CONNECTING DEVICE FOR CONNECTION OF THE END PORTIONS OF OPTICAL FIBRES

Abstract: Connecting device for axial connection of the end portions of at least one optical fibre (14) with another, which are fixed in at least one plug (13) each provided in a coupling house (10), in order to provide an optical connection between the fibres via a lens (12) connectable to each fibre end. Each lens (12) is constituted by a lens body (20), the front end surface (21) of which is partially spherical and the opposite, rear end surface (22) of which is arranged perpendicular against the longitudinal axis of the lens body (24). In the coupling house (11) a ring shaped, partially spherical or conical seat (19) is provided for the front end surface of the lens body, which seat is concentric with the longitudinal axis of the coupling house. The plug (13) is insertable in a coaxial guide sleeve (15) guided in the coupling house (11). The front end of the plug, which is perpendicular to its longitudinal axis, can be pressed to bearing against the rear end surface (22) of the lens body (20) so that the partial spherical end surface of the lens body front, is pressed to bearing against the seat achieving a centering of the lens (12), the plug (13) and the coupling house (11) relatively each other.

Description: CONNECTING DEVICE FOR CONNECTION OF THE END PORTIONS OF OPTICAL FIBRES. The present invention refers to a connecting device for axial connection of the end portions of at least one optical fibre with another, which are fixed in at least one plug each provided in a coupling house, in order to provide an optical connection between the fibres via a lens connectable to each fibre end. Background of the invention The rapid development of the field of communication has entailed that the need for faster and more reliable trans- mission media has increased drastically. Optical fibres have revolutionized transmission possibilities. These fibres allow a large number of signals to be transferred in one and the same fibre and with speeds near that of light. Since the fibre length is limited at manufacture, these have to be connected by means of different connecting devices. Connecting devices have to connect optical fibres with each other, so that the fibre ends are located exactly axially right in front of each other. A problem at connection of optical fibres end-ways with each other is their small diameter, that amounts to some or some tenths of milli¬ metres, while its optical core can have a diameter of 10-50 μm. A deviation of a thousandth part of a millimetre there¬ fore constitutes a coarse deviation, whereby the trans- mission losses increase drastically. Therefore there are very great demands on the tolerances of the connecting device, which entails complicated designs and high manufac¬ turing costs. Through the Swedish patent application 8903366-6, is known a connecting device for optical fibres, which device requi¬ res specially formed means to center optical fibres relati- lens body is pressed to bearing against the seat achieving a centering of the lens body, the plug and the coupling house relatively each other. Description of the drawings The invention will be described below with reference, to an embodiment shown in the accompanying drawings: Fig. 1 shows a section through a part of a connecting device according to the invention. Fig. 2 shows a section analogous with fig. 1 of a modified connecting device. Fig. 3 shows in reduced scale the connection device shown in fig. 1 in complete form. Fig. 4 shows a section through a centering means contained in the connecting device. Fig. 5 shows a bottom view of the centering means according to fig. 4. Description of the embodiments The insertion device 10 shown in fig. 1 consists of a coup¬ ling house 11, that comprises primarily a lens 12 for trans¬ mission of light signals and a plug 13, that is designed as a holder for one or more optical fibres 14, surrounded by an outer protection 28. The plug 13 is guided in the coupling house 11 by means of a conical guide sleeve 15, provided in a recess 17 designed with corresponding draught, which is coaxial with the longitudinal axis 24 of the coupling house. The conical recess 17 passes into a cylindric channel 18, which has somewhat larger diameter than the lens 12. The channel 18 at the end opposite the guide sleeve 15 is formed with a ring shaped partial spherical or conical seat 19, which is concentric with the longitudinal axis 24 of the coupling house 11. The plug 13 is of conventional type and can exist in different sizes, why even the guide sleeve 15 is manufactured in different sizes. At the front end of the coupling house 11, ie. the end that is intended to be con¬ nected axially with a second connecting device, is formed with a guide dowel 34, the peripheral guide surface 37 of which is coaxial with the longitudinal axis 24 of the coup- ling house 11. A coupling sleeve 42 is applied with press fit against the guide surface 37 with pins 38 extending from this, and between these pins located recesses 47, and the end surfaces 45 of which pins are perpendicular relatively the length axis 24 of the coupling house 11, which in turn is coaxial with the optical axis of the connection device. At a connection of two similar connecting devices 9, said pins 38 will be brought into the recesses 47 of the second connection device so that both connecting devices are loca- ted in the exact axial extension of each other. The manu¬ facture of the coupling house is appropriately carried out by turning, whereby the conical recess 17, the channel 18, the seat 19 and the guide surface 37 are turned at one and the same tooling in the lathe, so that these are absolutely mutually coaxial. The manufacturing process thereby becomes simple and cheap. The lens 12 is constituted by a lens body 20, with a front partial spherical surface 21 and a rear, flat end surface 22, that is perpendicular to the longitudinal axis of the lens. The end surfaces 21 and 22 of the lens are anti-reflex treated to achieve as loss free and free of reflexes trans¬ mission as possible. The lens 12 is pressed with its partial spherical end against the seat 19, by means of a spring 25 or the like, which spring also acts on the plug 13, which with its front end surface bears against the lens 12 with a even pressure. By giving the lens 12 a play 26 in the late¬ ral direction, this may be centered under the pressure of the plug 13. The mobility of the lens along the seat 19 entails that the end surface 23 of the plug 13 comes to full, plan bearing against the end surface 22 of the lens 12 and thereby also the end surface of the fibre. The lens 12 at its rear end is fixed in the channel by means of a lock ring 27, while its front end 21 is protected against dirt and shock by means of a protection glass 29. ~r- 5 The guide-sleeve 15 is constituted by a socket 30, that can be cylindric (according to fig. 2) or conical designed (according to fig. 1). An embodiment of the later is shown in fig. 4 and 5. The socket 30 is formed with resilient sec¬ tors 31, connected to each other via thin, material weakened 10 axial portions 32. The socket 30 is designed with a de¬ creasing diameter in direction towards the lens 12. In this embodiment the inner wall surface of the guide sleeve 15 forms the inner guide element of the plug 13, while the outer envelope surface of the sleeve forms its outer guide 15 element. The conical socket 30 on the inside is shaped after the outer form of the plug 13, which in this embodiment is cylindric. The plug 13 is provided with a peripheral flange 33, which forms a stop for the spring 25, the pre-stress of which is controllable by means of a nut 39. At the pressing 20 of the guide sleeve 15 in the conical recess 17 the thin portions 32 bulge outwards, such as is indicated by dash- dotted lines in fig. 5, and thus the inner limitation of the sleeve therefore can adapt to the diameter of the plug 13. 25 In the embodiment shown fig. 2, a connecting device is dis¬ closed in which the protection glass 29 has been taken away and the conical guide-sleeve 15 has been replaced by a cylindric guide-sleeve, whereby even the channel 18 is cylindric. In this embodiment as well the channel wall is 30 coaxial with the seat 19. The complete connecting device 9 shown in fig. 3 comprises the insertion device 10 according to fig. 1 or alternatively according to fig. 2, a connection sleeve 40 provided with 35 guide segments 44, provided preferably at the front end 35 of the connecting device 9, a barrel nut 41 or the like, and stress-relieving devices 36 for stress-relief of the optical coupling house 11, ie. the end that is intended to be con¬ nected axially with a second connecting device, is formed with a guide dowel 34, the peripheral guide surface 37 of which is coaxial with the longitudinal axis 24 of the coup- ling house 11. A coupling sleeve 42 is applied with press fit against the guide surface 37 with pins 38 extending from this, and between these pins located recesses 47, and the end surfaces 45 of which pins are perpendicular relatively the length axis 24 of the coupling house 11, which in turn is coaxial with the optical axis of the connection device. At a connection of two similar connecting devices 9, said pins 38 will be brought into the recesses 47 of the second connection device so that both connecting devices are loca- ted in the exact axial extension of each other. The manu¬ facture of the coupling house is appropriately carried out by turning, whereby the conical recess 17, the channel 18, the seat 19 and the guide surface 37 are turned at one and the same tooling in the lathe, so that these are absolutely mutually coaxial. The manufacturing process thereby becomes simple and cheap. The lens 12 is constituted by a lens body 20, with a front partial spherical surface 21 and a rear, flat end surface 22, that is perpendicular to the longitudinal axis of the lens. The end surfaces 21 and 22 of the lens are anti-reflex treated to achieve as loss free and free of reflexes trans¬ mission as possible. The lens 12 is pressed with its partial spherical end against the seat 19, by means of a spring 25 or the like, which spring also acts on the plug 13, which with its front end surface bears against the lens 12 with a even pressure. By giving the lens 12 a play 26 in the late¬ ral direction, this may be centered under the pressure of. the plug 13. The mobility of the lens along the seat 19 entails that the end surface 23 of the plug 13 comes to full, plan bearing against the end surface 22 of the lens 12 and thereby also the end surface of the fibre. The lens 12 Reference numerals 9 Connecting device 10 Insertion device 11 Coupling house 12 Lens 13 Plug 14 Optical fibre 15 Guide sleeve 16 Accommodation 17 Conical recess 18 Channel 19 Seat 20 Lens body 21 Lens front surface 22 Lens rear end 23 Dowel front end 24 Longitudinal axis 25 Spring 26 Play 27 Lock ring 28 Protection 29 Protection glass 30 Conical sleeve 31 Resilient sector 32 Axial portions 33 Peripheral flange 34 Guide pin 35 Front end of the connecting device 36 Stress-relief device 37 Guide surface 39 Nut 40 Connection sleeve 41 Barrel nut 42 Coupling sleeve 43 Optical fibre cable 44 Guide End surface Connection nut Recess

Claims: CLAIMS 1. Connecting device for axial connection of the end por¬ tions of optical fibres (14) with another, which are fixed in at least one plug (13) each provided in a coupling house (10), in order to provide an optical connection between the fibres via a lens (12) connectable to each fibre end, c h a r a c t e r i z e d t h e r e i n , that each lens (12) is constituted by a lens body (20), the front end surface (21) of which is partially spherical and the opposite, rear end surface (22) of which is arranged perpendicular against the longitudinal axis of the lens body (24), that in the coupling house (11) a ring shaped, partially spherical or conical seat (19) is provided for the front end surface of the lens body, which seat is concentric with the longitudinal axis of the coupling house, that the plug (13) is insertable in a coaxial guide sleeve (15) guided in the coupling house (11), and that the front end of the plug, which is perpendicular to its longitudinal axis, can be pressed to bearing against the rear end surface (22) of the lens body (20) so that the partial spherical end surface of the lens body front, is pressed to bearing against the seat achieving a centering of the lens (12), the plug (13) and the coupling house (11) relatively each other. 2. Connecting device according to claim 1, c h a r a c t e r i z e d t h e r e i n , that the envelope surface of the guide sleeve (15) is coni- cal, with a diameter decreasing in direction towards the lens (12) or cylindric, and that the guide sleeve (15) is insertable in an axial recess (17) provided in the coupling house (11) designed with complementary form, which recess is concentric with the ring shaped seat (19) of the coupling house. 8 End surface Connection nut Recess

Inventors: NODFELT INGVAR, NODFELT, INGVAR
Applicants: NODFELT INGVAR, NODFELT, INGVAR
Application year: 1993
Main classification: G02B6
IPC codes: G02B6