NZ229583A - Aligning optical fibres: preventing contact with cores - Google Patents

Description

22 9 5 8 3 Priority Date(s): . .17". .W^'. i c. r <?<3 Complete Specification Filed: Class: Publication Date: 2.6. MAR. • P.O. Journal. Wo: ... IS(V2.

N. Z.

NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION METHODPOSITIONING OPPOSED END FACES OF OPTICAL FIBERS We, SUMITOMO ELECTRIC INDUSTRIES, LTD., Of 5-33, Kitahama 4-chome, Chuo-ku, Osaka, Japan, a Japanese company do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- (in £Yi ri5JUNI989J - 1 - (Followed by 1A) -lft- 22 9 5 R 3 €-; BACKGROUND OF THE INVENTION The present invention generally relates to optical communication and more particularly, to a method of positioning opposed end faces of optical fibers in the case 5 where the optical fibers are fusion spliced or temporarily joined with each other.

Fig. 1 shows a known method of positioning opposed end faces of optical fibers 1. In this known method, a contact plate 2 is preliminarily disposed between the end 10 faces of the optical fibers 1 and the end faces of the optical fibers 1 are, respectively, butted against opposite faces of the contact plate 2 so as to be positioned. In this known method, since an end of a core 11 of each of the optical fibers 1 is brought into contact with the contact 15 plate 2, the ends of the cores 11 may be damaged, so that connection loss at the joint between the optical fibers 1 is increased, thereby resulting in deterioration of optical transmission characteristics.

Meanwhile, the known method has been disadvanta-20 geous in that optical transmission between the optical fibers 1 cannot be performed in a state where the optical fibers 1 are butted against the contact plate 2. Furthermore, the known method has such a drawback that misalignment of the optical fibers 1 can be observed only in one direc-25 tion. 22 9 5 8 3 SUMMARY OF THE INVENTION Accordingly, an essential object of the present invention is, with a view to eliminating the above mentioned inconveniences of the known method, to provide a method of positioning opposed end faces of optical fibers, in which the end faces of the optical fibers are, respectively, butted against opposite faces of a contact plate without bringing cores of the optical fibers into contact with the contact plate.

In order to accomplish this object of the present invention, there is provided a method of positioning opposed end faces of optical fibers by butting the end faces of the optical fibers respectively against opposite faces of a contact plate disposed preliminarily between the optical fibers embodying the present invention, wherein cores of the optical fibers are held out of contact with the contact plate.

BRIEF DESCRIPTION OF THE DRAWINGS This object and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which: Fig. 1 is a view explanatory of a prior art method of positioning opposed end faces of optical fibers by using a contact plate (already referred to); Figs.2,3 and 4 are views explanatory of methods 22 9 5 8 3 of positioning opposed end faces of optical fibers by using a contact plate, according to first, second and third embodiments of the present invention, respectively; Fig. 5a and 5b are views explanatory of methods of observing the positioned optical fibers of Figs. 2, 3 and 4; and Figs. 6a to 6d are views indicative of methods of retracting the contact plate away from the positioned optical fibers of Figs. 2, 3 and 4.

Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout several views of the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, there are shown in Figs. 2 to 4, methods of positioning opposed end faces of optical fibers 1 by using a contact plate 2, according to first, second and third embodiments of the present invention, respectively. The optical fiber 1 is constituted by a core 11 and a cladding 12.

In the first embodiment of Fig. 2, a recess 21 having a size larger than a diameter of the core 11 is formed on each of portions of opposite faces of the contact plate 2, with which portions the cores 11 of the optical fibers 1 are, respectively, brought into contact. Thus, when the end faces of the optical fibers 1 have been, 229583 respectively, butted against the opposite faces of the contact plate 2, only the claddings 12 of the optical fibers 1 are brought into contact with the contact plate 1 such that the cores 11 of the optical fibers 1 are held out of 5 contact with the contact plate 2 by the recesses 21.

In the second embodiment of Fig. 3, the contact plate 2 is disposed below an axis of the optical fibers 1. Therefore, in Fig. 3, only lower portions of the claddings 12 of the optical fibers 1 are brought into contact with the 10 contact plate 2 such that the cores 11 and upper portions of the claddings 12 are held out of contact with the contact plate 2.

Meanwhile, in the third embodiment of Fig. 4, a through-hole 22 having a diameter larger than that of the 15 core 11 is formed at a central portion of the contact plate 2. Hence, in Fig. 4, the cores 11 of the optical fibers 1 are aligned with the through-hole 22 such that only the claddings 12 of the optical fibers 1 are brought into contact with the contact plate 2. 20 By employing the constructions of the contact plate 2 shown in Figs. 2 and 4 or selecting the positional relation between the contact plate 2 and the optical fibers 1 as shown in Fig. 3, only the claddings 12 are brought into contact with the contact plate 2 and the cores 11 are held 25 out of contact with the contact plate 2 when the optical fibers 1 have been butted against the contact plate 2. 229583 Therefore, damage to the cores 11 through their contact with the contact plate 2 can be prevented.

Meanwhile, in the case where the through-hole 22 is formed at the central portion of the contact plate 2 as 5 shown in Fig. 4, optical transmission between the optical fibers 1 can be performed by eliminating any optical obstacle between the opposed end faces of the optical fibers 1.

Figs. 5a and 5b show methods of observing misalignment, etc. of the optical fibers 1 by using an optical 10 system such as a microscope in a state where the end faces of the optical fibers 1 have been positioned by the contact plate 2 as shown in Figs. 2 to 4. In Figs. 5a and 5b, the optical fibers 1 are observed from above the optical fibers 1 and a mirror 3 having an oblique reflective surface 3a 15 forming an angle of 45° with the direction of observation of the optical fibers 1, i.e. the direction of the arrows A and B is provided on a side face of the contact plate 2. In Figs. 5a and 5b, images of portions la and lb of the optical fibers 1 can be obtained as shown by the arrows A and B, 20 with the portions la and lb being radially spaced 90° from each other. Namely, the image of the portion la is directly observed from above as shown by the arrow A, while the image of the portion lb is upwardly reflected on the reflective surface 3a so as to be observed from above as shown by the 25 arrow B.

Furthermore, when the contact plate 2 is retracted c c, 22 9 5 8 3 away from the optical fibers 1 after misalignment, etc. of the optical fibers 1 have been observed as described above in a state where the optical fibers 1 are butted against the contact plate 2 so as to be positioned, the contact plate 2 may be brought into contact with the cores 11 of the optical fibers 1, thereby resulting in damage to the cores 11. In order to obviate such a phenomenon, the contact plate 2 is retracted away from the positioned optical fibers 1 in the directions of the arrows C, D, E and F as shown in Figs. 6a, 6b, 6c and 6d, respectively. By employing these retraction methods, the cores 11 of the optical fibers 1 are not brought into contact with the contact plate 2 and therefore, are not damaged.

As is clear from the foregoing, in the method of positioning the opposed end faces of the optical fibers, according to the present invention, only the claddings of the optical fibers are brought into contact with the contact plate such that the cores of the optical fibers are held out of contact with the contact plate.

Therefore, in accordance with the present invention, since damage to the cores through their contact with the contact plate is obviated, deterioration of optical transmission characteristics due to damage to the cores can be prevented.

If an optical obstacle between the opposed end faces of the optical fibers is removed at this time by, for 22 9 5 8 3 example, forming the through-hole at the central portion of the contact plate, it becomes possible to effect optical transmission between the optical fibers.

Meanwhile, in accordance with the present invention, since the mirror having the oblique reflective surface forming an angle of 45° with the direction of observation of the optical fibers is provided on the contact plate, two images of the optical fibers, which are, respectively, emitted from the portions of the optical fibers spaced radially 90° from each other, can be observed by the optical system, so that it becomes easy to correct misalignment, etc. of the optical fibers.

Furthermore, in accordance with the present invention, since the contact plate is retracted away from the positioned optical fibers in the predetermined direction, damage to the cores due to their contact with the contact plate can be prevented during retraction of the contact plate away from the optical fibers.

Although the present invention has been fully described by way of example with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.

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Claims (8)

WHAT WE CLAIM IS

1. A method of positioning opposed end faces of optical fibers by butting the end faces of the optical fibers respectively against opposite faces of a contact plate disposed preliminarily between the optical fibers, wherein cores of the optical fibres are held out of contact with the contact plate.

2. A method as claimed in Claim 1, wherein a gap defined by the contact plate exists between the cores of the optical fibers when the optical fibers have been butted against the contact plate.

3. A method as claimed in Claim 1 or 2 wherein a mirror having a reflective surface forming an angle of 45* with a direction of observation of the optical fibers is provided on the contact plate such that two portions of the optical fibers, which are radially spaced 90" from each other, are observed in the direction by using an optical system after the optical fibers have been butted against the contact plate.

4. A method as claimed in Claim 1 or 2 wherein when the contact plate is retracted away from the optical fibers butted against the contact plate, the cores of the optical fibers are held out of contact with the contact plate.

5. A method as claimed in Claim 1, wherein a pair of recesses are, respectively, formed on the opposite faces of the 9 plate so as to confront the cores of the optical fibers.

6. A method as claimed in Claim 1, wherein when the end faces of the optical fibers have been butted against the contact plate, the contact plate is interposed between only portions of claddings of the optical fibers.

7. A method as claimed in Claim 1, wherein a through-hole is formed on the contact plate so as to be aligned with the cores of the optical fibers.

8. A method substantially as herein described with reference to the accompanying drawings, figures 2 to 6d. SUMITOMO ELECTRIC INDUSTRIES, LTD By their Attorneys Per HENRY 'ED