Reinforcing members for connecting optical fibers and production thereof

Abstract: An optical fiber-connecting reinforcing member consists of a reinforcing base plate (3) made of a ceramic and a hot melt film (4). To simplify manufacture and protect the hot melt film against dirt and dust, the member is mounted on a resin sheet (1) having excellent heat resistance and peelability. The hot melt film is bonded to the resin sheet. In producing the optical fiber-connecting reinforcing member the resin sheet (1) is first placed on a lower holding plate with a guide, and a perforated plate is placed on the upper surface of the resin sheet. The perforated plate has longitudinal through holes bored therethrough at a specific interval. Hot melt films (4) and reinforcing ceramic base plates (3) are each preliminarily cut to a given size, and inserted into the longitudinal holes. An upper holding plate is placed on the perforated plate, and then hot pressing is effected.

Description: The present invention relates to optical fiber-connection reinforcing members to be used for connecting tip ends of optical fibers, and also to a process for producing such reinforcing members. As disclosed in Review of the Electrical Communication Laboratories, vol. 34, no. 6, pages 649-653, M. Matsumoto et al, "Practical Optical Fiber Splicing Techniques", optical fibers used for the purpose of optical communication, etc. are extremely thin quartz glass fibers having small diameters of around 100 µm. Thus, when tip ends of these optical fibers are to be connected together, a connecting portion needs to be reinforced by fixing the connecting portion to a reinforcing member which is formed by providing a hot melt layer on one side surface of a reinforcing ceramic base plate having the same coefficient of thermal expansion as that of the optical fibers. The above reinforcing member has conventionally been produced by hot pressing the reinforcing base plate onto a surface of a hot melt film and cutting the hot melt film in the same size as that of the reinforcing base plate with a cutter. Thus, there are problems in that the hot melt film attaches during the hot pressing to a lower holding plate for hot pressing and is not easy to peel off and that the hot melting film must be cut in a number of times which raises production cost. Furthermore, since such a conventional reinforcing member exposes an optical fiber-bonding surface of the hot melt film dirt and dust are likely to attach to the bonding surface during wiring. The present invention has been accomplished to solve the problems of the prior art and to provide optical fiber-connection reinforcing members which are free from contamination of a bonding surface for optical fibers and which can easily be handled at wiring sites as well as a process for producing such optical fiber-connecting reinforcing members at a low cost and high efficiency. According to a first aspect of the present invention, there is provided an optical fiber-connection reinforcing member package as specified in claim 1. According to a second aspect of the present invention, there is provided a process for producing optical fiber-connection reforcing members as specified in claim 7. The resin sheet may be any suitable flexible material, e.g. plastics material such as polyester. These and other optional features and advantages of the invention will be appreciated upon reading of the following description of the invention when taken in conjunction with the thus attached drawings with the understanding that some modifications, variations and changes of the same could be made by the skilled person in the art to which the invention pertains. For a better understanding of the invention, reference is made to the attached drawings, wherein: Fig. 1 is a perspective view of a first embodiment according to the present invention; Fig. 2 is a perspective view of a jig to be used for producing the first embodiment; Figs. 3 through 7 are sectional views illustrating production steps according to the present invention; and Fig. 8 is a partially cutaway front view of a hot press machine. Now, the present invention will be explained in more detail with reference to embodiments shown in the drawings. Fig. 1 illustrates a first embodiment of the present invention. Reference numerals 1 and 2 are a resin sheet having excellent heat resistance and peelability, such as a polyester film, and a plurality of laminates arranged on a surface of the resin sheet 1 at a specific interval, respectively. Each of the laminates 2 consists of a reinforcing base plate 3 made of a ceramic material having almost the same coefficient of thermal expansion as that of quartz glass (about 4×10⁻⁷/°C), such as crystallized glass, and a hot melt film 4 made of, for example, ethylenevinyl acetate or the like. The reinforcing base plate 3 and the hot melt film 4 are about 1 mm thick and about 0.5 mm thick, respectively. The ceramic material may be a ceramic substrate obtained by adding 0 to 3% by weight (hereinafter referred to briefly as "%") of TiO₂, 0.1 to 5% of ZrO₂, and 0 to 5% of P₂O₅ as a nuclei-forming agent to a base glass consisting essentially of 1.7 to 6% of Li₂O, 12 to 35% of Al₂O₃, and 55 to 75% of SiO₂, melting and shaping the mixture, and thermally treating the shaped plate to precipitate β-eucryptite crystals having the crystal grain diameter of not more than 0.1 µm. As shown in the drawings, the laminate is fixed onto the surface of the resin sheet 1 by bonding the hot melt film 4 onto the surface of the resin sheet 1. The thus constituted optical fiber-connecting reinforcing member according to the first aspect of the present invention is carried to a wiring site in the state shown in Fig. 1. When optical fibers are to be connected together, the laminate 2 is peeled off from the resin sheet 1. Then, the hot melt film 4 is butted to optical fibers, and heating is effected to reinforce the connecting portion of the optical fibers. As mentioned above, since the optical fiber-connecting reinforcing member according to the present invention is used by peeling the laminate from the resin sheet 1 immediately before use, the surface of the hot melt film can be prevented from being contaminated with dust unlike the prior art, so that the connecting portion of the optical fibers can assuredly be reinforced. Furthermore, since the optical fiber-connecting reinforcing member according to the present invention can be rolled, it is convenient in storage and transportation. In addition, an optical fiber-connection reinforcing member package may include only one reinforcing member bonded to a resin sheet. Next, the process for producing the above-mentioned optical fiber-connecting reinforcing member will be explained. As shown in Fig. 3, a resin sheet 1 is placed on the upper surface of a lower holding plate 6 on which guide members 5 project from three sides of the upper surface as shown in Fig. 2. Then, as shown in Fig. 4, a perforated plate 8 having longitudinal through holes 7 bored at a given interval is set on the upper surface of the resin sheet 1. The outer dimension of the perforated plate 8 matches with the inner dimension defined by the guide members 5, and the thickness of the former is almost equal to that of the latter. Each of the longitudinal holes 7 has the same size as that of the laminate 2, and slight escapes for the hot melt resin (not shown) are preferably formed at opposite ends of the through hole. Next, as shown in Fig. 5, hot melt films 4 preliminarily cut in a given size are inserted into the longitudinal holes 7 one by one. Then, as shown in Fig. 6, ceramic reinforcing base plates 3 cut in the same size as that of the hot melt films are inserted thereon. Then, as shown in Fig. 7, a planar upper holding plate 9 is placed on the upper surface of the perforated plate 8. The whole assembly is set in a hot press machine 12 provided with an upper heater 10 and a lower heater 11 as shown in Fig. 8, and then preliminarily heated in 30 seconds, and finally heated at a temperature of 120°C for 2 minutes and 30 seconds. Thereby, the hot melt films 4 are fused onto the reinforcing base plate 3 to form a laminate 2, and also simultaneously lightly bonded to the resin sheet 1 having excellent peelability and heat resistance. Thus, the optical-connecting fiber reinforcing member according to the first aspect of the present invention as shown in Fig. 1 is obtained. According to the producing process of the second aspect of the present invention, since the upper surface of the lower holding plate 6 is covered with the resin sheet 1 having excellent peelability, the product can easily be peeled from the lower holding plate after the hot pressing. Moreover, since the preliminarily cut hot melt film 4 is inserted into the longitudinal hole 7 of the perforated plate 8 and fused onto the reinforcing base plate 3, it is no need to cut the hot melt film to meet the size of the reinforcing base plate 3 after the hot melt film is bonded to the reinforcing base plate 3. Thus, the number of production steps is advantageously reduced. However, as a matter of course, the reinforcing member in which the resin sheet is cut to meet the size of the reinforcing base plate 3 may separately be used, if necessary. Furthermore, according to the producing process of the present invention, since the reinforcing base plate 3 and the hot melt film 4 are preliminarily cut in a given size and fused together, bubbles are unlikely to be involved in a joining interface thereof, and reliability can be enhanced. As is evident from the aforegoing explanation, the optical fiber-connecting reinforcing member according to the first aspect of the present invention can be prevented from being contaminated at an optical fiber-contacting surface and can easily be handled at a wiring site. Further, according to the producing process of the second aspect of the present invention, the optical fiber-connecting reinforcing members can be obtained at a low cost and high efficiency. Therefore, the present invention offers the optical fiber-connecting reinforcing members and the producing process thereof which solve the conventional problems, and greatly contributes to developments in the industry.

Claims: An optical fiber-connection reinforcing member package, including at least one reinforcing member comprising an elongate reinforcing base plate (3) made of a ceramic material and a hot-melting film layer (4) bonded to a major surface of the base plate (3), characterised in that the film layer (4) is bonded to a support consisting of a resin sheet (1), the bond between the film layer (4) and the resin sheet (1) being such that the reinforcing member is peelable from the resin sheet (1). The optical fiber-connection reinforcing member package according to claim 1, wherein the resin sheet (1) is a polyester film. The optical fiber-connection reinforcing member package according to claim 1 or 2, wherein the ceramic material has the same or almost the same coefficient of thermal expansion as that of quartz glass. The optical fiber-connection reinforcing member package according to any one of claims 1 to 3, wherein the thickness of the reinforcing base plate (3) is about 1 mm. The optical fiber-connection reinforcing member package according to any one of claims 1 to 4, wherein the hot-melting film layer (4) is ethylenevinyl acetate. The optical fiber-connection reinforcing member package according to any one of claims 1 to 5, wherein the thickness of the hot-melting film layer (4) is about 0.5 mm. A process for producing optical fiber-connection reinforcing members on a support according to claim 1, characterised by comprising the steps of: placing a support consisting of a resin sheet (1) on a lower holding plate (6) having guide members (5) projecting from three sides of its upper surface; placing a perforated plate (8) onto the upper surface of the resin sheet (1), the perforated plate (8) having elongate holes (7) bored therethrough; inserting into each elongate hole (7) firstly a hot-melting film layer (4) and secondly a base plate (3) made of a ceramic material, the film layer (4) and the base plate (3) having previously been cut to the size of the elongate hole (7); placing an upper holding plate (9) on the perforated plate (8); and then effecting hot pressing; the bond thus formed between the resin sheet (1) and the hot-melting film (4) being such that the reinforcing member is peelable from the resin sheet (1).

Inventors: KARIYA MIKIO, OHTA TAKASHI, KARIYA, MIKIO, OHTA, TAKASHI
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1988
Main classification: G02B6
IPC codes: G02B6