JPH07240912A - Optical catv transmitter - Google Patents

Abstract

PURPOSE:To simplify the installation and maintenance of an equipment by effectively utilizing an outgoing transmission band between a head end and a hub and the optical CATV transmitter and keeping an outgoing signal at a prescribed signal level at all times. CONSTITUTION:Incoming channel request signals from a subscriber 5 are summed up inside a hub 3, an area request signal is received by a light receiving part 9 and based on this area request signal, a signal selecting part 10 selects arbitrary (m) pieces of signals out of (n) pieces of outgoing signals. These selected outgoing signals are synthesized by a signal synthesizing part 11 and transmitted from a light transmitting part 8 to the subscriber 5 so that the outgoing transmission band can be effectively utilized. On the other hand, a level data signal is received by the light receiving part 9, this level data signal is compared with a prescribed signal level by a level control part 12 and the level difference of respective outgoing signals corresponding to the compared value is corrected by a variable attenuator 13 so that the outgoing signals can be kept at the prescribed signal level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical CATV transmission device suitable for effective use of downlink transmission band and simplification of equipment installation and maintenance.

[0002]

2. Description of the Related Art An optical CATV transmission device has been in high demand as an optical CATV trunk line by taking advantage of low cost and long distance transmission. Also, in recent years, a star type subscriber network represented by a hub method has been actively studied.

A conventional optical CATV transmission device will be described below. FIG. 3 is a system diagram showing a configuration of a conventional optical CATV transmission device. In FIG. 3, 1 is an optical CATV
It is a headend and has a plurality of modulators (M ₁ , M ₂ , ...
M _n ) 6 is transmitted via the mixer 7 to a plurality of optical transmitters (T ₁ , T ₂ ,
.. T _x ) 8, and the optical transmitter 8 is connected to a plurality of hubs (H ₁ , H ₂ , ... H _y ) 3 via the transmission line 2. Each of the hubs 3 is connected to a plurality of subscribers (K ₁ , K ₂ , ..., K _z ) 5 on a one-to-one _basis via a star-shaped subscriber network 4, and FIG. 3 shows only the hub H ₁ . Shows.

Next, an outline of the operation will be described. Optical CATV
Downstream video signals of several hundred channels are transmitted from the optical transmitter 8 of the headend 1 to each hub 3 via a transmission line (for example, an optical fiber) 2. The hub 3 and the subscribers 5 have a one-to-one correspondence with the star-shaped subscriber network 4 composed of optical fibers or coaxial lines.
It is connected to and has a configuration capable of bidirectional transmission. The channel request allows the subscriber 5 to select any number of channels from the hundreds of downlink video signals transmitted to the hub 3, which is advantageous in that the confidentiality is improved.

[0005]

However, in the above-mentioned conventional configuration, the optical CATV headend 1 transmits the same downlink signal to each hub 3, so that a channel with a low audience rating is also transmitted to all the hubs. Must. Therefore, there is a first problem that the downlink transmission band cannot be effectively used.

Further, in the conventional configuration, a pilot signal is provided in the band and the signal level is monitored to monitor all downlink signals. Therefore, there is a second problem that all signals within the band cannot be monitored accurately.

SUMMARY OF THE INVENTION The first object of the present invention is to provide an optical CATV transmission device capable of effectively utilizing the downlink transmission band between the headend and the hub in order to solve the above-mentioned first problem.

Further, the present invention solves the above-mentioned second problem of the prior art, and provides an optical CATV transmission apparatus which can maintain the downlink signal at a predetermined signal level at all times and greatly simplify the installation and maintenance of the equipment. The second purpose is provision.

[0009]

In order to achieve the above first and second objects, the present invention provides a hub for summing up upstream channel request signals from a subscriber network and each of a plurality of downstream signals. An optical CATV headend for selecting a downlink signal corresponding to a request from a subscriber and transmitting it to each subscriber.

Further, as a first means for achieving the first object, the optical CATV headend receives an area request signal created by summing up upstream channel request signals from subscribers in the hub. Section, a signal selecting section for selecting an arbitrary m number of n downlink signals based on the area request signal received by the optical receiving section, and a signal combining section for combining the downlink signals selected by the signal selecting section. And having.

As a second means for achieving the second object, the hub has a level detecting section for detecting the signal level of each transmission band, and the optical CATV headend includes:
An optical receiving unit that receives an area request signal created by summing up upstream channel request signals from subscribers in the hub, and an arbitrary m from n downlink signals based on the area request signal received by the optical receiving unit. In addition to the signal selecting unit for selecting the number and the signal combining unit for combining the downlink signals selected by the signal selecting unit, the level data signal detected by the level detecting unit in the hub is received by the optical receiving unit, A level control unit for comparing the level data signal with a predetermined signal level and outputting the comparison value; and a variable attenuating unit for correcting the level difference between the downlink signals corresponding to the comparison value. To do.

[0012]

According to the present invention, the optical CATV is realized by the first means.
Based on the area request signal received by the optical reception unit of the headend, the signal selection unit selects any m from the n downlink signals, the selected downlink signals are combined by the signal combination unit, and the optical transmission is performed. Since the transmission is performed from the department to the subscriber, the downlink transmission band can be effectively used and the number of channels that the subscriber can select can be increased.

The second means detects the signal level in the level detecting section in the hub, receives the level data signal in the optical receiving section of the optical CATV headend, and outputs the level data signal and the predetermined signal. The level control unit compares the levels and the level difference of each downlink signal corresponding to the comparison value is corrected by the variable attenuation unit, so the downlink signal is always maintained at a predetermined signal level, and equipment installation and maintenance is performed. Can be greatly simplified.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an optical CA according to a first embodiment of the present invention.
It is a system diagram which shows the structure of a TV transmission apparatus. In the optical CATV headend 1 shown in FIG. 1, 9 is an optical receiving unit for receiving an area request signal created by summing up upstream channel request signals from the subscriber 5 in the hub 3, and 10 is an area received by the optical receiving unit 9. A signal selection unit that selects an arbitrary m signal from the n downlink signals based on the request signal,
Reference numeral 11 denotes a signal combining unit that combines the downlink signals selected by the signal selecting unit 10.

In addition, the same components as those shown in FIG. 3 of the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

As a simple example of the optical CATV transmission apparatus configured as described above, the operation will be described for the case where only one hub is installed in each area.

The upstream channel request signals from the subscriber 5 transmitted via the subscriber network 4 are totaled by the hub 3,
It transmits to the optical CATV headend 1 via the transmission line 2 as an area request signal which is a collection of request channels of the corresponding area. The area request signal is separated in the optical CATV headend 1, converted into an electric signal by the optical receiving section 9, and input to the signal selecting section 10. The signal selection unit 10 controls the signal synthesis unit 11 based on the area request signal,
Arbitrary m signals are selected and combined from the n downlink signals and input to the optical transmitter 8 in the corresponding area. However, m <n.

The downlink signal is transmitted from the optical transmitter 8 to the hub 3 via the transmission line 2, and the hub 3 allocates the downlink signal to each subscriber according to the uplink channel request signal transmitted from the subscriber 5. As a result, each subscriber can view any downlink signal. In this case, the downlink signal is often a video signal, but may also transmit various signals such as a data signal.

As described above, according to the first embodiment of the present invention, the upstream channel request signals from the subscribers are aggregated by the hub and transmitted as an area request signal to the optical CATV headend to obtain the area request signal. Based on the above, the signal selecting unit and the signal synthesizing unit synthesize arbitrary m signals from the n downlink signals and transmit them from the optical transmitting unit to the hub, and the hub responds to each uplink channel request signal transmitted from the subscriber. By allocating a downlink signal to a subscriber, it is possible to provide an optical CATV transmission device that can effectively utilize the downlink transmission band and increase the number of channels that the subscriber can select.

FIG. 2 shows the light C in the second embodiment of the present invention.
It is a system diagram which shows the structure of an ATV transmission apparatus. In FIG. 2, 12 in the optical CATV headend 1 receives the level data signal detected by the level detecting section 14 in the hub 3 by the optical receiving section 9 and compares the level data signal with a predetermined signal level. Level control unit that outputs the comparison value,
Reference numeral 13 is a variable attenuator that corrects the level difference between the downlink signals corresponding to the comparison value output from the level controller 12, and 14 is a level detector that detects the signal level.

In addition, the same components as those shown in FIG. 1 of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As a simple example of the optical CATV transmission apparatus configured as described above, the operation will be described for the case where only one hub is installed in each area.

The upstream channel request signals from the subscriber 5 transmitted via the subscriber network 4 are totaled by the hub 3,
It transmits to the optical CATV headend 1 via the transmission line 2 as an area request signal which is a collection of request channels of the corresponding area. The area request signal is separated in the optical CATV headend 1, converted into an electric signal by the optical receiving section 9, and input to the signal selecting section 10. The signal selection unit 10 controls the signal synthesis unit 11 based on the area request signal,
Arbitrary m signals are selected and combined from the n downlink signals and input to the optical transmitter 8 in the corresponding area. However, m <n.

The downlink signal is transmitted from the optical transmitter 8 to the hub 3 via the transmitter 2, and the hub 3 allocates the downlink signal to each subscriber according to the uplink channel request signal transmitted from the subscriber 5. As a result, each subscriber can view any downlink signal. In this case, the downlink signal is often a video signal, but may also transmit various signals such as a data signal. The above is the same as in the first embodiment.

At this time, the level detector 14 in the hub 3 detects the signal level of each transmission band and transmits it as a level data signal to the optical CATV headend 1 via the transmission line 2. However, the signal in the signal detection band is an unmodulated signal and is excluded from the signal band temporarily supplied to the subscriber during the signal level detection period. The level data signal is separated in the optical CATV headend 1, converted into an electric signal by the optical receiving unit 9, and input to the level control unit 12. This level control unit 12
Compares the level data signal with a predetermined signal level and controls the variable attenuator 13 based on the comparison value to correct the level difference of the downlink signal.

As described above, according to the second embodiment of the present invention, in addition to the function of the first embodiment, the signal level of each signal band is detected by the level detection in the hub to obtain the level data. By transmitting the signal as a signal to the level control unit in the optical CATV headend through the transmission line and controlling the variable attenuator, it is possible to maintain a predetermined signal level at all times, which greatly reduces the installation and maintenance of the device. Can be simplified.

[0027]

As described above, the optical CAT of the present invention is used.
The V transmission device collects the upstream channel request signals from the subscribers at the hub and uses the optical C as an area request signal.
The signal is transmitted to the ATV headend, and based on the area request signal, the signal selecting unit and the signal synthesizing unit synthesize m arbitrary n signals from the n downlink signals, and the optical transmitting unit transmits them to the hub. By allocating the downlink signal according to the uplink channel request signal transmitted from, the downlink transmission band can be effectively used and the number of channels that the subscriber can select can be increased.

Further, the level detecting section in the hub detects the signal level of each transmission band and transmits it as a level data signal to the level control section in the optical CATV headend through the transmission line to control the variable attenuating section. By doing so, it is possible to maintain a predetermined signal level at all times, and equipment and maintenance of the equipment can be greatly simplified.

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration of an optical CATV transmission device according to a first embodiment of the present invention.

FIG. 2 is a system diagram showing a configuration of an optical CATV transmission device according to a second embodiment of the present invention.

FIG. 3 is a system diagram showing a configuration of a conventional optical CATV transmission device.

[Explanation of symbols]

1 ... Optical CATV head end, 2 ... Transmission line, 3 ... Hub, 4 ... Subscriber network, 5 ... Subscriber, 6 ... Modulator, 7
... mixer, 8 ... optical transmitter, 9 ... optical receiver, 10 ... signal selector, 11 ... signal combiner, 12 ... level controller, 13
… Variable attenuator, 14… Level detector.

Claims (3)

[Claims] 1. A hub that aggregates upstream channel request signals from a subscriber network, and an optical CATV that selects a downlink signal corresponding to a request from each subscriber from a plurality of downlink signals and transmits the selected downlink signal to each subscriber. An optical CATV transmission device having a head end. 2. The optical CATV headend receives an area request signal created by summing up upstream channel request signals from subscribers in the hub, and an area request signal received by the optical receiving section. 2. The signal selecting section for selecting an arbitrary m number from the n downlink signals based on the above, and a signal combining section for combining the downlink signals selected by the signal selecting section. Optical CATV transmission device. 3. The hub has a level detecting unit for detecting a signal level of each transmission band, and the optical CATV headend collects and prepares an upstream channel request signal from a subscriber in the area. An optical receiving unit that receives a request signal, a signal selecting unit that selects an arbitrary m number of downlink signals based on the area request signal received by the optical receiving unit, and a downlink selected by the signal selecting unit. In addition to the signal synthesizer that synthesizes signals, the optical receiver receives the level data signal detected by the level detector in the hub, compares the level data signal with a predetermined signal level, and outputs the comparison value. 2. The optical CATV according to claim 1, further comprising a level control unit for controlling the level difference, and a variable attenuator for correcting the level difference between the downlink signals corresponding to the comparison value.
Transmission equipment.