FR2638537A1 - Method of manufacturing an expander for expanding the optical beam of monomode fibres, and expander obtained by this method - Google Patents

Abstract

The present invention relates to a method of manufacturing an expander 20 for expanding the optical beam of monomode fibres, including a section 23 of monomode optical fibre of a diameter between 0.5 and 3 mm, a section 26 of monomode optical fibre of a diameter between 0.1 and 0.14 mm and a connecting cone 24 between the two sections, characterised in that it consists in making a section 23 of optical fibre of a diameter between 0.5 and 3 mm, in forming a cone 24 by drawing this section 23, in cutting the tapered portion of the cone 24 and, finally, in connecting, in the region of the cut, a section 26 of fibre of a diameter between 0.1 and 0.14 mm. It also relates to an expander obtained by this method.

Description

Method of manufacturing an expander for expanding the optical beam of single-mode fibers, and expander obtained by this method.

 The present invention relates to a method of manufacturing a widener for expanding the optical bundle of single-mode fibers, comprising a section of single-mode optical fiber with a diameter between 0.5 and 3 mm, a section of single-mode optical fiber of a diameter between 0.1 and 0.14 mm and a connection cone between the two sections.

 It also relates to an expander obtained by this process.

 Expanders of this type are used to connect a single mode optical fiber with a small diameter, between 0.1 and 0.74 mm, with an optical element of small dimensions or with another single mode optical fiber of the same diameter.

 In the case of the connection of a single-mode optical fiber with a conventional optical element, the expansion of the optical beam of the fiber by a widener proves to be very advantageous because this widener has low losses and it is less sensitive than the fiber at the lateral and axial distance. In addition, it is not very sensitive to dust and it does not require an index adapter liquid.

 In the case of the connection between a single-mode optical fiber and another same fiber, the expansion of the optical beam of each fiber by a widener makes it possible to use a removable connector with low losses, inexpensive, reliable and easy to maintain.

 In either case, these expanders improve the coupling of single-mode optical fibers.

 According to a known method, an enlarger is obtained by stretching an optical preform up to a diameter close to 0.1 mmr and a connection cone is formed between the two diameters. However, the final dimensions of this expander are not easy to control, in particular the length of the cone and the respective diameters of the two sections of fibers.

 We are therefore not sure to obtain an "adiabatic" optical transition regime.

 The object of the present invention is therefore to perfectly control the dimensions of the expander.

 This object is achieved by the method of the invention which is to focus only on the dimensions of the cone without worrying about its tapered part because it will be removed, and an optical fiber of a perfectly constant diameter will be reported at the end of the cone.

 The method according to the invention is characterized in that it consists in making a section of large optical fiber with a diameter between 0.5 and 3 mm, in forming a cone by stretching this section, in cutting the tapered part of the cone and finally. to connect, at the cutoff, a section of small fiber with a diameter between 0.1 and 0.14 mm.

 The method according to the invention is described below, by way of example and with reference to the accompanying drawings.

 Figures 1 to 4 each show a step in the process.

 FIG. 1 represents the first step which consists in developing sections of large fibers, on a fiberizing machine.

 FIG. 2 represents the second step which consists in developing, on each section of coarse fiber, a cone, on a drawing machine.

 Figure 3 shows the third step which consists in cutting the tapered part of the cone, and Figure 4 represents the fourth step which consists in welding, at the cut end of the cone, an optical fiber, the third and the fourth steps being carried out on the same conventional welding cutter.

 In FIG. 1, the fiberizing machine comprises a support 1 mounted on a motorized plate 2, a fiberizing oven 3, a measuring element 4 determining the diameter of the fiber, a capstan 5 which avoids the curvature of the fibers, and a knife 6.

 From a preform 21, a fiber 22 with a diameter of between 0.5 and 3 mm is formed, depending on the desired magnification ratio, and this fiber 22 is cut into sections 23. These sections 23 are then stored and then taken up on a drawing machine.

 In FIG. 2, the drawing machine comprises a support 7 mounted on a motorized plate 8, a heating element 11 mounted on a motorized plate 9, and finally a support 12 also mounted on a motorized plate 10. The heating element can be an electric arc, a small torch or a high frequency induction graphite oven.

 A section 23 of large fiber is therefore stretched to form a cone 24 and a tapered part 25. The place where the diameter has reached the desired value, between 0.1 and 0.14 mm, is identified by spraying ink.

 In FIG. 3, a welding cutter device comprises two supports 13 and 14, and a knife 15. The section 23 of large fiber is taken up on this device, then cut at the place previously identified.

 In FIG. 4, the knife 15 is retracted and replaced by two nozzles 16 allowing the welding of a small fiber section 26. This small fiber section 26 has a perfectly controlled diameter since it was obtained directly on a fiberizing.

 The final widener 20 therefore consists of a section 23 of large fiber, a cone 24 and a section of small fiber 26.

It can be covered by a heat shrink tubing. The end of the coarse fiber section can either be cut and used as it is, or repolished, and used in an optical isolator.

 The end of the small fiber section can be connected to a line fiber.

Claims (3)

1 / Method for manufacturing a widener (20) for expanding the optical beam of single-mode fibers, comprising a section (23) of single-mode optical fiber with a diameter between 0.5 and 3 mm, a section (26) of single-mode optical fiber with a diameter between 0.1 and 0.14 mm, and a connection cone (24) between the two sections, characterized in that it consists in developing a section 23 (23) of optical fiber d '' a diameter between 0.5 and 3 mm, to form a cone (24) by stretching this section (23), to cut the tapered part (25) of the cone (24), and finally to be connected at the cut , a section (26) of fiber with a diameter between 0.1 and 0.14 mm. 2 / Expander (20) for expansion of the optical beam of single-mode fibers, obtained by the method according to claim 1, characterized in that it comprises a section (23) of large fiber, a cone (24) and a section (26 ) of small fiber, connected by welding to the small end of the cone (24). 3 / Expander according to claim 2, characterized in that it is covered by a heat-shrinkable sheath.