JPS6173110A - Ferrule of connector for optical fiber - Google Patents

Abstract

PURPOSE:To raise and hold the concentricity of an outer cylinder and the center of an optical fiber by applying a suitable circumscribing pressure between each hollow needle and an inscribing pressure to the needle by an elastic deflection of the needle, so that the outside diameter of the outer cylinder is not deformed. CONSTITUTION:A through-hole 12 having the inside diameter which is a little larger than the outside diameter containing a protective film of an optical fiber is provided along an axial core of a ferrule 11 from the end face of a containing part 11c of the ferrule 11, and the optical fiber is inserted and fixed together with the protective film. The other end of the through-hole 12 is continued to a fixed hole 13 of a larger diameter pieced in the same axial core along the axial core of the ferrule 11 from the end face of a fitting part 11a. Three pieces of needles 14 of the same length as a depth of the fixed hole 13 are pressed into the fixed hole 13 in a state that they are circumscribed to each other. When the optical fiber F is pressed into a gap among the three needles in a state they it has been pinched, a hollow needle 14b is bent by a clamping allowance portion and the optical fiber F can be pressed and fixed between two pieces of cylindrical needles 14a.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical fiber connector used for interconnecting optical fibers used in information transmission lines and the like. More specifically, there are various types of connectors used to removably connect optical fibers in a straight line, but this invention relates to an asynchronous sleeve-type connector, and in particular, the structure of the ferrule. Regarding.

The basic structure of the conventional sleeve type connector is shown in Figure 3 (a) and (b).
and FIG. 4, and in FIG. 3(a), 31 is a precisely finished metal ferrule, and 31a is a fitting part when a pair of ferrules are fitted facing each other. , 31b is a protrusion, 31C is a accommodating part for accommodating and fixing the optical fiber, 32 is a pore opened coaxially with the fitting part 31a, and having an inner diameter slightly larger than the outer diameter of the optical fiber, into which the optical fiber is inserted and fixed; 33 is a through hole for inserting and fixing the optical fiber together with the protective film covering the optical fiber. In FIG. 3(b), the part of the fitting part 34a of the ferrule 34 where the ferrules face each other is made of ceramic so that it has a small hole 35 in the center that is coaxial with the fitting part 34a. It is used by fixing the holding part 36,
The other parts are the same as those in FIG. 3(a). The optical fibers held by these ferrules as shown in FIGS. 3(a) and 3(b) are connected to each other while facing each other as shown in FIG. Here, 412.4ib is the through hole 3 of the optical fibers 42a and 42b including the protective film portion to be connected.
3 is a ferrule in which a portion of the optical fiber from which the protective film has been removed is inserted and fixed in the pore 32 or 35, respectively. The fitting portions of the respective ferrules 41a, 41b are pushed into the precisely finished inner diameter of the fitting sleeve 44 by fasteners 43a, 43b via springs 45a, 45b and fixed. This aligns the optical fibers so that they face each other, and the mating parts from both ends accurately hit the coaxial center to position the optical fibers, thereby reducing connection loss and connecting light. It is.

Problems to be Solved by the Invention Optical fibers consist of a core that conducts light and a cladding that covers it, but the core diameter is extremely small, less than 100 μm, so it is difficult to align the centers of the optical fibers and connect them. is the current situation. Particularly in the case of optical fiber connectors that are used in a removable manner, the machining accuracy of the connector directly affects the connection loss of the optical fiber. To overcome this problem, various types of optical fiber connectors have been proposed in the past, but there is a problem in positioning how to align the center of the optical fiber with the center of the outer diameter of the ferrule of the optical fiber connector. was there. In other words, the dimensional accuracy of the ferrule and sleeve is a major factor determining the performance of the optical fiber connector. In particular, ensuring the concentricity of the fitting portions 31a, 34a and the pores 32.35 and the roundness of the fitting portion itself are problematic. Further, a large amount of processing cost is required to process the pores and ensure concentricity between the pores and the fitting portion.

Means for Solving the Problems The present invention uses a ferrule consisting of three needles circumscribing each other and an outer cylinder having an inner diameter circumscribing the needles in place of the pores 32 and 35 shown in FIG. 3 (aHb). And the third t1
It is possible to position the optical fiber to the center of the outer cylinder using the gap formed by the ferrule.
Of these needles, two are cylindrical needles that do not deform, and the other one is a cylindrical needle that does not deform.
A hollow needle with elastic force is used, and the relationship between the hollow needle and the fitting part is set so that the spring constant in the diametrical direction of the hollow needle is lower than the spring constant in the diametrical direction of the outer cylinder, and the optical fiber is held between the hollow needle and the fitting part. When doing so, the optical fiber is pressed between the two cylindrical needles using the elastic deflection of the hollow needle inside the outer cylinder, thereby fixing the optical fiber at the center of the outer cylinder of the ferrule and not causing any deformation to the outer cylinder. The idea is to do so.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples shown in the drawings.

FIG. 1 is an explanatory diagram of the ferrule, and FIG. 2 is a diagram of the ferrule viewed from the side. In this figure, 11 is a precisely finished metal ferrule, lla is the fitting part when a pair of ferrules are fitted facing each other, llb is the protrusion, and IIG is the part covered with a protective film. This is a accommodating part that accommodates and fixes optical fibers. Accommodating portion 11C of this ferrule 11
A through hole 12 having an inner diameter slightly larger than the outer diameter including the protective film of the optical fiber is provided along the axis of the ferrule 11, into which the optical fiber is inserted and fixed together with the protective film covering it. Ru.

The other end of the through hole 12 continues from the end surface of the fitting portion 11a to a fixing hole 13 (having an inner diameter of a larger diameter (described later)) coaxially drilled along the axis of the ferrule 11. Three needles 14 having the same length as the depth of the fixing hole 13 are press-fitted into the fixing hole 13 in a state in which they are in circumscribed contact with each other. Here, two of the three needles 14 are cylindrical needles 142 having a cylindrical shape that does not deform, and these two cylindrical needles 143 are inserted into the fixing hole 13 made in the fitting part 11a so as to circumscribe the fixing hole 13. At this time, the axis of the ferrule 11 and the center of the optical fiber were set so that if the optical fiber F with the protective film removed was placed in the valley formed by the outer surfaces of the two cylindrical needles 14a circumscribed to each other, the axis of the ferrule 11 and the center of the optical fiber would match. The cylindrical needle 142 has a shape. The other needle is a pipe-shaped hollow needle 14b with a hollow hole inside, and its outer diameter is slightly larger than the outer diameter of the cylindrical needle I4a before deformation. By making the wall thickness thinner than the wall thickness of the outer cylinder 15 which is the outer peripheral part of the fitting part 11a provided with the fixing hole 13, the spring constant of the diametrical deflection of the hollow needle 14b of the donut-shaped cross section can be kept the same. The spring constant is set to be much lower than the spring constant of the diametrical deflection of the outer cylinder 15 having a donut-shaped cross section. Furthermore, before the three needles 14 are press-fitted into the outer cylinder 15, the inner diameter of the outer cylinder 15 (diameter of the fixing hole 13) is slightly smaller than the dimension of the circumscribed circle that circumscribes the three needles. When the needle 14 is press-fitted into the fixing hole 13, the hollow needle 14b has a slightly elliptical shape as shown by the dotted line in FIG. bend it. Therefore, a total of three 1
4 is press-fitted into the gap between the three needles with the optical fiber F sandwiched between them, the hollow needle 14b is deflected by the above-mentioned tightening margin, and the elastic deflection of the hollow needle 14b due to this tightening margin causes the optical fiber F to be It becomes possible to press and fix between the cylindrical needles 142. At this time, due to the spring constant relationship (the spring constant of the diametrical deflection of the hollow needle 14b is much lower than the spring constant of the diametrical deflection of the outer tube 15), the outer tube 1
5 is not distorted. Therefore, the outer cylinder 1 does not cause deformation.
The optical fiber F is positioned and fixed at the center of the outer cylinder 15 (the axis of the ferrule 11) by the cylindrical needle 142 which does not cause deformation as in 5.

FIG. 5 shows another embodiment in which the outer diameter and inner diameter of the outer cylinder 15 are eccentric. In this case, the eccentricity i1H of the inner and outer diameters (outer diameter and inner diameter of the outer cylinder 15) of the fitting part 11a of the ferrule 11 is measured, and the outer diameter of the outer cylinder 15 and the optical fiber F are determined based on the eccentricity amount and the diameter of the optical fiber F to be held. A conversion table for the cylindrical needles 142 is prepared in advance so that the cylindrical needles 142 and the cylindrical needles 142 are coaxial, and two cylindrical needles 14a to be used are attached to the fixing hole 13 from among the cylindrical needles 142 having the diameters set in advance according to the values in the conversion table. It is inserted inside and fixed with adhesive.
The optical fiber F has two cylindrical needles 14a.

The optical fiber F is placed in the outer curved valley of the hollow needle 14.
The positioning is performed by inserting and fixing the optical fiber F by sandwiching it between the points b.

Effects of the Invention As detailed above, in the present invention, the ferrule 11
Two cylindrical needles 14a and one hollow needle 14b are installed in the outer cylinder 15 of
A total of three needles 14 are press-fitted, and the resulting elastic deflection of the hollow needle 14b inserted into the outer cylinder 15 presses the optical fiber F into the gap between the outer peripheries of the two cylindrical needles 14a, thereby forming an optical fiber. F is fixed at the center of the outer cylinder 15. As a result, the elastic deflection of the hollow needle 14b prevents the three needles 1°4 (two cylindrical needles 142 and one hollow needle 14b) from moving within the fixing hole 13,
It is also possible to prevent the needle 14 from being pulled out from the fixing hole 13. Furthermore, due to the distortion of the fitting part 34a that occurs when the holding part 36 made of ceramic shown in FIG. There is no need to polish the outer diameter of the outer cylinder (fitting portion 34a) to the set dimensions again while maintaining concentricity with the pore 35 if the fitting fails. Further, according to the present invention, since it is relatively easy to precisely process the outer diameter of the needle 14 and the inner diameter of the outer tube 15 of the fitting portion, the outer tube 15 and the needle 14 are The degree of concentricity with the optical fiber F to be gripped is high (the fitting part 31a as in the conventional
, 34a, and the hole 32 has to be made almost the same diameter as the optical fiber, which is difficult to process.
Alternatively, there is no need to precisely process the pores 35. Moreover, the ferrule 11 of the present invention can hold the optical fiber F by elastic deflection between the outer tube 15 and the hollow needle 14b, even against thermal expansion caused by temperature changes caused by outside air in the area where the optical fiber connector is used. There is also the effect that it is possible to continue, which is impossible with the conventional ferrules 31 and 34.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a ferrule of an optical fiber connector according to an embodiment of the present invention, Fig. 2 is a view seen from the left lateral direction of Fig. 1, and Figs. 3 (a) and (b) are conventional ferrules for optical fiber connectors. FIG. 4 is a cross-sectional view showing the structure of the ferrule of the connector, FIG. 4 is a cross-sectional view showing the assembled state of the optical fiber connector, and FIG. 5 is an explanatory view of another embodiment. 11... Ferrule tta... Fitting part 13... Fixing hole 111... Needle 14a... Cylindrical needle 14
b...Hollow needle 15...Outer m 31...Ferrule 31a...Fitting part 32...Small hole 34...
- Ferrule 34a... Fitting part 35... Pore
44...Mating sleeve F...Optical fiber

Claims (1)

[Claims] (1) In the structure of the ferrule of an optical fiber connector, in which the structure consists of three mutually circumscribing needles that grip the optical fiber, and an outer cylinder having an inner diameter circumscribing the three needles, two of the three needles is a cylindrical needle that does not deform, and the other needle is a hollow pipe-shaped needle.
The spring constant in the diametrical direction of the hollow needle is lower than the spring constant in the diametrical direction of the outer cylinder, and when the three mutually circumscribed needles are press-fitted into the outer cylinder, there is The elastic deflection of the hollow needles provides appropriate external contact pressure between the needles and internal contact pressure between the needles and the outer cylinder, while preventing deformation from being applied to the outer diameter of the outer cylinder. A ferrule for an optical fiber connector, which is characterized by holding the optical fiber in a highly concentric manner with the center of the optical fiber being held.