Method and apparatus for splicing optical fibres

Description of the invention

The invention relates to a method of connecting optical fibers, in particular to a method in which the ends of the fibers to be joined are trimmed with respect to the axis of the fibers at an angle other than right angle.

Optical fibers can be interconnected in many different ways. Welding of the fibers involves heating the two ends of the fibers to be joined to form a continuous transition medium. The mechanical joint consists in contacting the ends of the fibers on a suitable base or connector. Since the mechanical bonding of the fibers does not require the use of heat, it is preferred in the field. Mechanical joining devices must be carefully designed to ensure proper alignment of the fiber ends. Examples of such mechanical connection devices are included in US Patent Nos. 4,687,288 and US 5,394,496. A particular type of releasable mechanical connection of fibers is an optical fiber coupler. An example of such a linker is found in US Patent No. 4,705,352. The connector includes a retaining mechanism ensuring that during repeated interfaces of the fibers, the connector always has the same relative position to prevent damage to the end of the fiber. However, there is no suggestion in this specification as to the use of this mechanism for diagonal fiber trimming. This description suggests that the fibers may be joined together in any relative orientation.

In order to join the optical fibers, their ends are cut at right angles to the fiber axis. US Patent No. US 4,229,876 discloses an optical fiber trimming knife.

Optical fibers are traditionally cut at right angles to their longitudinal axis. However, it has been found that trimming the fibers at an angle other than a right angle significantly reduces the light loss per reflection. For example, PCT International Patent Application (Publication No. WO 98/54608) shows a tool for trimming fibers at an angle with respect to a straight line perpendicular to their axis. The angle at which the optical fibers are cut is deviated from the right angle by an amount of 1 ° to 20 °, preferably 5 ° to 10 °

European Patent EP 0419699 B1 and Japanese Patent JP 59038707 disclose an optical fiber connector, the sleeves of which and the fibers placed therein have obliquely polished faces that are not perpendicular to the longitudinal axis of the fibers. After the two coupler sleeves are joined together, the sleeve faces come into contact, while a gap is formed between the front faces of the optical fibers.

DE 3701421 A1 discloses a plug-in optical fiber connector, the sleeves and fibers of which have polished end surfaces inclined with respect to the longitudinal axis of the fibers. After the two fiber sleeves are joined together, the face surfaces of both the connector sleeves and the optical fibers are brought into contact with each other in a parallel orientation.

Although the slightly slanted end faces of the fiber ends eliminate light wastage, a problem arises when joining them. For proper contact of the oblique faces of the fibers, without any gap therebetween, the surfaces must be parallel to each other. This means that the optical fibers should have a specific orientation when they are inserted into the connector body. According to the known methods of combining fibers, the relative orientation of the combined fibers is arbitrary. Of course, it is possible to experimentally determine the correct orientation of the fibers by placing them in a coupler and measuring the reflection loss for different orientations. However, this way of orienting the fibers is costly and time-consuming, and can damage the end faces of the fibers. Alternatively, an optical gel (refractive index-matched gel) can be used, which can reduce the deleterious effect of improper orientation of the fiber faces. However, even the use of an optical gel loses the advantages of skewing the ends of the fibers to be joined.

The aim of the present invention is to provide such a method of connecting optical fibers, which will make it possible to take full advantage of the advantages resulting from the diagonal cutting of the ends of the fibers and will be practical and economical to use, thus eliminating the disadvantages of the previously known methods of mechanically connecting optical fibers.

The subject matter of the invention is a method of connecting optical fibers, which is characterized in that it comprises the steps of: attaching a first optical fiber to the first seating element, part of which extends beyond the first seating element; locating the first seat in the support member in a suitable radial orientation defined by a projection on the first seat and a cooperating slot in the support member; the first optical fiber attached to the first mounting member and projecting therefrom is cut at a defined sharp angle of inclination with respect to a straight line perpendicular to the axis of the optical fiber and the supporting member; the first seat is removed from the support member; locating the first seat in the body of the fiber-splicing device in a suitable radial orientation defined by a projection on the first seat and a cooperating slot in the body of the device; and the above steps are repeated for the second optical fiber and the second arrestor. The first and second oblique faces of the ends of the optical fibers abut each other in a mutually parallel orientation.

By skewing the fibers in a specific radial orientation and placing them in that orientation, a predictable orientation of the contacting fibers is achieved. As a result, a very good parallelism of the contacting faces of the fibers is achieved.

It should be noted that the radial orientation of the fibers at the time of trimming need not be the same as that at the time of their insertion into the body of the fiber-splicing apparatus. If a fiber trimming device and a support member with the same orientation are used, then the second seat should be rotated by 180 ° relative to the first seat when the fiber faces are brought into contact (assuming that identical seats are used). and the same support member when trimming the fibers).

According to the invention, the support member in which the fiber is placed for trimming is preferably attached to the fiber trimming device to prevent movement of the member in relation to the device. The support member is preferably integral with the fiber trimming device.

The angle of inclination at which the optical fibers are trimmed is preferably from 5 ° to 12 ° relative to a straight line perpendicular to the longitudinal axis of each optical fiber. (It should be noted that this angle is always measured with respect to a straight line perpendicular to the longitudinal axis of the fiber, where 0 ° means that the end face of the fiber is perpendicular to its longitudinal axis). In other preferred embodiments of the invention, the tilt angle is from 7 ° to 9 °, although other angles may be used.

In a preferred embodiment of the invention, attaching amine lumen fibers to the mounting element comprises heat shrinking the sleeve around the mounting element. The seating elements may consist of two parts which are pressed against each other by a thermally deformable sleeve. In this way, firm compression of the fibers is achieved, which can aid in obtaining axial stresses to facilitate the pressing of the fiber faces together.

In an alternative embodiment of the invention, securing the optical fiber to the holder comprises crimping the holder. Also in this case the seating elements can help to create the axial stresses of the fibers.

Preferably, abutting bevelled faces of the ends of the optical fibers are positioned in the alignment member. Such an alignment member, as is known per se, ensures the lateral alignment of the ends of the fibers. The equalizing member preferably consists of a first and a second element between which the amniotic lumen fibers are inserted, one of these elements having an approximately V-shaped groove which is covered when the two elements of the link are joined together. leveling.

An optical fiber connector is preferably arranged in the body of the fiber-splicing device.

The first seating element is placed in the body of the fiber-splicing device preferably during its manufacture.

Preferably, a body of the fiber-splicing device is used which has at least one latch for snapping the two seating elements together.

An optical gel is preferably used for the second end face of the fiber end.

The invention is shown in the drawing, in which fig. 1 shows the optical fiber splicing device according to the invention, in an axial longitudinal section, fig. 2 - the device according to fig. 1, cross-section, fig. 3 optical fibers connected by the method. according to the invention, in a side view, fig. 4 - the device for trimming fibers according to the invention, in axial longitudinal section, fig. 5 - a variant of the device

6 is a partial axial sectional perspective view of an optical fiber splicing device according to the invention, and FIG. 6 is another variant of the optical fiber splicing apparatus according to the invention in a partial axial sectional perspective view.

The exemplary device 1 for mechanically splicing optical fibers shown in Fig. 1 consists of a tubular body 2, an equalizing member 3 and two end fittings 4 and 5, in which optical fibers 20, 21 are placed, from the end portions of which the sheaths are removed. The ends of the fibers are positioned and aligned in the V-shaped groove 6 of the alignment member 3. The groove 6 has at the ends of the equalizer member 3 widened portions 6] which allow the fibers to bend in these areas in order to maintain the pressing force of the contact faces of the ends of the fibers.

According to the invention, the mechanical fiber splicing device 1 is provided with a mechanism for defining and maintaining the angular orientation of the optical fibers. This mechanism is equipped with edges or projections 7 on the seating elements 4, 5 and with cooperating slots 8 in the body 2. The combination of the projections 7 and the slots 8 ensures that the seating elements 4, 5 can only be inserted into the body 2 in one particular angular orientation (which is also seen in Fig. 2). It should be noted that the optical fibers 20, 21 are held firmly and still in the mounting elements 4, 5, for example by pressing the mounting elements against the fibers.

The seating elements according to Fig. 1, when placed in the body 2, are held by elastic latches which engage with the edges 10 of the mounting elements. Latches 9, which can be made of metal (e.g. metal wire) or plastic, are provided in the slots 11. The ends of the fibers are positioned in the seating members such that when they snap, the ends of the fibers touch each other and at least one of the fibers is slightly bent in the widened portion 61 of the groove 6. This ensures good contact of the ends of the ends of the optical fibers.

The second seating element 5 (FIG. 1) is rotated with respect to the first seating element 4 by an angle of 180 [deg.]. Such an arrangement allows the use of one design of the seating elements at both ends of the device 1, and (which is more important) ensures the correct orientation of the fiber faces, which is explained in more detail in connection with Fig. 3.

The seat 4 in Fig. 4 (also seen in Fig. 1) rests against the end 22 of the optical fiber 20 from which the sheath is removed. The fiber seat 4 is then placed in the support member 29. Due to the presence of the slot 8 and the projection 7, the seat 4 can only be positioned in one particular angular orientation. The end 22 of the optical fiber 20 is then trimmed at a specific angle to a straight line perpendicular to the longitudinal axis of the fiber by means of a clipping device 28, as is known per se, for example from the international PCT patent application (publication no. WO 98/54608). The front surface 24 of the fiber end 22, deviated from the perpendicular direction by an angle of inclination α, is schematically shown in Fig. 3, the size of this angle α is exaggerated for better illustration.

After the end 22 of the optical fiber 20 has been trimmed, the retainer is removed from the support member 29 and inserted into the body 2 of the splicing device. (Note that the body may contain one fiber pre-installed, but both fibers may also be field installed). The protrusion 7 and the slot 8 of the body 2 ensure that the seating 4 is inserted into the body 2 in a specific orientation, for example (as in the described example) exactly as when trimming the end of the fiber.

The above steps of the fiber joining method are repeated for the second seat 5 and the second optical fiber 21. As shown in Fig. 1, the second seat 5 is inserted into the body 2 in an angular orientation rotated relative to the first seat 4 by 180 °. This arrangement causes the faces 24 and 25 of the ends 22 and 23 of the optical fibers to be parallel to each other (Fig. 3). Subsequently, the snapping of the two seating elements brings the faces 24 and 25 of the ends 22 and 23 of the two optical fibers 20 and 21 into contact. The result of this method and device according to the invention is a very high quality optical fiber connector having very low light loss per reflection.

In the design of the device for mechanical fiber connection according to Fig. 5, between the seating elements and their holders 18 there are springs 19, which generate an oblique pressure ensuring very good contact of the faces of the optical fibers to be joined.

PL 204 576 B1

On the other hand, the device for mechanical fiber joining according to FIG. 6 is devoid of holders for the seating elements. Instead, the retainers are provided with a snap mechanism 17 similar to that used in ballpoint pens. Of course, other designs of fiber-splicing devices may be used, in which the advantages of the method of joining the fibers to the bevelled faces according to the invention can be obtained.