JPH01216304A - Optical connector - Google Patents

Abstract

PURPOSE:To align with high accuracy angles in the main axis direction of both optical fibers to be connected by fitting closely a key groove provided on a ferrule to a key of a plug housing. CONSTITUTION:One piece of key groove 11 in one piece or plural pieces of key grooves 11, 12 provided on a ferrule is fitted closely to a key of a plug housing 4 which is engaged to its key groove 11. In this regard, it is desirable that chamfering is performed to one end face or both end faces of the key groove 11. Accordingly, the degree of freedom of a rotation to the plug housing 4 of the ferrule 1 becomes small. In such a way, even when both the ferrules 1 which are butted have rotated to the maximum in the directions opposite to each other, it is prevented that the angles of their main shafts are shifted greatly.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention is used in connection between optical fibers or between optical fibers and optical elements, especially when it is necessary to align the angles around the axis of the optical fibers. This article relates to optical connectors.

"Prior Art" There are various types of optical connectors used to easily connect and disconnect optical fibers.
For example, JIS C597 is the mainstream.
Like the Pot-type single-core optical fiber connector specified in 0.0, the optical fiber is fixed at the center of a cylindrical rod (ferrule), and this is inserted into a hollow cylinder (alignment sleeve) with a precise inner diameter. There is a method in which the end faces of the ferrules are brought into contact with each other.

This technique can also be used to connect an optical fiber to an optical element such as a laser diode, but in either case, the optical fiber is fixed at the center of the ferrule.

In the case of the above method, the tip of the ferrule is machined to a precise outer diameter and serves as a fitting part that is inserted into the alignment sleeve, and the proximal end holds this ferrule in the plug housing. The structure has a flange portion for the purpose of Usually, as shown in FIG. 6, when positioning keys b, b are provided in the plug housing a,
Keyways d and d are provided in the flange portion of the ferrule C, and the rotation of the ferrule C relative to the plug housing a is restrained by engaging these keys b and b with the keyways d and d. , the ferrule C is kept in a floating state with respect to the plug housing a so that even if there is a slight positional deviation between the two plug housings a that are butted against each other, the positional deviation will not directly affect the ferrule C. Therefore, a gap of about 0.2 mm in width is secured between the key b and the keyway d. Therefore, in the conventional optical connector, as shown in FIG. 7, there is room for an angular deviation around the axis of about 5 degrees at most within the above-mentioned gap between the butted ferrules C.

By the way, some optical fibers include polarization-maintaining optical fibers that can preserve the polarization state of propagating light.

A polarization-maintaining optical fiber has a property of maintaining the polarization state when linearly polarized light is input in the direction of its principal axis. As a parameter for evaluating the performance of such polarization-maintaining optical fibers, the extinction ratio, which is the ratio of the optical power on the output side in the direction of the main axis and the component in the direction perpendicular to it, is used when a linearly polarized wave is input in the direction of the main axis. , for short polarization-maintaining optical fibers on the order of lOm, the extinction ratio is -40 to -50 dB.
things have been realized.

When connecting such polarization-maintaining optical fibers to each other, or to an optical element such as a laser diode that emits linearly polarized light, the direction of the main axis of the optical fiber, that is, the direction around the axis of the optical fiber It is necessary to match the angles of , and the required accuracy for this angular deviation in the rotation direction is 0.0.
Within 5 degrees, if -30 dB is required, within 2 degrees is required.

"Problem to be Solved by the Invention" As mentioned above, when connecting polarization-maintaining optical fibers to each other or to connectors to polarization-maintaining optical fibers and optical devices, it is necessary to align the main axes of the optical fibers with high precision. However, when the above-mentioned conventional optical connector is used to connect polarization-maintaining optical fibers to each other or to connect polarization-maintaining optical fibers to optical devices, the optical connector has an angular misalignment of up to 5° as described above. Since this may occur, the extinction ratio would be significantly degraded.

For example, if they are connected with their principal axes deviating from each other by 5°, the extinction ratio will deteriorate to about -21 dB, and therefore, it has been impossible to realize a sufficient extinction ratio.

The present invention has been made in view of the above circumstances, and its purpose is to accurately control the orientation of the principal axes of both polarization-maintaining optical fibers or when connecting polarization-maintaining optical fibers and an optical element. It is an object of the present invention to provide an optical connector that can match the above-mentioned values, and therefore does not significantly deteriorate the extinction ratio.

"Means for Solving the Problem" In order to achieve the above object, the present invention provides two methods to be combined.
a pair of ferrules to which the ends of two optical fibers are respectively fixed; a pair of plug housings in which the ferrules are housed in a floating manner; an alignment sleeve in which the pair of ferrules are fitted and butted together so as to be connected; and a spring that applies a pressing force in the axial direction to each of the ferrules; Or, in an optical connector having a structure in which angular positioning around the ferrule axis is achieved by a plurality of key grooves engaging with keys provided in the plug housing, one or more keys provided in the ferrule. The present invention is characterized in that one keyway of the grooves is tightly fitted into a key of the plug housing that engages with the keyway.

It is desirable that one or both end surfaces of the keyway be chamfered.

"Function" In the optical connector of the present invention, the key groove provided in the ferrule and the key provided in the plug housing are tightly fitted, so the degree of freedom of rotation of the ferrule with respect to the plug housing is reduced. This prevents the angles of their main axes from shifting significantly even when both ferrules that are butted against each other are rotated to the maximum in opposite directions.

"Embodiment" Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 5.

FIG. 1 is a cross-sectional view showing the overall schematic configuration of the optical connector of this embodiment, in which reference numeral 1.1 indicates a pair of ferrules;
2.2 is an optical fiber whose end is fixed to the ferrules 1.1; 3 is an alignment sleeve that fits into the tip ends of both ferrules 1.1 and abuts their tip surfaces; 4; .4 is a plug housing that houses the ferrule 1.1; 5.5 is a spring that applies a pressing force to the ferrule 1.1 housed in the plug housing 4.4;
6゜6 is an adapter that connects the plug housings 4.4, 7.7 is a coupling nut that connects and fixes the adapters 6.6, and 8.8 is a rubber hood provided at the rear end of the plug housing 4.4. It is.

As shown in detail in FIGS. 2(A) and 2(B), the above ferrule 1 is a fitting part whose tip is machined to a precise outer diameter and inserted into the alignment sleeve 3. , and a flange portion IO for holding the ferrule l within the plug housing 4 is formed on the base end side. Two keyways 11 and 12 are formed in the flange portion IO as shown in FIG. 2(B), but the upper keyway in the figure! The width dimension of l is slightly narrower than the width dimension of the lower keyway 12.

When the above-mentioned ferrule 1 is housed in the plug housing 4, as shown in FIG. A gap is formed so that the floating state of the ferrule l with respect to the plug housing 4 is ensured. Further, at this time, the above-mentioned key grooves 11 and 12 formed in the flange portion IO are adapted to engage with keys 13 and 14 provided respectively in a state of protruding into the plug housing 4, The engagement of the keyway 11 with the key 13 and the keyway 12 with the key 14 substantially restricts the relative rotation of the ferrule 1 with respect to the plug housing 4. And the upper keyway l
! By making the width dimension of the keyway l! slightly narrower, this keyway l! There is almost no gap between this and the key summer 3 that engages with it, and they are tightly fitted together. It is desirable that the gap between the keyway 11 and the key 13 be as small as possible as long as their relative movement in the axial direction is possible, and at most 0.05
It is preferable to set it to about m5+.

On the other hand, a gap of, for example, about 0.2+u+ is secured between the lower keyway 12 and the key 14 that engages with it, and within this gap, the keyway 12 and the key 14 have no relative displacement in the circumferential direction. It is possible.

Based on the above configuration, in this optical connector, the floating state of the ferrule l with respect to the plug housing 4 is ensured as in the case of conventional optical connectors, and the main axes of both optical fibers 2.2 to be connected are It is also possible to precisely match the angle.

This will be explained with reference to FIG.

FIG. 4 is a diagram showing a state in which the ferrule l is eccentrically eccentric to the maximum extent with respect to the plug housing 4. As is clear from this diagram, a gap is provided between the keyway 12 and the key 14. There is room for the ferrule 1 to be eccentric with respect to the plug housing 4, and this ensures that the ferrule 1 remains floating even if both plug housings 4.4 are slightly misaligned. This prevents misalignment from directly affecting the ferrule 1.1.

However, since the keyway 11 and the key 13 are tightly fitted together, the degree of freedom of rotation of the ferrule 1 is reduced compared to the case of conventional optical connectors, and when the ferrule 1 is eccentric to the maximum extent. The center position does not shift significantly even in the case of . Therefore, even if both ferrules 1.1 are butted against each other with eccentricity in opposite directions, their centers will be maintained at approximately the same position, and therefore the angular deviation between them will be sufficiently small, and as a result, the light The extinction ratio can be greatly improved when polarization-maintaining optical fibers or polarization-maintaining optical fibers and optical elements are connected using a connector.

For example, a keyway violet that fits closely together! When the gap between the key 13 and the key 13 is 0.05+am, and the outer diameter of the flange portion IO of the ferrule l is 4.6 mm, the angular deviation between the ferrules 1.1 that are butted together is at most arctan (0.05 /2.3)#l
, 3.

In this case, the extinction ratio is 101og(tan"(1,3°)) The maximum angular deviation between the main axis of the fiber and the main axis of the optical element is arctan (0,025/2.3) = 0.62
°, so the extinction ratio at this time is 101og(jan"(0,62@))Lr-39dB
In either case, the maximum angular error is 5° and the extinction ratio is -21 dB, which are greatly improved when using a conventional optical connector.

It should be noted that the smaller the gap between the keyway 2 and the key 13 that are fitted together, the more effective it is in terms of reducing angular deviation. However, if the gap is extremely small, the keyway 11 and Attachment of the ferrule l to the plug housing 4 with the axial movement with respect to the key 13 being obstructed;
Since removal becomes difficult and machining thereof becomes extremely difficult, it is desirable that the size of the gap be approximately 0.05 mm as described above.

Also, the gap between the keyway 11 and the key 13 is set to 0°05m.
5 or less can be achieved relatively easily by reducing the dimensional tolerance between the two, but it is possible to reduce the ferrule 1 and the plug housing 4 without making the dimensional tolerance too strict.
It is also possible to select and use them mutually.

One embodiment of the present invention has been described above, and since there is almost no gap between the key groove 11 and the key 13, which are tightly fitted together, the key 13 can be locked when the ferrule 1 is housed in the plug housing 4. If there is a possibility that it will be difficult to enter the groove 11, it is desirable to chamfer one or both end surfaces of the keyway 11. FIG. 5 shows a state in which a chamfered portion 15 is provided on one end face of the keyway II.

In addition, in the above embodiment, +i is an example in which two sets of keys and key grooves are provided, but even if more sets of keys and key grooves are provided, one set of keys and key grooves may be provided. Exactly the same effect can be obtained by making the grooves fit closely together and by providing a gap of a predetermined size between the key of the other set and the key groove to ensure a floating state. Of course. Alternatively, only one set of keys and keyways may be provided that fit closely together.

"Effects of the Invention" As explained in detail above, the optical connector of the present invention has one keyway out of one or more keyways provided in the ferrule, and a plug housing that engages with the keyway. Since the ferrule is tightly fitted to the key, it is possible to ensure the floating state of the ferrule with respect to the plug housing, and it is also possible to match the angles of the main axes of both optical fibers to be connected with high precision. Therefore, it is suitable for use when connecting polarization-maintaining optical fibers or between polarization-maintaining optical fibers and an optical element.

Additionally, by chamfering one or both end surfaces of the keyway that is tightly fitted to the key, the ferrule can be fitted easily when the ferrule is housed in the plug housing. play.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the optical connector of the present invention;
Figure 2 shows the shape of the ferrule in the optical connector of this embodiment, of which (a) is a half-sectional view, and (b) is a half-sectional view.
is a rear view, FIG. 3 is a cross-sectional view showing the state in which the key groove of the ferrule and the key of the plug housing are engaged in the optical connector of this embodiment, and FIG. FIG. 5 is a cross-sectional view showing a state when the optical connector is eccentric, and FIG. 5 is a perspective view showing a state in which the key groove of the ferrule of the optical connector of this embodiment is chamfered. Figure 6 is a cross-sectional view showing the state in which the ferrule, keyway, and key of the plug housing are engaged in a conventional optical connector, and Figure 7 is a cross-sectional view showing a conventional optical connector in which the ferrule is angularly misaligned within the plug housing. It is a sectional view showing a state. Ri: Ferrule, 2: Optical fiber, 3: Alignment sleeve, 4: Plug housing, 5: Spring, lO・...Flange part, 11...Keyway, 13...
Key, 15... Chamfered part. Applicant: Nippon Telegraph and Telephone Corporation Figure 2 (A)
(b) 1- Ferrule 10---Flashing 11-m-Key groove 11---Key thin 1-m-Ferrule 1o---7 Ramp part II-m-Key groove +5---FFO Loop part Figure 6

Claims (2)

[Claims] (1) A pair of ferrules to which the ends of two optical fibers to be coupled are respectively fixed; a pair of plug housings each housing the ferrules in a floating state; an alignment sleeve into which the pair of ferrules are fitted and abutted so that they are mutually aligned and connected in the axial direction; and a spring that applies a pressing force in the axial direction to each of the ferrules, the flange of each of the ferrules An optical connector having a structure in which angular positioning around the ferrule axis is achieved by engaging one or more keyways provided in the plug housing with keys provided in the plug housing, An optical connector characterized in that one of the one or more keyways is tightly fitted into a key of a plug housing that engages with the keyway. (2) The optical connector according to claim 1, wherein one or both end surfaces of the keyway are chamfered.