OPTICAL FIBER RIBBON END-STRUCTURE

Abstract: The invention provides an end structure comprising at least one optical fiber ribbons wherein the ends of the optical fiber ribbons (1) are bundled together and tightly fitted in a metallic sleeve member so that coating layers (4) of the optical fiber ribbons contact the inner surface (5) of the metallic sleeve member (2).

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to an improved end structure of a single or bundle of optical fiber ribbons for use in light transmission in optical communications, using a display unit or sensing means. Description of the Prior Art In the document US-A-4 022 647, a tape-like optical fiber element formed into a coherent fiber bundle is disclosed. This bundle consists of a wrapped sheet provided with a veneer of optic fibers. The bundle is a spiral bundle formed by wrapping said sheet about an axis parallel to an axis, commencing at one edge of the sheet. Furthermore, a similar optical fiber element is disclosed in document JP-A-52 26839, which also consists of a spirally wrapped sheet. This sheet has a plane back cloth with a plastic foil being attached to said back cloth in a wave form whereby, several cavities in which optical fibers can be placed are formed between the back cloth and the plastic foil. In the prior art, an end of bundle of optical fibers, is fixed in a connector terminal with adhesive or, instead of adhesive, by tight pressing thereby permiting frequent attachment and detachment of the terminal to light emitting or receiving element to be easily accomplished. Conventional optical fiber ribbons consist of small diameter optical fibers arranged in the form of tape and having a coating layer holding them together. Until now no satisfactory connector terminal for the end of an optical fibre ribbon has been proposed. In particular there was no connector that permits semipermanent fastening of the optical fiber end to a light emitting or receiving element that did not have high manufacturing costs. Furthermore the adhesive used could cause optical deterioration with time. SUMMARY OF THE INVENTION The above problems or defects have been overcome by the inventor. The present invention is defined in claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1a and 1b are perspective views of end structures of optical fiber ribbon bundle embodying the invention; Figs. 2a and 2b are cross-sectional views of the end structures of Figs. 1a and 1b, drawn to enlarged scale; and Fig. 3 is a stepwise diagram illustrating the outline of process for forming an end structure of optical fiber ribbon bundle according to the invention. DETAILED DESCRIPTION OF THE INVENTION The invention will be described more fully by way of examples with reference to the accompanying drawings hereinafter: Figs. 1a and 1b give perspective views of end structures of optical fiber ribbon bundles according to the invention and Figs. 2a and 2b are cross-sectional views of them, drawn to enlarged scale, in which reference characters designate 1 an optical fiber ribbon, 3 optical fibers as of plastic, 2 a metallic sleeve fitted over the end of a bundle of optical fiber ribbons 3, and 4 a coating layer of synthetic resin, on the inner surface of the sleeve 2. In the following, the process for forming an optical fiber ribbon terminal embodying the invention will be described referring the stepwise the process shown in Fig. 3. A plurality of optical fiber ribbons 1 are bundled together, with the coating layer at top, as shown in Fig 3a. The end of the optical fiber ribbon bundle is transversely bent or folded with the coating layer of each ribbon on the outside, as shown in Fig. 3b, and thereafter inserted into a metallic sleeve 2 with coating layers 4 adjacent the inner surface 5 of the sleeve 2, as shown in Fig. 3c. To aid insertion, the sleeve 2 may have a tapered opening 6 into which the end of optical fiber ribbon bundle is inserted. Then the sleeve 2 is pressed in a press 7, as shown in Fig. 3d, so that the totallized section of the optical fiber ribbon(s) after pressing is the same as or somewhat smaller than the resulting inside section of the sleeve. thus The end of optical fiber ribbon bundle thereby has a tight fit in the sleeve. The sleeve may be pressed into any intended shape. Subsequently passing an end part of the optical fiber ribbon bundle extending through the pressed sleeve is cut off with a cold or heated cutter 8, as shown in Fig. 3e. This process can be accomplished without doing damage optical fibers because there are coating layers 4 are positioned between the inner surface 5 of the sleeve 2 and optical fibers 3, and thus their optical characteristic can be maintained.

Claims: An optical fiber terminal comprising at least one optical fiber ribbon (1) tightly fitted in a metallic sleeve member (2) with the constituent fibers (3) extending therethrough each ribbon (1) comprising a single synthetic resin coating layer (4) supporting a row of fibers (3), wherein the end(s) of said optical fiber ribbon(s) (1) is (are) folded, curved or wrapped together and configured so that said coating layer(s) (4) of said optical fiber ribbon(s) (1) is(are) mostly on the outside of the bundled ribbon(s) (1) thereby forming a layer protecting the fibers (3) from damage and effectively coming between the bulk of the fibers (3) and the inner surface (5) of said tightly fitting metallic sleeve member (2).

Inventors: FUJIGAKI, TAKASHI, FUJINAGA, YOSHIKAZU, FURUKAWA, NORIYUKI, ICHIMURA, KIYOSHI, IUCHI, SHIGERU, SHIBUYA, YUKIO, TOKUDA, SHUICHIRO
Applicants: MITSUBISHI RAYON CO., LTD.
Application year: 1988
Main classification: G02B6
IPC codes: G02B6