JP2007081520A - Data transmission system and communication terminal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize protection which can be switched in a short time on a ring transmission path. <P>SOLUTION: Signals on a ring transmission path 10 are transmitted clockwise, and signals on a ring transmission path 12 are transmitted counterclockwise. An OLT 14 and ONUs 16-1 to 16-6 each output an idle pattern to the ring transmission paths 10, 12 in a non-data period. If not receiving an idle pattern from an upstream in the non-data period, the OLT 14 and the ONUs 16-1 to 16-6 each output a link switching signal to the downstream of the ring transmission paths 10, 12. An apparatus for transmitting data selects or switches a data path based on the received link switching signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a data transmission system and a communication terminal device.

  A ring-type optical transmission system having two ring optical transmission lines that transmit optical signals in opposite directions is attracting attention. RPR (Resilient Packet Ring) is known as such a ring-type optical transmission line protection method (Patent Documents 1 and 2).

Further, Patent Documents 3 and 4 describe methods for improving the confidentiality of communication by dividing and transmitting a transmission signal.
JP 2004-242194 A JP 2004-023480 A JP 2000-115162 A Japanese Patent Laid-Open No. 10-70531

  There is a demand for a communication method with high bandwidth utilization efficiency while concealing communication contents. In addition, a protection system that can be switched in a short time with a redundant configuration is also desired.

  An object of this invention is to show the data transmission system and communication terminal device which satisfy | fill such a request | requirement.

  A data transmission system according to the present invention includes first and second ring transmission lines that transmit signals in opposite directions, and a plurality of communication terminal devices arranged on the first and second ring transmission lines. This is a data transmission system. Characteristically, each communication terminal device outputs an idle pattern to the first and second ring transmission lines in the no-data period, respectively, and no data from the first and second ring transmission lines. An idle pattern discriminating device that determines the presence or absence of an idle pattern in a period and outputs an idle pattern non-detection signal when the idle pattern is not detected, and other idle patterns are detected according to the idle pattern non-detection signal from the idle pattern discrimination device. A link switching signal output device for outputting a link switching signal addressed to the communication terminal device to the first and second ring transmission lines.

  A communication terminal apparatus according to the present invention is a communication terminal apparatus arranged on first and second ring transmission lines that transmit signals in opposite directions, and a signal input from an upstream side of the first transmission line. Among the signals transmitted from the upstream side of the first transmission path, the first transmission signal is multiplexed on the other signals addressed from the upstream side of the first transmission path, and the downstream of the first ring transmission path. The first transfer system that outputs to the side and the signal that is addressed to itself among the signals that are input from the upstream side of the second transmission path are separated, and the signals that are input from the upstream side of the second transmission path A second transmission system that multiplexes a second transmission signal with a signal addressed to the other side and outputs the second transmission signal to the downstream side of the second ring transmission path, and an idle pattern in the no-data period, respectively. Idle pattern output device for outputting to transmission line, and first and second ring transmissions An idle pattern discriminating device for discriminating whether or not there is an idle pattern in a no-data period and outputting an idle pattern non-detection signal when the idle pattern is not detected, and the idle pattern non-detection signal from the idle pattern discriminating device And a link switching signal output device for outputting a link switching signal to the first and second ring transmission lines.

  According to the present invention, the path can be switched more quickly than in the past by the link switching signal.

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

  FIG. 2 is a schematic configuration diagram of a ring type optical transmission system according to an embodiment of the present invention. There are a ring optical transmission line 10 for transmitting the signal light in the clockwise direction and a ring optical transmission line 12 for transmitting the signal light in the counterclockwise direction. The ring optical transmission lines 10 and 12 are arranged on the center station on the ring optical transmission lines 10 and 12. The optical terminal unit (ONT: Optical Line Terminal) 14 and the optical terminal unit (ONU: Optical network unit) placed in each user's home, similar to the OLT placed in the center station in the star network PON system 16 (16-1 to 16-6) are arranged. A computer 18 is connected to the OLT 14, and computers 20 (20-1 to 20-6) are also connected to the ONUs 16 (16-1 to 16-6). Instead of the computers 18 and 20, a communication device such as a local area network (LAN) such as a router may be connected.

  The OLT 14 manages all the ONUs 16-1 to 16-6 connected to the ring optical transmission lines 10 and 12. Specifically, the OLT 14 manages whether or not the ONUs 16-1 to 16-n can be transmitted, their timings and bandwidths, and manages communication / broadcasting services that can be used by the respective ONUs 16-1 to 16-6. Except for this management function, the OLT 14 and the ONU 16 have the same data transmission / reception function.

  FIG. 1 shows a schematic block diagram of the ONU 16-2. The internal configurations of the other ONUs 16-1, 16-3 to 16-6 are the same as those of the ONU 16-2. The OLT 14 also has the same configuration as the ONU 16-2 regarding data transmission / reception. Here, in order to identify the OLT 14 and the ONUs 16-1 to 16-6 on the ring transmission lines 10 and 12, it is assumed that a unique number, that is, a terminal ID is assigned to each. For a unified understanding, OLT 14 is also expressed as ONU 16-0. The number of the OLT 14 is 0, and the numbers of the ONUs 16-1 to 16-6 are 1 to 6, respectively.

  The optical / electrical converter 30a receives signal light from the adjacent ONU 16-3 via the optical transmission line 10-2 that constitutes a part of the ring transmission line 10. The optical / electrical converter 30a converts an input optical signal into an electrical data signal. The buffer 32a temporarily stores data output from the optical / electrical converter 30a. The destination discriminating device 34a discriminates the destination of the data temporarily stored in the buffer 32a, switches the selector 36a to the receiving buffer 70a for the data destined for itself among the output data of the buffer 32a, and sends the data destined for the others. On the other hand, the selector 36a is switched to the transfer multiplexer 38a. The data destined for the other includes a link switching signal generated or transferred by the ONU 16-3. Details of the link switching signal will be described later.

  The multiplexing device 38a multiplexes the data from the transmission frame generating device 68 and the link switching signal from the link switching signal generating device 52 on the time axis to the data from the selector 36a, that is, data destined for others.

  The output of the multiplexer 38a is temporarily stored for rate adjustment in the buffer 40a, and the output of the buffer 40a is supplied to the no-data detecting device 42a and the selector 44a. The no-data detection device 42a detects whether there is valid data in the output of the buffer 40a. The selector 44a normally supplies the output data of the buffer 40a to the electrical / optical converter 46a. In the case of no data, the no-data detection device 42a causes the selector 44a to select the idle pattern output from the idle pattern generation device 48. That is, in this embodiment, when valid data addressed to another exists, the valid data is applied to the electrical / optical converter 46a. The idle pattern generated by the generation device 48 is applied to the electric / optical converter 46a.

  The electrical / optical converter 46a converts the electrical signal from the selector 44a into an optical signal. The optical signal output from the electrical / optical converter 46a propagates through the optical transmission line 10-1 constituting a part of the ring transmission line 10 and is input to the adjacent ONU 16-1.

  The same applies to the processing system for signals transmitted through the ring transmission path 12. Signal light is input to the optical / electrical converter 30b from the adjacent ONU 16-1 through the optical transmission line 12-1 that constitutes a part of the ring transmission line 12. The optical / electrical converter 30b converts an input optical signal into an electrical data signal. The buffer 32b temporarily stores data output from the optical / electrical converter 30b. The destination discriminating device 34b discriminates the destination of the data temporarily stored in the buffer 32b, switches the selector 36b to the receiving buffer 70b for the data destined for itself among the output data of the buffer 32b, and sends the data destined for others. On the other hand, the selector 36b is switched to the transfer multiplexer 38b. The data destined for the other includes a link switching signal generated or transferred by the ONU 16-1.

  The multiplexing device 38b multiplexes the data from the transmission frame generating device 68 and the link switching signal from the link switching signal generating device 52 on the time axis to the data from the selector 36b, that is, data destined for others.

  The output of the multiplexer 38b is temporarily stored for rate adjustment in the buffer 40b, and the output of the buffer 40b is supplied to the no-data detecting device 42b and the selector 44b. The no-data detection device 42a detects whether there is valid data in the output of the buffer 40b. The selector 44b normally supplies the output data of the buffer 40b to the electrical / optical converter 46b. In the case of no data, the no-data detection device 42b causes the selector 44b to select the idle pattern output from the idle pattern generation device 48. That is, in the present embodiment, when valid data addressed to another exists, the valid data is applied to the electrical / optical converter 46b, and in the period when there is no valid data addressed to another, the idle pattern The idle pattern generated by the generation device 48 is applied to the electric / optical converter 46b.

  The electrical / optical converter 46b converts the electrical signal from the selector 44b into an optical signal. The optical signal output from the electrical / optical converter 46b propagates through the optical transmission line 12-2 constituting a part of the ring transmission line 12 and is input to the adjacent ONU 16-3.

  As described above, the idle pattern generation device 48 generates an idle pattern to be transferred downstream during a no-data period when there is no data to be transferred to the downstream device. The idle pattern may not cover 100% of the no data period. When the idle pattern has to be a pattern that changes according to a certain rule of a certain length, an idle pattern for the ring transmission line 10 that generates an idle pattern in synchronization with the switching control signal for the selector 44a of the no-data detecting device 42a. An idle pattern generation device for the ring transmission line 12 that generates an idle pattern may be provided in synchronization with the pattern generation device and the switching control signal for the selector 44b of the no-data detection device 42b.

  The idle pattern discriminating device 50 discriminates whether or not an idle pattern is included in the non-data period of the electrical signals output from the optical / electrical converters 30a and 30b. In any case, while the idle pattern is not included in the no-data period, the idle pattern discriminating device 50 notifies the link switching signal generating device 52, the isolated terminal discriminating device 60, and the control device 66 of the idle pattern non-detection signal or the idle pattern. Continue to output the pattern undetected flag. The idle pattern non-detection signal indicates a failure in the optical transmission path between the upstream device and the own device, a failure in the electrical / optical converter in the upstream device, or a failure in the optical / electrical converter in the own device. However, since the failure of the electrical / optical converter and the optical / electrical converter can be separately detected by an electrical monitoring device, in this embodiment, the idle pattern non-detection signal is transmitted between the upstream device and the own device. Used to detect optical transmission line failures.

  The link switching signal generation device 52 generates a link switching signal according to the idle pattern non-detection signal from the idle pattern determination device 50. The link switching signal includes information indicating the source device (here, ONU 16-29). The destinations are all communication devices (here, OLT 14, ONUs 10-1, 10-3 to 10-6) on the ring transmission lines 10 and 12, except for themselves. Therefore, there is no need to individually specify the destination. Broadcast may be specified. The link switching signal indicates that the link is down on the upstream side of the source terminal.

  The link switching signal generated by the link switching signal generator 52 is sent out on the ring transmission line 10 by the multiplexing device 38a, and is sent out on the ring transmission line 12 by the multiplexing device 38b. Of course, the multiplexers 38a and 38b multiplex the ring switching signal with other signals on the time axis so as not to overlap other signals.

  The link switching signal discriminating device 54 separates the link switching signal from the electrical signals output from the optical / electrical converters 30a and 30b, and discriminates the source of the link switching signal. The link switching signal determination device 54 supplies information for identifying the OLT 14 or ONU 16 that generates the link switching signal, for example, the terminal ID, to the isolated terminal determination device 60 and the control device 66.

  Transmission data from the PC 20-2 is input to the selector 56 and the destination determination device 58. The transmission data is composed of, for example, an Ethernet (registered trademark) frame, and includes information on a destination address and a source address. The destination discriminating device 58 discriminates the destination from the transmission data and supplies the corresponding terminal ID to the isolated terminal discriminating device 60 and the destination information table 62.

  The selector 56 normally supplies the transmission data from the PC 20-2 to the encryption device 64. The destination information table 62 stores information for specifying an encryption method to be applied for each destination. The destination information table 62 supplies information indicating the encryption method corresponding to the destination of the transmission data to the encryption device 64. In the present embodiment, as the data transmission method with the highest security, division transmission is used in which transmission data is divided into two frames (divided frames), transmitted on different transmission paths, and combined on the receiving side. By using encryption together with this divided transmission, high data confidentiality is demonstrated. The same serial number is added to specify the divided frames that are paired with each other. The destination information table 62 supplies the serial number to the transmission frame generation device 68.

  The encryption device 64 encrypts the transmission data input from the selector 56 with the encryption method specified by the encryption method information from the destination information table 62, and generates a transmission frame of a data frame including the encrypted transmission data Supply to device 68.

  The transmission frame generation device 68 can select transmission using a single transmission path (single transmission) or transmission using two transmission paths (divided transmission). By making the serial number sequence to be added different depending on whether it is single transmission or divisional transmission, the receiving side can identify whether it is single transmission or divisional transmission.

  In the case of divided transmission, the transmission frame generation device 68 divides the encrypted frame from the encryption device 64 into two parts, adds the same serial number to each divided frame, sends one divided frame to the multiplexer 38a, and the other divided frame. The frame is supplied to the multiplexer 38b. As a result, one divided frame is transmitted through the ring transmission path 10 and reaches the destination apparatus, and the other divided frame is transmitted through the ring transmission path 12 and reaches the destination apparatus. In the case of single transmission, the transmission frame generation device 68 outputs data to the transmission path side designated by the control device 66.

  The control device 66 controls the strength or presence of encryption of the encryption device 64 and controls whether or not the transmission frame generation device 68 needs to divide the frame. In this embodiment, it is possible to select a plurality of levels of data confidentiality depending on the presence / absence and strength of encryption by the encryption device 64 and the presence / absence of divided transmission.

  The data addressed to itself is received as follows and transmitted to the computer 20-2. That is, the destination discriminating device 34a switches the selector 36a to the buffer 70a side for the data addressed to the ONU 14-2 among the data stored in the buffer 32a. Thereby, the data addressed to the ONU 14-2 output from the buffer 32a is supplied to the buffer 70a via the selector 36a. Similarly, the destination discriminating device 34b switches the selector 36b to the buffer 70b side for the data addressed to the ONU 14-2 among the data stored in the buffer 32b. Thereby, the data addressed to the ONU 14-2 output from the buffer 32b is supplied to the buffer 70b via the selector 36b.

  The synthesizing device 72 compares the serial numbers added in units of frames to the data stored in the buffers 70a and 70b, and synthesizes frames having the same serial number. When the data is transmitted through a single transmission line, the synthesizer 72 outputs the data from the buffers 70a and 70b to the decryption device 74 as it is. The decrypting device 74 decrypts the data from the synthesizing device 72 when it is encrypted, and outputs it as it is when it is not encrypted. The output data of the decryption device 74 is supplied to the computer 20-2 as received data. The control device 66 controls whether or not the decryption device 74 needs to decrypt and supplies the necessary decryption key to the decryption device 74.

  In the ring transmission system as shown in FIG. 2, the OLTs 14 and 16-1 are caused by a failure in the ring transmission lines 10 and 12 or a failure in the transfer function of the OLTs 14 and 16-1 to 16-6 on the ring transmission lines 10 and 12. Any of ˜16-6 may be isolated. The isolated terminal discriminating device 60 uses the terminal isolated from the idle pattern non-detection signal from the idle pattern discriminating device 50 and the terminal ID from the link switching signal discriminating device 54, that is, which of the ring transmission lines 10 and 12 is used. It is possible to distinguish an isolated terminal from which data cannot be reached. The isolated terminal discriminating device 60 is further supplied with a terminal ID indicating the destination of the transmission data from the destination discriminating device 58. The isolated terminal determination device 60 switches the selector 56 from the encryption device 64 to the data discard terminal when the destination of the transmission data is an isolated terminal. Thereby, the transmission data to the isolated terminal is discarded without being sent out on the ring transmission lines 10 and 12. Thereby, useless traffic on the ring transmission lines 10 and 12 can be reduced.

  A data transmission procedure according to the present embodiment will be described based on a specific example. For example, in a situation in which the OLT 14 is secretly transmitting data to the ONUs 16-1 to 6 by split transmission, a failure occurs in the transmission paths 10-3, 12-3 between the ONUs 16-2, 16-3, Assume that a failure also occurs in the transmission lines 10-4 and 12-4 between the ONU 16-3 and the ONU 16-4 after some time. FIG. 3 shows the change with time. Time passes from top to bottom.

  When the ring transmission lines 10 and 12 are both in a normal state, the OLT 14 and each of the ONUs 16-1 to 16-6 transmit an idle pattern toward an adjacent device in a no-data period (S1). Thereby, OLT14 and each ONU16-1-16-6 can confirm that there is no trouble in the data transmission between adjacent apparatuses. In this state, the OLT 14 can perform secret communication (D1a, D1b) by divided transmission and encryption for any of the ONUs 16-1 to 16-6.

  Assume that a failure has occurred in the transmission paths 10-3 and 12-3 between the ONU 16-2 and the ONU 16-3. As a result, the ONU 16-2 cannot receive data and idle patterns from the ONU 16-3, and the ONU 16-3 cannot receive data and idle patterns from the ONU 16-2. As a result, the ONU 16-2 outputs the link switching signal S2a to the downstream side of the ring transmission path 10 and the link switching signal S2b to the downstream side of the ring transmission path 12. Similarly, the ONU 16-3 outputs the link switching signal S3a to the downstream side of the ring transmission path 10 and the link switching signal S3b to the downstream side of the ring transmission path 12.

  Since a failure has occurred in the transmission lines 10-3 and 12-3 between the ONU 16-2 and the ONU 16-3, the link switching signal S2b cannot reach the ONU 16-3, and the link switching signal S3a is the ONU 16-2. Cannot reach.

  On the other hand, the link switching signal S2a is sequentially received by the ONU 16-1, the OLT 14, the ONU 16-6, the ONU 16-5, the ONU 16-4, and the ONU 16-3. The ONU 16-3 outputs a link switching signal S2a to the transmission line 10-3, but the link switching signal S2a cannot reach the ONU 16-2 due to a failure in the transmission line 10-3.

  The link switching signal S3b is sequentially received by the ONU 16-4, ONU 16-5, ONU 16-6, OLT 14, ONU 16-1, and ONU 16-2. The ONU 16-2 outputs a link switching signal S3b to the transmission line 12-3, but the link switching signal S3b cannot reach the ONU 16-3 due to a failure in the transmission line 12-3.

The link switching signal S2a includes a signal specifying the ONU 16-2 as a generation source of this signal, and the link switching signal S3b includes a signal specifying the ONU 16-3 as a generation source of this signal. The OLT 14 serving as the data transmission source can know that a failure has occurred in the transmission paths 10-3 and 12-3 between the ONU 16-2 and the ONU 16-3 by using the link switching signals S2a and S3b. This means that split transmission to the ONUs 16-1 to 16-6 is impossible. Therefore, the OLT 14 receives the data D for any of the ONUs 16-3 to 16-6.
2a is sent to the ring transmission line 10, and data D2b for either the ONU 16-1 or 16-2 is sent to the ring transmission line 12.

  Here, it is further assumed that a failure has occurred in the transmission lines 10-4 and 12-4 between the ONU 16-3 and the ONU 16-4. As a result, the ONU 16-4 cannot receive data and idle patterns from the ONU 16-3, and the ONU 16-3 cannot receive data and idle patterns from the ONU 16-4. The ONU 16-4 outputs the link switching signal S4a to the transmission line 10-4, and outputs the link switching signal S4b to the downstream side of the ring transmission line 12.

  Since a failure has occurred in the transmission lines 10-4 and 12-4 between the ONU 16-3 and the ONU 16-4, the link switching signal S4a cannot reach the ONU 16-3.

  On the other hand, the link switching signal S4b is sequentially received by the ONU 16-5, ONU 16-6, OLT 14, ONU 16-1, and ONU 16-2. The ONU 16-2 outputs a link switching signal S4b to the transmission line 12-3, but the link switching signal S4b cannot reach the ONU 16-3 due to a failure in the transmission line 12-3.

  The link switching signal S4b includes a signal designating the ONU 16-4 as a generation source of this signal. The OLT 14 that is the data transmission source has newly failed in the transmission lines 10-4 and 12-4 between the ONU 16-3 and the ONU 16-4 due to the link switching signal S4b newly received from the ring transmission line 12. You can know what you did. Since the OLT 14 is known to have a failure in the transmission lines 10-3 and 12-3 between the ONU 16-2 and the ONU 16-3 by the previous link switching signals S2a and S3b, It can be seen that the ONU 16-3 is isolated. Therefore, the OLT 14 sends the data D3a for any one of the ONUs 16-4 to 16-6 to the ring transmission line 10, sends the data D3b for the ONUs 16-1 and 16-2 to the ring transmission line 12, and the isolated ONU 16- Data for 3 is discarded by the selector 56.

  Although the case where the OLT 14 is the data transmission source has been described, the switching operation of the ring transmission lines 10 and 12 to be used is also performed when the ONUs 16-1, 2, 4, 5, and 6 are the data transmission source. The same as in the case of OLT14.

  When the ONU 16-3 transmits data to the OLT 14 or the ONUs 16-1, 16-2, and 16-4 to 6, the following operation is performed in response to the above-described failure. That is, when a failure occurs in the transmission lines 10-3 and 12-3, the ONU 16-3 does not receive data or an idle pattern from the ONU 16-2. In response to this, the ONU 16-3 generates the link switching signals S3a and S3b as described above, and performs ring transmission as a data path to be transmitted to the OLT 14 or the ONUs 16-1, 16-2, and 16-4 to 6-6. Specify the path 12. In the case of secret communication, the encryption method is switched to a method that is more difficult to decipher and a new encryption method is notified to the receiving device.

  Further, when a failure occurs in the transmission lines 10-4 and 12-4, the ONU 16-3 does not receive data or an idle pattern from the ONU 16-4. As a result, the ONU 16-3 knows that it is isolated, stops data transmission, and notifies the computer 20-3 accordingly.

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

It is a schematic block diagram of the optical termination unit (ONU) in one Example of this invention. It is an example of the network structure of one Example of this invention. It is an example of an operation sequence when a failure occurs in the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 12: Ring optical transmission line 10-3, 10-4: Transmission line 12-3, 12-4: Transmission line 14: Optical termination device (OLT)
16 (16-1 to 16-6): Optical termination unit (ONU)
18, 20 (20-1 to 20-6): computers 30a, 30b: optical / electrical converters 32a, 32b: buffers 34a, 34b: destination discriminating devices 36a, 36b: selectors 38a, 38b: multiplexers 40a, 40b: Buffers 42a, 42b: No data detection devices 44a, 44b: Selectors 46a, 46b: Electric / optical converter 48: Idle pattern generation device 50: Idle pattern discrimination device 52: Link switching signal generation device 54: Link switching signal discrimination device 56 : Selector 58: Destination discrimination device 60: Isolated terminal discrimination device 62: Destination information table 64: Encryption device 66: Control device 68: Transmission frame generation device 70 a, 70 b: Buffer 72: Synthesis device 74: Decryption device

Claims (11)

First and second ring transmission lines (10, 12) that transmit signals in opposite directions, and a plurality of communication terminal devices (10, 12) arranged on the first and second ring transmission lines (10, 12) 14, 16-1 to 16-6),
Each communication terminal device
Idle pattern output devices (42a, 42b, 44a, 44b, 48) for outputting idle patterns to the first and second ring transmission lines, respectively, in a non-data period;
An idle pattern discriminating device (50) for discriminating whether or not there is an idle pattern in a no-data period from the first and second ring transmission lines and outputting an idle pattern non-detection signal when the idle pattern is not detected;
A link switching signal output device (52) for outputting a link switching signal addressed to another communication terminal device to the first and second ring transmission lines in accordance with the idle pattern non-detection signal from the idle pattern discrimination device (50). , 38a, 38b)
A data transmission system comprising: The idle pattern output device
An idle pattern generation device (48) for generating the idle pattern;
A first no-data detection device (42a) for detecting the presence or absence of data to be output to the first ring transmission line;
A first selector that outputs the output idle pattern of the idle pattern generation device (48) to the first ring transmission line (10) during the non-data period according to the detection result of the first no-data detection device (42a). (44a)
A second no-data detection device (42b) for detecting the presence or absence of data to be output to the second ring transmission line;
A second selector that outputs the output idle pattern of the idle pattern generation device (48) to the second ring transmission line (12) during the non-data period according to the detection result of the second no-data detection device (42b). (44a)
The data transmission system according to claim 1, further comprising: The link switching signal output device is
A link switching signal generation device (52) for generating a link switching signal in accordance with the idle pattern non-detection signal from the idle pattern discrimination device (50);
A first multiplexer (38a) that multiplexes the link switching signal with a signal to be output to the first ring transmission line (10);
A second multiplexer (38b) that multiplexes the link switching signal with a signal to be output to the second ring transmission line (12).
The data transmission system according to claim 1 or 2, further comprising:   Each of the communication terminal devices further includes a device (66, 68) that switches the output destination of the transmission signal in accordance with the link switching signal received from either the first or second ring transmission line. The data transmission system according to claim 1, wherein the data transmission system is a data transmission system.   Each of the communication terminal devices further includes an isolated terminal determination device (60) that determines an isolated communication terminal device in accordance with the link switching signal received from the first and second ring transmission lines, and the isolated communication. The data transmission system according to any one of claims 1 to 4, further comprising a signal discarding device (56) for discarding a transmission signal to the terminal device. Each communication terminal device
Among the signals input from the upstream side of the first transmission line (10), the signal addressed to itself is separated, and the signal addressed to the other side among the signals input from the upstream side of the first transmission line (10). A first transfer system that multiplexes the first transmission signal to the downstream side of the first ring transmission path (10), and
A signal addressed to itself among the signals input from the upstream side of the second transmission path (12) is separated, and a signal addressed to the other of the signals input from the upstream side of the second transmission path (12). And a second transfer system that multiplexes the second transmission signal and outputs the multiplexed signal to the downstream side of the second ring transmission line (12). The data transmission system described in 1. A communication terminal device disposed on the first and second ring transmission lines (10, 12) for transmitting signals in opposite directions,
Among the signals input from the upstream side of the first transmission line (10), the signal addressed to itself is separated, and the signal addressed to the other side among the signals input from the upstream side of the first transmission line (10). A first transfer system (30a, 32a, 34a, 36a, 38a, 40a, 46a) that multiplexes the first transmission signal and outputs the multiplexed signal to the downstream side of the first ring transmission line (10);
A signal addressed to itself among the signals input from the upstream side of the second transmission path (12) is separated, and a signal addressed to the other of the signals input from the upstream side of the second transmission path (12). A second transfer system (30b, 32b, 34b, 36b, 38b, 40b, 46b) that multiplexes the second transmission signal and outputs the multiplexed signal to the downstream side of the second ring transmission line (12);
Idle pattern output devices (42a, 42b, 44a, 44b, 44) for outputting idle patterns to the first and second ring transmission lines, respectively, in a no-data period;
An idle pattern discriminating device (50) for discriminating whether or not there is an idle pattern in a non-data period from the first and second ring transmission lines and outputting an idle pattern non-detection signal when the idle pattern is not detected;
A link switching signal output device (52, 38a, 38b) that outputs a link switching signal to the first and second ring transmission lines in accordance with the idle pattern non-detection signal from the idle pattern discriminating device (50).
A communication terminal device. The idle pattern output device
An idle pattern generation device (48) for generating the idle pattern;
A first no-data detection device (42a) for detecting the presence or absence of data to be output to the first ring transmission line;
A first selector that outputs the output idle pattern of the idle pattern generation device (48) to the first ring transmission line (10) during the non-data period according to the detection result of the first no-data detection device (42a). (44a)
A second no-data detection device (42b) for detecting the presence or absence of data to be output to the second ring transmission line;
A second selector that outputs the output idle pattern of the idle pattern generation device (48) to the second ring transmission line (12) during the non-data period according to the detection result of the second no-data detection device (42b). (44a)
The communication terminal device according to claim 7, further comprising: The link switching signal output device is
A link switching signal generation device (52) for generating a link switching signal in accordance with the idle pattern non-detection signal from the idle pattern discrimination device (50);
A first multiplexer (38a) that multiplexes the link switching signal with a signal to be output to the first ring transmission line (10);
A second multiplexer (38b) that multiplexes the link switching signal with a signal to be output to the second ring transmission line (12).
The communication terminal device according to claim 7 or 8, characterized by comprising:   The apparatus further comprises a device (66, 68) for switching an output destination of the transmission signal in accordance with the link switching signal received from any one of the first and second ring transmission lines. The communication terminal device according to any one of 1 to 9.   Further, an isolated terminal discriminating device (60) for discriminating an isolated communication terminal device according to the link switching signal received from the first and second ring transmission lines, and a transmission signal to the isolated communication terminal device 11. The communication terminal device according to claim 7, further comprising a signal discard device that discards the signal.

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