JPS60138504A - Star coupler - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of a cascade star coupler while forming an optical branching path by bundling and fixing an external optical fiber and an internal optical fiber with a smaller diameter than it in different ferrule, and putting them opposite to each other across a connector. CONSTITUTION:When a coupler and the external optical fiber are coupled with each other, a leaf spring 11 is fixed to the projection 12 of an adapter 10 through a ferrule 9, which is pressed in. Namely, the ferrule 9 is fixed as mentioned above and the characteristics are confirmed, so the ferrule 9 and adapter 10 are adhered to each other. In this case, they are not fixed by adhesion and ferrules 9 may be applied with the force of a spring to make their coupling smooth. Further, a connector plug wherein external optical fibers for transmission and reception are paired is shown by 13. None of discharge formation, discharge splicing, and axial shift control is necessary, so a cascade star coupler is manufactured easily.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical system for passively branching and adding optical signals.
In a network, it relates to a star coupler that has the function of not returning optical signals to its own station.

[Technical background of the invention and its problems]

A star coupler, T
In ring-type and path-type networks in which optical networks are formed using type couplers, electrical processing is required for collision detection, making the system complex. In the cascade star network described below,
Since the optical signal does not flow back to the own station, cost reduction becomes easy.

Now, an example of the system configuration of a cascade star network is shown in Figure 1, where one star unit (a) is composed of two end couplers 1 and one center coupler 2. Each unit 1 is connected by an optical repeater 3.

The functions (internal structure) of such a constituent unit are as follows:
As shown in Figure 2, the end coupler J has one main port and three branch ports, and the center coupler 2 has a main port (2/i9) and two branch ports. In other words, the signal input from the transmitting terminal of the station is divided by the coupler to the receiving terminals of other stations, and
The signal is sent to other converters through the main optical path, and eventually sent to all receiving terminals other than the own station.

In this case, if the distribution ratio of each optical distribution section is set to a predetermined value, signals input from all terminals will be transmitted to all stations other than the own station with the same loss.

Conventional examples of the internal structure of this unit coupler (end coupler or center cuff) for dogs are shown in FIGS. 3(a) to 3(d). In this example, a 4-terminal pair is used, and since the optical signal is not returned to the own station, four types of 1×3 element Casolas with different distribution ratios (shown on the right side of the figure) are used. In Fig. 3, the mark in Fig. 2 is an l x 3 element coupler. Also, the optical fiber has a core diameter of 80 μm and an outer diameter of 125 μm.
0.25 GI type-quartz fiber is used. It has been announced that the loss between each branch is within the range of 13.9 to 21.5 dB.

By the way, in the above case, the element coupler is manufactured by controlling the taper shape 4 and the axis misalignment of the connection part 7 between the tapered fiber bundle 5 and the fiber 6, so the equality of the distribution ratio can be accurately determined. It's difficult to get it out. In addition, when manufacturing, first, eight sets of tapered fiber bundles with different shapes were made by electric discharge molding, and then one fiber and electric discharge tin were sliced, a 1×3 element coupler was made, and then Each element turnip,
It takes a lot of work to manufacture because it is made by electrical discharge splicing of 12 pairs of optical fibers. Furthermore, since quartz fibers are used, there is a drawback that the fibers are easily broken, especially at the connection point between the tapered fiber bundle and the fibers.

[Purpose of the invention]

The purpose of this invention is to create a star
To provide a star camera in a coupler that is easy to manufacture and has less variation in characteristics.

[Summary of the invention]

This invention consists of (1) bundling a large number of internal optical fibers with smaller diameters than the 11 external optical fibers and fixing them to 7 errules, fixing the external optical fibers to the other 7 errules, and making both optical fibers face each other via connectors; Furthermore, an optical branch is formed by dividing the internal optical fiber into multiple parts.
This is a star coupler formed using a plurality of these optical branching parts.

[Embodiments of the invention]

First, the concept of this invention will be explained using the coupler shown in FIG. In this example, a star net is formed by configuring one unit with four terminal pairs, two end couplers J, and one center coupler 2.

As shown in FIGS. 4 and 5, the fiber 8 inside the coupler has the same shape and is made of plastic fiber that is strong against bending. If the outer diameter of the outer fiber 9 is D, then D=(2m+1)d, where m=o , 1, 2... By determining the outer diameter d to satisfy the following relationships, when bundled in a circle, the outer diameter of the circumscribed circle becomes D using (3m" + 3m + l) books. That is, At the main port station where the largest distribution capacity is required, a fiber bundle with an outer diameter is coupled to an outer seven eyeper with an outer diameter, and the fiber bundle has a close-packed structure.In that case, The minimum distribution ratio according to the area filling ratio for light incident from the external fiber is as follows.The smaller the fiber diameter d in the coupler is, that is, the larger m is, the more freely the distribution ratio can be set, and the loss due to the area filling ratio is However, the diameter d cannot be made smaller due to ease of handling, strength against bending, and manufacturing issues.

This means that even if the port stations are coupled using the minimum distribution ratio, that is, one of the seven eyeper bundles, the maximum permissible reception level on the receiving side may be exceeded.

In this case, it is possible to avoid reducing the diameter d unnecessarily by intentionally providing a loss element to that one fiber. Examples of specific methods include: (1) Lengthen only the fiber and wind it in a spiral to provide loss due to mode dispersion.

■ Place a large fiber in between to provide a scattering element.

■Use a V-groove to leave a small gap in the middle.

■ Use special fibers with poor loss customization.

etc. are possible.

Next, to show an actual production example, the star coupler unit has 2 end couplers and 11 center/couplers as above.
Each unit has 4 ports, and the unit has 8 ports in total. Then, the external phino R-diameter was designed to be m=2 with a symmetrical value of 500 μm. That is, the fiber diameter inside the coupler is d=100μ
m, the densest fiber bundle will be 19.

As shown in Figure 2, the distribution ratio is 6 end couplers between the main port, port branch, and port, 15 wires between the branch, port branch, and I-to, and 2 wires between the main port, port branch, and port. ,branch·,! ? -) - Branch ports are now connected with one cable. By doing so, the loss of one shell between all of the eight ports of the star coupler, unit, and to, which are composed of three couplers, becomes approximately equal to the opposition.

Now, the connection with the external fiber is made by a connector, and the transmitting and receiving fibers are paired, so the transmitting and receiving fibers can be connected at the same time.Using a connector with a structure that prevents it from entering the wrong way, it is possible to easily connect and disconnect each station at once. did.

Furthermore, the fiber bundle was passed through seven errules inside the coupler, bonded, polished, and then passed through an adapter to be fixed. To give a concrete example, as shown in FIG. 5, a ferrule 9 is passed through an adapter 10, a leaf spring 1 is fixed to a protrusion 12 of the adapter 10, and the ferrule 9 is pushed into the adapter 10. That is, after the ferrule 9 is fixed by the above-described method and the characteristics are confirmed, the ferrule 9 and the adapter 10 can be fixed with adhesive. It is also conceivable to apply a spring-like force to the ferrules 9 to smooth the connection between the ferrules 9 without fixing them with adhesive. Reference numeral 13 designates a pair of connectors for transmitting and receiving external terminals.

〔Effect of the invention〕

According to this invention, there is no need for electrical discharge forming, electrical discharge splicing, or axis misalignment control.
Couplers can be made. Moreover, since no special parts are used and anyone can make it in a short time, it is possible to make it less stylish. Especially when plastic fibers are used in this invention,
It also becomes possible to downsize. Therefore, the industrial value of this invention is extremely large.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of the star system configuration of a cascade star camera, Fig. 2 is a block diagram showing the internal structure of a cascade star coupler, and Fig. 3 (,)~
(d) is a perspective view showing an element coupler that performs distribution in a conventional cascade star coupler; FIG. 4(a) y (
b) is a plan view showing an example of the arrangement of optical fiber bundles in a star coupler according to an embodiment of the present invention, and FIG. 5 is a sectional view showing an example of coupling between the coupler and external optical fibers. 1... End coupler, 2... Center coupler,
? ...Optical repeater, 4...Theno J in conventional element coupler? - shaped part, 5... bundle of optical fibers used for distribution within the coupler, 6... internal optical fiber for connection with external optical fiber, 7... connection part, 8...
Optical fiber used for distribution within the coupler, 9...7 errule, 10...adapter, 1...plate spring, 12...
−・Protrusion of adatsuta. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 1, *, '-1-

Claims (3)

[Claims] (1) Star network with mutual signal transmission function of multiple terminal stations
In a cascade star coupler that uses couplers to connect subordinately to expand the number of terminal stations, the port whose purpose is to connect the constituent star couplers is called the main port and is called the X port. The port that connects the star coupler with other terminals is called a branch port, and when there is a Y port, each port is composed of one input terminal and one output terminal, and the inside of the coupler is In this case, the basic element is an internal optical fiber whose diameter is smaller than that of the external optical fiber, and the output terminal of the main port mentioned above is connected to the main port other than the own station.
They are coupled to the input terminal of the port using mh fibers and n1 fibers to the input terminal of the branch port, and are connected to external optical fibers by bundling a total of -IY, and the branch ? - The output terminal of the main station is connected to the input terminal of the above main port using flj pieces, and to the input terminal of the branch port other than the local station using Jk pieces, respectively, and connected to external optical fibers by bundling the total. A star coupler characterized by being configured as follows. (2) The internal optical fiber used in the internal optical fiber bundle has an outer diameter d that satisfies the following, where D is the outer diameter of the external optical fiber, D÷(2m+1)・d (where m is a natural number); The star coupler according to claim 1, wherein the outer diameter of the circumscribed circle of the internal optical fiber bundle is set to be D with respect to the output terminal and the input terminal of the main port. . (3) The star coupler according to claim 1, wherein the optical path between the ports connecting with the external optical fiber with a low weight is performed by giving a certain loss to the internal optical fiber within the coupler. .