WO2004010612A1

WO2004010612A1 - Optical transmission method and system

Info

Publication number: WO2004010612A1
Application number: PCT/JP2002/007427
Authority: WO
Inventors: Kazumitsu Maki; Haruo Yamashita
Original assignee: Fujitsu Limited
Priority date: 2002-07-23
Filing date: 2002-07-23
Publication date: 2004-01-29
Also published as: JPWO2004010612A1; JP4044558B2

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

Specification

Optical transmission method and system

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

2. Description of the Related Art Conventionally, when bidirectional transmission is performed in an optical transmission system, transmission and reception are generally performed using a two-core optical fiber. In order to increase the transmission capacity of optical fibers, WDM (wavelength division multiplexing) transmission may be performed in each of the upstream and downstream directions.

On the other hand, in an access system that connects a telecommunications carrier's office (station side) and a user's house (inside the house), it is economical if bidirectional transmission can be performed using a single-core optical fiber because of the large number. As a single-core bidirectional optical transmission system, there is a WDM bidirectional transmission system that uses different wavelengths for upstream and downstream.However, it is necessary to prepare light-emitting elements with different wavelengths, and it depends on the wavelength division multiplexer. There is an economic limit, such as the need to have the property. In addition, since wavelength is the same valuable resource as radio waves, it is desirable that one service can be transmitted bidirectionally with one wavelength.

Such single-wavelength bidirectional transmission systems with the same wavelength include a time-axis compression multiplexed bidirectional optical transmission system and an echo canceller bidirectional optical transmission system, both of which operate on the same principle as the case of metallic transmission. .

1-core same-wavelength bidirectional transmission system (one-to-one connection: Fig. 7)

Here, the operation of the former one-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 method is described in detail in the document “Multimedia Network Series Digital Access Method” (Ohm) and will not be described here.

First, the station-side transmission circuit 1 and the home-side transmission circuit 2 face each other via the optical fiber 30. The information transmitted from the office-side transmission circuit 1 to the home-side transmission circuit 2 is transmitted to the office-side transmission logic circuit. The signal is time-axis-compressed by the unit 11, converted into an optical pulse by the station-side electric / optical conversion circuit unit 12, and sent to the optical fiber 30 via the station-side optical 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 converted back to an electrical signal in the in-home optical / electrical conversion circuit 24, which is further received in the in-home. The logic circuit section 25 expands the time axis to extract the original speed information.

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

Further, the station side control circuit section 16 generates a control signal and the like necessary for time axis operation from a clock pulse in the station. In addition, the inside control circuit unit 26 extracts quick information necessary for time axis operation from the received pulse train, and generates necessary control signals and the like.

Next, transmission and reception of a transmission signal between the station side transmission circuit 1 and the home side transmission circuit 2 during normal operation will be described with reference to FIG.

First, the downstream burst signal 1 1 1 2 transmitted from the station side transmission circuit 1 is received by the inside transmission circuit 2 after receiving the attenuation due to the loss in the optical fiber 30 and the propagation delay time (Tps). After receiving the downstream burst signal 1 1 1 2, the in-home transmission circuit 2 transmits the upstream burst signal 1 1 1 4 after a protection time (Tg) for preventing interference between upstream and downstream. The upstream burst signal 111 is received by the station side transmission circuit 1 after receiving the attenuation due to the loss in the optical fiber 30 and the propagation delay time (Tpr).

Here, the occupation time (Tis) of the downstream burst signal 1 1 1 and the occupancy time (Tir) of the upstream burst signal are equal. Also, the downstream propagation delay time (Tps) and the upstream propagation delay time (Tpr) are equal. Up 'occupation time of the downlink Pasuto signal (Tis, Tir) and uplink' becomes the downlink propagation delay time between (Tps, Tpr) and guard time (T _g) the sum of Pasuto 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. The office side echo canceller circuit section 7 and the office side subtracter 18 are provided, and the in-home transmission circuit 2 includes an in-home echo canceller circuit section 27 and an in-home subtractor 28.

The principle of the echo canceller two-way transmission method is also described in the above-mentioned document “Multimedia Network Series Digital Access Method” (Ohm), and will not be described here.

First, the station-side transmission circuit 1 and the home-side transmission circuit 2 face each other via the optical fiber 30. The information transmitted from the station side to the inside of the house is added with a frame synchronization signal and the like by the station side transmission logic circuit section 11, becomes an optical pulse by the station side electric / optical conversion circuit section 12, and becomes the station side optical coupler 1 It is sent to the optical fiber 30 via 3. At the inside of the house, the received optical pulse is guided from the optical fiber 30 through the inside optical coupler 23 to the inside-home optical / electrical conversion circuit section 24, and the frame synchronization signal is processed by the inside reception logic circuit section 25. And then retrieve the original information. When transmitting information from the inside of the house to the station in the opposite direction, a frame synchronization signal and the like are added by the inside-of-house transmission logic circuit 21 and are converted into optical pulses by the inside-of-house electrical-optical conversion circuit 22. The light is sent to the optical fiber 30 via the optical coupler 23. At 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 section 14, and the frame-side synchronization signal is sent to the station-side reception logic circuit section 15. After performing the above processing, extract the original information.

The above operation is the same as that of the time axis compression multiplexed bidirectional optical transmission system shown in Fig. 7, except that in the echo canceller bidirectional optical transmission system, during the information transfer, the data goes up on the optical fiber 30 and goes down in the Z direction. The point that transmission signals are continuously and simultaneously mixed is different from the time axis multiplexed bidirectional optical transmission method.

Here, the operation of the echo canceller method will be described with reference to FIG. The station-side echo canceller 17 performs a trace when starting communication. The training signal 3 1 1 2 from the station side transmission logic circuit section 11 is transmitted as an optical signal 3 11 3 to the optical fiber 30 via the station side optical coupler 13.

The sum of the reflection signal 3 1 1 4 of the training signal 3 1 1 3 transmitted to the optical fiber 3 0 and the training signal 3 1 1 5 leaked by the optical coupler 13 at the station is the optical-to-electrical conversion at the station. The signal is input to the circuit section 14 and converted into an electric signal.

The station-side echo canceller 17 based on the station-side training signal 3 1 1 2 Set its own operating parameters to generate a signal (called an echo signal) that cancels out the sum signal of the leakage signal 311 and the reflection signal 311 from the optical fiber. I do.

During normal operation, upstream and downstream transmission signals continuously and simultaneously flow on the optical fiber 30, but the station side subtractor 18 receives a signal from the station side optical / electrical conversion circuit section 14 from the inside of the house. The leaked signal of the received signal and 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 reception logic circuit 15. Since the operation of the echo canceller inside the house is the same, the description is omitted.

The station-side control circuit 16 generates necessary control signals such as a frame synchronization signal from the station-side terminal SCK. In addition, the inside 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 restrictions due to optical fiber loss. This will be described later.

In the former time-axis compression multiplex bidirectional optical transmission method, the upstream / downstream signals are separated in time, so that the optical coupler is simpler, but the transmission signal speed is lower than the information speed. More than twice as necessary.

Also, in the latter echo canceller bidirectional optical transmission system, the transmission signal speed is almost the same as the information speed, but a directional coupler must be used for the optical coupler to improve the separation between uplink and downlink. .

One-core same-wavelength time-axis compression multiplexed bidirectional optical transmission system (one-to-many connection -.mil)

The time-axis compression multiplexed bidirectional optical transmission system as a single-core bidirectional transmission system with the same wavelength is an economical single-core bidirectional optical transmission system in which multiple users share an optical fiber and information band using an optical branching device. It is applied to the same wavelength one-to-many connection type optical branching bidirectional optical transmission system.

The operation of the one-core, same-wavelength, one-to-multi-connection optical branching bidirectional optical transmission system will be described with reference to FIG. It should be noted that the above echo canceller bidirectional optical transmission system is not applied to this transmission system.

This single-core, one-wavelength, one-to-many connection optical branching bidirectional optical transmission system uses PON (Passive PT / JP2002 / 007427

This is a type of optical transmission system called an “optical network” system. The PON system is detailed in, for example, the document “xDS L / FTTH” (ASCII Press Office), and thus description thereof is omitted here.

In this one-core one-wavelength one-to-many connection type optical branching bidirectional optical transmission system, an optical transmission line termination circuit (hereinafter referred to as an OLT (Optical Line Termination circuit)) corresponding to the above-mentioned station-side transmission circuit 1 10. 1 and an optical network unit (hereinafter referred to as ONU (Optical Network Unit)) 201 corresponding to the in-home transmission circuit 2 are connected in a 1: N connection via an optical branching device 300. Here, N is an integer indicating the number of connected ONU.

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

On the other hand, the upstream direction from each ONU 201 to the OLT 101 is transferred in units of a predetermined time slot specified by the OLT 101. That is, as shown in FIG. 12, in the burst period Tb, the time taken for the downlink burst signal 1 1 1 2 to return at the station side —LT 101 —home side ONU 201 —station side OLT 101 is the entire time. As the ONU operation security window Tw, the optical pulse 21 12 for delay time measurement is sent from the OLT 101 to the new ONU 201 1 inside the new home, and the delay time Ta unique to the ONU 201 1 inside the home is measured. deep. Then, a time slot Tsl is allocated to the existing ONU 2012 and a time slot Ts2 is allocated to the new ONU 2011 to transmit a burst signal.

As described above, when the new ONU 201 1 is installed while the existing ONU 201 2 is operating, the information that `` unassigned time slots should be answered by ONUs '' in the ONU operation guarantee window Tw from the station side LT 101 is included. The pulse train 21 12 for delay time measurement is transmitted by broadcast. Upon receiving this, the new ONU 201 1 returns a response pulse train 2 114 including its own ID information.

When the OLT 101 receives the response from the newly established ONU 201 1, the delay time T a And transmit the designated time slot and delay adjustment time T d to the new ONU 2011 in the frame information F.

The pulse train for delay time measurement 2112 can be inserted in every burst period, and a certain line can be inserted once every few seconds, and even when an ONU is newly established, it can be inserted by an external instruction. You can also.

The newly installed ONU 201 1 reads out its 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 LT 101, and sends it from the station OLT 101 in the form of a broadcast. Only the information of the specified time slot Ts2 is received from the incoming information sequence.

The new ONU 201 1 sets the transmission timing to the OLT 101 on the station side as the protection time Tg (fixed value), the delay adjustment time Td (depending on the distance between the ONU and OLT), and the time slot position designation time Tt (for each ONU). Different) and sends the information to the specified 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 the decompression operation in the transmission of information transmitted from the station side to the house side and information in the opposite 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 LT 101 is compressed on the time axis at every noast period (Tb), put into, for example, the time slot Tsl in the signal 1112, and sent to the ONU 201 on the home side. The bit stream compressed in the time axis of the time slot Tsl is expanded in the time axis by the in-house ONU 201 to return to the original speed, and is used as the bit stream of the in-house received 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 inside-inside information.

The difference between the single-core time axis compression multiplexed bidirectional optical transmission system and the one-to-many connection type optical branching bidirectional optical system based on the PON system is that the upstream information from each connected ONU 201 is transmitted to the optical branching device station. This means that TDMA (Time Domain Multiple Access) control is performed to prevent information from being corrupted due to collisions on the side.

From each ONU 2012, 2011 1 sent to OLT 101 (see Fig. 12) The information time slots Tsl and Ts2 (see Fig. 12) are transmitted at a predetermined timing based on the transmission delay time instruction from the OLT 101. In the OLT 101, the information time slots Tsl and Ts2 from the ONU Be identified.

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

The downstream burst signal 11 12 transmitted from the OLT 101 at the station is data containing information time slots addressed to each ONU 201, and receives the attenuation due to loss and propagation delay time (Tps) in the optical fiber. Received at k.

At this time, the data received by each ONU 201 has different attenuation and propagation delay time according to the distance from the OLT 101. The on-premises ONU 201 extracts the information time slot addressed to the ONU # k from the downlink burst signal 11 12, and upon completion of reception, sets the uplink time from each ONU 201 during the protection time (Tg) to prevent uplink and downlink interference. After waiting for the time added with the delay adjustment time (Td) to avoid information collision, the information is transferred to the time slot Ts # k specified by the OLT 101 in the time slot of the upstream burst signal 1114. Send. This upstream burst signal 1114 is received by the station side after receiving attenuation due to loss and propagation delay time (Tpr) in the optical fiber 30.

Here, the upstream burst signal 1114 received by the station side ΔLT 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 11 and 12 is equal to the occupation time (Tir) of the uplink burst signal. Also, the downstream propagation delay time (Tps) and the upstream propagation delay time (Tpr) are equal for each ONU 201, but different ONU 201s have different distances from OLT 101, so the values differ for each ONU 201. .

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

In the one-core same-wavelength one-to-many connection type optical branching bidirectional optical transmission system, there is a maximum applicable distance (Lmax) as the system. This maximum distance is used to determine the delay time that each ONU 201 adjusts to be logically equidistant from the OLT 101. That is, in order to avoid collision of the upstream burst signal 1114 from each ONU 201 and thereby guarantee the operation of all ONUs, each ONU 201 sends out so that all ONUs 201 are at the logical distance of Lmax. Information time slot delay time adjust.

This delay time adjustment mechanism will be described with reference to FIG. In this figure, two home interior 宅 NUs, a home interior O NU # j and an ONU # k, are connected. For the delay adjustment time, the OLT 101 on the station measures the transmission path distance to each ONU 201 inside the house, and based on the measurement result, the OLT 101 on the station notifies each ONU 201 inside the house.

At this time, the delay adjustment time Tdi for the ONU # i inside the house is set so that the following relationship is established between the propagation delay time Tpi corresponding to the transmission distance Li and the maximum propagation time Tpmax corresponding to the maximum applicable distance Lmax. I can decide.

2Tpi + Tg + Tdi = 2Tpmax + TgEquation (1)

= Constant value

Where Tg is the protection time.

Optical fiber cutting failure

On the other hand, when an optical fiber disconnection failure occurs in all the above transmission methods, that is, one-core bidirectional optical transmission method with the same wavelength, 切断 TDR (Optical Time Domain Keflectometer) Detection was being performed.

In other words, in this ΔTDR, in order to accurately detect the cut point of the optical fiber, the Fresnel reflected light and the backscattered light of the measurement light pulse were received, the integration operation was performed, and the display was displayed on the display.

Although such a method is excellent in detecting a failure point with high accuracy, the ability to replace an optical connector with a terminal of an optical termination of a failed optical fiber and to connect the optical fiber to a known optical line maintenance. Measuring instruments must be connected via optical splitters and optical switches, as in a support system.

For this reason, when replacing optical connectors, it is necessary to identify the terminal of the optical fiber that has failed out of a large number of optical termination terminals and connect the measuring instrument. There is a disadvantage that it is not possible to prevent accidentally connecting the measuring instrument to a normal optical fiber due to a mistake.

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

Furthermore, it is different from the wavelength for transmitting information for the conventional optical fiber break point detection. It is necessary to use a dedicated wavelength for measurement, and it is difficult to incorporate the measurement function into the optical transceiver circuit because the circuit scale becomes large.

In the conventional optical fiber cutting point detection work, when a fault occurs, the operator manually instructs the optical fiber termination to connect the measuring instrument manually, and controls the optical switch according to the instruction from the operation support system. It was started by connecting to the system, and in each case, operator intervention was required.

Also, in the same wavelength one-to-many connection type optical branching bidirectional optical transmission system, it is possible to detect the breakpoint of the trunk fiber from the station side transmission circuit to the optical branching device using OTDR, but the optical branching device In the detection of a break point in a branch fiber connected to the user's home, it was difficult to identify which branch fiber failed because the test light pulse was split and multiple reflected.

Further, in the past, the optical transmission device and the measuring device for detecting the optical fiber cutting point were completely different, and there was no integrated device.

Accordingly, the present invention relates to a method and system for performing bidirectional optical transmission at the same wavelength between an office-side transmission circuit and a home-side transmission circuit by using a single-core optical fiber, wherein a special measuring device is connected to detect an optical fiber disconnection fault. The purpose is to be able to automatically detect without detecting. Disclosure of the invention

In the present invention, the fault point detection of the optical fiber is limited to the detection of the break point, and the operation of the station side transmission circuit is measured from the normal operation to the time from the transmission of the isolated pulse for measuring the fiber cut point to the reception. This is realized by switching to a cutting point detection operation.

Therefore, in the optical transmission method according to the present invention, the station-side transmission circuit detects the corresponding home-side transmission circuit based on the response fault of the home-side transmission circuit, and the station-side transmission circuit detects the response fault. And a second step of detecting a fault point by transmitting an optically isolated pulse toward the in-home transmission circuit corresponding to.

In other words, if a failure occurs, such as when the optical fiber that is the transmission medium is cut, for example, it will not be possible to respond from the inside of the house, and the upstream side transmission circuit will not be able to receive the upstream signal from the inside house transmission circuit. become. In such cases, conventionally, the station-side transmission circuit generates a response failure alarm, and at the instruction of the operator, carries a measuring device called an OTDR in front of the optical fiber termination, causing a failure. The measurement was performed by replacing the optical connector with an optical fiber that was thought to have been accessed.

Also, when a measuring instrument was connected via an optical splitter and an optical switch, the operation of the optical switch was performed from an operation support system, and measurement was performed to detect a cutting point.

On the other hand, according to 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 the normal operation to the failure point detection operation. By transmitting an optically isolated pulse to the home-side transmission circuit related to the response failure, the distance to the failure point can be measured (second step).

As described above, according to the present invention, when an optical fiber disconnection failure occurs in the single-core same-wavelength two-way transmission system, the disconnection point can be detected in the transmission circuit without using the OTDR. For this reason, it is not necessary to replace the optical connector and connect the measuring instrument, which reduces the number of measurement operations, and also allows the measuring instrument to be accidentally connected to a normal optical fiber due to human error. Can be prevented. Also, large-scale equipment for connecting the measuring instrument via the optical splitter and the optical switch is not required.

Furthermore, it is not necessary to use a wavelength dedicated to measurement for detecting an optical fiber break point, and it is sufficient to use the wavelength for transmitting information itself, so that a measurement function can be incorporated into an optical transceiver circuit with a slight increase in circuit size. .

In the above case, when the station-side transmission circuit and the home-side transmission circuit have a one-to-one connection relationship as shown in FIGS. 7 and 9, the station-side transmission circuit performs the home step in the first step. When the response fault of the inner transmission circuit is detected, the optical isolated pulse is sent to the home transmission circuit in the second step to detect a fault point.

On the other hand, in the point-to-multipoint connection type optical branching bidirectional optical transmission system, when the station-side transmission circuit and the home-side transmission circuit have a one-to-many connection relationship as shown in FIG. The circuit, when detecting the response failure for any one of the home inside transmission circuits in the first step, in the second step, the optical isolated pulse is detected within a predetermined operation guarantee time. The signal is sent to the transmission path to detect a fault point. That is, the station-side transmission circuit operates within the time to guarantee the operation of the ONU inside the entire house until the burst signal 1 1 1 2 shown in FIGS. 12 and 13 is transmitted from the station-side OLT and returned. An optical isolated pulse is sent to ONU inside each house to detect the harmful points in Chapter P.

To explain this more specifically, if a response failure occurs on the optical fiber, which is the transmission medium, when the backbone fiber of the optical branching device is cut off, communication cannot be attempted from the entire home inner transmission circuit ONU. However, from the point of view of the station, even if an attempt is made to communicate, it becomes impossible to receive the uplink burst signal from the house side.

In addition, when a branch fiber fault occurs, an uplink burst signal (information time slot from the relevant home ONU) from the relevant home ONU cannot be received. Therefore, when the branch fiber is cut, an alarm is generated in the OLT on the station side as out of synchronization with the received frame or as a time slot not received from the ONU.

Conventionally, when this condition is reached, a measuring instrument called an OTDR is carried in front of the optical fiber termination by an operator's instruction, and the optical fiber that seems to have failed is replaced by an optical connector and accessed for measurement. I was doing. In addition, when the measuring instrument was connected via an optical splitter and an optical switch, the operation support system operated the optical switch and performed measurement to detect a cutting point.

However, as described above, in this method, the breakpoint of the trunk fiber from the station-side transmission circuit to the optical branching device can be detected using OTDR, but a branch line connected from the optical branching device to each user's home. Since the test light pulse is split and multiple-reflected to detect the break point in the fiber, it was difficult to specify which branch fiber failed.

According to the present invention, when a failure occurs in which the optical fiber is cut, the operation of the optical line termination circuit on the optical line at the station side is automatically switched from the normal operation to the operation of detecting the disconnection point. The distance to the cutting point can be measured.

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

If a response failure occurs, the result is reported to the operation support system. The operation support system receives the notification and instructs the station-side transmission circuit to switch the station-side transmission circuit from the normal operation to the disconnection point detection operation. Distance can also be measured.

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

As a system for realizing the optical transmission method according to the present invention, the station-side transmission circuit detects a corresponding in-home transmission circuit based on a response failure of the in-home transmission circuit, and transmits the in-home transmission corresponding to the response failure. There is provided a system characterized in that a fault point is detected by transmitting an optical isolated pulse toward a circuit.

In the point-to-multipoint connection type optical branching bidirectional optical transmission system, when the station-side transmission circuit and the home-side transmission circuit have a one-to-many connection relationship, the station-side transmission circuit includes the home-side transmission circuit. When the response failure is detected for any one of the transmission circuits, the optical isolated pulse can be transmitted to the transmission line within a predetermined operation failure time to detect a failure point. Further, in the above system, when detecting 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 disconnection point detection operation from the operation support system. In this case, the fault check can be performed.

Further, in the present invention, in the transmission circuit on the station side that performs bidirectional optical transmission at the same wavelength to the in-home transmission circuit using a single-core optical fiber, the in-home transmission circuit corresponding to the response failure of the in-home transmission circuit is provided. A transmission circuit, comprising: first means for detecting; and second means for detecting a point of failure by transmitting an optical isolated pulse to a home-side transmission circuit corresponding to the response failure. Is done.

In the above-described transmission circuit of the one-to-many connection type optical branching bidirectional optical transmission system, when the station-side transmission circuit and the home-side transmission circuit have a one-to-many connection relationship, When the response failure is detected in any one of the side transmission circuits, the second means transmits the optical isolated pulse to the transmission path within a predetermined operation guarantee time to perform a failure point detection. Can be.

In the above transmission circuit, the first means, when detecting the response failure, The second means can detect a failure point when the operation support system notifies the operation support system of the result and when the operation support system receives an instruction to switch from the normal operation to the disconnection point detection operation.

Further, in the above method, system, and transmission circuit, the bidirectional optical transmission can be performed by time-axis compression multiplexing or an echo canceller method. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram showing an embodiment of a station-side transmission circuit according to the present invention.

FIG. 2 is a block diagram showing a connection relationship between the station-side transmission device and the operation support system.

FIG. 3 is a diagram showing an embodiment of an optical fiber cutting point detection result notification message sent from the station side transmission device to the operation support system according to the present invention.

FIG. 4 is a diagram for explaining an optical isolated pulse between a station side and a cutting point when an optical fiber is cut in the optical transmission system (one-to-one connection type) according to the present invention.

FIG. 5 is a block diagram showing another embodiment (echo canceller system) of the station side transmission circuit according to the present invention.

FIG. 6 is an explanatory diagram of an operation of an optical isolated pulse transmitted when an optical fiber is cut by the optical transmission system (one-to-many connection type) according to the present invention.

FIG. 7 is a block diagram of a conventionally known one-core one-wavelength time-axis compression one-to-one connection type bidirectional optical transmission system.

FIG. 8 is an explanatory diagram of an operation during one burst period in a normal operation in the one-core same-wavelength time-axis compression multiplexed bidirectional optical transmission system shown in FIG.

FIG. 9 is a block diagram of a conventionally known echo canceller bidirectional optical transmission system.

FIG. 10 is an explanatory diagram of a training operation in the station-side transmission circuit of the echo canceller bidirectional optical transmission system shown in FIG.

FIG. 11 is a block diagram of a conventionally known one-core one-wavelength, time-axis-compressed, one-to-many-connection optical branching bidirectional optical transmission system.

Figure 12 shows the conventional single-core, same-wavelength, time-axis compression, one-to-many FIG. 9 is an explanatory diagram of the operation when measuring the delay time of a newly installed ONU in the directional transmission system.

FIG. 13 is a diagram for explaining a time axis compression operation in a conventionally known one-core one-wavelength time-axis compression one-to-many-connection type optical branching bidirectional transmission system.

FIG. 14 is a diagram illustrating the operation during one burst period during normal operation in a conventionally known one-core one-wavelength, time-axis-compressed, one-to-many-connection type optical branching bidirectional optical transmission system. Fig. 15 is a diagram for explaining the delay time adjustment operation at each ONU during normal operation in a conventionally known one-core one-wavelength, time-axis-compressed, one-to-many-connection optical branching bidirectional optical transmission system. FIG.

Explanation of reference numerals

1 Station side transmission circuit

2 In-house transmission circuit

4 Multiplexing / separating unit

5 Common control unit

6 Information transfer network

7 Operation support system (〇S S)

8-person output device

9 Optical fiber termination

1 0 Station side transmission device

1 1 Station side transmission logic

1 2 Station side electrical / optical conversion circuit

1 3 Optical coupler

1 4 Station optical / electrical conversion circuit

15 Station side reception logic circuit

16 Station side control circuit

17 Station echo canceller circuit

1 8 Station side subtractor

2 1 In-home transmission logic

2 2 Electricity inside the house 23 In-home optical coupler

24 Light inside the house

25 In-home receiving logic

26 Residential control circuit

27 In-home echo canceller circuit

28 Home Subtractor

30, 30 # 1 ~ 30 # N Optical fiber

31 Optical Fiber Cutting Point

90 Optical Connector

101 station side OLT (transmission circuit)

1 11 Station side transmission logic

112 Isolated pulse generator

1 13 Transmitter operation 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 receiving logic

155 Gain switch

156 Identification clock switch

157 Reception-side operation switch

161 Station side control circuit

162 Timer circuit

171 Station-side echo canceler operation switching switch

201 ONU inside the house (transmission circuit)

300 light splitting device (1: N light splitting) 301 One-core same wavelength One-to-many connection time-base compressed optical branching main optical fiber in bidirectional optical transmission system

302 Branch optical fiber in one-to-many connection optical branching bidirectional optical transmission system

312 Optical isolated pulse transmitted from station side

314 Received light isolated pulse

331 Cutting point of branch fiber

11 12 A set of information time slots transmitted from the station side to each ONU in the one-to-many connection optical branching bidirectional optical transmission system (downstream burst signal)

11 14 A set of information time slots transmitted from each ONU received at the station side in the one-to-many connection optical branching bidirectional optical transmission system (uplink burst signal)

21 12 Pulse train for delay time measurement

21 14 Delay time measurement response pulse train

31 12 Training signal

31 13 Training signal sent to optical fiber

3114 Training signal reflected from optical fiber

31 15 Training signal leaked from optical coupler 13 at station

In the drawings, the same reference numerals indicate the same or corresponding parts. BEST MODE FOR CARRYING OUT THE INVENTION

1-core same-wavelength bidirectional transmission system (one-to-one connection: Figures 1 and 7)

FIG. 1 shows an embodiment of a station-side transmission circuit according to the single-core same-wavelength time-axis compression multiplex bidirectional optical transmission system according to the present invention. In this embodiment, in the conventional example shown in FIG. 7, the station-side transmission logic circuit section 11 is composed of a station-side transmission logic circuit 111, an isolated pulse generation circuit 112, and a transmission-side operation switching switch 113. The circuit section 16 is composed of a station side control circuit 161 and a timer circuit 162, and the station side reception logic circuit section 15 is an equalization amplifier circuit 151, a timing extraction circuit 152, an identification circuit 153, a station side reception logic circuit 154, and a gain. It is characterized by comprising a switching switch 155, an identification clock switching switch 156, and a receiving-side operation switching switch 157.

It is to be noted that the station-side electric / optical conversion circuit section 12 includes a driver circuit 121 and a light emitting element 122. This is the same as the above-described conventional example in that the optical-to-electrical conversion circuit section 14 on the station side comprises a light receiving element 14 1 and a preamplifier circuit 14 2.

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 located on the opposite side of the figure. That is, the station-side transmission logic circuit 111 is connected to the station-side electrical-optical conversion circuit section 12, the switch 155 is connected to the variable gain terminal G2, and the timing extraction circuit 155 is an identification circuit 155. 3 and the identification circuit 15 3 is connected to the station-side reception logic circuit 15 4.

FIG. 2 shows a connection relationship between the station-side transmission device 10 and the operation support system 7. In general, one station-side transmission device 10 has a plurality of station-side transmission circuits 1 shown in FIG. As 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 each station side transmission circuit 1 # 1 to 1 #N and the setting control for each station side transmission circuit 1 are collected by the common control unit 5 of the station side transmission device 10, and are configured with LAN, etc. It communicates with the operation support system (OSS) 7 via the information transfer network 6. Normally, communication between the operation support system and the transmission device is performed in the form of a packet message shown in Fig. 3.

The operation support system 7 has an input / output device 8 which controls a human machine interface with an operator. A personal computer or a workstation is usually used for the input / output device 8. The optical fiber 30 # 1 to 30 # N from each station side transmission circuit 1 is connected to an optical fiber extending to the user's home by an optical fiber termination frame 9 via an optical connector 90, where the inside of the station is connected. And failure outside the station.

Needless to say, in order to more reliably detect the disconnection point, the light emission pulse of the optically isolated pulse sent from the station side transmission circuit should be twice or more than the light emission pulse in normal operation. No. Needless to say, in order to accurately determine the distance to the cutting point, it is only necessary to perform multiple measurements and average the values. When the disconnection state of the received signal is detected by the station-side reception logic circuit 154, an alarm is issued from the station-side control circuit 161 via the common control unit 5 of the station-side transmission device 10. Tell system 7 The operator of the operation support system 7 refers to the alarm and issues an instruction to the corresponding station side transmission circuit 1 to switch from the normal operation to the disconnection point detection operation.

In the station side control circuit 16 1, when an instruction from the operation support system 7 is received, the transmission side operation switch 1 13, the gain switch 1 55, the identification clock switch 1 56, and the reception side operation switch Switch 157 to the cutting point detection operation mode shown in Fig. 1.

When the operation of the station side transmission circuit 1 is switched to the break point detection operation, the station side transmission logic circuit section 11 propagates an optical signal equivalent to twice the maximum applicable distance (Lmax) as shown in Fig. 4. An isolated pulse is generated with a period longer than the time (Tmax), and the isolated pulse becomes an optical isolated pulse 3 1 2 in the optical-to-optical conversion circuit section 12 on the station side. Sent to 30.

As shown in the figure, the optically isolated path 312 propagates through the optical fiber 30 from the station side to the home side while being attenuated due to optical loss, and is almost totally reflected at the cutoff point 31 of the optical fiber. Then come back to the station. The reflected light isolated pulse 3 14 received via the optical coupler 13 on the station side is converted into an electric signal by the optical-to-electrical conversion circuit section 14 on the station side and input to the receiving logic circuit section 15 on the station side. .

In the disconnection point detection operation, the station side reception logic circuit section 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 at the normal threshold (normally 0.5).

The station-side control circuit 16 starts a timer for counting the time from the point at which the above-mentioned isolated panel was generated by the station-side transmission logic circuit 11, and the received reflected light isolated pulse 3 1 4 has an identification function. The timer circuit 16 2 is stopped at the time when it is determined that there is a timer. Dividing the value of this timer by 2 and dividing by the propagation delay time per unit distance of the light in the optical fiber gives the distance (L) from the optical line end to the cutting point of the optical fiber. The clock for the timer may be used exclusively for the timer, or may be used by dividing or multiplying the clock CP of the transmission line signal as it is.

Echo canceller two-way optical transmission system (one-to-one connection: Figures 5 and 9) FIG. 5 shows an embodiment of a station side transmission circuit using the echo canceller bidirectional optical transmission system according to the present invention.

In this embodiment, in the conventional example of FIG. 9, the station side transmission logic circuit section 11 is composed of the station side transmission logic circuit section 111, the isolated pulse generation circuit 112, and the transmission side operation switching switch 113. The station side control circuit section 16 is composed of a station side control circuit 16 1 and a timer circuit 16 2, and the station side reception logic circuit section 15 is an equalizing amplifier circuit 15 1 and a timing extraction circuit 1 5 2, an identification circuit 15 3, a station-side reception logic circuit 15 4, a gain switching switch 15 5, an identification clock switching switch 15 6, and a reception-side operation switching switch 15 7, and It is characterized in that a station side echo canceller operation switching switch 17 1 is added to the station side echo canceller circuit section 17.

The station-side electrical / optical conversion circuit 12 is composed of a driver circuit 12 1 and a light emitting element 122, and the station-side optical / electrical conversion circuit 14 is comprised of a light receiving element 14 1 and a preamplifier circuit. The point composed of 1 and 2 is the same as the conventional one.

Next, the operation of this embodiment will be described.

The operation of detecting the disconnection point 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 switching switch 1 13, the gain switching switch 15 5, the identification clock switching switch 15 6, the reception-side operation switching switch 15 7 Has been switched to the cutting point detection operation mode, and in the normal operation mode, each switch is switched to the opposite side.

In other words, when the disconnection of the received signal 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 O S S sees the alarm and issues an instruction to the corresponding station side transmission circuit 1 to switch from the normal operation to the cut point detection operation shown in the figure.

In the station side control circuit 16 1, when an instruction is received from the operation support system 7, the transmitting side operation switching switch 13, the gain switching switch 15 5, the identification switch 15 6, the receiving side operation Selector switch 157 and station side echo canceler operation changeover switch 171 Switch to cut-point detection operation mode.

Isolated pulse generation circuit 1 1 2 In the isolated pulse repetition period pulse and transmission line clock Generates an isolated pulse for cutting point detection from the pulse CP and sends it to the driver circuit 12 1 and the station-side echo canceller circuit 17 via the transmission-side operation switching switch 1 13 and the timer circuit 16 2 Also sends an isolated pulse to the start terminal of.

In the disconnection point detection operation, the station-side echo canceller circuit unit 17 stops the operation including the training because the station-side echo canceller operation switching switch 17 1 is OFF. The driver circuit 122 drives the light emitting element 122 with an isolated pulse and converts it into an optical isolated pulse. This optical isolated pulse is sent to the optical fiber 30 through the optical coupler 13 on the local side.

And, as shown in Fig. 4, in the echo canceller bidirectional optical transmission system, there is no burst period unlike the time axis compression multiplexed bidirectional optical transmission system, so that the propagation time is twice the propagation time of the maximum transmission distance (Lmax) ( An isolated pulse may be transmitted at a period longer than Tmax). In the figure, the transmitted light isolated pulse 3 12 is totally reflected at the cut point 3 1 of the optical fiber 30 and becomes the received light isolated pulse 3 14.

That is, the light isolated pulse 3 14 reflected at the cut point 31 of the optical fiber enters the light receiving element 14 1 through the local optical coupler 13 and is extracted as an electric signal by the preamplifier circuit 14 2. You. This electric signal is applied to the station side subtractor 18, but since the station side echo canceler circuit section 17 has stopped operating, it is directly amplified by the equalizing amplifier circuit 15 1 and the identification circuit 15 3 I can get calories.

Here, there is no problem if the equalizing amplifier circuit 15 1 has a fixed gain, but since the AGC (Automatic Gain Control) is normally operating, the equalizing amplifier circuit 15 1 The gain is fixed to the maximum gain with the gain switch 1 5 5.

In the normal operation mode, the clock of the identification circuit 1553 uses the clock extracted by the timing extraction circuit 152 from the received signal.In the cutting point detection operation mode, the identification clock switching switch 1556 is switched and the transmission side is switched. Is used.

Here, in order to reliably identify the received light isolated pulse 3 14 by the transmission line clock on the transmission side, the time width of the transmitted light isolated pulse 3 1 2 is set to the reciprocal of the transmission line cut-off frequency by 2 Needless to say, it should be doubled or doubled.

When the identification circuit 153 identifies the reception isolated pulse 314, the identification output is applied to the stop terminal of the timer circuit 162 via the reception-side operation switching switch 157. Timer times Path 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 transmitted light solitary pulse 3 1 2 from wrapping around to the receiving side and destabilizing the cut point detection operation, the pulse applied to the start terminal of the timer circuit 16 2 must be delayed or discriminated. It goes without saying that the switching of the receiving-side operation switching switch 157 for sending the output to the stop terminal of the timer circuit 162 may be delayed.

From the detection result output terminal of the timer circuit 16 2, the value of the measured time value 1 Z 2 is sent to the station-side control circuit 16 1, and further via the common control unit 5 of the station-side transmission device 10. Sent to the operation support system 7. The operator looks at the result of the optical fiber break point detection and arranges for repair of the optical fiber.

Here, assuming that 1/2 of the measured time value is read from the detection result output terminal of the timer circuit 162, there is no problem with the measured value of the timer itself as the force value. Needless to say, the conversion processing into the distance may be executed in the common control unit 5 or the operation support system 7 of the station-side control circuit 16 1 or the station-side transmission device 10.

Single-core, single-wavelength, time-axis multiplexed bidirectional optical transmission system (one-to-many connection: Figures 1 and 11) Next, both one-core, same-wavelength, time-axis compression and one-to-many connection optical branches shown in Figure 11 An example in which an optical fiber disconnection failure occurs in the branch fiber 302 when the transmission circuit of FIG. 1 is applied to the optical transmission system will be described with reference to FIG. Note that the echo-canceller method shown in Fig. 5 is not applied in the same way as the conventional example!

In this case, taking into account the transmission distance (propagation delay time) between each ONU 201 and OLT 101, the time window T w for guaranteeing the operation of the ONU 210 furthest inside the house is considered. Is provided.

As shown in Fig. 6, the total ONU operation guarantee window Tw requires a time longer than the propagation delay time of twice the longest distance (Lmax) plus the protection time (Tg).

In other words, if the upstream signal disconnection from a specific ONU 201 is detected in the reception burst 1 1 14 of the local station LT 101, it is determined that the fiber is cut off at the branch fiber 302 and the local station The operation of the transmitting / receiving unit is switched from the normal operation to the disconnection point detection operation. At this time, at the start of the ONU operation guarantee window Tw, an optical isolated pulse 3 1 2 is generated, and the optical coupler 1 The data is sent to the optical fiber 301 toward all the inside ONUs via 3.

In other words, the isolated pulse generation circuit 112 generates an isolated pulse for cutting point detection from the burst frame pulse F shown in Fig. 12 and the transmission line clock pulse of the bit stream shown in Fig. 13 and switches the transmission side operation. The signal is sent to the driver circuit 121 via the switch 113 and an isolated pulse is sent to the start terminal 162a of the timer circuit 162. The driver circuit 122 drives the light emitting element 122 with an isolated pulse and converts it into an optical isolated pulse. The optical isolated pulse is sent to the optical fiber 30 through the optical coupler 13 on the optical line side.

Then, as shown in FIG. 6, the transmitted light isolated pulse 3 1 2 is totally reflected at the cutting point 3 0 3 (when the supporting fiber 3 0 2 is present), for example, in the case of the optical fiber 30, and is coupled to the station side. It returns to the station side receiving logic circuit section 15 through the device 13 as the received light isolated pulse 3 14. The station side receiving logic circuit section 15 is different from the normal operation state, in which the equalization function of the regenerative relay function (equalization amplification, timing extraction and identification function) is fixed to the maximum gain, and the identification function is It waits for a reflected light isolated pulse at a normal threshold (usually 0.5). That is, the light isolated pulse is extracted as an electric signal by the preamplifier circuit 142 to the light receiving element 144. This electric signal is amplified by the equalizing amplification circuit 15 1, and is amplified by the identification circuit 15 3. Here, there is no problem if the equalizing amplifier circuit 15 1 has a fixed gain, but since the AGC (Automatic Gain Control) is normally operating, the equalizing amplifier circuit 15 1 The gain is fixed to the maximum gain with the gain switching switch 1 5 5.

In the normal operation mode, the clock of the identification circuit 1553 uses the clock extracted from the received signal by the timing extraction circuit 152, but in the break point detection operation mode, the identification clock switching switch 1556 is switched to change the transmission side. Use the transmission path clock CP. Here, in order to reliably identify the isolated solitary pulse by the transmission-side transmission path CP of the transmitting side, the time width (connection time) of the transmitted solitary pulse is twice or twice the reciprocal of the transmission line clock frequency. That is all.

When the identification circuit 153 identifies the received isolated pulse, the identification output is transferred to the stop terminal 162 b of the timer circuit 162 via the reception-side operation switching switch 157. Timer circuit 162 starts measurement when a pulse is applied to start terminal 162a, and stops measurement when a pulse is applied to stop terminal 162b. Here, in order to prevent the transmitted light isolated pulse 3 1 2 from wrapping around to the receiving side and making the break point detection operation unstable, delay the pulse applied to the start terminal 16 2 a of the timer circuit 16 2 It is sufficient to delay the switching timing of the receiving-side operation switching switch 157 for sending the input or the identification output of the identification circuit 153 to the stop terminal 162 b of the timer circuit 162.

From the detection result output terminal 16 2 c of the timer circuit 16 2, the value of the measured time value 1 Z 2 is sent to the station side control circuit 16 1, and furthermore, the common control unit of the station side transmission device 10. It is sent to the operation support system 7 via 5.

Then, when 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 cutting point 303 of the optical fiber 30 is calculated. Can be requested. The clock for the timer may be used exclusively for the timer, or the clock of the transmission path signal may be used as it is, or may be divided or multiplied. The operator looks at the result of detecting the optical fiber cutting point and arranges for repair of the optical fiber 30.

Here, it is assumed that 1/2 of the measured time value is read from the detection result output terminal 162c of the timer circuit 162, but the timer measurement value itself may be used as the value. The conversion of the optical fiber 30 into the distance to the cut point 303 is performed by the station-side control circuit 161, the common control unit 5 of the station-side transmission device 10, or the operation support system 7. Needless to say, this may be done.

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

That is, when receiving the alarm output indicating that the transmission signal has been cut off from the station-side reception logic circuit 154, the station-side control circuit 161 of the station-side transmission circuit 1 automatically switches off from the normal operation in the same manner as above. Switch to break point detection operation.

Then, the distance to the disconnection point is measured in the timer circuit 16 2, the result is transmitted to the common control unit 5 of the station side transmission device 10, and the operation is returned to the normal operation. In addition, the common control unit 5 of the station-side transmission device 10 uses the station-side transmission circuit number (1 # 1 to 1 # N) that detected the failure and the numerical value of the measurement result as an operation support system in the form of a bucket message. Notify 7 autonomously.

An example of this packet message is shown in Fig. 3, where "message number" indicates an identifier for identifying the message between the station-side transmission device and the operation support system, and "transmission circuit number" usually indicates " Indicates the physical location identifier consisting of “building name, floor, rack number, unit number, shelf number, package number, interface number”.

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

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

Switching between the normal operation mode and the disconnection point detection operation mode is performed while the OLT 101 on the station side is down and transmitting the burst signal 1 1 1 2 and receiving the upstream burst signal 1 1 1 4 During this period, the operation mode is the normal operation mode, and the mode is switched to the disconnection inspection operation mode only during the entire ONU operation guarantee window Tw.

In addition, since the optical isolated pulse used for detecting the fault point is within the operation guarantee window Tw, other ONUs that have not caused the branch fiber breakage are not affected by this break point detection operation, and the normal service is not affected. Operation is not hindered.

In addition, the common control unit 5 of the station-side transmission device 10 autonomously notifies the operation support system of the station-side transmission circuit number that detected the failure and the numerical value of the measurement result to the operation support system in the form of a bucket message. The example is the same as that shown in Fig. 3, except that the ONU number is added to the end of the transmission circuit number.

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, there is no need to replace the optical connector of the optical termination terminal of the optical fiber in which the measuring instrument has failed, and to access the instrument, and to connect the measuring instrument via the optical splitter and the optical switch.

For this reason, when replacing optical connectors, failures may occur from a large number of optical termination terminals. It eliminates much of the work of identifying the optical fiber terminals and connecting the measuring instrument, and also prevents the mistake of connecting the measuring instrument to the normal optical fiber due to human error. is there.

In addition, there is an advantage that large-scale equipment for connecting the measuring instrument via the optical splitter and the optical switch is not required.

Furthermore, there is no need to use a dedicated wavelength for measurement that is different from the wavelength at which information is transmitted unlike the conventional optical fiber breakpoint detection, and the advantage is that the optical fiber breakpoint can be detected only at the information transmission wavelength. There is.

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

Furthermore, in the point-to-multipoint connection type optical branching bidirectional optical transmission system, by using the delay measurement function provided in the PON transmission system, it is possible to use a branch line without affecting other users who are currently using the service. There is an advantage that a fiber fault break point can be detected.

The advantage that the operation of the operator can be greatly reduced because the optical fiber disconnection failure can be detected by the transmission signal interruption, and the operation can be autonomously switched by the station side transmission circuit and the detection result can be autonomously transmitted to the operation support system. There is.

Claims

The scope of the claims

1.In the method of performing bidirectional optical transmission at the same wavelength between the station side transmission circuit and the home side transmission circuit using a single-core optical fiber,

A first step in which the station-side transmission circuit detects a corresponding in-home transmission circuit based on a response failure of the in-home transmission circuit;

A second step in which the station side transmission circuit detects a fault point by transmitting an optical isolated pulse to a home inside transmission circuit corresponding to the response fault;

A method comprising:

2. In Claim 1,

When the station-side transmission circuit and the home-side transmission circuit have a one-to-many connection relationship in a point-to-multipoint connection type optical branching bidirectional optical transmission system, the station-side transmission circuit performs the first step in the first step. When the response failure is detected for any one of the inside transmission circuits, the optical isolated pulse is transmitted to the transmission line within a predetermined operation guarantee time in the second step to detect the failure point. A method characterized by performing.

3. In Claims 1 or 2,

When detecting the response failure in the first step, the station-side transmission circuit notifies the operation support system of the result, and receives an instruction from the operation support system to switch from a normal operation to a disconnection point detection operation. Performing the second step.

4. In Claim 1,

A method characterized in that said bidirectional optical transmission is performed by time axis compression multiplexing or an echo canceller method.

5. In a system that performs bidirectional optical transmission at the same wavelength between the office-side transmission circuit and the home-side transmission circuit using a single-core optical fiber,

The station-side transmission circuit detects a corresponding home-side transmission circuit based on a response failure of the home-side transmission circuit, and sends out an optical isolated pulse to the home-side transmission circuit corresponding to the response failure, thereby detecting a failure point. A system characterized by performing.

6. In Claim 5, When the office-side transmission circuit and the home-side transmission circuit have a one-to-many connection relationship in a one-to-many connection type optical branching bidirectional optical transmission system, the office-side transmission circuit is connected to the home-side transmission circuit. A system which detects the response failure for any one of the above, and sends out the optical isolated pulse to a transmission line within a predetermined operation guarantee time to detect a failure point.

7. In claims 5 or 6,

When the station side transmission circuit detects the response failure, it notifies the operation robot system of the result, and when receiving the switching instruction from the normal operation to the disconnection point detection operation from the operation support system, the failure is detected. A system characterized by performing point detection.

8. In Claim 5,

The bidirectional optical transmission is performed by time axis compression multiplexing or echo canceller method.

9. In a transmission circuit on the office side that performs bidirectional optical transmission at the same wavelength to the transmission circuit inside the house using a single-core optical fiber,

First means for detecting a corresponding home-side transmission circuit based on a response failure of the home-side transmission circuit;

Second means for detecting a fault point by transmitting an optical isolated pulse to the in-home transmission circuit corresponding to the response fault,

A transmission circuit comprising:

10. In Claim 9,

When the station-side transmission circuit and the home-side transmission circuit are in a one-to-many connection relationship in a point-to-multipoint connection type optical branching bidirectional optical transmission system, the first means includes: The transmission circuit is characterized in that the response failure is detected in any one of the cases, and the second means sends the optical isolated pulse to a transmission line within a predetermined operation guarantee time to detect a failure point. Road.

1 1. In claims 9 or 10,

The first means notifies the operation support system of the result when the response failure is detected, and when the operation support system receives an instruction to switch from the normal operation to the disconnection checkout operation, the second means Characterized by detecting fault points Transmission circuit.

12. In Claim 9,

A transmission circuit characterized in that the bidirectional optical transmission is performed by time axis compression multiplexing or an echo canceller method.