APPARATUS AND METHOD FOR ALIGNING POLARIZATION-MAINTAINING OPTICAL FIBERS

Abstract

In a method for aligning a polarization-maintaining optical fiber, in which the optical fiber (7a, 7b, 7c) is held in clamping fashion by means of a clamping device (12, 19, 23), a given rotational position of the optical fiber (7a, 7b, 7c) about the fiber longitudinal axis is detected, and the optical fiber (7a, 7b, 7c) is rotated about the fiber longitudinal axis by means of the clamping device (12, 19, 23), it is proposed that at least one clamping element (13, 14, 20-22, 24-27) of the clamping device (12, 19, 23), said clamping element abutting against the optical fiber (7a, 7b, 7c), is moved relative to at least one further clamping element (13, 14, 20-22, 24-27) of the clamping device (12, 13, 17), said at least one further clamping element likewise abutting against the optical fiber (7a, 7b, 7c), for the purposes of rotating the optical fiber (7a, 7b, 7c). Moreover, a correspondingly configured apparatus is presented.

Claims

1-20. (canceled)

21. A method for aligning a polarization-maintaining optical fiber, in which a) an optical fiber is held in a clamping fashion by means of a clamping device, b) a given rotational position of the optical fiber around a fiber longitudinal axis is detected, and c) the optical fiber is rotated around the fiber longitudinal axis by means of the clamping device, characterized in that d) for the rotation of the optical fiber, at least one clamping element of the clamping device abutting against the optical fiber is moved relative to at least one further clamping element of the clamping device also abutting against the optical fiber.

22. The method according to claim 21, characterized in that the relative movement is a pure translational movement.

23. The method according to claim 21, characterized in that the relative movement is a pure rotational movement or a mixed translational and rotational movement and at least one of the clamping elements abutting against the optical fiber is a roller element rotatably mounted in the clamping device.

24. The method according to claim 21, characterized in that light is irradiated into the optical fiber in order to detect the given rotational position of the optical fiber in relation to the fiber longitudinal axis.

25. The method according to claim 24, characterized in that at an open end of the optical fiber, a light pattern is detected which is dependent on the rotational position of the optical fiber and is generated by the irradiated light.

26. The method according to claim 24, characterized in that the light is irradiated within the clamping device and/or through at least a partial region of the clamping device into the optical fiber.

27. The method according to claim 21, characterized in that, during the rotation, a cable sheath surrounding the optical fiber and allowing rotation of the optical fiber therein is held by a sheath fixing device arranged at a distance from the clamping device.

28. The method according to claim 21, characterized in that a distal end of the optical fiber is fixed with the desired rotational position in a fixing element.

29. The method according to claim 28, characterized in that the distal end of the optical fiber is freed from a fiber cladding layer.

30. The method according to claim 21, characterized in that the rotation of the optical fiber is controlled by means of the detected rotational position of the optical fiber.

31. An apparatus for the automated alignment of a polarization-maintaining optical fiber, comprising: a) a clamping device for gripping the optical fiber in a clamping fashion, and b) means for rotating the optical fiber clamped in the clamping device about its fiber longitudinal axis, characterized in that c) the clamping device has at least two clamping elements, wherein the at least two clamping elements are provided to abut against the optical fiber for clamping and for performing the rotation of the optical fiber, the at least two clamping elements or at least two of the clamping elements are movable relative to one another.

32. The apparatus according to claim 31, characterized in that the clamping device is configured, for performing the rotation of the optical fiber, to perform a pure translational movement relative between the at least two clamping elements or between at least two of the clamping elements involved.

33. The apparatus according to claim 31, characterized in that the clamping device is configured, for performing the rotation of the optical fiber, to perform a pure rotational movement or a mixed rotational and translational movement relative between the at least two clamping elements or between at least two of the clamping elements, wherein at least one of the clamping elements involved is a roller element rotatably mounted in the clamping device.

34. The apparatus according to claim 31, characterized by a detection device for detecting the given rotational position of the optical fiber around the fiber longitudinal axis, and by irradiation means for irradiating light into the optical fiber, wherein the detection device is configured to detect the rotational position of the optical fiber based on the irradiated light.

35. The apparatus according to claim 34, characterized in that the irradiation means are configured to irradiate the light through at least a partial region of the clamping device into the optical fiber.

36. The apparatus according to claim 35, characterized in that the light is irradiated through at least one of the clamping elements into the optical fiber, wherein preferably the refractive indices of the concerned clamping elements and the material of the optical fiber abutting against the concerned clamping element are identical or at least similar to one another.

37. The apparatus according to claim 34, characterized in that at least one light source of the irradiation means is arranged or fixed in or on the clamping device.

38. The apparatus according to claim 31, characterized by a holding device spaced apart from the clamping device for holding the optical fiber.

39. The apparatus according to claim 38, characterized in that the holding device is a sheath fixing device for holding a cable sheath surrounding the optical fiber, wherein the cable sheath allows rotation of the optical fiber around its fiber longitudinal axis relative to the cable sheath.

40. The apparatus according to claim 31, characterized by means for fixing a distal end of the optical fiber in a fixing element not belonging to the apparatus.

Description

[0032] Shown schematically are

[0033] FIG. 1a: an optical waveguide having a PANDA fiber,

[0034] FIG. 1b: an optical waveguide having a fiber with elliptical sheath,

[0035] FIG. 1c: an optical waveguide having a bow-tie fiber,

[0036] FIG. 2: a connector unit having a plurality of fibers fixed therein,

[0037] FIG. 3: an apparatus for performing the method according to the invention,

[0038] FIG. 4: a clamping device with purely translational relative movements between clamping elements,

[0039] FIG. 5: a clamping device with translational and rotational relative movements between clamping elements and

[0040] FIG. 6: a clamping device with purely rotational relative movements between clamping elements.

[0041] FIG. 1a shows schematically, in cross section, a first optical waveguide 1a having an optical fiber 7a having a structure of the so-called PANDA fiber type. The optical fiber 7a has a fiber matrix 2a surrounded by a fiber cladding 5a and an inner fiber core 3a embedded in the fiber matrix 2a, the inner fiber core being provided for forwarding polarized radiation in single mode. In addition to the fiber core 3a, two stress rods 4a generating mechanical stress are arranged in the fiber matrix 2a. The mechanical stress is material to the polarization-maintaining property of the optical fiber 7a. The optical fiber 7a is rotatably arranged in a cable sheath 6a. The representation is to be understood purely in principle and not to scale.

[0042] FIG. 1b shows, corresponding to the representation of FIG. 1a, a second optical waveguide 1b having a second optical fiber 7b having a structure of the so-called oval inner clad fiber type. The structure of the second optical waveguide 1b essentially corresponds to that of the first optical waveguide 1a according to FIG. 1a, wherein, however, no stress rods are contained in the fiber matrix 2b surrounded by the fiber cladding 5b but rather an oval inner sleeve 4b generating the desired mechanical stress surrounds the fiber core 3b. Here, a cable sheath 6b also surrounds the second optical fiber 7b.

[0043] FIG. 1c shows, corresponding to the illustration of FIG. 1a, a third optical waveguide 1c having a third optical fiber 7c having a structure of the so-called bow-tie fiber type. The structure of the third optical waveguide 1c essentially corresponds to that of the first optical waveguide 1a according to FIG. 1a, wherein however, no round stress rods are contained in the fiber matrix 2c surrounded by the fiber cladding 5c but rather stress rods 4c having the cross section of an isosceles trapezoid. A cable sheath 6c also surrounds the third optical fiber 7c here.

[0044] The aforementioned types of optical waveguides 1a, 1b and 1c are known from the prior art.

[0045] In the following, embodiments of the method according to the invention and the apparatus according to the invention are illustrated on the basis of the optical waveguide 1a having the optical fiber 7a of the PANDA fiber type. However, the embodiments apply correspondingly to other polarization-maintaining optical waveguide types, in particular also to optical waveguide types which correspond to the second optical waveguide 1b or the third optical waveguide 1c.

[0046] It is also known from the prior art, as shown in FIG. 2, to arrange a plurality of optical fibers 7a, possibly freed from the fiber cladding 5a, in a connector unit 8, wherein the optical fibers 7a have to be fixed in a defined rotational position with respect to their longitudinal axis in order to be able to pass on the polarized light in the desired orientation for further use. The optical fibers 7a can be fixed in V-shaped grooves 9 of the connector unit 8 using an adhesive (not illustrated here) and additionally or alternatively with a cover element 10. As an alternative to fixing the optical fibers 7a freed from the fiber cladding 5a in the grooves 9, for example, with direct contact between the fiber matrix wall and the groove wall, it is possible to fix the optical fibers 7a in the connector unit 8 with the fiber cladding 5a, for example, in the grooves 9, and to provide the fixation at a distance from the distal fiber end, which can then again be freed from the fiber cladding 5a.

[0047] The method according to the invention and the apparatus according to the invention can be used to be able to achieve the positioning of the optical fibers 7a in the desired rotational position as automatically as possible, an embodiment of which is represented schematically in FIG. 3.

[0048] The cable sheath 6a placed around the optical fiber 7a is fixed with a sheath fixing device 11 and thus the position of the optical fiber 7a is also largely predetermined in directions orthogonal to the fiber longitudinal axis. The optical fiber 7a of the optical waveguide 1a is held in a clamping fashion by a clamping device 12 on the fiber cladding 5a at a distal end at which the optical waveguide 1a is freed from the cable sheath 6a. The clamping device 12 is illustrated in another basic view in FIG. 4 and consists of an essentially flat first clamping element 13 and an essentially flat second clamping element 14, which are arranged on a manipulation unit 15. In order to rotate the optical fibers 7a in a defined manner about their longitudinal axis, the second clamping element 14 is moved relative to the first clamping element 13 in a translational movement, for example, downwards or upwards in FIG. 3 or 4. Since the optical fiber 7a abuts firmly against both clamping elements 13 and 14, the translational movement causes it to rotate about its longitudinal axis. Since, without further measures, the optical fiber 7a rolls away simultaneously on both clamping elements 13 and 14 with the rotational movement, the optical fiber 7a will also perform a translational movement upwards or downwards in FIGS. 3 and 4. Said translational movement of the optical fiber 7b can be compensated for by a corresponding translational movement of the entire clamping device 12.

[0049] The rotational position of the optical fiber 7a is determined using a detection device 16, which is only indicated schematically in FIG. 3. Provision can also be made for the other spatial position of the optical fiber 7a to be determined simultaneously using the detection device 16. A signal generated by the detection device 16 and dependent on the rotational position and/or other spatial position of the optical fiber 7a can be used to control the clamping device 12, for example, by using electronic data processing. If the desired rotational position of the optical fiber 7a is given, the optical fiber 7a freed from the fiber cladding 5a, that is, with the fiber matrix 2a, is inserted into one of the grooves 9 (see FIG. 2) of the connector unit 8, for example, by means of moving the clamping device 12 or by a separate movement of the connector unit 8. If a locally applied adhesive is used to fix the optical fiber 7a to the connector unit 8, it can be cured by means of a UV lamp 17.

[0050] In order to be able to better recognize the rotational position of the optical fiber 7a, light can be irradiated into the optical fiber 7a, which is passed on in particular by the stress rods 4a (see FIG. 1). The light can be irradiated laterally through the fiber cladding 5a by means of a light source 18.

[0051] FIG. 5 shows a second clamping device variant 19 having a first clamping element 20, a second clamping element 21 and a third clamping element 22, wherein the second and the third clamping element 21 and 22 are rotatably mounted in the clamping device variant 19 in a manner not illustrated here and, for example, have the shape of a cylindrical roller. If the first clamping element 20 is now moved translationally, up or down in FIG. 5, relative to the two other clamping elements 21 and 22, the optical fiber 7a clamped between the first clamping element 20 on the one hand and the second clamping element 21 and third clamping element 22 on the other hand executes a corresponding rotational movement due to the given frictional forces. Due to the rotatably mounted second and third clamping elements 21 and 22, the rotating optical fiber 7a does not execute any translational movement as long as the axes of rotation of the second and third clamping elements 21 and 22 remain fixed in space.

[0052] FIG. 6 finally shows a third clamping device variant 23 in which the optical fiber 7a is clamped between four clamping elements 24, 25, 26 and 27 rotatably mounted on the third clamping device variant 23 in a manner not illustrated here. One of the clamping elements, for example, clamping element 24, is actively driven and thus ensures a rotation of the optical fiber 7a, while the further clamping elements 25, 26 and 27 rotate with it and enable a low-wear rotation of the optical fiber 7a.

[0053] Instead of the passive, rotatably mounted clamping elements or in addition thereto, sliding surfaces are also conceivable in the clamping device variants 19 and 23, which enable the fiber 7a to rotate.

TABLE-US-00001 List of reference symbols  1a Optical waveguide  2a Fiber matrix  3a Fiber core  4a Stress rod  5a Fiber cladding  6a Cable sheath  7a Optical fiber  1b Second optical waveguide  2b Fiber matrix  3b Fiber core  4b Inner sleeve  5b Fiber cladding  6b Cable sheath  7b Second optical fiber  1c Third optical waveguide  2c Fiber matrix  3c Fiber core  4c Stress rod  5c Fiber cladding  6c Cable sheath  7c Third optical fiber  8 Connector unit  9 Groove 10 Cover 11 Sheath fixing device 12 Clamping device 13 First clamping element 14 Second clamping element 15 Manipulation unit 16 Detection device 17 UV lamp 18 Light source 19 Second clamping device variant 20 First clamping element 21 Second clamping element 22 Third clamping element 23 Third clamping device variant 24 Clamping element, actively driven 25 Clamping element 26 Clamping element 27 Clamping element