JP3111925B2 - Distance measurement system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring system, and more particularly, to a transmission system in which an intra-office device and a plurality of subscriber devices are connected, a logical transmission distance between the intra-office device and one subscriber device. The present invention relates to a distance measuring system for measuring the distance.

[0002]

2. Description of the Related Art An example of a schematic configuration of a conventional optical transmission system is shown as a block in FIG. In FIG. 2, a plurality of subscriber units 200.1-200. n is the star coupler 3
00, a large number are connected to the intra-office device 100. As a communication method between the intra-office device and the subscriber device, the downstream signal (cell) from the intra-office device 100 is of a broadcast type since the signal is branched to the subscriber device by the star coupler 300 and flows. Since the upstream signal (cell) from each subscriber unit is optically multiplexed by the star coupler 300, each subscriber unit becomes a multiplex type when it does not output an optical signal when it is not a time slot assigned to itself. ing.

[0003] To this end, a downlink signal from the intra-office device 100 is used to transmit an uplink cell of each subscriber device in an upward timing.
Grayed (time i.e. time slot number in the intra-office device that allows delivery) can be notified to each subscriber unit, at the time of the uplink reference timing of the time slot number (cell sending timing between respective subscriber units Yes, the reference value)
It is necessary to work to match. Therefore, in order to determine the timing, that is, to synchronize, the following distance measurement is usually performed.

A method for measuring the distance between devices will be described. First,
The intra-office device sends a downstream distance measurement cell to the subscriber device side, the subscriber device receives the distance measurement cell, writes an identification number unique to the own device in the distance measurement cell, and transmits the upstream distance. It is returned to the station device as a measurement cell.

[0005] As a method of synchronization, the value of the subscriber unit obtained in this way is transmitted from the intra-office unit to the subscriber unit, and the subscriber unit transmits an uplink cell with a delay of the value. As a result, uplink synchronization is established.

In such a conventional distance measuring method, an area (time) for distance measurement is always fixedly set,
Monitors distance measurement constantly. Such a technique is disclosed, for example, in Japanese Patent Application Laid-Open No. 7-135506.

[0007]

A problem in the prior art is a time division cell burst system in which a plurality of subscriber units are connected from the intra-office unit via the same transmission line.
Since it is impossible to transmit information to a part of the distance measurement area, it is impossible to effectively use information transmission of a transmission path. The reason is that the distance measurement area for performing the distance measurement from the subscriber device to the intra-station device is fixedly assigned to a part of the transmission cell from the subscriber device to the intra-station device.

An object of the present invention is to set a distance measurement area (referred to as a window) only when a distance measurement is necessary, and to perform a distance measurement between them, thereby restricting the transmission of normal information cells as much as possible. It is to provide a reduced distance measuring system.

[0009]

According to the present invention, in a transmission system in which an intra-office device and a plurality of subscriber devices are connected, a logical transmission distance between the intra-office device and one subscriber device is determined. A distance measuring system for measuring, wherein only when a phase measurement is lost during a service and a distance measurement is necessary, a restriction window for restricting information transmission to the intra-office device is set for the subscriber unit, and a distance between the restriction windows is set. A distance measurement system characterized by performing the measurement is obtained.

[0010] The intra-station device transmits a restriction signal to all the subscriber devices for setting the restriction window, and then transmits a distance measurement signal to the one subscriber device. Transmission means, further comprising the subscriber
A phase synchronization detecting means for detecting a phase synchronization state of a signal from the device, and a control means for controlling transmission by the transmitting means when the phase synchronization is lost by the phase synchronization detecting means.

Further, the subscriber unit has means for returning the distance measurement signal to the intra-station device in response to receiving the distance measurement signal addressed to the own device.

[0012] Still further, the intra-station device includes means for measuring a distance based on a distance measurement signal from the subscriber device, and means for canceling the setting of the limit window in response to the end of the distance measurement. It is characterized by having.

The operation of the present invention will be described. Normally, uplink information and downlink information are transmitted, but when distance measurement is necessary due to a failure or the like, a distance measurement cell is transmitted only in such a case. During that time, the intra-office device sends an uplink information restriction signal to all the subscriber devices, and immediately releases the uplink information restriction signal immediately after the distance measurement is completed, thereby effectively utilizing the transmission path. I am doing it.

[0014]

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

Referring to FIG. 1, first, an intra-office device 100 will be described. The downlink cell generation unit 1 generates a cell to be transmitted as the downlink signal 16 from the downlink information 11, the distance measurement cell when the downlink distance measurement request signal 12 is input, the uplink information restriction cell when the uplink information restriction signal 13 is input, and the phase information. When the synchronization control signal 23 is input, the phase synchronization control cells output the downlink signal 16 respectively.

The distance measurement cell request unit 2 stops outputting the downlink distance measurement request signal 12 when the distance measurement end signal 15 is input, and outputs the downlink distance measurement request signal 12 when the phase shift occurrence signal 14 is input. Output to

The distance measurement determination section 4 outputs the phase shift occurrence signal 1
At the time of input of 4, the cell for uplink distance measurement notified in a predetermined time range is recognized, a value for performing phase synchronization with the subscriber device 200 is acquired, and the distance measurement end signal 15 is sent to the distance measurement cell request unit 2. And outputs the same to the downlink cell generator 1 as the phase synchronization control signal 23.

The phase synchronization monitoring unit 3 monitors the upstream signal 21 and outputs an upstream information control signal 13 to the downstream cell generation unit 1 and a phase shift generation signal 14 to the distance measurement cell request unit 2 when the phase synchronization is lost. When the distance measurement end signal 15 is input, the output of the upstream information control signal 13 and the phase shift generation signal 14 is stopped.

Next, the subscriber device 200 will be described.
The cell determination unit 5 determines whether the cell of the downlink signal 16 is a cell of downlink information, a cell for distance measurement, or a cell for uplink information restriction, and when a cell for downlink distance measurement is recognized, the cell detection signal 17 for distance measurement, When an uplink information restricted cell is recognized, an uplink information restricted cell detection signal 18 is output to the uplink cell generator 7.

The phase synchronization control unit 6 sets the cell output timing of the uplink signal 21 with the value specified by the phase synchronization control cell transmitted by the downlink signal 16, and sets the uplink timing signal 19
Is output to the upstream cell generation unit 7.

The upstream cell generator 7 generates the upstream timing signal 1
9 generates a cell to be transmitted as the uplink signal 21 from the uplink information 20 at the timing specified by the step 9. When the distance measurement cell detection signal 17 is input, transmission of the cell generated from the uplink information 20 is prohibited, and the uplink distance measurement is performed. Cell for uplink signal 2
1 is output, and when the uplink information restricted cell detection signal 18 is input, the transmission of the cell generated from the uplink information 20 is stocked and not transmitted.

Referring to FIG. 2, subscriber unit 200.1
~ 200. n is the intra-station device 10 by the star coupler 300.
The configuration in which many are connected to 0 is the same as in the related art.

Next, the operation of the block shown in FIG. 1 will be described. In the state where the distance measurement control from the intra-station device 100 in FIG. 1 is normally performed and the phase synchronization of the signal 21 is established, the downlink information 11 is transmitted from the intra-station device 100 by the downlink cell generation unit 1 to the subscriber unit. The signal is transmitted to 200 as a downlink signal 16.

The phase synchronization between the intra-station device 100 and the subscriber device 200 is established by the value (time slot number) of the phase synchronization control cell transmitted by the downlink signal 16.
The subscriber unit 200 transmits the uplink timing signal 19 to the uplink cell generation unit 7 with the value of the phase synchronization control cell designated previously by the phase synchronization control unit 6, and converts the uplink information 20 as the phase-synchronized uplink signal 21. It has a configuration for transmitting.

When the phase synchronization of the uplink signal 21 is deviated due to a failure or the like, the phase synchronization monitoring unit 3 of the intra-station device 100 detects the dephasing and outputs it as a phase deviation generation signal 14 to the distance measurement cell requesting unit 2. The measurement cell request unit 2 outputs the downlink distance measurement request signal 12 to the downlink cell generation unit 1 to perform distance measurement using the phase shift occurrence signal 14 as an input. At the same time, since the phase synchronization monitoring unit 3 measures the distance by detecting the loss of phase synchronization, the subscriber unit 200 sends the uplink information control signal 13 to the downlink cell generation unit 1 so that the uplink information 20 of the uplink signal 21 does not overflow. And outputs the uplink information restricted cell to the downlink signal 16.

In this case, a cell for distance measurement is transmitted as a downlink signal 16 from the downlink cell generator 1 of the intra-station device 100 to the subscriber device 200, but the intra-station device 100 does not know the distance between the devices. In order for the subscriber device 2
It is unclear whether the cell for measuring the upstream distance is returned from 00. Therefore, the window for distance measurement is opened, and while the window is opened, the return of the cell for upstream distance measurement is waited.

Here, the window means that when an uplink cell from another subscriber device returns while the distance measurement is being performed, the optical signal is multiplexed by the star coupler 300 and cannot be recognized by the intra-office device 100. This means that an area from which the transmission of uplink cells is prohibited from the apparatus 100 for a certain period is set. The setting of this window is performed by the uplink information restriction cell transmitted from the downlink cell generation unit 1 in response to the generation of the uplink information restriction signal 13 from the phase synchronization monitoring unit 3, and the distance measurement determination unit 4 measures the distance. This window is continued until is completed.

The subscriber unit 200 separates the uplink information restricted cell and the cell for measuring the downlink distance from the downlink signal 16 in the cell determination unit 5 and detects the uplink information restricted cell which is an output when the uplink information restricted cell is detected. A signal 18 and an output distance measurement cell detection signal 17 resulting from detection of a downlink distance measurement cell are output to the uplink cell generation unit 7.

The upstream cell generation unit 7 outputs the upstream distance measurement cell to the upstream signal 21 when the distance measurement cell detection signal 17 is input, and outputs it until the distance measurement is completed by the distance measurement determination unit 4 of the intra-station device 100.

When the distance measurement is completed, the distance measurement determination unit 4
Since the distance measurement has been completed to the phase synchronization monitoring unit 3 and the distance measurement cell requesting unit, a distance measurement end signal 15 is output, and the phase synchronization control value collected by the uplink distance measurement cell is transmitted to the downlink cell generation unit 1. It is output as a synchronization control signal 23.

The above operation enables the effective use of the transmission path without securing a fixed distance measurement area in the cell for distance measurement.
During the distance measurement, the upstream information 20 is stocked so as not to be output as the upstream signal 21.

The distance measuring cell, the phase synchronization control cell,
The determination of the information-restricted cell and the information cell can be made by adding a special header used only in this section to each cell. Also, the destination of the cell from the intra-office device to the subscriber device is attached to the header, and each subscriber device determines whether or not the cell is addressed to the own device based on the destination. It should be noted that the information restriction cell for window setting is set to all the subscriber units 20.
0.1-200. n.

[0033]

As described above, according to the present invention, the window for distance measurement is opened only when the distance measurement such as a failure is required, and the distance measurement cell is transmitted.
Normally, only information cells can be transmitted, and the transmission path can be effectively used.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a system diagram to which an embodiment of the present invention is applied;

[Explanation of symbols]

 Reference Signs List 1 downlink cell generation unit 2 distance measurement cell request unit 3 phase synchronization monitoring unit 4 distance measurement determination unit 5 cell determination unit 6 phase synchronization control unit 7 uplink cell generation unit 100 intra-station device 20.1 to 200. n subscriber device 300 star coupler

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/44 H04L 7/00 H04L 12/28

Claims (5)

(57) [Claims] 1. A distance measuring system for measuring a logical transmission distance between an intra-station device and one subscriber device in a transmission system in which the intra-station device and a plurality of subscriber devices are connected, the service comprising: Only when it is out of phase synchronization and a distance measurement is required, a restriction window for restricting information transmission to the intra-station device is set for the subscriber unit, and a distance measurement is performed during that period. A distance measuring system characterized by: 2. The intra-station device transmits a restriction signal to all subscriber devices for setting the restriction window,
2. The distance measurement system according to claim 1, further comprising a transmission unit that transmits a distance measurement signal to said one subscriber device. 3. The in-station device includes: a phase synchronization detecting unit that detects a phase synchronization state of a signal from the subscriber unit; and when the phase synchronization is lost by the phase synchronization detecting unit,
3. The distance measuring system according to claim 2, further comprising control means for performing transmission control by said transmission means. 4. The apparatus according to claim 1, wherein said subscriber unit has means for returning said distance measurement signal to said intra-office device in response to receiving said distance measurement signal addressed to itself. The distance measuring system according to any one of claims 1 to 3. 5. The intra-station device includes: a unit that performs distance measurement based on a distance measurement signal from the subscriber device; and a unit that cancels the setting of the limit window in response to completion of the distance measurement. The distance measuring system according to claim 4, further comprising: