JP4044558B2 - Optical transmission apparatus and system - Google Patents

Abstract

A method and system for two-way optical transmission with the same wavelength between an office transmission circuit and a user terminal transmission circuit through a one-core optical fiber, wherein when an optical fiber disconnection failure occurs, the office transmission circuit locates the corresponding user terminal transmission circuit by detecting the response failure of the user terminal transmission circuit so as to automatically detect the optical fiber disconnection failure without connecting any special measuring instrument, and sends an optical isolated pulse to the user terminal transmission circuit corresponding to the response failure, whereby the failure point is located.

Description

  The present invention relates to an optical transmission system, and more particularly, to an optical transmission method and system for bidirectional transmission of the same wavelength using a single-core optical fiber.

  Conventionally, when bidirectional transmission is performed in an optical transmission system, uplink / downlink transmission is generally performed using a two-core optical fiber. In order to increase the transmission capacity of the optical fiber, WDM (wavelength division multiplexing) transmission may be performed in each of the upstream and downstream directions.

  On the other hand, since there are many access systems connecting the office (station side) of a telecommunications carrier and the user's home (inside of the home), it is economical that bidirectional transmission can be performed with a single optical fiber. As a single-core bidirectional optical transmission system, there is a WDM bidirectional transmission system that uses different wavelengths for upstream and downstream, but it is necessary to prepare light-emitting elements of different wavelengths, and wavelength dependence on the multiplexer / demultiplexer There is an economic limit, such as having to have sex. Also, since wavelength is a valuable resource that is the same as radio waves, it is desirable that one service can be transmitted bidirectionally at one wavelength.

  As such a single-wavelength single-core bidirectional transmission system, there are a time-axis compressed multiplex bidirectional optical transmission system and an echo canceller bidirectional optical transmission system, and the operating principle of both is the same as in the case of metallic transmission.

Single core same wavelength bidirectional transmission system (1 to 1 connection: Fig. 7)
Here, the operation of the former single-core single-wavelength time-axis compression multiplexed bidirectional optical transmission system will be described with reference to FIG. The principle of the time axis compression multiplex bidirectional transmission system is described in detail in the document “Multimedia Network Series Digital Access System” (Ohm Co., Ltd.) and the like, and is omitted here.

  First, the station-side transmission circuit 1 and the in-home transmission circuit 2 face each other through the optical fiber 30. Information transmitted from the station-side transmission circuit 1 to the in-home transmission circuit 2 is time-axis-compressed by the station-side transmission logic circuit unit 11 and converted into optical pulses by the station-side electric / optical conversion circuit unit 12. It is sent to the optical fiber 30 through the coupler 13.

  In the in-home transmission circuit 2, the optical pulse received from the optical fiber 30 via the in-home optical coupler 23 is returned to an electrical signal by the in-home optical / electrical conversion circuit unit 24, and this is further converted into the in-house reception logic circuit unit 25. To extract the original speed information.

  Similarly, in the reverse direction information transmission from the in-house transmission circuit 2 to the station-side transmission circuit 1, the time axis is compressed by the in-house transmission logic circuit unit 21 and converted into an optical pulse by the in-house electric / optical conversion circuit unit 22. Then, it is sent to the optical fiber 30 via the in-home optical coupler 23. In the station-side transmission circuit 1, the optical pulse received from the optical fiber 30 via the station-side optical coupler 13 is returned to an electrical signal by the station-side optical / electrical conversion circuit unit 14, and the time-axis is received by the station-side reception logic circuit unit 15. Extract and retrieve the original speed information.

  Further, the station-side control circuit unit 16 generates control signals and the like necessary for time axis operation from the clock pulses in the station. Further, the in-home control circuit unit 26 extracts clock information necessary for time axis operation from the received pulse train, and generates a necessary control signal and the like.

  Next, transmission and reception of transmission signals between the station side transmission circuit 1 and the in-house transmission circuit 2 during normal operation will be described with reference to FIG.

  First, the downlink burst signal 1112 transmitted from the station side transmission circuit 1 is received by the in-home transmission circuit 2 after receiving attenuation and propagation delay time (Tps) due to loss in the optical fiber 30. When the indoor transmission circuit 2 finishes receiving the downlink burst signal 1112, it transmits the uplink burst signal 1114 after a protection time (Tg) for preventing uplink-downlink interference. The upstream burst signal 1114 is received by the station-side transmission circuit 1 after receiving attenuation due to loss in the optical fiber 30 and propagation delay time (Tpr).

  Here, the occupation time (Tis) of the downlink burst signal 1112 is equal to the occupation time (Tir) of the uplink burst signal. Also, the downlink propagation delay time (Tps) and the uplink propagation delay time (Tpr) are equal. The sum of the up / down burst signal occupation time (Tis, Tir), the up / down propagation delay time (Tps, Tpr), and the protection time (Tg) is the burst cycle time (Tb).

Echo canceller bidirectional optical transmission system (one-to-one connection: Fig. 9)
The latter echo canceller bidirectional optical transmission system will be described with reference to FIG.

  In this echo canceller bidirectional optical transmission system, in FIG. 7, the station-side transmission circuit 1 has a station-side echo canceller circuit unit 17 and a station-side subtracter 18, and the premises transmission circuit 2 is a premises echo canceller circuit unit. 27 and a house subtractor 28.

  Note that the principle of the echo canceller bidirectional transmission method is also omitted here because it is well known in the above-mentioned document “Multimedia Network Series Digital Access Method” (Ohm).

  First, the station-side transmission circuit 1 and the in-home transmission circuit 2 face each other through the optical fiber 30. The information transmitted from the station side to the inside of the house is added with a frame synchronization signal or the like by the station side transmission logic circuit unit 11 and becomes an optical pulse by the station side electric / optical conversion circuit unit 12 and passes through the station side optical coupler 13. To the optical fiber 30. On the premises, after receiving the received light pulse from the optical fiber 30 through the premises optical coupler 23 to the premises optical / electrical conversion circuit 24 and processing the frame synchronization signal in the premises reception logic circuit 25, Retrieve the original information.

  Information transmission from the inside of the house in the reverse direction to the station side is also performed by adding a frame synchronization signal or the like at the inside transmission logic circuit unit 21 and forming an optical pulse at the inside electric / optical conversion circuit unit 22, 23 to the optical fiber 30. On the station side, the received optical pulse is guided from the optical fiber 30 through the station side optical coupler 13 to the station side optical / electrical conversion circuit unit 14, and after the frame synchronization signal is processed by the station side reception logic circuit unit 15. , Retrieve the original information.

  The above operation is the same as that of the time-axis compressed multiplex bidirectional optical transmission system shown in FIG. 7, except that in the echo canceller bidirectional optical transmission system, upstream / downstream transmission signals are transmitted on the optical fiber 30 during information transfer. It differs from the time-axis compressed multiplex bidirectional optical transmission system in that it is mixed simultaneously.

  Here, the operation of the echo canceller system will be described with reference to FIG. The station-side echo canceller 17 performs training at the start of communication. The training signal 3112 from the station-side transmission logic circuit unit 11 is sent as an optical signal 3113 to the optical fiber 30 via the station-side optical coupler 13.

  The sum of the reflected signal 3114 of the training signal 3113 sent to the optical fiber 30 and the training signal 3115 leaked by the station-side optical coupler 13 is input to the station-side optical / electrical conversion circuit unit 14 and converted into an electrical signal. The

  The station-side echo canceller 17 generates a signal (this is called an echo signal) that cancels the sum signal of the leakage signal 3115 to the receiving side and the reflected signal 3114 from the optical fiber based on the station-side training signal 3112. Set its own operating parameters.

  During normal operation, upstream / downstream transmission signals continuously flow on the optical fiber 30 at the same time, but the station-side subtracter 18 receives signals received from the inside of the house from the station-side optical / electrical conversion circuit unit 14. A signal leaked from the station side transmission signal is added, and an echo signal is added from the station side echo canceller 17. As a result, the output signal of the station side subtracter 18 becomes only the received signal from the inside of the house and is sent to the station side receiving logic circuit unit 15. Since the operation of the echo canceller inside the house is the same, the description is omitted.

  The station-side control circuit unit 16 generates necessary control signals such as a frame synchronization signal from the station-side clock SCK. Further, the in-home control circuit unit 26 extracts information such as a frame synchronization signal from the received pulse train, and generates a necessary control signal. Note that the echo canceller bidirectional optical transmission system also has a maximum applicable distance (Lmax) as a system due to limitations due to optical fiber loss. This will be described later.

  The former time-axis compression multiplex bidirectional optical transmission system requires a simple optical coupler because the upstream and downstream signals are separated in time, but the transmission signal speed is twice that of the information speed. More than necessary.

  In the latter echo canceller bidirectional optical transmission system, the transmission signal speed is almost the same as the information speed, but it is necessary to use a directional coupler for the optical coupler in order to improve the upstream / downstream separation. .

Single-core single-wavelength time-axis compression multiplexed bidirectional optical transmission system (one-to-many connection: Fig. 11)
The time-axis compressed multiplex bidirectional optical transmission system as the same wavelength single-core bidirectional transmission system described above uses the optical branching device to share the optical fiber and the information band among a plurality of users, and achieves economy. This is applied to a wavelength one-to-multiple connection type optical branching bidirectional optical transmission system.

  The operation of the single-core single-wavelength one-to-multiple connection type optical branching bidirectional optical transmission system will be described with reference to FIG. Note that the above-described echo canceller bidirectional optical transmission system is not applied to this transmission system.

  This single-core single-wavelength one-to-multiple connection type optical branching bidirectional optical transmission system is a kind of optical transmission system called a PON (Passive Optical Network) system, and for example, the document “xDSL / FTTH” ( Since it is well-known to the ASCII Publishing Bureau, the explanation is omitted here.

  In this single-core single-wavelength one-to-multiple connection type optical branching bidirectional optical transmission system, an optical transmission line termination circuit (hereinafter referred to as OLT (Optical Line Termination circuit)) 101 corresponding to the above-mentioned station-side transmission circuit 1; An optical network terminator (hereinafter referred to as an ONU (Optical Network Unit)) 201 corresponding to the in-home transmission circuit 2 is 1: N connected through an optical branching device 300. Here, N is an integer indicating the number of connected ONUs.

  The transmission information is accommodated in a predetermined time slot, and a control byte necessary for communication as a PON system that performs one-to-many connection type optical branching bidirectional optical transmission is added and transferred as necessary. In the downstream direction from the OLT 101 to each ONU 201 # 1 to 201 # N (hereinafter sometimes collectively referred to as reference numeral 201), information time slots addressed to each ONU 201 are multiplexed and continuously transferred. Extract only the information time slots.

  On the other hand, the upstream direction from each ONU 201 to the OLT 101 is transferred in a predetermined time slot unit instructed from the OLT 101. That is, as shown in FIG. 12, in the burst period Tb, the time until the burst signal 1112 in the downstream direction returns from the station side OLT 101 → the home side ONU 201 → the station side OLT 101 is defined as the all ONU operation guarantee window Tw. By sending an optical pulse 2112 for delay time measurement from the side OLT 101 to the new ONU 2011, the delay time Ta unique to the ONU 2011 is measured in advance. Then, the time slot Ts1 is assigned to the existing ONU 2012, and the time slot Ts2 is assigned to the new ONU 2011 to transmit the burst signal.

  As described above, when the ONU 2011 is newly installed while the existing ONU 2012 is in operation, the station-side OLT 101 is used for delay time measurement including the information that “ONU responds to unassigned time slots” within the all ONU operation guarantee window Tw. The pulse train 2112 is transmitted by broadcast. When the new ONU 2011 receives this, it returns a response pulse train 2114 including its own ID information.

  When the station-side OLT 101 receives a response from the new ONU 2011, the station-side OLT 101 measures the delay time Ta, and transmits the designated time slot and the delay adjustment time Td to the new ONU 2011 in the frame information F.

  The delay time measurement pulse train 2112 can be inserted in every burst period, or can be inserted once every several seconds, and can also be inserted by an external instruction when an ONU is newly established.

  The new ONU 2011 reads out its own time slot position Ts2 and delay adjustment time Td from the frame information F at the head of the burst signal from the station-side OLT 101, and sends the information sequence sent from the station-side OLT 101 in the form of a broadcast. Only the information of the designated time slot Ts2 is received.

  Further, the new ONU 2011 calculates the transmission timing to the station side OLT 101 from the protection time Tg (fixed value), the delay adjustment time Td (which varies depending on the distance between the ONU and the OLT), and the time slot position designation time Tt (which varies depending on the ONU). Information is transmitted to the designated time slot Ts2.

  In these two-way optical transmissions, optical signals are transferred after being compressed on the time axis in the upstream and downstream directions.

  The time axis compression operation and expansion operation in the transmission of information transmitted from the station side to the house side and information in the reverse direction from the house side to the station side are performed as shown in FIG.

  That is, the bit stream of the transmission information of the station-side OLT 101 is compressed on the time axis for each burst period (Tb), and is sent to, for example, the time slot Ts1 in the signal 1112 and sent to the in-home ONU 201. The bit stream compressed in the time axis of the time slot Ts1 is expanded in the time axis by the in-home ONU 201 to return to the original speed, and used as the bit stream of the in-home reception information.

  As a result, the station side information at the bit stream position A (arrow) in FIG. 13 is reproduced at the bit stream position A ′ (arrow) of the in-home information.

  The difference between the one-core time-axis compressed multiplex bidirectional optical transmission method and the one-to-many connection type optical branching bidirectional optical method based on the PON method is that uplink information from each connected ONU 201 collides on the station side of the optical branching device. Thus, TDMA (Time Domain Multiple Access) control is performed to prevent the information from being broken.

  Information time slots Ts1, Ts2 (see FIG. 12) from the ONUs 2012 and 2011 (see FIG. 12) to be sent to the OLT 101 are sent at a predetermined timing based on a send delay time instruction from the OLT 101. Information time slots Ts1, Ts2 from ONUs 2012, 2011 are identified.

  The operation of FIGS. 12 and 13 will be further described with reference to FIG.

  The downlink burst signal 1112 transmitted from the station-side OLT 101 is data including an information time slot addressed to each ONU 201, and receives attenuation and propagation delay time (Tps) due to loss in the optical fiber. Received.

  At this time, the data received by each ONU 201 has different attenuation and propagation delay time depending on the distance from the OLT 101. The in-home ONU 201 extracts the information time slot addressed to the ONU #k from the down burst signal 1112 and, after receiving it, the up information from each ONU 201 in the protection time (Tg) for preventing uplink / downlink interference. After delaying the delay adjustment time (Td) for avoiding the collision, information is transmitted to the time slot Ts # k indicated by the OLT 101 in the time zone of the upstream burst signal 1114. The upstream burst signal 1114 is received at the station side after receiving attenuation and propagation delay time (Tpr) in the optical fiber 30.

  Here, the upstream burst signal 1114 received by the station-side OLT 101 is a set of information time slots transmitted from each ONU 201. In this case, the occupation time (Tis) of the downlink burst signal 1112 is equal to the occupation time (Tir) of the uplink burst signal. Further, the downlink propagation delay time (Tps) and the uplink propagation delay time (Tpr) are the same for each ONU 201, but the distance from the OLT 101 is different if the ONU 201 is different, and therefore the value is also different for each ONU 201.

  The sum of the occupation time of the uplink / downlink burst signal, the uplink / downlink propagation delay time, the protection time, and the delay adjustment time is the burst cycle time (Tb).

  In the single-core single-wavelength one-to-multiple connection type optical branching bidirectional optical transmission system, there is a maximum applicable distance (Lmax) as a system. This maximum distance is used to determine a delay time for adjusting each ONU 201 to be logically equidistant from the OLT 101.

  That is, in order to avoid the collision of the upstream burst signal 1114 from each ONU 201 and thus to ensure the operation of all ONUs, each ONU 201 transmits the information time so that all ONUs 201 exist at the Lmax position as a logical distance. Adjust the slot delay time.

  This delay time adjustment mechanism will be described with reference to FIG. In this figure, two in-home ONUs, the inside-home ONU # j and ONU # k, are connected. The delay adjustment time is notified from the station-side OLT 101 to each in-home ONU 201 based on the result of measuring the transmission line distance between the station-side OLT 101 and each in-home ONU 201.

  At this time, the delay adjustment time Tdi for the in-home ONU # i is such that the relationship shown in the following equation holds between the propagation delay time Tpi corresponding to the transmission distance Li and the maximum propagation time Tpmax corresponding to the maximum application distance Lmax. It is decided.

2Tpi + Tg + Tdi = 2Tpmax + Tg (1)
= Constant value where Tg is the protection time.

Cutting failure whereas the optical fiber, all transmission method described above, that is, when the cutting failure of the optical fiber at the same wavelength single-core bidirectional optical transmission system occurs, using a measuring instrument called OTDR (Optical Time Domain Reflectometer) The cutting point was detected.

  That is, in this OTDR, in order to accurately detect the cutting point of the optical fiber, Fresnel reflected light and backscattered light of the measurement light pulse are received, integrated, and displayed on the display.

  Such a method is excellent in terms of accurately detecting the failure point, but it can be replaced by connecting the optical connector to the terminal of the optical termination of the failed optical fiber, or the optical line maintenance already known. The measuring instrument must be connected via an optical splitter and an optical switch as in the support system.

  For this reason, when replacing an optical connector, it is necessary to identify the optical fiber terminal that caused the failure from many optical termination terminals and connect a measuring instrument. There is a drawback in that it is impossible to prevent a measuring instrument from being mistakenly connected to a normal optical fiber due to a mistake.

  In addition, there is a disadvantage that a large facility is required to connect the measuring instrument via the optical splitter and the optical switch.

  Furthermore, in order to detect a conventional optical fiber break point, it is necessary to use a measurement-dedicated wavelength that is different from the wavelength for transmitting information, and incorporating a measurement function in an optical transceiver circuit increases the circuit scale. That was difficult.

  Also, the conventional optical fiber break point detection work is to connect the measuring instrument manually with an optical fiber termination according to the operator's instruction when a failure occurs, or connect the measuring instrument by controlling the optical switch according to the instruction from the operation support system. In either case, operator intervention was required.

  In the same wavelength one-to-multiple connection type optical bi-directional optical transmission system, the main fiber from the station side transmission circuit to the optical branching device can detect the cut point using OTDR. The detection of the break point in the branch fiber connected to the home is difficult because it is difficult to specify which branch fiber has failed because the test light pulse is branched and multiple reflected.

  Further, conventionally, the optical transmission device and the measuring device for detecting the optical fiber break point are completely different, and there is no one that is integrated.

Therefore, the present invention is the same between a station-side transmission circuit and a home-side transmission circuit having a one-to-many connection relationship in a one-to-many connection type optical branching time-axis compression multiplex bidirectional optical transmission system using a single- core optical fiber. In a method and system for performing bidirectional optical transmission at a wavelength, an object of the present invention is to enable automatic detection of an optical fiber cutting failure without connecting a special measuring instrument.

  In the present invention, the failure point detection of the optical fiber is limited to the detection of the disconnection point, the operation of the transmission circuit on the station side is normally operated, and the disconnection for transmitting the isolated pulse for measuring the optical fiber disconnection point and measuring the time until reception is measured. This is realized by switching to the point detection operation.

For this reason, in the optical transmission method according to the present invention, the station-side transmission circuit detects the corresponding in-house transmission circuit due to the response failure of the in-house transmission circuit, and the operation provided in the station-side transmission circuit. The changeover switch switches the input from the transmission logic circuit to the isolated pulse generation circuit based on the detected response failure, and the down burst based on the pulse from the isolated pulse generation circuit toward the in-home transmission circuit corresponding to the response failure A distance to a fault point is detected based on the reflected light isolated pulse reflected and received in the optical transmission path by transmitting an optical isolated pulse having the same wavelength as the signal from the same light emitting element to the optical transmission path. It includes 2 steps, and該局side transmission circuit when it detects the response failure for any one of a該宅inner transmission circuit in the first step, in the second step Immediately after a predetermined burst signal is transmitted in the downstream direction, the isolated optical pulse is sent to the transmission line within the operation guarantee time until the burst signal returns, and the reflected light isolated pulse is received to the point of failure. It is characterized by performing distance detection .

  In other words, when a failure occurs, for example, in which an optical fiber that is a transmission medium is cut, a response cannot be made from the inside of the house, and an upstream signal from the inside transmission circuit cannot be received from the station-side transmission circuit.

  In such a case, conventionally, the station side transmission circuit generates an alarm of response failure, and at the operator's instruction, a measuring instrument called OTDR is brought to the front of the optical fiber termination and it seems that a failure has occurred. The measurement was performed by accessing the optical fiber by replacing the optical connector.

  Further, when a measuring instrument is connected via an optical splitter and an optical switch, the optical switch is operated from the operation support system to perform a measurement for detecting a cutting point.

On the other hand, in the present invention, when a response failure occurs from the in-home transmission circuit, the station-side transmission circuit detects this (first step), and automatically switches from normal operation to failure point detection operation, By transmitting an optical isolated pulse having the same wavelength as the downlink burst signal from the same light emitting element to the optical transmission line based on the pulse from the isolated pulse generating circuit toward the in-home transmission circuit related to the response failure, the optical transmission The distance to the obstacle point can be measured based on the reflected light isolated pulse reflected and received in the road (second step).

  As described above, according to the present invention, when an optical fiber disconnection failure occurs in the single-core single-wavelength bidirectional transmission system, the cut point can be detected in the transmission circuit without using OTDR. For this reason, it is not necessary to replace the optical connector and connect the measuring instrument, thereby reducing the measuring operation and preventing the measuring instrument from being mistakenly connected to a normal optical fiber by human error. be able to. In addition, a large facility for connecting the measuring device via the optical splitter and the optical switch is not required.

  Furthermore, it is not necessary to use a wavelength exclusively for measurement for detecting the optical fiber break point, and the wavelength for transmitting information itself may be used, so that a measurement function can be incorporated in an optical transmission / reception circuit with a slight increase in circuit scale. .

In the above case, when the station side transmission circuit and the premises transmission circuit are in a one-to-many connection relationship as shown in FIG. When the transmission circuit detects the response failure for any one of the in-house transmission circuits in the first step, the transmission circuit immediately after the predetermined downlink burst signal is transmitted in the second step. Within the operation guarantee time until the rising burst signal is returned, the distance to the fault point is detected by the reflected light isolated pulse which is transmitted to the transmission line and received .

That is, the station-side transmission circuit transmits an optical isolated pulse within each premises within a time period during which the burst signal 1112 shown in FIGS. 12 and 13 is transmitted from the station-side OLT and returns to the home-side ONU. It is sent to the ONU and the distance to the failure point is detected.

  This will be explained more specifically. When a response failure occurs on the optical fiber as the transmission medium, communication cannot be attempted from the all-home inner transmission circuit ONU when the backbone fiber on the station side of the optical branching device is disconnected, When viewed from the station side, an upstream burst signal from the inside of the house cannot be received even if communication is attempted.

  In addition, when a branch fiber failure occurs, an upstream burst signal (information time slot from the in-home ONU) cannot be received from the in-home ONU. Therefore, when the branch line fiber is disconnected, the station-side OLT generates an alarm that the received frame is out of synchronization or the time slot is not received from the ONU.

  Conventionally, in this state, a measurement device called OTDR is carried in front of the optical fiber termination by an operator's instruction, and the measurement is performed by accessing the optical fiber that seems to have failed by replacing the optical connector. It was. Further, when a measuring instrument is connected via an optical splitter and an optical switch, the optical switch is operated from the operation support system to perform a measurement for detecting a cutting point.

  However, as described above, in this method, the backbone fiber from the station side transmission circuit to the optical branching device can detect the cut point using OTDR, but the branch fiber connected from the optical branching device to each user's home. Since the test light pulse is branched and multiple-reflected in the detection of the break point at, it is difficult to specify which branch line fiber has failed.

  In the present invention, when a failure occurs in which the optical fiber is disconnected, the operation of the station-side optical transmission line termination circuit is automatically switched from the normal operation to the disconnection point detection operation. The distance to the cutting point can be measured.

  As described above, in the single-core single-wavelength one-to-multiple connection type optical branching bidirectional optical transmission system according to the present invention, the operation of the ONU accommodated in the branch fiber other than the branch fiber in which the failure occurs in the case of the branch fiber disconnection failure. The optical fiber cutting point can be detected without affecting the above.

  In addition, when a response failure occurs, the operation support system is notified of the result, and the operation support system that receives the failure notifies the station side transmission circuit to switch the station side transmission circuit from the normal operation to the disconnection point detection operation. By instructing, it is possible to measure the distance to the response failure point in the station side transmission circuit.

  Therefore, the present invention has means for autonomously notifying the operation support system of the detection result of the optical fiber break point from the optical transmission device that has detected the failure, so that no operator intervention is required when a failure occurs.

In the system to realize an optical transmission method according to the invention described above,該局side transmission circuit detects the corresponding home-side transmission circuit by impaired response該宅inner transmission circuit, provided in該局side transmission circuit The operation changeover switch switches the input from the transmission logic circuit to the isolated pulse generation circuit based on the detected response fault, and goes down based on the pulse from the isolated pulse generation circuit toward the in-home transmission circuit corresponding to the response fault. rows that have a distance detection to the fault point based on the reflected light isolated pulse received is reflected by the optical transmission path by sending light isolated pulse having the same wavelength as the burst signal from the same light emitting element to the optical transmission line The station-side transmission circuit detects the response failure for any one of the in-house transmission circuits and transmits the optical isolated pulse to the transmission line within a predetermined operation guarantee time. It is possible to perform the distance detection of up to the point of failure out.

In the above system, when the station side transmission circuit detects the response failure, the station side transmission circuit notifies the operation support system of the result, and receives a switching instruction from the normal operation to the cut point detection operation from the operation support system. The distance to the fault point can be detected.

Furthermore, in the present invention, an operation changeover switch provided in the station-side transmission circuit is detected in a station-side transmission circuit that performs bidirectional optical transmission with the same wavelength to the premises transmission circuit using a single-core optical fiber. And a first means for switching the input from the transmission logic circuit to the isolated pulse generation circuit based on the response failure and detecting a corresponding in-home transmission circuit by the response failure of the in-home transmission circuit, and the inside of the home corresponding to the response failure Based on the pulse from the isolated pulse generation circuit toward the transmission circuit, an optical isolated pulse having the same wavelength as the downlink burst signal is transmitted from the same light emitting element to the optical transmission line, and is reflected and received in the optical transmission line. a second means for detecting a distance to the fault point based on the reflected light isolated pulse comprises, the response disabled for any one of a該宅inner transmission circuit by the first means The time of detection, by said second means, it is possible to perform distance detection to the fault point by sending the light isolated pulse to the transmission path at a predetermined operation guarantee time.

Further, in the above transmission circuit, when the first means detects the response failure, the first means notifies the operation support system of the result, and receives a switching instruction from the normal operation to the cut point detection operation from the operation support system. When this occurs, the second means can detect the distance to the point of failure.

Furthermore, the above-described methods, systems, and the transmission circuit, it is possible to perform bidirectional optical transmission in a time axis compression multiplex scheme.

  As described above, according to the present invention, there is an advantage that a cutting point of an optical fiber can be detected without using an expensive measuring instrument. In addition, it is not necessary to replace the optical connector of the optical termination terminal of the optical fiber in which the measuring device has failed, and to connect the measuring device via the optical splitter and the optical switch.

  For this reason, when replacing the optical connector, many operations for identifying the optical fiber terminal that caused the failure from among the many optical termination terminals and connecting the measuring instrument are unnecessary, and human error is caused. There is an advantage that it is possible to prevent a measuring instrument from being mistakenly connected to a normal optical fiber.

  In addition, there is an advantage that a large facility for connecting a measuring instrument via an optical splitter and an optical switch is not required.

  Furthermore, there is an advantage that it is not necessary to use a measurement-dedicated wavelength different from the wavelength for transmitting information as in the conventional detection of the cut point of an optical fiber, and the cut point of the optical fiber can be detected only by the wavelength for transmitting information. is there.

  Since the measurement function is realized by switching the operation of the station-side transmission circuit of the single-core single-wavelength bidirectional optical transmission system, there is an advantage that the cost increase due to the addition of the function is small. Further, since there is almost no increase in circuit scale, there is an advantage that the functions can be integrated into the conventional optical transceiver module.

  Furthermore, in the one-to-many connection type optical branching bi-directional optical transmission system, by utilizing the delay measurement function provided in the PON transmission system, there is no influence on the branch fiber without affecting other users in the current service. There is an advantage that a break point can be detected.

  Advantages of drastically reducing operator operations, as optical fiber disconnection failure is detected by transmission signal disconnection, and the station-side transmission circuit autonomously switches the operation to the operation support system. There is.

Single core same wavelength bidirectional transmission system (1 to 1 connection: Fig. 1 and 7)
FIG. 1 shows an embodiment of a station-side transmission circuit according to the present invention, which uses a single-core, single-wavelength time-axis compression multiplexed bidirectional optical transmission system. In this embodiment, in the conventional example of FIG. 7, the station side transmission logic circuit unit 11 is composed of a station side transmission logic circuit 111, an isolated pulse generation circuit 112, and a transmission side operation changeover switch 113, and the station side control circuit unit 16 Is composed of a station-side control circuit 161 and a timer circuit 162, and the station-side reception logic circuit unit 15 includes an equalization amplifier circuit 151, a timing extraction circuit 152, an identification circuit 153, a station-side reception logic circuit 154, and a gain changeover switch 155. And an identification clock changeover switch 156 and a reception-side operation changeover switch 157.

  The station-side electrical / optical conversion circuit unit 12 includes a driver circuit 121 and a light emitting element 122, and the local-side optical / electrical conversion circuit unit 14 includes a light receiving element 141 and a preamplifier circuit 142. Is the same as the conventional example described above.

  Next, the operation of this embodiment will be described.

  Now, when the station side transmission circuit 1 is performing a normal operation, the switches 113 and 115 to 157 are in positions opposite to those shown in the figure. That is, the station-side transmission logic circuit 111 is connected to the station-side electrical / optical conversion circuit unit 12, the switch 155 is connected to the variable gain terminal G2, the timing extraction circuit 152 is connected to the identification circuit 153, and the identification circuit 153 is It is connected to the station side reception logic circuit 154.

  FIG. 2 shows a connection relationship between the station-side transmission apparatus 10 and the operation support system 7. In general, one station side transmission apparatus 10 has a plurality of station side transmission circuits 1 shown in FIG. For information to be transmitted, N station-side transmission circuits 1 # 1 to 1 # N are connected to other devices via a multiplexing / demultiplexing unit 4.

  The alarms from the station-side transmission circuits 1 # 1 to 1 # N and the setting control for the station-side transmission circuits 1 are collected by the common control unit 5 of the station-side transmission device 10 and transferred by a LAN or the like. It communicates with an operation support system (OSS) 7 via the network 6.

  Normally, communication between the operation support system and the transmission apparatus is performed in the form of a packet message having the contents shown in FIG.

  The operation support system 7 has an input / output device 8 that controls a human-machine interface with an operator. The input / output device 8 is usually a personal computer or a workstation. The optical fibers 30 # 1 to 30 # N from each station-side transmission circuit 1 are connected to the optical fiber extending to the user's home by the optical fiber termination 9 and the optical connector 90. The failure is determined.

  Needless to say, in order to make the detection of the cut point more reliable, the light emission power of the optical isolated pulse transmitted from the station side transmission circuit may be set to be twice or more than the light emission power in the normal operation. Needless to say, in order to accurately obtain the distance to the cutting point, it is only necessary to perform a plurality of measurements and average the values.

  When the station-side reception logic circuit 154 detects a disconnection state of the reception signal, an alarm is transmitted from the station-side control circuit 161 to the operation support system 7 via the common control unit 5 of the station-side transmission device 10. The operator of the operation support system 7 gives an instruction to switch from the normal operation to the disconnection point detection operation to the corresponding station side transmission circuit 1 upon seeing the alarm.

  When an instruction from the operation support system 7 is received, the station side control circuit 161 detects the transmission point operation switch 113, the gain switch 155, the identification clock switch 156, and the reception operation switch 157 as shown in FIG. Switch to operating mode.

  When the operation of the station-side transmission circuit 1 is switched to the cut-off point detection operation, the station-side transmission logic circuit unit 11 causes the optical signal propagation time corresponding to twice the maximum application distance (Lmax) as shown in FIG. An isolated pulse is generated with a period longer than (Tmax), and the isolated pulse becomes an optical isolated pulse 312 in the station-side electrical / optical conversion circuit unit 12 and is sent to the optical fiber 30 through the station-side optical coupler 13. .

  As shown in the figure, this optical isolated pulse 312 propagates through the optical fiber 30 from the station side to the inside of the house while being attenuated by optical loss, and is almost totally reflected at the cut point 31 of the optical fiber and returns to the station side. come. The reflected light isolated pulse 314 received via the station-side optical coupler 13 is converted into an electrical signal by the station-side optical / electrical conversion circuit unit 14 and input to the station-side reception logic circuit unit 15.

  In the disconnection point detection operation, the station side reception logic circuit unit 15 is different from the normal operation state, and the equalization function of the regenerative relay function (equalization amplification, timing extraction and identification function) is fixed to the maximum gain. The identification function waits for the reflected light isolated pulse 314 with a normal threshold (usually 0.5).

  The station-side control circuit unit 16 starts a timer for counting the time from the time when the above-mentioned isolated pulse is generated by the station-side transmission logic circuit unit 11, and the received reflected light isolated pulse 314 is determined to be present by the identification function. At that time, the timer circuit 162 is stopped.

The value of this timer is divided by 2, still is divided by the propagation delay time per unit length of light in the optical fiber, it is possible to determine the distance (L) to the cutting point in the station side or Stanislaus Lo Kuang fiber. The timer clock may be used exclusively for the timer or may be used by dividing or multiplying the clock CP of the transmission path signal as it is.

Echo canceller bi-directional optical transmission system (one-to-one connection: Figs. 5 and 9)
Figure 5 shows an example of the station-side transmission circuit according echo canceller bidirectional optical transmission system is another example of one-to-one connection.

In this example , in the conventional example of FIG. 9, the station side transmission logic circuit unit 11 is composed of a station side transmission logic circuit unit 111, an isolated pulse generation circuit 112, and a transmission side operation changeover switch 113, and the station side control circuit unit 16 Is composed of a station-side control circuit 161 and a timer circuit 162. The station-side reception logic circuit unit 15 includes an equalization amplifier circuit 151, a timing extraction circuit 152, an identification circuit 153, a station-side reception logic circuit 154, and a gain changeover switch 155. It is characterized by comprising an identification clock changeover switch 156 and a reception side operation changeover switch 157, and a station side echo canceller operation changeover switch 171 is added to the station side echo canceller circuit unit 17.

  The station-side electrical / optical conversion circuit unit 12 includes a driver circuit 121 and an issuing element 122, and the local-side optical / electrical conversion circuit unit 14 includes a light receiving element 141 and a preamplifier circuit 142. Is the same as before.

Here, the operation in this case will be described.

  The cut point detection operation of the station side transmission circuit 1 will be described in detail with reference to FIG. 5 and FIG. In the figure, the transmission side operation changeover switch 113, the gain changeover switch 155, the identification clock changeover switch 156, the reception side operation changeover switch 157, and the station side echo canceller operation changeover switch 171 are switched to the breakpoint detection operation mode. In the operation mode, each switch is switched to the opposite side.

  That is, when the reception signal disconnection is detected by the station-side reception logic circuit 154, an alarm is transmitted from the station-side control circuit 161 to the operation support system 7 via the common control unit 5 of the station-side transmission device 10. The operator of the operation support system OSS gives an instruction to switch from the normal operation to the cut point detection operation shown in the figure to the corresponding station side transmission circuit 1 upon seeing the alarm.

  In the station side control circuit 161, when an instruction is received from the operation support system 7, the transmission side operation changeover switch 113, the gain changeover switch 155, the identification clock changeover switch 156, the reception side operation changeover switch 157, and the station side echo canceller operation changeover switch 171. Is switched to the cut point detection operation mode.

  The isolated pulse generation circuit 112 generates a disconnection point detection isolated pulse from the isolated pulse repetition period pulse and the transmission path clock pulse CP, and passes through the transmission side operation changeover switch 113 to the driver circuit 121 and the station side echo canceller circuit unit 17. At the same time, an isolated pulse is also sent to the start terminal of the timer circuit 162.

  In the cut point detection operation, the station-side echo canceller circuit unit 17 stops the operation including the training because the station-side echo canceller operation changeover switch 171 is OFF. The driver circuit 121 drives the light emitting element 122 with an isolated pulse to convert it into a light isolated pulse. This optically isolated pulse is sent to the optical fiber 30 through the local optical coupler 13.

  As shown in FIG. 4, in the echo canceller bidirectional optical transmission system, there is no burst period as in the time-axis compressed multiplex bidirectional optical transmission system, so twice the propagation time of the maximum transmission distance (Lmax) (Tmax The solitary pulse may be transmitted with a period longer than (). In the figure, the transmitted light isolated pulse 312 is totally reflected at the cut point 31 of the optical fiber 30 to become a received light isolated pulse 314.

  That is, the light isolated pulse 314 reflected at the cut point 31 of the optical fiber passes through the local optical coupler 13 and enters the light receiving element 141, and is taken out as an electrical signal by the preamplifier circuit 142. This electric signal is applied to the station-side subtracter 18, but the station-side echo canceller circuit unit 17 has stopped its operation, so that it is amplified as it is by the equalization amplifier circuit 151 and added to the identification circuit 153.

  Here, there is no problem if the equalization amplifier circuit 151 has a fixed gain. However, since the AGC (Automatic Gain Control) is normally operated, the gain of the equalization amplifier circuit 151 is switched in the cut point detection operation mode. The maximum gain is fixed by the switch 155.

  In the normal operation mode, the clock extracted from the received signal by the timing extraction circuit 152 is used as the clock of the identification circuit 153. In the disconnection point detection operation mode, the transmission clock on the transmission side is switched by switching the identification clock switch 156. .

  Here, in order to reliably identify the received optical isolated pulse 314 with the transmission-side transmission path clock, the time width of the transmitted optical isolated pulse 312 is set to be twice or twice the reciprocal of the transmission path clock frequency. Needless to say, it is good.

  When the reception isolated pulse 314 is identified by the identification circuit 153, the identification output is applied to the stop terminal of the timer circuit 162 via the reception side operation changeover switch 157. The timer circuit 162 starts measurement when a pulse is applied to the start terminal, and stops measurement when a pulse is applied to the stop terminal.

  Here, in order to prevent the transmission light isolated pulse 312 from going around to the receiving side and destabilizing the cut point detection operation, the pulse applied to the start terminal of the timer circuit 162 is delayed or the identification output is set to the timer circuit 162. Needless to say, it is only necessary to delay the switching of the reception-side operation selector switch 157 to be sent to the stop terminal.

  From the detection result output terminal of the timer circuit 162, a half value of the measured time value is sent to the station side control circuit 161, and further to the operation support system 7 via the common control unit 5 of the station side transmission apparatus 10. Sent. An operator looks at the detection result of the optical fiber break point, and arranges the repair of the optical fiber.

  Here, it is assumed that a half of the measured time value is read from the detection result output terminal of the timer circuit 162, but there is no problem with the measured value of the timer itself as the value. It goes without saying that the conversion processing to the distance may be executed in the station side control circuit 161 or the common control unit 5 or the operation support system 7 of the station side transmission apparatus 10.

Single-core single-wavelength time-axis compression multiplex bidirectional optical transmission system (one-to-many connection: Figs. 1 and 6)
Next, when the transmission circuit of FIG. 1 is applied to the one-core single-wavelength time-axis compression one-to-multiple connection type optical branching bidirectional optical transmission system shown in FIG. An example will be described with reference to FIG. Note that the echo canceller system of FIG. 5 is not applied as in the conventional example.

  In this case, in consideration of the transmission distance (propagation delay time) between each ONU 201 and the OLT 101, a time window Tw for ensuring the operation of the furthest indoor ONU 201 is provided.

  As shown in FIG. 6, the all ONU operation guarantee window Tw needs a time longer than the time obtained by adding the protection time (Tg) to the propagation delay time corresponding to twice the farthest distance (Lmax).

  In other words, when an upstream signal disconnection from a specific ONU 201 is detected in the reception burst 1114 of the station-side OLT 101, it is determined that the fiber of the branch line fiber 302 is disconnected, and the operation of the station-side transceiver unit is changed from the normal operation to the disconnection point detection operation. Switch. At this time, at the start of the all ONU operation guarantee window Tw, an optical isolated pulse 312 is generated and sent to the optical fiber 301 toward all the in-home ONUs via the local optical coupler 13.

  That is, the isolated pulse generation circuit 112 generates a disconnection point detection isolated pulse from the burst frame pulse F shown in FIG. 12 and the transmission channel clock pulse of the bit stream shown in FIG. The driver circuit 121 sends the isolated pulse to the start terminal 162a of the timer circuit 162.

  The driver circuit 121 drives the light emitting element 122 with an isolated pulse to convert it into a light isolated pulse. This optically isolated pulse is sent to the optical fiber 30 through the local optical coupler 13.

  Then, as shown in FIG. 6, the transmitted light isolated pulse 312 is totally reflected at, for example, the cut point 303 (when the support fiber 302 is present) of the optical fiber 30, passes through the station-side optical coupler 13, and receives the station-side reception logic. It returns to the circuit unit 15 as a received light isolated pulse 314. The station-side reception logic circuit unit 15 is different from the normal operation state in that the equalization function is fixed to the maximum gain among the regenerative repeater functions (equalization amplification, timing extraction and identification function), and the identification function is normal. The reflected light isolation pulse is awaited at the threshold value (normally 0.5). That is, the light isolation pulse is extracted as an electrical signal by the preamplifier circuit 142 to the light receiving element 141. This electric signal is amplified by the equalization amplifier circuit 151 and applied to the identification circuit 153.

  Here, there is no problem if the equalization amplifier circuit 151 has a fixed gain. However, since the AGC (Automatic Gain Control) is normally operated, the gain of the equalization amplifier circuit 151 is switched in the cut point detection operation mode. The maximum gain is fixed by the switch 155.

  In the normal operation mode, the clock extracted from the received signal by the timing extraction circuit 152 is used as the clock of the identification circuit 153. However, in the disconnection point detection operation mode, the identification clock selector switch 156 is switched to set the transmission-side transmission path clock CP. Use.

  Here, in order to reliably identify the received isolated pulse by the transmission-side transmission path clock CP, the time width (connection time) of the transmitted isolated pulse is set to be twice or more than the reciprocal of the transmission-path clock frequency. That's fine.

  When the reception isolated pulse is identified by the identification circuit 153, the identification output is applied to the stop terminal 162b of the timer circuit 162 via the reception side operation changeover switch 157. The timer circuit 162 starts measurement when a pulse is applied to the start terminal 162a, and stops measurement when a pulse is applied to the stop terminal 162b.

  Here, in order to prevent the transmission light isolated pulse 312 from going around to the receiving side and destabilizing the cut point detection operation, the pulse applied to the start terminal 162a of the timer circuit 162 is delayed or the discrimination circuit 153 What is necessary is just to delay the switching timing of the reception side operation changeover switch 157 for sending the identification output to the stop terminal 162b of the timer circuit 162.

  From the detection result output terminal 162 c of the timer circuit 162, a half value of the measured time value is sent to the station side control circuit 161, and the operation support system 7 is further connected via the common control unit 5 of the station side transmission apparatus 10. Sent to.

  Then, if the value of this timer is divided by 2 and further divided by the propagation delay time per unit distance of the light in the optical fiber, the distance (L) from the station side transmission circuit to the cut point 303 of the optical fiber 30 is obtained. Can do. This timer clock may be dedicated to the timer, or the transmission line signal clock may be used as it is or after being divided or multiplied. The operator looks at the detection result of the optical fiber break point and arranges the repair of the optical fiber 30 for failure.

  Here, it is assumed that a half value of the measured time value is read from the detection result output terminal 162c of the timer circuit 162, but this value may be the measured value of the timer itself, and the optical fiber 30 is cut. It goes without saying that the conversion processing to the distance to the point 303 may be executed by the station side control circuit 161, the common control unit 5 of the station side transmission apparatus 10, or the operation support system 7.

  In the above-described embodiment, the control for switching the operation of the station side transmission circuit 1 from the normal operation to the cut point detection operation is performed from the outside manually or from the operation support system 7, but this is automatically performed in the station side transmission circuit 1. It may be done automatically.

  That is, when the station side control circuit 161 of the station side transmission circuit 1 receives an alarm output from the station side reception logic circuit 154 that the transmission signal is cut off, the station side control circuit 161 automatically switches from the normal operation to the same cut point detection operation as described above. .

  Then, the distance to the cutting point is measured in the timer circuit 162, and the result is transmitted to the common control unit 5 of the station side transmission apparatus 10 and the operation is switched back to the normal operation. Furthermore, the common control unit 5 of the station side transmission apparatus 10 autonomously sends the station side transmission circuit number (1 # 1 to 1 # N) where the failure is detected and the numerical value of the measurement result to the operation support system 7 in the form of a packet message. Notice.

  An example of this packet message is shown in FIG. 3, where “message number” indicates an identifier for identifying a message between the station-side transmission apparatus and the operation support system, and “transmission circuit number” is usually “building name”. , Floor, rack number, unit number, shelf number, package number, interface number "and the like.

  The “type” is a major alarm such as LOS (Loss Of Signal) or LOF (Loss Of Frame), performance information such as a bit error, or numerical data followed by the detection result of an optical fiber cut point. Indicates the type of “Numerical data” indicates specific numerical values such as the number of bit errors and numerical values of detection results of optical fiber break points.

  The operation support system 7 can identify the user's home from the user data and transmission circuit number of the database held, match the distance data to the failure point with the route diagram of the optical fiber cable, and specify the failure point.

  Note that switching between the normal operation mode and the cut point detection operation mode is the normal operation mode while the station-side OLT 101 is transmitting the downlink burst signal 1112 and while receiving the uplink burst signal 1114. Only the period of the ONU operation guarantee window Tw is switched to the cut point detection operation mode.

  In addition, since the optical isolation pulse used for fault point detection is within the operation guarantee window Tw, other ONUs that have not caused the branch fiber disconnection are not affected by this disconnection point detection operation, and perform normal service operation. There is no hindrance.

Further, the common control unit 5 of the station side transmission apparatus 10 autonomously notifies the operation support system in the form of a packet message of the station side transmission circuit number where the failure is detected and the numerical value of the measurement result. Is the same as that shown in FIG. 3, except that the ONU number is added to the end of the transmission circuit number.

It is the block diagram which showed the Example of the station side transmission circuit based on this invention. It is the block diagram which showed the connection relation of a station side transmission apparatus and an operation support system. It is the figure which showed the Example of the optical fiber cut point detection result notification message sent to an operation support system from a station side transmission apparatus by this invention. It is a figure explaining the optical isolation pulse between the station side at the time of the optical fiber cutting | disconnection in a optical transmission system (one-to-one connection type), and a cutting point. It is a block diagram showing an example of a station side transmission circuit of an echo canceller system . It is operation | movement explanatory drawing of the optical isolation pulse sent at the time of an optical fiber cut | disconnection by the optical transmission system (1 to many connection type) which concerns on this invention. It is a block diagram of a one-core identical wavelength time axis compression one-to-one connection type bidirectional optical transmission system known conventionally. FIG. 8 is an operation explanatory diagram during one burst period at the time of normal operation in the single-core single-wavelength time-axis compression multiplex bidirectional optical transmission system shown in FIG. 7. It is a block diagram of a conventionally known echo canceller bidirectional optical transmission system. It is explanatory drawing of the training operation | movement in the station side transmission circuit of the echo canceller bidirectional | two-way optical transmission system shown in FIG. 1 is a block diagram of a conventionally known single-core, single-wavelength time-axis compression one-to-multiple connection type optical branching bidirectional optical transmission system. FIG. It is operation | movement explanatory drawing when measuring the delay time of newly installed ONU in the 1 core same wavelength time-axis compression one-to-multiple connection type | formula optical branch bidirectional transmission system conventionally known. It is a figure for demonstrating the time-axis compression operation | movement in the 1 core same wavelength time-axis compression one-to-multiple connection type | formula optical branch bidirectional transmission system known conventionally. It is operation | movement explanatory drawing in 1 burst period at the time of normal operation | movement in the 1 core same wavelength time-axis compression one-to-multiple connection type | formula optical branching bidirectional optical transmission system conventionally known. It is a figure for demonstrating the delay time adjustment operation | movement in each ONU at the time of normal operation in the single core same wavelength time-axis compression one-to-multiple connection type optical branch bidirectional optical transmission system conventionally known.

Explanation of symbols

1 Station-side transmission circuit 2 Home-side transmission circuit 4 Multiplexing / demultiplexing unit 5 Common control unit 6 Information transfer network 7 Operation support system (OSS)
DESCRIPTION OF SYMBOLS 8 Input / output device 9 Optical fiber termination 10 Station side transmission apparatus 11 Station side transmission logic circuit part 12 Station side electrical / optical conversion circuit part 13 Station side optical coupler 14 Station side optical / electrical conversion circuit part 15 Station side reception Logic circuit section 16 Station-side control circuit section 17 Station-side echo canceller circuit section 18 Station-side subtractor 21 Home-side transmission logic circuit section 22 Home-side electrical / optical conversion circuit section 23 Home-side optical coupler 24 Home-side optical / electrical conversion Circuit unit 25 Home-side reception logic circuit unit 26 Home-side control circuit unit 27 Home-side echo canceller circuit unit 28 Home-side subtractor 30, 30 # 1 to 30 # N Optical fiber 31 Optical fiber cutting point 90 Optical connector 101 Station side OLT (Transmission Circuit)
111 Station side transmission logic circuit 112 Isolated pulse generation circuit 113 Transmission side operation changeover switch 121 Driver circuit 122 Light emitting element 141 Light receiving element 142 Preamplifier circuit 151 Equalization amplifier circuit 152 Timing extraction circuit 153 Identification circuit 154 Station side reception logic circuit 155 Gain switching switch 156 Identification clock switching switch 157 Reception side operation switching switch 161 Station side control circuit 162 Timer circuit 171 Station side echo canceller operation switching switch 201 Inside ONU (transmission circuit)
300 Optical branching device (1: N optical branching)
301 Core optical fiber in one-core single-wavelength one-to-multiple connection type time-axis compressed optical branching bidirectional optical transmission system 302 Branch optical fiber in one-to-multiple connection type optical branching bidirectional optical transmission system 312 Optical isolation transmitted from the station side Pulse 314 Received light isolated pulse 331 Cut off point of branch optical fiber 1112 Set of information time slots addressed to each ONU (downlink burst signal) transmitted from the station side in the one-to-many connection type optical branching bidirectional optical transmission system
1114 A set of information time slots (upstream burst signals) transmitted from each ONU received on the station side in the one-to-multiple connection type optical branching bidirectional optical transmission system
2112 Delay time measurement pulse train 2114 Delay time measurement response pulse train 3112 Training signal 3113 Training signal 3114 sent out to optical fiber Training signal reflected from optical fiber 3115 Training signal leaked at station side optical coupler 13 The same reference numerals indicate the same or corresponding parts.

Claims (6)

A single-core optical fiber is bidirectional at the same wavelength between the station-side transmission circuit and the premises transmission circuit in a one-to-many connection relationship in a one-to-many connection type optical branching time-axis compression multiplexed bidirectional optical transmission system. In a method of performing optical transmission,
A first step in which the station-side transmission circuit detects a corresponding home-side transmission circuit due to a response failure of the home-side transmission circuit;
An operation changeover switch provided in the station-side transmission circuit switches the input from the transmission logic circuit to the isolated pulse generation circuit based on the detected response fault, and the isolation switch toward the in-home transmission circuit corresponding to the response fault Based on the pulse from the pulse generation circuit, an optical isolated pulse having the same wavelength as that of the downstream burst signal is transmitted from the same light emitting element to the optical transmission line, thereby causing a failure based on the reflected isolated light pulse reflected in the optical transmission line. A second step of detecting the distance to the point ,
When the station side transmission circuit detects the response failure in any one of the premises transmission circuits in the first step, a burst signal in a predetermined downlink direction is transmitted in the second step. how burst signal is characterized by performing the distance detection of the light isolated pulse to the point of failure by the reflected light isolated pulse received by sending to the transmission line in operation guarantee time to come back up directly after. In claim 1,
該局side transmission circuit when it detects the response failure by the first step, when the result is notified to the operations support system, which received the switching instruction to the breakpoint detection operation from the normal operation from the operations support system And performing the second step . A single-core optical fiber is bidirectional at the same wavelength between the station-side transmission circuit and the premises transmission circuit in a one-to-many connection relationship in a one-to-many connection type optical branching time-axis compression multiplexed bidirectional optical transmission system. In a system that performs optical transmission,
The station-side transmission circuit detects a corresponding house-inside transmission circuit due to a response failure in the house-inside transmission circuit, and an operation changeover switch provided in the station-side transmission circuit transmits a transmission logic based on the detected response failure. The circuit switches the input from the circuit to the isolated pulse generation circuit and transmits the optical isolated pulse having the same wavelength as the downlink burst signal from the same light emitting element to the in-home transmission circuit corresponding to the response failure based on the pulse from the isolated pulse generation circuit. A distance to the fault point is detected based on the reflected light isolated pulse reflected and received in the optical transmission line by being sent to the optical transmission line, and the station side transmission circuit is connected to any of the in-house transmission circuits. A system characterized in that the response failure is detected for one of them, and the optical isolated pulse is sent to a transmission line within a predetermined operation guarantee time to detect the distance to the failure point . In claim 3,
When the response fault is detected, the station side transmission circuit notifies the operation support system of the result, and when receiving a switching instruction from the normal operation to the disconnection point detection operation from the operation support system, up to the fault point. A system characterized by performing distance detection. Station side that performs one-to-many connection type optical branching time axis compression multiplexed bi-directional optical transmission at the same wavelength to a home-side transmission circuit that has a one-to-many connection relationship with the station-side transmission circuit using a single-core optical fiber In the transmission circuit of
An operation switching switch provided in the station-side transmission circuit switches the input from the transmission logic circuit to the isolated pulse generation circuit based on the detected response fault and responds to the response fault of the home-side transmission circuit A first means for detecting
The optical transmission by transmitting an optical isolated pulse having the same wavelength as the downlink burst signal from the same light emitting element to the optical transmission line based on the pulse from the isolated pulse generating circuit toward the in-home transmission circuit corresponding to the response failure A second means for detecting a distance to the obstacle point based on the reflected light isolated pulse reflected and received in the road,
The first means detects the response failure in any one of the in- house transmission circuits, and the second means sends the optical isolated pulse to the transmission line within a predetermined operation guarantee time. A transmission circuit characterized by detecting the distance to the point of failure. In claim 5 ,
The first means, when detecting the response fault, and notifies the result to the operations support system, when receiving a switching instruction to the breakpoint detection operation from the normal operation from the operations support system, the second means A transmission circuit characterized by detecting the distance to the point of failure.

Images