JPS5888944A - Coaxial optical repeater - Google Patents

Abstract

PURPOSE:To perform processing of reproduced relaying and collision, and interfacing between a coaxial cable and an optical transmission line, by connecting a plurality of coaxial cables to which a plurality of communication terminals are connected to a star repeater via a repeater having an electrooptic converter. CONSTITUTION:Communication terminal devices A0-Al and N0-Nn are information sinks such as picture and audio terminals and provided with an interface section with a connection tap T, which is provided with a transceiver of branch connection at an intermediate tape point of coaxial cables CA-CN, performing the detection of collision of transmission/reception of signals among the devices A0-Nn and power supplying. Coaxial optical repeaters COR0-CORN mutually connect optical fiber cables LT and LR, convert signals between them, and detect collision on the coaxial cables to inform it to the other CORs via a star repeater SREP, and inform the colision detected at the other repeaters COR or the repeater SREP to each terminal device connected to the corresponding coaxial cables.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a coaxial/optical repeater, particularly a coaxial cable to which a plurality of communication terminal devices are commonly connected, and one of a plurality of optical transmission lines connected to a star repeater. This relates to coaxial/optical repeaters for communication networks that relay signals to each other.

As a local communication network installed in the user's premises, communication terminal devices are commonly connected through multiple intermediate taps of coaxial cables via transmitting/receiving devices (transceivers), and each communication terminal device independently transmits information signals to others. A so-called C8MA/CD method is known in which the data is transmitted to a number of communication terminal devices, and when there is a transmission collision between the terminal devices, each terminal device stops transmitting and retransmits after a random waiting time. This coaxial cable is, for example, 500m
~2! The cable has a length of 11,100 MHz and a transmission band of about 20 MHz, and baseband pulse signals are transmitted. The information to be transmitted includes images, audio, and data, and is assembled into message blocks such as notebooks, and control codes such as destination addresses and check codes are added.

By the way, coaxial cable transmission lines can generally be easily branched from an intermediate tag and connected to communication terminal equipment, and the construction is relatively simple, but on the other hand, it is susceptible to external noise such as from power lines and telephone lines. The disadvantage is that it is relatively weak. If such a local communication network is installed on the same floor within a building, there are relatively few problems, but if coaxial cables are installed between other floors, there will be problems from other power sources in the cable duct. Coaxial cables are often affected by noise, and when coaxial cables are installed between buildings, they are often affected by voltage surges caused by lightning strikes.

Therefore, it is desirable to use an optical fiber transmission line as a so-called trunk transmission line between floors within a building or between buildings. Optical fiber transmission lines have disadvantages such as high transmission speed, a large number of channels, and the need for advanced technology for noise-resistant mechanical connections. Therefore, optical fiber transmission lines are suitable as trunk communication lines that require high-density, high-speed transmission and require little construction work.

Therefore, the most desirable system configuration at present is a communication network that uses coaxial cables as branch transmission lines and optical fiber transmission lines as the main transmission line.
The success or failure of adopting such a system configuration in the 8MA/CD system depends on how the problem of collision processing is solved. To organically connect a coaxial cable transmission line and an optical fiber transmission line, we need a coaxial/optical repeater that completely handles collisions on the coaxial cable, collisions between coaxial cables, and collisions between optical fiber transmission lines. need to be developed.

Therefore, the present invention eliminates the drawbacks of the prior art, takes advantage of the advantages of coaxial cables and optical fiber transmission lines, organically combines them, and creates a coaxial cable that can completely handle collisions.・The purpose is to provide optical repeaters.

According to the invention, this object is achieved by a coaxial-optical repeater as follows. In other words, this repeater includes a signal transmitting/receiving means that performs mutual conversion between the electrical signal of the coaxial cable and the optical signal of the optical transmission line to transmit and receive signals, and a signal transmitting/receiving means that transmits and receives signals by mutually converting the electric signal of the coaxial cable and the optical signal of the optical transmission line, and the signal transmitting and receiving means that detects the collision of transmission in the coaxial cable and generates a collision detection signal. a collision detection means that generates a collision detection signal and sends a collision detection signal to the optical transmission line by the signal transmission and reception means; and when the signal transmission and reception means receives the collision signal from the star repeater through the optical transmission line, the signal state on the coaxial cable is changed to a collision state. and a collision state generating means.

Next, embodiments of the coaxial/optical repeater according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a local communication network to which a coaxial/optical repeater according to the present invention is applied.

In this communication network, for example, a private communication network installed in a user's premises, the coaxial cable CA is installed on one floor or building, and the coaxial cables CB-CN are installed on other floors or buildings, respectively.

(l+1) communication terminal devices AO to Al belonging to group GO
are each coupled to a coaxial cable CA by a connecting tap T containing a transceiver. The same applies to the other groups G1 to GN.

These (N+1) groups are connected to each other by optical fiber cables LTO to LTN and LRO to LRN, and a star repeater 5REP from the connection tap TR and the coaxial/optical repeater CORONCORN.

The communication terminal device A O= N n is, for example, an image terminal,
It is an information source and information sink, such as a voice terminal, a data terminal or a computer, and is provided with an interface section with a connection tag T.

The connection tag T is a device that branches and connects each communication terminal AO=Nn with matching impedance at the intermediate tag point of the coaxial cables CA-CN, and connects the signal between the coaxial cable CA-CN and the communication terminal device AO=Nn. It has a transceiver that performs transmission and reception, transmission collision detection, and power supply.
These are installed in close proximity to the coaxial cable CA-CN. This ensures that the information signals on the coaxial cable CA-CN meet the specified conditions.

Coaxial cable CA-CN, for example, cable length 50
It has a transmission band of about 20 MHz from 0m to 2km,
A baseband pulse signal is transmitted at a transmission rate of about 10 megabits/second.

The information signals to be transmitted include image signals, audio signals, and data signals, and are assembled into message blocks such as packets in each communication terminal device AO-Nn, and transferred in blocks. Of course, this message block includes a destination address and control codes such as check codes, and each terminal device AO to Nn has a destination address that matches its own address.

Load the sage block into the device.

Two identical coaxial cables, e.g.
When more than one terminal device starts transmitting almost simultaneously, that is, when a collision occurs, the transceiver of each connection tap T detects the occurrence of the collision and notifies each terminal device of its own station of the occurrence of the collision. The terminal device that caused the collision temporarily stops transmission, recovers, and starts transmission again after a random waiting time has passed. Such a method is CSMA/C
This is called method D.

The coaxial/optical repeater C0RO-C0RN consists of coaxial cables CA to CN and optical fiber cables LT, as detailed later.
It interconnects O-%-L'rN and LRO to LRN, performs signal conversion between them, and detects collisions on the corresponding coaxial cables, turns star repeater 5REP red and white, and connects other coaxial/optical cables. It has the function of notifying the repeater COR and also notifying each terminal device connected to the corresponding coaxial cable of a collision detected by another coaxial/optical repeater COR or Tahaster repeater 5REP.

The star repeater 5RFP simultaneously relays incoming signals from any of the (N+1) incoming fiber cables, that is, the transmission lines LTO to LTN, to the same ((N+1)) all outgoing fiber cables, that is, the receiving lines LRO to LRN. It also has a function to detect collisions in the star repeater 5REP, as described later.Therefore, the relayed signals are transmitted to each terminal device AO to
Information signal from Nn and coaxial/optical repeater C0RO~CO
This is a collision signal generated in the RN or star repeater 5REP itself.

FIG. 2 is a block diagram showing the detailed configuration of one of the coaxial/optical repeaters C0RO and star repeater 5REP shown in FIG. 1.

In FIG. 2, the coaxial/optical repeater CORO has a transmitter 12, a receiver 14, a collision detector 16, and a collision condition generator 18 connected by a lead 10 from a connection tap TR of a coaxial cable CA. The transmitter 12 is a circuit that transmits an information signal in a signal format compatible with the characteristics of the coaxial cable CA, and the receiver 14 receives the information signal from the coaxial cable CA, shapes the waveform according to a threshold value, and performs level conversion. It is a circuit. Further, the collision detector 16 is a circuit that monitors the occurrence of a so-called collision in which any two or more of the terminal devices AO to Al connected to the coaxial cable CA start transmitting almost simultaneously. This may be, for example, a circuit that monitors the DC level of the signal on the coaxial cable CA and detects that the DC level increases significantly compared to normal due to the occurrence of a collision. Or, if a collision occurs, the A of the mother signal on the coaxial cable CA? It may also be a circuit that detects a change in pulse frequency. As will be described later, the collision state generator 18 is a circuit that makes the signal state on the coaxial cable CA pseudo-identical to the collision occurrence state. For example, the collision state generator 18 changes the DC level of the signal on the coaxial cable CA as if it were It may be a circuit that forces the level to be the same as when the collision occurred, as if a collision had occurred above.

The input 20 of the transmitter 12 is connected to one electrical signal output 24 of the optical-to-electrical converter (0/E) 33 through one contact a of the changeover switch SWO, and is connected to one electrical signal output 24 of the receiver 14.
6 is the electrical connection through the other contact of the changeover switch SWO.
It is connected to the input 30 of the optical converter (VO) device 28 . The changeover switch SWO responds to a priority control circuit 32 that responds to the other output RD of the receiver 14 and the other electrical output TD of the optical-to-electrical converter 22, so that only one of the contacts a and b is always activated. The coaxial cable CA operates to ensure half-duplex transmission of information signals on the coaxial cable CA.

For example, when receiver 14 receives a signal from coaxial cable CA, lead RD is energized and priority control circuit 3
2 closes the contact A and opens the contact A as shown.

As a result, the received signal is input to the electrical-to-optical converter 28. Further, when the optical/electrical converter 22 outputs a transmission signal to the output 34, the lead TD is energized, and the priority control circuit 32 closes the contact a and opens the contact A, contrary to the illustration. This provides a transmission signal to the transmitter 12.

The input 34 of the collision condition generator 1B is connected to another selector switch S'
It is connected to the electrical signal output CDS of the optical/electrical converter 36 via the contact C of %v1. Switch SWI is controlled by one output 38 of collision detector 16, as described below.

The other output CDR of the collision detector 16 is sent to the electrical/optical converter 4.
connected to the input of o.

The electrical/optical converters 40 and 28 are light emitting elements that output light with different wavelengths λ0 and λ1, respectively, according to input electrical signals, and have respective optical outputs 43. and 44 are combined into a composite optical signal having wavelengths λ0 and λ1 by an optical combiner 46, and outputted to the optical fiber cable LTO.

The optical-to-electrical converters 36 and 22 are photoelectric conversion elements that convert input optical signals into corresponding electrical signals, and the respective optical inputs 47 and 48 are connected to the optical fiber cable LRO via a wavelength filter F. . Wavelength filter F
is a filter that provides an optical component having a wavelength λO to an output 48 and an optical component having a wavelength λ1 to an output 47 of the composite optical signal received from the optical fiber cable LRO. Although the configuration of the coaxial/optical repeater CORO has been described, the same applies to the other coaxial/optical repeaters COR1 to C0RN.

The fiber optic cable LTO is coupled to the wavelength filter FO of the Sternpeter 5BEP. Similar to the wavelength filter F of the coaxial/optical repeater CORO, the wavelength filter FO performs composite optical compensation of the input LTO by combining the optical component with the wavelength λO and the wavelength "
Separates into light components with λ1 and outputs the former toe-e
, the latter is output to output 102-0. One output 100-0 of the wavelength filter FO is input to the optical-to-electrical converter RAO, converted into an electrical signal, and output to the lead 104-0. Similarly to the optical fiber cables LTI to LTN4 from the other coaxial/optical repeaters COR1 to CORN, the output 1 of one of them is passed through wavelength filters F1 to FN, respectively.
00-1 to 100-N are optical/electrical converters RAI to RAM
is input. These optical/electrical converters RAO-RAM
The electrical signal outputs 104-0 to 104-N are OR circuits to
ll, which is logically summed and outputs 1
It is output on 08. This OR output 108 is connected to the input of the electrical-to-optical converter TA, where it is again converted into an optical signal having the wavelength λ1 and outputted to the output 110.

The other output 102-0 of the wavelength filter FO, ~FN
102-N, an optical component having wavelength λ0, is coupled to the input of optical coupler 112. Optical coupler 112 combines the optical signals of these inputs 102-0 to 102-N, and its output 114 is coupled to opto-to-electrical converter RB.

The optical-to-electrical converter RB generates an electrical signal on a lead 116 in response to the optical signal at the input 114, and the lead 116 is connected to the collision signal generating section O8C.

Optical/electrical converter RAO~RAM output 104-0~10
4-N is also connected to the input of the decoder 11B. When signals are applied almost simultaneously from at least two of these inputs 104-0 to 104-N, the decoder 118 determines that a collision has occurred between at least two coaxial/optical repeaters. This circuit energizes its output 120. Output 1201i Collision signal generator O8C
is connected to the other input of the

The collision signal generating unit OSC is a circuit that generates a collision signal in response to the activation of the input 116 or 120, as will be described later, and its output 122 is connected to the electrical/optical converter TB. The electrical/optical converter TB is a light emitting element that generates an optical signal having a wavelength λO at the output 144 in response to the electrical signal on the lead 122.

Optical outputs 110 and 1 of electrical-to-optical converters TA and TB
24 is coupled to a light combiner 126, and the light combiner 126, like the light combiner 46 of the coaxial/optical repeater C0RO,
0 and λ1 are combined to generate a composite optical signal having both wavelengths at output 12g. The composite optical signal output 128 is coupled to fiber optic coupler 18G through which it is simultaneously transmitted to each optical fiber cable LRO-LRN.

In normal operation, either communication terminal device AO-A
The information signal transmitted from I over the coaxial cable CA is received by the receiver 14 of the coaxial/optical repeater CORO from the tag TR. The output RD of the receiver 14 is thereby energized, and the contact of the changeover switch swO is closed by the priority control circuit 32. The information signal is therefore sent from receiver 14 to electro-optical converter 28 where it is converted into an optical signal of wavelength λ1. This optical signal is transmitted from the optical combiner 46 through the optical fiber cable LTO to the star repeater S R
The wavelength filter FO of the EP separates the light component into a light component having a wavelength λ1. This is given to the optical-to-electrical converter RAO by the output 100-0, converted into an electrical signal, and inputted to the OR circuit 1oll. Output 108 of OR circuit 106
is again converted into an optical signal having wavelength λ1 by the electrical-to-optical converter TA, and transmitted to the optical fiber cables LRO to LRN from the optical combiner 126 and the optical fiber coupler to all the coaxial and optical repeaters CORO-CORN. .

In the coaxial/optical repeater C'ORO, which receives this information signal from the optical fiber cable LRO, the optical component of wavelength λ1 is separated into an output 47 by the wavelength filter F, and converted into an electrical signal by the optical/electrical converter 23. It is output to lead 24. At the same time, the lead TD is also energized, but the priority control circuit 32 has the lead RD energized first and is in the state of receiving information signals from the terminal device, so the contact a of the changeover switch SWO is kept open. There is. This information signal is therefore never transmitted to the coaxial cable CA.

All other coaxial and optical repeaters COR1>CORN respectively transmit this information signal received from the optical fiber cables LRI-LRN to the respective coaxial cables CB-CN. In the coaxial/optical repeaters COR1 to C0RN, unless the information signal is already received from the coaxial cable CB-CN at that time, the lead TI by the optical/electrical converter 22)
By energizing the priority control circuit 32, the changeover switch SWO
, closes its contact a, and opens the same. Therefore, the information signal at the output 24 of the optical-to-electrical converter 22 is transmitted to the transmitter 12.
The transmitter 12 transmits this information signal to the corresponding coaxial cable CB-CN via the lead jO and the connection tap TR. In this way, the information signal transmitted from any terminal device AO to Al of the coaxial cable CA is transmitted to the coaxial/optical repeater C0RO, the star repeater S REP, and the coaxial/optical repeater COR1 to C0RNI.
It is transmitted to the terminal device B O=N n via the terminal device B O=N n. Note that the signal is directly transmitted to other terminal devices connected to the coaxial cable CA from that axial cable.

By the way, suppose, for example, that two terminal devices connected to the coaxial cable CA start transmitting almost simultaneously. This collision state is detected by the collision detector 16 of the coaxial/optical repeater CORO, and is transmitted to the electrical/optical converter 40 as a collision detection signal CDR. The electrical/optical converter 40 converts the collision detection signal into an optical signal having a wavelength λθ, which is transmitted from the optical combiner 46 to the optical fiber cable LTO and then sent to the star repeater 5REP.

In the star repeater 5RFP, the wavelength filter FO separates the collision detection signal of the wavelength λ0 received from the cable LTO and outputs it to the output 10. This optical signal is sent to the optical-to-electrical converter RB via the optical coupler 112'ff, where it is converted into an electrical signal and is converted into a collision signal generator OSC.
is applied to one input 116 of the . Collision signal generation part OS
In response to this, C generates a collision signal +V-do 122,
This is again converted into an optical signal of wavelength λO by the electrical-to-optical converter TH. This optical signal is sent from the optical combiner 126 and the optical fiber coupler 13G to the optical fiber/? cable LRO
-Transmitted as a collision signal to the LRN.

Coaxial/optical repeater CORO has optical fiber/9 cable LR
The optical component of wavelength λ0 received from O is separated into an output 48 by a wavelength filter F as a collision signal, which is outputted to an output CDS by an optical/electrical converter 36 as an electrical signal.

However, the collision detector 16 of the coaxial/optical repeater C0RO that detected the collision on the coaxial cable CA energizes the other output 38 to drive the changeover switch sw1 and open the contact C, so a collision condition occurs. device 18 is not driven by the output CDS.

However, since the collision detectors 16 of the other coaxial/optical repeaters C0RI to CORN that did not detect a collision on the coaxial cable de-energize the output 3B, the contact C of the changeover switch SWI is held in the closed state. ing. Therefore, the collision signals of wavelength λO received from the cables LRI to LRN are converted into electrical signals CDS by the optical-to-electrical converter 36,
Activate each collision condition generator 18. The collision state generator 18 forces the signal state of each cable CB-CN into a pseudo collision state as described above. This allows each communication terminal device BO to Nn to know that a collision has occurred.

Note that the terminal device AO connected to the coaxial cable CA
At monitors the signal state on the coaxial cable CA by each collision detection circuit, and independently detects the occurrence of a collision.

By the way, even if no collision occurs on each coaxial cable CANCN, the information signal is transferred to the optical fiber cable LTO.
~Transmitted by LTN to star repeater 5REP,
Here, a collision may occur between the optical fiber cables LTO to LTN, that is, between the coaxial cables CA to CN. In this case, the optical fiber cable LT ON
Since information signals are transmitted from at least two of the LT H, the decoder 118 of the star repeater 5RFP
Due to this, it is detected that at least two corresponding inputs among the inputs 104-0 to 104-N are energized, and a collision signal generator 08Cf is transmitted through the lead 120t.
t drive. By this, - the aforementioned coaxial cable CA
As in the collision case above, the collision signal is transmitted to all coaxial/optical repeaters CORO-CORN as an optical signal of wavelength λ0. In this case, which coaxial/optical repeater CORO
Since the collision detector 16 of -CORN is also not operating, the contacts C of all changeover switches SWI remain closed.

Therefore, the collision state generators 1B of all repeaters CORO to CORN are activated, forcing the signal state of all coaxial cables CA-CN to a collision occurrence state. This causes the terminal device A O-N n to know that a collision has occurred.

By having the coaxial/optical repeater according to the present invention configured as described above, it is possible to fully interface between coaxial cables and optical fiber cables, and to completely perform regenerative relay and collision processing of information signals. . Therefore, by taking advantage of the characteristics of the coaxial cable communication system and the optical fiber communication system, a communication network that organically combines the two can be realized. These communication networks use optical fiber transmission lines as the main line, so they can achieve high transmission speeds, are immune to noise, are not affected by lightning strikes, etc., and use coaxial cables on the branch lines to connect communication terminal equipment. Easy tap connection with the pipe and construction work can be carried out easily.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of an L7'c local communication network using a coaxial/optical repeater according to the present invention, and Fig. 2 shows a detailed configuration of the coaxial/optical repeater and star repeater shown in Fig. 1. FIG. CORO... Coaxial/optical repeater 12... Transmitter 14... Receiver 16... Collision detector 18... Collision condition generator 22.36... Optical/electrical converter 28.40... ...Electrical/optical converter 46...Photosynthesizer F...Wavelength filter 5REP...Stern filter 106...OR circuit 113...Optical coupler 11g...Decoder 126...Photosynthesis device 130... optical fiber coupler FO... wavelength filter RA, 0. RB...Optical to electrical converter TA, TB...Electric to optical converter Patent applicant Ricoh Co., Ltd.

Claims (1)

[Claims] One of a plurality of optical transmission lines connected to a coaxial cable and a star repeater to which a plurality of communication terminal devices are commonly connected.
In a coaxial/optical repeater of a communication network that mutually relays signals between two devices, the coaxial/optical repeater performs mutual conversion between the electrical signal of the coaxial cable and the optical signal of the optical transmission line. a signal transmitting/receiving means for transmitting and receiving signals through the coaxial cable; and a collision detecting means for detecting a transmission collision in the coaxial cable to generate a collision detection signal, and transmitting the collision detection signal to the optical transmission line by the signal transmitting/receiving means. , a coaxial/optical relay characterized in that the signal transmitting/receiving means includes, when the signal transmitting/receiving means receives a collision signal from the star repeater through the optical transmission line, a collision state generating means that changes the signal state on the coaxial cable to a collision state. vessel.