JP2006115013A - Optical transmission apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmission apparatus capable of transmitting a signal with high quality at a low cost. <P>SOLUTION: The optical transmission apparatus for respectively receiving a first high frequency signal and a second high frequency signal whose frequency band is higher than that of the first high frequency signal, mixing the first and second high frequency signals, converting the mixed signal into an optical signal and outputting the optical signal from one output, includes an optical receiver for receiving a first optical signal resulting from optically converting a high frequency signal part or all of which is overlapped with the first high frequency signal and converting the optical signal into a third high frequency signal; and a switching means configured to freely switch passing of the first high frequency signal or passing of the third high frequency signal and to pass either of them, the first high frequency signal or the third high frequency signal is selectively switched by the switching means and thereafter the selected signal is mixed with the second high frequency signal, and the mixed signal is converted into an optical signal and outputted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an optical transmission apparatus mainly used in a CATV system, and more particularly to a configuration of the optical transmission apparatus.

Conventionally, the CATV system of the HFC transmission system transmits a downstream signal from the CATV center to the vicinity of a subscriber's house such as an individual or a condominium through a downstream optical transmission line, and an optical / electric conversion device (so-called node type optical transmission / reception) The downstream signal is transmitted to each subscriber's house via a coaxial cable, and the upstream signal from the subscriber's house is also transmitted using the same coaxial cable. After the conversion, the data is transmitted to the CATV center through the upstream optical transmission line.
In addition, as a distribution system in the building on the subscriber side, a high-frequency signal as a downstream signal is distributed using a booster, a branching device, a distributor, etc., or a downstream high-frequency signal drawn into the building is optically transmitted. An example of constructing an optical system that converts an optical signal into an optical signal and distributes it individually by an apparatus has increased.
In addition, satellite antennas and UHF antennas are installed in buildings so that they can receive services by directly receiving satellite broadcasts such as BS and CS, and digital terrestrial broadcasts, and these signals are mixed with signals from CATV transmission lines. As a result, the number of distribution systems in the building has increased.
(For example, see Patent Document 1)

JP 2001-231023 A

However, in such a conventional HFC transmission system, for example, a downlink signal is transmitted through a high-frequency transmission line in which a trunk amplifier or the like is cascaded because a high-frequency signal output from a node is transmitted. May deteriorate, which has been a cause of service quality degradation.
For this reason, there is a problem that if the nodes are subdivided in order to improve the quality of service, the cost of the system is involved.
Further, it is conceivable to double the CATV system so as to cope with the case where the signal from the CATV center station stops for some reason, but there is a problem that the construction becomes complicated and the cost is increased.
Therefore, in the present application, it was made to solve such problems,
An object of the present invention is to provide an optical transmitter capable of transmitting a high-quality signal without incurring costs.
Another object is to stop the optical signal from the CATV center station that outputs the optical signal from the CATV center station and the high-frequency signal from the antenna for receiving terrestrial broadcasting or satellite broadcasting as one optical signal. It is an object of the present invention to provide an optical transmitter capable of transmitting a terrestrial broadcast signal.

In order to solve the above problems, the invention of claim 1 is configured such that a first high-frequency signal and a second high-frequency signal having a frequency band higher than that of the first high-frequency signal are input. In an optical transmitter configured to mix a first high-frequency signal and the second high-frequency signal, convert the mixed high-frequency signal into an optical signal, and output from one output,
An optical receiver that inputs a first optical signal obtained by optically converting a high-frequency signal that partially or entirely overlaps with the first high-frequency signal, and converts the input optical signal into a third high-frequency signal; Switching means configured to switch between allowing the first high-frequency signal to pass or the third high-frequency signal to pass, and passing either one of the high-frequency signals. The high-frequency signal or the third high-frequency signal is selectively switched by the switching means, mixed with the second high-frequency signal, converted into an optical signal, and output.

According to a second aspect of the present invention, in the optical transmission device according to the first aspect, the switching means uses a signal level of the first optical signal as a criterion for determination, and the first optical signal is transmitted to the optical receiver in a predetermined manner. When the level does not reach, the first high-frequency signal is allowed to pass. When the first optical signal is inputted to the optical receiver at a predetermined level or higher, the third high-frequency signal is allowed to pass. Composed.

According to a third aspect of the present invention, in the optical transmission device according to the first aspect, the switching means uses the predetermined signal included in the first optical signal as a determination criterion, and is included in the first optical signal. When the predetermined signal is not at the specified value, the first high-frequency signal is allowed to pass, and when the predetermined signal included in the first optical signal is at the specified value, the third high-frequency signal is allowed to pass. Configured.

According to a fourth aspect of the present invention, in the optical transmission device according to any one of the first to third aspects, the first optical signal is a downstream optical signal transmitted from a CATV center station. The high frequency signal is configured to be in an intermediate frequency band output from the satellite antenna.

According to the first aspect of the present invention, the first high-frequency signal and the second high-frequency signal having a frequency band higher than that of the first high-frequency signal are input, respectively, and the first high-frequency signal and In the optical transmitter configured to mix the second high-frequency signal, convert the mixed high-frequency signal into an optical signal, and output from one output,
An optical receiver that inputs a first optical signal obtained by optically converting a high-frequency signal that partially or entirely overlaps with the first high-frequency signal, and converts the input optical signal into a third high-frequency signal; Switching means configured to switch between allowing the first high-frequency signal to pass or the third high-frequency signal to pass, and passing either one of the high-frequency signals. Since the high-frequency signal or the third high-frequency signal is selectively switched by the switching means and then mixed with the second high-frequency signal, it is converted into an optical signal and output.
The first optical signal can be directly input via an optical fiber without passing through a high-frequency amplifier or the like, and the C / N of the signal is reduced by transmitting the high-frequency signal through a transmission line that cascades the high-frequency amplifier or the like. It is possible to provide an optical transmission device that does not deteriorate the quality of a transmission signal that would deteriorate.
Further, even if the first optical signal (so-called third high-frequency signal) is stopped, at least the first high-frequency signal that partially or entirely overlaps with the third high-frequency signal can be input. Thus, even if the first optical signal is stopped, the switching means switches the transmission path, thereby providing a convenient optical transmitter that does not stop.

According to a second aspect of the present invention, in the optical transmission device according to the first aspect, the switching means uses the signal level of the first optical signal as a judgment criterion, and the first optical signal is the optical receiver. When the predetermined level is not reached, the first high-frequency signal is allowed to pass. When the first optical signal is input to the optical receiver at a predetermined level or higher, the third high-frequency signal is allowed to pass. Because it was configured as
For example, even when a service is received by the first optical signal and a shortage occurs such as an optical fiber cut or an optical transmitter failure, the transmission line is automatically switched by the switching means 11. By switching, it is possible to provide an optical transmission device that can respond quickly so that at least a signal from the first high-frequency signal can be received.

According to a third aspect of the present invention, in the optical transmission device according to the first aspect, the switching means uses a predetermined signal included in the first optical signal as a determination criterion and is included in the first optical signal. When the predetermined signal is not at a specified value, the first high-frequency signal is allowed to pass, and when the predetermined signal included in the first optical signal is at a specified value, the third high-frequency signal is allowed to pass. Because it was configured to
For example, when the pilot signal included in the first optical signal is detected, the line state of the optical fiber transmitting the first optical signal is accurately determined, and the state of the first optical signal is bad By automatically switching the switching means, it is possible to provide an optical transmission device that can respond quickly so that at least the first high-frequency signal can be received.

According to a fourth aspect of the present invention, in the optical transmission device according to any one of the first to third aspects, the first optical signal is a downstream optical signal transmitted from a CATV center station. Since the high frequency signal of 2 is configured to be an intermediate frequency band output from the satellite antenna,
Not only can you receive multi-channel (first optical signal) services, including independent broadcasting, terrestrial broadcasting, and satellite broadcasting via the CATV network, but you can join even if the signal from the CATV network stops. It is possible to provide an optical transmission device that can be switched quickly so that direct reception (first high-frequency signal that is terrestrial broadcasting, second high-frequency signal that is satellite broadcasting) can be performed using an antenna installed in a house.

Hereinafter, an example of an embodiment embodying the present invention will be described in detail with reference to the drawings.
Fig.1 (a) is a schematic block diagram which shows the Example of this application. (B) shows another embodiment. 2 is a schematic explanatory diagram showing an example of a CATV system using the optical transmission device of the present application. FIG. 3 is a block diagram showing an example of a conventional CATV system.

An embodiment of the optical transmission device 1 according to the present invention will be described with reference to FIG. Reference numeral 2 is configured as an RF signal input terminal for inputting a high-frequency signal, and the high-frequency signal input from this input terminal is input to the high-frequency signal switching means shown in 11.
For example, a signal in a frequency band of 70 to 770 MHz is input to this input terminal, and this signal indicates the first high-frequency signal described in the claims. In the embodiment of the present application, for example, a signal of VHF and UHF bands is input.

Reference numeral 3 denotes an input terminal for inputting a second high frequency signal that is higher in frequency than the first high frequency signal and does not overlap with each other. In the embodiment of the present application, for example, a signal in the BS / CS-IF band is used. BS-IF input terminal for inputting, BS / CS-IF band signal input from the input terminal is input to an amplifier 15 composed of a transistor or IC, and the amplifier 15 has a predetermined level. And then input to the mixer 13.
The signal in the BS / CS-IF band in this embodiment is, for example, a signal in the frequency band of 1032 to 2602 MHz, and this signal indicates the second high-frequency signal in the claims.

Reference numeral 4 denotes an input terminal for inputting a first optical signal. In the embodiment of the present application, for example, an optical signal from a CATV transmission network for transmitting an optical signal from a CATV center station via an optical fiber cable is input. CATV downstream optical signal input terminal. The optical signal input from the input terminal 4 is converted into a high-frequency signal by an optical receiver 16 that converts the optical signal into a high-frequency signal, and then input to the switching unit 11.
The CATV downstream optical signal uses, for example, a signal having a wavelength band of 1.31 μm band or 1.55 μm band, and this optical signal indicates the first optical signal described in the claim hole. The high-frequency signal output from the optical receiver 16 is a signal in a frequency band of, for example, 70 to 770 MHz, and this high-frequency signal indicates the third high-frequency signal in the claims.

The switching means 11 is configured to switch between whether to pass the first high-frequency signal or to pass the third high-frequency signal so that either one of the high-frequency signals is passed. For example, a mechanical changeover switch or an electronic switch constituted by a pin diode or the like is changed over by the operation means 17.
The first high-frequency signal or the third high-frequency signal input to the switching unit 11 is input to a high-frequency amplifier 12 configured by a transistor or an IC after the transmission unit is selectively switched by the switching unit 11. Then, after being amplified to a predetermined level in the amplifier 12, it is input to the mixer 13.
In this way, the second high-frequency signal input to the mixer 13 and the first high-frequency signal or the third high-frequency signal selectively input are mixed in the mixer 13. After being converted into an optical signal by the optical transmitter 14 for converting a high-frequency signal into an optical signal, it is output from the downstream optical signal output terminal 5 shown in FIG.

Next, another embodiment according to the optical transmission apparatus of the present application will be described. In this embodiment, as a switching determination unit of the switching unit 11, a predetermined signal included in the first optical signal is detected and determined, and the switching unit 11 is set to the first high frequency on the basis of this determination criterion. The transmission path for allowing the signal to pass or the third high-frequency signal to pass is automatically determined and switched.
The predetermined signal at this time may be a pilot signal generated in the center station, or may be a specific signal included in the broadcast signal, and is not particularly limited.
In this embodiment, an optical receiver 16 having a photodiode is provided with a detection circuit such as a pilot signal to detect a reference signal, and the detected signal is determined by the control means 18 and predetermined based on this signal. Thus, the switching means 11 is configured to switch the transmission path.

Next, an outline of a CATV system provided with the optical transmission apparatus 1 of the present invention is shown in FIG. 2, and the optical transmission apparatus 1 and the system will be described in detail.
Reference numeral 30 denotes a CATV center station, and a signal received by a ground broadcast antenna 30a such as VHF or UHF, a BS / 110 ° satellite antenna 30b, or the like is input to the headend device 31 and has a frequency band of, for example, 70 to 770 MHz. After each signal is processed so as to be suitable for transmission or mixed with a pilot signal, it is converted into a downstream optical signal by optical transmitters 32, 32... That convert this high frequency signal into an optical signal. It is transmitted via optical fiber cables 33, 33.
In the CATV system of the present application, the downstream optical signal is configured using an optical signal having a wavelength such as a 1.31 μm band or a 1.55 μm band. It is an optical signal.
Further, the upstream optical signal is input to the optical receivers 36, 36... Of the center station via the optical fiber cables 35, 35. This optical receiver is connected to a center modem 37 and a router 38, and the center station 30 is connected to a WAN (Wide Area Network) 40. In order to clarify the description of the present application, detailed description of the upstream optical signal is omitted.

In FIG. 2, reference numeral 50 denotes a building such as an apartment, and 51a, 51b,... Denote individual subscriber homes having terminal terminals.
The CATV downstream optical signal (first optical signal) drawn into the condominium 50 via the optical fiber cable 33 is the CATV downstream of the optical transmitter 1 connected to the optical fiber 7 installed in the condominium or the like. Input from the optical signal input terminal 4. In addition, the building 50 such as an apartment is provided with an antenna 50a for receiving terrestrial broadcast waves such as VHF and UHF, and the signal (first high frequency signal) received by the terrestrial broadcast antenna 50a is Input from the RF signal input terminal 2 of the optical transmitter 1. At this time, when receiving both a signal of 90 to 222 MHz which is a frequency band of the VHF band and a signal of 470 to 770 MHz which is a frequency band of the UHF band, a signal obtained by mixing the outputs from the respective antennas with a mixer. Pull in with a single coaxial cable.
Further, the building 50 is provided with a satellite antenna 50b capable of receiving, for example, BS and 110 ° CS. In the embodiment of the present application, a signal in the intermediate frequency band of 1032 to 2602 MHz (second high frequency signal) is an optical transmitter. 1 from the BS / CS-IF input terminal 3.

The CATV downstream optical signal input to the optical transmitter 1 is converted into a third high-frequency signal by the optical receiver 16 incorporated in the optical transmitter 1. For one high frequency signal, the switching means 11 selectively switches the transmission path, and one of the high frequency signals is output from the switching means 11. Further, the third high-frequency signal or the first high-frequency signal output from the switching unit 11 is amplified to a predetermined level by the amplifier 12 and then passed through the second input transmission path in the mixer 13. Mixed with the signal. The mixed high-frequency signal is converted into an optical signal by the optical transmitter 14 and then transmitted from the downstream optical signal output terminal to the optical fiber 7 disposed inside the building.
The downstream optical signal transmitted through the optical fiber 7 is output from the terminal 9 after being converted into a high-frequency signal by the optical receiver 8 installed in the subscriber premises 51a through the optical distributor 6, the optical fiber 7, and the like. The

In the above system, since the third high frequency signal is configured to be a transmission band (70 to 770 MHz in the embodiment of the present application) of the high frequency signal of the CATV system to which it is subscribed, Are both the third high-frequency signal which is the CATV downlink high-frequency signal of 70 to 770 MHz and the signal of 90 to 222 MHz which is the VHF band and 470 to 770 MHz which is the UHF band received by the ground wave antenna 50a. Alternatively, the first high-frequency signal that is one of the signals is drawn, and the transmission path of these high-frequency signals is selectively switched in the switching means 11.

That is, in the building CATV system using the optical transmitter 1 of the present application, the optical transmitter 1 is provided with the optical receiver 16 for converting the CATV downstream optical signal into a high frequency signal. As shown in FIG. 3, for example, the high-frequency signal output from the node passes through a high-frequency transmission line cascaded with a trunk amplifier or the like as in the conventional HFC transmission method shown in FIG. As a result, the C / N of the signal deteriorates and the service quality does not deteriorate.
Further, since it is not necessary to subdivide the nodes in order to improve the quality of service, the problem of increasing the system cost can be solved.

In addition, the optical transmission device 1 of the present application is configured to be able to selectively input and transmit the third high-frequency signal and the first high-frequency signal. This is a case where a multi-channel service is received by the CATV downstream optical signal that is the first optical signal input via the road, and there is a shortage such as optical fiber disconnection or center station equipment failure. However, the first high-frequency signal from the terrestrial antenna 50a installed in the building 50 such as a condominium is switched automatically or manually by the switching means 11 provided in the optical transmitter 1 and the transmission path is switched. Even when the signal from the CATV is cut off or the state is deteriorated, at least the terrestrial antenna 5 is configured to pass the signal. It is the is no longer said that at all can not receive the TV so it can receive the signal from a.
In addition, since the signal from the BS · 110 ° CS satellite antenna 50b can also be input, the in-building CATV system equipped with the optical transmission device 1 can enjoy a multi-channel service including satellite broadcasting by CATV. In addition, the subscriber can select a method of directly receiving satellite broadcasts, and can build a reception system that expands the range of service selection.
If an optical signal in the 1.55 μm band is used as an optical signal used in the optical transmitter 1 and the CATV system of the present application, amplification distribution by an EDFA (Erbium Doped Fiber Amplifier) can be performed. It is possible to provide an optical transmission apparatus and a CATV system that are highly advantageous in that the cost of the system can be reduced.

In addition, this invention is not limited to the said embodiment, It is also possible to change and implement the structure of each part suitably.

(A) An example of the embodiment of the optical transmitter according to the present invention is shown, and (b) shows a different embodiment. It is a schematic block diagram of an example of the CATV system using the optical transmitter of this application. The schematic block diagram of an example of the conventional CATV system is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical transmitter, 2 ... RF signal input terminal, 3 ... BS * CS-IF input terminal, 4 ... CATV downstream optical signal input terminal, 5 ... Downstream signal output terminal, 6 ... Optical splitter, 7 ... Optical fiber, DESCRIPTION OF SYMBOLS 8 ... Optical receiver, 9 ... Television terminal, 10 ..., 11 ... Switching means, 12 ... Amplifier, 13 ... Mixer, 14 ... Optical transmitter, 15 ... Amplifier, 16 ... Optical receiver, 17 ... Operating means, 18 Control means, 19 ..., 20 ... Node type optical transceiver, 21 ... Coaxial cable, 22 ... Trunk distribution amplifier, 23 ... Trunk branch amplifier, 24 ... Branch amplifier, 25 ... Tap-off, 26 ... Guard, 30 ... CATV center 30a ... terrestrial antenna, 30b ... satellite antenna, 31 ... head end device, 32 ... optical transmitter, 33 ... optical fiber cable, 35 ... optical fiber cable, 36 ... optical receiver, 37 ... center modem, 3 ... router, 40 ... WAN, 50 ... subscribers, 50a ... terrestrial antenna, 50b ... satellite antenna, 51a · 51b ··· ... private homes, 100 ... optical transmitter

Claims (4)

The first high-frequency signal and the second high-frequency signal having a frequency band higher than that of the first high-frequency signal are input, and the first high-frequency signal and the second high-frequency signal are mixed. In the optical transmitter configured to convert the mixed high-frequency signal into an optical signal and output it from one output,
An optical receiver that inputs a first optical signal obtained by optically converting a high-frequency signal that partially or entirely overlaps with the first high-frequency signal, and converts the input optical signal into a third high-frequency signal;
Switching means configured to switch between whether to pass the first high-frequency signal or to pass the third high-frequency signal, and to pass either one of the high-frequency signals;
The first high-frequency signal or the third high-frequency signal is selectively switched by the switching means and then mixed with the second high-frequency signal and then converted into an optical signal and output. An optical transmitter characterized by the above.
The switching means uses the signal level of the first optical signal as a criterion, and passes the first high-frequency signal when the first optical signal does not reach the predetermined level to the optical receiver. 2. The optical transmission device according to claim 1, wherein the third high-frequency signal is allowed to pass when the first optical signal is input to the optical receiver at a predetermined level or more. 3.
The switching means uses a predetermined signal included in the first optical signal as a criterion, and passes the first high-frequency signal when the predetermined signal included in the first optical signal is not within a specified value. The optical transmission device according to claim 1, wherein when the predetermined signal included in the first optical signal is at a specified value, the third high-frequency signal is allowed to pass.
The first optical signal is a downstream optical signal transmitted from a CATV center station, and the second high-frequency signal is an intermediate frequency band output from a satellite antenna. 4. The optical transmission device according to any one of 3.

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