been calculated. At least as long as it is before (previous) The OLT may be notified to the OLT when the RTT is different from the recalculated RTT (including the case where the RTT is not notified to the OLT before).

In this way, the RN, when receiving the frame from the OLT, updates the timestamp value (TS value) in the frame to the local time (the value of the local timer) and transmits it to the ONU. Moreover, when the received frame includes the allocation information of the upload band (in the case of the Discovery Gate frame and the Gate frame), the transmission start time (GST) included in the band allocation information is also transmitted after being updated. To the ONU. Furthermore, when a frame is received from the ONU, the RTT is calculated. Further, when the RN has a plurality of transponders, the RN performs ranging in the above-described order for each transponder. Further, it is not necessary for each ONU accommodated in the RN to check whether the TS value of each frame received by the RN or the GST is based on the local time of the RN, and whether to perform time synchronization with the OLT or between the RN and the RN. Time synchronization. In other words, it is only necessary to perform the same operation as the conventional ONU, and no special operation is required.

Here, the band allocation operation including the correction operation of the GST executed in the above-described step S42 and the like will be described. FIG. 9 is a view showing an example of a band allocation operation, and shows a band allocation operation for a network composed of the kth RN and each ONU of the lower layer of the RN (indicated as ODN#k in FIG. 9). An example. The same is true for the operation of the network composed of the RN other than the kth and the ONU of the lower layer.

In the band allocation operation of the optical communication system according to the present embodiment, first, as Step (A), the OLT calculates the band allocation amount for each logical link (indicated as LL in the figure), and sets the frequency band of each logical link. The result of the assignment is notified to the RN. At this time, the sum of the bandwidth allocation amounts of each logical link does not exceed the upload band allocation amount (BW _k ) for the RN determined in the order described in the first embodiment. In addition, the band allocation result is notified to the RN by the Gate frame (also including the Discovery Gate frame) as described.

As shown in the figure, the band allocation result is notified as the transmission start time (GST) of each logical link and the length of the transmission allowed period (Grant Length, GL in the figure). In Fig. 9, the GST (GST_LT _k (LL)) of the start logical link (LL = 1) is regarded as 0 and the GST and GL (GL _k (LL)) of each logical link are calculated. An example. Further, in order to avoid collision of transmission signals of the respective logical links, GL is a value obtained by deducting 10 from the interval (difference) of each GST. In addition, the OLT may not consider the RTT between the terminals connected to the logical links when determining the GST. Since the GST is corrected in the RN by considering the RTT of each RN of the RN and the lower layer, the OLT only takes into consideration the timing (time) of the signal from each ONU to the local device (OLT) during normal operation. Just fine.

Next, as Step (B), the RN receives the information of the frame (Gate frame, Discovery Gate frame) containing the band allocation result (GST and GL) from the OLT, according to the local time, each logical link The RTT and the previously calculated reference time (RN_GST_base _k ) correct the information in the received frame (the GST of the display band allocation result). For example, the GST of each logical link is added to the reference time, and the corresponding RTT (RTT of each logical link) is subtracted from each GST after the reference time is added to obtain the corrected GST. In addition, no changes have been made to the GL.

Regarding the band update period K, when LL is set as the logical link ID, the GST of each logical link calculated by the OLT is set to GST_LT _k (LL), the reference time is set to RN_GST_base _k , and each of the RNs is held. when a logical link is set to the RTT RTT _k (LL), as an absolute GST (GST after the correction) of GST _k (LL) system to provide the following equation. By implementing such calculations, it is possible to perform upload communication control after scheduling to avoid conflicts in the upload direction.

GST _k (LL)=GST_LT _k (LL)+RN_GST_base _k -RTT _k (LL)

The RN transmits a modified frame including the corrected GSTs generated in this order and the GLs of each logical link notified from the OLT to the ONUs of the lower layers of the local device.

Further, in the operation shown in FIG. 9, the OLT determines the GST regardless of the RTT between the RN and each ONU, and the RN is based on the RTT (RTT of each logical link) and the local time between each ONU. The GST is modified, but the OLT may be configured to determine the GST in consideration of the RTT described above, and the RN corrects the GST only by considering the local time.

Fig. 10 and Fig. 11 are flowcharts showing the sequence of updating (correcting) GST by RN and the order of updating the reference time of the band update period. Fig. 10 is a flowchart showing the procedure of calculating the correction value of GST and updating the reference time, and Fig. 11 is a flowchart showing the procedure of updating the reference time. In the optical communication system according to the present embodiment, as shown in FIG. 10, although the update of the reference time is calculated when the correction value of the GST is calculated, it is also implemented as shown in FIG. The correction of the GST is calculated and the operation of the reference time is updated.

As shown in Figure 10, in the GST correction action, RN#k (kth RN), when receiving the Gate information (information inserted in the Gate frame, Discovery Gate frame), confirms whether it is after startup. The initially received Gate information, if it is the initially received Gate information, initializes the reference time (RN_GST_base _k ). In this initialization operation, the value of the local timer (indicated as TS in Fig. 10) is added with a predetermined offset value (OFFSET), and is taken as the reference time after initialization.

When the initialization of the reference time is completed, or when the received Gate information is not the first received Gate information after startup, each GST (GST of each logical link) included in the received Gate information is updated. In the update operation, first, the reference time RN_GST_base _{k is} added to each of the transmission start times GST_LT _k (LL) included in the received Gate information, and RN_GST _k (LL) of each logical link is calculated. Next, from the calculated RN_GST _k (LL), the corresponding (RTT _k (LL)) in the RTT of each logical link in the hold is subtracted, and is regarded as the updated transmission start time GST _k (LL). ).

When the update is started for all the transmission start times, the reference time is updated. Specifically, the selected value among the transmission start time GST _k (LL) of each logical link calculated by the above-described transmission start time update operation is the largest, and is regarded as the new reference time RN_GST_base _k . Each RN performs such an update operation of the GST every time it receives the Gate information.

Further, each RN updates the reference time in the order shown in Fig. 11 in addition to the operation shown in Fig. 10. In other words, each RN monitors the local time (Local_Timer) and the reference time (RN_GST_base _k ) in the state in which the Gate information has been received, and detects the current value of the local time when the local time is detected as the reference time or higher. The TS adds the predetermined offset value (OFFSET) and is taken as the reference time after the update. The compensation value is determined based on the difference between the local time and the reference time. Specifically, it is considered that the local time becomes a value smaller than the reference time.

As described above, in the optical communication system of the present embodiment, each RN calculates and displays an RTT for displaying an individual transmission delay amount between each ONU of the lower layer in advance, and the OLT notifies the ONU of the RNs that are accommodated in each RN. When the calculation result of the upload band is calculated, the setting value of the transmission start time (GST) is determined regardless of the RTT with each RN, and the RN sets the setting value of the GST included in the receiving frame from the OLT according to the present example. The local time of the machine and the RTT held in advance are updated. In other words, the local time of each of the lower ONUs is controlled in synchronization with the local time of the lower layer, and the RTT between the lower ONUs is calculated, and the calculated RTTs are held in advance. Then, each GST set in the receiving frame is updated according to the local time and the RTT. Thereby, even when the communication path higher than the RN is switched, since the RTT held at the RN is not affected, it becomes easy to perform the upload burst control of the PON, and the communication at the time of switching the communication path can be restored. The time required is shorter than the conventional one.

(industrial availability)

As described above, the optical communication system of the present invention includes a plurality of one-to-many connected networks, and is adapted to set the communication in the upload direction as time division multiplexing. An optical communication system that constitutes communication.

1‧‧‧OLT

2, 2 ₁ , 2 ₂ , 2 _n ‧‧‧ ring nodes

3, 3 ₁₁ , 3 _1p , 3 ₂₁ , 3 _2q , 3 _n1 , 3 _nr ‧‧‧ Remote Node (RN)

4‧‧‧Optocoupler

5‧‧‧ONU

5 ₁ ‧‧1G-ONU

5 ₁₀ ‧‧10G-ONU

5 ₁₀₁ ‧‧10G. 1G-ONU

11‧‧‧OLT-IF

12‧‧‧Monitoring Control Department

13, 21‧‧ ‧ ROADM Department

22‧‧‧OTN-XC Department

31, 115‧‧OptTRx Department

32, 112‧‧‧OTN Mapper/Demapper Section

33‧‧‧猝Transmitter

111‧‧‧ IF Department

113‧‧‧SER/DES Department

114‧‧‧Upload Band Allocation Control Unit

331‧‧‧RTT Management Department

332‧‧‧DOB CDR Department

333‧‧‧DOB Rx Department

334‧‧‧Time Stamp Processing Department

335‧‧1G/10G OptTx Department

336‧‧WDM coupler

337‧‧‧Local timer

Fig. 1 is a view showing a configuration example of an optical communication system of the present invention.

Fig. 2 is a view showing an outline of a configuration example and a control method of an OLT, a ring node, and an RN.

Fig. 3 is a diagram showing the relationship between the metropolitan area band update period and the access band update period.

Fig. 4 is a flow chart showing an example of the overall operation of the band allocation control.

Fig. 5 is a flow chart showing an example of band allocation control for RN3.

Fig. 6 is a flow chart showing an example of band allocation control for RN3.

Fig. 7 is a flow chart showing an example of band allocation control for a repeater.

Fig. 8 is a view showing an example of a ranging procedure in the optical communication system of the present invention.

Fig. 9 is a view showing an example of a band allocation operation.

Fig. 10 is a flow chart showing the sequence of updating the GST and the order of updating the reference time of the band update period.

Figure 11 is a flow chart showing the sequence of updating the reference time of the band update period.

1‧‧‧OLT

2 ₁ , 2 ₂ , 2 _n ‧‧‧ ring nodes

3 ₁₁ , 3 _1p , 3 ₂₁ , 3 _2q , 3 _n1 , 3 _nr ‧‧‧ Remote Node (RN)

4‧‧‧Optocoupler

5 ₁ ‧‧1G-ONU

5 ₁₀ ‧‧10G-ONU

5 ₁₀₁ ‧‧10G. 1G-ONU

Claims (15)

An optical communication system, comprising: a plurality of ring nodes, a remote node, and an ONU, wherein the plurality of ring nodes form a ring network and extracts signal light of a specific wavelength from the ring network and Outputting to other nodes that do not form the ring network, and outputting signal light input from the other node to the ring network; the remote node acts as the other node; the ONU is optically coupled And connected to the remote node, and some of the nodes on the ring are operated as an OLT that performs processing for allocating an upload band to the ONU, and the node operating as the OLT has: 1st The band allocation function treats ONUs under the same remote node as one ONU group, and is allocated to the upload frequency band of the local system, according to the allocation bandwidth allocation requirements from each ONU, and belongs to each ONU. The number of ONUs of the group is allocated to each of the ONU groups; and the second band allocation function is configured to allocate an upload band by the first band allocation function for each of the ONU groups, according to The upload band allocation requirements from each ONU are redistributed to each ONU in the group. The optical communication system according to claim 1, wherein the first aspect is performed in a cycle that is the same as a frequency band update period of a period in which an upload frequency band allocated to each ONU is updated or longer than the frequency band update period. Band allocation function. The optical communication system according to claim 1, wherein the first band allocation function is (the sum of the upload band allocation requirements from all ONUs) ≦ (allocation to the local system) In the case of the frequency band), the same amount of frequency bands as the sum of each of the aforementioned ONU groups from the upload band requirement amount of each ONU is allocated to each ONU group. The optical communication system according to claim 1, wherein the first band allocation function is (the sum of the upload band allocation requests from all ONUs)> (allocation to the local system) In the case of the frequency band, when the upload frequency band allocated to the local system is set to BW, the number of ONUs belonging to the i-th (i=0, 1, ...) ONU group is set to N _i , and the entire system is When the number of ONUs is N, the upload band is allocated to each ONU group so as to be "(the band allocation amount for the i-th ONU group) ≦ (BW × N _i / N)". The optical communication system of claim 4, wherein when the sum of the upload band requirements from the ONUs belonging to the i-th ONU group is set to R _i , then "R _i ≦ (B × When N _i /N)" is established, the same frequency band as R _i is allocated to the corresponding ONU group, and when "R _i >(B × N _i /N)" is established, The same amount of bands of B × N _i / N are allocated to the corresponding ONU group. The optical communication system according to claim 4, wherein when the sum of the upload band requirements from the ONUs belonging to the i-th ONU group is set to R _i , the past will be for the i-th ONU group. When the average value of the allocation band allocation amount is y _i (t) and Δy _i (t)=y _i (t) - B × N _i /N, then "R _i ≦ (B × N _i / When N)" is established, the same frequency band as R _i is allocated to the corresponding ONU group, and when "R _i >(B × N _i /N)" is established, The same amount of frequency band x _i (t) is assigned to the corresponding ONU group The optical communication system according to the first aspect of the invention, wherein the residual frequency band exists when the allocation of the uplink frequency band by the first frequency band allocation function to the ONU group ends, and the residual frequency band is present. The additional ONU group is additionally distributed, and after the additional delivery is completed, the band allocation to the ONU is performed by the second band allocation function. The optical communication system according to claim 1, wherein the remote node includes one or more transponders, and the ONU is connected to the transponder through the optical coupler, and is in the second In the band allocation function, in the process of allocating the upload band to each ONU in each ONU group, first, the allocated upload band is allocated to each transponder according to the number of ONUs in the connection, and secondly, it is assigned to each forwarding. The frequency band of the device is allocated to each ONU according to the amount of the upload band required from each ONU. An optical communication system as described in claim 1, wherein the former The remote node has a function of measuring an RTT indicating a transmission delay time between each ONU connected to itself, and in the case where the Gate information indicating the distribution result of the upload band of each ONU has been received, according to itself The local time and the measurement result of the RTT are corrected and transmitted to the ONUs. The optical communication system according to claim 9, wherein the remote node displays, as the correction target, the GST indicating the transmission start time of each of the ONUs among the information included in the Gate information. The GST is corrected in such a manner that the upload signals transmitted from the respective ONUs do not collide with each other. The optical communication system according to claim 9, wherein the remote node includes: one or more transponders that measure and display an RTT of a transmission delay time between each ONU in the accommodation and maintain If the result of the measurement is received, and the Gate information indicating the distribution result of the upload frequency band of each ONU has been received, the Gate information is corrected according to the local time and the measurement result of the RTT, and then transmitted to the ONUs. The optical communication system according to claim 11, wherein the transponder displays, as the correction target, the GST indicating the transmission start time of each of the ONUs among the information included in the Gate information. The GST is corrected in such a manner that the upload signals transmitted from the respective ONUs do not collide with each other. The optical communication system according to claim 9, wherein the ring node operating as the OLT is determined to be assigned to each ONU. After the upload band is allocated, the aforementioned Gate information is generated regardless of the transmission delay time between each ONU that allocates the upload band. A communication device, characterized in that: in an optical communication system including a plurality of ring nodes, a remote node, and an ONU, and a part of the nodes on the ring node allocates an upload frequency band to the ONU, performing the foregoing uploading The ring-on-node of the processing of the frequency band is a actor, and the plurality of nodes on the ring form a ring network and extract signal light of a specific wavelength from the ring network and output it to other nodes that do not constitute the ring network. And outputting the signal light input from the other node to the ring network; the remote node acts as the other node; the ONU is connected to the remote node through the optical coupler, and is the same far The ONUs in the lower layer of the end node are treated as one ONU group, and will be allocated to the upload frequency band of the local system, according to the allocation bandwidth allocation requirements from each ONU, and the number of ONUs belonging to each ONU group. Allocating to each of the aforementioned ONU groups, and for each of the foregoing ONU groups, allocating the allocated upload frequency bands to each ONU in the group according to the upload bandwidth allocation requirement from each ONU . A frequency band control method, characterized in that: in an optical communication system including a plurality of ring nodes, a remote node, and an ONU, and some of the nodes on the ring are allocated an uplink frequency band to the ONU, The plurality of nodes on the ring form a ring network and extract signal light of a specific wavelength from the ring network and output to other nodes that do not form the ring network, and input signals from the other nodes. Light is output to the ring network; the remote node operates as the other node; the ONU is connected to the remote node through an optical coupler, and the frequency band control method includes: a first frequency band allocation step, The ONUs under the same remote node are treated as one ONU group, and will be allocated to the upload frequency band of the local system, according to the uplink bandwidth allocation requirements from each ONU, and the ONUs belonging to each ONU group. The number is allocated to each of the aforementioned ONU groups; and the second band allocation step is for each of the ONU groups to allocate an upload band by the first band allocation step, according to an upload band allocation requirement from each ONU Redistributed to each ONU in the group.