JPH0256130A - Optical ring network - Google Patents

Abstract

PURPOSE:To eliminate need for giving an address to a transmission signal by allocating a specific optical frequency to each node so as to correspond the address of each node to the optical frequency thereby applying the communication between nodes. CONSTITUTION:Optical transmission lines 1, 2 and plural communication terminal equipment nodes 61-6n are connected by optical multiplexers/demultiplexers 51-5n whose transparent frequency is variable and optical multiplexers/ demultiplexers 41-4n whose transparent frequency is fixed. Each one frequency is allocated to the nodes 61-6n and the optical multiplexers/demultiplexers 41-4n used as a demultiplexer belonging to the node are fixed to the frequency. The accessing between nodes is implemented by tuning the optical multiplexers/ demultiplexers 51-5n used as insertion equipments having a sender side optical source frequency to the transparent frequency. Since it is not required to give addressing to the transmission signal in this way, there is no restriction in number of nodes.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical communication system in which a plurality of nodes perform node open communication using a common optical 7-IPA transmission path, and particularly relates to an optical communication system in which a plurality of nodes perform node open communication using a common optical The present invention relates to a light source-shaped communication system that is capable of connecting a larger number of nodes to a network than before.

A circular communication system using optical fibers is useful as a method for realizing a broadband user-network interface that allows users to access broadband signals such as moving images and high-speed data.

[Conventional technology]

The light source soft rope should have the basic configuration shown in Figure 6.

In the figure, 100 is a center, 101 to 103 are communication terminals, 104 . 105 represents an optical (fiber) line.

The center 100 and the communication terminals 101 to 103 are connected to the optical line 10
4 105 are connected in a ring.

Conventionally, in this type of network, each communication terminal often had an optical/electrical coupling circuit as shown in FIG.

In the figure, 106, 107 are electrical/optical converters (abbreviated as Elo in the figure), 110. 111
is the original control unit, 108. Reference numeral 109 represents an optical/electrical conversion unit (abbreviated as Q/E in the figure), and 112 represents a terminal control unit.

The optical signal propagating through the optical path 104 is transmitted through the optical-to-electrical converter 10
8, the signal from the terminal control section 112 is superimposed on the original yarn control section 111, and the electrical/optical conversion section 10
At step 7, the signal is converted into an optical signal again and propagated on the optical path 105.

Furthermore, in such an optical loop network, if any one of the communication terminals connected in a ring has a failure, communication throughout the loop becomes impossible.

In order to eliminate this drawback, conventional practice has been to form the optical path into a double loop as shown in FIG.

That is, optical lines 104 and 105 are used to create two communication paths in opposite directions, and normally one of them is used to turn off communication, but in the event of a failure, communication is performed using the two communication paths. ing.

As shown in the figure, in such a conventional configuration,
Since optical circuits do not have an identification function, the receiving side can distinguish whether the signal is needed by adding the destination address to the beginning of the time-divided transmission signal.

[Problem to be solved by the invention]

In the conventional light source type communication network as described above, there is a control problem in that the destination address must be added to the beginning of the transmitted signal. There are limits to sexuality, and
The number of nodes that can be connected was restricted.

SUMMARY OF THE INVENTION In view of the drawbacks of the conventional methods, it is an object of the present invention to provide a light source type communication method that does not require addresses to be attached to transmission signals and is not limited by the number of nodes.

[Means to solve the problem]

According to the invention, the above-mentioned object is achieved by the means specified in the claims.

That is, the present invention provides an optical ring network communication system in which nodes such as a center node and a plurality of communication terminals are connected in a ring via optical lines, and each node receives an optical signal on an optical transmission path. or an optical multiplexer/demultiplexer for extracting the optical signal or transmitting an optical signal onto an optical transmission path, and a light source capable of changing the frequency of the oscillated light, and using an optical multiplexer/demultiplexer as the optical multiplexer/demultiplexer. In addition, it is a light source network that allocates at least one unique optical frequency to each node and communicates between each node.

[For production]

The present invention optically frequency multiplexes each signal and uses an optical multiplexer/demultiplexer as an optical drop/adder at each node as described above, and the optical drop/dropper is lossless in principle. This technology differs from conventional technology in that there is no need to attach a destination address to a transmitted signal.

Therefore, according to the present invention, there is no restriction on the number of nodes, and it is possible to construct a high-performance communication system with high system expandability.

〔Example〕

FIG. 1 is a diagram showing the configuration of a light source-shaped communication network according to an embodiment of the present invention.

The overall configuration of the communication network is the same as that shown in FIG. 6 above.

In the figure, 1 and 2 represent seven optical fiber transmission lines, 3 is a center node, 4. -4n optical multiplexer/demultiplexers used as optical splitters, 51-5n optical multiplexer/demultiplexers used as optical adders, and 61-6° represent communication terminal nodes.

In the figure, optical splitters 4, to 4o are optical multiplexers/demultiplexers with fixed transmission frequencies, and optical adders 5 to 5n are optical multiplexers/demultiplexers with variable transmission frequencies.

In this example, each node has one frequency (f,
f2. ..., f,), and fix the transmission frequency of the optical multiplexer/demultiplexer used as a splitter belonging to that node to that value. Access between nodes is possible by tuning the transmitting side light source frequency and the transmission frequency of the optical multiplexer/demultiplexer used as an inserter.

For example, in order to access 61 from node 6°, first, the transmission frequency of optical multiplexer/demultiplexer 5□ of node 6□ is set to y4 to be fl, and the light source frequency of node 6□ is set to fl and is transmitted. The optical multiplexer/demultiplexer 41 of the node 6 is set in advance to transmit only f.

It is possible to selectively receive the signal of frequency F transmitted from node 6□.

When a semiconductor laser is used as a light source, the light source frequency can be tuned by changing the temperature and bias current.

FIG. 2 is a block diagram showing an example of the device configuration within the /-domain.

In the same figure, 7 and 8 are elementary control units, 9 is a common control unit, and 1
0 is an optical/electrical converter (abbreviated as O/E in the figure), and 11 is an electrical/optical converter (abbreviated as E in the figure).
(displayed as lo).

FIG. 3 is a diagram showing an example of the configuration of an optical waveguide type double ring resonant spoken channel demultiplexer used as an optical multiplexer/demultiplexer for an optical drop/dropper. 13
2 represents a ring-shaped optical waveguide, 14 a thermal electrode, 15 a lead wire, and 16 an optical directional coupler.

In this dual ring type channel splitter, the diameters of the ring waveguides are different from each other, and the resonant frequency interval is the least common multiple of the resonant frequency intervals of each ring.

In addition, the frequency of the resonant frequency can be adjusted by changing the propagation constant (equal index of refraction) of the waveguide, and in reality, it is
As shown in Fig. S3, this can be realized by setting electrodes on the waveguide for performing thermal modulation or modulation by electro-optic effect.

FIG. 4 schematically shows the frequency dependence of the transmission loss of the double ring resonant spoken channel splitter shown in FIG.

The transmission loss repeatedly becomes zero at constant frequency intervals ΔF. Therefore, the maximum frequency band available for frequency multiplexing is ΔF.

Further, if the width of the low transmission loss region is Δf, the number N of channels that can be frequency multiplexed is N=ΔF/Δf.

Figure tlS5 shows an example of calculating the frequency dependence of the transmission loss of a ΔF = 40 GHz'' ChCh designed double ring resonant spoken channel duplexer.

In this calculation example, a silica-based optical waveguide with a refractive index of 1.46 is assumed, and the radius of each ring waveguide is 5736.8μ.
m, 6556.3 μTsuru, 1 is 0.12 for the power coupling coefficient between each ring waveguide and input/output optical waveguide, and 2 is o, ooe for the power coupling coefficient between ring waveguides.

In this calculation example, the worst value of crosstalk is 14 dB, and it is considered that almost no deterioration due to crosstalk occurs.

Also, the 3dB transmission bandwidth Δf is 190MHz,
The number of channels that can be frequency multiplexed is 210.

This indicates that the number of nodes is 20 times or more compared to the conventional optical path method.

In addition, there is essentially no increase in loss due to the drop/add device, and it does not become a limiting factor for the number of nodes.

On the other hand, a tunable optical multiplexer/demultiplexer can use a movable diffraction grating as a wavelength separation element, or can be configured with a double ring resonator.

However, in an optical multiplexer/demultiplexer using a diffraction grating, the number of channels is limited by the coupling loss between the optical fiber and the diffraction grating, and the maximum number of channels realized to date is about 20 channels.

Furthermore, in order to fabricate a double ring resonator with the same ΔF as the double ring resonator described above, the radius of the ring must be approximately halved, and radiation loss due to bending of the waveguide will occur. There is a possibility that it will increase significantly. Therefore, it is difficult to increase the number of channels even in the case of a double ring resonator.

Therefore, it is desirable that the optical multiplexer/demultiplexer for a drop/adder according to the present invention uses an optical waveguide double ring resonator as shown in FIG.

〔Effect of the invention〕

As explained above, in this method, the 7 addresses of the node correspond to the optical frequency, so there is no need to attach a destination address to the transmitted signal, and a double ring resonator type channel demultiplexer is used as a drop-adder. By doing so, it is possible in principle to selectively transmit a large number of optical frequencies arranged at narrow wave number intervals without loss, and there are advantages such as connecting a large number of nodes.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a light source type communication network according to an embodiment of the present invention, FIG. tJS4 is a diagram schematically showing the frequency dependence of the transmission loss of a double ring resonator type channel duplexer. Figure 6 showing an example of calculating the frequency dependence of transmission loss of a ring resonator type channel splitter.
The figure shows the basic configuration of a conventional light source soft rope, and FIG. 7 shows the configuration of a conventional communication terminal. 1 2...Optical fiber transmission line, 3...
... Center node, 4. ~4o...
...Optical multiplexer/demultiplexer used as an optical splitter, 51~
50... Optical multiplexer/demultiplexer used as an optical adder, 6
□～60...Communication terminal node, 78...
・・・・Common control unit, 9 ・・・・Common control unit, 10 ・・・・Optical/electric conversion unit, 1
1... Electricity/optical conversion section, 12...
...optical waveguide, 13,. 13□...Ring-shaped optical waveguide, 14...Thermal electrode, 1
5 ・・・・・・Lead wire, 16 ・・・・・・
Optical directional coupler agent Patent attorney Honma
Takashi ft fz ---h --fn Frequency diagram Frequency board (ωna) Raku diagram

Claims (1)

[Claims] An optical ring network communication system in which a center node and nodes such as a plurality of communication terminals are connected in a ring via optical lines, and each node extracts an optical signal on the optical transmission path. or an optical branch/adder for sending optical signals onto an optical transmission path;
and a light source capable of changing the frequency of the oscillated light,
An optical ring network characterized in that an optical multiplexer/demultiplexer is used as the optical branch/adder, at least one unique optical frequency is assigned to each node, and communication is performed between the nodes.