WO2004073213A1

WO2004073213A1 - Device for wireless transmission of point-multipoint signals

Info

Publication number: WO2004073213A1
Application number: PCT/FR2004/050050
Authority: WO
Inventors: Yvon Dutertre; Olivier Bouchet
Original assignee: France Telecom
Priority date: 2003-02-10
Filing date: 2004-02-06
Publication date: 2004-08-26
Also published as: FR2851099A1

Abstract

The invention relates to a device for transmission of point-multipoint signals, comprising at least one transmitter unit (4) and at least one receiver unit (5) cooperating by means of an atmospheric optical link. The transmitter unit (4) comprises a single transmitter (E) or a group of transmitters and the receiver unit (5) comprises respectively a group of receivers (r1, r2) or a single receiver. The single transmitter (E) or each of the transmitters part of the group of transmitters is used to illuminate respectively each of the receivers (rl, r2) of the receiver group or the single receiver, without full masking by virtue of respectively at least one other receiver (rl, r2) of the receiver group or at least one other transmitter of the transmitter. The invention can be used to distribute television signals.

Description

POINT-MULTIPOINT SIGNAL TRANSMISSION DEVICE

WITHOUT WIRING

DESCRIPTION

TECHNICAL AREA

The present invention relates to a device for transmitting signals of all kinds, analog, digital, in Internet or other format, point-to-multipoint type, without wiring. Point-to-multipoint transmission means a unidirectional or bidirectional transmission between a central point and a certain number of points

(the transmission is called point-to-multipoint transmission) or vice versa (the transmission then being called point-to-multipoint transmission). Such a transmission device is particularly advantageous in particular for distributing television signals in the various apartments of a building or between different buildings which are aligned, for example located on the same street. Another interesting application can be in particular, the transmission of signals, for example computer signals, between a server located in a room and user stations placed in offices, for example, on either side of a corridor serving the room. .

STATE OF THE PRIOR ART

Currently the distribution of television signals in buildings is done by wiring from a reception system located outside the building to the various apartments to be served. The reception system receives signals to be broadcast, these signals coming for example from a satellite. The wiring is carried out with coaxial cable and distributors and / or amplifiers are installed between the reception system and the destination apartments. This technique is complicated to carry out and therefore expensive, in particular, in old premises which do not lend themselves easily to the passage of cables. In addition, it has very little evolution.

In applications for distributing computer signals to user stations, the signals also pass through cables and the problems mentioned above are encountered.

In general, atmospheric optical links have existed for many years, but they only connect one point to another. They are generally bidirectional, each point comprising a transceiver. They are called point-to-point links. They are used with points distant from a few hundred meters to a few kilometers. They do not allow dissemination.

STATEMENT OF THE INVENTION

The object of the present invention is precisely to propose a point-to-multipoint signal transmission device which does not have the drawbacks mentioned above. More specifically, the present invention proposes to provide a point-to-multipoint signal transmission system which is economical, whose performance is acceptable, which is simple to implement, which does not visually degrade the environment, which is easily adaptable to needs. present and future of users, which has no harmful effect on the health of living beings.

To achieve this, the present invention is a point-to-multipoint signal transmission device, comprising at least one transmission block and at least one reception block cooperating by atmospheric optical link. The transmission block comprises a single transmitter or a group of transmitters and the reception block a group of receivers or a single receiver respectively. The single transmitter or each of the transmitters of the transmitter group is intended to directly illuminate each of the receivers of the receiver group or the single receiver respectively, without complete masking due to at least one other receiver in the receptor group or to at least one other transmitter in the group of transmitters respectively.

The transmission device can be bidirectional, the transmission block forming a first transmission-reception block and the reception block a second transmission-reception block, one of the blocks comprising a single transceiver and the another a group of transceivers.

The positioning of the transmitters in the transmitter group is such that a transmitter in the transmitter group, close to the single receiver, generates when illuminated by a more distant transmitter, a volume of shadow on the side of the single receiver, the single receiver being totally or partially excluded from the volume of shadow. Similarly, the positioning of the group's receivers is such that said receivers, illuminated by the single transmitter, generate a volume of shadow opposite to the single transmitter, no receiver being completely included in a volume d 'shadow.

The shadow volume can be a cylinder or a possibly truncated cone.

The single emitter or each emitter of the emitter group comprises an emissive device intended to emit an optical beam, this device being confined in a housing. This emissive device can be formed by a laser or light-emitting diode.

The single emitter or each emitter of the emitter group may include an optic to conform the optical beam emitted by the emissive device.

The housing can be closed by a transparent window. An encryption device can be placed upstream of the single transmitter or of the transmitters of the group of transmitters, in particular if the signals transmitted are television signals or computer data.

The single receiver or each receiver in the group of receivers may include an optical to electrical conversion device, confined in a housing. The conversion device can be produced by a PIN photodiode or by an avalanche. Instead of the optical to electrical conversion device, one end of the optical fiber can be found in the housing. The housing can be closed by a transparent window.

A color filter can be placed between the window and either the conversion device or the end of the optical fiber to prevent ambient lighting from reaching the conversion device or the end of the optical fiber.

Focusing means can be placed between the window and either the conversion device or the end of the optical fiber. The interior of the housing can be coated with a coating absorbing ambient light, so as to prevent it from reaching the conversion device or the end of the optical fiber when entering the housing. Ambient lighting is defined by any light source whose spectrum covers the wavelength of the optical beam used by the transmission device but which is not part of it. The sun's rays are included in the ambient lighting. The distance between the window of the conversion device or the end of the optical fiber is chosen so that the conversion device or the end of the optical fiber is out of the reach of ambient lighting. At least one of the boxes can be waterproof, this characteristic is important when the boxes are outside.

At least one of the boxes can be intended to be fixed on a support such as a building wall.

To avoid the accumulation of rain or snow, at least one of the windows can be domed. At least one of the windows can be treated with anti-drip. When there is a single transmitter, the latter can transmit a multiplex signal to the receivers of the receiver group. When there is a group of transmitters, the transmitters of the transmitter group preferably transmit multiplex signals to the single receiver.

The single receiver or each receiver in the receiver group is preferably electrically or optically connected to a user device. Advantageously, the transmission block and the reception block can be housed in the same sheath.

They can be integral with the same building.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on reading the description of exemplary embodiments given, by way of purely indicative and in no way limiting, with reference to the appended drawings in which: FIG. 1 schematically shows a point-to-multipoint transmission device according to the invention installed on the front of a building; FIGS. 2A 2B illustrate two transmission devices according to the invention operating with optical beams of different shapes; FIGS. 3A, 3B illustrate the shade on the ground made by the receivers of FIGS. 2A, 2B respectively; FIG. 4 illustrates in detail a receiver of a transmission device according to the invention; FIG. 5 illustrates a point-to-point multipoint transmission device according to the invention; FIG. 6 illustrates a bidirectional point-to-multipoint transmission device according to the invention.

Identical, similar or equivalent parts of the different figures described below have the same reference numerals so as to facilitate the passage from one figure to another.

The different parts shown in the figures are not necessarily shown on a uniform scale, to make the figures more readable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

We will now refer to FIG. 1 which very schematically shows an example of a signal transmission device conforming to the invention. It is assumed that this signal transmission device is intended for distributing analog or digital television signals in different apartments 2 of a building 1. The signal transmission device is located on the facade 3 of the building 1 It comprises an emission block 4 and a reception block 5 which cooperate together by atmospheric optical link. The emission unit 4 is located at the top of the building 1 and comprises a single transmitter E. It is fixed to the building by an appropriate device (not shown) and the transmitter E is slightly overhang relative to the facade 3 of the building 1. The transmission block 4 receives signals to be transmitted, for example from a satellite. This reception has been materialized by an antenna 6 which is connected to the transmission block 4. The signals to be transmitted can be multiplexed in a multiplexer 7 located within the transmission block 4. These signals are transmitted to an emissive device 8 of the single emitter E. This emissive device 8 can be produced by a laser or light-emitting diode for example, intended to emit an optical beam 11 representative of the signals, towards the reception unit 5. This optical beam 11 can be light visible or not. When using an atmospheric optical link, the optical beam is a beam of electromagnetic waves whose wavelength is generally between 0.1 micrometer and 100 micrometers. In the present invention, the wavelength of the optical beam will preferably be between approximately 0.8 micrometer and 1.7 micrometer. An encryption device 23 can be provided to control access to the transmitted signals. Such an encryption device 23 will be placed for example upstream of the transmitter E. In the example described, the optical beam

11 is directed towards the ground and is substantially vertical. Class 1 laser beams with a power of the order of a few milliwatts are suitable for this transmission. Such powers have no harmful effect on the body and especially not on the eyes. The diode 8 is confined in a sealed housing 9 which can contain an optic 10 making it possible to correctly shape the optical beam 11. The housing 9 can be closed by a transparent window 12

The optical beam 11 is substantially in a cone, possibly truncated, or in a cylinder and its opening angle and / or its diameter at the outlet of the housing 9 are defined as a function of parameters of the optical link, such as the distance separating the block from reception 5 of transmission block 4 as well as the composition of reception block 5.

The reception block 5 comprises a group of receivers ri, r2,, the number of receivers of the group corresponding to the number of points to receive the television signals. Each receiver ri, r2, of the group must be able to be illuminated directly by a part of the optical beam 11 coming from the transmission unit 4 without undergoing complete masking due to at least one other receiver of the group. The different receivers ri, r2, are fixed on the facade of building 1, also slightly protruding from facade 3. One can find for example a receiver ri, r2 of the group per floor. The positioning of the receivers ri, r2 requires special care to avoid this complete masking. The receivers are relatively close to each other and close to the transmitter. A few meters separate them. We will highlight by referring to Figures 2A, 2B, 3A, 3B, the importance of the shape of the optical beam 11 with respect to the position of the receivers. FIGS. 2A, 2B show two transmission devices according to the invention with single transmitters emitting optical beams of different shapes. FIGS. 3A and 3B show the shadow 24 on the ground (or in a capture plane situated beyond the receivers relative to the transmitter), made by the receivers in each of the cases illustrated above. In fact each of the receivers ri, r2, r3 of the group illuminated directly by the transmitter E generates a volume of shadow vrl, vr2, vr3 opposite to the transmitter E. Each volume of shadow vrl, vr2, vr3 creates a shadow 24 on the ground.

In FIG. 2A, the emitter E is substantially punctual and the optical beam 11 is substantially a cone. The receptors ri, r2, r3 are also substantially punctual. The receivers ri, r2, r3 and the transmitter E are not aligned, they are offset with respect to each other. However, the receivers ri, r2, r3 are placed in the cone of illumination of the optical beam 11. With the configuration shown, the shadow volumes vrl, vr2, vr3 are substantially conical and the shadows 24 are relatively sharp but almost contiguous.

Thus, if we consider an emitter E placed at the top of a 10-storey building, that is to say placed about 30 meters from the ground, which emits an optical beam 11 having a possible capture surface of 50 centimeters in diameter at ground, a receiver ri of 1 centimeter in diameter, placed at six meters from the transmitter E, will make on the ground a shadow 24 of 5 centimeters in diameter (that is (30 x 0.01) / 6). The further the receivers are from the transmitter, the smaller the shadow they make on the ground. The other receptors r2, r3 in the group will therefore have a smaller shadow, that is to say that the possible capture surface will be greater. But in reality the emitter E is not a point source, it has a non-negligible surface, generally circular, and the optical beam 11 is not really a cone but a truncated cone. Reference is made to FIGS. 2B and 3B which illustrate this configuration. The relative positions of the receivers ri, r2, r3 and the transmitter E are unchanged. The shadow 24 on the ground formed by each receiver ri, r2, r3 is smaller than in the previous case. It is much less clear and therefore less annoying. In FIG. 3B, it can be noted, moreover, that the shadows 24 are more spaced apart from one another while the position of the receivers has not been modified between FIG. 2A and FIG. 2B. If in the case of FIG. 2A, there had been a total obstruction of one receiver with respect to another, in the case in Figure 2B, the total obstruction could have been removed.

From a geometrical point of view, this amounts to moving the emitter E away from the ground, that is to say placing it at the top I of the cone obtained by extending the truncated cone, without moving the receivers and therefore reducing the shadow 24 to soil provided by these receptors. A receiver r2 must not be completely in a volume of shadow vrl generated by another receiver ri closer to the transmitter E than it is, but as for the same height, on the one hand these volumes of shadow vrl, vr2, vr3 have a smaller section and on the other hand the section of the optical beam 11 is larger than in the previous case, a greater latitude is offered for the positioning of the receivers and consequently their mounting is simplified.

We will now describe in detail the reception block 5 with reference to FIG. 4. We have seen previously that the reception block 5 comprises a group of receivers ri, r2, each of. these receivers ri, r2, is electrically connected to a user device 13 which can have a function of processing the signal received by the corresponding receiver. The operating devices 13, subsequently called processing modules, are located inside the building 1, in each of the apartments 2 to be served. In Figure 4, only a receiver, for example ri, connected to its processing module 13 is shown. The receiver ri comprises a housing 14, preferably sealed, closed by a window 15 transparent facing the transmitter. Thus the window is exposed to a fraction 11.1 of the optical beam emitted by the transmitter. The window 15 is preferably curved, with a dome shape and it is treated anti-drip when it is placed outside. Thus precipitation, such as snow or rain, cannot accumulate on it. One can imagine placing a defrosting device (not visible) at the level of the dome. The housing 14 can contain a device 16 for converting the fraction 11.1 of the received optical beam into an electrical signal. This optical-electrical conversion device 16 can be produced, for example, by a PIN photodiode or an avalanche. In a variant, the fraction of optical beam received can be collected directly at one end of an optical fiber 21 'connecting the receiver to the use device 13 (signal processing module or other). This variant is illustrated in FIG. 5. The conversion device is no longer necessary and the end of the optical fiber 214 is in its place. The optical fiber 21 ′ penetrates inside the building in a similar manner to the connection 21 which will be described later. Focusing means 17 are provided for converging the fraction 11.1 of the optical beam on the conversion device 16 or on the end of the optical fiber. These focusing means 17 can be produced for example by one or more converging lenses. The focusing means 17 are placed between the window 15 and either the conversion device 16, ie the end of the optical fiber 21 '. It is advantageous to place between the window 15 and the focusing means 17 a chromatic filter 18 intended to absorb stray light not coming from the emitter. It may, for example, be solar rays, light from urban lighting or light signs located in the vicinity of the transmission device which is the subject of the invention. In FIG. 5, the focusing means and the chromatic filter are not shown so as not to overload the figure.

The housing 14 generally has the form of a tube, the window 15 is placed at one of its ends. The conversion device 16 or the end of the optical fiber are at the other end. The height h of the tube is chosen so as to protect either the conversion device 16 or the end of the optical fiber against direct sunlight or against ambient lighting. This height h separates the window 15 from the conversion device 16 or from the end of the optical fiber. For a case approximately 1 cm in diameter, the order of magnitude of the height h may be a few centimeters. It is preferable to line the inside of the housing 14 with an absorbent coating 19 so that the conversion device 16 or the end of the optical fiber receives only the fraction 11.1 of optical beam to which the receiver is exposed. and no ambient lighting for example. This absorbent coating 19 can be black paint. The housing 14 is integral with a support 20 intended to secure the facade 3 of the building. This support 20 gives the receiver ri a rigid fixing and a precise position on the facade of the building. The length of the support and its fixing point are determined in relation to that of the supports of the other receivers so as to avoid complete masking of one receiver by another receiver. With a divergent optical beam 11 and a sufficient emission surface, it can be envisaged that two receptor supports have substantially the same length and that, if the two receivers are sufficiently distant from each other, they are on the same vertical without one obstructing the other. The two receiver supports will be at the same distance from the wall of the building. On the other hand, with a single point transmitter, two receivers must not be on the same vertical because the closest to the transmitter completely masks the most distant. An electrical connection 21 connects the conversion device 16 to the processing module 13. This connection 21 can be contained in the support 20. It crosses the wall of the building to reach the processing module 13, the function of which can be to amplify and to adapt the signal received and converted by the conversion device 16 so that it becomes usable. It is conceivable that the support 20 crosses the wall. The processing module 13 is equipped with an interface 22 which makes it possible to connect it to the user device such as a television set or a personal computer for example (not shown) and supplying power to the processing module.

The housing 14 can have very small transverse dimensions, for example a diameter of the order of a centimeter.

Using the digital example mentioned above, that is to say with a capture surface corresponding to a diameter of 50 centimeters (i.e. the surface illuminated on the ground by the optical beam) and a receiver surface corresponding to a diameter of 1 cm, the attenuation is equal to:

201og (0.5 / 0.01) = 34 dB. Such a value is compatible with the powers transmitted (of the order of a few milliwatts) and with the sensitivity of current receivers (of the order of -40 dBm).

Such a transmission device does not require any wiring between the transmitter and the various receivers, which makes it particularly economical and easy to install in existing buildings. Another advantage which contributes to a low cost is that no processing of the signals is necessary between transmitters and receivers. In radio transmission systems, processing such as framing, over-screening, adding error correcting codes are often implemented.

Such transmission by atmospheric optical link, at low power, is neither disturbed nor disturbing with respect to radio signals. This is a significant advantage in an environment where radio signals are increasingly present. Currently the use of such signal transmission device is not subject to any authorization or license. The low powers involved do not affect the health of living things. With a transmission device according to the invention a large bandwidth (greater than one gigahertz) is available, consequently such a transmission device is particularly well suited to the broadcasting of a multiplex of UHF or VHF television signals or in intermediate band satellite in different apartments of a building.

Instead of being in a free space, the transmitter block and the receiver block could be confined in the same sheath. The optical beam would then be protected against obstacles, for example leaves of trees which could screen. No stray light could disturb the reception of signals. Such a sheath is shown schematically in Figure 1 with the reference 25. This sheath 25 can be located outside the building 1, also called building, or inside. This duct may already be present and have another function such as a mechanical ventilation duct or a technical column.

Instead of being directed substantially vertically along the facade of a building, the optical beam emitted by the transmission device object of the invention could be directed substantially horizontally, the transmitter and the various receivers of the group of receivers would be in solidarity, for example, with buildings or pavilions that follow one another in a street. Such a transmission device could of course be used indoors, along a ceiling for example, for distributing television signals, computer signals or the like in offices, hotel or hospital rooms. for example giving on either side of a corridor. Such a transmission device is particularly effective as a corporate network when data flows are important between a server connected to the transmitter and the user stations each connected to a receiver. Indoors, the boxes are not necessarily waterproof, the windows are not necessarily configured in dome and treated anti-drip. On the other hand, it is preferable to keep the chromatic filter and the absorbent coating.

One can imagine that, instead of carrying out point-to-multipoint transmission as described above, the transmission device which is the subject of the invention, realizes multipoint-to-point transmission. Such a transmission device can be used, for example, at the ceiling of a corridor, to collect information coming from smoke sensors (not shown) or any data flow from user stations to a central point. These sensors or user stations are placed in different rooms overlooking the corridor. This information contributes to the triggering of an alarm. Reference can be made to FIG. 5 which very schematically illustrates such a configuration. The reception block 50 comprises a single receiver R and the block 40 a group of transmitters el, e2. Each emitter el, e2 is intended to emit an optical beam, referenced respectively 41, 42 to the single receiver R of the reception block 50 and its radiation diagram is in cone (possibly truncated) or in cylinder as before. The different transmitters el, e2 are carefully placed with respect to the single receiver R so that a transmitter e2 distant from the receiver R is not completely masked from the receiver R by one or more transmitters el closer. The different transmitters el, e2 are not aligned, they are offset with respect to each other with respect to the receiver R, the latter being illuminated directly by each of the optical beams 41, 42. A transmitter el from the group of transmitters, close to the single R receiver, generates when it is directly illuminated by a more distant e2 transmitter, a volume of vel shadow on the side of the R receptor such that the R receptor is totally or partially excluded from the vel shadow volume.

The receiver R having to simultaneously receive the signals of all the transmitters el, e2, the separation of the different streams transmitted by the transmitters el, e2 to the receiver R will be carried out by any type of multiplexing well known in radio. A multiplexer (not shown) cooperates with each transmitter. The multiplexing can for example be a time multiplexing known by the abbreviation TDMA

(for time division multiple access or time division multiple access), a frequency multiplexing known by the English abbreviation FDMA (for frequency division multiple access or multiple access by frequency distribution), spread spectrum multiplexing known by the English abbreviation CDMA (code division multiple access for multiple access by code distribution), length separation multiplexing wave known by the English abbreviation DM (wavelength division multiplex for wavelength division multiplexing). All these techniques allow considerable information rates. The receiver will conventionally cooperate with a demultiplexer (not shown). From the structure point of view, the emitters el, e2 could have a structure comparable to that of the single emitter of FIG. 1. The window for closing the case will preferably be domed, dome-shaped, if it is placed outside and directed to the sky. It will advantageously be treated against gout. As for the receiver, it can be similar to that described in FIG. 4. Its box can be closed by a window which is not necessarily domed and treated with anti-drip treatment if the receiver R is directed towards the ground. The absorbent coating is desirable.

Although more complex to implement, the two transmission devices according to the invention which have just been described could be confused and make only one. The transmission device would then be bidirectional or dual. In this configuration illustrated in FIG. 6, each of the blocks 400, 500 would therefore have a transmission function and a reception function. Transmission takes place then between a first transceiver block 400 comprising a single transceiver ER and a second transceiver block 500 comprising a group of transceivers elrl, e2r2. The optical beam emitted by the transceiver ER carries the reference 11 while those emitted by the transceivers elrl, e2r2 respectively bear the references 11.1, 11.2. Each transceiver is thus formed of a transmitter (hatched) attached to a receiver (without hatching). This configuration will not be described further, which does not pose a problem to a person skilled in the art, the transmitters and receivers possibly being similar to those which have been described previously in FIGS. 1, 4 and 5. The same constraints on their positioning exist. Although several embodiments of the present invention have been represented and described in detail, it will be understood that various changes and modifications can be made, in particular at the level of the structure of the transmitters or receivers, without departing from the scope of the invention. .

Claims

1. Device for transmitting point-to-multipoint signals, comprising at least one transmission block (4, 40) and at least one reception block (5, 50), characterized in that the transmission block (4, 40 ) cooperates by atmospheric optical link with the reception block (5, 50), the transmission block (4, 40) comprising a single transmitter (E) or a group of transmitters (el, e2), the reception block (5, 50) comprising a group of receivers (ri, r2) or a single receiver (R) respectively, the single transmitter (E) or each of the transmitters (el, e2) of the group of transmitters being intended to illuminate directly each of the receptors (ri, r2) of the receptor group or the single receptor (R) respectively, without complete masking due to at least one other receptor (ri, r2) from the receptor group or to at least one other transmitter (el, e2) of the group of transmitters respectively.

2. Signal transmission device according to claim 1, characterized in that the transmission block (400) forms a first transmission-reception block and in that the reception block (500) forms a second block of transmission-reception, one of the blocks comprising a single transceiver (ER) and the other a group of transceivers (elrl, e2r2).

3. Transmission device according to one of claims 1 or 2, characterized in that a transmitter (el) of the group of transmitters, close to the single receiver (R), generates when illuminated by a more distant transmitter (e2), a shadow volume (vel) on the side of the single receiver (R), the single receiver (R) being totally or partially excluded from the shadow volume (vel).

4. Transmission device according to one of claims 1 to 3, characterized in that the receivers (ri, r2) of the group of receivers, illuminated by the single transmitter (E), generate a volume of shadow (vrl, vr2) opposite to the single transmitter (E), no receiver (ri, r2) being completely included in a shadow volume (vrl, vr2).

5. Transmission device according to one of claims 3 or 4, characterized in that the shadow volume (vel, ve2, vrl, vr2) is a cylinder or a possibly truncated cone.

6. Transmission device according to one of claims 1 to 5, characterized in that the single transmitter (E) or each transmitter (el, e2) of the group of transmitters comprises an emissive device (8) intended to emit a optical beam (11), this emissive device (8) being confined in a housing (9).

7. Transmission device according to claim 6, characterized in that the emissive device (8) is formed of a laser or light emitting diode.

8. Transmission device according to one of claims 6 or 7, characterized in that the single transmitter (E) or each transmitter (el, e2) of the group of transmitters includes an optic (10) to conform the optical beam (11) emitted by the emissive device (8).

9. Transmission device according to one of claims 6 to 8, characterized in that the housing (9) is closed by a transparent window (12).

10. Transmission device according to one of claims 1 to 9, characterized in that it comprises an encryption device (23) placed upstream of the single transmitter (E) or transmitters (el, e2) of the group of issuers.

11. Transmission device according to one of claims 1 to 10, characterized in that the single receiver (R) or each receiver (ri, r2) of the group of receivers comprises a conversion device (16) optical to electric or a end of an optical fiber, confined in a housing (14).

12. Transmission device according to claim 11, characterized in that the conversion device (16) is a PIN or avalanche photodiode.

13. Transmission device according to one of claims 11 or 12, characterized in that the housing (14) is closed by a transparent window

(15).

14. Transmission device according to claim 13, characterized in that a chromatic filter (18) is placed between the window (15) and either the conversion device (16) or the end of the optical fiber.

15. Transmission device according to one of claims 13 or 14, characterized in that focusing means (17) are placed between the window (15) and either the conversion device (16) or the end of the optical fiber.

16. Transmission device according to one of claims 11 to 15, characterized in that the interior of the housing (14) comprises a coating (19) intended to absorb ambient light penetrating into the housing.

17. Transmission device according to claim 13 to 16, characterized in that the distance (h) separating the window (15) either from the conversion device (16) or from the end of the optical fiber is adjusted so that the conversion device (16) or the end of the optical fiber, is out of reach of ambient lighting.

18. Transmission device according to one of claims 6 or 11, characterized in that at least one of the housings (9, 14) is sealed.

19. Transmission device according to one of claims 6 or 11, characterized in that at least one of the housings (9, 14) is intended to be fixed on a support such as a building wall.

20. Transmission device according to one of claims 9 or 13, characterized in that at least one of the windows (12, 15) is dome shaped.

21. Transmission device according to one of claims 9 or 13, characterized in that at least one of the windows (12, 15) is treated anti-drip.

22. Transmission device according to one of claims 1 to 21, characterized in that the single transmitter (E) or the transmitters (el, e2) of the group of transmitters transmit multiplex signals to the receivers (ri, r2 ) of the receptor group or the single receptor (R) respectively.

23. Transmission device according to one of claims 1 to 22, characterized in that the single receiver (R) or each receiver (ri, r2) of the group of receivers is electrically or optically connected to a user device (13).

24. Transmission device according to one of claims 1 to 23, characterized in that the transmission block (4) and the reception block (5) are housed in the same sheath (25).

25. Transmission device according to one of claims 1 to 24, characterized in that the transmission unit (4) and the reception unit (5) are integral with the same building (1).