JP4198569B2 - Passive optical network system, master station and slave station - Google Patents

Description

The present invention relates to a passive optical network system , a master station, and a slave station that enable communication of variable-length Ethernet (registered trademark) frame data.

  Conventionally, one master station OLT (Optical Line Termination) and a plurality of slave stations ONT (Optical Network Termination) are connected by an optical fiber via a star coupler, which is a multi-branch, There has been a passive optical network system (PON (Passive Optical Network) system) configured to perform transmission and reception at a slave station (see, for example, Patent Document 1).

  Such a PON system includes an optical transmission / reception circuit in each of the master station and the slave station. For example, in the optical transmission / reception circuit of the master station, the downstream signal is converted from an electric signal to an optical signal, and the slave station is connected via an optical fiber. Send to. Further, the optical signal received from each slave station via the optical fiber is converted into an electric signal. Similarly, in the optical transmission / reception circuit of the slave station, the optical signal received from the master station via the optical fiber is converted into an electrical signal, and the upstream signal is converted from the electrical signal to the optical signal and transmitted.

The communication procedure in such a PON system is as follows.
First, a slave station is registered by associating an individual slave station number with an arbitrary slave station. The master station designates the individual number of the registered slave station and transmits an ONT number assignment frame. The slave station that has received the ONT number assignment frame holds the assigned ONT number. Thereafter, the slave station receives only the frame of the assigned ONT number and discards the other frames.

  The slave station that has received the ONT number assignment frame transmits an ONT number assignment response frame to the parent station. When the master station receives the ONT number assignment response frame, the link between the master station and the slave station is established. Then, the master station transmits a transmission permission frame to the slave station in the link established state. The slave station that has received the transmission permission frame starts transmission of the uplink signal.

  When the slave station finishes transmitting the uplink signal with the data amount permitted to be transmitted, the slave station transmits a transmission end display frame to the master station, and terminates the transmission of the uplink signal. The master station that has received the transmission end display frame transmits a transmission permission frame to another slave station that has established a link. Thereafter, the same procedure is repeated to perform communication in the uplink transmission direction with a plurality of slave stations.

  There is no signal in the uplink transmission direction until one slave station finishes data transmission and another slave station starts data transmission. That is, the master station receives a signal from each slave station in a burst (intermittent) manner. In order to identify the received frame from the no-signal state, a preamble is added to the head of the frame transmitted by each slave station.

  For the downlink transmission direction, the downlink signal is transmitted to all the slave stations connected to the master station by broadcast, and each slave station receives only the frame displaying the ONT number assigned to itself, and discards the others. .

Japanese Patent Laid-Open No. 10-313334

  By the way, the optical transceiver used in the PON system using the burst signal as described above is an optical transceiver for continuous signals. Therefore, when applied to transmission / reception of such a burst signal, the transmitter requires a considerable time for stable operation of optical output. Similarly, a receiver also requires a considerable response time to reproduce an electrical signal from an optical signal. Therefore, there is a possibility that the head part of the signal is lost at the start of transmission, and there is a possibility that the master station cannot receive the frame correctly unless the length of the preamble added to the head of the frame is appropriate.

  For this reason, in the multiple slave stations connected to the master station, if the time required for stable operation of the optical transceivers used differs due to reasons such as multi-vendors, it is transmitted depending on the slave station. There was a problem that the received signal could not be received correctly by the master station.

The present invention has been made in order to solve the above-described problems, and the object of the present invention is to provide a continuous signal optical transmitter / receiver having different time required for stable operation of optical output even from a slave station. A passive optical network system , a master station, and a slave station that can correctly receive a signal transmitted to a master station are obtained.

In this invention, one master station and a plurality of slave stations are connected via a multi-branch unit, and each uses a continuous signal optical transceiver, and each slave station receives a transmission permission from the master station. In a passive optical network system that transmits signals in bursts, a slave station transmits a preamble length measurement frame insertion circuit that inserts a preamble length measurement frame into a transmission frame, and transmits a signal to the master station. A preamble length control circuit that sets a preamble based on information indicating a preamble length specific to the slave station that is measured and notified from the master station based on the preamble length measurement frame. It is a thing.

  In the present invention, since a preamble having a preamble length specific to the slave station is set in a frame transmitted from the slave station to the master station, continuous signal optical transceivers having different times required for stable operation of optical output are used. Even in this case, the signal transmitted from the slave station to the master station can be correctly received.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a passive optical network system according to the present invention.
In the illustrated system, one master station (OLT) 1 is connected to a plurality of slave stations (ONT) 2 via an optical fiber 4 via a star coupler 3. In this embodiment, the direction from the master station 1 to the slave station 2 is the downlink transmission direction, the direction from each slave station 2 to the master station 1 is the uplink transmission direction, a signal in the downlink transmission direction is a downlink signal, and uplink transmission. A direction signal is an upstream signal. Since each slave station 2 has the same configuration, only the internal configuration is shown.

  The master station 1 includes an optical transmission / reception circuit 10, an upstream frame identification circuit 11, a control frame termination circuit 12, an ONT state control circuit 13, a preamble length detection circuit 14, a preamble length storage unit 15, a downstream frame identification circuit 16, a frame buffer 17, And a control frame insertion circuit 18.

  The optical transceiver circuit 10 is an optical transceiver for continuous signals, and includes an electrical / optical signal converter (E / O) 10a, an optical / electrical signal converter (O / E) 10b, and a WDM coupler 10c. The optical transmission / reception circuit 10 is a functional unit that converts a downstream signal from an electrical signal to an optical signal by the electrical / optical signal converter 10 a and transmits the signal to the slave station 2 via the optical fiber 4. The upstream signal received from each slave station 2 through the optical fiber 4 is converted from an optical signal to an electrical signal by the electrical / optical signal converter 10 b and transmitted to the upstream frame identification circuit 11. The WDM coupler 10c is a coupler for wavelength-multiplexing the downstream signal.

  The upstream frame identification circuit 11 identifies an Ethernet (registered trademark) frame, a control frame, and a preamble length measurement frame. The Ethernet (registered trademark) frame is an upstream output signal 50, and the control frame is transmitted to the control frame termination circuit 12. The preamble length measurement frame has a function of transmitting to the preamble length detection circuit 14. The control frame is a frame including information for controlling signal transmission / reception.

  The control frame termination circuit 12 is a functional unit that identifies the content of the control frame received from the upstream frame identification circuit 11 and transmits it to the ONT state control circuit 13. The ONT state control circuit 13 manages the state of the slave station 2 based on the control information received from the control frame termination circuit 12, assigns the ONT number to the slave station 2, and the downlink transmission direction associated with the change in the state of the slave station 2 The control frame insertion circuit 18 is instructed to issue a control frame to the control frame insertion circuit 18.

  The preamble length detection circuit 14 has a function of measuring the optimum preamble length based on the preamble measurement frame received from the upstream frame identification circuit 11 and transmitting it to the preamble length storage unit 15. That is, when the preamble length detection circuit 14 receives a preamble length measurement frame having a length index from the head of the frame, the preamble length detection circuit 14 transmits the preamble length measurement frame with a length corresponding to the received position index. It has a function of detecting as the optimum preamble length of the slave station 2 (preamble length unique to the slave station 2). The preamble length storage unit 15 has a function of storing the optimum preamble length information received from the preamble length detection circuit 14 and transmitting the optimum preamble length information to the control frame insertion circuit 18 in response to a request from the control frame insertion circuit 18. ing.

  The downstream frame identification circuit 16 has a function of identifying an Ethernet (registered trademark) frame as the downstream input signal 51 and transmitting it to the frame buffer 17. The control frame insertion circuit 18 is a circuit that generates a control frame according to a command received from the ONT state control circuit 13 and inserts the control frame into a downstream signal.

  The control frame insertion circuit 18 includes a transmission permission frame insertion circuit 19, an ONT number assignment frame insertion circuit 20, and a preamble length measurement request frame insertion circuit 21. The transmission permission frame insertion circuit 19 has a function of generating a control frame that permits transmission of an upstream signal to an arbitrary slave station 2 and inserting the control frame into the downstream signal. The transmission permission frame includes information on the amount of data permitted to be transmitted to the slave station 2. The ONT number assignment frame insertion circuit 20 is a circuit for generating a control frame for assigning an arbitrary ONT number to an arbitrary slave station and inserting it into a downstream signal. The transmission of the ONT number assignment frame is performed when the slave station 2 is activated, and thereafter, the master station 1 is configured to monitor and control the slave station 2 based on the ONT number. The preamble length measurement request frame insertion circuit 21 generates a preamble length measurement request frame as a control frame so that a measurement frame for measuring the preamble length is transmitted from the slave station 2 as an uplink signal, and inserts it into the downlink signal. It is a circuit for performing processing.

  The slave station 2 includes an optical transmission / reception circuit 30, a downstream frame identification circuit 31, a control frame termination circuit 32, an ONT number storage unit 33, a preamble length storage unit 34, an ONT control circuit 35, an upstream frame identification circuit 36, a frame buffer 37, a control A frame insertion circuit 38 and a preamble length control circuit 39 are included.

  The optical transmission / reception circuit 30 includes a continuous signal optical transceiver similar to the optical transmission / reception circuit 10 of the master station 1, and includes an electrical / optical signal converter (E / O) 30a and an optical / electrical signal converter (O / E). 30b and a WDM coupler 30c. The optical transmission / reception circuit 30 converts an upstream signal from an electrical signal to an optical signal by the electrical / optical signal converter 30a and transmits the optical signal to the optical fiber 4, and transmits a downstream signal from the optical signal to the electrical signal by the optical / electrical signal converter 30b. To the downstream frame identification circuit 31. The WDM coupler 30 c is a coupler for demultiplexing the wavelength multiplexed signal transmitted from the master station 1 via the optical fiber 4. Further, the optical transmission / reception circuit 30 is configured to start or stop the optical output based on the control signal received from the ONT control circuit 35.

  The downstream frame identification circuit 31 is configured to identify an Ethernet (registered trademark) frame and a control frame, output the Ethernet (registered trademark) frame as a downstream output signal 52, and transmit the control frame to the control frame termination circuit 32. ing.

  The control frame termination circuit 32 has a function of identifying the contents of the control frame received from the downstream frame identification circuit 31 and transmitting control information to the ONT control circuit 35. Also, it has a function of identifying an ONT number assignment frame and transmitting the assigned ONT number to the ONT number storage unit 33 and a function of transmitting the optimum preamble length information included in the transmission permission frame to the preamble length storage unit 34. ing.

  The ONT control circuit 35 has a function of instructing the control frame insertion circuit 38 to issue a control frame in the upstream transmission direction based on the control information received from the control frame termination circuit 32. In addition, the optical transmitter / receiver circuit 30 has a function of transmitting a signal instructing activation and stop of the optical output.

  The upstream frame identification circuit 36 identifies an Ethernet (registered trademark) frame as the upstream input signal 53 and transmits it to the frame buffer 37. The control frame insertion circuit 38 is a circuit that generates a control frame according to a command received from the ONT control circuit 35 and inserts the control frame into the upstream signal.

  The control frame insertion circuit 38 includes a preamble length measurement frame insertion circuit 40, an ONT number assignment response frame insertion circuit 41, and a transmission end display frame insertion circuit 42. The preamble length measurement frame insertion circuit 40 is a circuit for inserting a preamble length measurement frame into an uplink signal in response to a preamble length measurement request from the master station 1. The ONT number assignment response frame insertion circuit 41 receives an ONT number assignment frame from the master station 1, generates a control frame for responding to the master station 1 that the ONT number has been assigned, and inserts it into the upstream signal. Circuit. The transmission end display frame insertion circuit 42 is a circuit for generating a control frame for notifying the master station 1 that transmission of the uplink signal is to end and inserting it into the uplink signal.

  The preamble length control circuit 39 is a functional unit that adds a preamble to an uplink signal based on the optimum preamble length information received from the preamble length storage unit 34 and transmits the uplink signal to the optical transmission / reception circuit 30. That is, when transmitting a signal to the master station 1, the preamble length control circuit 39 is specific to the slave station 2 based on the optimum preamble length information notified from the master station 1 at the head of the frame to be transmitted. It is configured to set a length preamble.

Next, the operation of the passive optical network system configured as described above will be described.
FIG. 2 is a sequence chart showing operations from registration of the slave station 2 to upstream signal conduction.
First, the slave station 2 is registered by associating the individual number of the slave station 2 with an arbitrary ONT number (step ST101). The master station 1 designates the registered individual number of the slave station 2 and inserts a preamble length measurement request frame in the downlink transmission direction from the preamble length measurement request frame insertion circuit 21 of the control frame insertion circuit 18. This preamble length measurement request frame is transmitted to each slave station 2 via the optical transmission / reception circuit 10 and branched by the star coupler 3 (step ST102).

FIG. 3 shows a configuration example of the control frame.
A preamble 70 in the figure is a synchronization pattern. The maintenance identifier 71 is an identifier indicating whether the frame is an Ethernet (registered trademark) frame, a control frame, or a preamble length measurement frame. The direction identifier 72 is an identifier indicating the transmission direction of the control frame. The command identifier 73 indicates that the control frame is a request, a response to the request, or an autonomous notification. The control signal 74 indicates the content of the control frame command, and the master station 1 or the slave station 2 that has received the control frame operates according to the value of the control signal 74. Taking the downlink transmission direction as an example, this control signal 74 identifies whether the control frame is a preamble length measurement request frame, an ONT number assignment frame, or a transmission permission frame.

  The ONT state 75 is included in the control frame in the upstream transmission direction, and is information for notifying the parent station 1 of the state of the slave station 2. The ONT number 76 indicates the ONT number of the slave station 2 to be controlled in the uplink transmission direction. For the downlink transmission direction, the ONT number of the slave station 2 that transmitted the control frame is shown. The control parameter 77 includes a different parameter for each control frame. For example, the preamble length measurement request frame includes the individual number of the slave station 2 to be requested as a parameter. The ONT number assignment frame transmitted in step ST105 of FIG. 2 described later includes the individual number of the slave station 2 to be assigned a number and the optimum preamble length measured by the master station 1 as parameters. In addition, the amount of data permitted to be transmitted is included as a parameter in the transmission permission frame transmitted in step ST109 of FIG. 2 described later. FCS 78 is a CRC code in the area of maintenance identifier 71 to control parameter 77 excluding preamble 70.

  Returning to FIG. 2, the slave station 2 that has received the preamble length measurement request frame refers to the ONT individual number included in the frame, and if it matches the individual number of itself, the slave station 2 sends the preamble length measurement frame to the master station 1. Transmit (step ST103). The master station 1 that has received the preamble length measurement frame measures the optimum preamble length, and holds the measurement value in association with the individual number of the slave station 2 (step ST104). That is, in the master station 1, when the received frame is identified as the preamble length measurement frame by the upstream frame identification circuit 11, the preamble length detection circuit 14 detects the optimum preamble length of the slave station 2 by processing to be described later. . The detected preamble length is stored in the preamble length storage unit 15.

FIG. 4 shows an example of the configuration of a preamble length measurement frame.
The preamble length measurement frame includes a synchronization pattern 80, a maintenance identifier 81, a frame length 82 from the beginning, an ONT individual number 83, and an FCS 84. The length of the entire frame is arbitrary, and the synchronization pattern 80, the maintenance identifier 81, and the frame length 82 from the top appear repeatedly from the top of the frame. The repetition of the synchronization pattern 80, the maintenance identifier 81, and the frame length 82 from the head is sufficient so that synchronization can be achieved even in the slave station 2 having the lowest optical output rising characteristics among all the connected slave stations 2. Length. The preamble length detection circuit 14 of the master station 1 that has received the preamble length measurement frame sets the frame length 82 from the head immediately after the synchronized synchronization pattern 80 as the optimum preamble length, and associates it with the ONT individual number 83 as a preamble. This is stored in the long storage unit 15.

  Next, the master station 1 inserts an ONT number assignment frame into the slave station 2 of the registered individual number by the ONT number assignment frame insertion circuit 20 and transmits it (step ST105). This frame includes the optimum preamble length information measured in the master station 1. The slave station 2 that has received the ONT number assignment frame retains the assigned ONT number and optimum preamble length information (step ST106). Thereafter, the slave station 2 receives only the frame of the assigned ONT number and discards the other frames. Further, when transmitting an uplink signal to the master station 1, a preamble having an optimum length is added based on the held optimum preamble length information and transmitted in the uplink transmission direction. The slave station 2 that has received the ONT number assignment frame transmits an ONT number assignment response frame to the master station 1 (step ST107).

  When the master station 1 receives the ONT number assignment response frame, the link is established between the master station 1 and the slave station 2 (step ST108). Master station 1 transmits a transmission permission frame to slave station 2 in the link established state (step ST109). The slave station 2 that has received the transmission permission frame starts transmission of the uplink signal (step ST110). The transmission permission frame includes transmission permission data amount information, and the slave station 2 transmits a transmission end display frame to the master station 1 after completing transmission of the uplink signal having the transmission permitted data amount (step S1). ST111), uplink signal transmission is terminated. At this time, the preamble having the optimum length is also added to the uplink signal and the transmission end display frame based on the optimum preamble length information notified in the ONT number assignment frame in step ST105.

  Receiving the transmission end display frame, master station 1 transmits a transmission permission frame similar to that in step ST109 to other slave stations 2 with which a link has been established. Thereafter, the same procedure is repeated in order to communicate with the plurality of slave stations 2 in the uplink transmission direction.

  In the downlink transmission direction, a downlink signal is transmitted by broadcast to all the slave stations 2 connected to the master station 1, and each slave station 2 receives only a frame displaying the ONT number assigned to itself. Discard everything except.

As described above, according to the first embodiment, the slave station 2 transmits a signal to the master station 1 and the preamble length measurement frame insertion circuit 40 that inserts the preamble length measurement frame into the transmission frame. A preamble length control circuit that sets a preamble based on information indicating a preamble length specific to a slave station that is measured from the master station 1 based on a preamble length measurement frame at the beginning of a frame of a signal to be transmitted 39 , the master station 1 and the slave station 2 are transmitted from the slave station 2 to the master station 1 even when using continuous signal optical transceivers with different times required for stable optical output operation. The signal can be received correctly.

  Further, since the master station 1 is notified when the master station 1 activates the slave station 2, no special processing is required for the notification of the preamble length, and the slave station 2 transmits a signal of the master station 1 When performing transmission / reception, it is possible to easily obtain the optimum preamble length of itself.

  In addition, since the preamble length information is notified in the control frame from the master station 1 to the slave station 2, the preamble length information can be notified from the master station 1 to the slave station 2 accurately and easily.

  The master station 1 inserts a preamble length measurement request frame for requesting each slave station 2 to transmit a preamble measurement frame into a transmission frame to the slave station 2. Accordingly, each slave station 2 can easily obtain the transmission timing of the preamble length measurement frame.

  Further, since the preamble length measurement frame insertion circuit 40 of the slave station 2 inserts a preamble measurement frame having an index from the head of the frame, the optimum preamble length of the slave station 2 can be measured in one frame. Can do.

  Further, when the master station 1 can receive the preamble length measurement frame from the slave station 2, a preamble length detection circuit that detects the length corresponding to the received position index as the optimum preamble length of the slave station 2. Therefore, the optimum preamble length corresponding to each slave station 2 can be easily detected from one frame.

Embodiment 2. FIG.
FIG. 5 is a configuration diagram of the passive optical network system according to the second embodiment.
The basic configuration of the system shown is the same as that of the first embodiment shown in FIG. 1, but the following configuration is different. That is, the preamble length detection circuit 14 included in the master station 1 of the first embodiment is not included, and the preamble length measurement request frame insertion circuit 21 is not included in the control frame insertion circuit 18a. The control frame insertion circuit 38a of the slave station 2 does not include the preamble length measurement frame insertion circuit 40.

  In the system of FIG. 5, as with the system shown in FIG. 1, one master station (OLT) 1 a is connected to a plurality of slave stations (ONT) 2 a via an optical fiber 4 via a star coupler 3. . The master station 1a includes an optical transmission / reception circuit 10, an upstream frame identification circuit 11a, a control frame termination circuit 12a, an ONT state control circuit 13, a preamble length storage unit 15, a downstream frame identification circuit 16, a frame buffer 17, and a control frame insertion circuit 18a. It is comprised including. Here, since the optical transmission / reception circuit 10, the ONT state control circuit 13, the preamble length storage unit 15, the downlink frame identification circuit 16, and the frame buffer 17 are the same as those in the first embodiment, the same reference numerals are given to corresponding parts. The description is omitted.

  The upstream frame identification circuit 11 a has a function of identifying an Ethernet (registered trademark) frame and a control frame, outputting the control frame to the control frame termination circuit 12 a and outputting the Ethernet (registered trademark) frame as an upstream output signal 50. . The control frame termination circuit 12a not only identifies and transmits the contents of the control frame received from the upstream frame identification circuit 11a to the ONT state control circuit 13, but also the ONT number assignment frame from the parent station 1a when the slave station 2a is activated. The preamble length of the ONT number assignment response frame transmitted in the uplink transmission direction in response to the function is detected and sent to the preamble length storage unit 15.

  As described above, the control frame insertion circuit 18a includes only the transmission permission frame insertion circuit 19 and the ONT number assignment frame insertion circuit 20. As in the first embodiment, the transmission permission frame insertion circuit 19 has a function of generating a control frame that permits transmission of an upstream signal to an arbitrary slave station 2a and inserting the control frame into the downstream signal. This transmission permission frame includes information on the amount of data permitted to be transmitted to the slave station 2a and information on the optimum preamble length that the slave station 2a should add to the uplink signal. The ONT number assignment frame insertion circuit 20 is a functional unit that generates a control frame for assigning an arbitrary ONT number to an arbitrary slave station 2a and inserts it into a downlink signal. The transmission of the ONT number assignment frame is performed when the slave station 2a is activated, and thereafter, the slave station 2a is configured to be monitored and controlled based on the ONT number.

  The slave station 2a includes an optical transmission / reception circuit 30, a downstream frame identification circuit 31, a control frame termination circuit 32, an ONT number storage unit 33, a preamble length storage unit 34, an ONT control circuit 35, an upstream frame identification circuit 36, a frame buffer 37, a control A frame insertion circuit 38a and a preamble length control circuit 39 are included. Here, since the configuration other than the control frame insertion circuit 38a is the same as that of the first embodiment, the corresponding parts are denoted by the same reference numerals and the description thereof is omitted.

  The control frame insertion circuit 38a includes an ONT number assignment response frame insertion circuit 41a and a transmission end display frame insertion circuit 42. The ONT number assignment response frame insertion circuit 41a receives the ONT number assignment frame from the master station 1a, generates a plurality of control frames for notifying the master station 1a that the ONT number has been assigned, and inserts it into the upstream signal. It has a function. The plurality of frames have different preamble lengths, and are configured to insert a frame with a short preamble length at first and insert a frame with gradually increasing preamble length. Similar to the first embodiment, the transmission end display frame insertion circuit 42 generates a control frame for notifying the master station 1a that transmission of the uplink signal is completed, and inserts the control frame in the uplink signal. It is.

Next, the operation of the passive optical network system configured as described above will be described.
FIG. 6 is a sequence chart showing an operation from registration of the slave station 2a to upstream signal conduction.
First, in the master station 1a, the slave station 2a is registered by associating the individual number of the slave station 2a with an arbitrary ONT number (step ST201). This process is the same as in the first embodiment.

  Next, the master station 1a designates the registered individual number of the slave station 2a, inserts an ONT number assignment frame in the downlink transmission direction from the control frame insertion circuit 18a, and transmits this as a control frame (step ST202). ).

  The configuration of the control frame is the same as that shown in FIG. However, the ONT number allocation frame includes only the individual number of the slave station 2a to be number allocated as a parameter, and does not include the optimum preamble length as in the first embodiment. In addition, the transmission permission frame includes, as parameters, the amount of data permitted to be transmitted and preamble length information of an optimum length that the slave station 2a should add to the uplink signal. Further, each of a plurality of ONT number assignment response frames transmitted from the slave station 2a to the master station 1a includes preamble length information added to the head of the frame as a parameter.

  The slave station 2a that has received the ONT number assignment frame refers to the ONT individual number included in the frame, and if it matches with its own individual number, the assigned ONT number is held in the ONT number storage unit 33 (step ST203). ). The ONT number assignment response frame insertion circuit 41a of the control frame insertion circuit 38a inserts a plurality of ONT number assignment response frames each having a different preamble length, and the slave station 2a transmits these frames to the master station 1a ( Step ST204). At this time, a plurality of ONT number assignment response frames are continuously transmitted, and a frame having a short preamble length is initially set, and a frame having a long preamble length is gradually transmitted. The preamble length at the start of transmission and the ratio of increasing the preamble length can be arbitrarily set.

  The master station 1a that has received such a plurality of ONT number assignment response frames cannot correctly receive the first several frames because the preamble length is short. Then, the control frame termination circuit 12a refers to the preamble length information included in the control parameter section 77 (see FIG. 3) of the ONT number assignment response frame that can be correctly received first. Next, it is associated with the ONT number assigned to the corresponding slave station 2a, and the value is sent to the preamble length storage unit 15 as the optimum preamble length, and the preamble length storage unit 15 holds this (step ST205). In step ST205, the master station 1a receives the ONT number assignment response frame, so that the link is established between the master station 1a and the slave station 2a.

  Next, a transmission permission frame is output from the control frame insertion circuit 18a of the master station 1a to the slave station 2a that has transmitted the ONT number assignment response frame (step ST206). This transmission permission frame includes a preamble length N corresponding to the slave station 2a together with the amount of transmission permission data. In the slave station 2a that has received this, the control frame termination circuit 32 sends the included preamble length to the preamble length storage unit 34, and the preamble length storage unit 34 holds this (step ST207).

  The slave station 2a that has received the transmission permission frame starts transmission of the uplink signal (step ST208). Further, when the slave station 2 has finished transmitting the uplink signal with the data amount permitted to be transmitted, it transmits a transmission end display frame to the master station 1a (step ST209), and terminates the transmission of the uplink signal. Thereafter, communication in the uplink transmission direction is performed with a plurality of slave stations 2a in the same procedure as in the first embodiment. Even in the downlink transmission direction, communication is performed in the same manner as in the first embodiment.

  As described above, according to the second embodiment, the slave station 2a continuously inserts ONT number assignment response frames having a short preamble length and gradually increasing the preamble length into the transmission frame. Since the response frame insertion circuit 41a is provided, the preamble length measurement for each slave station 2a can be easily realized.

  Further, since the master station 1a sets the preamble length of the frame that has been correctly received as the optimum preamble length of the slave station 2a, the frame insertion for measuring the preamble length is performed in the master station 1a and the slave station 2a. There is no need for a circuit, and it is not necessary to add a long preamble that can cover the rising characteristics of the optical outputs of all the slave stations 2a in the frame transmitted from the slave station 2a to the master station 1a. Even an unknown slave station can easily know the optimum preamble length.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the passive optical network system by Embodiment 1 of this invention. It is a sequence chart which shows operation | movement of the passive optical network system by Embodiment 1 of this invention. It is a frame block diagram of the passive optical network system by Embodiment 1 of this invention. It is a block diagram of the frame for passive optical network system preamble measurement by Embodiment 1 of this invention. It is a block diagram which shows the passive optical network system by Embodiment 2 of this invention. It is a sequence chart which shows operation | movement of the passive optical network system by Embodiment 2 of this invention.

Explanation of symbols

  1, 1a master station, 2, 2a slave station, 3 star coupler (multiple branching unit), 10, 30 optical transmission / reception circuit, 12, 12a control frame termination circuit, 14 preamble length detection circuit, 21 preamble length measurement request frame insertion circuit 39 Preamble length control circuit, 40 Preamble length measurement frame insertion circuit, 41 ONT number assignment response frame insertion circuit.

Claims (12)

One master station and a plurality of slave stations are connected via a multi-branch, and each uses a continuous signal optical transceiver, and the slave station receives a transmission permission from the master station in a burst manner. In a passive optical network system that transmits signals,
The slave station, when transmitting a signal to the parent station , a preamble length measurement frame insertion circuit that inserts a preamble length measurement frame into the transmission frame, from the parent station at the head of the frame of the signal to be transmitted the measured based on the frame preamble length measuring, based on information indicating a specific preamble length notified child station, a passive optical network, characterized in that a preamble length control circuit for setting a preamble system.   The passive optical network system according to claim 1, wherein the preamble length is notified when the master station activates the slave station.   2. The passive optical network system according to claim 1, wherein the preamble length information is notified in a control frame from the master station to the slave station. The master station includes a preamble length measurement request frame insertion circuit that inserts a preamble length measurement request frame for requesting transmission of a preamble length measurement frame to each slave station in a transmission frame to the slave station. The passive optical network system according to any one of claims 1 to 3 . 5. The passive light according to claim 1 , wherein the preamble length measurement frame insertion circuit inserts a preamble length measurement frame having a length index from the head of the frame. Network system. When the master station receives a preamble length measurement frame, the master station has a preamble length detection circuit that detects the length corresponding to the received position index as the optimum preamble length of the slave station that transmitted the preamble length measurement frame. The passive optical network system according to claim 5, further comprising: One master station and a plurality of slave stations are connected via a multi-branch, and each uses a continuous signal optical transceiver, and the slave station receives a transmission permission from the master station in a burst manner. In a passive optical network system that transmits signals,
The slave station is in the transmission frame, beginning with a short preamble length, the ONT number allocation response frame insertion circuit for inserting continuously gradually ONT number assignment response frame long preamble length, signal to the master station Is transmitted from the master station at the beginning of the frame of the signal to be transmitted, measured based on the continuously inserted ONT number assignment response frames, and notified information indicating the preamble length specific to the slave station And a preamble length control circuit for setting a preamble based on the above, a passive optical network system. 8. The control station termination circuit according to claim 7, further comprising: a control frame termination circuit that detects the preamble length of the ONT number assignment response frame as the optimum preamble length of the transmitted slave station when the master station is able to receive the ONT number assignment response frame for the first time. Passive optical network system. A plurality of slave stations are connected via a multi-branch, a transmission permission is sent to each slave station using a continuous signal optical transceiver, and each slave station transmits in bursts based on the transmission permission In the master station that receives the signal,
A preamble length measurement request frame insertion circuit for inserting a preamble length measurement request frame for requesting transmission of a preamble length measurement frame into a transmission frame to each of the slave stations;
A preamble length detection circuit for measuring a preamble length specific to each slave station based on the preamble length measurement frame transmitted from each slave station based on the preamble length measurement request frame. The master station. In a slave station that is connected to a master station via a multi-branch, receives a transmission permission from the master station, and transmits a burst signal using an optical transceiver for continuous signals,
A preamble length measurement frame insertion circuit for inserting a preamble length measurement frame into the transmission frame; and
When transmitting a signal to the master station, the preamble length specific to the slave station measured and notified from the master station based on the preamble length measurement frame is indicated at the beginning of the frame of the signal to be transmitted. A slave station comprising: a preamble length control circuit that sets a preamble based on information. A plurality of slave stations are connected via a multi-branch, a transmission permission is sent to each slave station using a continuous signal optical transceiver, and each slave station transmits in bursts based on the transmission permission In the master station that receives the signal,
The ONT number assignment response frame which is transmitted continuously from each of the slave stations and which is initially short and gradually lengthened the preamble length is received, and the preamble length based on the ONT number assignment response frame which has been correctly received first is A preamble length storage unit for storing the optimum preamble length for the slave station;
A master station comprising a transmission permission frame insertion circuit that generates a transmission permission frame that includes the preamble length stored in the preamble length storage unit and is output to each of the slave stations. In a slave station that is connected to a master station via a multi-branch, receives a transmission permission from the master station, and transmits a burst signal using an optical transceiver for continuous signals,
An ONT number assignment response frame insertion circuit that continuously inserts ONT number assignment response frames that are initially short and gradually increase the preamble length;
A preamble length control circuit configured to set a preamble based on information indicating a preamble length specific to the slave station measured and notified based on the continuously inserted ONT number assignment response frames. A slave station.

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