JP5891640B2 - Media conversion apparatus and transmission system - Google Patents

Description

  The present invention relates to a media conversion device and a transmission system.

  The CATV (cable television) system is based on a technology that divides a frequency band of a high-frequency signal transmitted by a coaxial cable into channel units (6 MHz) and multiplex-transmits a composite-type television signal to a necessary channel.

  The cable modem technology is used as a transmission means for providing such CATV systems with additional Internet services, VOD (Video On Demand), and VoIP (Voice over Internet Protocol) services. Has been.

The cable modem is installed on the user's home side and operates in combination with a CMTS (Cable Modem Termination System) which is a headend device on the CATV station side.
In a cable modem, for the purpose of realizing bidirectional data communication, a signal is converted into a high-frequency signal digitally modulated by the QAM method or the like, and transmitted by frequency multiplexing in the same way as a television signal.
Note that the same principle applies to digital television signals in that a high-frequency signal digitally modulated by OFDM or QAM is frequency-multiplexed in units of channels.

  That is, the CATV signal is characterized by a complex analog signal in which a modulated high-frequency signal is frequency-multiplexed.

In the CATV transmission system, a coaxial cable was originally used as a transmission medium from the CATV station equipment (head end device) to the subscriber's house.
However, in recent years, as shown in FIG. 9, an HFC (Hybrid Fiber-Coaxial) system that transmits from a CATV station facility (head-end device) to the vicinity of a subscriber's home using an optical fiber cable instead of a coaxial cable is generally used. It is the target. In HFC, a cable modem is connected to the subsequent stage of an optical node via a coaxial cable.

  In the HFC system, an analog high-frequency signal (coaxial RF signal data) that should be transmitted by a coaxial cable in the section from the head end to the optical node is optically converted into an optical fiber using an optical signal that is AM-modulated by an optical transceiver. It is transmitted via a cable and is also called an optical AM transmission system.

JP 2011-4095 A

Here, in the telephone system, FTTH (Fiber To The Home) method is used for opticalization. The FTTH method is also called a PON (Passive Optical Network) method, and transmits data encoded with optical pulses using an optical fiber cable as a transmission medium.
The PON system is composed of a station-side device (OLT), an optical fiber network that branches from an optical fiber cable connected thereto to a plurality of optical fiber cables via an optical distributor, and an end of the branched optical fiber cable. Connected home-side equipment (ONU).

  Even in the CATV system, if a PON system is used, an efficient network can be constructed. Therefore, a transition from a cable modem system to a PON system is desired.

However, the PON system in which data encoded by optical pulses is transmitted has no compatibility with a cable modem system (coaxial system or HFC) that is an analog transmission.
For this reason, in order to shift the cable modem system to the PON system, it is necessary to greatly change the equipment, resulting in a great burden.
Also, in apartment buildings, etc., even though fiber optic cables can be laid up to common facilities, etc., it may be difficult to lay fiber optic cables from there to each house. Introduction may be difficult.

  Accordingly, a first object of the present invention is to provide an apparatus or the like that facilitates the transition from a cable modem system to a PON system in a CATV system.

In order to achieve the first object, it is conceivable to provide a media conversion device that performs data conversion between the PON type station side device and the cable modem.
Here, in a general cable modem system as shown in FIG. 9, a plurality of CMTSs as station side devices are often installed in CATV stations. For example, a CMTS limited to VOD may be installed in a CATV station because of the relationship with an upstream application server or customer management system. Also, in the VoIP application, it is usual that the management entity of the station equipment is different, and a dedicated CMTS is installed.

  Therefore, a second object of the present invention is to make it compatible with the cable modem system as described above.

  In order to achieve the second object, it is conceivable to install a media conversion device having a plurality of media conversion units. However, when an optical signal from the station side is distributed to a plurality of media conversion units, expensive optical parts are required, which leads to high introduction costs.

  Accordingly, a third object of the present invention is to enable a signal to be given to a plurality of media conversion units without optical distribution.

  Moreover, even if the media conversion device described above is introduced, for example, it is impossible to unify the subscriber side terminal with only the cable modem in one apartment house, and the ONU is used as the subscriber side terminal. You may want to do that. That is, it is desirable to increase the ratio of ONUs sequentially while coexisting ONUs and cable modems.

Therefore, it is advantageous to be able to coexist with the FTTH method even when the above-described media conversion device is introduced. In this case, it is necessary to distribute the optical signal from the station side device not only to the media conversion device but also to the ONU at the subscriber's home. However, the distance from the cable station to the media conversion device is expected to vary, and the conditions for optical distribution also differ.
Therefore, when considering the optical distribution of the input to the media conversion device to the ONU, it is further necessary to comprehensively satisfy these conditions regarding the number of ONUs that can be connected. Troublesome circuit design and management are required.
On the other hand, if the media conversion device also has an FTTH (optical signal) relay function, the optical output starting from that position can be advantageously used independently for distribution to the ONU.

  Accordingly, a fourth object of the present invention is to provide a media conversion apparatus with an FTTH (optical signal) relay function.

  Further, transmission and distribution of optical signals in FTTH are performed only by passive components such as optical fibers and optical splitters. Therefore, in the optical distribution method, it is very difficult to automatically perform path switching or backup at the time of failure. Since a CATV transmission line is often installed on an outdoor utility pole or the like, a disconnection accident cannot be completely avoided, and it is desirable to be able to back up an important transmission route.

  Accordingly, a fifth object of the present invention is to provide functions suitable for transmission route backup and route switching.

Furthermore, it is desirable that the configuration of the media conversion device described above can be changed sequentially in accordance with the addition of CATV station applications and the progress of transition to FTTH.
Accordingly, a sixth object of the present invention is to facilitate the change of the configuration of the media conversion device.

(1) From the viewpoint of the first object, the present invention relates to a cable modem system between a first transmission unit capable of PON system transmission and a cable modem. A second transmission unit capable of transmission, wherein the first transmission unit converts PON data transmitted from the station side device into intermediate data of a predetermined method and outputs the intermediate data to the second transmission unit In addition, the intermediate data of the predetermined method output from the second transmission unit is converted into PON method data and transmitted to the station side device, and the second transmission unit transmits the cable transmitted from the cable modem. The modem system data is converted into intermediate data of the predetermined system and output to the first transmission unit, and the intermediate data of the predetermined system output from the first transmission unit is converted into cable modem system data. , The case A media conversion apparatus and transmits to the Null Modem.

  According to the present invention, even if there is a cable modem as a home side device, it is possible to shift to the PON system.

(2) From the viewpoint of the second object, the present invention relates to a cable modem system between a first transmission unit capable of PON system transmission and a cable modem with a PON system station side device. A plurality of media conversion units each having a second transmission unit capable of transmission, wherein the first transmission unit converts the PON method data transmitted from the station side device into intermediate data of a predetermined method, and In addition to outputting to the second transmission unit, the intermediate data of the predetermined method output from the second transmission unit is converted into PON method data and transmitted to the station side device, the second transmission unit, Cable modem data transmitted from the cable modem is converted into intermediate data of the predetermined system and output to the first transmission unit, and the intermediate data of the predetermined system output from the first transmission unit is converted to the cable modem. Formula Converted to over data, a media conversion apparatus characterized by transmitting to the cable modem.

(3) From the viewpoint of the third object, the media conversion further includes an optical link connected to the optical fiber to the PON type station side device, and a split circuit unit connected to the optical link, and the plurality of media conversions The first transmission unit is connected to the split circuit unit, and the split circuit unit distributes and outputs the electrical signal output from the optical link to the plurality of media conversion units, It is preferable that the electrical signals output from the first transmission units of the plurality of media conversion units are aggregated and output to the optical link. In this case, the split circuit unit can perform electrical distribution / aggregation without optically distributing / aggregating signals using an optical distributor.

(4) a first SerDes provided between the optical link and the split circuit unit;
A second SerDes provided between the split circuit unit and the plurality of first transmission units, wherein the first SerDes converts a serial electrical signal output from the optical link into a parallel signal; A parallel electric signal output from the split circuit unit to the optical link is serially converted and applied to the optical link. The second SerDes is supplied from the first transmission unit to the split circuit. A serial electrical signal output to the circuit unit is converted into parallel and applied to the split circuit unit, and a parallel electrical signal output from the split circuit unit to the first transmission unit is converted into serial. Then, it is preferable to provide the first transmission unit. In this case, the processing in the split circuit section can be performed with parallel signals, which is advantageous in that the speed can be reduced.

(5) A plurality of the optical links are provided, and the split circuit unit is connected to the plurality of first input / output units connected to the plurality of optical links and the first transmission unit of the plurality of media conversion units. A plurality of second input / output units, wherein each of the plurality of second input / output units connected to the first transmission unit is connected to the plurality of optical links. It is preferable to be selectively connected to any of the above. In this case, the path can be switched electrically in the split circuit section, and automatic path switching, which was difficult (cannot be performed electrically) with a passive optical splitter, or switching to a standby system in the event of a failure Automation such as (backup) becomes easy.

(6) It is preferable that the media conversion unit is configured to be detachable with respect to the split circuit unit. In this case, it becomes easy to expand the media conversion device.

(7) From the viewpoint of the fourth object, the first optical link connected to the optical fiber to the PON type station side device, the split circuit unit connected to the first optical link, and the split circuit unit One or more second optical links to be connected and one or more media converters described in (2), wherein the one or more media converters are connected to the station side device, A first transmission unit capable of PON transmission and a second transmission unit capable of cable modem transmission between the cable modem and the first transmission unit from the station side device; The transmitted PON system data is converted into intermediate data of a predetermined system and output to the second transmission unit, and the intermediate data of the predetermined system output from the second transmission unit is converted into PON system data. To the station side device, and The transmission unit converts the data of the cable modem method transmitted from the cable modem into intermediate data of the predetermined method and outputs the intermediate data to the first transmission unit, and the predetermined method output from the first transmission unit. The intermediate data is converted into cable modem data and transmitted to the cable modem. The first transmission unit is connected to the split circuit unit, and the split circuit unit is output from the first optical link. And distributing the electrical signal to the one or more second optical links and the one or more media converters,
It is preferable that electrical signals output from the one or more second optical links and the first transmission unit of the one or more media conversion units are aggregated by the split circuit unit and output to the first optical link. In this case, a PON system can be constructed on the home side of the media conversion device by connecting an optical fiber to the second optical link.

(8) The first SerDes provided between the first optical link and the split circuit unit, the split circuit unit and the one or more first transmission units, and the split circuit unit and the 1 Or a second SerDes provided between a plurality of second optical links, wherein the first SerDes converts the serial electrical signal output from the first optical link into parallel and converts the split circuit unit The parallel electrical signal output from the split circuit unit is converted to serial and applied to the first optical link, and the second SerDes is connected to the split circuit from the first transmission unit and the second optical link. The serial electric signal output to the unit is converted into parallel and given to the split circuit unit, and the split circuit unit Preferably provide a parallel electrical signal output with respect et the first transmitter and the second optical link to the into serial first transmission section and a second optical link.

(9) From the viewpoint of the fifth object, a plurality of the first optical links are provided, and the split circuit unit includes a plurality of first input / output units connected to the one or the plurality of first optical links, The one or more second optical links, and the plurality of second input / output units connected to the first transmission unit of the one or more media conversion units. Each of the plurality of second input / output units connected to the link and the first transmission unit of the one or more media conversion units is one of the plurality of first input / output units connected to the first optical link. It is preferable that they are selectively connected. In this case, the path can be switched electrically in the split circuit section, and automatic path switching, which was difficult (cannot be performed electrically) with a passive optical splitter, or switching to a standby system in the event of a failure Automation such as (backup) becomes easy.

(10) From the viewpoint of the sixth object, it is preferable that the media conversion unit or the second optical link is detachably configured with respect to the split circuit unit. In this case, it becomes easy to expand the media conversion device.

(11) From another viewpoint, the present invention provides a transmission system in which the media conversion device according to any one of (1) to (10) is installed between a PON type station side device and a cable modem. It is.

  According to the present invention, the CATV system can be easily shifted to the PON system.

It is a figure which shows the media converter and transmission system relevant to the 1st objective. It is a figure which shows the media converter and transmission system relevant to the 2nd objective. It is a figure which shows the media converter relevant to the 3rd objective. It is a figure which shows the media converter relevant to the 4th objective. It is a figure which shows the media conversion apparatus relevant to the 5th objective. It is a figure which shows the crossbar switching circuit functionally matched with the signal of the PON system. It is a figure which shows the other example of the media conversion apparatus relevant to the 6th objective. It is a figure which shows the other example of a media converter. It is a figure which shows the conventional HFC system.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[1. First Embodiment]
FIG. 1 shows a transmission system in which a PON system (FTTH system) and a cable modem system (CATV system) are mixed.
In the CATV station, an OLT (Optical Line Terminal) 1 that is a PON type station side device is installed as a headend device. The OLT 1 serves as a relay node with an upper network such as an IP network.

An optical fiber 2 (main line) extending from the OLT 1 is branched into a plurality of optical fibers 4 (branch lines) via an optical distributor 3 (optical splitter) which is a passive optical distribution node.
In a general PON system transmission system, as shown in FIG. 1, an ONU (Optical Network Unit) 5, which is a PON system home device, is connected to the end of the branched optical fiber 4. Note that a terminal device 6 such as a PC is connected to the ONU 5.

  In the transmission system of the present embodiment, the media converter 10 is connected to any one or more (or all) of the ends of the branched optical fibers 4.

  The media conversion device 10 is installed, for example, on an equipment room of an apartment house or on a utility pole in the vicinity of the apartment house. A coaxial cable 7 is connected to the media conversion device 10. The coaxial cable 7 is laid, for example, toward each door of the apartment house, and a cable modem 8 is connected to the end of the branched coaxial cable 7. The cable modem 8 is connected to a terminal device 6 such as a PC.

  The media conversion device 10 includes PON method data transmitted to the OLT 1 serving as the station side device, and cable modem method data (coaxial RF signal data) transmitted to the cable modem 8. Convert data between each other.

  The media conversion device 10 includes an ONU function unit (first transmission unit) 11, a CMTS function unit (second transmission unit), and an optical link (first optical link) 13.

  The optical link 13 is an optical transceiver that is connected to the end of the optical fiber 4, converts an optical signal from the optical fiber 4 into an electrical signal, outputs the electrical signal, converts the electrical signal into an optical signal, and outputs the optical signal to the optical fiber 4. Note that the electrical signal output from the optical link 13 is merely a conversion of the PON data, which is an optical signal, into an electrical signal, and the data format is not converted.

The ONU function unit 11, which is a first transmission unit, performs PON transmission with the OLT 1 via the optical link 13.
The ONU function unit 11 converts the PON format data of the electrical signal output from the optical link 13 into intermediate data of a predetermined method and outputs it to the CMTS function unit 12 side which is the second transmission unit (downstream ONU conversion).
Further, the ONU function unit 11 converts intermediate data of a predetermined method output from the CMTS function unit 12 into PON method data (electrical signal) and outputs it to the OLT 1 side (upstream ONU conversion).
A general ONU 5 includes the optical link 13 and the ONU function unit 11. In other words, it can be said that the ONU function unit 11 is obtained by removing the optical link 13 from the general ONU 5.

  In this embodiment, the OLT 1 of the station side device and the ONU function unit 11 of the media conversion device 10 are equivalent to a pair of OLT and ONU in a general PON system. That is, the station-side device 1 and the media conversion device 10 are configured as a PON system that transmits PON data.

The CMTS function unit 12, which is the second transmission unit, performs cable modem transmission with the cable modem 8 connected via the coaxial cable 7.
The CMTS function unit 12 has a function equivalent to that of the CMTS which is a station side device in a cable modem system.

That is, the CMTS function unit 12 converts the cable modem type data transmitted from the cable modem 8 into intermediate data of a predetermined method and outputs the intermediate data to the ONU function unit 11 (uplink CMTS conversion).
Further, the CMTS function unit 12 converts intermediate data of a predetermined method output from the ONU function unit 11 into data of a cable modem method, and transmits the data to the cable modem 8 side (downlink CMTS conversion).

  In this embodiment, the CMTS function unit 12 and the cable modem 8 of the media conversion device 10 are equivalent to a CMTS and cable modem pair in a general cable modem system. That is, the media conversion device 10 and the cable modem 8 are configured as a cable modem system in which cable modem method data is transmitted.

  The media conversion device 10 performs mutual conversion between the PON method data and the cable modem method data, so that transmission between the PON type station side device (OLT) 1 and the cable modem 8 is possible.

In the transmission system of the present embodiment, the PON system can be used as the trunk line from the station. Therefore, even if the home apparatus is the cable modem 8, the PON system can be adopted as the system on the trunk line as the CATV station.
For this reason, it is not necessary to change the equipment (cable modem 8) on the subscriber's house side or install an optical fiber in the apartment, even in an apartment where the cable modem system is used. Even when the optical fiber cannot be laid, the main line portion can be easily converted to the PON system, and the first object of the present invention can be achieved.
Therefore, as a CATV station, even if the PON system is used, replacement of the terminal device on the home side (exchange from the cable modem to the ONU) can be made unnecessary or delayed, which is economical.

[2. Second Embodiment]
FIG. 2 shows a media conversion device 20 including a plurality of media conversion units 10a, 10b, and 10c.
The media converter 10 in FIG. 2 is the same as the media converter shown in FIG.

  In a general cable modem system, a plurality of CMTSs as station side devices are often installed in CATV stations. For example, a CMTS limited to VOD may be installed in a CATV station because of the relationship with an upstream application server or customer management system. Also, in the VoIP application, it is usual that the management entity of the station equipment is different, and a dedicated CMTS is installed.

  The media converter 20 of FIG. 2 includes a plurality of media converters 10a, 10b, and 10c so as to be compatible with the cable modem system as described above, thereby achieving the second object of the present invention. For example, the first media conversion unit 10a is for VOD, the second media conversion unit 10b is for VoIP, and the third media conversion unit 10c is for the Internet and others. The optical signals branched by the optical distributor 3 are input to the optical links 13 of the media converters 10a, 10b, and 10c. Further, the CMTS function units 12 of the media conversion units 10 a, 10 b, and 10 c are aggregated and connected to the coaxial cable 7. The end of the branched coaxial cable 7 is connected with a cable modem built-in STB (Set Top Box) 8a for VOD, a cable modem 8, and a cable modem 8b (EMTA: Embedded Multimedia Terminal Adapter) with a telephone function. A telephone device 6a is connected to the cable modem with telephone function 8b as a terminal device.

[3. Third Embodiment]
FIG. 3 shows a media conversion device 20 with fewer optical components.
In the media conversion device 20 of FIG. 2, the plurality of media conversion units 10 are each provided with an optical link 13 that is an expensive optical component. In addition, an optical distributor 3 for distributing the optical signal to the plurality of media conversion units 10 is also necessary. In addition, the optical components are very delicate, and it may be difficult in practice to arrange a large number of them in an equipment room of an apartment house.

3 includes a single first optical link 13 and a split circuit unit 21 that electrically distributes and aggregates signals.
The split circuit unit 21 electrically performs a function equivalent to that of the optical distributor 3 of FIG. The split circuit 21 copies and distributes the PON system data of the electrical signal (downstream signal) output from the first optical link 13 according to the number of outputs.

In addition, the split circuit unit 21 aggregates the PON system data of the electrical signals (upstream signals) output from the plurality of media conversion units 10a, 10b, 10c, and 10d, and outputs them to the first optical link 13 side.
In the PON system, the signal from each ONU is transmitted at different timing so that the upstream signal does not collide with the signal from each ONU.
Therefore, the split circuit unit 21 simply aggregates a plurality of signals received from the plurality of media conversion units 10a, 10b, 10c, and 10d and sequentially sends them to the first optical link 13 side for the upstream signal. .

The split circuit unit 21 in FIG. 3 distributes and outputs the electrical signal output from the first optical link 13 to the plurality of media conversion units 10a, 10b, 10c, and 10d, and also outputs the plurality of media conversion units 10a. , 10b, 10c, and 10d are collected and output to the first optical link 13.
In this case, since the split circuit unit can be electrically distributed and aggregated, the optical distributor 3 of FIG. 2 which is an expensive optical component is not necessary. Further, since the first optical link 13 is not necessary for each of the media conversion units 10a, 10b, 10c, and 10d, the number of optical links that are expensive optical components can be reduced. Can be achieved.

  If the media conversion device 20 in FIG. 3 is used, the optical distributor 3 is unnecessary for the purpose of distributing signals to a plurality of media conversion units of the media conversion device 20, but other media conversion devices 20 and In order to distribute the signal to the ONU, an optical distributor 3 may be provided in the PON system.

In the media conversion device 20 of FIG. 3, a first SerDes (SERializer / DESerizer) 22 is provided between the first optical link 13 and the split circuit unit 21. Further, second SerDes 23a, 23b, 23c, and 23d are provided between the split circuit unit 21 and the plurality of media conversion units 10a, 10b, 10c, and 10d.
The first and second SerDes perform mutual conversion between a serial signal and a parallel signal.

The first SerDes 22 converts the serial electrical signal (downlink signal) output from the first optical link 13 into a parallel electrical signal and regenerates the clock based on the downlink signal. The converted parallel electric signal is output to the split circuit unit 21 side.
Further, the first SerDes 22 converts the parallel electrical signal (upstream signal) output from the split circuit unit 21 to the first optical link 13 side into a serial electrical signal and outputs the serial electrical signal to the first optical link 13 side.
The first optical link 13 and the first SerDes 22 are collectively referred to as a station side optical transmission / reception unit 14.

The second SerDes 23a, 23b, 23c, and 23d perform reverse conversion to the first SerDes22.
That is, the second SerDes 23a, 23b, 23c, and 23d convert the serial electrical signal (upstream signal) output from the first transmission unit 11 to the split circuit unit 21 side into a parallel electrical signal, and then to the split circuit unit 21 side. Output.
Further, the second SerDes 23 a, 23 b, 23 c, and 23 d convert the parallel electric signal (downstream signal) output from the split circuit unit 21 to the first transmission unit 11 into a serial signal and output the serial signal to the first transmission unit 11. To do.

  In the split circuit unit 21 surrounded by the first and second SerDes, the transmission signal becomes a parallel synchronization signal, and the clock frequency can be lowered to, for example, 1/10 or less than the optical signal, so that signal processing is easy. It becomes. For example, when the optical signal clock is 1.25 GHz, the parallel signal clock can be 125 MHz.

Moreover, since SerDes and the split circuit unit 21 are general-purpose electrical components, the cost can be reduced.
If the signal conditions of the second SerDes 23a, 23b, 23c, 23d and the first transmission unit 11 do not match, the signal amplitude adjustment circuits 24a, 24b, 24c, 24d are adjusted as shown in FIG. Thus, even if the signal conditions of the second SerDes 23a, 23b, 23c, 23d and the first transmission unit 11 do not match, both can be combined.

[4. Fourth Embodiment]
FIG. 4 shows the media conversion device 20 in which the PON relay function coexists.
The media conversion device 20 in FIG. 4 is the same as the media conversion device 20 in FIG. 3 except that the media conversion unit 10 d in FIG. 3 is replaced with a PON relay function unit 30.

  The PON relay function unit 30 includes a second optical link 25, and the PON system data converted into an electrical signal by the first optical link 13 is converted again into an optical signal, or the PON relay function unit 30. The optical signal (PON system data) from the ONU 5 connected to the optical fiber 9 extending from is converted into an electrical signal. Note that the PON system data converted into the electrical signal by the second optical link 25 is reconverted to the optical signal by the first link.

The split circuit unit 21 in FIG. 4 distributes the electric signal output from the first optical link 13 not only to the media conversion units 10a, 10b, and 10c but also to the second optical link 25.
4 splits the electrical signals output from the second optical link 25 and the first transmission unit 11 of the media conversion units 10a, 10b, and 10c, and outputs them to the first optical link 13 side. To do.

The media conversion device 20 in FIG. 4 relays the PON system on the station side and the PON system on the home side than the media conversion device 20. Thereby, for example, a cable modem and an ONU for PON can coexist in one apartment house.
Even in a single apartment house, there may be subscribers who want the PON system, and it may be difficult to unify the cable laying in the apartment house to the cable modem system (coaxial). It is also assumed that ONU will increase in the future.

  In this case, as shown in FIGS. 1 and 2, among the branch optical fibers 4 branched by the optical distributor 3, a branch optical fiber different from the branch optical fiber to which the media converter 10 or the media converter 20 is connected is used. It is conceivable to connect ONUs.

  In this case, it is necessary to further distribute a part of the optically distributed signal to the ONU at the subscriber's house. However, the distance from the CATV station to the media conversion apparatus 20 varies, and the light distribution conditions also differ.

  Therefore, when the input from the station side to the media conversion device 20 is optically distributed, the number of ONUs that can be further connected is to satisfy these conditions comprehensively. Troublesome circuit design and management are required.

On the other hand, in the media conversion device 20 of FIG. 4, the optical signal is relayed by the media conversion device 20, so that the propagation loss due to the optical fiber between the CATV station and the device 20 and the distribution by the optical distributor 3 are performed. Loss becomes irrelevant. That is, the transmission conditions on the subscriber premises side of this device can be determined only by the output of the second optical link 25 of the PON relay function unit 30 of this device 20. As a result, a large number of light distributions can be obtained in an apartment house located away from the CATV station, and as a result, the optical fiber of the entire CATV network can be saved. Therefore, the circuit design of the transmission network is simplified, management becomes easy, and the fourth object of the present invention is achieved.
In addition, the cable modem system and the PON system can be easily coexisted, and the advantage that the transition to the PON system becomes very flexible is born.

[5. Fifth Embodiment]
FIG. 5 shows a media conversion apparatus 20 that can switch between an active optical fiber path and a standby optical fiber path.
In the media conversion apparatus 20 of FIG. 5, the working optical fiber 2a and the standby optical fiber 2b can be connected.
Optical links (first optical links) 13a and 13b are connected to the optical fibers 2a and 2b, and first SerDes 22a and 22b are provided between the first optical links 13a and 13b and the split circuit unit 21, respectively. ing.

The split circuit unit 21 in FIG. 5 includes a plurality of first input / output units 21a and 21b corresponding to the plurality of first optical links 13a and 13b.
The split circuit unit 21 includes a plurality of second input / output units 21-1, 21-2, 21-3, and 21-4 corresponding to the plurality of media conversion units 10a, 10b, 10c, and 10d. The first input / output units 21a and 21b are selectively connected.

  That is, normally, the second input / output units 21-1, 21-2, 21-3, and 21-4 of the split circuit unit 21 are connected to the first input / output unit 21a connected to the working optical fiber 2a. Yes. When it is desired to switch the connection to the standby optical fiber 2b, the second input / output units 21-1, 21-2, 21-3, and 21-4 of the split circuit unit 21 are connected to the standby optical fiber 2b. The connection is switched so as to be connected to the connected first input / output unit 21b.

As shown in FIG. 5, the split circuit unit 21 has a crossbar replacement function.
FIG. 6 shows an example of a crossbar switching circuit that is functionally matched to a PON signal. The plurality of first input / output units 21a, 21b, and 21c are connected to a PON type station side device (OLT) through separate paths. The second input / output units 21-1, 21-2, 21-3, and 21-4 connected to the media conversion unit or the PON relay function unit are the first input / output units connected to the station side device (OLT). Any one of 21a, 21b, and 21c can be selectively connected.

In the media conversion device 20 of FIG. 5, switching of a line or switching to a backup system (backup) in the event of a failure can be performed electrically by the crossbar replacement function of the split circuit unit 21, and path switching is automated. Becomes easy.
That is, in the light distribution method using the light distributor 3, since the light distributor 3 is a passive component, it is difficult (automatically cannot be performed) to automatically switch paths. On the other hand, in the media conversion device 20 of FIG. 5, it is easy to provide an automatic path change and a backup function at the time of failure, which are difficult with optical distribution, and the fifth object of the present invention is achieved.
In the media conversion device 20 of FIG. 5 as well, the PON relay function unit 30 can be provided as in FIG.

[6. Sixth Embodiment]
The media conversion device 20 in FIG. 7 is a module in which the media conversion unit and the PON relay function unit in FIG. 4 are modularized for each function.
In FIG. 7, each system on the home side with respect to the split circuit unit 21 is formed into sub-blocks 40a, 40b, 40c, and 40d that are modularized. The sub-blocks 40a, 40b, 40c, and 40d on the home side, together with the media conversion units 10a, 10b, and 10c or the PON relay function unit 30, are the second SerDes 23a, 23b, 23c, and 23d and the adjustment circuits 24a and 24b that are in the preceding stage. 24c and 24d are modularized.

  Between the split circuit unit 21 and the second SerDes 23a, 23b, 23c, and 23d, signals are transferred with low-speed parallel signals, so the second SerDes 23a, 23b, and 23d are connected to the sub-blocks 40a, 40b, 40c, and 40d on the home side. By including 23c and 23d, it is possible to easily transfer signals between the split circuit unit 21 and the sub-blocks 40a, 40b, 40c, and 40d at a low speed.

  The sub-blocks 40a, 40b, 40c, and 40d on the home side can be attached to and detached from the split circuit unit 21, respectively. That is, the board (sub board) constituting the sub block is detachably connected to the apparatus (main board apparatus) including the split circuit unit 21 via the connector or the like.

The home side sub-blocks 40a, 40b, 40c, 40d including the media conversion unit 10 or the second optical link 25 are detachable from the main board device, so that according to the individual circumstances of the CATV station, etc. The home-side output of the media converter 20 can be freely rearranged to either a cable modem system (coaxial RF signal) or a PON system. Also, the number of outputs can be freely adjusted by attaching and detaching the sub-block. In particular, when the media conversion device 20 is initially installed, the media conversion device 20 can be easily expanded by reducing the number of outputs and attaching an expansion sub-block later. The sixth objective is achieved.
In FIG. 7, all four systems on the home side of the split circuit unit 21 are configured as sub-blocks 40a, 40b, 40c, and 40d, and are configured to be detachable from the main board device. Only part of the system may be sub-blocked.
Further, the first optical links 13a and 13b and the first SerDes 22a and 22b closer to the station than the split circuit unit 21 in FIG. 7 may be sub-blocked as the station-side optical transmission / reception units 14a and 14b, respectively, so as to be detachable.

[7. Seventh Embodiment]
In FIG. 8, the lower two systems are detachable sub-blocks (extension sub-boards) 40c and 40d, and the upper two systems are provided on the main board side including the split circuit portion 21 (not shown in FIG. 8). An example is shown.

The high-frequency cable modem system data input / output to / from the CMTS function unit 12 of the media converters 10a, 10b, 10c, and 10d is divided into separate uplink signals and downlink signals, with the CMTS function unit 12 as a unit. Processed.
In the media conversion device 20 of FIG. 8, a diplex filter 51 is provided in order to improve usability by combining the coaxial cables on the home side with respect to the CMTS function unit 12 into one.

  The diplex filter 51 separates upstream and downstream signals. Each upstream signal and downstream signal is amplified by the amplifier 52. Further, appropriate distribution / aggregation is performed by the distributor 53.

  Further, the expansion sub-blocks (expansion sub-boards) 40c, 40d include a coaxial connector 55 connected to the coaxial connector 54 provided on the main board side, and between these coaxial connectors 54, 55, Connected by coaxial jumper. When the extension sub-blocks (extension sub-boards) 40c, 40d are not mounted on the main board, the dummy sub-board 60 shown in FIG. 8 is mounted, and the coaxial connector 55 of the dummy sub-board 60 and the main board are mounted. The coaxial connector 54 may be connected.

[8. Addendum]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Station side apparatus 2 Optical fiber 3 Optical distributor 4 Optical fiber 6 Terminal apparatus 7 Coaxial cable 8 Cable modem 9 Optical fiber 10 Media converter 10a, 10b, 10c, 10d Media converter 11 1st transmission part (ONU function part)
12 Second transmission unit (CMTS function unit)
13 Optical link (first optical link)
14 station side optical transmission / reception unit 14a, 14b station side optical transmission / reception unit 20 media conversion device 21 split circuit unit 21a, 21b first input / output unit 21-1, 21-2, 21-3, 21-4 second input / output unit 22 1st SerDes
23a, 23b, 23c, 23d Second SerDes
24a, 24b, 24c, 24d Adjustment circuit 25 Optical link (second optical link)
30 relay function unit 40a, 40b, 40c, 40d sub-block 51 diplex filter 52 amplifier 53 distributor 54 coaxial connector 55 coaxial connector 60 dummy substrate

Claims (9)

A media conversion device installed between a PON type station side device and a cable modem,
An optical fiber is connected to the station side device, converts an optical signal from the optical fiber into an electrical signal and outputs it, converts an electrical signal into an optical signal and outputs the optical signal to the optical fiber, and
A split circuit connected to the optical link;
A plurality of media converters for mutually converting data between PON data and cable modem data;
With
The optical link converts the PON method data of the optical signal from the optical fiber into PON method data of an electric signal, and outputs the PON method data of the electric signal to the split circuit side,
The split circuit section is
The PON method data of the electrical signal output from the optical link is copied and distributed to the plurality of media conversion units and output,
Aggregating PON data of electrical signals output from the plurality of media conversion units, and outputting to the optical link ,
The media converter according to claim 1, wherein the optical link converts the PON data of the electrical signal output from the split circuit into an optical signal and outputs the optical signal to the optical fiber . A first SerDes provided between the optical link and the split circuit unit;
A second SerDes provided between the split circuit unit and the plurality of media conversion units;
The first SerDes is
The serial electrical signal output from the optical link is converted into parallel and given to the split circuit unit,
A parallel electrical signal output from the split circuit unit is converted to serial and given to the optical link,
The second SerDes is
The serial electrical signal output from the media conversion unit to the split circuit unit is converted into parallel and given to the split circuit unit,
The media conversion apparatus according to claim 1, wherein the parallel electric signal output to the media conversion unit from the splitting circuit into serial given to the media conversion unit. A plurality of the optical links are provided,
The split circuit section is
A plurality of first input / output units connected to the plurality of optical links;
A plurality of second input / output units connected to the plurality of media conversion units;
With
The medium according to claim 1, wherein each of the plurality of second input / output units connected to the media conversion unit is selectively connected to one of the plurality of first input / output units connected to an optical link. Conversion device.   The media conversion device according to claim 1, wherein the media conversion unit is configured to be detachable from the split circuit unit. A media conversion device installed between a PON type station side device and a cable modem,
A first optical fiber connected to the station side device is connected, and an optical signal from the first optical fiber is converted into an electrical signal and output, and an electrical signal is converted into an optical signal and output to the first optical fiber. An optical link,
A split circuit connected to the first optical link;
A second optical fiber is connected to the PON type home-side device, and an optical signal from the second optical fiber is converted into an electric signal and output to the split circuit unit, and an electric signal from the split circuit unit is converted into an optical signal. One or a plurality of second optical links that are converted into and output to the second optical fiber;
One or a plurality of media converters for mutually converting data between PON data and cable modem data;
With
The first optical link converts the PON method data of the optical signal from the first optical fiber into PON method data of an electric signal, and outputs the PON method data of the electric signal to the split circuit side,
The split circuit section is
The PON method data of the electrical signal output from the first optical link is copied and distributed to the one or more second optical links and the one or more media converters, and is output.
Aggregating PON system data of electrical signals output from the one or more second optical links and the one or more media conversion units, and outputting to the first optical link ,
The media converter according to claim 1, wherein the first optical link converts the PON data of the electrical signal output from the split circuit into an optical signal and outputs the optical signal to the first optical fiber . A first SerDes provided between the first optical link and the split circuit unit;
A second SerDes provided between the split circuit unit and the one or more media conversion units and between the split circuit unit and the one or more second optical links;
The first SerDes is
The serial electrical signal output from the first optical link is converted into parallel and given to the split circuit unit,
The parallel electrical signal output from the split circuit unit is converted into serial and is provided to the first optical link,
The second SerDes is
A serial electrical signal output from the media conversion unit and the second optical link to the split circuit unit is converted into parallel and given to the split circuit unit, and
The media conversion device according to claim 5, wherein a parallel electrical signal output from the split circuit unit to the media conversion unit and the second optical link is serially converted and provided to the media conversion unit and the second optical link. A plurality of the first optical links are provided,
The split circuit section is
A plurality of first input / output units connected to the plurality of first optical links;
A plurality of second input / output units connected to the one or more second optical links and the one or more media conversion units;
Each of the one or more second optical links and the plurality of second input / output units connected to the one or more media conversion units is connected to the first optical link. The media conversion device according to claim 5 or 6, wherein the media conversion device is selectively connected to any of the above.   The media conversion device according to any one of claims 5 to 7, wherein the media conversion unit or the second optical link is configured to be detachable from the split circuit unit. A transmission system in which the media conversion device according to any one of claims 1 to 8 is installed between a PON type station-side device and a cable modem.

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