JPS58173707A - Optical fiber fixing structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an original fiber fixing structure, and particularly to an optical fiber fixing structure for a terminal used in a repeater using an optical fiber as a transmission path.

In repeaters in transmission systems using original fibers, particularly in optical submarine repeaters installed on the ocean floor, terminals for pulling out optical fibers must have high water pressure resistance and high airtightness.

FIG. 1 is a sectional view showing the main structure of an optical submarine repeater. A repeater unit 1 for amplifying optical signals is protected from high water pressure by a water pressure cylinder 2 and cover 3 covering its outer periphery. The optical signal is transmitted through the optical fiber 7. A watertight terminal 4 is attached to a terminal mounting portion 31 of the cover 3, and the watertight terminal 4 is connected to an optical cable 6. The optical fiber 7 passes through an optical fiber fixing structure 5 installed in the watertight terminal 4 and is led out into the optical cable 6.

FIG. 2 is a perspective view showing a conventional optical fiber fixing structure. The sleeve 51 is a cylindrical metal sleeve having a bottom. The fiber guide 52 is connected to the sleeve 51
A groove 25 for accommodating the sheath removal section 8 of the optical fiber 7 and a recess 26 for sealing the sheath removal section 8 are provided on its outer periphery. .

A hole for passing the optical fiber 7 is provided at the bottom of the sleeve 51, and a recess 15 for sealing the portion 8 to be waxed removed is provided at the opening of the sleeve 51. The surface of the sheath removal section 8 of the optical fiber 7 is metal-coated, and after the sheath removal section 8 is accommodated in the groove 25 of the fiber guide 52 and inserted into the sleeve 51, the sleeve 51 and the fiber are removed. By melting and solidifying a low melting point metal, such as solder, in the recesses 15 and 26 of the guide 52, the sealing section! The coating removal part 8 is sealed in u'''''3. The fiber fixing part 54 is connected to the sealing part 53
At the base of the optical fiber 7 coming out from the sleeve 51
It is fixed to the fiber ψ guide 52 and molded with resin to prevent external force from acting on the root of the optical fiber 7 and causing it to deform. The one formed in this way is
Watertight terminal 4 as optical fiber fixing structure 5 in FIG.
installed within.

This conventional optical fiber fixing structure has the disadvantage that the transmission loss of the optical fiber changes due to temperature changes, and furthermore, after the optical fiber is soldered and sealed, the resin used to mold the fiber fixing part at its root takes a long time to harden. (Usually for 24 hours or more) There is a drawback in that during this time, extreme care must be taken in handling so that no external force is applied to the optical fiber. That is, when there is a temperature change, the metal of the sleeve 51 and the fiber kite 52 and the resin of the fiber fixing part 54 have different thermal expansion coefficients, so the sealing part 5
The coating removed portion 8 extending from the optical fiber 3 receives shear stress near its root, causing a bend with a small radius of curvature (so-called micro-bending), and the transmission loss of the optical fiber 7 increases accordingly.

- In the experimental example, almost 0 decibel (
dB) due to a temperature change of 35C.
or more. It is not uncommon for temperature changes of this magnitude to occur during the installation or transportation of repeaters, and in configuring the system, it is not possible to allow an increase in transmission loss of 1 dB for each terminal of the repeater.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber fixing structure that eliminates the above-mentioned drawbacks and causes almost no change in optical fiber transmission loss due to temperature changes.

The structure of the present invention includes a metal rod having at least one groove formed on the outer periphery along the length direction, and a recessed portion deeper than the groove provided on the outer periphery at at least one end of the groove, and the metal rod. a metal support protruding from the end surface of the side where the recess is provided, and a metal sleeve that fits on the outer periphery of the metal rod and has a recess on the inner periphery of the metal rod at a location facing the recess. The coating removed portions of at least one optical fiber from which the coating has been removed at predetermined locations are accommodated in the grooves of the metal rod, respectively, and the recesses are formed in each of the gold oval rod and the metal sleeve. A low melting point metal is filled in the space to seal the optical fiber including the coating removal portion, and the sealed optical fiber is fixed and held on the support portion.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a perspective view showing an embodiment of the present invention.

In the structure shown in FIG. 2, a column 55 and a support stand 56 are added to the fiber fist guide 52 shown in FIG. 2, and the fiber 7 is fixed to the support stand 56 and covered with a skin. The sleeve 51 and the fiber guide 52 have the same structure as shown in FIG. Formed. The part of the optical fiber 7 from which the coating is not removed is soldered to the sealing part 53 together with the coating removal part 8 , and the optical fiber 7 coming out from the sealing part 53 is placed on the outer periphery of the support base 56 . [Fixed with adhesive 58, sealing part 53 and support base 5]
It is held straight for 60 minutes. Since the part of the optical fiber 70 from which the coating has not been removed is sealed with solder, even if a local force is applied to the root of the optical fiber 7 coming out from the sealing part 53, that part is covered with the coating and reinforced. The support base 56 is made of metal that is integrated with the fiber guide 52 and has the same coefficient of thermal expansion.
Since it is fixed to the support stand 56 at a location away from 3,
This eliminates the need for shear stress to act on the root of the optical fiber 7 and cause micro-bending as in the conventional case.

Therefore, in the structure shown in FIG. 3, the transmission loss of the optical fiber hardly changes due to temperature change. Furthermore, since there is no part of the optical fiber 7 coming out of the sealing part 8 after being soldered and sealed, there is no need to take care in handling the optical fiber so that no external force is applied to it, which was conventionally required.

In addition, 3rd. The structure in the figure shows two sides of the structure, and is not limited thereto. Although the figure shows a case in which two optical fibers 7 are sealed and fixed, it is clear that the application can be applied to the case where there is only one optical fiber 7 or three or more optical fibers 7, and the same effect can be obtained. . Further, the same effect can be obtained by appropriately changing the shape of the support column 55 and the support base 56 or the means for fixing the optical fiber 7 to the support base 56. By providing it at both ends of the structure, water pressure resistance and airtightness can be improved.

As is clear from the above description, the present invention has the effect of realizing an optical fiber fixing structure in which the transmission loss of the optical fiber hardly changes due to temperature changes.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an optical submarine repeater, FIG. 2 is a perspective view showing a conventional optical fiber fixing structure, and FIG. 3 is a perspective view showing an embodiment of the present invention. 1... Repeater unit, 2... Pressure resistant cylinder, 3... Cover, 4... Watertight terminal, 5... Optical fiber fixing Structure, 6...
・Optical cable, 7... Optical fiber, 8...
...Removable part, 51...Sleeve, 52°°
...Fiber e-guide, 53...Sealing part,
54...Fiber fixing part, 55...Strut, 56...Support stand, 57...Groove. ￥7 l Closed Ilz Diagram Page 1 continued 0 Inventor Osamu Harada Inside NEC Corporation, 5-33-1 Shiba, Minato-ku, Tokyo Applicant NEC Corporation 5-33 Shiba, Minato-ku, Tokyo No. 1 Procedural Amendment (Spontaneous) 58.7.-5 Director General of the Japan Patent Office, Month, Day, Showa 1, Indication of the case Showa S7 Patent Application No. 5617
No. 8 No. 2, Title of the invention Optical 7 Aipa fixing structure 3, Relationship with the case of the person making the amendment Applicant: 33-1, Shibago I-fl, Minato-ku, Tokyo; Person (contact address: NEC Corporation Patent Department) & Subject of amendment: “Detailed explanation of the invention” column of the specification (b) Drawings & Contents of amendment: “Detailed explanation of the invention” column (i) Section rg the description “Figure 1” on page 6, line j111.
I corrected it to ``Z diagram''. (2) The entry "8" on page 7, line 13 will be corrected to "53". (B) Replace Figure 1 of the nine drawings attached to the drawing application with the attached drawing.

Claims (1)

[Scope of Claims] A metal rod provided on the outer periphery along the length direction of at least one groove, and having a recess on the outer periphery that is deeper than the groove at at least one end of the groove; a metal sleeve having a recess on the inner periphery protruding from the end face of the rod on the side where the recess is provided; The groove of the rod is filled with a low melting point metal in the space formed by the recess of each of the metal rod and the metal sleeve to seal the optical fiber including the portion where the coating is removed, and further seal the optical fiber. An optical fiber fixing structure, characterized in that an optical fiber is fixed and held on the support part.