JP4816787B2 - Station side communication device, subscriber side communication device, communication system, and communication method - Google Patents

Description

  The present invention relates to a point-multipoint communication system in which a station side communication device and a plurality of subscriber side communication devices are connected by an optical fiber via a star coupler.

As a conventional access network for transmitting a multimedia service to each home, an EPON (Ethernet (registered trademark) Passive Optical Network) system is known (see, for example, Non-Patent Document 1). In this EPON system, a plurality of subscriber side communication devices (ONU: Optical Network Unit) and a station side communication device (OLT: Optical Line Terminal) are connected by an optical fiber cable via a star coupler. It is economical because ONUs share a single OLT.
In this EPON system, for example, the idle pattern transmitted when there is no downstream data from the OLT to the ONU is a fixed pattern, and therefore the same pattern is repeated in the physical layer.

IEEE (Institute of Electrical and Electronics Engineers) 802.3ah

  In the conventional communication method disclosed in Patent Document 1, for example, since the idle pattern is a fixed pattern, the same pattern is repeated, and a specific spectrum appears strongly in the optical signal as the physical layer. For this reason, for example, when wavelength division multiplexing of a video signal is performed on a data communication signal in the downlink direction, if the optical demultiplexer mounted in the ONU cannot sufficiently separate this specific spectrum, the data communication signal is converted into the video signal. There was a problem of affecting.

  The present invention has been made to solve the above-described problems, and in a communication method, for example, when a PON system such as an EPON system transmits an idle pattern, a specific spectrum due to a periodic fixed pattern is generated in an optical signal. The purpose is to suppress.

A station-side communication apparatus according to the present invention is a station that wavelength-division-multiplexes different types of first and second optical signals and transmits them to a plurality of subscriber-side communication apparatuses connected via an optical coupler. A transmission signal output unit that outputs a first transmission signal and a first transmission signal output by the transmission signal output unit, the number of appearances of the same code in the encoded code string A scramble encoding unit that performs encoding by a predetermined encoding method, a scramble encoding unit that scrambles the first transmission signal encoded by the encoding unit, and a scramble encoding unit by the scramble encoding unit A first optical conversion unit that converts the first transmission signal thus converted into a first optical signal, and a second transmission signal that is converted into a second optical signal having a wavelength different from that of the first optical signal. A second light conversion unit and the first light conversion; An optical multiplexing unit that wavelength-division-multiplexes the first optical signal converted by the second optical signal and the second optical signal converted by the second optical conversion unit, and transmits them to the plurality of subscriber side communication devices; Is provided.

  In the communication method, for example, when an idle pattern is transmitted in a PON system, a fixed pattern is converted into a random pattern by scramble coding, so that a specific spectrum due to a periodic fixed pattern is prevented from occurring in an optical signal. be able to.

Embodiment 1 FIG.
The communication method according to Embodiment 1 of the present invention is a periodic transmission that is wavelength-division-multiplexed and transmitted from a station side communication device (OLT: Optical Line Terminal) to a plurality of subscriber side communication devices (ONU: Optical Network Unit). Since the generation of a specific spectrum can be suppressed by scrambling the data including the fixed pattern, the wavelength division multiplexing technology is applied to the GE-PON (Gigabit Ethernet (registered trademark) -Passive Optical Network) system. In this case, the specifications of the optical demultiplexer mounted on the ONU can be relaxed.

  1 is a block diagram showing a network system in a communication method according to Embodiment 1 of the present invention. In the figure, 1 is a data communication PON control unit (OLT), 2 is a scramble coding unit that performs scramble coding on input 10-bit parallel data, 3 is a parallel-serial conversion unit, 4 is a wavelength λ1 (for example, This is an optical transmitter that generates an optical signal of 1490 nm band). Reference numeral 5 denotes a video signal PON control unit (OLT), and 6 denotes an optical transmitter that generates an optical signal having a wavelength λ2 (for example, 1550 nm band). Reference numeral 7 denotes an optical multiplexer that wavelength-multiplexes the optical signal for video and the optical signal for data. An optical demultiplexer 8 wavelength-separates the optical signal for video and the optical signal for data. 9 is an optical receiver for an optical signal having a wavelength λ1, and 13 is an optical receiver for an optical signal having a wavelength λ2. Reference numeral 10 denotes a scramble decoding unit that performs scramble decoding, 11 a serial-parallel conversion unit, 12 a data communication PON control unit (ONU), and 14 a video signal PON control unit (ONU).

Next, the operation will be described.
Downstream data is output from the data communication PON control unit (OLT) 1 as 10-bit parallel data of an 8B / 10B 10B signal of Ethernet (registered trademark). The 10-bit parallel data is scrambled by the scramble encoder 2 for all downstream signals. The scramble-encoded 10-bit parallel data is subjected to parallel-serial conversion by the parallel-serial conversion unit 3, subjected to electro-optical conversion by the optical transmitter 4 and transmitted to the ONU as an optical signal having a wavelength λ 1.

  Here, since the data for data communication is converted into a random pattern by being scrambled, generation of a specific spectrum can be suppressed. Note that scrambling means “mixing”, and the original signal sequence is converted into a different signal sequence according to a certain conversion rule, and the mark is set regardless of the mark rate of the original signal sequence (probability of occurrence of “1” of the digital code). A random signal sequence with a rate of approximately ½ is used. As shown in FIG. 2, the data for data communication is scrambled by taking an exclusive OR of a pattern generated by the scramble pattern generator (for example, a pattern called a maximum periodic sequence code) and the original signal sequence. Is done.

On the other hand, the downstream video signal is also output from the video signal PON control unit (OLT) 5 as a modulation signal, subjected to electro-optical conversion by the optical transmitter 6, and transmitted to the ONU as an optical signal of wavelength λ2.
These optical signals are wavelength-multiplexed by the optical multiplexer 7 and transmitted through a one-core optical fiber via an optical coupler (not shown). The transmitted optical signal is wavelength-separated by the optical demultiplexer 8 in the ONU and separated into an optical signal for data communication and an optical signal for video, and then the optical receiver 9 and the optical receiver 13 respectively. Photo-electrical conversion.

  The video signal PON control unit 14 processes the video signal. The data communication signal output from the optical receiver 9 is returned to the 8B / 10B 10B signal by the scramble decoding unit 10.

Next, the operation of scramble decoding (cancellation) will be described with reference to FIG.
The signal for data communication output from the optical receiver 9 searches the input pattern by the pattern search unit 17, notifies the matched pattern to the scramble release unit 18 by the pattern search unit 17, and cancels it by the scramble release unit 18. 10B serial data of an 8B / 10B signal is obtained by preparing a pattern necessary for the above and releasing the scramble of the input data.
The scrambled decoded signal undergoes serial-parallel conversion by the serial-parallel conversion unit 3 and is processed by the data communication PON control unit 12.

As described above, in the communication method according to Embodiment 1 of the present invention, a specific spectrum is obtained by scrambling and encoding data including a periodic fixed pattern transmitted by wavelength division multiplexing from the OLT to the ONU. Since the generation can be suppressed, the specification (optical characteristic specification) of the optical demultiplexer mounted on the ONU can be relaxed when the wavelength multiplexing technique is applied to the GE-PON system.
Note that a configuration in which an optical filter for extracting each wavelength of wavelength multiplexed light is mounted after the optical demultiplexer of the ONU is also conceivable. In this case, the effect of relaxing the specifications of the optical filter is expected by the present invention. The

  Further, in the first embodiment, since all the downlink main signals for data communication are scrambled, it is possible to easily perform scramble coding on the OLT side. Since the ONU receiving side performs serial processing, a circuit with a high processing speed is required.

Embodiment 2. FIG.
In the first embodiment described above, the scramble decoding in the ONU is performed with serial data. Next, the second embodiment in which the scramble decoding is performed with parallel data will be described.
4 is a block diagram showing a network system in a communication method according to Embodiment 2 of the present invention. The system configuration is almost the same as that of the first embodiment, but the configurations of the scramble encoding unit 2a and the scramble decoding unit 10a are different as shown in FIGS.

Next, the operation will be described.
First, the operation of the scramble coding unit 2a will be described with reference to FIG. With respect to the 10-bit parallel signal output from the data communication PON control unit (OLT) 1, the fixed pattern search unit 19 searches for the K28.5 pattern (00111111010) which is an Ethernet (registered trademark) idle signal. The scramble control unit 20 executes scramble coding on the downlink signal. However, the K28.5 pattern is passed through the idle signal portion of the downstream signal as it is without periodically performing scramble coding. This is because the K28.5 pattern is necessary for the ONU side serial-parallel converter 11 described later to synchronize. The scramble-coded downstream signal is subjected to parallel-serial conversion by the parallel-serial conversion unit 3, and then subjected to electro-optical conversion by the optical transmitter 4 and transmitted to the ONU.

  On the other hand, the video signal is output as a modulation signal from the video signal PON control unit (OLT) 5 and is electro-optically converted by the optical transmitter 6 as an optical signal having a wavelength λ2, as in the first embodiment. Transmitted to the ONU.

  These optical signals are wavelength-multiplexed by the optical multiplexer 3 and transmitted through a one-core optical fiber via an optical coupler (not shown). The transmitted optical signal is wavelength-separated by the optical demultiplexer 7 in the ONU and separated into the optical signal for data and the optical signal for video, and then the optical signal is received by the optical receiver 9 and the optical receiver 13, respectively. -Electrical conversion.

  The video signal is processed by a video signal PON control unit (OLT) 14. The data communication signal output from the optical receiver 9 is converted into a 10B signal of 8B / 10B signal by the scramble decoding unit 10a.

  Next, the scramble decoding (cancellation) operation will be described with reference to FIG. The signal received by the optical receiver 9 is subjected to serial-parallel conversion by the serial-parallel converter 11. Since the K28.5 pattern is periodically inserted as an idle pattern in the downstream signal, a commercially available device can be used. The K28.5 pattern is searched for the parallel-converted signal by the fixed pattern search unit 17a. If they match, a descrambling invalid signal is transmitted to the subsequent descrambling unit 18a. The signal can also be used as a signal for resetting the scramble pattern. The descrambled signal is processed by the data communication PON control unit (ONU) 12.

  As described above, the second embodiment has an advantage that a circuit having a high processing speed is not necessary because scramble decoding is performed using a parallel signal.

Embodiment 3 FIG.
In the second embodiment described above, it is possible to perform scramble decoding of a parallel signal with a low-speed circuit. Further, scramble coding is performed using a periodic control message transmitted from the OLT to the ONU. And Embodiment 3 in which the timing for performing scramble decoding is controlled.

Although the basic configuration is the same as that of the second embodiment, the operations of the scramble coding unit 2a and the scramble decoding unit 10a shown in FIGS. 5 and 6 are different, and these are the scramble coding control unit and the scramble decoding control. Operation as a part.
First, the scramble encoding operation will be described with reference to FIG. In the GE-PON system, there is data periodically transmitted from the OLT to the ONU. A certain portion of the data always has a predetermined value, and when the value (predetermined fixed pattern) is scrambled, an idle pattern (K28.5 pattern) is obtained. Then, the fixed pattern search unit 19 searches for a predetermined fixed pattern, and if it matches, sends a search result match signal to the scramble control unit 20. The scramble control unit 20 resets the scramble pattern when receiving the search result coincidence signal. The scrambled signal is parallel-serial converted by the parallel-serial converter 3 and transmitted to the ONU.

  Next, the scramble decoding (cancellation) operation will be described with reference to FIG. The signal output from the optical receiver 9 is serial-parallel converted by the serial-parallel converter 11. The K28.5 pattern is searched by the fixed pattern search unit 17a, and a control signal for resetting the scramble pattern is transmitted to the subsequent descrambling unit 18a at the timing when the matching pattern is found. The scramble release unit 18a releases the scramble for the input signal, and resets the scramble pattern when the control signal is input from the fixed pattern search unit 17a.

  As described above, in the third embodiment, the scramble timing can be controlled using the periodic message pattern used in the GE-PON system. Also, it can be realized with a relatively small circuit scale.

  As described above, in the first to third embodiments of the present invention, the case of the Ethernet (registered trademark) frame is shown, but the frame format is not limited to this, and a periodic fixed pattern is a problem. The present invention can be applied as long as

Configuration diagram showing a network system in a communication method according to Embodiment 1 of the present invention The block diagram which shows the scramble encoding part in the communication method by Embodiment 1 of this invention The block diagram which shows the scramble decoding part in the communication method by Embodiment 1 of this invention The block diagram which shows the network system in the communication method by Embodiment 2 of this invention The block diagram which shows the scramble encoding part in the communication method by Embodiment 2 of this invention The block diagram which shows the scramble decoding part in the communication method by Embodiment 2 of this invention

1 PON control unit for data communication (OLT)
2 Scramble coding unit 4, 6 Optical transmitter 5 Video signal PON control unit (OLT)
7 Optical multiplexer 8 Optical demultiplexer 9, 13 Optical receiver 10 Scramble decoding unit 12 Data communication PON control unit (ONU)
14 Video signal PON control unit (ONU)

Claims (8)

A station-side communication device that wavelength-division-multiplexes a first optical signal and a second optical signal of different types and transmits them to a plurality of subscriber-side communication devices connected via an optical coupler,
A transmission signal output unit for outputting a first transmission signal;
An encoding unit that encodes the first transmission signal output by the transmission signal output unit using an encoding method in which the number of appearances of the same code is defined in advance in the encoded code string;
A scramble encoder that scrambles the first transmission signal encoded by the encoder;
A first optical conversion unit that converts the first transmission signal scrambled by the scramble encoding unit into a first optical signal;
A second optical conversion unit that converts the second transmission signal into a second optical signal having a wavelength different from that of the first optical signal;
The first optical signal converted by the first optical conversion unit and the second optical signal converted by the second optical conversion unit are wavelength-division multiplexed to the plurality of subscriber-side communication devices. An optical multiplexer to transmit;
A station-side communication device comprising: The station-side communication device according to claim 1, wherein the transmission signal output unit outputs the first transmission signal including a periodic fixed pattern. The station-side communication apparatus according to claim 1, wherein the encoding scheme is an encoding scheme that performs encoding by converting the number of bits. The station side communication apparatus according to any one of claims 1 to 3, wherein the encoding method is 8B / 10B conversion. A communication system that wavelength-division-multiplexes a first optical signal and a second optical signal of different types and transmits them from a station-side communication device to a plurality of subscriber-side communication devices connected via an optical coupler,
The station side communication device is:
A transmission signal output unit for outputting a first transmission signal;
An encoding unit that encodes the first transmission signal output by the transmission signal output unit using an encoding method in which the number of appearances of the same code is defined in advance in the encoded code string;
A scramble encoder that scrambles the first transmission signal encoded by the encoder;
A first optical conversion unit that converts the first transmission signal scrambled by the scramble encoding unit into a first optical signal;
A second optical conversion unit that converts the second transmission signal into a second optical signal having a wavelength different from that of the first optical signal;
The first optical signal converted by the first optical conversion unit and the second optical signal converted by the second optical conversion unit are wavelength-division multiplexed to the plurality of subscriber-side communication devices. An optical multiplexer to transmit;
With
The subscriber side communication device is:
An optical demultiplexing unit that separates a signal received from the station-side communication device into a first optical signal and a second optical signal;
First and second electrical conversion units for electrically converting the first optical signal and the second optical signal separated by the optical demultiplexing unit into a first transmission signal and a second transmission signal, respectively;
A scramble decoding unit that scrambles and decodes the first transmission signal converted by the first electrical conversion unit;
A decoding unit for decoding the first transmission signal scrambled and decoded by the scramble decoding unit by a decoding method corresponding to the encoding method;
Having
A communication system characterized by the above. The second transmission signal is wavelength-division-multiplexed with the first transmission signal that is encoded by the encoding method in which the number of appearances of the same code in the encoded code string is defined in advance and scrambled. A subscriber-side communication device applicable to a communication system that transmits from a station-side communication device to a plurality of subscriber-side communication devices connected via an optical coupler,
An optical demultiplexing unit that separates a signal received from the station-side communication device into a first optical signal and a second optical signal;
First and second electrical converters for electrically converting the first optical signal and the second optical signal separated by the optical demultiplexing unit into a first transmission signal and a second transmission signal, respectively;
A scramble decoding unit that scrambles and decodes the first transmission signal converted by the first electrical conversion unit;
A decoding unit for decoding the first transmission signal scrambled and decoded by the scramble decoding unit by a decoding method corresponding to the encoding method;
A subscriber-side communication device comprising: Communication applicable to a communication system in which a first optical signal and a second optical signal of different types are wavelength division multiplexed and transmitted from a station side communication device to a plurality of subscriber side communication devices connected via an optical coupler. A method,
A transmission signal output step of outputting a first transmission signal;
An encoding step of encoding the first transmission signal output in the transmission signal output step by an encoding method in which the number of appearances of the same code in the encoded code string is defined in advance;
A scramble encoding step of scrambling encoding the first transmission signal encoded in the encoding step;
A first optical conversion step of converting the first transmission signal scrambled and encoded in the scramble encoding step into a first optical signal;
A second optical conversion step of converting a second transmission signal into a second optical signal having a wavelength different from that of the first optical signal;
An optical combination for wavelength division multiplexing the first optical signal converted in the first optical conversion step and the second optical signal in the second optical conversion step and transmitting the result to the plurality of subscriber side communication devices. Wave process,
An optical demultiplexing step of separating a signal received from the station side communication device into the first optical signal and the second optical signal;
An electrical conversion step of electrically converting the first optical signal separated in the optical demultiplexing step into a first transmission signal;
A scramble decoding step of scrambled decoding the first transmission signal converted in the electrical conversion step;
A decoding step of decoding the first transmission signal scrambled and decoded in the scramble decoding step by a decoding method corresponding to the encoding method;
A communication method comprising: In the scramble encoding step, when a control pattern included in the first transmission signal output in the transmission signal output step is detected, the scramble pattern used in the scramble encoding step is reset,
In the scramble decoding step, when a control pattern included in the first transmission signal electrically converted in the electrical conversion step is detected, resetting the scramble pattern used in the scramble decoding step;
The communication method according to claim 7.

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