JP4710487B2 - Data transmission method, optical transmission system, and dummy data insertion device - Google Patents

Description

  The present invention relates to a data transmission method, an optical transmission system, and a dummy data insertion device, and more specifically to a system for transmitting data and video at different wavelengths.

  In the optical subscriber line, simultaneous data communication and broadcasting services are being planned and partially put into practical use. For example, in GE-PON (Gigabit Ethernet (registered trademark) Passive Optical Network), a three-wave multiplexing system that multiplexes a downstream broadcast signal with a wavelength of 1.55 μm to data communication with a downstream wavelength of 1.49 μm and an upstream wavelength of 1.31 μm. Studies are ongoing (see Patent Documents 1, 2, and 3).

In the GE-PON system conforming to IEEE 802.3ah, when there is no downlink data signal, the optical terminal unit OLT (Optical Line Terminal) of the center station may transmit an idle pattern to the optical terminal unit ONU (Optical Network Unit) of the user. It is prescribed. The idle pattern is defined as a repetition of “001111110101001000101” as /I2/=/K28.5/D16.2. It is known that when a downstream broadcast signal having a wavelength of 1.55 μm is multiplexed for data transmission using such an idle pattern, the periodicity of the idle pattern becomes stimulated Raman scattering and interferes with the broadcast signal. That is, on the optical transmission line, the bit rate of the optical signal is 1.25 Gbps by 8B / 10B conversion. An idle pattern with a 20-bit period is
1.25 (Gbps) / 20 (bit) = 62.5 (MHz)
Thus, a frequency component having a period of 62.5 (MHz) is generated. As a result, stimulated Raman scattering occurs at a frequency that is an integral multiple of a 62.5 (MHz) period, and this enters the video signal band of the broadcast signal.
Japanese Patent Laying-Open No. 2005-210688 JP 2004-215247 A Japanese Patent Laying-Open No. 2005-027302

  The method of scrambling the idle pattern is not applicable to the existing GE-PON system, and the OLT must be exchanged.

  GE-PON systems are installed in large quantities without waiting for the introduction of three-wave multiplexing, and a method that can reduce interference with video signals without replacing existing systems is desired.

  An object of the present invention is to provide a data transmission method, an optical transmission system, and a dummy data insertion device that satisfy such a demand.

The data transmission method according to the present invention is an OLT that converts a downlink data signal input from a higher-level network device into a data signal light having a first wavelength, and outputs a predetermined idle pattern when there is no downlink data signal. An OLT, a video signal transmitting device that generates a video signal light carrying a video signal having a second wavelength different from the first wavelength, a data signal light output from the OLT, and a video signal transmitting device A WDM optical coupler for multiplexing video signal light to be output; one or more subscriber devices; and an optical transmission path for transmitting an optical signal output from the WDM optical coupler to the one or more subscriber devices. Applies to optical transmission systems. The presence / absence of the downlink data output from the host network device is detected. Then, when the downlink data is not, it supplies the dummy data is discarded in and passed through the OLT the subscriber unit to the OLT. The dummy data is carried in a frame having any one of an unused multicast address, an unused VLAN-ID, and an unused LLID as a header.

An optical transmission system according to the present invention is an OLT that converts a downlink data signal input to an uplink port into a data signal light of a first wavelength, and outputs a predetermined idle pattern when there is no downlink data signal. An OLT, a video signal transmitting device that generates a video signal light carrying a video signal having a second wavelength different from the first wavelength, a data signal light output from the OLT, and a video signal transmitting device A WDM optical coupler for multiplexing video signal light to be output, one or more subscriber devices, an optical transmission path for transmitting an optical signal output from the WDM optical coupler to the one or more subscriber devices, and an upper network When the downlink data output from the device is supplied to the uplink port as the downlink data signal, and there is no downlink data from the upper network device, The dummy data is discarded in and the subscriber unit through the LT; and a dummy data insertion device for supplying as the downlink data signal, the dummy data is an unused multicast address as a header, an unused VLAN-ID and It is carried by a frame having any one of unused LLIDs .

An optical transmission system according to the present invention carries an OLT that converts a downlink data signal from a higher-level network device into data signal light of a first wavelength, and a video signal of a second wavelength that is different from the first wavelength. A video signal transmitter for generating video signal light, a data signal light output from the OLT, a WDM optical coupler for multiplexing the video signal light output from the video signal transmitter, and one or more subscriber devices , An optical transmission system comprising an optical transmission path for transmitting an optical signal output from the WDM optical coupler to the one or more subscriber devices, and when the OLT does not have the downlink data signal, the dummy data is discarded by the subscriber unit to output as the downlink data signal, the dummy data is an unused multicast address as a header, an unused VLAN-ID and unused L Characterized in that it is carried in a frame having any one of the ID.

The dummy data insertion device according to the present invention transmits a downlink data signal and a video signal to subscriber devices via light transmission paths using light of different wavelengths, and outputs a predetermined idle pattern when there is no downlink data signal. A dummy data insertion device arranged between the data / video transmission system and the higher-level network device, the buffer temporarily storing downlink data output from the higher-level network device, and the data / video transmission system A dummy data generator for generating dummy data that can be transmitted and discarded by the subscriber device, and when there is the downlink data in the buffer, supply output data of the buffer to the data / video transmission system, The dummy output from the dummy data generator when there is no downstream data in the buffer The chromatography data; and a selector for supplying to the data / video transmission system, the dummy data is an unused multicast address as the header, it is conveyed by a frame having any one unused VLAN-ID and unused LLID characterized in that that.

  According to the present invention, it is possible to reduce the opportunity to transmit a downstream optical signal having an idle pattern having a frequency component that interferes with video signal light. Thereby, the bad influence with respect to a video signal can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention. In this embodiment, a dummy data insertion device 32 is added to the existing OLT 10. Since the optical signal carrying the uplink data output from the subscriber apparatus does not interfere with the video signal transmitted in the downlink direction, the apparatus relating to the uplink data is omitted in this embodiment.

  In the center station, an OLT 10, a video signal transmission device 12, and a WDM coupler 14 are arranged. When there is downlink data, the OLT 10 outputs a downlink data signal light having a wavelength of 1.49 μm that carries downlink data to the WDM coupler 14, and when there is no downlink data, the OLT 10 outputs a signal light having a wavelength of 1.49 μm that carries an idle pattern. Output to the coupler 14. The video signal transmitter 12 outputs signal light having a wavelength of 1.55 μm for carrying the video signal. The WDM optical coupler 14 multiplexes the signal light with a wavelength of 1.49 μm output from the OLT 10 and the video signal light with a wavelength of 1.55 μm output from the video signal transmitter 12.

  The signal light wavelength-multiplexed by the WDM optical coupler 14 is transmitted through the optical fiber 16 and enters the optical splitter 18. The optical splitter 18 divides the optical signal from the optical fiber 16 into n, and outputs each divided light to the optical fibers 20-1 to 20-n. The split light transmitted through the optical fibers 20-1 to 20-n is incident on the subscriber units 22-1 to 22-n.

  The subscriber unit 22-1 includes a WDM optical coupler 24 that separates a data signal light having a wavelength of 1.49 μm and a video signal light having a wavelength of 1.55 μm, a data ONU (D-ONU) 26, and a video signal signal. The ONU (V-ONU) 28 is provided. The D-ONU 26 converts the data signal light having a wavelength of 1.49 μm from the WDM optical coupler 24 into an electric signal and outputs it. The V-ONU 28 converts the video signal light having a wavelength of 1.55 μm from the WDM optical coupler 24 into an electric signal and outputs it. The other subscriber units 22-2 to 22-n have the same configuration and functions as the subscriber unit 22-1. Some users have only one of the D-ONU 26 and the V-ONU 28.

  The above configuration is not different from the conventional one. In the present embodiment, a dummy data insertion device 32 is further arranged between the LAN switch 30 connected to the upper network and the uplink port of the OLT 10. The LAN switch 30 is an L2 (Layer 2) switch corresponding to, for example, Ethernet (registered trademark). The dummy data insertion device 32 monitors the presence / absence of downlink data from the LAN switch 30. When there is no downlink data, the dummy data insertion device 32 can pass through the OLT 10, but the D-ONU 26 of the subscriber devices 22-1 to 22-n does not receive or This is a device that supplies dummy data that is ignored to the OLT 10. Details of the dummy data will be described later.

  The dummy data insertion device 32 includes a buffer 34 for temporarily storing data from the LAN switch 30, a dummy data generation device 36 for generating dummy data, and output data of the buffer 34 or dummy data generated by the dummy data generation device 36. A selector 38 to be selected and a switch control circuit 40 to control the selector 38 are provided. The selector 38 normally selects the output of the buffer 34. The switch control circuit 40 detects whether or not the downlink data to be supplied to the OLT 10 exists in the buffer 34, and when the downlink data does not exist in the buffer 34, selects the output of the dummy data generator 36 for the selector 38. Let

  The buffer 34 adjusts the rate of the downlink data from the LAN switch 30 and outputs it to the selector 38. The switch control circuit 40 constantly monitors whether or not there is downlink data to be supplied to the OLT 10 in the buffer 34. If there is no downlink data to be supplied to the OLT 10 in the buffer 34, the dummy data generating device 36. Simultaneously with outputting dummy data, the selector 38 is controlled to select the output of the dummy data generator 36. Thereby, in a situation where downlink data is not supplied from the LAN switch 30, the dummy data insertion device 32 supplies dummy data to the OLT 10.

  The dummy data output from the dummy data insertion device 32 passes through the OLT 10 and is connected to each subscriber device 22-1 via the WDM optical coupler 14, the optical fiber 16, the optical splitter 18, and the optical fibers 20-1 to 20-n. It enters the D-ONU 26 of ˜22-n. Since the dummy data is transmitted in the downstream direction, the OLT 10 does not generate an idle pattern of a prescribed pattern. The OLT 10 generates an idle pattern only for the interframe gap. If the downstream signal light that carries the dummy data does not interfere with the video signal light output from the video signal transmission device 12 or if there is little, the adverse effect on the video signal that has been problematic in the past can be eliminated or reduced. .

  Details of the dummy data will be described. The dummy data must first pass through the OLT 10 and be discarded by the D-ONU 26 of all the subscriber devices 22-1 to 22-n. This can be realized, for example, by transmitting dummy data in a frame using an unused multicast address or an unused VLAN-ID (Virtual Local Area Network-Identifier). Since the unused multicast address or unused VLAN-ID under the control of the OLT 10 is known in advance, these data are stored in the switch control circuit 40 or the dummy data generator 36. For example, when 32 ONUs are connected and 1 to 32 VLAN-IDs are used, a numerical value of 33 or more, for example, 100 VLAN-IDs is used.

  In order to satisfy these conditions, the dummy data generator 36 generates a dummy data frame including these unused multicast addresses or unused VLAN-IDs in accordance with a trigger signal from the switch control circuit 40. When the switch control circuit 40 stores the unused multicast address or the unused VLAN-ID, the switch control circuit 40 supplies the unused multicast address or the unused VLAN-ID together with the trigger signal to the dummy data generating device 36. . The unused multicast address or unused VLAN-ID accommodated in the dummy data frame output from the dummy data generator 36 is preferably changed for each frame, preferably randomly, in order to avoid periodicity.

  In order to eliminate or reduce the influence on the video signal, it is sufficient that there is no peak in the video signal band or the peak power is small even if there is a peak. That is, it suffices if there is no periodicity or the peak power in the video signal frequency band is small. For example, since the idle pattern / I2 / of GE-PON has a 20-bit period, a peak appears at a frequency that is an integral multiple of 62.5 MHz. If the cycle of the idle pattern is 40 bits, a peak appears at a frequency that is an integral multiple of 31.25 MHz. Since the total power of interference due to stimulated Raman scattering is constant regardless of the period of the idle pattern, in this case, the number of peaks is doubled, but the power per peak is halved by simple calculation. In other words, the longer the period, the smaller the peak power and the less interference with the video signal.

  In order to reduce the peak power within the video signal band, for example, a random pattern or a pseudo random pattern (PN sequence) having a sufficiently large period may be inserted into the payload of the Ethernet frame. FIG. 2 shows a frame configuration example. 2A shows a basic structure of an Ethernet frame, FIG. 2B shows a frame structure with an IP header, and FIG. 2C shows a frame structure in which a TCP / UDP header is further added. When the payload includes an IP header and / or a TCP / UDP header, the remaining portion of the payload is a random pattern.

  Furthermore, the periodicity of the dummy data can be reduced by making the frame length of the Ethernet frame random. However, a fixed length may be used in consideration of the degree of interference received by the video signal. For example, even if it is a fixed length Ethernet frame of 64 bytes (84 bytes by adding the minimum interframe gap and preamble), this frame is transmitted in the PON section with a period of 840 bits. The peak power is reduced to 20/840 = 1/42 compared to the case where the idle pattern is continuous, and the influence on the video signal is also reduced according to this reduction rate.

  The embodiment in which the dummy data insertion device 32 is inserted between the existing OLT 10 and the LAN switch 30 has been described. With this configuration, it is possible to reduce the adverse effect of the downstream data signal on the video signal when the data communication / broadcasting combined service using three wavelengths is performed with the existing OLT as it is.

  Of course, the existing OLT may be replaced with an OLT in which the dummy data insertion device 32 is incorporated. In this case, the new OLT may output dummy data when there is no downlink data signal, and may output the existing idle pattern or dummy data for the interframe gap. Obviously, it is convenient to use an OLT in which a dummy data insertion device 32 is incorporated when a new PON system with three wavelengths that integrates data communication / broadcasting is introduced. The dummy data only needs to be discarded by the ONU, and an unused LLID (Logical Link Identifier) can be used in addition to the unused multicast address or the unused VLAN-ID.

  When the GE-PON system itself can be newly laid, a function of discarding an unknown unicast frame at the ONU may be installed, and the unknown unicast may be used as a dummy data header. In addition, when there is specific information in a part of the header, the ONU may have a function of discarding the data frame, and the specific information may be embedded in the header of the dummy data.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

It is a schematic block diagram of one Example of this invention. It is an example of a frame structure of dummy data in the present embodiment.

Explanation of symbols

10: OLT
12: Video signal transmitter 14: WDM optical coupler 16: Optical fiber 18: Optical splitters 20-1 to 20-n: Optical fibers 22-1 to 22-n: Subscriber device 24: WDM coupler 26: ONU for data
28: Video ONU
30: LAN switch 32: Dummy data insertion device 34: Buffer 36: Dummy data generation device 38: Switch 40: Switch control circuit

Claims (14)

An OLT (10) that converts a downlink data signal input from the higher-level network device (30) into a data signal light of the first wavelength, and outputs a predetermined idle pattern when there is no downlink data signal. )When,
A video signal transmitting device (12) for generating a video signal light carrying a video signal having a second wavelength different from the first wavelength;
A WDM optical coupler (14) for combining the data signal light output from the OLT (10) and the video signal light output from the video signal transmission device;
One or more subscriber units (22-1 to 22-n);
Optical transmission lines (16, 18, 20-1 to 20-n) for transmitting optical signals output from the WDM optical coupler (14) to the one or more subscriber devices (22-1 to 22-n)
In an optical transmission system comprising:
Detect the presence or absence of the downlink data output from the upper network device,
When there is no downlink data, dummy data that passes through the OLT (10) and is discarded by the subscriber device is supplied to the OLT (10) .
The data transmission method , wherein the dummy data is carried in a frame having any one of an unused multicast address, an unused VLAN-ID, and an unused LLID as a header . The data transmission method according to claim 1 , wherein the header of the dummy data is changed at a predetermined cycle. The data transmission method according to claim 1 or 2 , wherein the dummy data includes a random pattern or a pseudo-random pattern arranged in a payload having a predetermined frame structure. The data transmission method according to any one of claims 1 to 3 , wherein a frame length of the frame carrying the dummy data is random. An OLT (10) for converting a downlink data signal input to an uplink port into a data signal light of a first wavelength, and outputting a predetermined idle pattern when there is no downlink data signal;
A video signal transmitting device (12) for generating a video signal light carrying a video signal having a second wavelength different from the first wavelength;
A WDM optical coupler (14) for combining the data signal light output from the OLT (10) and the video signal light output from the video signal transmission device;
One or more subscriber units (22-1 to 22-n);
An optical transmission line (16, 18, 20-1 to 20-n) for transmitting an optical signal output from the WDM optical coupler (14) to the one or more subscriber units (22-1 to 22-n); ,
The downlink data output from the upper network device is supplied to the uplink port as the downlink data signal, and when there is no downlink data from the upper network device, the OLT (10) passes and the subscriber device Dummy data insertion device (32) for supplying the dummy data discarded in step S3 as the downlink data signal
Provided with a door,
The optical transmission system , wherein the dummy data is carried in a frame having any one of an unused multicast address, an unused VLAN-ID, and an unused LLID as a header . The dummy data insertion device (32)
A buffer (34) for temporarily storing the downlink data output from the host network device;
A dummy data generator (36) for generating the dummy data;
When there is the downlink data in the buffer (34), the output data of the buffer (34) is supplied to the uplink port, and when there is no downlink data in the buffer (34), the dummy data generator Selector (38) for supplying the dummy data output from (36) to the uplink port
The optical transmission system according to claim 5 , further comprising: An OLT (10, 32) for converting a downstream data signal from the host network device into a data signal light of the first wavelength;
A video signal transmitting device (12) for generating a video signal light carrying a video signal having a second wavelength different from the first wavelength;
A WDM optical coupler (14) for combining the data signal light output from the OLT (10) and the video signal light output from the video signal transmission device;
One or more subscriber units (22-1 to 22-n);
Optical transmission lines (16, 18, 20-1 to 20-n) for transmitting optical signals output from the WDM optical coupler (14) to the one or more subscriber devices (22-1 to 22-n)
An optical transmission system comprising:
When the OLT (10, 32) does not have the downlink data signal, the OLT (10, 32) outputs dummy data discarded by the subscriber device as the downlink data signal ,
The optical transmission system , wherein the dummy data is carried in a frame having any one of an unused multicast address, an unused VLAN-ID, and an unused LLID as a header . The optical transmission system according to claim 5 , wherein the header of the dummy data is changed at a predetermined cycle. The dummy data, the optical transmission system according to any one of claims 5 to 8, characterized in that it comprises a random pattern or a pseudo-random pattern is placed in the payload of a predetermined frame structure. The optical transmission system according to any one of claims 5 to 9 frame length of the frame is a random for transporting the dummy data. The downlink data signal and the video signal are transmitted to the subscriber units (22-1 to 22-n) through the optical transmission line with light having different wavelengths, and a predetermined idle pattern is output when there is no downlink data signal. A dummy data insertion device disposed between a data / video transmission system and a host network device,
A buffer (34) for temporarily storing downlink data output from the host network device;
A dummy data generating device (36) for generating dummy data that can be transmitted in the data / video transmission system and discarded by the subscriber device;
When there is the downlink data in the buffer (34), the output data of the buffer (34) is supplied to the data / video transmission system, and when there is no downlink data in the buffer (34), the dummy data A selector (38) for supplying the dummy data output from the generator (36) to the data / video transmission system
Provided with a door,
The dummy data insertion device, wherein the dummy data is carried in a frame having any one of an unused multicast address, an unused VLAN-ID, and an unused LLID as a header . 12. The dummy data insertion device according to claim 11 , wherein the header of the dummy data is changed at a predetermined cycle. The dummy data insertion apparatus according to claim 11 or 12 , wherein the dummy data includes a random pattern or a pseudo-random pattern arranged in a payload having a predetermined frame structure. The dummy data dummy data insertion device according to any one of claims 11 to 13 frame length of the frame is a random that carry.

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