GB2075709A

GB2075709A - Opto-electronic component

Info

Publication number: GB2075709A
Application number: GB8112844A
Authority: GB
Original assignee: Telecommunications SA Comp Ind; Compagnie Industrielle de Telecommunication CIT Alcatel SA
Current assignee: Telecommunications SA Comp Ind; Alcatel CIT SA
Priority date: 1980-04-30
Filing date: 1981-04-27
Publication date: 1981-11-18
Also published as: IT8167581A0; FR2481815A1; DE3116252A1; JPS56169379A; NL8102017A; IT1144205B

Abstract

The opto-electronic component provides an interface between an optical fibre and an electrical communications link. An opto-electronic diode pellet (2) mounted on the end of a cylindrical electrode (1). The diode is a photo-diode or a light- emitting diode depending on the direction of transmission. The face of the pellet on the electrode is conductive and constitutes a first electrical connection thereto. On its other face, the diode has a photoactive region (7) looking into an optical fibre (3). A tubular positioning member (not shown in Fig. 1) ensures that the diode and the optical fibre are held in proper relationship with each other. Surrounding the photoactive region there is a contact zone (8) for a second electrical contact to the diode. This zone is connected to a second electrode which is tubular, and which is coaxial with the first. Depending on the embodiment, the second electrode may either surround the first electrode, or alternatively it may surround a length of the optical fibre. <IMAGE>

Description

SPECIFICATION Opto-electronic component The present invention relates to opto-electronic components intended to interface between the end of an optical fibre for transmitting light signals and the end of a link for transmitting electrical signals.

Transmitting data in the form of light signals via optical fibres has considerable technical and economic advantages over transmitting data in the form of electrical signals via conductors. However, in practice the data is only processed when it is in electrical form.

Consequently, when use is to be made of data transmitted optically, or when data available in electrical form is to be transmitted, it is necessary to convert optical signals into electrical signals or electrical signals into optical signals.

Such conversions are performed by optoelectronic devices, such as photodiodes and light-emitting diodes (LEDs). Naturally a photodiode or an LED has both to be connected to an electric circuit via electric conductors, and to be positioned very accurately in relation to the optical fibre(s) being used.

It is difficult to obtain and then to maintain such positioning without sometimes breaking the fibres, particularly when the opto-electronic diode is part of a hybrid circuit disposed in a plane perpendicular to the direction of arrival of the fibre.

Preferred embodiments of the present invention thus provide opto-electronic components which are made in a discrete form similar to that of conventional discrete electronic components, thereby reducing problems of manufacture and assembly into a circuit because of the very similarities with conventional electronic components in form and manufacture. Saiopt-electronic components also interface easily with optical ibres.

The present invention provides an optoelectronic component for interfacing between the end of an optical fibre for transmitting light signals and the end of a link for transmitting electric signals, the component comprising an opto-electronic diode having first and second electrodes for connection to respective conductors of the link for transmitting electrical signals, and having its photo-active portion looking into the end of the optical fibre from such a position and at such a distance that that one of the diode and the fibre which is the receiver of light signals is in the field of action of the other one of them which is the sender of light signals, wherein:: - the first electrode is cylindrical; - the opto-electronic diode is in the form of a pellet having two major faces, with a photoactive zone and an electrically conductive contact zone around said photoactive zone on one of its major faces, while its other major face is fastened to and in electrical contact with one end of said cylindrical first electrode; - the second electrode is tubular, is disposed coaxially with the first electrode and is electrically connected to the contact zone-on the opto-electronic diode; and - a tubular positioning member is provided for holding the optical fibre in position relative to the opto-electronic diode and the first electrode.

Embodiments of the invention are described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective diagram of some of the essential elements of the invention; Figure 2 is a partial axial section through an opto-electronic component in accordance with the invention and having in-line electrodes; Figure 3 is a partial axial section through an opto-electronic component in accordance with the invention and having coaxial electrodes glued to a tubular positioning member; and Figure 4 is a partial axial section through an opto-electronic component in accordance with the invention and having coaxial electrodes envelopped in a tubular positioning member.

Fig. 1 shows some of the essential elements of the invention, said elements comprising a first electrode 1, a photoactive diode 2, an optical fibre 3 and its protective covering 4.

Two elements are not shown in Fig. 1; these are a second electrode and a member for positioning the optical fibre 3 relative to the opto-electronic diode 2, both will be described in greater detail with reference to Figs. 2, 3 a 4.

The end of the first electrode 1 is arranged to receive an opto-electronic diode. Thus the electrode 1 is essentially cylindrical in form and may be constituted by a conductive rod as shown in Fig. 2, or by a conductive part in the form of a flat-headed nail, as shown in Figs. 3 a 4.

Depending on requirements, the opto-electronic diode 2 is a light-emitting diode if it receives the signals to be transmitted in electrical form, or a photo-sensitive diode if it receives the signals to be transmitted in optical form. The opto-electronic diode 2 is constituted by a semi-conductor pellet, and may be a PirPN or PIN type of semiconductor diode, for example.

One of the two major faces of the pellet has a photoactive zone 7 at its centre, and an electrically conductive contact zone 8 surrounding the photoactive zone 7. The contact zone constitutes a second terminal of the diode 2.

The other face of the pellet is electrically conductive and constitutes a first terminal of the diode 2. It is fastened to the end of the first electrode 1 and is in electrical contact therewith.

The tubular second electrode, not shown, is electrically connected to the contact zone 8 in a manner that is described in greater detail with reference to the following figures.

A positioning member acts directly or indirectly to position one end of the optical fibre 3 relative to the photoactive zone of the optoelectronic diode 2, in such a manner that that one of the diode and the fibre which is the receiver of light signals is in the field of action of the other This is conventionally achieved by positioning the end of the optical fibre directly opposite the photoactive zone 7.

Figs. 2, 3 a 4 show several variants of the invention which correspond to different manufacturer requirements (depending on their facilities) and on different user requirements (depending on their applications).

Fig. 2 shows a first variant which has particularly low inter-electrode capacitance, and enables an optical fibre to be introduced into the component after it has been assembled on a circuit board or in a hybrid circuit.

In this variant the first and second electrodes 1 a 8 6a are preferably of the same outside diameter. The first electrode 1 a is constituted by a rod with the opto-electric diode 2a mounted at its end as described above. The opto-electronic diode 2a has an electric contact zone 8a which is preferably annular.

The second electrode 6a is tubular, the inside diameter of the capillary tube which it forms is slightly larger than the diameter of the optical fibre 3a so that it serves as a positioning guide for the fibre. A first end of the tube formed by the second electrode 6a comes into contact with the ring-shaped electrical contact zone 8a, and is soldered, brazed or pressed thereto in order to ensure the required continuity of conduction.

The positioning member 5a is constituted by a tube which embraces both electrodes and thereby centres them.

In one embodiment the electrodes are made of an alloy such as "DUMEr' which enables glass-to-metal sealing, and the positioning member 5a is made of a low melting point glass and ensures that the component thus constituted is held together by sealing.

A suitable length of the optical fibre 3a is introduced into the second electrode 6a, and the fibre and its protective covering 4a are fastened to the electrode 6a. This may be done for example by gluing the end of the optical fibre to the photoactive zone by means of a glue having good light transmitting qualities, such as a silicone or an epoxy. The.

protective covering 4a is held in position relative to the electrode 6a by a sleeve 9a which may be shrunk on or glued to both parts.

Fig. 3 shows a second variant in which the first electrode 1 b has a nail's head connexion surface on which the opto-electronic diode 2b is positioned. Electrical connexion between the electrode and the diode is provided as in the preceding variant. The first electrode 1 b is housed inside the second electrode 6b which is in the form of a conductive tube of greater inside diameter than the maximum diameter of the nail's head at the end of the first electrode, thereby leaving room to insert an insulating spacer member between the electrodes, e.g. an insulating resin or beads of glass. The spacer member 1 0b thus constituted is shown here as a block of insulating resin which both positions and holds the first electrode inside the second.In a preferred embodiment of the invention the ends of the first and second electrodes 1 b and 6b that are in inside the opto-electronic component are situated in practically the same plane, while the first electrode 1 b is longer than the second electrode 6b, and therefore projects beyond it for connexion to an outside circuit.

The second electrode 6b is connected to the electrical contact zone 8b of the optoelectronic diode 2b by a connecting wire 11 b bonded at both ends.

The optical fibre 3b is positioned relative to the photoactive zone 7b of the opto-electronic diode 2b by means of a jig (not shown), and it is held in position by means of a drop 1 2b of glue having good light-transmitting qualities holding the end of the optical fibre 3b to that face of the opto-electronic diode 2b which has the photoactive zone 7b and the electrical contact zone 8b.

The optical fibre 3b and its protective covering 4b are fastened to the electrodes 1 b and 6b as well as to the block of resin 1 0b by a resin casting which constitutes the positioning member 5b of the opto-electronic component thus formed. In one embodiment the positioning member 5b is cylindrical, and extends over a portion of the second electrode 6b to insulate it electrically except where it is intended to be connected to an outside circuit.

Fig. 4 shows a third variant which avoids the use of a jig and the subsequent casting required in the manufacture of the preceding variant. It enables the optical fibre to be inserted in the component after the component has been mounted on a printed or a hybrid circuit.

This variant of the opto-electronic component comprises the first electrode 1 c, an optoelectronic diode 2c, a second electrode 6c, an insulating spacer member 1 Oc and a connexion wire 11 c which are practically identical to the corresponding items shown in Fig. 3.

In contrast, the positioning member Sc is constituted by a tubular metal part which is crimped around the second electrode Sc at 13c.

The positioning member Sc is tubular and includes a first portion whose inside diameter is slightly larger than the outside diameter of the second electrode 6c to which it is crimped. The length of the first portion is chosen so as to leave a void in front of the face of the opto-electronic diode 2c which includes the photoactive zone 7c and the contact zone 8c. A second portion of the positioning member Sc has a slightly larger diameter than the protective covering 4c of the optical fibre 3c to serve as a guide therefor.

As in the previous variants, the end of the fibre may be glued to the photoactive zone.

In a particular embodiment of this variant, the second portion of the positioning member Sc includes an axial recess 1 4c leading to the outside and having a rather larger diameter than the inside diameter of the remainder of the second portion of the member 5c. A spring 1 sic is wound around the protective covering 4c and is inserted into the axial recess 1 4c and jammed therein so as to hold the covering by means of its own resilience.

Whatever the variant used, a component in accordance with the invention can be assembled in a circuit like a conventional diode or resistor by soldering the projecting portions of the electrodes to circuit pads, or by using connexion tabs or ribbons. In particular, it is possible to place the components with their axes disposed in a plane parallel to the plane of the circuit to which their electrodes are connected so that the optical fibre lies in a plane parallel to that of the circuit. For a small circuit, the opto-electronic component(s) can be potted in the same potting compound as the circuit, thereby providing some of the strength for holding the component(s) in position.

Claims

1. An opto-electronic component for interfacing between the end of an optical fibre for transmitting light signals and the end of a link for transmitting electric signals, the component comprising an opto-electronic diode having first and second electrodes for connection to respective conductors of the link for transmitting electrical signals, and having its photoactive portion looking into the end of the optical fibre from such a position and at such a distance that that one of the diode and the fibre which is the receiver of light signals is in the field of action of the other one of them which is the sender of light signals, wherein:: - the first electrode is cylindrical; - the opto-electronic diode is in the form of a pellet having two major faces, with a photoactive zone and an electrically conductive contact zone around said photoactive zone on one of its major faces, while its other major face is fastened to and in electrical contact with one end of said cylindrical first electrode; - the second electrode is tubular, is disposed coaxially with the first electrode and is electrically connected to the contact zone on the opto-electronic diode; and - a tubular positioning member is provided for holding the optical fibre in position relative to the opto-electronic diode and the first electrode.

2. An opto-electronic component according to claim 1, wherein: - the two electrodes are disposed on opposite sides of the opto-electronic diode, and are held in place by the tubular positioning member which constitutes a sealed and electrically insulating housing inside which the opto-electronic diode and portions of said electrodes are situated; - the second electrode is in contact with the electrical contact zone situated on the second face of the opto-electronic diode, and has an inside diameter slightly greater than the outside diameter of the fibre which passes therethrough and is guided thereby; and - the covering of the optical fibre is fastened to that end of the second electrode which is not in contact with the opto-electronic diode.

3. An opto-electronic component according to claim 2, wherein both electrodes have the same outside diameter, and are inserted inside a tubular positioning member made of glass.

4. An opto-electronic component according to claim 3, including a connecting sleeve for the covering of the fibre and the second electrode, said sleeve being fastened to the covering and to the electrode.

5. An opto-electronic component accordingAo claim 1, wherein: - the first electrode is housed inside the second, and is held in place by a spacer of insulating material; and - a connecting wire provides electrical con- nection between the contact zone of the optoelectronic diode and the end of the second electrode which is closest to said contact zone.

6. An opto-electronic component according to claim 5, wherein the spacer of insulating material is in the form of a block of resin.

7. An opto-electronic component according to claim 5, wherein the spacer of insulating material is in the form of a glass bead.

8. An opto-electronic component according to claim 5, 6 or 7, wherein: - the end of the optical fibre is fastened to and positioned with respect to the photoactive zone of the opto-electronic diode by means of a drop of light conducting glue; and - the tubular positioning member is made by moulding insulating meterial around the fibre and its covering, and fastened thereto by gluing to those ends of the electrodes and of the fill that are closest to the opto-electronic diode.

9. An opto-electronic component according to claim 5, 6 or 7, wherein the tubular positioning member comprises: - a first portion with an inside diameter slightly larger than the outside diameter of the second electrode, around which said tubular positioning member is crimped, said first portion serving as a housing for the two elec trodes and the opto-electronic diode; and - a second portion with an inside diameter slightly larger than the outside diameter of the covering of the fibre which passes therethrough and is guided thereby.

10. An opto-electronic component according to claim 9, including a spring wound round the covering of the optical fibre and partially housed in an axial recess in the tubular positioning member in which it is fixed, said spring being fixed to the covering by its own resilience.

11. An opto-electronic component substantially as herein described, with reference to, and as illustrated in, Fig. 1 and any one of Figs. 2, 3 s 4 of the accompanying drawings.