JP2009171434A - Ason system and optical switch device used for the same, and station-side device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To specify a protocol unique to an ASON, by executing circuit control to optical switch parts 7 and 8 separately from the control of a house side device 2. <P>SOLUTION: This optical switch device 3 is used for constructing the ASON system by connecting a station side device 1 to a plurality of house side devices 2 in P2MP configurations, and is provided with optical switch parts 7 and 8 for selecting the line of an optical signal; and a switch control part 10 for determining the line and opening timing of an optical signal in optical switches 7 and 8, based on gate frames dG and uG, including the operation exclusive gates of the optical switch parts 7 and 8 transmitted from the station-side device 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an optical fiber network in which one station-side device and a plurality of home-side devices are connected in a point-to-multipoint manner for selectively controlling a route of an optical signal transmitted to an optical fiber by an optical switch. It relates to control technology.
In other words, the present invention relates to an ASON system in which an optical splitter in EPON (GE-PON, 10GE-PON, etc.) is replaced with the optical switch, and an optical switch device and a station side device used therefor.

The PON system (Passive Optical Network System) is a point where one station side device (OLT: Optical Line Terminal) and a plurality of home side devices (ONU: Optical Network Unit) are connected via a passive element such as an optical coupler. This is an optical fiber network system in the form of a point to multipoint (P2MP).
Among these PON systems, EPON (Ethernet-PON) is an economical implementation of a high-speed transmission system based on the Ethernet (registered trademark) technology. It was established as IEEE 802.3ah (TM) in June 2004. Is one of the standardized high-speed optical access systems.

  According to the IEEE 802.3ah (TM) standard, MPCP (Multi-Point Control Protocol), which is a control protocol between a station side device and a home side device, and OAM (Operation Monitoring and Control of devices and lines in a communication network) Administration and Maintenance) protocol is defined. Among them, MPCP is an automatic registration function (discovery function) of the home side device, a bandwidth request (REPORT) from the home side device and transmission permission to the home side device (GATE ) And the uplink signal multiplexing control function, etc.

In such EPON, since the optical signal is passively distributed by an optical splitter, the following problems have been pointed out (see Patent Document 1).
(1) Since the optical splitter distributes the optical signal, the power loss of the optical signal is large, and the transmission distance between the station side device and the home side device cannot be set too long.
(2) Since the downstream signal from the station side device reaches all the home side devices connected to the same optical splitter, it is possible for a certain user to spoof intentionally or maliciously and to see the downstream signal addressed to another user's home It is.

(3) A certain user does not obey the transmission permission of the station side device, and intentionally or maliciously continues to emit an optical signal from the home side device, thereby obstructing communication of other home side devices. Is possible.
Therefore, in Patent Document 1, in the point-to-multipoint optical access network, instead of the passive optical splitter used in the PON, an active optical switch for controlling the destination (path) of the optical signal is provided. What is used is recommended, and according to this, the above problems (1) to (3) are solved.

An optical access network that uses an optical switch at the branch point of an optical fiber is called OSAN (Optical Switched Access Network) or ASON (Active Switched Optical Network), which is not yet established as a term, but in this specification, The case of the prior art is called OSAN, and the object of the present invention is called ASON.
On the other hand, in Patent Document 2, an optical switch (OSM: Optical Switching Module) is also provided with a ranging function so that the station side device performs the ranging on the optical switch as in the case of the home side device. An OSAN system is disclosed.

In the system of Patent Document 2, the difference between the round trip delay time of the home-side device and the round trip delay time of the optical switch, which is the result of each ranging, is transmitted to the optical switch, whereby the switching element for the upstream optical switch is switched. It is possible to obtain the connection start time.
IEEE Std 802.3ah (TM) -2004 JP 2006-140830 A JP 2006-246262 A

However, in the OSAN systems described in Patent Documents 1 and 2, since the optical switch is switched based only on the LLID of the home device described in the control frame of the PON, the conventional system adopted in the PON is used. The route and opening timing of the optical switch can be controlled only by a control method according to a protocol (MPCP or the like).
The optical switch element of the OSAN system selects and opens one combination of input port and output port, and broadcasts to a plurality of output ports or inputs from any port within a range of a plurality of input ports. The output signal cannot be output to the output port.
For this reason, for example, control is performed such that a downlink frame with a broadcast LLID is opened in a dynamically grouped route, or an uplink frame from an unspecified home-side device is opened in a grouped range as a response. There is a disadvantage that can not be.

  In view of such circumstances, the present invention enables an ASON system that can define a unique protocol for ASON and control the optical switch unit so that the line control for the optical switch unit can be executed separately from the control of the home-side apparatus and the optical system used therefor. The first object is to provide a switch device and the like.

On the other hand, the conventional GE-OSAN system in which the downstream optical switch is switched in units of PON frames has a further disadvantage that the bandwidth efficiency of the downstream band becomes worse as the transmission speed increases.
That is, the transmission rate in the downstream direction in GE-OSAN is a gigabit class, and the gap between frames is at least about 100 ns (nanosecond). It is technically easy to switch the optical switch within the minimum inter-frame gap, and it is possible to prevent the deterioration of the band efficiency due to the optical switch control.

However, at 10 gigabits, this gap is about 10 ns. In addition, since the LLID field for determining the route is written inside the frame to be sent to the appropriate route, the downstream optical signal is transmitted through the delay line while the switch control unit determines the route by reading the LLID. Delayed by (optical fiber) or the like. In addition to the switching time of the optical switch, it is difficult to add timing control accuracy (blur) to 10 ns or less.
Accordingly, the station side device adds an inter-frame gap in accordance with the performance of the optical switch, and the band efficiency is deteriorated. This deterioration in bandwidth efficiency becomes more prominent when the transmission speed is further increased.

In view of such circumstances, a second object of the present invention is to provide an ASON system capable of improving the bandwidth efficiency in the downlink direction regardless of the increase in transmission speed, an optical switch device used therefor, and the like. And
Furthermore, in GE-OSAN, since the P2MP connection is realized by the optical switch, the downlink signal to the home side device is a burst signal. Therefore, in the period when there is no downstream signal, the clock of the home side device runs on its own, and a deviation from the clock of the station side device occurs. When the station side device grants the uplink transmission permission to the home side device, it is necessary to insert a gap that does not collide with the preceding and following bursts even if the above-described deviation occurs, and there is a problem that the upstream bandwidth efficiency deteriorates. .
In the present invention, in view of such a situation, in the access system in which the station side device and the plurality of home side devices are P2MP connected by the optical switch, the clocks of the station side device and the home side device are not synchronized in frequency. However, a third object is to provide a station-side device that performs bandwidth allocation without deteriorating uplink bandwidth efficiency.

  The optical switch device according to the present invention (Claim 1) is based on an optical switch unit capable of selecting a route of an optical signal and a gate frame including data dedicated to the operation of the optical switch unit transmitted by a station side device. And a switch control unit that determines a path of the optical signal and an opening timing in the optical switch unit.

According to this optical switch device, the switch control unit determines the optical signal route and opening timing in the optical switch unit based on the gate frame including data dedicated to the operation of the optical switch unit, and is adopted in the PON. The route and opening timing of the optical switch can be controlled without being limited to data included in the protocol (MPCP or the like) being used.
For this reason, for example, an ASON-specific protocol for an optical switch unit such as unicasting a discovery gate frame with a broadcast LLID to a specific output port of the optical switch can be introduced. One objective is achieved.

In the optical switch device according to the present invention, when the optical switch unit includes a downstream optical switch capable of selecting a route of a downstream signal transmitted from the station side device, a gate transmitted by the station side device The frame can define a protocol as a downlink gate in which a destination and a transmission period for a downlink burst in which downlink frame sequences are collected by destination are described.
In this case, the switch control unit may determine the path and opening timing of the downstream optical switch based on the downstream gate (claim 2).

Since the downstream gate describes the destination and transmission period for the downstream burst in which downstream frame sequences are grouped by destination, the switch control unit switches the path and the opening timing of the downstream optical switch for each burst. become.
Therefore, according to such an optical switch device, the switching overhead is reduced as compared with the case where the downstream optical switch is switched for each frame, and the deterioration of the bandwidth efficiency in the downstream direction can be prevented. Achieved.

The downlink gate may include a broadcast destination, and when the destination described in the downlink gate is a broadcast, the switch control unit causes all routes of the downlink optical switch to be routed. What is necessary is just to make it open (claim 3).
Furthermore, the downlink gate can include a multicast destination, and when the destination described in the downlink gate is a multicast, the switch controller controls the downlink optical switch corresponding to the destination. It is sufficient to open the route (Claim 4).

In this way, by newly defining broadcast and multicast in the downlink gate for downlink signal line control for the optical switch device, it is possible to broadcast and multicast to the downlink optical switch unit capable of broadcasting to multiple output ports. Corresponding downlink signal line control can be performed.
Therefore, since the frame can be transmitted to all or a plurality of home-side devices by transmitting one frame from the station-side device, it is possible to eliminate a waste of bandwidth between the station-side device and the optical switch device.

  On the other hand, in the optical switch device of the present invention, when the optical switch unit further includes an upstream optical switch capable of selecting a route of an upstream signal transmitted from the home-side device, the switch control unit includes: In order to pass the upstream gate through the downstream optical switch when determining the upstream optical switch opening timing based on the upstream gate in which the upstream source and transmission period for upstream bursts in which upstream frame sequences are grouped by transmission source are described. Preferably, the path of the upstream optical switch is determined in accordance with the setting of the downstream gate.

In this case, since the switch control unit determines the route of the upstream optical switch in accordance with the configuration of the downstream gate for passing the upstream gate through the downstream optical switch, the home side device that is not permitted to transmit the upstream signal The transmission of the optical signal can be blocked by the upstream optical switch.
For this reason, for example, an unauthorized optical signal from a malicious or malfunctioning home device can be blocked, and communication of other home devices can be protected, so that communication security can be improved.

  Further, in the optical switch device of the present invention, when the uplink gate includes information on a scheduled reception period at the station side device, the switch control unit receives the uplink gate when receiving the uplink gate. Obtaining a round-trip delay time with the station side device and advancing the opening timing of the upstream optical switch marked on the upstream gate by the round-trip delay time of the scheduled reception period written on the upstream gate It is preferable to determine by (Claim 6).

If the opening timing of the upstream optical switch is determined as described above, it is possible to accurately detect the passage time of the upstream burst signal with a simple calculation.
In addition, since the scheduled reception period at the station side device is originally required for the uplink bandwidth allocation processing of the station side device, unnecessary processing is unnecessary.
In addition, since the scheduled reception period at the station side device is clearly indicated at the upstream gate, there is an advantage that an external device can detect an unauthorized upstream signal, and even a general home side device knows the station side device and the RTT. be able to. These increase the transparency of the network system.

Further, in the optical switch device of the present invention, when the destination setting of the downstream gate for passing the upstream gate through the downstream optical switch is broadcast, the switch controller controls the entire path of the upstream optical switch. What is necessary is just to make it open (claim 7).
Further, when the destination setting of the downstream gate for passing the upstream gate through the downstream optical switch is multicast, the switch control unit opens the path of the upstream optical switch corresponding to the destination. (Claim 8).

In this way, for the upstream optical switch unit that newly defines broadcast and multicast in the downstream gate for downstream signal line control for the optical switch device, and can merge signals from multiple input ports to the output port By controlling the route of the upstream optical switch in accordance with the destination setting of the downstream gate for passing the upstream gate through the downstream optical switch, it is possible to perform upstream signal line control corresponding to downstream broadcast or multicast.
Therefore, an upstream frame from any home device such as a response to a downstream broadcast or multicast can be delivered to the station device.

  The station-side device of the present invention (Claim 9) can be connected to a plurality of home-side devices in the P2MP form via an optical switch device having an optical switch unit capable of selecting an optical signal route. A station-side apparatus, comprising a control frame processing unit that generates a gate frame including data dedicated to the operation of the optical switch unit, and transmits the generated gate frame to the optical switch device.

According to this station side device, the control frame processing unit generates a gate frame including data dedicated to the operation of the optical switch unit, and transmits the generated gate frame to the light switch device. The route and opening timing of the optical switch unit can be controlled without being limited to data included in the protocol (MPCP or the like).
For this reason, for example, an ASON-specific protocol for an optical switch unit such as unicasting a discovery gate frame with a broadcast LLID to a specific output port of the optical switch can be introduced. One objective is achieved.

In addition, the station side apparatus of the present invention constitutes an ASON system by being connected in a P2MP form to a plurality of home side apparatuses via an optical switch apparatus having an optical switch unit capable of selecting a route of an optical signal. Since it is possible to transmit a downlink burst to the home device via the optical switch device, a period without a downlink signal is generated as compared with the case of the PON system, and a clock deviation from the home device is generated. Prone to occur.
Therefore, when performing the ranging process in the station side device, the round-trip propagation time of the home side device and the frequency difference of the clock with the home side device are further measured using a plurality of reports for the same home side device. (Claim 10).
In this case, the transmission period of the home-side device described in the upstream gate in which the transmission source and transmission period for the upstream burst in which the upstream frame sequence is grouped by transmission source is set, and the reception period for the station-side device is the round-trip propagation. By adjusting the time and the frequency difference, the upstream burst signal arrangement can be determined in consideration of the frequency difference of the clock of the home device. Therefore, it is possible to improve the upstream bandwidth efficiency, thereby achieving the third object.

  The ASON system of the present invention (claim 11) includes a station side device, an optical switch device having an optical switch unit capable of selecting a route of an optical signal, and the station side device and the P2MP form via the optical switch device. The station-side device generates a gate frame including data dedicated to the operation of the optical switch unit, and uses the gate frame as the optical switch. It transmits to an apparatus in advance, The said optical switch apparatus determines the direction and opening timing of the said optical switch part according to the said gate frame, It is characterized by the above-mentioned.

According to this ASON system, the station side device generates a gate frame including data dedicated to the operation of the optical switch unit, transmits the gate frame to the light switch device in advance, and the optical switch device transmits the gate frame. Therefore, the route and opening timing of the optical switch unit are determined according to the above, so that the route and opening timing of the optical switch unit can be controlled without being limited to the data included in the protocol (MPCP or the like) adopted in the PON. .
For this reason, for example, an ASON-specific protocol for an optical switch unit such as unicasting a discovery gate frame with a broadcast LLID to a specific output port of the optical switch can be introduced. One objective is achieved.

As described above, according to the present invention, the line control for the optical switch unit can be executed separately from the control of the home-side device, so that it is possible to define an ASON-specific protocol, for example, the destination is broadcast or multicast It is possible to cope with this case.
Further, according to the present invention, it is possible to prevent the downstream bandwidth efficiency from being deteriorated regardless of the increase in transmission speed.
Furthermore, according to the present invention, it is possible to determine the arrangement of the uplink burst signal in consideration of the frequency difference of the clock of the home side device, so that the uplink bandwidth efficiency can be improved.

[Overall system configuration]
FIG. 1 is an overall configuration diagram of an ASON system according to an embodiment of the present invention.
The ASON system of this embodiment includes an ASON station-side device 1, a plurality of ASON home-side devices 2, an ASON optical switch device 3, and an optical fiber 4 that connects them point-to-multipoint. It is configured. In this system, a station-side device for PON, a home-side device, and an optical splitter in an existing access PON line are respectively connected to a station-side device 1 for ASON, a home-side device 2 for ASON, and an optical switch device for ASON. By replacing it with 3, the system was constructed using the existing optical fiber 4 network.

In the following, for simplification of description, unless otherwise specified, the station-side device 1 for ASON, the optical switch device 2 for ASON, and the home-side device 3 for ASON are each simply a station-side device. 1 and called the optical switch device 2 and the home device 3.
Further, the station side device may be abbreviated as “OLT”, the home side device as “ONU”, and the optical switch device as “RN (Remote Node)” as necessary.

The station side device 1 and each home side device 2 are an extension of 10GEPON (under standardization by IEEE 802.3av task force) and are combined with the optical switch device 3 to constitute the ASON system of the present invention. .
Further, in the ASON system of the present embodiment, the station side device 1 and the home side device 2 are connected to a normal 10 GEPON home side device and a station side device via the optical splitter 5, respectively. It can also operate as a part.

  Further, as shown in FIG. 1, the ASON system of the present embodiment can accommodate the 10GEPON home-side device 2A in combination with other ASON home-side devices 2 or the optical switch device 3. Can be configured in multiple stages.

[Configuration of optical switch device]
As shown in FIG. 1, the optical switch device 3 includes a 1 × N optical switch for downstream signals (hereinafter referred to as downstream optical switch) 7 and an upstream signal as optical switch units capable of selecting a route of optical signals. N × 1 optical switch (hereinafter referred to as upstream optical switch) 8. The optical switch device 3 includes a WDM splitter 9 for multiplexing / separating an optical bidirectional signal and a unidirectional signal, and a switch control unit 10 for controlling opening / closing of the optical switch units 7 and 8.
The switch control unit 10 is passively connected to the station-side device 1 and the optical switch device 3 operates as a kind of home-side device 2 (same for synchronization of the clock of the optical switch device 3).

FIG. 2 is a schematic configuration diagram of the downstream optical switch 7, and FIG. 3 is a schematic configuration diagram of the upstream optical switch 8.
As shown in FIG. 2, the downstream optical switch 7 includes an optical splitter 11 having a single optical fiber connected to the upstream side (right side in FIG. 2) and a plurality of optical fibers connected to the downstream side (left side in FIG. 2). A plurality of semiconductor optical amplifiers (SOA: Semiconductor Optical Amplifiers) 12 provided for the optical fibers branched from the optical splitter 11 are provided.

The optical amplifier 12 is connected to an optical fiber so that the input port I is on the upstream side (right side in FIG. 2) and the output port O is on the downstream side (left side in FIG. 2). A control port G, which is an input part for a control signal (gate signal), is provided.
The optical amplifier 12 blocks the optical signal to the output port O when the control signal for the control port G is 0, and amplifies the optical signal from the input port I when the control signal is 1. This is transmitted to the output port O.

As described above, the downstream optical switch 7 is configured such that after branching by the optical splitter 11, the SOA 12 is inserted for each branch line, and the attenuation by the branch is compensated by the amplification action of the SOA 12 and the SOA 12 is operated by the gate operation. Controls signal opening / closing.
On the other hand, as shown in FIG. 3, the upstream optical switch 8 is also an optical splitter in which a single optical fiber is connected on the upstream side (right side in FIG. 3) and a plurality of optical fibers are connected on the downstream side (left side in FIG. 3). 13 and a plurality of semiconductor optical amplifiers 14 provided in each optical fiber branched from the optical splitter 13, but the input / output direction of the optical amplifier 14 is the reverse of that of the downstream optical switch 7. Circuit configuration.

That is, the optical amplifier 14 of the upstream optical switch 8 is connected to an optical fiber so that the input port I is on the downstream side (left side in FIG. 3) and the output port O is on the upstream side (right side in FIG. 3). .
The optical amplifier 14 also includes a control port G that is an input unit for a digital control signal (gate signal) from the switch control unit 10. When the control signal for the control port G is 0, the output port O When the control signal is 1, the optical signal from the input port I is amplified and transmitted to the output port O.

In this way, the upstream optical switch 8 has a configuration in which the SOA 14 is inserted for each branch line, and the output of the SOA 14 is merged by the optical splitter 13 and the direction is reversed, but the amplification and opening / closing action of the SOA 14 is downstream. The same.
Returning to FIG. 1, the switch control unit 10 of the optical switch device 3 is connected to the optical fiber 4 on the station side device 1 side through a power splitter (hereinafter simply referred to as a splitter) 5. Yes.

  The switch control unit 10 snoops communication between the station-side device 1 and the home-side device 2 or generates a gate frame (in this embodiment, a downlink gate dG) generated exclusively by the station-side device 1 for the optical switch device 3. By performing the switching according to the above, the path and opening period of the downstream optical switch 7 and upstream optical switch 8 constituting the optical switch unit are determined, and the control ports of the optical amplifiers 12 and 14 of the optical switch 7 and 8 are determined. The gate signal to G is output. Details of the switch control unit 10 will be described later.

Also in the ASON system of the present embodiment, wavelength division multiplexing (WDM) is performed by dividing the upstream optical wavelength and the downstream optical wavelength as in the conventional PON system. For this reason, the optical fiber inside the optical switch device 3 is branched by the WDM splitter 9, and only the laser beams having different wavelength components to be received in the upstream and downstream directions reach the optical switches 7 and 8. It is supposed to be.
In the illustrated example, laser light having an upstream wavelength λ1 of 1270 nm and a downstream wavelength λ2 of 1577 nm is used.

[Addition of communication protocol]
Next, a communication protocol for executing the ASON system of this embodiment will be described.
In the present embodiment, the communication protocol between the station side device 1 and the home side device 2 basically follows EPON (IEEE Std 802.3ah) and 10GEPON (IEEE 802.3av). However, as the optical switch device 3 is an active optoelectronic component, the following protocol is further added.

(1) Protocol for Registration Request As described above, since the optical switch device 3 is an active device, management control by OAM is essential.
Therefore, the optical switch device 3 is assumed to be able to communicate with the station-side device 1 as a kind of home-side device 2 and identifies the optical switch device 3 in the registration request (REGISTER_REQ) at the time of discovery of the PON system. Add information for
Similarly, assuming a mixed environment with the home device 2 for 10GEPON, information for identifying the home device 2 for “ASON” is added to the registration request (REGISTER_REQ).

(2) Protocol relating to the downlink gate In the conventional PON system, since the downlink signal is simply broadcast, transmission permission and transmission time regarding the downlink signal are not particularly problematic.
However, in the ASON system of the present embodiment, the destination of the downstream signal is also controlled by the optical switch device 3, so it is necessary to perform downstream line control for the downstream optical switch 7 in the device 3. Therefore, a message for instructing downlink line control is added from the station side device 1 to the optical switch device 3 in advance.

Hereinafter, the message (gate frame) for downlink control to the downstream optical switch 7 is referred to as “downstream gate dG”. On the other hand, the gate for line control in the uplink direction defined in the conventional MPCP is referred to as “uplink gate uG”.
In the downlink gate dG, a destination and a transmission period for a downlink burst in which downlink frame sequences transmitted by the station side device 1 are grouped by destination are described. That is, in the downlink gate dG, in addition to the LLID (Logical link ID) for identifying the home device 2, a set of transmission periods (specified by the start time and the transmission time) of the downlink signal in the station device 1 is provided. One or more are listed.

Note that the LLID includes not only a unicast LLID but also a broadcast or multicast LLID.
The exchange of messages of the downlink gate dG can be performed by defining a new MPCP frame or may be performed by an OAM frame. However, assuming that all of the multi-stage optical switch devices 3 are broadcast, It is preferable to use MPCP frames.

(3) Protocol for Upstream Gate On the other hand, the upstream gate uG describes the transmission source and the transmission period for the upstream burst in which the upstream frame sequence transmitted by the home side apparatus 2 is grouped according to the transmission source as defined in the conventional MPCP. ing. Therefore, the uplink line control for the upstream optical switch 8 is performed by snooping (looking into) the upstream gate uG transmitted by the station side device 1.
That is, the path of the upstream optical switch 8 is equal to the path of the downstream switch 7 when the upstream gate uG passes, and the opening period of the upstream optical switch 8 follows the contents described in the upstream gate uG. .

However, since the transmission period written in the upstream gate uG is specified by the clock of the home-side device 2, the time period for passing through the optical switch device 3 is unknown by itself.
Therefore, in order to derive the passage period for this optical switch device 3, information on the reception period (reception start time and reception time) in the station side device 1 is added to the uplink gate uG.
FIG. 4 is a sequence diagram illustrating a method in which the home-side device 2 and the optical switch device 3 measure the round-trip delay time with the station-side device 1 when the above information is added.

As shown in the sequence on the left side of FIG. 4, if the information of the reception start time and the reception time at the station side device 1 is written in the uplink gate uG, (OLT reception start time) − (ONU (or RN) transmission (Start time) represents a round trip time (RTT) between the OLT and the ONU (or RN), and the RTT between the OLT and the OLT can also be known.
Then, as shown in the sequence on the right side of FIG. 4, the RN advances the OLT reception period recorded in the upstream gate uG to the ONU by the RTT between the OLT and the RN, so that the upstream burst signal from the ONU is The period of passing through the optical switch device 3 can be determined according to the RN's own clock.

[Configuration of station side equipment]
The station-side device 1 of this embodiment is basically a 10-GEPON station-side device, and operates as a 10-GEPON station-side device even in an environment in which the optical switch device 3 is replaced with an optical splitter.
The station side apparatus 1 starts a discovery sequence first with respect to an access line. In the ASON system in which the optical switch device 3 is operating, the optical switch device 3 is registered in this sequence, and the station side device 1 recognizes the presence of the device 3.
Furthermore, by repeating the discovery sequence, the home-side device 2 subordinate to the optical switch device 3 and the lower-order optical switch devices 3 in multiple stages are registered.

FIG. 5 is a block diagram illustrating an example of the station-side device 1.
As shown in FIG. 5, the station-side device 1 has a transmission control circuit 17 that schedules the transmission timing of the downlink signal, and a band for performing dynamic bandwidth allocation (DBA: Dynamic Bandwidth Allocation) for the uplink signal from the home-side device 2. An allocation circuit 28 is provided.

Downstream frames from the higher-order uplink line are distributed to the downstream queue 16A for each home-side apparatus 2 having a different destination, and are temporarily stored in the downstream buffer 16.
At this time, broadcast frames and multicast frames are also distributed to the dedicated downstream queue 16A. It is assumed that multicast constitutes the queue 16A for each group.

The transmission control circuit 17 as a downlink scheduler determines the transmission order and the transmission amount of each queue 16A based on attributes (allocated bandwidth, delay, etc.) given to each queue 16A by the operator.
The unit of the transmission amount of each downlink queue 16A to be determined by the downlink scheduler 17 is determined in consideration of the trade-off between the bandwidth efficiency and the delay (the larger the unit, the better the bandwidth efficiency but the longer the delay). However, it is typically on the order of several microseconds in terms of transmission time (for 10 Gbps, one to several Ethernet maximum length frames).

In this way, a frame group for the home apparatus 2 that the station apparatus 1 collectively generates the downlink frame sequence for each downlink queue 16A is referred to as a “downlink burst”. A signal for synchronization may be inserted at the head of this downstream burst.
The transmission control circuit 17 generates a downlink gate dG including information on the transmission order and transmission amount of the downlink burst determined in advance as described above, and transmits the downlink gate dG as an optical signal to the access line. Thereby, the optical switch apparatus 3 can grasp | ascertain the transmission order and transmission amount of a downlink burst.

When performing multicast for dynamically setting a group of home-side devices 2 to be broadcast (this is defined as dynamic multicast), the control frame processing circuit 26 of the station-side device 1 uses the multicast LLID and the homes belonging to the group. The correspondence of the unicast LLID of the side device 2 is instructed to the optical switch device 3 by OAM, for example.
In addition, there is a static multicast, which reserves a fixed correspondence between the multicast LLID and the port of the optical switch device 3.

Similarly to the case of EPON, the bandwidth allocation circuit 28 of the station side device 1 collects the status of the upstream queue from the home side device 2 by a report (REPORT) which is a control frame transmitted from the home side device 2. The latest RTT is obtained by the time management circuit 25.
Then, the bandwidth allocation circuit 28 sets the upstream burst arrangement (reception start time and reception time in the station side device 1) with a predetermined algorithm so as to satisfy the attributes (allocation bandwidth, delay, etc.) given by the operator. The transmission permission is given to each home-side apparatus 2 at the upstream gate uG.

Hereinafter, the internal configuration of the station apparatus 1 will be described with reference to FIG.
As shown in FIG. 5, the downlink frame from the uplink line is temporarily stored in the downlink buffer 16 via the receiver 30 </ b> B and then sent to the encoding circuit serializer 18 based on an instruction from the transmission control circuit 17.
The encoding circuit serializer 18 encodes the transmission frame based on a predetermined method and a predetermined rate, and sends it to the electro-optical converter (E / O) 19 as a serial bit signal. At this time, if the frame to be transmitted is a control frame, the latest value of the ASON counter is referred to and a time stamp TS is attached to the frame. An electro-optical converter (E / O) 19 converts a serial bit signal into an optical signal, and sends it to the optical fiber 4 of the ASON system via a WDM coupler.

On the other hand, an upstream optical signal incident from the optical fiber 4 of the ASON system through the WDM coupler is converted into an electrical signal by an opto-electric converter (O / E) 20 and input to the clock / data recovery circuit 21. The clock / data recovery circuit 21 extracts a clock signal included in the received signal, samples the received signal with the clock signal, reproduces serial data, and sends the serial data to the deserializer decoding circuit 22.
The deserializer decoding circuit 22 converts the serial data into low-speed parallel data and performs a decoding process to restore the original frame.

The restored frame is input to the frame type classification circuit 23, and the control frame and other user frames are classified. Among these, the user frame is transmitted to the uplink line via the transmitter 30A, and the control frame is transmitted to the control frame processing circuit 26 via the time stamp extraction circuit 24.
The time stamp extraction circuit 24 reads the time stamp TS and sends it to the time management circuit 25. The control frame processing circuit 26 judges the type of the control frame and sends information relating to the registration processing of the home side device 2 and the optical switch device 3 to the registration processing circuit 27 to allocate the bandwidth to the home side device 2 and the optical switch device 3. Is sent to the bandwidth allocation circuit 28.

The registration processing circuit 27 instructs the bandwidth allocation circuit 28 to start the registration processing, and exchanges control frames based on a sequence determined with the home-side device 2 and the optical switch device 3 that have requested registration. Then, the home device 2 or the like is registered or the registration is rejected.
When registering the home device 2 or the like, the registration processing circuit 27 instructs the bandwidth allocation circuit 28 to continuously allocate the bandwidth to the home device 2 or the like.

Based on the registration processing activation instruction from the registration processing circuit 27, the bandwidth allocation circuit 28 allocates transmission permission for polling the registration request, and instructs the control frame processing circuit 26 to issue a control frame for bandwidth allocation. .
When the bandwidth allocation circuit 28 receives the control frame of the bandwidth allocation request from the control frame processing circuit 26, the bandwidth allocation circuit 28 executes bandwidth allocation processing based on a predetermined policy, allocates transmission permission to each home-side device 2, and The control frame processing circuit 26 is instructed to issue a control frame (uplink gate uG) for allocation.

  When receiving a control frame issuance instruction from the registration processing circuit 27 or the band allocation circuit 28, the control frame processing circuit 26 configures a corresponding control frame and sends it to the transmission control circuit 17. The details of the sequence related to registration of the home device 2 will be described later.

The reference clock generation circuit 29 autonomously oscillates within a frequency range determined around the ideal frequency f and generates a reference clock.
The time management circuit 25 counts the reference clock to generate an ASON counter, and distributes this counter to each main part of the station side device 1. When the time management circuit 25 receives the time stamp TS of the control frame, the time management circuit 25 calculates a round-trip propagation time RTT with the home-side device 2 that is the transmission source of the frame, and uses this RTT information for each station-side device 1. Distribute to key parts.

At this time, the time management circuit 25 examines a change from the immediately preceding RTT, and generates an alarm if the fluctuation exceeds a predetermined range. When receiving this alarm, the registration processing circuit 27 performs necessary processing such as refusing registration of the home device 2.
When the transmission control circuit 17 receives the control frame (including the downlink gate dG and the uplink gate uG) from the control frame processing circuit 26, the transmission control circuit 17 temporarily stores the control frame in the downlink buffer 16 and performs scheduling with priority over transmission of a general downlink frame. I do. At this time, the time stamp TS is added to the control frame with reference to the latest value of the counter.

[About home equipment]
The home device 2 of this embodiment is basically a 10 GEPON home device and operates as a 10 GEPON home device in the PON environment.
However, in the ASON system of the present embodiment, since the downlink signal is also a burst signal, the receiving circuit (the photoelectric converter (O / E) 31) of the home side apparatus 2 is a burst signal in the same manner as the station side apparatus 1. Can be received, and whether the downstream signal is a continuous signal or a burst signal can be identified.

When the downlink signal is a continuous signal, the clock of the home device 2 is driven in synchronization with the downlink signal, and when the downlink signal is a burst signal, the clock of the home device 2 is autonomously driven. In any case, the upstream signal is transmitted in synchronization with the clock of the home device 2.
As a burst reception technique in the home side apparatus 2, a well-known technique used for an EPON station side apparatus such as a high speed AGC or a high speed CDR can be adopted.

FIG. 6 is a block diagram illustrating an example of the home device 2.
The downstream optical signal incident from the optical fiber 4 through the WDM coupler is converted into an electrical signal by an opto-electric converter (O / E) 31 and input to the clock / data recovery circuit 32. Further, the photoelectric converter (O / E) 31 identifies a continuous signal on the condition that a downstream optical signal is always input (in contrast, a burst signal), and sends it to the clock circuit 37 as a continuous light identification signal.
The clock / data recovery circuit 32 extracts the clock signal included in the received signal, samples the received signal with the clock signal, reproduces the serial data, sends the serial data to the deserializer decoding circuit 33, and reproduces the recovered clock. Is sent to the clock circuit 37.
The deserializer decoding circuit 33 converts the serial data into low-speed parallel data and performs a decoding process to restore the original frame.

The restored frame is input to the frame type classification circuit 34, where the control frame and other frames are classified. Among these, the user frame is transmitted to the uplink line via the transmitter 44A, and the control frame is transmitted to the control frame processing circuit 36 via the time stamp extraction circuit 35.
The time stamp extraction circuit 35 reads the time stamp TS and sends it to the clock circuit 37. The control frame processing circuit 36 determines the type of the control frame and sends information related to the registration processing to the registration processing circuit 38. If it is related to transmission permission, the transmission control circuit 39 is notified of transmission permission information.

The transmission permission information includes a data type (registration permission or normal permission: in the case of normal permission, whether bandwidth request is forced), a transmission start time, and a transmission duration.
The registration processing circuit 38 exchanges control frames based on a sequence determined with the station side device 1 to register the home side device 2. When receiving a control frame issuance instruction from the registration processing circuit 38, the control frame processing circuit 36 configures a corresponding control frame and sends it to the transmission control circuit 39. The details of the sequence related to registration of the home device 2 will be described later.

The local clock generation circuit 40 autonomously oscillates within a frequency range determined around the ideal frequency f and generates a local clock.
The clock circuit 37 counts the ASON counter with reference to the recovered clock when the continuous light identification signal is valid, and supplies the reference clock to the transmission control circuit when the continuous light identification signal is not valid. Operates in synchronization with this clock). The value of this counter can be referred from the transmission control circuit 39. When the time stamp TS of the control frame is received, the ASON counter is updated with the value.
At this time, a change from the immediately preceding counter is examined, and if the fluctuation exceeds a predetermined range, an alarm is generated. In response to this alarm, the registration processing circuit 38 performs necessary processing such as withdrawal of registration.

The receiver 44B receives the frame from the user line, filters the frame whose destination is in the user line, and temporarily stores the frame to be transmitted in the upstream direction in the upstream buffer 41. The state of the upstream buffer 41 is managed by the transmission control circuit 39.
When receiving a control frame to be transmitted from the control frame processing circuit 36, the transmission control circuit 39 temporarily stores it in the upstream buffer 41. Also, when a request for bandwidth request is instructed by permission to transmit, a report frame (a type of control frame) reflecting the state of the upstream buffer 41 is generated and recorded in the upstream buffer 41.

The transmission control circuit 39 receives a transmission permission notification from the control frame processing circuit 36. When the transmission permission data type is normal permission, the transmission control circuit 39 instructs the electro-optical converter (E / O) 43 to emit light when the ASON counter reaches the transmission start time, and continues transmission. The light emission instruction is continued until time elapses.
At this time, prior to the light emission instruction, the upstream buffer 41 is instructed to take out an amount of transmission frames corresponding to the transmission duration. In addition, when the band request forcing is instructed, the report frame is taken out. Also, the amount commensurate with the transmission duration means that data after encoding (including codes for error correction) can be transmitted in the transmission duration.

On the other hand, when the control frame of the registration request is received from the control frame processing circuit 36, since the data type of transmission permission is the registration request, the transmission control circuit 39 starts from the time when the ASON counter reaches the transmission start time. After waiting for a random time within the range of the transmission duration, the electro-optical converter (E / O) 43 is instructed to emit light, and the light emission instruction is continued for the time required to transmit the registration request control frame. At this time, prior to the light emission instruction, the upstream buffer 41 is instructed to take out the frame.
The frame extracted from the upstream buffer 41 is encoded by the encoding circuit serializer 42 based on a predetermined method and a predetermined rate, and sent to the electro-optical converter (E / O) 43 as a serial bit signal.
At this time, if the frame to be transmitted is a control frame, the latest value of the ASON counter is referred to and a time stamp TS is attached to the frame. The electro-optical converter (E / O) 43 converts a serial bit signal into an optical signal for a period when there is a light emission instruction. On the other hand, the electro-optical converter (E / O) 43 does not emit light during a period when there is no light emission instruction. The optical signal converted by the electro-optical converter (E / O) 43 is sent to the access line via the WDM coupler.

[Ranging processing considering frequency difference]
As described above, the band allocation circuit 28 of the station-side device 1 grants transmission permission to each home-side device 2 at the upstream gate uG, but in this embodiment, at this time, the home-side device 2 described in the upstream gate uG. The transmission period is set so that the reception period at the station side device 1 is advanced by the RTT with the home side device 2 and the difference in the clock frequency difference between the station side device 1 and the home side device 2 is corrected. . The reason is as follows.

That is, in EPON, the clock of the home device 2 is synchronized with the clock of the station device 1 by loading the time stamp TS every time an MPCP frame is received, and the interval of the MPCP frame is included in the received signal. Synchronization is maintained by updating the clock with a clock.
However, in the ASON system of the present embodiment, the downlink signal to the home side device 2 is also a burst signal, and thus synchronization cannot be maintained using the received signal. Similarly, the upstream signal cannot be transmitted at the loop timing synchronized with the downstream signal.

For this reason, the bandwidth allocation circuit 28 of the station side device 1 determines transmission permission by the uplink gate uG on the assumption that the clock of the home side device 2 is self-running, but the Ethernet protocol allows a clock error of ± 100 ppm. Therefore, when the interval is 1 ms, a time lag of a maximum of 200 ns occurs, and the time effect cannot be ignored.
That is, it is necessary to insert a gap so that the preceding and following bursts do not collide even if the above-described deviation occurs, resulting in poor bandwidth efficiency.

Therefore, the station-side device 1 uses the two reports (first report and second report) with different elapsed times at the home-side device 2, in addition to the RTT, the clocks of the station-side device 1 and the home-side device 2. The frequency difference df is measured.
FIG. 7 is a sequence diagram showing the ranging process for obtaining the frequency difference.
As shown in FIG. 7, the OLT bandwidth allocation circuit 28 generates one GATE forcing transmission of two REPORTs in the ranging process for calculating the RTT, and transmits this GATE from the transmitter 19.

This GATE includes one time stamp TS and two transmission permissions. At this time, the transmission permission for the first first REPORT is the GATE reception time and the latest transmission time, similar to the transmission permission for REPORT in the ranging process.
On the other hand, it is desirable that the transmission permission for the second second REPORT should be as long as possible in the ONU.

  Here, assuming that the reception time of the first REPORT is Tr, the equation (Tr-TS) when the first REPORT is received reflects the exact RTT of the OLT and the ONU. Also, since the change in RTT between these two REPORTs is relatively small, the difference between (Tr-TS) at the time of receiving the first REPORT and that at the time of receiving the second REPORT is the difference between OLT and ONU. It can be said that this is due to the difference in clock frequency between

Therefore, the OLT calculates the clock frequency difference df together with the RTT from the above measurement. In this way, the OLT adjusts the transmission start time by GATE in consideration of the deviation due to the actually measured frequency difference df.
In the example of FIG. 6, the case where the transmission time of the first REPORT is set close to the reception time of GATE is illustrated, but the method for measuring df is not limited to this.

That is, although the accuracy is inferior, RTT and df may be calculated from two independent GATE-REPORTs having different elapsed times in the ONU.
In this case, since the OLT or ONU clock frequency changes over time due to environmental conditions or the like, it is preferable that the calculation of df is continuously performed as in the case of RTT. If the measurement conditions are not satisfied in the original GATE-REPORT process, the second-stage ranging is started.

Then, in consideration of the frequency difference df, the band allocation circuit 28 of the station side device 1 arranges the upstream burst signals from the home side devices 2 densely without collision.
However, since the downstream signal between the OLT and the RN is a continuous signal, the clock of the optical switch device 3 is synchronized with the downstream reception signal. Further, a signal for burst synchronization is not necessary for the downstream signal addressed to the optical switch device 3.

[Route control by switch control unit]
As illustrated in FIG. 1, the switch control unit 10 of the RN is passively connected to the station-side device 1 and operates the optical switch device 3 as a kind of home-side device 2.
Accordingly, the switch control unit 10 is configured to shut off all the optical switches 7 and 8 at the initial time, and registers the optical switch device 3 in response to the discovery sequence from the station side device 1.

As described above, since the reception period at the station side device 1 is added to the upstream gate uG, the switch control unit 10 obtains the RTT between the OLT and the RN, and thereafter, the upstream gate uG arrives at itself. RTT is updated every time.
Further, when receiving the downstream gate dG, the switch control unit 10 determines the route and the opening period of the downstream optical switch 7 and generates a gate signal for the SOA 12 of the downstream optical switch 7. In this case, the switch control unit 10 determines the route of the downstream switch 7 by grasping the correspondence between the LLID and the branch line, and this control will be described later.

Further, the switch control unit 10 opens all the paths of the downstream optical switch 7 when the LLID of the downstream gate dG is broadcast LLID, and responds to the destination when the LLID of the downstream gate dG is multicast LLID. The direction of the downstream optical switch 7 to be opened is opened.
On the other hand, the switch control unit 10 snoops the upstream gate uG from the OLT and controls the route of the upstream optical switch 8 together with the downstream gate dG for passing the upstream gate uG.
That is, the switch control unit 10 determines the path of the upstream optical switch 8 by the downstream gate dG for passing the upstream gate uG through the downstream optical switch 7, and determines the opening period of the upstream optical switch 8 by the upstream gate uG. As described above, the opening period is a period in which the OLT reception period written in the upstream gate uG to the home side apparatus 2 is advanced by RTT between OLT and RN.

In the example of this embodiment, the upstream optical switch 8 does not detect that the burst signal has arrived for each port of the switch because of the cost.
However, as an example that makes this possible, there is a method of branching an upstream optical signal with an optical coupler and detecting the presence or absence of the optical signal with a light receiving element.
Assuming this, the optical switch device 3 can learn the correspondence between the unicast LLID of the home-side device 2 and the branch port, and the port discovery sequence in the discovery batch method described later becomes unnecessary.

On the other hand, in the system in which the normal 10GEPON home-side device 2A is mixed (FIG. 1), the switch control unit 10 fully opens the downstream optical switch 7 at the stage where the optical switch device 3 is registered, and is used for ASON. The branch line port of the downstream optical switch 7 in which the home device 2 is found is switched to opening by the downstream gate dG.
By doing so, it becomes possible to mix home-side devices 2A that cannot receive bursts. At this time, if the 10GEPON home-side device 2A is replaced with the optical switch device 3, a multi-stage configuration of the optical switch device 3 is possible.

[Configuration of switch control unit]
FIG. 8 is a functional block diagram showing the configuration of the switch control unit 10.
As shown in FIG. 8, the optical fiber branched from the power splitter 5 (FIG. 1) provided in the optical switch device 3 is connected to the WDM splitter 45 of the switch controller 10, and this splitter 45 is connected to the downstream optical signal. And the upstream optical signal are separated / multiplexed.
The separated downstream optical signal is converted into an electrical signal by an opto-electric converter (O / E) 46 and input to a clock / data recovery circuit 47.

The clock / data recovery circuit 47 extracts a clock signal included in the received signal, samples the received signal with the clock signal, and reproduces serial data. This clock signal is input to the clock circuit 48 and the encoding circuit serializer 49.
On the other hand, the serial data is input to the deserializer decoding circuit 50, where it is converted into a low-speed parallel signal and decoded to restore the original frame.

From the restored frame, the frame type classification circuit 51 classifies the MPCP frame, the downlink gate frame, and the frame addressed to the RN, and sends them to the time stamp extraction circuit 52.
The time stamp extraction circuit 52 extracts the time stamp TS at the time of OLT transmission described by the station side device 1, sends it to the clock circuit 48, and passes the frame to the control frame processing circuit 53.
The clock circuit 48 resets its clock so that the input time stamp TS becomes the current time, and updates the clock with the extracted clock in the interval of the time stamp TS.

However, when the drift of the time stamp TS is larger than the specified value, the clock is not reset, and a time stamp drift violation alarm is sent to the control frame processing circuit 53.
The clock of the clock circuit 48 can be referred to from the control frame processing circuit 53, the down switch control circuit 54, the up switch control circuit 55, and the like.
The control frame processing circuit 53 performs registration of the optical switch device 3, RTT calculation with the OLT, and management information exchange with the OLT in response to the received MPCP frame or frame addressed to the RN.

At this time, when sending a registration request (REGISTER_REQ), a registration response (REGISTER_ACK), a report (REPORT), management information, etc. to the station side device 1, at the timing according to the upstream gate uG addressed to the optical switch device 3, The frame is sent to the encoding circuit serializer 50.
The encoding circuit serializer 59 performs encoding and conversion to a high-speed serial signal in synchronization with the clock extracted by the clock / data recovery circuit 47.
This serial signal is converted into an optical signal by an electro-optical converter (E / O) 56, and this optical signal is multiplexed as an upstream optical signal via the WDM splitter 45 into a downstream signal. At this time, the electro-optical converter 56 emits light only during a period according to the upstream gate uG to the optical switch device 3.

The control frame processing circuit 53 holds the correspondence between the LLID and the branch ports of the optical switches 7 and 8 in, for example, a reference table.
This correspondence relationship is determined by whether it is reserved in advance, notified from the station-side device 1 as management information, or learned by an ONU registration sequence by an individual method described later.

When receiving the downstream gate frame, the control frame processing circuit 53 breaks it into opening instruction information for each transmission period and puts it into the first queue 57. At this time, the opening instruction is inserted at a position aligned in time order, and the LLID is replaced with a route bitmap representing the opening branch port by the reference table.
The downstream switch control circuit 54 refers to the opening instruction information at the head of the first queue 57, and drives the gate signal of the downstream optical switch 7 according to the route bitmap while the clock corresponds to the opening instruction period. At the same time, the head entry of the first queue 57 is removed. The drive signal of the downstream optical switch 7 (represented by a bit map) is returned to the control frame processing circuit 53 via the delay circuit 59.

A certain processing delay occurs until the downstream frame reaches the control frame processing circuit 53 via the power splitter 5 → O / E 46 → time stamp extraction circuit 52 in the optical switch device 3.
Therefore, the delay circuit 59 takes into account such a processing delay and compensates for a difference between the input frame to the control frame processing circuit 53 and the drive signal of the downstream optical switch 7 for passing the input frame.

Further, the control frame processing circuit 53 snoops the uplink gate frame to other than itself, converts it into opening instruction information for each grant, and puts it into the second queue 58 (inserts the opening instruction at a position aligned in time order).
At this time, the route bitmap representing the open branch line port reflects the drive information (bitmap) of the downstream optical switch 7 at that time. Further, the opening period is a period in which the OLT reception period corresponding to the grant (this is written in the uplink gate uG) is advanced by RTT between the OLT and the RN.
The upstream optical switch control circuit 55 refers to the opening instruction information at the head of the second queue 58 and drives the gate signal of the upstream optical switch 8 according to the route bitmap while the clock corresponds to the opening instruction period. At the same time, the head entry of the second queue 58 is removed.

[Registration method for home device]
In the ASON system of the present embodiment, since the optical switch device 3 directs the destination of the downstream optical signal, discovery of the home device 2 (registration for automatically establishing a communication link with the unknown home device 2) In performing (work), it is necessary to register the home device 2 in association with the branch port of the optical switch device 3.
Various methods for registering the home-side device 2 associated with this branch line port are conceivable. Hereinafter, two typical methods (individual method and collective method) will be described.

[Registration method by individual method]
In short, the registration method using this individual method (also referred to as a sequential method) is a method of performing discovery for each branch line port of the optical switch device 3.
The OLT designates a static multicast LLID defined in a branch line selective manner in a downstream gate dG for passing the discovery gate through the downstream optical switch 7. In response to this, the RN passes only the reserved branch line through the discovery gate.

The OLT gives a new LLID at the time of registration, but passes through the reserved LLID up to the downstream gate dG for the registration notification (REGISTER), and then passes through the new LLID.
The RN can snoop the new LLID written in the registration notification (REGISTER) and recognize the correspondence with the reservation LLID and the branch port.
FIG. 9 is a sequence diagram showing a registration method using the individual method. Hereinafter, the contents of the registration method will be further described with reference to FIG.

Here, the notation of each control frame used in the registration sequence shown in FIG. 9 is defined as follows.
dG (pJ, Pk): Down gate that opens the branch line pJ for the period Pk uG (L, Pk): Up gate to the ONU of LLID (L) (grant period Pk)
uDG (Pk): Up discovery gate (grant period Pk)
RR (aM): Registration request (REGISTER_REQ) from ONU of address aM
R (aM, L): Registration notification (REGISTER) for assigning LLID (L) to ONU of address aM
RA (L): Registration response (REGISTER_ACK) from ONU of LLID (L)

As shown in order from the left in FIG. 9, first, the OLT sends a downlink gate dG (p1, P1) to the access line. Thereafter, the OLT sends an upstream discovery gate uDG (P2) to the access line during the opening period P1.
The RN receives the downstream gate dG (p1, P1), and opens the branch line p1 of its downstream optical switch 7 for the period P1. Further, the RN snoops the upstream discovery gate uDG (P2) that passes in the period P1, and opens the branch line p1 of the upstream optical switch 8 (corresponding to the path of the downstream optical switch in the period P1) during the period P2. Let (As described herein, the control of the optical switches 7 and 8 performed by the RN is subordinate, and the operation of the RN will be omitted in the description of FIG. 9 hereinafter.)
The OLT receives, for example, a registration request RR (a1) from the ONU of the unregistered address a1 as a response of the upstream discovery gate uDG (P2) sent to the branch line p1.

Thereafter, the OLT sends the downlink gate dG (p1, P3) to the access line. Then, the OLT sends a registration notification R (a1,1) and an upstream gate uG (1, P4) during the opening period P3, assigns LLID (1) to the ONU at address a1, and sends it to the ONU. The transmission permission for period P4 is given.
The ONU that has received the registration notification R (a1, 1) sends out a registration response RA (1) during the period P4 when the transmission permission is given. The OLT that has received the registration response RA (1) registers the ONU that issued the response RA (1) as the ONU (a1) of the address a1 connected to the branch line p1.

Similarly, the OLT sends the downlink gate dG (p2, P5) to the access line, then sends the uplink discovery gate uDG (P6) during the period P5, and further from the ONU of the unregistered address a2. The registration request RR (a2) is received.
After that, the OLT sends the downlink gate dG (p2, P7) to the access line, and then sends the registration notification R (a2, 2) and the uplink gate uG (2, P8) during the period P7. LLID (2) is assigned to the ONU at address a2, and transmission permission for period P8 is given to the ONU.

  The ONU that has received the registration notification R (a2, 2) sends out a registration response RA (2) during the period P8 in which the transmission permission is given. The OLT that has received the registration response RA (2) registers the ONU that issued the response RA (2) as the ONU (a2) of the address a2 connected to the branch line p2.

As described above, according to the registration method based on the individual method, the OLT opens the branch lines pJ (J = 1 to N) of the downstream optical switches 7 and 8 one by one for the predetermined period Pk one by one. ) Individually, and during the opening period Pk of the individual branch line pJ, the upstream discovery gate uDG (Pk) is transmitted and discovery is performed between the unregistered ONUs. It can be recognized whether it is connected to the branch line pJ.
For this reason, even if the relationship between the ONU and the branch line port of the RN is not set in advance, the ONU can be automatically registered including the corresponding relationship.

[Registration method by batch method]
On the other hand, the registration method based on the collective method is basically a method in which discovery similar to EPON is performed simultaneously on all branch port ports (not necessarily all, but some of the branch port ports). It is.
That is, the OLT designates the broadcast LLID for the downstream gate dG that passes through the upstream discovery gate uDG. As a result, the OLT can find an ONU on an arbitrary branch line, but by this alone, neither the OLT nor the RN can recognize the correspondence between the ONU and the branch line.

Therefore, the OLT executes a port discovery sequence subsequent to the discovery sequence.
In this port discovery sequence, the OLT sends a report forced gate to the new LLID while changing the passing static LLID by trial and error, and finally determines the branch port to which the ONU belongs depending on the presence of this report (REPORT). To be specific.
In this case, for example, by performing a binary search by assigning a reserved LLID to a group that is hierarchically divided by 2 to the n-th power, such as two-division, four-division, and eight-division, for all branch-line ports, For an increase, it is possible to find a port in log N order time. At this time, if the ONU has already been registered in all the branch ports of the divided group, the port can be found more quickly by excluding that group from the search range. The OLT notifies the RN of the result.

FIG. 10 is a sequence diagram showing a registration method using the batch method. Hereinafter, the contents of the registration method will be further described with reference to FIG.
In the registration sequence shown in FIG. 10, in addition to the control frames defined by the individual method (in the case of FIG. 9), the notation of the following control frames is further defined.

dG (pB, Pk): Downward gate that opens all branches for period Pk dG (pMi, Pk): Downgate that opens branch group Mi for period Pk uGfr (L, Pk): LLID (L) to ONU Up gate (grant period Pk and report compulsory)
RP (L): Report from ONU of LLID (L) (REPORT)
OAMp (L, pJ): An OAM frame that notifies the RN of the association between the LLID (L) and the branch line pJ.

As shown in order from the left in FIG. 10, first, the OLT sends a downlink gate dG (pB, P1) to the access line. Thereafter, the OLT sends an upstream discovery gate uDG (P2) to the access line during the opening period P1.
The RN receives this downstream gate dG (pB, P1) and opens all the branch lines p1 to pN of its own downstream optical switch 7 for the period P1. Further, the RN snoops the upstream discovery gate uDG (P2) that passes in the period P1, and all the branch lines p1 to pN (corresponding to the path of the downstream optical switch in the period P1) of its own upstream optical switch 8 are transmitted in the period P2. Open for a while. (As described here, the control of the optical switches 7 and 8 performed by the RN is subordinate, and the operation of the RN will be omitted in the description of FIG. 10 hereinafter.)

The OLT receives, for example, a registration request RR (a2) from the ONU of the unregistered address a2 as a response of the upstream discovery gate uDG (P2) sent to all the branch lines p1 to pN. Thereafter, the OLT sends a downstream gate dG (pB, P3) to the access line.
During the opening period P4, the OLT sends a registration notification R (a2,1) and an upstream gate uG (1, P4), assigns LLID (1) to the ONU at address a2, and sends the ONU to the period. Grant P4 transmission permission.

  The ONU that has received the registration notification R (a2, 1) sends out a registration response RA (1) during the period P4 when the transmission permission is given. The OLT that has received the registration response RA (1) registers the ONU that issued the response RA (1) as the ONU (a2) of the address a2.

The OLT then performs the port discovery sequence.
In this sequence, the OLT first sends a downlink gate dG (pM0x, P5) to the access line.
The OLT transmits the upstream gate uGfr (1, P6) during the opening period P5, grants transmission permission with forced report in the period P6, and waits for a reply from the ONU having the LLID (1).

In the example of FIG. 10, since the ONU (a2) connected to the branch line p2 sends the report RP (a2), at this time, the ONU (a2) having the LLID (1) is transferred to the branch group pM0x ( = P1, p2).
However, since the branch line group pM0x includes two branch lines p1 and p2, it is not yet known which branch line p1 and p2 in the group the ONU (a2) is connected to.

  Therefore, the OLT further sends a downstream gate dG (pM00, P7) to the access line. The OLT sends the upstream gate uGfr (1, P8) during the opening period P7, grants transmission permission with forced report in the period P8, and returns a report from the ONU (a2) having the LLID (1). Wait for.

In the example shown in FIG. 10, no report is returned even if a predetermined time has elapsed.
Therefore, the OLT further sends a downstream gate dG (pM01, P9) to the access line. The OLT sends the upstream gate uGfr (1, P10) during the opening period P9, grants transmission permission with report compulsion in the period P10, and returns a report from the ONU (a2) having the LLID (1) Wait for.

When the ONU (a2) actually connected to the branch line p2 sends out the report RP (a2) and receives this report RP (a2), the OLT has the ONU (a2) having the LLID (1). Is included in the branch line group pM01 (= p2 only). That is, ONU (a2) is found in the branch line P2.
Thereafter, the OLT sends an OAM frame OAMp (1, p2) to the RN, and notifies the RN that the ONU of the LLID (1) is connected to the branch line p2.

  As described above, according to the registration method using the collective method, the OLT sends out the downward gate dG (pB, Pk) that opens all the branch lines p1 to pN of the downstream optical switches 7 and 8 for a predetermined period Pk. During the period Pk, discovery is performed for an unregistered ONU, and then an uplink gate uGfr (L, Pk) with a report compulsion for a registered (LLID-assigned) ONU is connected to the branch line pJ ( Since the port discovery sequence for transmission is performed while narrowing down J = 1 to N), the ONU is automatically registered including the correspondence even if the correspondence between the ONU and the branch port of the RN is not set in advance. Can do.

  Further, in the registration method using the collective method, branch discovery pJ (J = 1 to N) corresponding to registered ONUs is performed after performing normal discovery with all branch lines p1 to pN of optical switches 7 and 8 being opened. In general, automatic registration of ONUs can be performed more quickly than in the individual method in which discovery is performed for each branch line pJ (J = 1 to N).

In the registration method of the individual method or the batch method, as shown in FIG. 1, unlike the burst-compatible ASON-ONU capable of receiving burst signals, the ONGE is not capable of receiving burst signals and is not capable of receiving burst signals. -In a system that may include ONUs, the switch control unit 10 may register all branch lines p1 to pN (or 10GEPON-ONUs of the downstream optical switch 7 after its registration is completed). A certain branch line) is always open. When the newly registered ONU belongs to the ASON-ONU, the branch line of the downstream optical switch 7 corresponding to the ONU is stopped constantly and switched to the opening according to the downstream gate dG instructed by the OLT.
As a result, the downstream signal to the ONU that does not support burst becomes a continuous signal, and it is possible to prevent the ONU that does not support burst from malfunctioning due to the burst signal and to mix them in the same access line as the ASON-ONU.

[Apply both individually and collectively]
On the other hand, the individual registration method (FIG. 9) and the batch registration method (FIG. 10) are not mutually exclusive, and both of these registration sequences can be performed in one ASON system.
Here, since the ASON system is based on a form in which one ONU is connected to each branch line pJ (J = 1 to N) of the optical switch, this form is assumed in the following comparison.

A feature of the individual method is that discovery is performed for each branch line, so that the upper limit of time required to register all ONUs that want to be registered is suppressed regardless of the number of unregistered ONUs. On the other hand, for a specific ONU, the time from when registration is desired until the registration is completed depends on the order of selection of branch lines, and may be longer.
The feature of the collective method is that discovery is performed for all branch lines, so registration can be done in a relatively short time regardless of which branch line the ONU that wants to register (assuming that the other ONUs do not change) is connected. Is to complete. On the other hand, if there are a large number of ONUs that want to register at the same time, the probability that registration requests will collide increases, and the time required to register all ONUs may increase.

In general, in a normal state in preparation for registration due to ONU circumstances, such as when the ONU is powered on, registration by the batch method is suitable. For the event that the ONU requests registration at the same time, the registration by the individual method is suitable.
Therefore, it is recommended to selectively perform the individual method registration method and the batch method registration method in accordance with the status of the ASON system in one ASON system.

These registration methods may be switched by an operator, or may be automatically switched to the individual method when the collision frequency of registration requests increases in the batch method.
If these methods are generalized, branch lines are grouped, and a batch method is applied to each group. The group with the maximum range is the so-called batch method, and the group with the smallest range is the individual method (the port discovery sequence is unnecessary and is deleted). As an intermediate between them, the range of the group may be adjusted.

  The above-described embodiments are all illustrative and do not limit the scope of the present invention. The technical scope of the present invention is shown not by the above embodiment but by the scope of claims for patent, and includes modifications within the scope equivalent to the structure of the scope of claims for patent.

1 is an overall configuration diagram of an ASON system according to an embodiment of the present invention. It is a schematic block diagram of a downstream optical switch. It is a schematic block diagram of an upstream optical switch. It is a sequence diagram which shows the measuring method of a round trip delay time (RTT). It is a functional block diagram which shows the structure of a station side apparatus. It is a functional block diagram which shows the structure of a home side apparatus. It is a sequence diagram which shows the ranging process which calculates | requires a frequency difference. It is a functional block diagram which shows the structure of the switch control part of an optical switch apparatus. It is a sequence diagram which shows the registration method by an individual system. It is a sequence diagram which shows the registration method by a batch system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Station side apparatus 2 Home side apparatus 3 Optical switch apparatus 4 Optical fiber 5 Optical splitter 7 Downstream optical switch (optical switch part)
8 Upward optical switch (optical switch)
9 WDM splitter 10 Switch control unit dG Down gate uG Up gate

Claims (11)

An optical switch unit capable of selecting the route of the optical signal;
A switch control unit for determining a path and opening timing of an optical signal in the optical switch unit based on a gate frame including data dedicated to the operation of the optical switch unit transmitted by the station side device;
An optical switch device comprising: The optical switch unit includes a downstream optical switch capable of selecting a route of a downstream signal transmitted from the station side device,
The gate frame transmitted by the station side device is a downlink gate in which a destination and a transmission period are described for a downlink burst in which downlink frame sequences are grouped by destination,
The optical switch device according to claim 1, wherein the switch control unit determines a path and opening timing of the downstream optical switch based on the downstream gate. The downlink gate includes a broadcast destination.
3. The optical switch device according to claim 2, wherein when the destination described in the downlink gate is broadcast, the switch control unit opens all the paths of the downlink optical switch. The downlink gate includes a multicast destination,
3. The optical switch device according to claim 2, wherein when the destination described in the down gate is multicast, the switch control unit opens a path of the down optical switch corresponding to the destination. The optical switch unit further includes an upstream optical switch capable of selecting a route of an upstream signal transmitted from the home side device,
The switch control unit determines the opening timing of the upstream optical switch by determining the upstream optical switch opening timing by using an upstream gate in which a transmission source and a transmission period of an upstream burst in which upstream frame sequences are grouped by transmission source. The optical switch device according to claim 2, wherein a route of the upstream optical switch is determined in accordance with a setting of the downstream gate for passing through the optical switch. The uplink gate includes information on a scheduled reception period at the station side device,
The switch control unit obtains a round-trip delay time with the station side device upon reception of the uplink gate for itself,
6. The optical switch device according to claim 5, wherein the opening timing of the upstream optical switch written in the upstream gate is determined by advancing the scheduled reception period written in the upstream gate by the round-trip delay time. The downlink gate includes a broadcast destination.
The optical switch according to claim 5 or 6, wherein when the destination setting of the downstream gate for passing the upstream gate through the downstream optical switch is broadcast, the switch control unit opens all the paths of the upstream optical switch. apparatus. The downlink gate includes a multicast destination,
7. The route of the upstream optical switch corresponding to the destination is opened by the switch control unit when the destination setting of the downstream gate for passing the upstream gate through the downstream optical switch is multicast. The optical switch device described. A station-side device that can be connected to a plurality of home-side devices in a P2MP form via an optical switch device having an optical switch unit capable of selecting an optical signal route,
A control frame processing unit that generates a gate frame including data dedicated to the operation of the optical switch unit;
A station-side device that transmits the generated gate frame to the optical switch device. It is possible to connect to a plurality of home-side devices in the P2MP form via an optical switch device having an optical switch unit capable of selecting an optical signal route, and to the home-side device via the optical switch device. A station side device capable of transmitting a downlink burst,
While measuring the round-trip propagation time of the home device and the frequency difference of the clock with the home device using a plurality of reports for the same home device,
The transmission period of the home-side device described in the upstream gate in which the transmission source and the transmission period are recorded for the upstream burst in which the upstream frame sequence is grouped by transmission source, the reception period for the station-side device is the round-trip propagation time and frequency A station side device characterized by being adjusted by a difference. A station-side device, an optical switch device having an optical switch unit capable of selecting an optical signal route, and a plurality of home-side devices connected to the station-side device in a P2MP configuration via the optical switch device. ASON system,
The station side device generates a gate frame including data dedicated to the operation of the optical switch unit, and transmits the gate frame to the optical switch device in advance,
The optical switch device determines a route and opening timing of the optical switch unit according to the gate frame.

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