JP2007201842A - Pon system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PON system by which a reference clock signal for synchronization on the station side is transmitted to the side of subscriber's houses without performing special communication between an optical line terminal of the station side and individual optical line terminal of the subscriber side. <P>SOLUTION: The PON system has the optical line terminal (OLT9) of the station side, a point and crossing 8 and the optical line terminal of the subscriber side (ONU10). The OLT9 has a clock reception and distribution part 15 which receives the reference clock signal for synchronization generated by a reference clock source 7 on the station side, generates a clock signal with predetermined frequency synchronized with the reference clock signal for synchronization and distributes the clock signal and a PON interface part 16 which generates a transmission signal synchronized with the clock signal distributed from the clock reception and distribution part 15. The ONU 10 has a clock reproduction part 17 which reproduces the clock signal from the transmission signal from the OLT9 and a clock conversion part 18 which converts the clock signal into the predetermined frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a PON system, and more particularly to a PON system that can be synchronized between a station-side terminal device and a subscriber-side terminal device.

  As an optical fiber network system in which a general home or the like is a subscriber, for example, a system in which a station-side terminal device provided in an aggregation station and a subscriber-side terminal device installed in a subscriber's house are connected by an optical fiber is conceivable. .

  In particular, in a synchronous subscriber system that synchronizes between a station-side terminator and a subscriber-side terminator, a one-to-one dedicated line is installed between the station-side terminator and each subscriber-side terminator. A system is needed. However, since a one-to-one dedicated line is installed between the station-side terminal device and each subscriber-side terminal device, the installation cost is high.

  Specific examples of a system in which a one-to-one dedicated line is installed between a station-side terminal device and individual subscriber-side terminal devices include systems such as T1 and E1. Here, T1 is a standard for a digital dedicated line with a communication speed of 1.5 Mbps, and is also referred to as “DS1”. E1 is a standard that is prevalent in Europe, and is a standard for a digital dedicated line having a capacity of 2 Mbps in which 32 lines of 64 Kbps lines are bundled.

  In addition, as a system that does not have a one-to-one dedicated line, one optical fiber that inputs / outputs data from the station-side terminator is branched into a plurality of optical couplers that are passive elements. There is a PON (Passive Optical Network) system that connects subscriber-side terminal devices. In this PON system, high-speed data transmission / reception can be performed to a plurality of subscriber homes without providing a special relay device in the middle of the transmission path. Among them, there is a GE-PON (Gigabit Ethernet (registered trademark) -Passive Optical Network) system using Ethernet (registered trademark) technology. Note that the GE-PON system is defined by IEEE 802.3ah.

  However, in the GE-PON system, it is assumed that the Ethernet (registered trademark) technology does not synchronize between the station-side terminal device and each subscriber-side terminal device. It operates using a running clock signal (a clock signal that is not synchronized with others), and the subscriber-side terminating device also operates with an independent clock signal. Therefore, in the GE-PON system, a synchronous subscriber system cannot be constructed.

  Therefore, as one method of accommodating the synchronous subscriber system in the GE-PON system, a large-capacity buffer memory is installed in each of the synchronous signal-Ethernet (registered trademark) conversion devices on the station side and the subscriber side, There has been a method of absorbing the clock difference between the reference clock signal for synchronization and the operation clock signal in the synchronous signal-Ethernet (registered trademark) conversion device in the buffer memory.

  However, in the case of this method, since a delay occurs in the buffer memory, there is a problem in that echo is generated due to the delay when audio is accommodated by a synchronous signal.

  In order to solve the delay problem, it is necessary to minimize the capacity of the buffer memory. For this purpose, it is necessary to synchronize between the station-side terminator and each subscriber-side terminator in some way. was there.

  Therefore, in the system disclosed in Patent Document 1, a counter for generating a clock is installed in both the station-side termination device and the subscriber-side termination device, and the counter value is periodically transmitted from the station-side termination device. The counter of the subscriber-side terminal device is synchronized with the counter of the station-side terminal device.

JP 2002-051078 A

  However, in the system shown in Patent Document 1, it is necessary to communicate a counter value for synchronization, so that a band for data transmission / reception is consumed. Furthermore, in the system shown in Patent Document 1, it is necessary to newly negotiate a communication procedure in order to perform synchronization between the station-side terminal device and each subscriber-side terminal device, and it is necessary to change the standard itself. It was.

  Therefore, in order to solve the above-mentioned problems, the present invention provides a synchronization reference clock signal on the station side to the subscriber's home without performing special communication between the station side termination device and each subscriber side termination device. An object of the present invention is to provide a PON system capable of transmitting to the side.

  The solution according to the present invention is connected to each of a station-side termination device that transmits and receives a predetermined signal, a branching device that branches a wiring from the station-side termination device, and a wiring that is branched by the branching device. A PON system comprising a side terminator and a plurality of subscriber side terminators for transmitting and receiving a predetermined signal, wherein the station side terminator receives a synchronization reference clock signal generated by a reference clock source on the station side A clock reception / distribution unit that generates and distributes a clock signal that is synchronized with the reference clock signal for synchronization, and an interface unit that generates a transmission signal that is synchronized with the clock signal distributed from the clock reception / distribution unit. The termination device includes a clock recovery unit that recovers a clock signal from a transmission signal from the station-side termination device, and a clock conversion unit that converts the clock signal to a predetermined frequency.

  In the PON system according to the present invention, the station-side termination device includes a clock reception distribution unit and an interface unit, and the subscriber-side termination device includes a clock recovery unit and a clock conversion unit. Since the synchronization-side reference clock signal can be obtained in the subscriber-side terminating device and can be operated in synchronization with the synchronization-purpose reference clock signal, the synchronous subscriber system can be accommodated in the PON system.

  As a premise of the PON system according to the present invention, a conventional synchronous subscriber system will be described with reference to FIG. In the synchronous subscriber system shown in FIG. 3, a one-to-one dedicated line (optical fiber or electric wire) is installed between the station side 1 and the subscriber house 2, and each of the two subscriber houses 2 is installed. In contrast, wiring is provided independently. In the synchronous subscriber system shown in FIG. 3, a synchronous station-side terminal device 3 is installed at the station side 1, and a synchronous subscriber-side terminal device 4 is installed at the subscriber house 2.

  Further, in the synchronous subscriber system shown in FIG. 3, a synchronous host system 5 connected to the station-side terminal device 3 on the station side 1, and a synchronous system connected to the subscriber-side terminal device 4 on the subscriber house 2. The user devices 6 are provided. Therefore, the station-side terminal device 3 and the host device 5 operate in synchronization with the synchronization reference clock signal generated by the synchronization reference clock source 7. On the other hand, the user device 6 reproduces the synchronization reference clock signal from the signal received in the subscriber-side termination device 4, and realizes synchronization based on the synchronization reference clock signal.

  Next, as a premise of the PON system according to the present invention, a conventional GE-PON system will be described with reference to FIG. In the GE-PON system shown in FIG. 4, a one-to-many connection is made between the station side 1 and the subscriber premises 2 using an optical fiber and using an optical branching unit 8 which is a passive element in the middle. is doing. FIG. 4 shows an example in which two subscriber houses 2 are connected to one station side 1. In the GE-PON system shown in FIG. 4, the station-side terminal device on the station side 1 is called an OLT (Optical Line Terminal) 9, and the subscriber-side terminal device in the subscriber house 2 is called an ONU (Optical Network Unit) 10. Call.

  In the GE-PON system shown in FIG. 4, communication is performed between the Ethernet (registered trademark) user device 11 connected to the ONU 10 and the Ethernet (registered trademark) host device 12 connected to the OLT 9. Is possible. However, since the Ethernet (registered trademark) technology is based on the premise that no synchronization is performed between the user apparatus 11 and the host apparatus 12, a clock source is provided in each of the OLT 9 and the ONU 10 illustrated in FIG. Therefore, the conventional GE-PON system cannot accommodate the synchronous subscriber system.

  Next, the PON system according to the present invention will be described.

(Embodiment 1)
The PON system according to the present embodiment will be described with reference to FIG. 1 especially on the premise of the GE-PON system. The station side 1 of the PON system shown in FIG. 1 includes an OLT 9 (station side terminal device) and a synchronization system signal-Ethernet (registered trademark) conversion device 14 that are synchronized with the synchronization reference clock signal of the synchronization reference clock source 7, and synchronization. A host device 5 of the system is provided. The OLT 9 is provided with a clock reception distribution unit 15 that receives a synchronization reference clock signal and generates an internal clock signal of the OLT 9 in synchronization with the synchronization reference clock signal. Further, the clock reception distribution unit 15 distributes the generated internal clock signal to other parts in the OLT 9.

  The OLT 9 includes a PON interface unit 16 that operates in synchronization with the internal clock signal from the clock reception distribution unit 15 and transmits / receives a main signal (user data) to / from the subscriber home 2 side. Since the host device 5 employs communication using a synchronous signal, the main signal from the host device 5 is converted into a signal suitable for the PON interface unit 16 in the synchronous signal-Ethernet (registered trademark) converter 14. There is a need to. The host device 5 is a subscriber line termination device or the like used by a telecommunications carrier to aggregate signal lines from subscribers, and the synchronous signal-Ethernet (registered trademark) converter 14 is a synchronous interface. Is a device that bridges between the higher-level device 5 having an OLT 9 and the OLT 9 having an Ethernet (registered trademark) interface. However, since the host device 5 and the synchronous signal-Ethernet (registered trademark) converter 14 are not directly related to the configuration of the present invention, detailed description thereof is omitted.

  On the subscriber premises 2 side of the PON system shown in FIG. 1, an ONU 10 (subscriber-side termination device) connected to the OLT 9, a synchronous signal-Ethernet (registered trademark) converter 13 connected to the ONU 10, and a synchronous system A synchronous user device 6 connected to the signal-Ethernet (registered trademark) conversion device 13 is provided. In the PON system, the wiring from the OLT 9 is branched into a plurality by the optical branching unit 8, and the ONU 10 is connected to each wiring. However, in FIG. 1, only the ONU 10 of one subscriber house 2 is illustrated, and the illustration of the other subscriber houses 2 is omitted.

  Further, the ONU 10 includes a clock recovery unit 17 that recovers a clock signal from the main signal received from the OLT 9, and converts the extracted clock signal into a clock signal having a frequency suitable for the synchronous signal-Ethernet (registered trademark) converter 13. And a clock converter 18 for conversion. The main signal received by the ONU 10 is input to the synchronous system signal-Ethernet (registered trademark) conversion device 13 together with the extracted clock signal, and after being appropriately converted, is input to the user device 6 as the synchronous system signal.

  Next, in the PON system according to the present embodiment, a method for transmitting the synchronization reference clock signal on the station side 1 to the subscriber home 2 side will be described. First, the clock reception distributor 15 of the OLT 9 receives the synchronization reference clock signal input from the synchronization reference clock source 7. The clock reception / distribution unit 15 generates a synchronization clock signal having a frequency necessary for the PON interface unit 16 and synchronized with the synchronization reference clock signal by a built-in PLL (Phase Locked Loop) or the like. Furthermore, the clock reception distribution unit 15 distributes the generated synchronous clock signal to the PON interface unit 16 and the like in the OLT 9.

  The PON interface unit 16 synchronizes with the synchronous clock signal distributed from the clock reception distribution unit 15 when generating the main signal to be transmitted to the ONU 10. The PON interface unit 16 also transmits the main signal to the ONU 10 in synchronization with the synchronous clock signal.

  On the other hand, when the ONU 10 receives the main signal from the OLT 9, the clock recovery unit 17 extracts and reproduces the synchronous clock signal from the main signal. Note that the signal transmitted from the OLT 9 to the ONU 10 in the GE-PON system is based on the standard (IEEE 802.3ah) and is an encoding method that easily reproduces the clock signal. Further, a general ONU 10 often includes a clock recovery unit 17 for reception. Therefore, in the GE-PON system, the synchronous clock signal can be easily reproduced without adding a new circuit to the ONU 10.

  Next, in the ONU 10, the recovered synchronous clock signal is converted into a frequency (for example, 8 kHz) used in the synchronous signal by the clock converter 18 and supplied to the synchronous signal-Ethernet (registered trademark) converter 13. The synchronous signal-Ethernet (registered trademark) conversion device 13 operates in synchronization with the synchronous clock signal supplied from the ONU 10, so that the interface to the user device 6 is eventually used for the synchronization of the reference clock source 7 for synchronization. It can be operated in synchronization with the reference clock signal. The user device 6 is a device having a synchronous interface, and the synchronous signal-Ethernet (registered trademark) conversion device 13 is a user device 6 having a synchronous interface and an Ethernet (registered trademark) interface. It is a device that bridges between the ONU 10 having. However, since the configurations of the user device 6 and the synchronous signal-Ethernet (registered trademark) conversion device 13 are not directly related to the configuration of the present invention, detailed description thereof is omitted.

  As described above, in the PON system according to the present embodiment, the OLT 9 receives the synchronization reference clock signal generated by the reference clock source 7 on the station side 1 and is synchronized with the synchronization reference clock signal. And a PON interface unit 16 that generates a main signal to be transmitted in synchronization with the synchronous clock signal distributed from the clock reception distribution unit 15. The ONU 10 receives the main signal from the OLT 9. A clock recovery unit 17 that recovers a synchronous clock signal from the signal, and a clock conversion unit 18 that converts the synchronous clock signal to a predetermined frequency are provided. Therefore, the PON system according to the present embodiment can reproduce the synchronization clock synchronized with the synchronization reference clock signal of the synchronization reference clock source 7 in the ONU 10, and further synchronize the ONU 10 and the like with the synchronization reference clock signal. Therefore, it is possible to accommodate a synchronous subscriber system.

(Embodiment 2)
The PON system according to the present embodiment will be described with reference to FIG. 2 on the premise of the GE-PON system. The station side 1 of the PON system shown in FIG. 2 includes an OLT 9 (station side terminal device) synchronized with a synchronization reference clock signal of a synchronization reference clock source 7, a synchronization signal-Ethernet (registered trademark) conversion device 14, and a synchronization. A host device 5 of the system is provided. The OLT 9 receives the main signal (user data) from the electro-optical converter 19 that converts the synchronization reference clock signal into an optical signal and the synchronization signal-Ethernet (registered trademark) converter 14 between the ONU 10 and the OLT 9. And a PON interface unit 16 for transmitting and receiving data.

  Further, the OLT 9 combines a WDM (Wavelength Division) for combining (wavelength multiplexing) the optical signal of the main signal from the PON interface unit 16 and the optical signal of the synchronization reference clock signal from the electro-optical conversion unit 19. Multiplexer) coupler 20 is provided. The synchronous signal-Ethernet (registered trademark) conversion device 14 and the host device 5 are not directly related to the configuration of the present invention, and thus detailed description thereof is omitted.

  On the subscriber premises 2 side of the PON system shown in FIG. 2, an ONU 10 (subscriber-side termination device) connected to the OLT 9, a synchronous signal-Ethernet (registered trademark) conversion device 13 connected to the ONU 10, a synchronous system A synchronous user device 6 connected to the signal-Ethernet (registered trademark) conversion device 13 is provided. In the PON system, the wiring from the OLT 9 is branched into a plurality by the optical branching unit 8, and the ONU 10 is connected to each wiring. However, in FIG. 2, only the ONU 10 of one subscriber house 2 is illustrated, and the illustration of the other subscriber houses 2 is omitted.

  Further, on each subscriber home 2 side, a demultiplexing WDM coupler 21 for separating the optical signal from the PON interface unit 16 and the optical signal from the electro-optical conversion unit 19 is provided in the front stage of the ONU 10. . Further, on each subscriber home 2 side, an optical-electric conversion unit 22 that converts an optical signal from the electric-optical conversion unit 19 separated by the demultiplexing WDM coupler 21 into an electric signal, and an electric-optical conversion And a clock conversion unit 18 that converts the synchronization reference clock signal converted into an electric signal by the unit 19 into a frequency suitable for the subsequent synchronization system signal-Ethernet (registered trademark) conversion device 13.

  Next, in the PON system according to the present embodiment, a method for transmitting the synchronization reference clock signal on the station side 1 to the subscriber home 2 side will be described. First, the wavelength of the main signal (user data) output from the PON interface unit 16 is λ1. Further, the wavelength of the optical signal obtained by converting the synchronization reference clock signal by the electro-optical converter 19 is set to λ2.

  Then, in the multiplexing WDM coupler 20, the optical signal (λ1) from the PON interface unit 16 and the optical signal (λ2) from the electro-optical conversion unit 19 are combined to produce one combined wave (λ1 + λ2). Multiplex on optical fiber.

  On the other hand, on the subscriber's home 2 side, the combined wave (λ1 + λ2) received by the demultiplexing WDM coupler 21 is converted into an optical signal (λ1) from the PON interface unit 16 and an optical signal (λ1) from the electro-optical conversion unit 19 ( and λ2). The separated optical signal (λ1) is input to the ONU 10 and processed as a main signal. The processed main signal is input to the synchronous signal-Ethernet (registered trademark) converter 13.

  Further, the separated optical signal (λ2) is converted into an electrical signal by the optical-electrical converter 22, and a synchronization reference clock signal is taken out. The synchronization reference clock signal extracted by the opto-electric conversion unit 22 is input to the clock conversion unit 18 and converted into a frequency (for example, 8 kHz) used for the synchronization system signal by the clock conversion unit 18. The clock converter 18 supplies the reference clock signal for synchronization after frequency conversion to the synchronous signal-Ethernet (registered trademark) converter 13. The ONU 10 and the demultiplexing WDM coupler 21, the optical-electric conversion unit 22, and the clock conversion unit 18 described above may be considered as subscriber terminators in a broad sense.

  The synchronous signal-Ethernet (registered trademark) converter 13 operates in synchronization with the reference clock signal for synchronization supplied from the clock converter 18, thereby synchronizing the interface to the synchronous user device 6 as a result. The reference clock source 7 can be operated in synchronism with the synchronization reference clock signal. Note that the configurations of the synchronous signal-Ethernet (registered trademark) conversion device 13 and the user device 6 are not directly related to the configuration of the present invention, and thus detailed description thereof is omitted.

  As described above, in the PON system according to the present embodiment, the OLT 9 receives the synchronization reference clock signal generated by the reference clock source 7 on the station side 1 and uses the synchronization reference clock signal as the optical signal (λ2). An electro-optical conversion unit 19 that converts the main signal into an optical signal (λ1), a PON interface unit 16 that performs transmission and reception, an optical signal (λ1) from the PON interface unit 16, and an electro-optical conversion unit And a multiplexing WDM coupler 20 that combines the optical signal (λ2) from 19 to generate a combined wave (λ1 + λ2). Further, in the PON system according to the present embodiment, the optical signal (λ1) from the PON interface unit 16 and the optical signal (λ2) from the electro-optical conversion unit 19 from the combined wave (λ1 + λ2) are placed in front of each ONU 10. ), A photoelectric conversion unit 22 for converting the separated optical signal (λ2) into a synchronization reference clock signal, and a synchronization reference converted by the photoelectric conversion unit 22. A clock converter 18 for converting the clock signal to a predetermined frequency is further provided.

  Therefore, the PON system according to the present embodiment can reproduce the synchronization clock synchronized with the synchronization reference clock signal of the synchronization reference clock source 7 in the ONU 10, and further synchronize the ONU 10 and the like with the synchronization reference clock signal. Therefore, it is possible to accommodate a synchronous subscriber system.

  In the first embodiment and the second embodiment described above, the GE-PON system has been described. However, the present invention is not limited to this, and a signal is transmitted between the station-side terminal device and the subscriber-side terminal device. The same applies to other PON systems that are not synchronized.

1 is a block diagram of a PON system according to Embodiment 1 of the present invention. It is a block diagram of the PON system which concerns on Embodiment 2 of this invention. 1 is a block diagram of a network system as a premise of the present invention. 1 is a block diagram of a PON system as a premise of the present invention.

Explanation of symbols

1 station side, 2 subscriber premises, 3 station side termination device, 4 subscriber side termination device, 5,12 host device, 6,11 user device, 7 synchronization reference clock source, 8 optical branching unit, 9 OLT, 10 ONU, 13, 14 Synchronous signal-Ethernet (registered trademark) conversion device, 15 clock reception distribution unit, 16 PON interface unit, 17 clock recovery unit, 18 clock conversion unit, 19 electro-optical conversion unit, 20 WDM for multiplexing Coupler, WDM coupler for demultiplexing, 22 optical-electrical converter.

Claims (2)

A station-side terminator for transmitting and receiving a predetermined signal;
A branching device for branching the wiring from the station side termination device into a plurality;
A PON system connected to each of the wirings branched by the branching device, the PON system including the station-side terminal device and a plurality of subscriber-side terminal devices that transmit and receive the predetermined signal;
The station-side termination device receives a synchronization reference clock signal generated by a station-side reference clock source, generates a clock signal synchronized with the synchronization reference clock signal, and distributes the clock reception distribution unit,
An interface unit that generates a transmission signal synchronized with the clock signal distributed from the clock reception distribution unit,
The subscriber-side terminal device includes a clock recovery unit that recovers the clock signal from the transmission signal from the station-side terminal device;
A PON system comprising: a clock conversion unit that converts the clock signal into a predetermined frequency. A station-side terminator for transmitting and receiving a predetermined signal;
A branching device for branching the wiring from the station side termination device into a plurality;
A PON system connected to each of the wirings branched by the branching device, the PON system including the station-side terminal device and a plurality of subscriber-side terminal devices that transmit and receive the predetermined signal;
The station-side termination device receives a synchronization reference clock signal generated by a station-side reference clock source, and converts the synchronization reference clock signal into a first optical signal;
An interface unit for converting the predetermined signal into a second optical signal to transmit and receive;
A combining coupler that combines the second optical signal from the interface unit and the first optical signal from the electro-optical conversion unit to generate a combined wave;
A demultiplexing coupler that separates the second optical signal from the interface unit from the combined wave and the first optical signal from the electro-optical conversion unit from the combined wave in a stage preceding each of the subscriber-side termination devices. An optical-electric conversion unit that converts the first optical signal separated by the demultiplexing coupler into the synchronization reference clock signal, and the synchronization reference clock signal converted by the optical-electric conversion unit, A PON system, further comprising a clock conversion unit for converting to a predetermined frequency.

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