JP2002281058A - Optical access network, optical subscriber line terminating device, and line card to be used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical access network capable of efficiently housing IP traffic represented by the Internet in which outgoing traffic is extremely large than incoming traffic and an optical subscriber line terminating device and a line card (giga bit Ethernet (registered trademark) card). SOLUTION: An optical subscriber line terminating device, a large capacity physical line for operating only data communication in an outgoing direction and a bi-directional physical line for carrying out bi-directional communication in incoming and outgoing directions and control communication for controlling the large capacity physical line are arranged between a center side device and a plurality of user side devices. The optical subscriber line terminating device is provided with a function for realizing the termination of the large capacity of physical line for operating only the data communication in the outgoing direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical access network, an optical network unit, and a line card used for the same, and more particularly, to the Internet in which downstream traffic is overwhelmingly greater than upstream traffic. The present invention relates to an optical access network capable of efficiently accommodating IP traffic, an optical network unit, and a line card used therein.

In particular, conventionally provided STM-PDS
System (Synchronous Transfer Mode-Passive Double
If the present invention is applied to Star (synchronous transfer mode-passive double star), it is possible to increase the speed of the downlink line and minimize the cost of additional equipment. Regarding this, it is possible to refer to the description of “Achieving further economical construction of optical PDS system components” in NTT Technical Journal 2000.3.

[0003]

2. Description of the Related Art As a typical conventional optical access network, there is an STM-PDS system. FIG.
FIG. The STM-PDS system is a system in which a plurality of users share one center-side device, and a plurality of ONs are connected to one OLT (Optical Line Terminal) via a star coupler.
U (Optical Network Unit: optical network unit) is connected.

On the center side, routers and nodes are arranged in addition to the OLT. OLT, specifically, telephone and 1
OSU that terminates 0 Mbit / s Ethernet (Op
tical Subscribe Unit: a subscriber line termination panel), a cross-connect for distributing each signal type, and an interface corresponding to the distributed signal. For example,
Telephone analog signals are connected to various nodes from a telephone interface, and 10 Mbit / s Ethernet signals are connected to routers and switches. On the other hand, the service provided by the ONU differs depending on the interface provided by the line card.

[0005] In the transmission in the STM-PDS system, a ping-pong transmission system in which upstream and downstream signals are alternately transmitted on one optical fiber and a case where upstream signals are multiplexed on a star coupler. , A time division multiple access control (TDMA) that controls transmission timing so that uplink signals of each ONU do not collide with each other.
Access) technology. The ping-pong transmission method is a time axis compression bidirectional multiplexing (TCM: Ti) that divides a time for transmitting a signal in an upward direction and a time for transmitting a signal in a downward direction.
This is a transmission system that basically enables bidirectional transmission at one wavelength by using a me compression multiplexing technique.

In the STM-PDS system, the bandwidth of the telephone analog line is allocated to each user in advance, but the bandwidth allocated to Ethernet communication is fairly shared by the users who want to use it. In other words, in Ethernet communication, when only one user is communicating among a plurality of ONUs connected to the OLT on the center side, the maximum available bandwidth is used by this one user, and the plurality of users In the case of simultaneous communication, control is performed so that a band is equally allocated to each user.

When Ethernet communication is performed on the STM-PDS system, a line card having a 10 Mbit / sec Ethernet interface is inserted into the ONU. The interface on the OLT side of this line card is
The STM-PDS system has its own specifications, and Ethernet frames can be converted to STM-PDS within the line card.
It is converted into a signal that enables transmission in the system.

As another example of the optical access network, an ATM-PDS system (Asynchronous Transfer
r Mode-Passive Double Star: Asynchronous transfer mode-passive double star. FIG. 5 shows a schematic diagram thereof. The ATM-PDS system, like the STM-PDS system, shares one optical fiber with a plurality of users via a star coupler, but uses different wavelengths for upstream and downstream signals. A major difference is that an ATM used for asynchronous communication is used for a data link to be used.

[0009] As a transmission method of a signal in the downstream direction in the ATM-PDS system, a broadcast-type common use access system using an optical branching means is used, and in the upstream direction, TDMA control is performed similarly to the STM-PDS system. It is a method. At this time, communication is possible between the OLT and the ONU at a speed of 155 Mbit / s in both the upstream and downstream directions.

[0010] The ATM-PDS system is STM-PDS.
As with the system, telephone and Ethernet communications are distributed to each interface by the OLT cross-connect inside the OLT, and are connected to nodes, routers, and switches. Also, the interface unit inside the OLT and the ONU
In, ATMs are terminated and assembled or disassembled into telephone analog signals or Ethernet frames.

[0011]

When a user uses services such as homepage browsing and content download on the Internet, downlink traffic is overwhelmingly greater than uplink traffic, and downlink traffic is sporadic. (The peak traffic volume is large, but it does not always occur, but occurs at time intervals). In the conventional example, since the communication speed in the downlink direction is the same as the communication speed in the uplink direction, an unnecessary band is allocated to the uplink direction, and there is a problem that the equipment efficiency is deteriorated.

In addition, since the bandwidth of Ethernet communication provided by the STM-PDS system itself is as low as 10 Mbit / sec, it is impossible to provide a bandwidth sufficient to cope with the recent increase in large-capacity IP traffic. . When speeding up the line of the STM-PDS system, there is a problem in the system that the transmission method is ping-pong transmission, as described above, so that a speed twice as high as the information transmission speed is required.

Further, since guard time is required in both the up direction and the down direction, there is also a problem that the bandwidth is substantially reduced. In addition, OL of center side equipment
It is necessary to replace not only T but also the ONU main body on the user side with one corresponding to high speed. Therefore, it is considered that the increase in traffic capacity due to the speeding-up significantly increases the equipment cost.

[0014] On the other hand, the ATM-PDS system attempts to realize high speed by using different wavelength bands in the upstream and downstream directions, but is not widely used as compared with the STM-PDS system. Also, AT for data link
The use of M results in a costly system.

An object of the present invention is to solve the above-mentioned problems and to provide an optical access system capable of efficiently accommodating IP traffic typified by the Internet, in which the downstream traffic is overwhelmingly greater than the upstream traffic. An object of the present invention is to provide a network, an optical network unit, and a line card used therein.

[0016]

In order to achieve the above object, a line card according to the present invention comprises at least a 10-bit interface (Ten Bit Interface) and a gigabit interface converter (Gigabit Interface Converter).
and a PMD service interface (PMD Server).
vice Interface) PMD_UNITDAT.request
A signal is branched, one of which is connected to the gigabit interface converter, and the other is turned back at the PMD service interface point to form a PMD_UNIT.
PMA signal input to the 10-bit interface as a DAT.indicate signal and regardless of the presence or absence of optical input to the gigabit interface converter
The _SIGNAL.indicate signal is configured to be at a high level.

Further, an optical access network system according to the present invention is an optical access network system using the above-mentioned gigabit Ethernet card, wherein an optical signal is transmitted between one center device and each of the center devices. A plurality of user-side devices that perform communication, and an optical network unit between the center-side device and the plurality of user-side devices; and a large-capacity physical line that performs only downlink data communication. And having a bidirectional physical line for performing bidirectional communication in the uplink and downlink directions and control communication for controlling the large-capacity physical line, and having an uplink direction from the user-side device to the center device. Communication is performed by a time-division multiple access control method in which a plurality of users share a band in time, and from the center-side device. The communication in the down direction to the user-side device is configured to be performed by a broadcast-type medium sharing access method in which an optical signal from the center side is branched and distributed to each of the user-side devices. It is.

An optical network unit according to the present invention is an optical network unit constituting the above-mentioned optical access network system, and uses the above-mentioned gigabit Ethernet card to transmit the downlink data. It is characterized by realizing a large capacity physical line termination function for performing only communication.

Further, another optical access network system according to the present invention includes one center device and a plurality of user devices each of which communicates with the center device by an optical signal. Between the center-side device and the plurality of user-side devices, an optical network unit, and a large-capacity physical line that performs only downlink data communication, and uplink and downlink bidirectional communication. A bidirectional physical line for performing control communication for controlling a large-capacity physical line, and upstream communication from the user-side device to the center device temporally shares a band with a plurality of users. Performed by a time-division multiplexed access control method, and the downstream communication from the center-side device to the user-side device branches an optical signal from the center-side device to each of the respective devices. An optical access network system configured to perform a broadcast type media sharing access method distributed to a user side device, wherein the optical network unit outputs a signal from a gigabit interface converter of a transmission side line card in the optical network unit. The optical signal is split by an optical splitter, one of which is connected to a large-capacity physical line dedicated for downlink, and the other is fed back to the optical receiving unit of the gigabit interface converter. .

Still further, another optical network unit according to the present invention is an optical network unit constituting the above optical access network system, wherein the optical network unit comprises a gigabit interface converter of the transmission side line card. The output optical signal is split by an optical splitter, one of which is connected to a downlink large-capacity physical line, and the other is fed back to the optical receiving unit of the gigabit interface converter and input. is there.

The basic concept of the present invention is a large-capacity physical line that performs only downlink data communication and a physical line that performs both uplink and downlink bidirectional communication and controls both downlink and large-capacity physical lines. I have a line. As described above, by using a large-capacity line dedicated to downlink, sporadic large-capacity traffic in the downlink direction can be efficiently handled.

In the present invention, basically, Ethernet is used which performs communication by performing nB / mB block coding (n, m: integer) on a signal dedicated to downlink. Ethernet is a data link line widely used in LANs and the like, and is being standardized. It is possible to construct an inexpensive system compared to ATM. The communication speed provided by commercially available Ethernet is 1 gigabit / second, but the standard of 10 gigabit / second Ethernet is also being promoted, and a further increase in communication speed and
Price reduction is expected.

When the present invention is applied to the STM-PDS system, the bandwidth of the downlink data link line is 10 Mbit / s at the maximum with the minimum equipment cost increase, but is reduced to 1 Gbit / s. Significantly faster. Hereinafter, before describing an embodiment of the present invention, an optical access network on which the embodiment is based will be described.

FIG. 6 shows a configuration of an optical access network on which the present invention is based. The center-side device receives telephone analog signals and IPs from the ONUs 7-1 to 7-n.
An OLT 1 for transmitting and receiving data communication such as a signal, a control device 2 for receiving a request from a user and collecting billing information and contract information, a server 3 having an interface for a downlink-only large-capacity physical line, and a downlink 3. It comprises a wavelength demultiplexing coupler 4 for demultiplexing a signal and an upstream signal.

The server 3 needs to replace the laser used in the interface with a 1.5 μm band laser different from the 1.3 μm wavelength used in the STM-PDS system. 1.3μ output from OLT1
The wavelength in the m band and the wavelength in the 1.5 μm band output from the server 3 are wavelength-multiplexed by the wavelength demultiplexing coupler 4. Although wavelength multiplexing is possible with ordinary star couplers, STM
In the PDS system, since the 1.3 μm band signal is also used in the upstream direction, when a star coupler is used, the 1.3 μm band signal in the upstream direction is output as a 1.5 μm band signal. In this case, the wavelength multiplexing / demultiplexing coupler 4 is used because it is returned to the direction of the optical device. The wavelength multiplexed light is transmitted on the optical fiber 5 and split by the number of users by the star coupler 6, and the ONUs 7-1 to 7-
n.

FIG. 7 shows the configuration of the ONU and the line card used here. The wavelength-division multiplexed light input to the ONUs 7-1 to 7-n is again converted by the wavelength-division demultiplexing coupler 9 into 1.
It is separated into a wavelength of 3 μm band and a wavelength of 1.5 μm band.
The 1.3 μm band wavelength is processed as a signal of the STM-PDS system. If the signal is an analog signal of a telephone, the signal is transmitted to the telephone line card 10 and connected to the telephone, and if the signal is packet data, The data is directly input to the Ethernet line card 12.

Upstream signals from the ONUs 7-1 to 7-n are controlled by the TDMA controller 16 according to the TDMA method and transmitted from the STM transceiver 17 to the OLT 1. Here, since the signals of the ONUs 7-1 to 7-n are respectively subjected to TDMA control, the signals reach the OLT 1 without colliding on the optical fiber 5. O
In the LT1, a telephone analog signal and an Ethernet signal are separated by a cross-connect and reach their respective interface units. The telephone analog signal is connected to a node, and the Ethernet signal is connected to a router or a switch.

When each of the ONUs 7-1 to 7-n receives data using a downlink large-capacity physical line (a line in a wavelength band of 1.5 μm), a bidirectional transmission line of 1.3 μm wavelength band is used as a control line. Use a communication line. A request signal from the terminal is transmitted to the optical fiber 5 via the Ethernet line card 11, the TDMA controller 16, the STM transceiver 17, and the wavelength division multiplexing / demultiplexing coupler 9.

At this time, the request signal is sent out as an Ethernet signal controlled by TDMA, as in normal uplink data communication. The request signal received at the center passes through the wavelength separation coupler 4 and the OLT 1 and is input to a router or a switch. When the received signal is a request signal, the router or the switch sends this signal to the control device 2. The control device 2 reads the transmission source address from the received request signal, controls the billing and the like, and, at the same time, transmits the transmission destination address, that is, the downlink dedicated large capacity physical line card 12 Determine the address.

Here, the address of the Ethernet line card 11 provided in a certain ONU terminal and the address of the downlink dedicated large-capacity physical line line card 12 have a one-to-one correspondence. Is prepared in advance. If transmission is possible, the control device 2 notifies the server 3 of the destination address, and the server 3 outputs the requested data to the destination address at a wavelength of 1.5 μm.

The above is the outline of the configuration and operation of the optical access network on which the present invention is based. Hereinafter, an embodiment in which the present invention is applied to an optical access network having such a configuration and an operation function will be described.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] This embodiment relates to claims 1 to 3, and realizes new functions using a gigabit Ethernet card having new features. . The Gigabit Ethernet card has 1000BASE-X that performs communication using optical signals,
There is 1000BASE-T that performs communication by electric signals, but here, it is assumed that only 1000BASE-X is handled assuming application to STM-PDS.

First, according to FIG.
From the optical interface point of the ET Gigabit Ethernet card to the PMA service interface (PMA Servi
ce Interface) will be described. In FIG. 1, reference numeral 18 denotes a gigabit interface converter for performing optical / electric conversion, and reference numeral 19 denotes a 10-bit interface for performing serial / parallel conversion and reproduction of 1/20 clock.

The optical signal input from the outside is converted into an electric signal by a gigabit interface converter 18,
It is input to the 10-bit interface 19 as a PMD_UNITDAT.indicate signal. In the 10-bit interface 19, the PMD_UNITDAT.indicate signal is converted into a 10-bit parallel signal, and at the same time, the PMD_U
Regenerate 1/20 clocks from the NITDAT.indicate signal and pass them to the PMA service interface.

At this time, the gigabit interface converter 18 determines whether there is an optical signal input or not by PMA_SIGNAL.i.
It is passed to the PMA service interface as an ndicate signal. Here, gigabit interface converter 1
8, when no optical signal is input, the PMA_RX_CLK and PMA_UNIT
DAT.indicate is not input and PMA_SIGN
Since LOW is input as AL.indicate,
The PMA service interface notifies the upper layer of an error signal, and no Ethernet communication is performed.

FIG. 2 shows a gigabit Ethernet card improved for a downlink-only large-capacity physical line in this embodiment. The PMD_UNITDAT.request signal output from the 10-bit interface 19 is branched into two, one of which is a gigabit interface converter 18.
And the other is looped back at the PMD service interface point and input to the 10-bit interface 19 as a PMD_UNITDAT.indicate signal.

In the 10-bit interface 19, the PMA_RX_CLK and PMA_UNITDAT.
It outputs an indicate signal and passes it to the PMA service interface. The PMA_SIGNAL.indicate signal is set to be high regardless of the presence or absence of optical input to the gigabit interface converter 18.

As a result, even when no optical signal is input to the gigabit interface converter 18, data transmission becomes possible, and the present invention can be applied to a downlink dedicated large capacity physical line card.

However, the Gigabit Ethernet card has an auto-negotiation function. The auto negotiation function is a function for automatically setting whether each card performs full-duplex communication or half-duplex communication when NICs are connected to each other. If it is known that the cards communicate with each other in full-duplex, this function can be turned off and the communication can be set as full-duplex communication.

In the present embodiment, a card dedicated to downlink, that is, a card that can output only a downlink signal is proposed. Therefore, if conventional functions are used, auto-negotiation cannot be performed when the cards are connected to each other. An error occurs and stops working. Therefore, the Gigabit Ethernet card auto-negotiation function is turned off from the beginning to deal with this.

[Embodiment 2] This embodiment relates to claims 4 and 5. The difference from the first embodiment is not the electric stage,
The point is that a line card dedicated to downlink is realized by folding the signal at the optical stage. FIG. 3 shows a gigabit Ethernet card improved for a downlink-only large-capacity physical line in this embodiment. Here, reference numeral 20 denotes an optical splitter.

Gigabit interface converter 18
Is split into two by the optical splitter 20,
One is connected to a large-capacity physical line for downlink, and the other is looped back and input to the gigabit interface converter 18. The optical signal input after being turned back is converted into an electric signal by a gigabit interface converter 18 and input to a 10-bit interface 19, and PMA_RX_CLK and PMA_U are input by the 10-bit interface 19.
An NITDAT.indicate signal is passed to the PMA service interface.

Since the optical signal is input to the gigabit interface converter 18, the PMA_SIGNAL.
The indicate signal has a high level. As a result, data communication becomes possible, and the present invention can be applied to a downlink dedicated large-capacity physical line card. However, at this time, the auto-negotiation function of the Gigabit Ethernet card needs to be turned off for the same reason as described in the first embodiment.

Here, a supplementary explanation will be given for the signals shown in FIGS. These are all IEEE80
It is specified in 2.3. PMD_UNITDAT.indicate: A 1.25 Gbit / sec serial signal obtained by directly converting an optical signal into an electric signal PMA_UNITDAT.indicate: A signal obtained by converting a 1.25 Gbit / sec serial signal into a 10-bit parallel signal PMA_RX_CLK: PMD_UNITDAT.indicate
1/20 clock reproduced from the signal PMA_UNITDAT.request: 10-bit parallel signal passed from the upper layer

PMD_UNITDAT.request: PMA_
MUX the UNIDAT.request signal to 1.25 Gbit
/ Second serial signal PMA_SIGNAL.indicate: High when light is input to the gigabit interface converter 18;
Outputs Low when light is not input (If Low, it is recognized as fail in the above layer and communication is not performed) For downlink only card, use only * request signal, * i
The ndicate signal is not actually used, but if the * indicate signal is not input, the card issues an error and does not operate.

The above embodiments are merely examples of the present invention, and the present invention should not be limited to these embodiments. Appropriate changes and modifications can be made without departing from the spirit of the present invention. It goes without saying that it may be performed.

[0047]

As described in detail above, when the present invention is applied to the STM-PDS system, bidirectional communication of 10 Mbit / s per user can be performed, and a maximum of 1 Mbit / s can be achieved.
Gigabit / second downlink communication can be shared and used by users. At this time, it is possible to provide the STM-PDS system without making significant changes, and it is possible to realize the STM-PDS system with some functions of the line card and the OLT. In addition, high-speed lines of 1 gigabit / sec.
The effect of being able to provide at a sufficiently low cost as compared with the S system is also obtained.

[Brief description of the drawings]

FIG. 1 shows a general Gigabit Ethernet card (10
00BASE-X).

FIG. 2 is a configuration diagram of a line card dedicated to downlink according to one embodiment of the present invention.

FIG. 3 is a configuration diagram of a downlink dedicated line card according to another embodiment of the present invention.

FIG. 4 is a schematic diagram of a conventional STM-PDS system.

FIG. 5 is a schematic diagram of a conventional ATM-PDS system.

FIG. 6 is a configuration diagram of an optical access network on which the present invention is based.

FIG. 7 is a configuration diagram of an ONU and a line card used in the optical access network shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 OLT 2 control device 3 content server 4 wavelength multiplexing / demultiplexing coupler 5 optical fiber 6 star coupler 7-1 to 7-n ONU 8-1 to 8-n terminal or telephone 9 wavelength multiplexing / demultiplexing coupler for ONU 10 telephone line card 11 Ethernet line card 12 Gigabit Ethernet line card 16 TDMA controller 17 STM transceiver 18 Gigabit interface converter 19 10-bit interface 20 Optical splitter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/20

Claims (5)

[Claims] 1. A gigabit Ethernet card having at least a 10-bit interface and a gigabit interface converter, wherein a PMD_UNI at a PMD service interface point.
The TDAT.request signal is branched, one of which is connected to the gigabit interface converter, the other is looped back at the PMD service interface point and input to the 10-bit interface as a PMD_UNITDAT.indicate signal, and A gigabit Ethernet card, wherein the PMA_SIGNAL.indicate signal is at a high level regardless of the presence or absence of optical input to the gigabit interface converter. 2. An optical access network system using the Gigabit Ethernet card according to claim 1, wherein a plurality of users, each communicating with an optical signal between one center device and the center device. And an optical line terminal between the center-side device and the plurality of user-side devices, and a large-capacity physical line that performs only data communication in the downlink direction, And a bidirectional physical line for performing control communication for controlling the large-capacity physical line in the direction, and uplink communication from the user-side device to the center device is performed by a plurality of users. Performed by a time-division multiplexing access control method that temporally shares a band, and downlink communication from the center-side device to the user-side device is the Optical access network system, characterized in that branches an optical signal is configured to perform the broadcast type of shared medium access method to be distributed to each user device from the centers side. 3. An optical network unit constituting the optical access network system according to claim 2, wherein only the downlink data communication is performed using the gigabit Ethernet card according to claim 1. An optical subscriber line terminating device for realizing a function of terminating a large-capacity physical line. 4. A device comprising one center-side device and a plurality of user-side devices, each of which communicates with the center-side device by an optical signal, wherein the center-side device, the plurality of user-side devices, In the meantime, the optical network unit, and a large-capacity physical line that performs only data communication in the down direction, and bidirectional communication in the up and down directions and control communication for controlling the large-capacity physical line. Having a two-way physical line for performing, the uplink communication from the user side device to the center device is performed by a time division multiple access control system in which a plurality of users time-share a band, In the downstream communication from the center device to the user device, a broadcast-type media sharing action for branching an optical signal from the center device and distributing it to each of the user devices. An optical access network system configured to perform by an optical subscriber line system, wherein in the optical network unit, an optical signal output from a gigabit interface converter of a transmission side line card is split by an optical splitter. The optical access network system is connected to a large-capacity physical line dedicated to downlink, and the other is input to the optical receiving unit of the gigabit interface converter in a folded manner. 5. The optical network unit according to claim 4, wherein an optical signal output from a gigabit interface converter of the transmitting line card is split by an optical splitter. An optical network unit, wherein one is connected to a large-capacity physical line dedicated to downlink and the other is fed back to the optical receiver of the gigabit interface converter.