Optical fiber connector

Abstract: 1. Disclosed is an optical fiber connector for connecting an optical fiber cable (C) including a cable core (E), an inner coating layer (P) formed on the cable core, and an outer coating layer (S) formed on the inner cable layer. The optical connector includes a ferrule (F) to which the cable core (E) is inserted, a first cable fixing member (H,Q,J) for fixing the inner coating layer (P), a second cable fixing member (D,T) for fixing the outer coating layer (S), a connector cover (AA) having an opening (B1), and a fastening ring (A1) provided at an outer circumference of the opening (B1), and formed together with the connector cover (AA) as a single body. The fastening ring (A1) is fastened after the first (H,Q,J) and second (D,T) cable fixing members are fitted into the opening (B1).

Description: TECHNICAL FIELD The present invention relates to an optical fiber connector for connecting optical fiber cables, and more particularly, to an optical fiber connector for connecting optical fiber cables each composed of a cable core comprised of a core and a cladding, an inner coating layer, and an outer coating layer. BACKGROUND ART Figure 1 is a view showing a mode in which an optical fiber cable C is inserted into an optical fiber connector in the prior art, Figs. 2 and 3 are cross-sectional views showing how the optical fiber connector is assembled, and Fig. 4 is a cross-sectional view of the optical fiber cable when assembled. As shown in the figures, the optical fiber cable C consists of a cable core E comprised of a core and a cladding, both made of silica based glass, an inner coating layer P coated on the cable core E, and an outer coating layer S coated on the inner coating layer P. When the cable core E is a single mode optical fiber, the diameter of the core, having a refractive index higher than that of the cladding, is 10 µ m, and the diameter of the cladding is 125 µ m. The inner coating layer P is formed of a polyaramid fiber such as Kevlar (trademark of Du Pont Corporation), and the outer coating layer S is formed of PVC. As shown in Figs. 1 and 4, the cable core E of the optical fiber cable C is inserted into a ferrule F, a spring G is fitted over the cable core E and the ferrule F, a support H is fitted over the spring G, and a projection L of the support H is fitted into a fitting groove M of a plug hole K, to fix the support H thereat. Next, the inner coating layer P next to the cable core E is peeled back and then pulled forward and over a knurled portion N of the support H, a cylinder Q of a pinch member D is fitted over the portion of the inner coating layer P fitted over the knurled portion N and fastened thereat to sandwich the inner coating layer P between the pinch member D and the support H. Then, as shown in Fig. 2, the outer coating layer S of the optical fiber cable C is fitted over a pinch portion R of the pinch member D, and as shown in Fig. 3, a cylinder T is fitted over the outer coating layer S and fastened from the outside as shown by arrows to sandwich the outer coating layer S between the cylinder T and the pinch member D, to thereby pinch-fasten the optical fiber cable C to the pinch member D. As shown in Fig. 4, the pinch member D is inserted into an opening B of a connector cover A, made of an elastic material such as a rubber, and then a cap X is fitted over the connector cover A, to thus complete the connection of the optical fiber cable C to the optical fiber connector. A stop edge W, having an inner diameter d 2 which is smaller than an outer diameter d 1 of the pinch member D, is provided at an insertion opening V of the opening B and projects inward to prevent a unintentional withdrawal of the pinch member D after it is inserted into the opening B of the connector cover A. This prior art optical fiber connector, however, suffers from the following disadvantages. The provision of the stop edge W projected inward of the opening B requires the application of a strong pressure, to forcibly press the pinch member D into the opening B. The cover A, however, is formed of an elastic material such as a rubber, and accordingly, this forcible insertion of the pinch member D into the opening B is difficult and may damage the inner wall of the opening B. Namely, the prior art connection of the optical fiber cable to the optical fiber connector suffers from a low work efficiency, and requires a high level of skill. Accordingly, an automatic connection of the optical fiber cable to the optical fiber connector is practically impossible. WO-A-86/00423 shows the features of the first part of present claim 1. DISCLOSURE OF THE INVENTION An object of the present invention is to provide an optical fiber connector in which a pinch member is easily inserted into an opening of a connector cover and is not easily withdrawn therefrom, to thus improve the efficiency of assembly. Another object of the present invention is to provide an optical fiber connector enabling an automatic connection of an optical fiber cable thereto. According to the present invention, there is provided an optical fiber connector according to claim 1. The fastening ring is made of a plastically deformable material such as metal or thermoplastics. The fastening ring may be mounted on an inner wall of the opening. The fastening ring may also be mounted on an outer wall of the connector cover at the opening. The fastening ring may be embedded in the connector cover at the opening. In all cases, the fastening ring is integrated with the connector cover. BRIEF DESCRIPTION OF THE DRAWINGS Optional objects and features of the present invention will be described in detail with reference to the accompanying drawings, in which Figs. 1 to 4 are sectional views showing a connection and assembling of an optical fiber connection of a prior art; and Figs. 5 to 7 are sectional views showing a connection and assembling of an optical fiber connector of an embodiment in accordance with the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figures 5 is a sectional view of an optical fiber connector of an embodiment in accordance with the present invention, and Figs. 6 and 7 are sectional views showing the assembling of the optical fiber connector. In Figs. 5 to 7, elements having reference numerals identical to those in Figs. 1 to 4 indicate corresponding elements in Figs. 1 to 4. A cover AA corresponding to the cover A of the prior art, is provided with a fastening ring Al, which is made of a force deformation material such as metal or thermoplastics, has a cylindrical shape, and is integrated with the cover AA, made of an elastic material, at an inner circumference of the opening B of the cover AA, by an insertion molding process. The inner diameter d 3 of the fastening ring A1 is slightly larger than the diameter d 1 of the pinch member D to facilitate the insertion of the pinch member D into the fastening ring Al. After inserting the pinch member D to the fastening ring Al, as shown in Fig. 7, the fastening ring A1 is fastened at a portion of the cylinder Q of the pinch member D to thereby fix the pinch member D in the opening B of the connector cover AA, and as a result, the pinch member D can not be unintentionally withdrawn from the opening B. The connector cover AA has the opening B1 in which the first cable fixing means including the support H, the cylinder portion Q and the frame J, is fitted when the connector is assembled, a first hole B2 in which the second cable fixing means including the pinch member D and the cylinder T is fitted, and a second hole B3 which passes over the optical fiber cable C. Note that the stop edge W inserted into the opening, as shown in Figs. 1 to 4, is omitted from the optical fiber connector in the present invention. The fastening ring A1 formed of a force deformation material such as metal or thermoplastics can be provided on an outer wall, or the inner wall (as shown in Fig. 5), of the connector cover AA formed of an elastic material by molding, in each case so as to be formed as an integrated part of the connector cover AA, or can be embedded in the connector cover AA, so as to be formed as an integral part of the connector cover AA. The omission of the stop edge W eliminates any bending of the cover A made of an elastic material when the pinch member D is inserted into the opening B thereof, and thus facilitates the insertion of the pinch member D. The fastening ring A1 is easily fastened, provides a firm pinching of the pinch member D, and prevents an unintentional withdrawal of the optical fiber cable C from the optical fiber connector. The connecting and assembling operation of the present invention does not require any cumbersome or complex procedures, and accordingly, the connecting and assembling operation can be automated. The above description is devoted to the connection of the single-mode optical fiber of a silica based glass as an example, but the present invention is not limited to the connection of such optical fiber, and can be applied to other optical fibers such as a multi-mode optical fiber.

Claims: An optical fiber connector for connection of an optical fiber cable (C) including a cable core (E), an inner coating layer (P) formed on the cable core, and an outer coating layer (S) formed on the inner cable layer, comprising: a ferrule (F) into which said cable core (E) is inserted; a first cable fixing means (N,Q), including an outer sleeve portion (Q), for fixing said inner coating layer (P); a second cable fixing means (R,T) for fixing said outer coating layer (S); and a connector cover (AA) having a through passage comprising, in order along the passage, an opening (B1) in which said first cable fixing means (N,Q) can be fitted, a first hole (B2) in which said second fixing means (R,T) can be fitted, and a second hole (B3) for passing over said optical fiber cable (C); characterised in that the body of said connector cover (AA) is of elastic material, and in that the connector cover (AA) further comprises a fastening ring (A1) of plastically deformable material integrally formed with the body of said connector cover (AA), provided around said opening (B1), the opening (B1) having a diameter larger than the outer diameter of said sleeve portion (Q) and said second cable fixing means (R,T) and being fastenable by an inwardly directed force deformation applied from outside said connector cover (AA) to provide firm pinching of the sleeve portion (Q), after said second cable fixing means (R,T) and said first cable fixing means (N,Q) have been fitted respectively into said first hole (B2) and said opening (B1), thereby to prevent the first cable fixing means (N,Q) from being withdrawn from the opening (B1). An optical fiber connector according to claim 1, wherein said fastening ring (A1) is made of metal or thermoplastics. An optical fiber connector according to claim 2, wherein said fastening ring (A1) forms the inner wall of the connector cover (AA) at said opening (B1). An optical fiber connector according to claim 2, wherein said fastening ring (A1) forms the outer wall of said connector over (AA) at said opening (B1). An optical fiber connector according to claim 2, wherein said fastening ring (A1) is embedded in the body of said connector over (AA) at said opening (B1).

Inventors: HIGUCHI KAZUHIRO, YUGUCHI REN-ICHI, HIGUCHI, KAZUHIRO, YUGUCHI, REN-ICHI
Applicants: FURUKAWA ELECTRIC CO LTD, THE FURUKAWA ELECTRIC CO., LTD.
Application year: 1991
Main classification: G02B6
IPC codes: G02B6