JP2001197096A - Passive double-star transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PDS transmission system which eliminates the need for wiring between subscriber devices and can transfer an alarm to an in-office device even if a signal cannot be received normally in a subscriber device. SOLUTION: A timer part is provided and made to operate based on normal up-directional signal output timing reported from an in-office device to respective subscriber devices and even if a subscriber device becomes unable to receive the up-directional signal output timing normally from the in-office device, an alarm is transferred according to the timing clocked by the timer part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passive double-star transmission system, and more particularly to a passive double-star transmission system suitable for transferring an alarm generated in a subscriber unit to an intra-office device.

[0002]

2. Description of the Related Art Recent advances in optical communication technology and information processing technology have led to the development of cable television (CAT).
V), a video distribution service and a video on demand (VOD) service have been realized. As a system suitable for providing such a service, Passive Double Star (Passive Double Star)
Star: Hereafter abbreviated as PDS. ) There is a transmission system.

[0003] In the PDS transmission system, an in-station device that provides services such as video is connected to a plurality of subscriber devices that receive the service via a star coupler.
The intra-station device, the star coupler, and the subscriber device are connected by a transmission line such as an optical fiber. Service information such as video is broadcast from the intra-office device to all the subscriber devices. On the other hand, control information and the like from a subscriber device are transmitted at a timing at which output signals from other subscriber devices do not collide. The transmission timing of each subscriber device is managed by the intra-station device, and a signal output phase is specified by a transmission signal from the intra-station device. As described above, in the PDS transmission system, a part of the transmission path from the intra-station device to the star coupler can be shared among a plurality of subscriber devices, so that the system can be reduced in size and economical.

By the way, if the direction from the intra-office device 10 to each subscriber device is the down direction, and the direction from each subscriber device to the intra-station device 10 is the up direction, one of the subscriber devices will be transmitted from the intra-station device for some reason. If the downstream signal cannot be received normally, the subscriber unit cannot receive the instruction of the output phase of the upstream signal to the intra-station device.
Therefore, in order to prevent a collision with a signal from another subscriber device, a subscriber device that cannot normally receive a downlink signal has to stop an uplink signal. That is, not only can the subscriber unit not transmit an alarm indicating the occurrence of a failure, but also the intra-office unit can detect the loss of the input signal from the subscriber unit, but this is due to the failure of the subscriber unit itself. It is impossible to determine whether the error is due to a failure in the transmission path or not, and the maintainability of the entire system is reduced.

[0005] Therefore, even in the case where the subscriber unit cannot normally receive the downlink signal from the in-station unit,
There is disclosed a technology that enables alarm transfer from a subscriber device to improve system maintainability.

FIG. 3 shows a conventional PDS transmission system.
This is an outline of the system configuration. This PDS transmission
In the system, the intra-station device 10 is connected via a star coupler 11.
Then, the first to m-th (m is a natural number) subscriber units 12₁~
12_mIt is connected to the. Station device 10 and star coupler
11. Star coupler 11 and first to m-th subscriber units 12
₁~ 12_mBetween transmission lines 13 and 14, respectively.₁~ 14_m
Connected by First to m-th subscriber units 12₁~ 1
2_mAre the phase information transmitting / receiving circuits 15₁~ 15_mBe prepared
The phase information is transmitted to each other via the phase information signal line 16.
Received.

[0007] Output signals from the intra-station device 10 are transmitted via the star coupler 11 to the first to m-th subscriber devices 12 ₁ to 12 _1.
It is broadcast to 2 _m. At this time, the transmission timings of the _first to _m-th subscriber devices 121 to 12m managed by the intra-station device 10 are notified as a signal transmission phase instruction for each subscriber device. Each subscriber unit transmits an output signal to the intra-station device 10 in accordance with the designated signal transmission phase. Phase information transmitting and receiving circuit of each subscriber unit 15 ₁ to 15 _m
Transmits the transmission phase of the output signal from each subscriber unit to another subscriber unit via the phase information signal line 16.
Accordingly, the subscriber unit 12 ₁ to 12 _m of the first to m is
The other device other than the own device recognizes at which phase the signal is transmitted to the intra-office device.

[0008] Therefore, the subscriber unit that cannot receive the downlink signal from the intra-office unit 10 properly for some reason is the output signal of the other subscriber unit collected via the phase information signal line 16. , A vacant phase is detected from the transmission phase, and an alarm generated by the own apparatus is transferred to the intra-office apparatus 10 at a phase that does not collide with an output signal from another subscriber apparatus.

A technique relating to such a PDS transmission system is disclosed, for example, in Japanese Patent No. 2669356, entitled “PDS Transmission System”.

[0010]

However, in the PDS transmission system proposed in the prior art, it is necessary to manage the transmission phase of the upstream signal to all the intra-station devices connected to the star coupler. Wiring such as a phase information signal line for notifying each subscriber unit of the transmission phase of an upstream signal to the intra-office device is required. Therefore, a separate construction different from the construction work of the transmission line is required, and there is a problem that the economic efficiency of the system is reduced.

Therefore, an object of the present invention is to eliminate the need for wiring between subscriber units, and to transmit an alarm to an intra-office unit even when a signal cannot be received normally in the subscriber unit. It is an object of the present invention to provide a PDS transmission system that can perform the above.

[0012]

According to the first aspect of the present invention, there are provided (a) an intra-office device for notifying different transmission timings, (b) a star coupler for making multiple connections to the intra-office device, and C) When the received signal from the intra-station device connected to the star coupler cannot be processed normally, the intra-station device transmits the signal to the intra-station device based on the transmission timing addressed to the own device notified by the intra-station device. The PDS transmission system is provided with one or a plurality of subscriber devices for transmitting a signal to the PDS transmission system.

That is, according to the first aspect of the present invention, in a PDS transmission system in which an intra-office device and one or a plurality of subscriber devices are connected one-to-many by a star coupler, the subscriber device is notified by the intra-station device of the subscription. The transmitting device extracts the transmission timings different from each other, and when the reception signal from the intra-office device cannot be processed normally, generates the transmission timing to the intra-office device based on the extracted transmission timing and generates the intra-office device. Is transmitted.

According to a second aspect of the present invention, in the PDS transmission system according to the first aspect, the transmission timing is measured based on a transmission timing addressed to the own device, and then stopped after a predetermined time has elapsed. Features.

According to the second aspect of the present invention, when the received signal from the intra-station device cannot be processed normally, the transmission timing to the intra-station device measured based on the extracted transmission timing elapses a predetermined time after the start of the timing. And then stop.

According to the third aspect of the present invention, (a) an intra-office device for notifying mutually different transmission timings, and (b) a star coupler for making multiple connections to the intra-office device,
(C) monitoring means connected to each of the star couplers for monitoring whether or not a received signal from the intra-station device has been normally processed, and extracting means for extracting a transmission timing addressed to the own device from the received signal from the intra-station device And a timer means for timing the signal transmission timing addressed to the intra-office device based on the transmission timing extracted by the extraction means, and the transmission means extracted by the extraction means when the reception signal can be normally processed as a result of monitoring by the monitoring means. A signal transmitting means for transmitting a signal to the intra-office device in accordance with the timing, and transmitting a signal to the intra-office device in accordance with the transmission timing to the intra-office device measured by the timer when the received signal cannot be processed normally; The PDS transmission system is provided with one or a plurality of subscriber devices including

That is, according to the third aspect of the present invention, in a PDS transmission system in which an intra-office device and one or a plurality of subscriber devices are connected one-to-many by a star coupler, the subscriber device receives from the intra-office device by an extracting means. While extracting the transmission timing addressed to the own device from the signal, the monitoring means monitors whether or not the received signal from the in-station device has been normally processed. As a result of monitoring by the monitoring means, when the received signal can be processed normally, a signal is transmitted to the intra-office device in accordance with the transmission timing extracted by the extracting means, and when the received signal cannot be processed normally, the extracting means A signal is transmitted to the intra-office device in accordance with the transmission timing to the intra-office device measured based on the extracted transmission timing.

According to a fourth aspect of the present invention, in the PDS transmission system according to the third aspect, the timing means performs timing based on a transmission timing addressed to the own device, and stops after a lapse of a predetermined time. .

That is, in the invention according to the fourth aspect, when the received signal from the intra-station device cannot be processed normally, the timing device sets the transmission timing to the intra-station device based on the extracted transmission timing to a predetermined time. Stop after the elapse.

According to a fifth aspect of the present invention, in the PDS transmission system according to the first to fourth aspects, the signal output at the transmission timing to the intra-office device is an alarm for notifying that a failure has occurred in the subscriber device. It is characterized by being information.

That is, according to the fifth aspect of the present invention, at the transmission timing to the intra-office device, the alarm information for notifying the occurrence of a failure in the subscriber device is transmitted, so that the maintainability of the intra-office device is improved. Can be.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

First Embodiment

FIG. 1 shows an outline of the configuration of the PDS transmission system in the first embodiment. In the PDS transmission system in the first embodiment, the in-station device 20
Are connected to the _first to n-th (n is a natural number) subscriber units 22 _{1 to} 22 _n via a star coupler 21. Station device 20 and star coupler 21, star coupler 21 and first
The n-th subscriber units 22 _{1 to} 22 _n are connected by transmission lines 23 and 24 _{1 to} 24 _n , respectively. The star coupler 21 is connected to the transmission line 23 transmitted by the intra-station device 20.
And outputs demultiplexed to the transmission line 24 ₁ to 24 _n a transmission signal of the above first to n subscriber units 22 ₁ through 22 _n transmission signal on the transmission path 24 ₁ to 24 _n delivered by the Are multiplexed to the transmission line 23 and output.

In the following, the direction from the intra-station device 20 to each subscriber device is defined as a down direction, and the direction from each subscriber device to the intra-station device 20 is defined as an up direction.

The first to n-th subscriber units 22 _{1 to} 22 _n are:
Each of them has the same configuration, and FIG. 1 shows only the first subscriber unit. First subscriber device 2
2 ₁ is a transmission line transmission separation unit 25 ₁ and a downlink signal processing unit 26
_1, the timer unit 27 _1, the selector 28 _1, and a uplink signal processing unit 29 _1.

The transmission line transmission separation unit 25 ₁ separates a downstream signal from a transmission signal on the transmission line 24 ₁ and outputs the separated signal to the downstream signal processing unit 26 ₁ , and outputs an upstream signal on the transmission line 24 ₁ It sends the upstream signal from the processing unit 29 _1.

The downlink signal processing section 26 ₁ extracts, from the downlink signal separated by the transmission line transmission separation section 25 ₁ , the output timing of the upstream signal addressed to the own device included in the signal and outputs it as the extracted transmission timing 30 _1. , To the timer section 27 ₁ and the selection section 28 ₁ . Further, the downlink signal processing unit 26 ₁ monitors whether or not the downlink signal separated by the transmission path transmission separation unit 25 ₁ has been normally processed,
As a result, when the down signal cannot be processed normally, the alarm signal 31 ₁ is output to the selecting unit 28 ₁ .

The timer unit 27 ₁ performs time counting based on the extracted transmission timing 30 ₁ extracted by the downlink signal processing unit 26 ₁ , and the timed timing 32 _{1 as} a result of the time counting.
And outputs to the selection unit 28 _1.

The selecting section 28 _1, when able to process successfully downstream signal by the alarm signal 31 ₁ is a monitoring result of a downlink signal by the downlink signal processor 26 _1, extracted by the downlink signal processor 26 ₁ Extracted transmission timing 3
0 ₁ is selected and output to the upstream signal processing section 29 ₁ as upstream signal transmission timing 33 ₁ . On the other hand, when it could not be processed successfully downstream signal by the alarm signal 31 ₁ from the downstream signal processing unit 26 _1, select the clocking timing 32 ₁ counted by the timer unit 27 _1, the uplink signal transmission timing 33 ₁ and outputs it to the uplink signal processing unit 29 ₁ as.

The uplink signal processing unit 29 _1, the uplink signal transmission timing 33 ₁ from the selector 28 _1, for processing and uplink signal output. Thereby, the transmission path transmission separation unit 25
₁ transmits an upstream signal to the transmission path 24 ₁ and outputs the star coupler 2
1 to the intra-station device 20.

The PD in the first embodiment having the above-described configuration
S The transmission system, the subscriber unit 22 ₁ through 22 _n of the first to n from the station device 20 notifies the signal output timing of the uplink, the subscriber of the first to n 22 21 _to
2n extracts the upstream signal output timing addressed to the own device and transmits the upstream signal addressed to the intra-office device 20, so that the upstream signal does not collide with the star coupler 21. I have. Therefore, in each of the subscriber units, the downlink signal processing unit extracts the uplink signal output timing from the downlink signal separated by the transmission path transmission separation unit, and monitors whether the downlink signal has been normally processed. . The timer unit starts measuring a predetermined timing based on the upstream signal output timing extracted by the downstream signal processing unit. Then, when it is determined that the downstream signal processing unit can normally process the downstream signal, the upstream signal output timing extracted by the downstream signal processing unit,
When it is determined by the downlink signal processing unit that the downlink signal could not be processed normally, the timing measured by the timer unit is set as the transmission timing of the uplink signal.

As described above, the PDS transmission system according to the first embodiment is provided with the timer unit, and operates based on the normal uplink signal output timing notified from the intra-office device to each subscriber unit. Even when the apparatus cannot normally receive the signal output timing in the uplink direction from the intra-station apparatus, it is possible to transfer the alarm according to the timing measured by the timer unit. Thereby, the state of the alarm of the subscriber device can be appropriately notified to the intra-station device, so that the maintainability in the event of a failure can be greatly improved. Further, since no wiring is required between the subscriber units, an economical system can be constructed.

Second Embodiment

In each subscriber unit of the PDS transmission system according to the first embodiment, for example, if a failure occurs in the downstream signal output unit of the intra-office unit 20, the first to n-th subscriber units 22 _{1 to} 22 _n Since the reception of the downlink signal becomes abnormal, the subordinate synchronous relationship between the intra-station device 10 and the first to n-th subscriber devices 22 _{1 to} 22 _n is not established, and the timing is measured by the timer unit in each subscriber device. An up signal is output. However, since the oscillators that measure the time in the timer units in the respective subscriber units operate independently of each other, a frequency shift occurs with the lapse of time, and the increased shift causes each of the subscribers synthesized by the star coupler 21. There is a possibility that the uplink signal from the user device collides and the in-station device 20 cannot make the uplink signal normal. For this reason, in the second embodiment, even when a plurality of subscriber units independently transmit uplink signals at the timing measured by the timer unit, the frequency cannot be avoided by each timer unit. To provide a PDS transmission system capable of avoiding collision of signals combined by a star coupler due to the deviation of the PDS.

FIG. 2 shows the outline of the configuration of the PDS transmission system in the second embodiment. However,
The same parts as those of the PDS transmission system according to the first embodiment shown in FIG. Second
In the embodiment of the PDS transmission system, the intra-station device 2
0 is connected to the _first to _n-th subscriber units 401 to 40n via the star coupler 21.

The _first to _n-th subscriber units 40 ₁ to 40 _n are:
Each of them has the same configuration, and FIG. 2 shows only the first subscriber unit. The difference between the subscriber device in the second embodiment and the subscriber device in the first embodiment is that the first subscriber device 40 ₁ in the second embodiment is different.
As shown in the figure, the alarm signal 31 ₁ output from the downstream signal processing unit 26 _{1 is} output to the timer unit 41 as well as the selection unit 28 _1.
1 and the timer unit 41 ₁ outputs the extraction transmission timing 3
0 lies in performing counting the predetermined timing based on ₁ and the alarm signal 31 _1.

The timer section 41 ₁ in the second embodiment.
The downlink signal processing unit 26 ₁ when it can not properly process the downlink signal, by a predetermined time based on the extracted transmission timing 30 ₁ extracted by the downlink signal processor ₂₆₁ and the alarm signal 31 ₁ After performing the timing, the timing operation is stopped. Accordingly, transmission of the uplink signal is stopped by the clock timing in subsequent timer unit 41 _1.

As described above, in the PDS transmission system according to the second embodiment, when the processing of the signal in the down direction cannot be performed normally by the timer section, the timer section measures the time for a predetermined time.
Since the timer operation is stopped, after transmitting the alarm generated by the subscriber unit a certain number of times, the transmission of the uplink signal can be stopped. Even when transmitting the signal in the uplink direction at the timing measured by the unit, it is possible to avoid collision of the signal synthesized by the star coupler due to the frequency shift unavoidable in each timer unit, The alarm of the own subscriber device can be transferred without adversely affecting other subscriber devices.

[0041]

As described above, according to the first or third aspect of the present invention, even if a subscriber unit cannot normally process a signal received from an intra-office unit, each subscriber unit can receive a signal. A signal can be sent to the intra-office device without wiring between the subscriber devices, and an economical system can be constructed.

According to the second or fourth aspect of the present invention, even when a plurality of subscriber units send outbound signals at the timing measured by the timer unit independently of each other, each subscriber unit can send a signal to each of the subscriber units. It is possible to avoid collision of signals combined by a star coupler due to a frequency shift that cannot be avoided by the timer unit, and output a signal of the own subscriber device without adversely affecting other subscriber devices. be able to.

According to the fifth aspect of the present invention, at the transmission timing to the intra-office device, the alarm information for notifying the occurrence of a failure in the subscriber unit is transmitted. The status can be notified appropriately,
Maintainability in the event of a failure can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an outline of a configuration of a PDS transmission system according to a first embodiment.

FIG. 2 is a configuration diagram illustrating an outline of a configuration of a PDS transmission system according to a second embodiment.

FIG. 3 is a configuration diagram illustrating an outline of a configuration of a conventionally proposed PDS transmission system.

[Explanation of symbols]

10, 20 In-station device 11, 21 Star coupler 12 _{1 to} 12 _m First to _m- th subscriber device 13, 14 _{1 to} 14 _m , 23, 24 _{1 to} 24 _n Transmission line 15 ₁ to 15 _m Phase information transmission / reception circuit 16 phase information signal lines 22 _{1 to} 22 _n , 40 ₁ to 40 _{n first} to _n- th subscriber units 25 ₁ transmission line transmission separation unit 26 ₁ downstream signal processing units 27 ₁ , 41 ₁ timer unit 28 ₁ selection unit 29 ₁ Upstream signal processing unit 30 ₁ Extraction transmission timing 31 ₁ Alarm signal 32 ₁ Timing timing 33 ₁ Upstream signal transmission timing

Claims (5)

[Claims] 1. An intra-station device for notifying transmission timings different from each other, a star coupler for making multiple connections to the intra-station device, and a received signal from the intra-station device connected to the star coupler and being normally processed. And one or more subscriber units for transmitting a signal to the intra-station device at a transmission timing to the intra-station device measured based on a transmission timing addressed to the own device notified by the intra-station device when there is no transmission. A passive double-star transmission system, characterized in that: 2. The passive double-star transmission system according to claim 1, wherein the transmission timing is a timing based on a transmission timing addressed to the own device, and then stops after a lapse of a predetermined time. 3. An intra-station device for notifying transmission timings different from each other, a star coupler for making multiple connections to the intra-station device, and normally connected to the star coupler, and normally processing a reception signal from the intra-station device. Monitoring means for monitoring whether or not the signal has been transmitted; extracting means for extracting a transmission timing addressed to the own device from a received signal from the intra-station device; and a signal addressed to the intra-station device based on the transmission timing extracted by the extracting means. A timer means for measuring transmission timing, and when the reception signal can be normally processed as a result of monitoring by the monitoring means, sends a signal to the intra-office device according to the transmission timing extracted by the extraction means,
Signal transmitting means for transmitting a signal to the intra-office device in accordance with the transmission timing to the intra-office device measured by the timing device when the received signal cannot be processed normally; And a passive double-star transmission system. 4. The passive double-star transmission system according to claim 3, wherein said time-measuring means performs time-measurement based on a transmission timing addressed to said own device and stops after a lapse of a predetermined time. 5. The passive apparatus according to claim 1, wherein the signal output at the transmission timing to the intra-station apparatus is alarm information for notifying that a failure has occurred in the subscriber apparatus. Double star transmission system.