IE912399A1

IE912399A1 - Device for transmitting light

Info

Publication number: IE912399A1
Application number: IE239991A
Authority: IE
Original assignee: Siemens Ag
Priority date: 1990-07-10
Filing date: 1991-07-09
Publication date: 1992-01-15
Also published as: DE4022076A1

Abstract

The coupler is used between an opto-electronic component (14) and the incident face of an optical fibre and uses a lens (8) inserted in the light path. The optical fibre end (3) is enclosed by a sleeve (1) providing a gas-tight fixing for the spherical lens and attached to the base plate (13) for the opto-electronic component via a gas-tight bond, eliminating the need for a separate housing for the opto-electronic component. Pref., the spherical lens is secured in the sleeve by plastic deformation of the latter. ADVANTAGE - Reduced light losses.

Description

The invention relates to a device for transmitting light between an optoelectronic component arranged on a base-plate and the end of an optical fibre having a ferrule which grips this end, in which a lens that focuses the light between the optoelectronic component and the optical fibre is mounted, and having a housing which seals the optoelectronic component gas-tight.

Such a device is disclosed, for example, in European Patent 0,155,528. In the design described there, an optoelectronic component is used which is sealed gastight in a commercial housing. This housing has a window for the passage of the radiation generated or absorbed by the component. Thus, when transferring from the optical fibre end to the optoelectronic component or visa versa, a light has to traverse two solid bodies, specifically the spherical lens and the window of the gas-tight housing of the optoelectronic component. In this case, disturbing attenuation occurs due to instances of refraction at the surfaces and to transmission losses.

It is therefore the object of the invention to reduce the radiation attenuation between the optical fibre end and the optoelectronic component in a device of the type mentioned at the beginning.

The object is achieved according to the invention when the lens is mounted gas-tight in the ferrule and when, together with the ferrule and the base-plate, the lens forms the housing, which seals the optoelectronic component gas-tight.

Due to the design according to the invention, the lens, which is mounted in the ferrule, simultaneously fulfils the function of focusing the light between the optical fibre end and the optoelectronic component and, on the other hand, the function of sealing the housing of the optoelectronic component, which is formed from the base-plate and the ferrule, gas-tight. No further housing is provided for the optoelectronic component, so that, apart from the lens, no further element stands in the way - 2 of the radiation to be overcoupled. Due to the gas-tight sealing of the housing, it is ensured that no harmful gases can penetrate to the component from outside. When producing the device, the air can be pumped out of the housing before the latter is sealed gas-tight, so that any sort of dampness is also removed from the housing. Thereafter, the housing can be refilled with a dried gas. This gas is expediently chosen such that the sensitive parts of the optoelectronic component are not attacked by the gas.

The invention can advantageously be configured such that the lens is a spherical lens, and that the spherical lens is pressed gas-tight into the ferrule in a known way with plastic deformation thereof.

By pressing a spherical lens, preferably a glass lens or a sapphire lens, into a ferrule with plastic deformation of the inner wall of the ferrule, a gas-tight fitting of the spherical lens into the ferrule is achieved in a simple way. This process is the subject of German Offenlegungsschrift 3,829,067, to which reference is hereby made with respect to more precise details.

A further advantageous embodiment of the invention provides that the optoelectronic component is mounted centrally on the base-plate, and that the base25 plate has a circular elevation whose outside diameter is smaller than the inside diameter of the ferrule at its end, and in whose centre the optoelectronic component is mounted on the base-plate.

For the purpose of producing the device, the ferrule can be slipped over the elevation of the baseplate, and thus preadjusted. The distance of the lens from the optoelectronic component is then already fixed by the length of the ferrule and the arrangement of the optoelectronic component on the base-plate. In terms of production engineering, this distance can be kept with adequate precision by machining the ferrule and the baseplate so that no further adjustment is required with respect to this distance. The ferrule with the lens must only still be adjusted in the radial direction relative - 3 to the optoelectronic component.

It turns out to be particularly advantageous for the outside diameter of the elevation to be approximately fifty micrometers smaller than the inside diameter of the ferrule at the end thereof.

Due to this configuration, after the ferrule has been mounted on the base-plate the preadjustment is already so precise that the transmission of light between the optical fibre end and the optoelectronic component is possible in any case. Further adjustment can be performed in such a way that the device is operated and the overcoupled radiation intensity (light or infrared radiation) is measured while the ferrule is re-adjusted with respect to the base-plate. This can also be done by means of an automatic device.

The end face of the ferrule can thereafter be mounted gas-tight on the base-plate by means of resistance welding. During resistance welding, no forces arise which cause the surfaces to be welded to undergo mutual shearing. As a result, the adjustment is maintained during the welding process.

It can likewise be advantageous when the end face of the ferrule is mounted gas-tight on the base-plate by means of laser welding. Laser welding permits the gas25 tight connection between the ferrule and the base-plate to be produced without the use of force.

The end face of the ferrule can also advantageously be connected to the base-plate by soldering.

Furthermore, the invention comprises a process 30 for producing a device for transmitting light between an optical fibre end and an optoelectronic component, in which process the air is extracted from the housing before the latter is sealed gas-tight, and the housing is filled with a gas cleared as far as possible of dampness.

The light-emitting diode or PIN diode installed in the device may not be directly exposed to dampness.

Consequently, the air is extracted before the housing is welded and replaced by a dry gas, for example dried nitrogen, or, for subsequent verification of tightness, - 4 10 helium. It is ensured in this way that the diode is not damaged even over a long time under the influence of the gas surrounding it.

Furthermore, the process according to the invention can be configured such that together with the lens mounted gas-tight in it, the ferrule can be slipped with its end face over the elevation of the base-plate, and the light intensity overcoupled between the optical fibre end and the optoelectronic component by the radial adjustment of the ferrule is maximised, and the ferrule is thereafter welded gas-tight to the base-plate.

This process permits a simple and reliable, precise adjustment of the ferrule with respect to the base-plate, and is also easy to carry out by means of an automatic device.

The invention is shown below with reference to an exemplary embodiment in a drawing and subsequently described.

In this drawing, the single figure shows the device according to the invention in a diagrammatic longitudinal section.

The ferrule 1 has a continuous opening, which is subdivided into various sections of different diameter. In a first section 2, the ceramic ferrule 4 is gripped together with the optical fibre end 3 mounted in it. Arranged at the bottom of this first section 2 is a stopplate 5 for the ceramic pin 4. In the middle, the stopplate 5 has an opening 6 for passage of the light to or from the optical fibre end 3.

Joined to the first section 2 is a second section 7, in which the spherical lens 8 is mounted gas-tight. The spherical lens 8 is pressed gas-tight in the region of the second section 7 with plastic deformation of the inside wall of the ferrule 1. The opening of the ferrule 1 expands in a funnel shape in a third section 9. The fourth section 10 forms the end section of the ferrule, and extends up to the end face 11 thereof. The inside diameter of the fourth section 10 is approximately fifty micrometers larger than the outside diameter of the - 5 elevation 12 of the base-plate 13. Since, on the one hand, the spherical lens 8 is arranged very precisely in the centre of the ferrule 1, and since the fourth section 10 of the opening in the ferrule 1 is arranged precisely concentrically with the spherical lens 8, the result of the relatively precise fit between the fourth section 10 of the opening in the ferrule 1 and the elevation 12 of the base-plate 13 is that the spherical lens 8 is relatively precisely arranged on the central axis of the elevation 12 of the base-plate 13.

The optoelectronic component 14 is arranged, for its part, precisely at the centre of the elevation 12 of the base-plate 13. As a result, there is an adequately precise pre-adjustment between the spherical lens 8 and the optoelectronic component 14. The pre-adjustment suffices to overcouple so much light between the optoelectronic component 14 and the optical fibre end 3 that the overcoupled light intensity can be measured for the purpose of further fine adjustment. In the fine adjust20 ment, the ferrule 1 is moved against the base-plate 13 such that the overcoupled light intensity reaches a maximum. Once an optimum end position has been reached in the adjustment, the ferrule 1 is welded to the base-plate 13. For this purpose, an annular elevation 15, which facilitates welding, is provided on the end-face 11 of the ferrule 1.

The ferrule 1 and base-plate 13 can be welded to one another gas-tight particularly easily by means of resistance welding.

The optoelectronic component 14 is, for example, a PIN diode. A PIN diode without a housing can be used in the design according to the invention of the coupling device. As a result, on the path between the optical fibre end 3 and the diode 14 the light need traverse only a single glass body, specifically the spherical lens 8, and pass only two interfaces. When the diode 14 is coupled to the optical fibre end 3, the result of this is a reduction in attenuation.

The supply leads 16 of the diode 14 are led - 6 through glass encapsulations 17 through the base-plate 13. A reliably gas-tight sealing of the diode in the space formed by the spherical lens 8, the ferrule 1 and the base-plate 13 is ensured in this way.

Claims

Patent Claims 1. Or one of the following, characterised in that the end face (7) of the ferrule (1) is mounted gas-tight on the base-plate (13) by means of resistance welding.

1. Device for transmitting light between an optoelectronic component arranged on a base-plate and the end of an optical fibre having a ferrule which grips this

2. Device according to Claim 1, characterised in that the lens (8) is a spherical lens, and in that the 15 spherical lens is pressed gas-tight into the ferrule (1) in a known way with plastic deformation thereof. 3. , characterised in that the outside diameter of the elevation (12) is approximately fifty micrometers smaller than the inside diameter of the ferrule (1) at the end thereof. 30 5. Device for transmitting light according to Claim

3. Device for transmitting light according to Claim 1 or 2, characterised in that the optoelectronic component (14) is mounted centrally on the base-plate (13), 20 and in that the base-plate (13) has a circular elevation (12) whose outside diameter is smaller than the inside diameter of the ferrule (1) at its end, and in whose centre the optoelectronic component (14) is mounted on the base-plate (13). 25

4. Device for transmitting light according to Claim

5. Is extracted from the housing before the latter is sealed gas-tight, and the housing is filled with a gas cleared as far as possible of dampness. 5 end, in which a lens which focuses the light between the optoelectronic component and the optical fibre is mounted, and having a housing which seals the optoelectronic component gas-tight, characterised in that the lens (8) is mounted gas-tight in the ferrule (1), and in

6. Device for transmitting light according to one of 35 Claims 1 to 4, characterised in that the end face (11) of the ferrule (1) is mounted gas-tight on the base-plate (13) by means of laser welding.

7. Device for transmitting light according to one of Claims 1 to 4, characterised in that the end face (11) of the ferrule (1) is connected to the base-plate (13) by means of soldering.

8. Process for producing a device according to Claim 1 or one of the following, characterised in that the air

9. Process according to Claim 7, characterised in that together with the lens (8) mounted gas-tight in it,

10. A device for transmitting light according to any preceding claim substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. 10 the ferrule can be slipped with its end face over the elevation (12) of the base-plate (13), and in that the light intensity overcoupled between the optical fibre end (3) and the optoelectronic component (14) by the radial adjustment of the ferrule (1) is maximised, and in that 15 the ferrule (1) is thereafter welded gas-tight to the base-plate (13). 10 that, together with the ferrule (1) and the base-plate (13), the lens (8) forms the housing which seals the optoelectronic component (14) gas-tight.

11. A process for producing a device according to claim 1, according to any preceding claim substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.