WO2008142297A1

WO2008142297A1 - Optical fibre transmission method and device

Info

Publication number: WO2008142297A1
Application number: PCT/FR2008/000537
Authority: WO
Inventors: Regis Hamelin; Jean-Charles Garcia
Original assignee: Intexys
Priority date: 2007-04-17
Filing date: 2008-04-16
Publication date: 2008-11-27
Also published as: FR2915334A1

Abstract

The device for bidirectional communication over an optical fibre (105) comprises, at at least one end of said optical fibre: a first convergent lens (110), a splitter plate (115) adapted to reflect light rays in a first range of wavelengths and to be passed through by light rays in a second range of wavelengths, opposite one of the faces (120) of the splitter plate, a plurality of convergent lenses (125) each associated with a laser (130 to 136), the lasers being located on the same face of the splitter plate emitting in different and adjacent wavelengths and opposite another of the faces (140) of the splitter plate, a plurality of convergent lenses (145) each associated with a photoreceiver (150 to 156), the photoreceivers being located on the same face of the splitter plate being adapted to receive different and adjacent wavelengths.

Description

METHOD AND DEVICE FOR TRANSMISSION ON OPTICAL FIBER

The present invention relates to a method and an optical fiber transmission device. It is particularly relevant to the field of telecommunications.

Bidirectional optical fiber communication devices are known, that is to say whose equipment at the end of an optical fiber makes it possible both to transmit and to receive light signals propagating in the same optical fiber in two opposite directions. These systems implement a different wavelength of light for each of the directions of propagation of the light rays on the optical fiber. At each end of the optical fiber is associated a dichroic plate which reflects the light rays having one of the wavelengths and which does not reflect the light rays having the other of these wavelengths. Thus, by associating a laser source emitting in one of the wavelengths considered at one of the faces of the blade, either so that the light rays emitted by the laser are reflected therein, or so that they cross it and by associating a photodiode with the other of the faces of the blade, so that the light rays coming from the optical fiber pass through it or are reflected therein, respectively, the optical paths are separated from the rays entering the optical fiber and rays coming out of the optical fiber. These devices have the disadvantage of being able to convey only one light signal in each direction of propagation in the optical fiber.

Other mono-directional devices are known that make it possible, by a set of lenses, to multiplex or demultiplex light rays of different wavelengths propagating all in the same direction in the optical fiber. To achieve bidirectional communication, two of these devices must be implemented.

The present invention aims to remedy these disadvantages. For this purpose, according to a first aspect, the present invention aims a bidirectional communication device on an optical fiber, characterized in that it comprises, in at least one end of said optical fiber: a first convergent lens, a splitter blade adapted to reflect light rays in a first wavelength range and to be traversed by light rays in a second wavelength range, in front of one of the faces of the separating plate, a plurality of convergent lenses each associated with a laser, the lasers being on the same face of the separating plate emitting in different and similar wavelengths and opposite another face of the separating plate, a plurality of convergent lenses each associated with a photoreceptor, the photoreceptors lying on the same face of the separating plate being adapted to receive different wavelengths and neighboring .

Thanks to these arrangements, a bidirectional multi-channel communication can be established on a single optical fiber with a compact device with low mechanical tolerances, which improves the efficiency and reduces the signal losses or inter-modulations between the channels.

According to particular features, the separating blade is formed in a separator cube. Thanks to these provisions, the mechanical strength of the various optical components can be performed directly on the separator cube.

According to particular characteristics, each photoreceptor is associated, at the input, with a filter which specifically selects the light rays intended for said photoreceptor. Thanks to these provisions, the construction of the device is simplified.

According to particular characteristics, each photo-receiver is associated, at the output, with a very high linearity amplifier. Thanks to these arrangements, it is possible to implement the device for transmissions of analog signals.

According to particular characteristics, at least one of the sets of lasers or photoreceptors is connected to an integrated control circuit by a flexible sheet of electrical conductors. Thanks to these arrangements, the components connected on either side of the splitter blade can be connected to the same integrated circuit.

According to particular characteristics, at least a portion of the lenses associated with lasers and photoreceptors are diffractive lenses.

According to particular characteristics, at least a portion of the lasers or photoreceptors are mounted on a support via micro-beads. Thanks to these arrangements, the positioning of the components mounted on micro-ball is very accurate, the electrical connection of these components is easy, through micro-conductive balls.

According to particular characteristics, the lenses associated with the photo-receivers are integrated on a support placed opposite the photo-receivers. According to particular features, said lens support is mounted on the support of the photoreceptors, via micro-beads. Thanks to these arrangements, the optical positioning of the lenses relative to the photoreceptors is accurate in all three dimensions. According to particular characteristics, the lenses associated with the lasers are integrated on a support placed next to the lasers.

According to particular features, said lens support is mounted on the support of the lasers, by means of microbeads. Thanks to these arrangements, the optical positioning of the lenses relative to the lasers is accurate in all three dimensions.

According to particular features, the first convergent lens has a substantially spherical shape.

According to a second aspect, the present invention aims a bidirectional communication method on an optical fiber, characterized in that it comprises: a step of mounting, in at least one end of said optical fiber: o a first convergent lens, a separator plate adapted to reflect light rays in a first wavelength range and to be crossed by light rays in a second wavelength range, or opposite one of the faces of the separating plate, a plurality of convergent lenses each associated with a laser, the lasers being on the same face of the separating plate emitting in different wavelengths and neighboring and o opposite another of the faces of the separating blade, a plurality of convergent lenses each associated with a photoreceptor, the photoreceptors lying on the same side of the separator blade being adapted to receive long and a step of transmitting optical signals with said lasers and receiving said optical signals with said photoreceptors.

The advantages, aims and characteristic of said method being similar to those of the device, as described above, they are not recalled here.

Other advantages, aims and features of the present invention will emerge from the description which follows, made for an explanatory and non-limiting purpose with reference to the appended drawings, in which: FIG. 1 schematically represents, in section, an embodiment 2 schematically represents, in section, a mounting of lenses and photo-receivers integrated in the device illustrated in Figure 1 and - Figure 3 shows schematically, in section, a mounting of lenses and lasers integrated in the device illustrated in FIG.

FIG. 1 shows a device 100 for bidirectional communication on an optical fiber 105. This device 100, mounted at one end, has an angle u u comprises a first convergent lens 110 and a splitter plate 115. The first convergent lens 110 has a substantially spherical shape.

The splitter plate 115 is adapted to reflect light rays in a first wavelength range, here between 850 and 910 nm, and to be traversed by light rays in a second wavelength range, here between 1310.degree. and 1370 nm. In the embodiment illustrated in FIG. 1, the separating blade 115 is formed in a separator cube, in a manner known per se.

Opposite a face 120 of the separating plate 115 which is located on the axis of the end of the optical fiber 105, are arranged second convergent lenses

10,125 each associated with a laser 130 to 136. The lasers 130 to 136 are, for example, surface emission lasers known as VCSELs (acronym for Vertical Cavity Surface Emitting

Laser). The lasers 130 to 136 emit respectively in wavelengths of

1310, 1330, 1350 and 1370 nm such that the light rays emitted by the lasers

130 to 136 are concentrated by the second convergent lenses 125, pass through the blade

Separator 115, are concentrated by the first convergent lens 110 and enter the optical fiber 105.

Opposite a face 140 of the separating plate 115 towards which light rays coming from the optical fiber 105 are reflected, are arranged third convergent lenses 145 associated, each with a photoreceptor 150 to 156. The photoreceptors

150 to 156, for example photodiodes, are respectively photosensitive for wavelengths of 850, 870, 890 and 910 nm. In this way, the light rays having these wavelengths from the optical fiber 105 are concentrated by the first convergent lens 110, are reflected by the splitter plate 115, are concentrated by the third convergent lenses 145 and reach the photoreceptors

150 to 156.

Preferably, each photoreceptor is provided with an antireflection layer over its entire surface facing the corresponding third convergent lens.

To select the wavelengths reaching the photosensitive surfaces of the photoreceptors 150 to 156, each of the photoreceptors is input associated with a filter 160 (see Fig. 2) which specifically selects the light rays for said photoreceptor.

Preferably, for analog signal transmission applications, each photoreceptor 150 to 156 is associated, at the output, with a very high linearity amplifier (not shown).

Each of the sets of lasers and photoreceptors is mounted on an electronic circuit 170 and 175, respectively, these electronic circuits being connected to an electronic control circuit 180 via a flexible sheet of electrical conductors 185 and 190, respectively . Flexible layers of electrical conductors 185 and 190 are simply bonded to the surface and interconnected to the conductors carried on the surface by the electronic circuits.

Preferably, at least a portion of the second and third lenses associated with lasers and photoreceptors are diffractive lenses. FIG. 2 shows a sectional view of an assembly of lenses and photo-receivers on the electronic circuit 175. FIG. 3 shows a sectional view of an assembly of lenses and lasers on the electronic circuit 170.

The lasers 130 to 136, here lasers emission by the slice or VCSEL, and the photoreceptors 150 to 156 are mounted on the support, respectively 200 and 250, of the corresponding electronic circuit, via micro-balls 205.

The third convergent lenses 145 associated with the photoreceptors are integrated on a support 255 placed opposite the photoreceptors 150 to 156. The support

255 of the lenses is mounted on the support 250 of the photoreceptors via micro-balls 210. The second convergent lenses 125 associated with the lasers 130 to 136 are integrated on a support 215 placed next to the lasers 130 to 136 The support 215 lenses is mounted on the support 200 of the lasers, through micro-balls 220.

The supports are, for example, semiconductor materials, for example silicon, where are previously integrated lines of interconnections necessary for the operation of electronic components. Other types of materials are possible to constitute the support, such as silicon carbide, aluminum nitride, gallium nitride, quartz or diamond compatible with the production, on at least one of the faces of the support, conductive tracks (not shown) adapted to the propagation of a microwave electrical signal. A support is previously equipped with electrical tracks, allowing the propagation of a microwave signal, and metallized pads for the transfer by flip-chip technology of various electronic and optoelectronic components, in particular an optoelectronic component, its control circuit and one or several electronic components

(Integrated circuits) necessary for the control of the optoelectronic component or the conversion of the detected signal if the component is a detector, for example a photodiode, as well as the passive electronic components necessary for their operation (not shown).

To produce each of the micro-balls, the deposition of a ball support 255 is thus carried out. This deposit is known in flip-chip technology. Then, the fuse material is deposited on the support at low temperature by evaporation of the metal (indium,

AuSn or other eutectic alloy). The fusible material is then melted and this material spontaneously takes the form of a ball under the effect of surface tension forces. then a reflow, the weld is formed into balls of controlled diameter, typically between 5 microns and 500 microns.

The indium metal taken for example can be replaced by indium-based alloys such as indium-tin (InSn). In the case of indium formation of the beads, the temperature to make the liquid indium is between 160 and 175 ^° C.

Finally, it is placed on these balls, in support, the component, the circuit or the component support to be positioned. Firstly, all the solder balls are made by conventional techniques. These techniques involve different technological steps of resin, lithography, opening of the contact zones, deposition of the fusible material (indium for example), formatting of the balls.

The component is then coated with a thermally conductive and electrically insulating polymer so as to provide mechanical support. Note that following the welding process we can have a phenomenon of self-alignment of the chip. The production of solder balls as well as the coating methods are described in the processes relating to US Pat. Nos. 5,494,669 and 3,915,348.

Resin is then carried out, a conventional method in microelectronics.

In some embodiments, the balls serve both as a support and connector, the conductive tracks being connected to the supports of the balls on either side of the balls. In a higher complexity level, the current and modulation generator of the laser diode can be integrated on a deferred heat sink, made of metal materials (gold, copper, for example) or known for their great conduction properties. thermal (silicon carbide, aluminum nitride, gallium nitride). The solder balls thus realize the electrical connections and make it possible to drain the heat of the component in operation towards the semiconductor support which constitutes a good heat sink. It is clear to those skilled in the art that the greater the number of balls, the greater the contact surface will be and the greater the thermal drainage towards the support will be effective. A coating method with a thermal conductive but electrically insulating polymer element makes it possible to improve the thermal conduction and to solidify the assembly. The electrical connection is thus performed at the same time as the heat dissipation function.

The use of a flip-chip report is motivated by the good microwave performance of this technology and by its self-aligning properties of components, allowing to control their position: the use of flip-chip technology chip "allows the lateral and transverse positioning (i.e. in both axes of the substrate plane) of the component, component support or circuit, with respect to a support. As a result, passive alignment of the electronic, optoelectronic and optical components is realized.

Claims

1 - Bidirectional communication device on the same optical fiber (105), characterized in that it comprises, at at least one end of said optical fiber: - a first convergent lens (110), a splitter blade (115) adapted to reflecting light rays from or to said optical fiber in a first wavelength range and to be traversed by light rays to or from, respectively, said optical fiber in a second range of lengths of a wave different from the first wavelength range, facing one of the faces (120) of the splitter plate, a plurality of convergent lenses (125) each associated with a laser (130 to 136) the lasers being on the same side of the splitter plate, emitting in different wavelengths and neighbors and transmitting light rays to said same optical fiber,

opposite another face (140) of the separating plate, a plurality of convergent lenses (145) each associated with a photoreceptor (150 to 156), the photoreceptors lying on the same face of the separator plate being adapted to receive different wavelengths and neighbors and receiving light rays from said same optical fiber.

2 - Device according to claim 1, characterized in that the separating blade (115) is formed in a separator cube.

3 - Device according to any one of claims 1 or 2, characterized in that, each photoreceptor (150 to 156) is associated, at the input, a filter which specifically selects the light rays for said photo-receiver.

4 - Device according to any one of claims 1 to 3, characterized in that, each photo-receiver (150 to 156) is associated, at the output, an amplifier with very high linearity.

5 - Device according to any one of claims 1 to 4, characterized in that at least one of the sets of lasers (130 to 136) or photoreceptors (150 to 156) is connected to an integrated control circuit ( 180) by a flexible web of electrical conductors (185, 190).

6 - Device according to any one of claims 1 to 5, characterized in that at least a portion of the lenses (125, 145) associated with the lasers (130 to 136) and the photoreceptors (150 to 156) are diffractive lenses .

7 - Device according to any one of claims 1 to 6, characterized in that at least a portion of the lasers (130 to 136) or photoreceptors (150 to 156) are mounted on a support (200, 250) by l Intermediate micro-beads (ZUb, kπυj. 8 - Device according to any one of claims 1 to 7, characterized in that the lenses (145) associated with the photoreceptors (150 to 156) are integrated on a support (255) facing the photoreceptors.

9 - Device according to claim 8, characterized in that said support (255) of the lenses 5 (145) is mounted on the support (250) of the photoreceptors (150 to 156), via micro-beads ( 220).

10 - Device according to any one of claims 8 or 9, characterized in that the lenses (125) associated with the lasers (130 to 136) are integrated on a support (215) placed next to the lasers.

11 - Device according to any one of claims 8 to 10, characterized in that said support (215) of the lenses (125) is mounted on the support of the lasers (200), via micro-balls (220 ).

12 - Device according to any one of claims 1 to 11, characterized in that the first convergent lens (110) has a substantially spherical shape. 13 - Bidirectional communication method on the same optical fiber (105), characterized in that it comprises: a step of mounting, in at least one end of said optical fiber: o a first convergent lens (110), a splitter plate (115) adapted to reflect light rays from or to said optical fiber in a first wavelength range and to be traversed by light rays to or from respectively of said optical fiber, in a second wavelength range different from the first wavelength range, 5 o opposite one of the faces (120) of the splitter plate, a plurality of convergent lenses ( 125) each associated with a laser (130 to

136), the lasers being on the same side of the separating blade emitting in different and similar wavelengths and o opposite another of the faces (140) of the separating plate, a plurality of convergent lenses ( 145) each associated with a photoreceptor (150 to 156), the photoreceptors on the same side of the separator plate being adapted to receive different and similar wavelengths; and

a step of transmitting optical signals with said lasers for transmitting light rays to said same optical fiber, and receiving optical signals from said same optical fiber with said photoreceptors.