JP4718799B2 - CATV optical transmission apparatus and optical transmission system using the apparatus - Google Patents

Description

  The present invention relates to a CATV (Cable Television) optical transmission apparatus and an optical transmission system using the apparatus, and more particularly to an improvement of a CATV optical transmission apparatus using an HFC (Hybrid Fiber / Coax) transmission path (optical coaxial hybrid transmission path). .

  A CATV optical transmission apparatus using an HFC transmission line is known. FIG. 6 is a configuration diagram of an example of a CATV optical transmission apparatus using a conventional HFC transmission line.

  Referring to the figure, an example of a conventional CATV optical transmission device using an HFC transmission line is a center 101, a closure 102, a CATV optical transmission device 103, a tap-off 4, subscriber homes 8 and 9, and transmission. Path 6, 61 and 62.

  The center 101 includes a head end 105. The home 8 is provided with a home terminal (hereinafter referred to as HT) 10a and a television (hereinafter referred to as TV) 11a, and the home 9 is provided with an HT 10b, a TV 11b, and a cable modem (hereinafter CM). 14) and a personal computer (hereinafter referred to as PC) 50 are provided.

  The transmission path 6 is an optical transmission path (hereinafter referred to as an optical fiber), and the transmission paths 61 and 62 are coaxial transmission paths.

  Then, the image and the CM signal having a wavelength of 1.31 μm are transmitted through the single optical fiber 6 (from the center 1 to the home 8 and 9 directions), and the image and CM signal are transmitted through the other single optical fiber 6 (from the home 8 and 9 to the center (One direction) A CM signal having a wavelength of 1.31 μm was transmitted.

  Further, the downstream optical signal is converted into an electrical signal by the CATV optical transmission device 103 and transmitted to each of the homes 8 and 9, and the upstream electrical signal is converted into an optical signal by the CATV optical transmission device 103 and sent to the center 101. Had been sent.

  Conventional CATV optical transmission systems have provided video services and commercial Internet communication services in HFC systems. Recently, however, FTTH ((Fiber To The Home) system has become popular, and CATV is considering FTTH systems to secure users. Operators are increasing.

  As an operator, since a CATV transmission line has already been installed, communication between the OLT (Optical Line Terminal) in the center and the ONT (Optical Network Terminal) in the home can be performed while effectively using this transmission line. It is necessary to prepare equipment.

  On the other hand, Patent Document 1 discloses a technique for performing high-speed data transmission by inserting a WDM (wavelength division multiplexing) coupler into an optical transmission line corresponding to a center facility or a node optical device.

JP2003-009112A (summary, paragraph 0023)

  However, when the conventional CATV optical transmission system is completely shifted to FTTH, there is a problem that the initial investment amount becomes very large because it is necessary to install the optical fiber from the center to the ONT in the home. Further, the technique disclosed in Patent Document 1 is provided with one WDM coupler in each transmission line, and one WDM coupler (WDM filter 26, see FIG. 3) is provided in the CATV optical transmission apparatus as in the present invention. The configuration, operation, and effect are completely different from those provided only.

  Accordingly, an object of the present invention is to provide a CATV optical transmission apparatus capable of simultaneously performing a video signal and CM communication and OLT-ONT communication using an FTTH system, and capable of effectively utilizing an existing HFC system, and its An object of the present invention is to provide an optical transmission system using the apparatus.

In order to solve the above problems, a CATV optical transmission apparatus according to the present invention inputs a first signal based on an optical signal from a center through an optical transmission line , converts the input first signal into an electric signal, and transmits a coaxial signal. Are transmitted to each home via the optical signal, and a second signal based on an electrical signal from each home is input via the coaxial transmission line, and the input second signal is converted into an optical signal and transmitted via the optical transmission line. a CATV optical transmission device for transmitting to said center Te, the wavelength of the first signal by the optical signal from the center, and the wavelength of the third signal by the optical signal from the center, by the optical signal from each home Filter means for frequency-dividing and multiplexing the wavelength of the fourth signal and transmitting it to each home or the center .

  An optical transmission system according to the present invention includes the optical transmission device.

  According to the present invention, it is possible to add an FTTH system to a conventional HFC system by providing filter means in the CATV optical transmission apparatus.

  According to the present invention, it is possible to perform OLT-ONT communication using FTTH using an existing CATV system. The reason is that an optical fiber for PON (Passive Optical Network) has already been output to the closure.

  Further, even when it is desired to newly perform communication by PON, it is not necessary to install all optical fibers from the center to the ONT, and it is only necessary to newly install from the closure to the ONT in each home. The reason is the same as above. If the number of branches is to be increased or decreased, an optical coupler can be used.

  Also, it is possible to smoothly convert an existing CATV system to FTTH. The reason is that by installing the CATV optical transmission device according to the present invention in the HFC transmission line already constructed by the CATV operator, a PON system can be added on the HFC transmission line, and in addition to video and CM transmission, ONT This is because the transmission by the network becomes possible at the same time, and the existing system can be used effectively.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of an example of a CATV optical transmission system according to the present invention. In the figure, the same components as those in FIG. 6 described above are denoted by the same reference numerals, and the description thereof is omitted.

  Referring to FIG. 1, the CATV optical transmission system according to the present invention is different from the conventional CATV transmission system in that the head end 5 in the center 1, the closure 2, the configuration of the CATV optical transmission apparatus 3, and the ONT 12 a in the home 8. PC 13a is provided.

  Another difference is that an optical fiber 7 for downlink / uplink communication is laid from the CATV optical transmission apparatus 3 to the ONT 12a of the home 8 via the closure 2.

  The closure 2 between the optical cables is a storage such as a splice for connecting and branching optical fibers. The tap-off 4 is for distributing the video / CM signal on the transmission path 61 to each home.

  That is, in this CATV optical transmission system, between the center 1 and the homes 8 and 9, a video / CM communication transmission path (optical transmission path + coaxial transmission path) and an OLT-ONT communication transmission path (all optical transmission lines). Both of them are laid.

  Video / CM communication between the center 1 and the homes 8 and 9 is performed via the center 1, the optical fiber 6, the closure 2, the CATV optical transmission device 3, the coaxial transmission line 61, the tap-off 4, and the coaxial transmission line 62. OLT-ONT communication is performed via the center 1, the optical fiber 6, the closure 2, the CATV optical transmission device 3, and the optical fiber 7 for downlink / uplink communication.

  Next, an exemplary configuration of the head end 5 in the center 1 will be described. FIG. 2 is a configuration diagram of an example of the center 1, specifically showing the configuration of the head end 5.

  Referring to the figure, the center 1 includes an OLT 41, a TVSP (video signal transmitter) 15, a coupler 46, an FTX (optical transmitter) 17, a WDM (Wavelength Division Multiplexing) filter 19, and an HM (head end modem). ) 44 and an RRX (optical receiver) 39. An optical fiber 21 is the optical fiber 6 described above.

  Then, a downstream light wavelength of 1.55 μm (hereinafter referred to as downstream 1.55 μm) for video / CM communication, and an optical wavelength of 1.49 to 1.61 μm (20 nm interval 8) for upstream CWDM (Coarse Wavelength Division Multiplexing) transmission. 1 wave selection (hereinafter referred to as upstream CWDM) is used, and downstream optical wavelength 1.49 μm (hereinafter referred to as downstream 1.49 μm) and upstream light for OLT-ONT communication. A wavelength of 1.31 μm (hereinafter referred to as “upstream 1.31 μm”) is used.

  The WDM filter 19 is a filter that divides and multiplexes three waves of 1.49 μm downstream, 1.55 μm downstream, and 1.31 μm upstream.

  The OLT 41 is a control device for communicating with the ONT. The TVSP 15 is a device that transmits a video signal. The HM 44 is a control device necessary for communicating with the CM over the Internet.

  Next, the operation of the center 1 will be described. First, the signal paths of the downlink video signal and downlink CM communication (for example, Internet communication) will be described.

  The downstream electrical signal (downstream 1.55 μm signal) output from the TVSP 15 reaches the FTX 17 via the coupler 46. The FTX 17 converts the electrical signal into an optical signal, and the optical signal passes through the WDM filter 19. This WDM filter 19 wavelength-multiplexes the downstream 1.55 μm signal and the downstream 1.49 μm for OLT-ONT communication described later, and outputs the result to the optical fiber 21.

  Further, since the electrical signal (CM signal) output from the HM 44 is transmitted at the same optical wavelength as the video signal, it is combined with the video signal by the coupler 46 and then converted into an optical signal by the FTX 17. After that, the same path as the video signal is followed.

  Next, the signal path of the uplink CWDM signal will be described. The upstream CWDM signal is a signal output from the CM 14 in the home 9. The upstream CWDM signal reaches the RRX 39 via the optical fiber 21, and the optical signal is converted into an electrical signal and input to the HM 44.

  Next, the signal path of the downlink OLT-ONT communication will be described. The downstream optical signal (downstream 1.49 μm signal) output from the OLT 41 is wavelength-multiplexed with the video signal (downstream 1.55 μm) by the WDM filter 19 and output to the optical fiber 21.

  Next, a signal path for uplink OLT-ONT communication will be described. The upstream OLT-ONT communication signal is a signal output from the ONT 12a of the home 8. The upstream OLT-ONT communication signal (upstream 1.31 μm) reaches the WDM filter 19 via the optical fiber 21. Thereafter, 1.31 μm upstream is branched by the WDM filter 19 and input to the OLT 41.

  Next, the configuration of an example of the closure and the CATV optical transmission apparatus will be described. FIG. 3 is a configuration diagram of an example of a closure and a CATV optical transmission apparatus.

  Referring to the figure, the closure 2 includes an optical coupler 48. An optical fiber for optical signal transmission of 1.49 μm downstream / 1.31 μm upstream is branched from the optical coupler 48 and connected to the ONTs 12 a and 12 b of each household.

  The CATV optical transmission apparatus 3 includes a WDM filter 26, an O / E (optical signal / electrical signal converter) 28, an E / O (electrical signal / optical signal converter) 37, trunk amplifiers 31, 36, and a coupler. 32 and 33 and directional filters 34 and 35 are comprised.

  The optical fiber 21 on the center 1 side passes through the closure 2 and is connected to the optical fiber 24 on the CATV optical transmission apparatus 3 side, and the optical fiber 24 is connected to the WDM filter 26 and the E / O 37.

  Next, operations of the closure and the CATV optical transmission apparatus will be described. First, the signal paths of the downlink video signal and the downlink CM communication signal will be described.

  The downstream video signal (downstream 1.55 μm signal) is input to the WDM filter 26 via the optical fiber 24. In the WDM filter 26, the downstream signal is branched to O / E 28, and the optical signal is converted into an electrical signal. Then, the downstream video signal converted into the electrical signal is input to the trunk amplifier 31 and amplified. The amplified downstream signal is output through the directional filters 34 and 35 after being branched by the coupler 32 to correspond to the output.

  Since the downstream CM communication signal is combined with the video signal by the coupler 46 in the center 1 as described above, the signal path from the closure 2 to the CATV optical transmission device 3 is the downstream video signal (downstream 1.55 μm signal) described above. It is the same.

  Next, the signal path of the uplink CWDM signal will be described. The upstream CWDM signal is divided into upstream bands by the directional filters 34 and 35, and is input to the upstream trunk amplifier 36 via the coupler 33. The upstream CWDM signal is amplified here, converted from an electrical signal to an optical signal by the E / O 37, and output to the optical fiber 24.

  Next, the signal path of the downlink OLT-ONT communication will be described. A downstream video signal (downstream 1.55 μm signal) and a wavelength-multiplexed downstream OLT-ONT communication signal (downstream 1.49 μm signal) are input to the WDM filter 26 in the CATV optical transmission apparatus 3 via the optical fiber 24. The Then, the downstream 1.49 μm signal is divided by the WDM filter 26 and input to the optical coupler 48 in the closure 2 via the optical fiber 7. The downstream 1.49 μm signal is branched by the optical coupler 48 to the ONTs 12a, 12b, etc. installed in each home, and further input to the PCs 13a, 13b, etc., so that communication is possible.

  Next, the signal path of the upstream OLT-ONT communication signal (upstream 1.31 μm signal) will be described. The upstream 1.31 μm signal and downstream 1.49 μm signal are wavelength-multiplexed because they have the same path.

  Upstream optical signals (upstream 1.31 μm signals) transmitted from the ONTs 12 a and 12 b are coupled by the optical coupler 48 and input to the WDM filter 26 in the CATV optical transmission apparatus 3 through the optical fiber 7. In the WDM filter 26, the upstream 1.31 μm signal, the downstream 1.55 μm signal, and the downstream 1.49 μm signal are wavelength-multiplexed, and the upstream 1.31 μm signal is transmitted to the center 1 through the optical fiber 24.

  As described above, according to the first embodiment of the present invention, by adding the WDM filter 26 in the CATV optical transmission apparatus 3, a conventional single optical fiber for each uplink (for example, both uplink and downlink) In addition to video / CM communication using 1.31 μm wavelength), it is possible to add OLT-ONT communication using FTTH.

  In the HFC system, since the optical fiber has already been laid from the center 1 to the branch point of the optical trunk line (the optical coupler 48 of the closure 2), the FTTH can be obtained simply by laying the optical fiber from the optical coupler 48 to the ONTs 12a and 12b. Can be realized.

  Specifically, in the past, only video / CM communication of 1.31 μm in the upper and lower directions was performed using a single optical cable, but according to the present invention, downlink video / CM communication (downstream 1.55 μm) and downstream OLT are performed. -ONT communication (downlink 1.49 [mu] m) and upstream OLT-ONT communication (upstream 1.31 [mu] m) are performed with a single optical cable, and upstream CWDM transmission (of 8 wavelengths of optical wavelengths 1.49 to 1.61 [mu] m) 1 wave) can be performed by another single optical cable.

  FIG. 4 is a block diagram of the second embodiment of the center 1 according to the present invention, and FIG. 5 is a block diagram of the second embodiment of the closure 2 and the CATV optical transmission apparatus 3 according to the present invention. In the figure, the same components as those in FIGS. 2 and 3 described above are denoted by the same reference numerals, and description thereof is omitted.

  The second embodiment is intended for line redundancy of the CATV optical transmission system of the first embodiment.

  First, the center 1 will be described. Referring to FIG. 4, the relays 42, DIS (signal distributor) 16, couplers 45 and 47, FTX 18, WDM filter 20, and RFSW (high frequency switch) 49 are newly added to the center 1. And RRX40. Further, along with the line redundancy of the CATV optical transmission system, an optical fiber 22 is added in addition to the optical fiber 21.

  In this embodiment, as an example, downlink video / CM communication (downlink 1.55 μm), downlink OLT-ONT communication (downlink 1.49 μm), uplink OLT-ONT communication (uplink 1.31 μm), and uplink CWDM transmission A description will be given of a case in which two systems (one of eight waves having an optical wavelength of 1.49 to 1.61 μm) are provided, but the present invention can also be applied to a system in which three or more systems are provided.

  A relay 42 is provided as the input / output of the OLT 41 is divided into two systems, and the relay 42 can be switched to one system. In addition, with the two systems, the WDM filter is also formed into two systems (WDM filters 19 and 20).

  Further, the DIS 16 is provided in association with the output of the TVSP 15 being divided into two systems, and the input / output of the TVSP 15 can be distributed to the two systems by the DIS 16. Also, two couplers (couplers 46 and 47) and two FTXs (FTX 17 and 18) are provided.

  In addition, a coupler 45 is provided in association with the two outputs of the HM 44, and the coupler 45 distributes the output of the HM 44 in two and couples it with the output of the TVSP 15 via the couplers 46 and 47.

  In addition, the RFSW 49 is provided in association with the two inputs of the HM 44, and the RRX is also provided with two systems (RRX 39, 40). One output of the RRXs 39 and 40 can be selected and input to the HM 44 by the RFSW 49.

  As described above, the signal handled in the center 1 is different from the first embodiment in that the signals handled by the center 1 are increased, and the path of each signal is the same as in the first embodiment. Therefore, the description of the signal path of the center 1 in the second embodiment is omitted.

  Next, the closure 2 and the CATV optical transmission device 3 will be described. Referring to FIG. 5, the WDM filter 27, the optical couplers 43 and 38, the O / E 29, and the relay 30 are newly added to the closure 2 and the CATV optical transmission apparatus 3. Further, along with the line redundancy of the CATV optical transmission system, an optical fiber 25 is added in addition to the optical fiber 24.

  In this embodiment, as an example, downlink video / CM communication (downlink 1.55 μm), downlink OLT-ONT communication (downlink 1.49 μm), uplink OLT-ONT communication (uplink 1.31 μm), and uplink CWDM transmission A description will be given of a case in which two systems (one of eight waves having an optical wavelength of 1.49 to 1.61 μm) are provided, but the present invention can also be applied to a system in which three or more systems are provided.

  CATV optical transmission apparatus by down-link video / CM communication (downstream 1.55 μm), downstream OLT-ONT communication (downstream 1.49 μm) and upstream OLT-ONT communication (upstream 1.31 μm) The three WDM filters are also divided into two systems (WDM filters 26 and 27), and an optical coupler 43 for coupling and branching these signals is provided.

  The relay 30 is for selecting one of two systems of downstream video / CM communication (downstream 1.55 μm). This relay 30 is selected as the system that is normally operated. However, if an abnormality occurs in the selected system, it is automatically switched to the other system, and remote control is also possible. It is.

  The optical coupler 38 is for branching upstream CWDM transmission (one of eight waves having an optical wavelength of 1.49 to 1.61 μm) into two systems.

  In the present embodiment, as an example, the case where the optical coupler 48 branches the downlink OLT-ONT communication (downlink 1.49 μm) and the uplink OLT-ONT communication (uplink 1.31 μm) into 32 branches.

  As described above, the signals handled by the closure 2 and the CATV optical transmission apparatus 3 are different from the first embodiment in that the signals handled by the closure 2 and the CATV optical transmission device 3 are different, and the paths of each signal are the same as in the first embodiment. It is. Therefore, description of signal paths of the closure 2 and the CATV optical transmission device 3 in the second embodiment is omitted.

  As described above, according to the second embodiment of the present invention, in addition to the effects of the first embodiment, there is an effect that the transmission path can be made redundant.

  Next, a third embodiment of the present invention will be described. The embodiment of the present invention is basically the same as the first and second embodiments described above, but the present CATV optical transmission apparatus 3 has components (each of the CATV optical transmission apparatuses 3 shown in FIGS. 3 and 5). Since the component part has a unit structure, it is possible to change functions and add models.

  For example, by changing the uplink CWDM (Coarse Wavelength Division Multiplexing) transmission method to the DWDM (Dense Wavelength Division Multiplexing) transmission method, the uplink communication capacity can be expanded.

It is a block diagram of an example of the CATV optical transmission system which concerns on this invention. 2 is a configuration diagram of an example of a center 1. FIG. It is a block diagram of an example of a closure and a CATV optical transmission apparatus. It is a block diagram of 2nd Example of the center 1 which concerns on this invention. It is a block diagram of 2nd Example of the closure 2 and the CATV optical transmission apparatus 3 which concern on this invention. It is a block diagram of an example of the CATV optical transmission apparatus using the conventional HFC transmission line.

Explanation of symbols

1 Center
2 Closure
3 CATV optical transmission equipment
4 Tap-off 6, 7 Optical fiber
8 Home 21, 22 Optical fiber 24, 25 Optical fiber 26, 27 WDM filter 61, 62 Coaxial transmission line

Claims (6)

A first signal based on an optical signal from the center is input via an optical transmission line, and the input first signal is converted into an electric signal and transmitted to each home via a coaxial transmission line. A CATV optical transmission apparatus that inputs a second signal by a signal through the coaxial transmission line , converts the input second signal into an optical signal, and transmits the optical signal to the center through the optical transmission line. the wavelength of the first signal by the optical signal from the wavelength of the third signal by the optical signal from the center, wherein each home by frequency division-multiplexing a wavelength of the fourth signal by the optical signal from each home Alternatively, a CATV optical transmission apparatus comprising filter means for transmitting to the center . The center and between the CATV optical transmission device is connected in the first 1-core optical fiber, said first through said first 1-core optical fiber, the third, fourth wavelength-multiplexed signal and the second signal Is transmitted,
The CATV optical transmission device and said each home between is connected by a first coaxial transmission line and the second 1-core optical fiber, said first through said coaxial transmission line the first and second signals are transmitted, 2. The CATV optical transmission apparatus according to claim 1, wherein the third and fourth wavelength division multiplexed signals are transmitted through the second one-fiber optical fiber. A closure is provided in the middle of the first one-fiber optical fiber between the CATV optical transmission apparatus and the center, and the third and fourth signals are transmitted via an optical coupler in the closure. The CATV optical transmission apparatus according to claim 2. A third one-core optical fiber is connected between the center and the CATV optical transmission device, and the second signal is transmitted through the third one-core optical fiber,
The second coaxial transmission line is connected between the CATV optical transmission apparatus and each household, and the second signal is transmitted through the second coaxial transmission line. A CATV optical transmission apparatus according to claim 1. By providing the third single-core optical fiber together with the first and second single-core optical fibers between the center and the CATV optical transmission apparatus, a line between the center and the CATV optical transmission apparatus is made redundant. CATV optical transmission apparatus according to claim 4, wherein a. An optical transmission system comprising the CATV optical transmission apparatus according to claim 1.

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