JPS63227139A - Communication system - Google Patents

Abstract

PURPOSE:To exchange and communicate information large in capacity with high quality and at high speed by mutliplexing optical signal having plural frequencies and plural wavelengths, which is outputted from plural terminals, to an optical cable, and instructing tuning or a selection by the terminal. CONSTITUTION:In each node being a basic unit, terminals 12a-12c are connected to a pair of input/output corresponding to an optical star coupler 10 through the corresponding interface parts 11a-11c and an optical fiber cable 16. Also, to specific input/output ports of the coupler 10, a controller 13 and a remote bridge 14 for transmitting a data between the nodes of a long distance are connected, respectively, and the bridge 14 is connected to the controller 13 through a bus 15. The controller 13 executes a mutual control of a frequency allocation of a line channel, or wavelength of an optical signal to be used, etc., and to a signal line of an arbitrary output port, an optical signal different in wavelength and frequency of all input ports is superposed, and selected and received by each terminal, and the information large in capacity can be exchanged and communicated with high quality and at high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a communication system that performs bidirectional communication using optical multiplex signals.

[Prior Art] In conventional communication systems, particularly in the field of LAN (Local Area Network), transmission methods such as baseband type, broadband type, or optical fiber type are used, and transmission speeds and access methods vary depending on the application. Various products such as different communication devices have been announced.

CATV has also been put into practical use for video signal transmission.

On the other hand, in terms of switching functions compatible with these various transmission systems, electronic switching equipment is still the mainstream, and with the spread of optical communications, research on optical switching equipment is currently being actively conducted.

[Problems to be Solved by the Invention] The above conventional example has the following problems.

(1) When performing two-way video transmission using CATV, line amplifiers become very expensive and channel allocation becomes difficult. It is also difficult to communicate between specific subscribers.

(2) When exchanging using an electronic exchange, quality deterioration occurs due to crosstalk when transmitting high frequency signals. Further, in order to perform arbitrary N-to-N exchange, a circuit scale of NXN is required, and when the number of subscriber systems N increases, the circuit scale increases in proportion to the square of N.

(3) Although research on optical switching equipment is actively being conducted, it has not yet reached the stage of practical use.

(4) It is difficult for existing LANs to cope with the increase in transmission capacity.

The present invention has been made in view of the above conventional example, and an object of the present invention is to provide a communication system that can exchange and communicate large amounts of information with high quality and at high speed.

[Means for Solving the Problems] In order to achieve the above object, the communication system of the present invention has the following configuration. , the terminal has output means for modulating transmission data into a first frequency signal, converting it into an optical signal of a predetermined wavelength, and outputting it; input means for inputting an optical signal of a predetermined wavelength from a wavelength multiplexed optical signal; converting means for converting the optical signal of the predetermined wavelength into an electrical signal; and means for receiving an electrical signal having a second frequency; The apparatus includes means for multiplexing optical signals having different wavelengths, and control means for instructing at least one of frequency tuning and wavelength selection at the transmitter terminal and the receiver terminal.

[Operation] In the above configuration, the terminal modulates the transmission data into a first frequency signal, converts it into an optical signal of a predetermined wavelength, and outputs it, receives the optical signal of a predetermined wavelength, and converts it into an electrical signal,
A signal of a second frequency signal is received. Optical signals having multiple frequencies and multiple wavelengths output from multiple terminals are multiplexed on the optical cable, and the control means controls the frequency tuning and optical signal at the transmitting terminal and receiving terminal that wish to transmit or receive. Each terminal that wishes to transmit and receive is instructed to perform wavelength matching.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Description of Communication System (Figure N1)] Figure 's1 is a diagram showing the basic configuration of the communication system of the first embodiment.

Figure 2 is a diagram showing the configuration of an optical star coupler node corresponding to each node (node 1 to node 3) in Figure 1, which is the basic unit in the configuration of this system. First, let's talk about the configuration of the nodes in Figure 2. To explain, in each node, each terminal 12
(12a to 12C) correspond to the corresponding interface section 11 (
lla to 11c), and each interface unit 11
are connected to a corresponding pair of input/output ports of the optical star coupler 10 via optical fiber cables 16 (16a to 16c). Further, a controller 13 and a remote bridge 14 that transmits data between distant nodes are connected to specific input/output ports of the optical star coupler 10, respectively, and the remote bridge 14 connects to the controller 13 via a bus 15. connected and controlled by a controller 13.

Each node (node 1 to node 3) in FIG.
Corresponding to the nodes shown in the figure, the long-distance communication line 17 between the remote bridges (14-1 to 14-6) provided at each node is an NTT dedicated line, optical fiber line, etc. Yes, the control line 18 between the controllers is composed of a telephone line, etc., and each controller has a mutual control line 18.
Control signals are sent and received via the node, and control is executed between each node.

With this configuration, communication via multiple nodes is also possible, and at this time, the remote bridge 14 and the controller 13
By combining these, the entire node also plays the role of a repeater with a relay function.

The optical star coupler 10 has n fibers connected to each input/output boat 9, and a pair of input/output lines of each corresponding boat is connected to the interface section 11 or the controller 1.
3. Connected to remote bridge 14. At this time, a signal in which optical signals having different wavelengths and frequencies from all input ports are superimposed is output to the signal line of any output port.

Each interface section selectively receives this signal at a desired frequency and wavelength.

At least one controller 13 is disposed within the node, and is connected to the interface unit 11 via an optical star coupler 10 and to the remote bridge 14 via a path line 15. line status within a node, line “connection”,
In addition to “disconnection” and exchange functions, it also performs all controls such as billing management. At the same time, in long-distance node-to-node communication, since controllers are connected via a modem to a public telephone line, etc., mutual control such as line channel frequency assignment or the wavelength of the optical signal to be used can be performed by handshaking.

[Description of the interface section (Fig. 3)] Fig. 3 is a diagram showing the configuration of the interface section 11 and its connections.
2. Parts common to those in FIG. 2 are indicated by the same symbols.

Transmission data 20 from terminal 12 is modulated by modulator 21 using a unique carrier frequency assigned to the own channel by controller 13 .

This frequency instruction to the modulator 21 is performed by an instruction from the CPU 22. The multiplexer 23 multiplexes the modulated signal 24 from the modulator 21 and the control signals from the CPU 22 (failure check, in-use check, optical wavelength instruction, tuner control, called signal, etc.) and outputs the multiplexed signal. Electro-optical (Elo) converter 8
0 is the electrical signal from the multiplexer 23 at a predetermined wavelength or CP.
It is converted into an optical signal of the wavelength specified by U22 and sent to the optical star coupler 10.

On the other hand, among the optical signals 83 inputted from the optical star coupler 10, only an optical signal having a predetermined wavelength or an optical signal having a wavelength instructed by the CPU 22 is inputted to the optical demultiplexing circuit 84. This optical signal includes transmission data from each terminal and control signals from the controller 13 (failure check, in-use check, optical wavelength instruction, tuner control, calling signal, etc.). The optical signal input from the optical demultiplexing circuit 84 is
It is converted into an electrical signal by an optical-to-electrical (0/E) converter 82, separated by a duplexer 26 composed of a band filter, a band elimination filter, etc., and then sent to the CPU 22 and the variable tuner section 27.
sent to. The variable tuner 27 tunes the input signal at a frequency instructed by the CPU 22, demodulates the modulated input signal, and sends it to the terminal 12 as received data 28.
Output to.

With the above configuration, when the terminal 12 wants to communicate with another terminal within the same node, it specifies the terminal with which it wants to communicate to the CPU 22 via the bus 29. As a result, the CPU 22 passes the multiplexer 23, converts it into an optical signal of a predetermined wavelength by the electro-optical (Elo) converter 80, and transmits the calling terminal and destination designation data (control signal) to the optical star coupler 10. The data is sent to the controller 13 via the .

When the controller 13 receives the above-mentioned control signal, it outputs the reception frequency and reception optical wavelength of the other party terminal, and the transmission frequency and transmission optical wavelength of the other party terminal to the optical star coupler 10 as a response. Of the optical signals from the optical star coupler 10 , the interface circuit 11 receives an optical signal of a wavelength selected by the optical demultiplexing circuit 84 and converts it into an electrical signal by an optical-electrical converter 82 . This electrical signal is branched by a branching filter 26, and a control signal is input to the CPU 22.

When the CPU 22 recognizes the frequency used by the other terminal (transmission/reception frequency) and the wavelength of the optical signal to be used based on the signal from the demultiplexer 26, the CPU 22 sets the modulator 21 and variable tuner 27 to the reception frequency and transmission frequency of the other terminal, respectively. In accordance with the frequency, the wavelength of the output optical signal of the electro-optical converter 80 is specified, and the input wavelength of the sufficient wave circuit 84 is matched with the output wavelength of the other terminal.

Note that this frequency tuning may be such that the other party's terminal matches the frequency of the communication requesting terminal. Alternatively, the transmission frequency from each terminal may be fixed, and the tuning frequency of the variable tuner 27 on the receiving side may be matched to the transmission frequency of the other terminal.

Similarly, for matching the wavelength of the optical signal between terminals, the other terminal may match the wavelength of the optical signal output by the terminal requesting communication, or the wavelength of the optical signal output from each terminal may be fixed. Alternatively, the demultiplexing wavelength of the optical demultiplexing circuit 84 on the receiving side may be matched to the wavelength of the optical signal on the transmitting side.

Furthermore, if there are any unused frequency bands and wavelengths among the frequency bands and wavelengths that can be used in this communication network (node), the controller 4 may allocate those frequency bands and wavelengths to terminals that wish to communicate. good.

By doing so, it is possible to easily add or reduce terminals in the communication system.

[Explanation of Controller Operation (FIGS. 1 to 4)] FIG. 4 is a flowchart of preprocessing for communication by the controller 13, and this program is started in response to a request for communication from the interface unit 11.

First, in step S1, when the interface section 11 of the terminal 12 specifies a counterpart terminal with which the terminal 12 desires to communicate, the process proceeds to step S2, and in step S2, a communication request is sent to the interface section of the counterpart terminal. Check the operation of the other party's terminal. In step S3, it is checked whether communication is possible with the other party's terminal, and if communication is not possible, the process proceeds to step S4, where the terminal 12 is informed via the bus 29 that communication with the other party's terminal is not possible, and the process ends.

If it is determined in step S3 that communication is possible with the other party's terminal, the process proceeds to step S5, where frequency bands and wavelengths of optical signals that are currently not used within the communication network are checked, and instructions are given to the terminal 12 and the other party's terminal in step S6.

According to this instruction, the interface section of each terminal changes either or both of the transmission and reception frequencies, and changes either or both of the transmission and reception wavelengths of the optical signal to perform communication. Note that if the transmission frequency or output optical wavelength of each terminal is fixed, the controller 4 performs step S.
5 is omitted, and in step S6, the transmission frequency and output optical wavelength of the other terminal are instructed to the interface section of each terminal,
Each interface section only needs to set the demultiplexing wavelength of the optical demultiplexing circuit 84 and the tuning frequency of the variable tuner 27 to designated values.

[Explanation of operation of interface unit (Figs. 3 and 5)] Fig. 5 is a flowchart of a program for pre-communication processing by the interface unit 11, and this program is based on C in Fig. 3.
It is stored in the ROM of the PU22. Note that this program is started by a communication instruction from a connected terminal.

This flowchart shows the operations executed in response to the operations of the controller 13 shown in FIG. A partner terminal with which communication is desired is specified to the controller 13 via the converter 80 and the optical star coupler 10. In step Sll, a response from the controller 13 input via the optical demultiplexing circuit 84, the optical-electrical converter 82, and the demultiplexer 26 is waited for, and in step S12 it is checked whether the other party's terminal is capable of communication.

If communication is not possible, the process proceeds to step 313, which notifies the terminal 12, and the process ends; however, if the companion terminal is capable of communication, the process proceeds to step S14, where the controller 13
Either or both of the modulation frequency of the modulator 21 and the tuning frequency of the variable tuner 27 are set in order to correspond to the transmission or reception frequency and the wavelength of the optical signal instructed by the electro-optic converter 80 in step S15. Either or both of the output optical wavelength of the optical demultiplexing circuit 84 and the demultiplexing wavelength of the optical demultiplexing circuit 84 are set, and communication is started in step 316. Note that the settings for the frequency and wavelength of light here are based on the fourth setting as described above.
It goes without saying that this corresponds to the frequency and wavelength of light specified by the controller 13 in step S6 in the figure.

[Explanation of optical star cobra (Fig. 6)] Fig. 6 (A) (
B) is a diagram showing a specific example of a unidirectional optical star doubler used in this embodiment.

Figure 6 (A,) is a diagram showing an optical star coupler with orthogonal piconic taper structure, in which multiple optical fiber cables are connected.
It is fused at part 70. FIG. 6(B) shows a concentrated coupling type optical star coupler using a flat plate mixer 71.

[Explanation of optical demultiplexing circuit (Figure 7)] FIG. 7 is a diagram showing an example of an optical demultiplexing circuit.

The basic components of an optical demultiplexing circuit for wavelength multiplexing transmission are broadly divided into angular dispersion elements such as diffraction gratings and prisms, wavelength selective reflection/transmission films such as dielectric multilayer interference filters, and light guides. There is a wave path.

In FIG. 7, 72 is an optical fiber into which the optical signal 83 from the optical star coupler 10 is input, and 73 is a lens which converts the incident light of the optical signal 83 into parallel light.

Reference numeral 74 is an angular dispersion element that reflects incident light by changing the reflection angle for each wavelength, and 75 is an output lens, which is combined with the angular position conversion by the angle dispersion element 74 to form a light receiving element 76 on the output side.
77. In this way, optical signals with different wavelengths are input to each light-receiving element, and light is demultiplexed.

Note that an optical multiplexer that combines a plurality of light beams into one transmission line can be realized in principle by reversing the input and output terminals of the optical demultiplexing circuit described above.

[Description of Remote Bridge (FIG. 8)] FIG. 8 is a diagram showing the configuration of the remote bridge 14.

The remote bridge 14 is used during communication between the optical star couplers 10 (between nodes), and the remote bridge 14 is connected to a pair of input/output ports of the optical star coupler 10 with an optical fiber cable, and is connected to an NTT dedicated line or an optical fiber. It is connected to a long-distance line 17 such as.

The signal from the optical star coupler 10 is converted into an electrical signal by an optical-to-electrical (0/E) converter 90, and then sent to the controller 13.
The duplexer 91 is controlled via the path line 15 by
(variable tuner group). In order to convert this demultiplexed signal into a frequency assigned to a long-distance transmission channel, a signal from the controller 13 is used to convert the VFO 92-
1 to 92-n, and converts by mixers 93-1 to 93-n. The signal is then transmitted through the multiplexer 94 to the long-distance line 17 by the driver 95. However, if the line 17 is an optical fiber at this time, an E10 converter 96 is required.

In the example of this explanation, the control signal from the controller 13 is sent via the path line 15, but as explained in the terminal interface, it can also be transmitted on an optical signal, separated by a demultiplexer, and extracted. It is possible.

On the other hand, the signal from the long-distance line 17 is sent to the receiver 9.
8 (if line 17 is an optical fiber, O/E
converter 97 is required) and is converted into an optical signal by an electro-optical (Elo) converter 99, and then sent to the optical star coupler 10. However, if the long-distance line 17 is a high-speed digital line, the above functions are performed by digital processing.

[Explanation of controller operation (Fig. 9)] Fig. 9 is a flowchart of communication preprocessing by the controller 13.
This program is started in response to a request for communication from the interface section 11 connected to a terminal in the node desiring communication.

First, in step S20, the interface unit 11 of the terminal 12
Then, the terminal 12 inputs a command specifying the other party's terminal with which it wishes to communicate. If the terminal on the other side is a terminal within the same node, the process advances to step S22 to check whether the terminal on the other side is capable of communication. Incidentally, the operations in steps S23 to S27 are performed in the fourth step.
Since the operations are the same as those in steps 33 to S7 in the figure, the explanation will be omitted.

If the other party's terminal is not located at the same node in step S21, the process proceeds to step S28, where the controller of the other party is informed of the communication destination, terminal instructions, and usable long-distance transmission/reception frequencies through the control line 18, such as a public telephone line. convey. The controller at the other end checks whether the specified terminal is capable of communication, and when the status is returned, the process proceeds to step 32.
In step 9, it is checked whether the terminal on the other side is capable of communication, and if communication is not possible, the process proceeds to step S24, where the terminal with which communication is desired is notified that communication is impossible, and the process ends.

On the other hand, when communication is possible, the controller of the other node checks the available frequency bands within the node among the frequencies that can be transmitted and received at the own node (the other node), and determines the transmission frequency fx and the reception frequency f. do. Then, the carrier frequency of the remote bridge of the node is set to f8, and the frequency is notified to the node with which communication is desired via the line 18. As a result, the process proceeds to step S30, and the controller of the node desiring communication inputs the aforementioned frequency f8°f via the control line 18, and in step S31, the controller of the node desiring communication inputs the optical fiber cable 16, optical star The transmission/reception frequency is specified via the coupler 10.

As a result, the interface section 1 corresponding to the terminal desired for communication
1 sets the tuning frequency of the variable tuner 27 to fx. It goes without saying that this frequency setting may be performed for either or both of the transmission frequency and the reception frequency as necessary.

In step S32, the duplexer 91 of the remote bridge 14
is set to the carrier frequency of the terminal desiring communication, and the VFO 92-i is controlled to output the frequency f by the corresponding mixer 93-1.

In addition, in the above explanation, it was explained that the transmitting and receiving frequency of the terminal wishing to communicate is matched to the transmitting and receiving frequency of the other party's terminal (other node), but for communication within each node, an independent frequency and wavelength are used for each node. Therefore, it is not necessarily necessary to change the transmitting/receiving frequency or the wavelength of the optical signal of the terminal with which communication is desired.

[Explanation of frequency bands (Figure 10)] Figure 1 is a diagram showing the frequency bands used in this example.
Band 110 is allocated to control signals between controllers between nodes, and band 111 is allocated to control signals between controllers between nodes.
indicates the frequency band of the signal used between long-distance remote bridges. Because lower frequencies have less attenuation, relatively low frequency bands are used for long-distance applications.

Band 112 is a short-distance transmitting/receiving frequency band used between the interface sections in each node, and the bandwidth of one video channel (including audio) is 6 MH, and this signal is subjected to analog AM modulation and converted to 6 MH. A guard band of 6 MHz is installed for each line, and a long-distance line (band 111) is installed.
10 channels, 2 channels for short distance (band 112)
0 channel is assigned.

At this time, since intra-node communication is completely independent, it is possible to allocate the same channel to each node, while communication between nodes requires the allocation of a common channel throughout the system.

As described above, this embodiment has the following effects.

(1) By combining an optical star coupler, a controller (PC class), and an interface, it is possible to construct a two-way video network system with a simple exchange function.

(2) Although arbitrary exchange of NXN is possible, in addition to frequency separation, the exchange method uses the wavelength of the optical signal, so NXN
It is possible to handle a large capacity while being small and lightweight without requiring a large circuit scale.

(3) Since the system is based on a distributed control method that controls each node, it is possible to easily scale up or down the system scale, and at the same time, it is also possible to easily handle increases in transmission capacity by using wavelength multiplexing.

(4) By using public telephone lines only when establishing long-distance transmission lines, the system configuration becomes extremely simple.

(5) Compared to mechanical relay exchange transmission, high-frequency signal crosstalk can be reduced, and a high-quality exchange transmission line can be realized.

[Effects of the Invention] As described above, according to the present invention, there is an effect that a large amount of information can be exchanged and communicated with high quality and at high speed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of the communication system of the embodiment. FIG. 2 is a diagram showing the configuration of the optical star coupler node corresponding to each node of the embodiment. FIG. 3 is a diagram showing the configuration of the interface section of the embodiment. 4 is a flowchart showing preprocessing of intra-node communication by the controller, FIG. 5 is a flowchart showing preprocessing of communication by the interface section of the embodiment, and FIGS. 6(A) and 6(B) are optical star couplers. 7 is a diagram showing an example of an optical demultiplexing circuit. FIG. 8 is a diagram showing the configuration of the remote bridge of the embodiment. FIG. 9 is a diagram showing the configuration of the remote bridge of the embodiment. FIG. 10 is a flowchart showing communication preprocessing and is a diagram showing frequency bands used in this embodiment. In the figure, it...interface part (1/F), 12
...terminal, 13...controller, 10...optical star coupler, 14...remote bridge, 17...
Communication line! 8... Control line, 21... Modulator, 2
2...cpU, 23...multiplexer, 26...brancher, 27...variable tuner, 73.75...lens,
74... Angular dispersion element, 76.77... Light receiving element,
80.99...Electric-optical (Elo) converter, 82.9
0... Optical-electrical (○/E) converter, 83... Optical signal, 84... Optical demultiplexer circuit, 91... Demultiplexer, 92...
・VFO193...mixer, 94...multiplexer, 95
. . . Driver, 98 . . . Receiver. Patent applicant: Canon Corporation Figure 2 Figure 3 Figure 4 Figure 5 (A) (B) Figure 6 Figure 9 (B) Figure 10

Claims (3)

[Claims] (1) A communication system that performs communication between a plurality of terminals via an optical cable, wherein the terminal modulates transmission data into a first frequency signal, converts it into an optical signal of a predetermined wavelength, and outputs the signal; Input means for inputting an optical signal of a predetermined wavelength from a wavelength-multiplexed optical signal, conversion means for converting the input optical signal of the predetermined wavelength into an electrical signal, and means for receiving an electrical signal having a second frequency. means for multiplexing optical signals having a plurality of frequencies and a plurality of wavelengths output from the plurality of terminals onto the optical cable, and at least one of frequency tuning and wavelength selection at the transmitting terminal and the receiving terminal. A communication system comprising a control means for giving instructions. (2) Each terminal transmits and receives an optical signal of a unique wavelength, and the control means instructs the terminal desiring to transmit the receiving frequency of the receiving terminal, and the terminal desiring to receive the transmitting frequency of the transmitting terminal,
Claim 1, wherein the terminal desiring to transmit matches a first frequency signal to the receiving frequency, and the terminal desiring to receive matches a second frequency signal to the transmitting frequency. Communications system. (3) The control means instructs the terminal desiring to transmit the receiving frequency and optical wavelength of the receiving terminal, and the terminal desiring to receive the transmitting frequency and optical wavelength of the transmitting terminal, and the terminal desiring to transmit specifies the transmitting frequency and optical wavelength of the transmitting terminal. While adjusting the signal to the receiving frequency and the wavelength of the optical signal to be output to the receiving optical wavelength, the terminal desiring to receive a second frequency signal to the transmitting frequency and the wavelength of the optical signal to be output to the transmitting optical wavelength. The communication system according to claim 1, characterized in that the communication system is adapted to match the communication system.