EP3729688A1

EP3729688A1 - System for transmitting data by means of optical radiation and method associated therewith

Info

Publication number: EP3729688A1
Application number: EP18782796.9A
Authority: EP
Inventors: Alessandro Pasquali
Original assignee: Slux Sagl
Current assignee: Slux Sagl
Priority date: 2017-09-08
Filing date: 2018-09-10
Publication date: 2020-10-28
Also published as: WO2019048943A1; EP3729686A1

Abstract

A transmitter device (99) configured to transmit a signal through an optical radiation (108), said transmitter device (99) being characterized in that it comprises at least one modulator stage (101 ) having: - at least one photoemitter (100) configured to transmit the optical radiation (108); - an input (105) adapted to receive in use an electrical signal (s(t)) to be modulated, and - an output (107) transmitting, in use, towards the at least one photoemitter (100), one voltage or current driving signal (v7(t), i7(t)) for which said electrical signal (s(t)) represents a modulating signal, said driving signal (v7(t), i7(t)) being such that in use, the at least one photoemitter (100) transmits said optical radiation (108) with a radiation intensity (lr(t)) variable in accordance with said driving signal (v7(t), i7(t)), and wherein, between the input (105) and the output (107) there is at least one modulator stage (102; 103) configured for modulating, and/or modulating in use, according to at least one predefined modulation scheme comprising a frequency and/or phase modulation and an amplitude modulation.

Description

SYSTEM FOR TRANSMITTING DATA BY MEANS OF OPTICAL RADIATION AND METHOD ASSOCIATED THEREWITH

FIELD OF THE INVENTION

The present invention refers to the field of transmitting optical radiation and in detail regards a system of data transmission by means of optical radiation.

The present invention also regards a method of data transmission by means of optical radiation.

The present invention also regards data transmission and reception devices which exploit the abovementioned method.

PRIOR ART

It is known to use the electromagnetic spectrum in the radio frequency field for the transmission of electronic data, such as images or audio. The transmission of electronic data over radio channels requires the attribution of a specific channel for each transmission, which can only be shared with multiplexing techniques.

The great diffusion of wireless transmissions for the diffusion of electronic data in broadcast mode, in simulcast mode or with transmissions selectively dedicated towards a portion of the users - especially with the increase of volume of electronic data to be exchanged that has developed in recent years - has quickly saturated the previously-available radio channels, forcing the technology community to seek new radio resources, and thus frequency bands, with increasingly high frequency, up to reaching the microwave spectrum, in order to allow the transmission of electronic data over radio channel employing wide band. A typical example are the radio transmission backbones for mobile phone signals, DAB radios, high-definition television signals, which use bands of frequency in the microwave region to have a plurality of adjacent channels, each of which having sufficient bandwidth for the type of transmission required.

The massive use of wireless radio transmission for transmitting electronic data has raised several problems. A first problem is that radio transmissions often use radio channels which are overlapped or, in any case, interfering with the transmission spectra of adjacent channels, or with other sources of interference geographically allocated in a position different with respect to those of interest. The use of radio transmissions with very high frequencies is also subjected to considerable atmospheric absorption, the latter actually being substantially increasing with the increase of the frequency for the radio frequency spectrum; consequently, in order to transmit electronic data over wide band with very high frequencies, it is typically necessary to employ very high transmission powers.

Furthermore, the use of particularly high radio frequencies especially for close transmissions and for consumer applications is currently the subject of debate in relation to harmfulness to health.

The use of radio transmissions for transmitting electronic data is often limiting or entirely non-actuatable in specific environments in which the atmosphere is subject to risk of explosion. In particular, in the European Union, the applicant indicates that there is the directive AtEx 2014/34/UE for regulating apparatuses intended for use in zones with explosion risk.

The Applicant has also observed that the range of a radio transmission cannot be precisely predicted; in other words, a user who decides to receive a radio transmission of electronic data is able (or not able) to have, in his/her receiver, a sufficient radio power only on the basis, as a non-limiting example, of a change of antenna. The unpredictability of the boundaries of radio transmissions is such that a WiFi network that the user would like to be only intended for his/her own home can in fact be picked up even outside the home thereof. This leads to privacy problems, presently resolved by means of encryption of the flow of electronic data transmitted in the networks; nevertheless, there are daily examples of violation of the WiFi network encryption protocols.

Transmissions of electronic data which employ light radiation are known. Such optical transmissions use an AM modulation, which has the limit of a direct transmission. In other words, the AM modulation employed for optical transmission of electronic data is such that if an optically opaque object is interposed between a photoemitter and a photoreceiver that are modulated in AM with an input signal, the photoreceiver substantially is unable to reproduce, as an output, a copy of the signal placed as an input to the photoemitter. In other words, the AM modulation of a data signal is direct. The object of the present invention is to describe a system and a method for transmitting electronic data by means of optical radiation which contribute to reducing the impact and preferably resolving the above-described drawbacks. SUMMARY OF THE INVENTION

Transmitter device

According to a first aspect of the invention, a transmitter device (99) is implemented, configured to transmit a signal through an optical radiation (108), said transmitter device (99) being characterized in that it comprises at least one modulator stage (101 ) having:

- at least one photoemitter (100) configured to transmit the optical radiation (108);

- an input (105) adapted to receive in use an electrical signal (s(t)) to be modulated, and

- an output (107) transmitting, in use, towards the at least one photoemitter (100), one voltage or current driving signal (v7(t), i7(t)) for which said electrical signal (s(t)) represents a modulating signal, said driving signal (v7(t), i7(t)) being such that in use, the at least one photoemitter (100) transmits said optical radiation (108) with a radiation intensity (lr(t)) variable in accordance with said driving signal (v7(t), i7(t)), and wherein, between the input (105) and the output (107) there is at least one modulator stage (102; 103) configured for modulating, and/or modulating in use, according to at least one predefined modulation scheme comprising a frequency and/or phase modulation and an amplitude modulation.

According to a further non-limiting aspect, the at least one modulator stage (102, 103) is configured to produce a driving signal (v7(t), i7(t)) such as to cause the transmission of the optical radiation (108) modulated in frequency and amplitude according to the predefined modulation scheme and/or is configured to cause an optical radiation transmission (108) with a variable radiation intensity (lr(t)) according to the predefined modulation scheme.

According to a further non-limiting aspect, the predefined modulation scheme is a modulation scheme in which the modulation of the electrical signal (s(t)) is an amplitude modulation followed by a frequency modulation and/or a phase modulation, and/or is a frequency modulation and/or a phase modulation followed by an amplitude modulation. According to a further non-limiting aspect, the at least one modulator (102; 103) comprises an AM modulator (102) and an FM modulator and/or phase modulator (103), and/or comprises a modulator configured to perform an amplitude modulation and a frequency and/or phase modulation.

According to a further non-limiting aspect, said frequency and/or phase modulation follows the said amplitude modulation, and/or the FM and/or phase modulator (103) is placed downstream of said AM modulator (102).

According to a further non-limiting aspect, the predefined modulation scheme is a hybrid analog/numerical modulation scheme comprising at least one amplitude modulation and/or one phase or frequency modulation.

According to a further non-limiting aspect, the modulator stage (101 ) is a hybrid analog/numerical modulator stage, configured to perform at least one amplitude modulation and/or an at least partially numerical phase or frequency modulation.

According to a further non-limiting aspect, said photoemitter (100) comprises an LED and/or a SLED and/or an amplified spontaneous emission LED.

According to a further non-limiting aspect, said photoemitter (100) has a bandwidth greater than the band of the data signal (s(t)) and/or of the driving signal (v7(t), i7(t)), and/or has a bandwidth greater than the speed with which said data signal (s(t)) is received by the transmitter device (99).

According to a further non-limiting aspect, between said input (105) and said output (107) of said modulator stage (101 ), a cascade of a first AM modulator (102) and of a second FM modulator (103) is present, said FM modulator (103) being placed downstream of said AM modulator (102) and having an own output directly connected to the output (107) of said modulator stage (101 ), in which said AM modulator (102) has an input directly connected to said input (105) of said modulator stage and is directly powered by means of said electrical signal (s(t)) to be modulated, and in which said AM modulator (102) has an output on which it generates an intermediate signal (s2(t)) powered at input at said FM modulator (103).

Therefore, according to a further aspect of the invention is therefore realized a transmitter device (99) transmitting by means of optical radiation (108), said device being characterized in that it comprises at least one modulator stage (101 ) comprising: - an input (105) adapted to receive in use an electrical signal (s(t)) to be modulated, and

- an output (107) transmitting towards at least one photoemitter (100) a voltage or current driving signal (v7(t), i7(t)), for which said electrical signal (s(t)) represents a modulating signal, where said at least one photoemitter (100) transmits an optical radiation (108) with radiation intensity (lr(t)) variable in accordance with said driving signal (v7(t), i7(t)), and wherein, between said input and said output of said modulator stage (101 ), a cascade of a first AM modulator (102) and of a second FM modulator (103) is present, said FM modulator (103) being placed downstream of said AM modulator (102) and having an own output directly connected with the output (107) of said modulator stage (101 ), wherein said AM modulator (102) has an input directly connected to said input (105) of said modulator stage and is directly supplied by means of said electrical signal (s(t)) to be modulated and wherein said AM modulator (102) has an output on which it generates an intermediate signal (s2(t)) supplied as an input to said FM modulator (103).

According to a further non-limiting aspect, said intermediate signal (s2(t)) is directly supplied as an input to the FM modulator (103).

According to a further non-limiting aspect, the device comprises said at least one photoemitter (100), and said photoemitter is a photoemitter whose radiation curve as a function of said driving signal (v7(t), i7(t)) is not constant and/or wherein said photoemitter (100) is configured to emit and/or during use emits an optical radiation variable in accordance with said driving signal (v7(t), i7(t)).

According to a further non-limiting aspect, said photoemitter (100) has a pass band greater than the pass band of said driving signal (v7(t), i7(t)).

According to a further non-limiting aspect, said electrical signal (s(t)) is an audio signal and/or a base band signal.

According to a further non-limiting aspect, the photoemitter (100) is configured to emit an optical radiation (108) with radiation intensity (lr(t)) variable according to the said driving signal (v7(t), i7(t) ); said radiation comprising a first continuous part (I), independent from said driving signal and a second time variable part direct function of said driving signal (v7(t), i7(t)), wherein said time variable part direct function of said driving signal (v7(t), i7(t)) is lower in absolute value than the absolute value taken by said first continuous part. According to a further non-limiting aspect, a driving stage (104) is also present for said at least one photoemitter (100) interposed between said output (107) of said modulator stage (101 ) and said at least one photoemitter (100), wherein said driving stage (104) is configured to condition and/or process the driving signal (v7(t), i7(t)); optionally said driving stage (104) comprises means and/or a device for signal processing comprising at least one operating configuration such that said radiation intensity (lr(t)) variable in accordance with said driving signal comprises a first continuous part (I), independent of said driving signal and a second time variable part that is a direct function of said driving signal (v7(t), i7(t)), wherein said time variable part that is a direct function of said driving signal (v7(t), i7(t)) is lower in absolute value than the absolute value taken by said first continuous part.

According to a further non-limiting aspect, said driving stage (104) is configured to condition and/or process said driving signal (v7(t), i7(t)) and comprises processing means comprising at least one operating configuration in which it supplies said photoemitter (100) with an electrical signal having a first direct current or voltage signal component, of value independent of the value taken by said driving signal (v7(t), i7(t)), and a second time variable signal component, direct function of said driving signal, wherein said second time variable component is lower in absolute value than the absolute value taken by said first component and/or wherein the driving signal as an output from said driving stage (104) and supplied to said photoemitter (100) is always positive and/or greater than zero.

According to a further non-limiting aspect, said intermediate signal (s2(t)), powered at input to said FM modulator (103), is a signal adapted to cause a variation in the instantaneous frequency which said driving signal (v7(t)), i7(t)) takes on at the output of the FM modulator (103).

According to a further non-limiting aspect, said device comprises at least one stage of generating a reference frequency (109), in which said stage of generating a reference frequency (109) is electrically connected to a reference frequency input of said AM modulator (102) and generates at least one first reference frequency (fo) for said AM modulator.

Alternatively, according to a further non-limiting aspect, the stage of generating a reference frequency (109) is electrically connected to a reference frequency input of said AM modulator (102) by means of a first output (109f) thereof, and is further electrically connected to a reference frequency input of said FM modulator (103) by means of a second output (109s) thereof.

According to a further non-limiting aspect, said stage of generating a reference frequency (109) generates at least one first reference frequency (fO) for said AM modulator (102) and a second reference frequency (fc) for said FM modulator (103).

According to a further non-limiting aspect, the modulator stage (101 ) is configured to be supplied with an analogue signal and upstream of said input (105) of said modulator stage (101 ), a digital/analog converter is present.

According to a further non-limiting aspect, the transmitter device (99) is configured to transmit the optical radiation (108) according to at least a first and a second average power; said transmitter device (99) comprising a plurality of photoemitters (100) selectively simultaneously activable according to an automated activation algorithm, so that as the required average optical power increases, the number of photoemitters (100) simultaneously activated increases.

Method of modulation and transmission of the signal

According to a further aspect of the present invention, a method is described for modulating and transmitting a data signal (s(t)) by optical radiation (108), wherein the optical radiation (108) is capable of, and/or suitable for, being propagated also by reflection and/or indirect diffusion, said method being characterized in that it comprises:

- a modulation step of the data signal (s(t)) by at least one modulation and/or a predefined modulation scheme comprising an amplitude modulation and a frequency and/or phase modulation;

- a step for generating a driving signal (v7(t), i7(t)) as a result of the modulation of the data signal (s(t));

- a step of supplying the driving signal (v7(t), i7(t)) to at least one photoemitter (100);

- a step of adjusting the radiation intensity (lr(t)) of said optical radiation (108) emitted by at least one photoemitter (100) by means of and/or according to said driving signal (v7(t), i7(t));

According to a further non-limiting aspect, the modulation step comprises a hybrid, numerical and/or analog modulation step. According to a further non-limiting aspect, the modulation step is performed by means of a modulator configured to perform an amplitude modulation and a frequency and/or phase modulation.

According to a further non-limiting aspect, the modulation step is performed by means of a modulator comprising an AM modulator (102) and an FM and/or phase modulator (103).

According to a further non-limiting aspect, the AM modulator (102) and the phase modulator (103) are and/or comprise modules executing the modulation via and/or through software.

According to a further non-limiting aspect, the modulation step comprises:

- a first amplitude modulation step of said data signal (s(t)) preferably by means of an AM modulator (102), wherein following said amplitude modulation step an intermediate signal (s2(t)) is generated of which said data signal (s(t)) is a modulating signal;

- a second step of modulating the frequency of said intermediate signal (s2(t)) preferably by means of an FM modulator (103), wherein, following said frequency modulating step, a driving signal (v7(t), i7(t)) is generated, in particular voltage or current;

- a step of adjusting the radiation intensity (lr(t)) of said optical radiation (108) emitted by at least one photoemitter (100) by means of, and/or according to, said driving signal (v7(t), i7(t)).

According to a further aspect of the invention, the data signal (s(t)) is a base band signal and/or an audio signal, and is directly supplied to the input of said AM modulator (102).

According to a further aspect of the invention, said driving signal (v7(t), i7(t)) is directly generated following said frequency modulation step.

According to a further non-limiting aspect, in said step of adjusting the radiation intensity, the radiation intensity (lr(t)) of the optical radiation (108) is made variable according to said driving signal, and comprises a first continuous part (I), which is independent from said driving signal, and a second part which is variable over time as a direct function of said driving signal (v7(t), i7(t)).

According to a further non-limiting aspect, the method comprises a step of providing said driving signal (v7(t), i7(t)) to a photoemitter (100) whose radiation intensity curve as a function of said driving signal (v7(t), i7(t)) is not constant and/or wherein said photoemitter (100) is configured to emit and/or during use emits an optical radiation variable in accordance with said driving signal (v7(t), i7(t)).

According to a further non-limiting aspect, the step of adjusting the radiation intensity is a step of adjusting the luminous radiation intensity.

According to a further non-limiting aspect, the radiation intensity curve is a light intensity curve.

According to a further non-limiting aspect, the method comprises a step of simultaneous activation of a plurality of photoemitters (100) according to an algorithm or automated selective activation process according to an average power of required optical radiation, in which as such an average optical radiation power required increases, the number of photoemitters (100) simultaneously activated increases.

According to a further non-limiting aspect, the method comprises a step of defining at least a first average optical radiation transmission power and a second average optical radiation transmission power, in which the second power is greater than the first power; said method further comprising a selection step of a first plurality of photoemitters (100) simultaneously activated for the transmission of said optical radiation (108) when said first power is required, or a selection step of a second plurality of photoemitters (100 ) simultaneously activated for the transmission of said optical radiation (108) when said second power is required, said second plurality of photoemitters (100) being greater than the first plurality of photoemitters (100).

According to a further non-limiting aspect, the method comprises a step of providing said driving signal (v7(t), i7(t)) to a photoemitter (100) which has a pass band greater than the pass band of said driving signal (v7(t), i7(t)).

According to a further non-limiting aspect, said part which is variable over time as a direct function of said driving signal (v7(t), i7(t)) is less in absolute value than the absolute value taken on by said first continuous part (I).

According to a further non-limiting aspect, said method comprises a step of conditioning and/or processing of said driving signal (v7(t), i7(t)) in order to supply said photoemitter (100) with an electrical signal having a first direct current or voltage signal component, of value independent of the value taken by said driving signal (v7(t), i7(t)) and a second time variable signal component, direct function of said driving signal, wherein said second time variable component is lower in absolute value than the absolute value taken by said first component and/or wherein the driving signal as an output from said driving stage (104) and supplied to said photoemitter (100) is always positive and/or greater than zero.

According to a further non-limiting aspect, said method comprises a step of generating a first reference frequency (fO) for said amplitude modulation.

According to a further non-limiting aspect, said method comprises a step of generating a first reference frequency (fO) for said amplitude modulation and a second reference frequency (fc) for said frequency modulation.

According to a further non-limiting aspect, the step of generating said first reference frequency and/or said first and said second reference frequencies is executed by means of powering an AM modulator (102) and/or an AM modulator (102) and a FM modulator (103) with a reference frequency generator (109).

According to a further non-limiting aspect, a step of converting an input signal from the numerical domain to the analog domain is present, following which the signal in said analog domain represents said data signal (s(t)).

According to a further non-limiting aspect, a step of retrieving said data signal (s(t)) from a power grid is present.

According to a further non-limiting aspect, said data signal (s(t)) is filtered by an alternating component belonging to the network voltage present on said power grid.

Receiver device

According to a further aspect, a receiver device (199) for receiving optical radiation (108) is realized, said device being adapted to cooperate with a transmitter device (99) according to one or more of the preceding aspects, said receiver device (199) being adapted to output a replication (s'(t)) of an electrical data signal (s(t)) by means of a demodulation of the optical radiation (108) received according to the at least one predefined modulation scheme comprising a frequency modulation and an amplitude modulation.

According to a further non-limiting aspect, said receiver device (199) is characterized in that it comprises at least one demodulator stage (201 ) comprising: - an input (205) adapted to receive in use a voltage or current driving signal (v7'(t), i7'(t)) modulated and generated through a photoreceiver (200) operatively connected thereto and receiving in use an optical radiation (108) also reflected and/or rediffused, and

- an output (207) transmitting an output replication signal (s'(t)) for which said electrical signal (s(t)) represents a modulating signal,

and wherein, between said input and said output of said demodulator stage (201 ) there is at least one demodulator (202, 203) configured to demodulate according to a predefined modulation scheme comprising a frequency and/or phase modulation and an amplitude modulation.

According to a further non-limiting aspect, the demodulator is a demodulator (202, 203) configured to perform a hybrid numerical and analog demodulation.

According to a further non-limiting aspect, said receiver device (199) comprises at least one photoreceiver (200), optionally a plurality of photoreceivers (200) arranged according to a predefined spatial configuration and selectively activable according to the power of the optical radiation (108) received.

According to a further non-limiting aspect, said receiver device (199) is configured to increase the number of photoreceivers (200) simultaneously activated as the power of the received optical radiation increases, optionally when a predetermined power threshold is exceeded.

According to a further non-limiting aspect, the demodulator (202, 203) comprises and/or implements an FM demodulator (203) and an AM demodulator (202).

In particular, according to a further aspect, the demodulator (202, 203) comprises a cascade of a first FM demodulator (203) and a second AM demodulator (202) is present, said FM demodulator (203) being placed upstream of said AM demodulator (202), wherein said AM demodulator (202) has an input directly connected to the output of said FM demodulator (203).

According to a further non-limiting aspect, said input (205) of said demodulator stage (201 ) is directly supplied by means of said driving signal (v7(t), i7(t)) produced as an output from said photoreceiver (200).

According to a further non-limiting aspect, the receiver device (199) comprises a filtering stage placed downstream of said photoreceiver (200), said filtering stage being adapted to filter and/or separate and/or eliminate a continuous electrical signal component produced as an output from said photoreceiver (200) from a variable electrical signal component produced as an output from said photoreceiver, said filtering stage being adapted to create as an output said driving signal (v7(t), i7(t)).

According to a further non-limiting aspect, said FM demodulator (203) has an output on which it generates an intermediate signal (s2'(t)) supplied in input to said AM demodulator (202).

According to a further non-limiting aspect, said at least one photoreceiver (200) supplies a driving stage (204) for said demodulator stage (201 ), said driving stage being interposed between said input (205) of said demodulator stage (201 ) and said at least one photoreceiver (200), wherein said driving stage (204), in generating said driving signal (v7'(t), i7'(t)), is configured to identify, in the variable radiation intensity (lr(t)) received during use from said photoreceiver (200), a first continuous part (I) and a second time variable part that is a direct function of said driving signal, and to generate said driving signal (v7'(t), i7'(t)) as a time variable signal, direct function of said second variable part.

According to a further non-limiting aspect, said intermediate signal (s2'(t)) supplied in input to said AM demodulator (202) is a signal adapted to cause a variation of the instantaneous amplitude that said replication signal (s'(t)) assumes at the output of said AM demodulator (202).

According to a further non-limiting aspect, said device comprises at least one stage of generating a reference frequency (109), in which said stage of generating a reference frequency (109) is electrically connected to a reference frequency input of said AM demodulator (202) and generates at least one first reference frequency (fO) for said AM demodulator.

Alternatively, according to a further non-limiting aspect, said stage of generating a reference frequency (109) is electrically connected to a reference frequency input of said AM demodulator (202) by means of a first output (109f) thereof, and is further electrically connected to a reference frequency input of said FM demodulator (203) by means of a second output (109s) thereof.

According to a further non-limiting aspect, said stage of generating a reference frequency (109) generates at least one first reference frequency (fO) for said AM demodulator (202) and a second reference frequency (fc) for said FM demodulator (203). According to a further non-limiting aspect, said demodulator stage (201 ) produces, as an output, an analog signal.

Method for demodulation and reception of the signal

According to a further aspect of the present invention, a method is described for demodulation and reception of a data signal (s(t)) by means of optical radiation (108) even with indirect reflection, said method being characterized in that it comprises:

- a step of receiving, through at least one photoreceiver (200), an optical radiation (108) with its own radiation intensity (lr(t)) wherein through said at least one photoreceiver (200), a driving signal (v7(t), i7(t)) is generated, in particular in voltage or current, adapted to be transmitted and/or sent and/or demodulated to a demodulator (201 );

- a demodulation step of the driving signal (v7(t), i7(t)) for obtaining an output data signal, wherein the demodulation step is a demodulation step according to at least one predefined demodulation scheme comprising a frequency demodulation and an amplitude demodulation.

According to a further non-limiting aspect, the demodulation step comprises:

- a first step of frequency demodulation by means of a FM demodulator (203), wherein following said frequency modulation step, an intermediate signal (s2'(t)) is generated, starting from said voltage or current driving signal (v7(t), i7(t));

- a second step of amplitude demodulation of said intermediate signal (s2'(t)) by means of an AM demodulator (202), wherein following said amplitude demodulation step, a replication signal of the transmitted data signal (s(t)) is generated.

According to a further non-limiting aspect, the demodulation step comprises a hybrid numerical/analog demodulation step.

According to a further non-limiting aspect, the radiation intensity (lr(t)) of said optical radiation (108) comprises a first continuous part (I) and a second time variable part.

According to a further non-limiting aspect, the time-variable part comprises an amplitude and frequency modulation and/or is implemented by means of amplitude and frequency modulation, in particular an AM modulation and an FM modulation. According to a further non-limiting aspect, said radiation intensity is a light radiation intensity.

According to a further non-limiting aspect, said time variable part is lower in absolute value than the absolute value taken by said first continuous part (I).

According to a further non-limiting aspect, the method comprises a measurement step of a power of the received optical radiation, and a step of selective simultaneous activation of a plurality of photoreceivers (200) simultaneously used for receiving the optical radiation (108) in accordance with the measured power, in which as the power of the optical radiation increases, the number of simultaneously activated photoreceivers (200) increases.

According to a further non-limiting aspect, said method comprises a filtering step, in particular performed downstream of said photoreceiver (200), said filtering step being adapted to filter and/or separate and/or eliminate a continuous electrical signal component produced as an output from said photoreceiver (200) from a variable electrical signal component produced as an output from said photoreceiver, said filtering step being adapted to cause the creation of said driving signal (v7(t), i7(t)).

According to a further non-limiting aspect, said method comprises a step of generating a first reference frequency (fO) for said amplitude demodulation.

According to a further non-limiting aspect, said method comprises a step of generating a first reference frequency (fO) for said amplitude demodulation and a second reference frequency (fc) for said frequency demodulation.

According to a further non-limiting aspect, the step of generating said first reference frequency and/or said first and said second reference frequencies is executed by means of powering an AM demodulator (202) and/or an AM demodulator (202) and a FM demodulator (203) with a reference frequency generator (109).

According to a further non-limiting aspect, a step is present for converting a replication signal s'(t) from the analog domain to the numerical domain.

Power line

According to a further non-limiting aspect, a step of transmitting said replication signal (s'(t)) towards a power grid is present. According to a further non-limiting aspect, said data signal (s(t)) is filtered by an alternating component belonging to the network voltage present on said power grid.

Use

According to a further aspect, the use of a transmitter device (99) according to one or more of the present aspects is described, for the optical transmission of multimedia data signals, comprising audio and/or video data present even simultaneously, and/or for transmitting data signals received for streaming and/or burst type data signals.

Pointing device

According to a further aspect, is realized a reception system (300) comprising a receiver device (199) according to one or more of the preceding aspects, said system at its interior comprising an optically sensitive element (301 ) provided with a reception area (302) thereof and on which one or more photoreceivers (200) are installed, wherein said one or more photoreceivers (200) achieve a reception area (302) adapted to acquire at least one image in which a variation of radiation intensity (lr(t)) transmitted by a modulated and/or modulating photoemitter according to a predefined modulation scheme is present, said reception system (300) comprising means for selecting a part of the reception area (302) formed by the plurality of photoreceivers (200), configured to automatically select part of the reception area (302) in which a variation of radiation intensity (lr(t)) transmitted by a modulated photoemitter is present, and to cause the sending of a signal substantially corresponding to said variation of radiation intensity (lr(t)) towards said demodulator stage (201 ) of said receiver device.

According to a further non-limiting aspect, a reception system (300) is realized comprising a receiver device (199) of optical radiation (108), said device being adapted to cooperate with a transmitter device (99) according to one or more of the preceding aspects, said receiver device (199) being adapted to output a replication (s'(t)) of an electrical data signal (s(t)) by means of hybrid demodulation AM/FM, wherein said receiver device (199) comprises at least one demodulator stage (201 ) in turn comprising:

- an input adapted to receive in use a voltage or current driving signal (v7(t), i7(t)) modulated and generated through a photoreceiver (200) operatively connected thereto and receiving in use an optical radiation (108) also reflected and/or red iff used, and

and wherein, between said input and said output of said demodulator stage (201 ) there , is at least one demodulator (202, 203) configured to demodulate according to a predefined modulation scheme comprising a frequency and/or phase modulation and an amplitude modulation,

said system therein comprising an optically sensitive element (301 ) provided with a reception area (302) thereof and on which one or more photoreceivers (200) are installed, wherein said one or more photoreceivers (200) achieve a reception area (302) adapted to acquire at least one image in which a variation of radiation intensity (lr(t)) is present, transmitted from a modulated photoemitter, said reception system (300) comprising means for selecting a part of the reception area (302) formed by the plurality of photoreceivers (200), configured to automatically select part of the reception area 302 in which a variation of radiation intensity (lr(t)) is present, transmitted by a modulated photoemitter and to cause a signal substantially corresponding to said light variation (lr(t)) to be sent towards said demodulator stage (201 ) of said receiver device.

According to a further non-limiting aspect, a reception system (300) is realized comprising a receiver device (199) of optical radiation (108), said device being adapted to cooperate with a transmitter device (99) according to one or more of the preceding aspects, said receiver device (199) being adapted to output a replication (s'(t)) of an electrical data signal (s(t)) by means of hybrid demodulation AM/FM, wherein said receiver device (199) comprises at least one demodulator stage (201 ) comprising:

- an input (205) adapted to receive in use a voltage or current driving signal (v7(t), i7(t)) modulated and generated through a photoreceiver (200) connected thereto and receiving in use an optical radiation (108) also reflected, and

and wherein, between said input and said output of said demodulator stage (201 ) a cascade of a first FM demodulator (203) and a second AM demodulator (202) is present, said FM demodulator (203) being placed upstream of said AM demodulator (202), wherein said AM demodulator (202) has an input directly connected to the output of said FM demodulator (203),

According to a further aspect, the selection means are mechanical and are controlled by a data processing unit.

According to a further non-limiting aspect, the selection means are implemented by software.

According to a further non-limiting aspect of the invention, in both cases wherein the selection means are achieved via software or are of mechanical type, a predetermined algorithm analyzes the signal received by said one or more photoreceivers (200) of the reception area (302) in order to search a predetermined signal modulation scheme.

According to a further non-limiting aspect of the invention, the system (300) is further configured to execute a tracking algorithm through which said selection means are configured in order to find if the point of the reception area (302) or the point on the sub-portion of the reception area (302), in which said variation of radiation intensity (lr(t)) arrives, moves, and in order to perform an automatic tracking thereof, hence without requiring intervention by of the user.

According to a further non-limiting aspect of the invention, the search is without interruption of time continuity.

For greater clarity, the following definitions apply in the present description. According to the present invention, optical radiation means an optical radiation comprised in the infrared spectrum and/or in the ultraviolet spectrum and/or in the visible spectrum.

According to the present invention, by direct optical radiation or direct optical transmission, it is intended a transmission of an optical signal in which between a source or photoemitter and a destination or photoreceiver optically opaque obstacles are not interposed and reflections are not present. In other words, in the direct optical radiation or direct optical transmission, the transmission of the signals occurs with said source or photoemitter and the destination or photoreceiver being within the optical range, i.e., mutually visible.

For the purpose of a better understanding of the present invention, the following further definitions are applied:

- "Transparency" means a feature such that the material under examination may allow a radiation, which is incident thereon, to pass along a preferential direction, independently of the attenuation that such radiation undergoes in the passage through said material.

- "Infrared" means an electromagnetic radiation which has a wavelength approximately from 0.7 pm to 15 pm.

- "Visible" or "visible spectrum" means an electromagnetic radiation which has a wavelength approximately from 390 to 700 nm.

- "Ultraviolet" means an electromagnetic radiation which has a wavelength approximately from 400 nm to 10 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments and some aspects of the invention are described hereinafter with reference to the accompanying drawings, provided only for illustrative and, therefore, non-limiting purposes, in which:

- Figure 1 illustrates a block diagram of a modulator and of a demodulator of optical signals, operating with the hybrid AM modulation/FM according to the invention;

- Figure 2 illustrates a block diagram of a multi-channel receiver demodulating an optical signal with the hybrid AM/FM demodulation, object of the invention; - Figure 3 illustrates a block diagram of a reception device employing the demodulator, object of the invention; and

- Figure 4 illustrates a block diagram of a transmitter element and of a receiver element adapted to operate on an energy distribution power grid, in which the AM/FM modulation and demodulation, object of the invention, is used.

DETAILED DESCRIPTION OF THE INVENTION

With reference to figure 1 , reference numeral 99 indicates as a whole an optical transmitter device, which is configured to perform a particular method of transmitting electronic data transmitted starting from an electrical signal s(t) which can be for example, and not limited to a modulating signal of audio and/or video and/or audio and video type simultaneously or in any case multimedia, and can be transmitted by streaming - therefore with a substantially continuous frequency - or in bursts, or packets.

The transmitter device 99 is configured to transmit a signal by an optical radiation 108 and comprises at least one modulator stage 101 having:

- at least one photoemitter 100 configured to transmit the optical radiation 108;

- an input 105 adapted to receive, in use, the electrical signal s(t) to be modulated, and

- an output 107 transmitting, in use, towards the at least one photoemitter 100, one voltage or current driving signal v7(t), i7(t) for which said electrical signal s(t) represents a modulating signal, said driving signal v7(t), i7(t) being such that in use, the at least one photoemitter 100 transmits said optical radiation 108 with a radiation intensity lr(t) variable in accordance with the driving signal v7(t), i7(t). In particular, between the input 105 and the output 107 there is at least one modulator stage 102; 103 modulating according to at least one predefined modulation scheme comprising a frequency modulation and an amplitude modulation.

The modulator stage 102, 103 (or where it is made in multiple hardware and/or software portions of the modulator stages) is configured to produce a driving signal v7(t), i7(t) such as to cause the transmission of a frequency and amplitude modulated radiation according to the predefined modulation scheme and/or is configured to cause a transmission of the optical radiation 108 with a variable radiation intensity lr(t) according to the predefined modulation scheme. For example, the predefined modulation scheme can be a modulation scheme in which the modulation of the electrical signal s(t) is an amplitude modulation followed by a frequency modulation and/or a phase modulation, and/or is a frequency modulation and/or a phase modulation followed by a frequency modulation. In particular, the modulator 102; 103 can comprise an AM modulator 102 and/or an FM modulator and/or phase modulator 103, and/or comprises a modulator configured to perform an amplitude modulation and a frequency and/or phase modulation. The frequency and/or phase modulation 103 may follow the amplitude modulation 102, and/or the FM and/or phase modulator 103 is placed downstream of said AM modulator (102).

A further example is given by a modulator, or a set of modulators, hybrid analog/digital; in particular, the modulator, or the set of modulators, are configured to perform at least one amplitude modulation and/or an at least partially numerical phase or frequency modulation and/or the predefined modulation scheme is a hybrid analog/numerical modulation scheme comprising at least one amplitude modulation and/or a phase or frequency modulation.

More particularly, between the input and the output of the modulator stage 101 there is a cascade of a first AM modulator 102 and of a second FM modulator 103; in this case, the FM modulator 103 is placed downstream of said AM modulator 102 and has its own output directly connected to the output 107 of said modulator stage 101 . The AM modulator 102 has an input directly connected to the input 105 of the modulator stage and is directly powered by the electrical signal s(t) to be modulated and in which said AM modulator 102 has an output on which it generates an intermediate signal s2(t) supplied in input to the FM modulator 103.

The photoemitter 100 may be a photoemitter emitting an optical radiation in the infrared, ultraviolet or visible domain. The photoemitter 100 can be an LED or a laser or still be a superluminescent LED (SLED, SLD) or amplified spontaneous emission. In a particular embodiment, the photoemitter 100 can be a broadband and/or high speed LED, capable of allowing data transmissions at speeds higher than Gbps. This LED can in particular be an LED doped with gallium nitride. Conveniently, the bandwidth of the photoemitter 100 is greater than the bandwidth of the signal to be transmitted, in order to avoid inappropriate filtering effects. In a particular configuration, the transmitter device 99 comprises a plurality of photoemitters 100 configured according to a predefined spatial orientation scheme and preferably connected in parallel. In this configuration, the transmitter is designed and configured to transmit the optical radiation according to at least a first and a second average optical power, in which in particular the second optical power is greater than the first optical power. This adjustment of the average optical power can be performed by the user according to a command that can also be remotely controlled. According to an automatic activation algorithm, and therefore without the need for direct intervention by the user, the photoemitters 100 are selectively simultaneously activated so that, as the required average optical power increases, the number of photoemitters 100 simultaneously activated increases.

In a non-limiting embodiment, the signal s(t) is a base band signal; the audio analog signal s(t), before being transmitted to a photoemitter 100 which preferably though not in a limiting manner comprises an LED diode, is subjected during transmission to a modulation step performed by a modulator stage 101 of analog and hybrid type. The transmission module 99 implemented with the transmitter device 99 and which also comprises the photoemitter 100 comprises a plurality of modulators in series adapted to perform said hybrid modulation, and in detail, starting from its input 105 on which it receives the audio analog signal s(t), it first comprises an AM modulator 102 directly supplied from the aforesaid input 105, and a FM modulator 103 placed in series with the AM modulator 102 and directly supplied therefrom. The output 107 of the modulator stage 101 supplies an input of a driver stage 104 for said photoemitter 100.

In particular, the output 107 of the modulator stage 101 produces a voltage signal v7(t) or current signal i7(t) which is supplied through the driver 104 to the photoemitter 100 and which attains a driving signal. In particular if the photoemitter 100 is made from one or more LED diodes 100, it was found that the brightness of the diode is proportional to the voltage or current provided thereto as input. Preferably, the LED diode or in general the photoemitters 100 must be photoemitters which, if emitting an optical radiation in the visible domain, have a light intensity curve as a function of the voltage or current, in particular of the driving signal, supplied to them in input that does not have to be constant. This means that the light intensity curve, and more generally the intensity of optical radiation, varies as a function of the voltage or current supplied to the photoemitter. More preferably, but not limiting, the light intensity curve of the voltage or current is substantially of linear type.

The voltage signal v7(t) or the current signal i7(t) produced as an output 107 from the modulator stage 101 are analog signals correlated with the audio input signal s(t) and, when supplied to the photoemitter 100, they produce a variation of the brightness lr(t) of the optical beam 108 transmitted by the photoemitter proportional to the variation of voltage or current, respectively of the voltage signal v7(t) or of the current signal i7(t).

More particularly, once the input signal s(t) has been given to the AM modulator 102, such AM modulator 102 produces as an output an intermediate signal s2(t) that assumes the following form:

s₂(t) = s(t)sin(27r/ot)

where fo is the carrier frequency of the AM modulation.

The FM modulator 103 attains a frequency modulation, such that its instantaneous frequency assumes the form:

wherein fc is the carrier frequency of the FM modulation.

The output signal v7(t) or i7(t) will therefore have the following form

The two carrier frequencies fo and fc respectively of the AM or FM modulation are actual predetermined values, which nevertheless can be modified by the user according to a technique that is known and hence not described herein. Conveniently in the device, object of the invention, a frequency generator 109 is also present, provided with a first output 109f supplying the AM modulator and a second output 109s supplying the FM modulator respectively with a sinusoidal frequency signal fo and with a cosinusoidal frequency signal fc. Such solution should be intended as non-limiting, since it is possible to make the device, object of the invention, in a manner such that the frequency generator 109 has a single output directed towards both the AM modulator 102 and the FM modulator 103, then giving the latter the task of generating the cosinusoidal signal with frequency fc based on the sinusoidal signal with frequency fo generated by the frequency generator 109. The Applicant has found that the carrier frequency fc can also be zero. In such case, the hybrid modulation takes the form of a direct modulation. In addition, the Applicant has observed that the carrier frequency fc can also be greater than 1 MHz; in particular when photoemitter is an LED diode, the carrier frequency fc for the FM modulator can as a non-limiting example be up to 10 MHz. Preferably though not limiting, the carrier frequency fc for the FM modulator 103 is greater than the carrier frequency fo for the AM modulator.

In order to avoid significant distortions of the optical beam 108 in terms of brightness variation lr(t) or more in general of optical radiation intensity, the Applicant has observed that the band occupied by the brightness variation signal lr(t), and even more so the voltage signal v7(t) or current signal i7(t) supplied to the photoemitter 100, must not exceed its maximum pass band. In other words, the band occupied by the driving signal must be lower than the maximum pass band of the photoemitter 100 in order to not have distortions. The absence of distortions is important, especially since the signal placed as an input to the said signal modulator is an audio signal.

The Applicant has observed that the data signal in input can also be a numerical signal. In such case, the Applicant has conceived a further embodiment which differs from the preceding embodiment in that it comprises an digital/analog converter 106 stage, placed between the input of the device and the input 105 of the modulator stage 101 , which provides to transform the input data signal into an analog signal suitably adapted in order to be analogically modulated through the modulators AM 102 and FM 103, as previously described. Since the digital/analog converter 106 relates to the further embodiment and therefore with respect to the first embodiment it is optional, in figure 1 such a digital/analog converter 106 is shown with a broken line.

The Applicant has observed that the optical beam 108 obtained by means of the hybrid modulation as previously described is particularly adapted for being received even over indirect paths, i.e. by means of reflection or refraction caused by surfaces that are even micrometrically incoherent, such as a wall or the like. In figure 1 , there are two reflections but such number must not be intended as being limiting.

In particular, the optical beam 108, as illustrated in figure 1 , is transmitted with one or more reflections 140, 141 as a non-limiting example over one or more walls M, towards a receiver device 199, which comprises at least one photoreceiver 200 which receives the reflected optical beam 108 and which transmits a voltage or current signal v7'(t) or i7'(t) - in accordance with the intensity as a function of time of said optical beam 108 - towards a demodulator stage 201 , which performs a step of hybrid demodulation of the received voltage or current signal. The voltage or current signal v7'(t), i7'(t) represents a driving signal for the demodulator 201.

The demodulator 201 is configured to perform a demodulation according to a predefined demodulation scheme which comprises an amplitude demodulation and a frequency and/or phase demodulation, and may be and/or comprise a hybrid analog/numeric demodulation.

In a particular embodiment, the demodulator 201 comprises a cascade of an

FM demodulator 203 and of an AM demodulator 202, wherein the input of the Am demodulator 202 is directly supplied by the output of the FM demodulator 203. The FM demodulator 203 has an input 205 on which said voltage or current signal v7'(t) or i7'(t) is supplied. As in the case of the transmission side, between the FM demodulator and the photoreceiver 200 a driver can be present that is adapted to generate the voltage or current signal v7'(t) or i7'(t) for the demodulator stage, termed "driving signal" for the purposes of the present invention for the demodulator stage, in a manner such to separate the first continuous component I from the second variable component of the optical radiation, and only send the variable component to the input of the demodulator stage.

As in the case of the modulation side, also the receiver device 199 comprises a frequency generator 109, provided with a first output 109f supplying the AM demodulator and a second output 109s supplying the FM demodulator respectively with a sinusoidal frequency signal fo and with a cosinusoidal frequency signal fc. Such solution should be intended as non-limiting, since it is possible to make the device, object of the invention, in a manner such that the frequency generator 109 has a single output directed towards both the AM demodulator 202 and the FM demodulator 203, then giving the latter the task of generating the frequency the cosinusoidal signal with frequency fc based on the sinusoidal signal with frequency fo generated by the frequency generator 109. The Applicant has found that the carrier frequency fc can also be zero. In such case, the hybrid demodulation takes on the form of a direct demodulation. The demodulator stage 201 , as with the modulator stage 101 , can be made with hardware or with mixed hardware-software structure, or as SDR, hence only software, without such difference constituting a limitation for the purpose of the present invention. The receiver device 199 then produces, on its output 199u, a replication s'(t) of the input signal s(t) at the transmitter side.

In particular, the voltage or current signal v7'(t) or i7'(t) generated by the photoreceiver is first transmitted towards the FM demodulator 203 which extracts a copy s2'(t) of the intermediate signal s2(t) that is supplied to the input of the AM demodulator 202, which performs the actual conversion towards the replication signal s'(t) of the input signal s(t) at the transmitter side.

Advantageously, the Applicant has observed that the hybrid modulation and demodulation performed as described above are particularly adapted for being used for transmitting an audio analog data signal, even with transmission by means of reflections, since it has been proven that the replication s'(t) of the audio analog input signal s(t) at the transmitter side is received without audible distortions, or in any case without distortions that are capable of significantly worsening the quality of the signal.

A further embodiment of the receiver 199, object of the invention, is advantageously described in the following portion of the text. Such embodiment of the receiver 199 is conceived so as to allow the reception of optical signals 108 over multiple channels simultaneously, hence realizing a multichannel receiver for optical signals.

The multi-channel optical receiver described below and shown in figure 2 comprises a plurality of demodulator stages 201 arranged in parallel and having the same structure as the single-channel receiver 199 described above, to which reference shall be made, but also integrates a filtering stage 210. This filtering stage is positioned between the photoreceiver 200 and the demodulator stage 201 , and is designed to cause the transmission of only part of the voltage v7'(t) or current i7'(t) signal at the output of the photoreceiver, with a subdivision by frequency bands.

In particular, the Applicant has observed that conveniently the filtering stage

210 can integrate one or more band-pass filters 211 each centered on its own central frequency ideally coinciding with each of the carrier frequencies fc of the FM modulator 103. In this way, the filtering stage performs a procedure for selecting which sub-parts of the spectrum to transmit to the various demodulator stages 201 , such that each of them can decode its own channel independently of the remaining demodulator stages 201 . The filtering stage 210 can be realized in hardware, partially software or totally software.

Advantageously the Applicant has verified that the multichannel receiver described herein is particularly useful for the reception of data signals of audio type, since it allows distinguishing, as a non-limiting example, a left channel from a right channel, thus realizing a multichannel receiver adapted to be installed on a headset/earphone for the audio signal reception by means of optical transmission.

Such receiver device 199 is well-integrated in a transmission system that comprises a plurality of transmitters as described above, in which each i-th transmitter has its own FM modulator 103 operating with a carrier frequency f_Ci different from the others, and in which the receiver 199 comprises a filtering stage 210 adapted such that it can be tuned or in any case divide the N carrier frequencies fc,, i=1 ... N of each of the transmitters towards one or more of the demodulators FM 203.

As an alternative to the above-proposed solution, the multichannel receiver described herein can be provided with a filtering stage 210 installed between the FM demodulator 203 and the FM demodulator 202, operating under the same principle as the preceding case. Nevertheless, in such case, the differentiation of the audio channels will only be given by the distinction of the carrier frequencies fo of the various modulators AM 103 on the transmitter side, hence taking care to maintain constant the carrier frequency fc of the modulators FM 103 of the system.

The filtering stage 210 may comprise selection means adapted to allow the manual selection of sub-parts, preferably one sub-part, of the various carrier frequencies fc, so as to select for example only one channel. Such solution is particularly advantageous for the applications of multilingual signal diffusion, since each i-th transmitter can employ its own carrier frequency fc, i=1 ,N in the system in order to carry an audio signal, each in one language thereof, allowing the user to select the channel of interest by means of known selection means.

The method which is therefore carried out by the present invention, on the transmitter side, comprises a step for feeding an analog signal s(t) to a modulator stage 101 , which performs a modulation step of the data signal (s(t)) by at least one modulation and/or a predefined modulation scheme comprising an amplitude modulation and a frequency and/or phase modulation; a step for generating a driving signal v7(t), i7(t) as a result of modulation of the data signal s(t); a step of supplying the driving signal (v7(t), i7(t)) to at least one photoemitter 100; and an adjustment step of the radiation intensity lr(t) of the optical radiation 108 emitted by at least one photoemitter 100 by means of said driving signal v7(t), i7(t). This modulation, in a particular embodiment, can be an optical modulation. The propagation of the optical radiation is such that the latter is also admissible in an indirect way, by reflection and/or diffusion or scattering.

In particular, the modulator 101 performs a step of modulation first comprising a step of amplitude modulation of said analog signal s(t) in order to produce, as an output from an AM modulator 102 thereof, an amplitude-modulated intermediate signal s2(t) and further comprising a step of supplying the intermediate signal s2(t) to a FM modulator 103 in order to obtain, as an output, a voltage or current signal v7(t), i7(t) supplied as an input to a photoemitter 100, wherein the step of supplying the voltage or current signal v7(t), i7(t) to said photoemitter 100 generates a variation of optical radiation intensity lr(t) proportional to the voltage or current signal v7(t), i7(t).

Likewise, on the receiver side, the method comprises a reception step of an optical beam 108 carrying electronic data through the modulation of the data signal s(t) according to a predetermined modulation, wherein in the receiving step at least one photoreceiver 200 generates a voltage or current driving signal v7'(t), i7'(t) of amplitude proportional to the light intensity lr(t) received, and in which there is a demodulation step performed by at least one demodulator stage 201 of a receiver 199.

In particular, demodulation is a demodulation performed in a demodulation step of the driving signal (v7(t), i7(t)) for obtaining an output data signal, wherein the demodulation step is a demodulation step according to at least one predefined demodulation scheme comprising a frequency demodulation and an amplitude demodulation.

In particular, in the step of receiving at least one photoreceiver 200 it generates a voltage or current driving signal v7'(t), i7'(t) of amplitude proportional to the received light intensity lr(t), and wherein there is a step of demodulation performed by at least one demodulator stage 201 of a receiver 199 in which the at least one demodulator stage 201 first of all performs a frequency demodulation of said voltage or current driving signal v7'(t), i7'(t) generated by the at least one photoreceiver in order to produce an intermediate signal s2'(t) and wherein said method comprises a step of supplying said intermediate signal s2'(t) to the input of an amplitude demodulator 102 of said receiver 199, which performs an amplitude demodulation in order to extract an analog data signal s(t) from said intermediate signal s2'(t).

The Applicant has devised a particular embodiment of the receiver device 199, in which there is a plurality of photoreceivers 200 connected to each other and configured to receive the optical radiation 108 modulated according to the predefined modulation scheme. The plurality of photoreceivers 200 is selectively activable, preferably in a process or through an algorithm controlled through a data processing unit, and in particular according to a predetermined and preferably automatically performed activation algorithm, such that, upon exceeding a predetermined received optical power threshold (non-zero threshold, for example equal to or higher than the dark current), as the optical power received increases, an increasing number of photoreceivers 200 is used to produce the voltage or current driving signal v7'(t), i7(t). Thanks to this aspect, there is a greater reception efficiency both with extremely low optical powers and with extremely high optical powers, respectively compensating the electrical noise and any saturation phenomena.

More in detail, since the signal being transmitted is modulated by means of the superimposition of a constant component and a variable component, also the output of the photoreceiver 200 generates an electrical signal comprising a first constant voltage or current component and a second voltage or current component variable in accordance with the modulation performed, and only the latter component is effective for the decoding of the signal s'(t). For such reason, a filtering stage can be present, downstream of the photoreceiver 200, which separates and/or eliminates and/or filters the constant component of said voltage or current signal, and produces as an output the voltage or current driving signal v7'(t), i7'(t) based on the single variable voltage or current component.

With reference to the embodiment specifically described herein, both in transmission and in the receiving step, the frequency and amplitude modulations respectively can be sequential, and in particular: during transmission, the frequency modulation follows the amplitude modulation, while in the receiving step the amplitude demodulation follows the frequency demodulation. During transmission, the intermediate signal s2(t) contributes to defining an instantaneous frequency of a signal which will be the object of a frequency modulation by means of the aforesaid intermediate signal s2(t).

The Applicant has observed that, in the optical domain, the hybrid modulation formed by a cascade of a FM modulation of a signal previously modulated in AM renders the receivers particularly sensitive to detecting the presence of a power signal, even a very weak one.

The Applicant has conceived a reception system 300, comprising a receiver 199 according to what described above, which is shown in figure 3. Such a reception system 300 therein integrates an optically sensitive element 301 provided with its own reception area 302 and on which one or more photoreceivers 200 are installed. In this case, although this solution does not have to be considered as a limitation, preferably the photoreceivers 200 are of the CCD type, and form a matrix in the reception area 302. The reception area 302 therefore has relative size and can be adapted to acquire an image, as well as the variation of optical radiation intensity lr(t) transmitted by a modulated photoemitter. The assembly of the photoreceivers can therefore achieve a reception area 302 of a camera, of a video camera or of binoculars.

The receiver 199 in this case comprises means for selecting a part of the reception area 302 formed by the plurality of photoreceivers 200. Said selection means 303 are in particular configured to select part of the reception area 302 in which there is a variation of intensity of optical radiation lr(t) transmitted by a modulated photoemitter.

In a first non-limiting embodiment, the selection means are mechanical, e.g. attained through micro-arms, while in a second non-limiting embodiment the selection means are attained via software; in both cases, a predetermined algorithm analyzes the signal received by the photoreceivers 200 of the reception area 302 in order to search a predetermined signal modulation scheme. The search can occur over all the photoreceivers 200 of the area or over a part thereof by means of the selection means. When such selection means are moved, electronically or mechanically, on the sub-portion of the area in which a signal is received with variation of optical radiation intensity lr(t) transmitted by a modulated photoemitter, the selection means perform a spatial filtering over the reception area 302 which allows more greatly isolating the variation of optical radiation intensity lr(t) transmitted by said modulated photoemitter from the optical noise otherwise captured on the remaining portion of the reception area 302; the variation of optical radiation intensity lr(t) transmitted by the photoemitter, which is an indication of an optical beam 108 modulated with the previously-described hybrid modulation, through the photoreceiver or the photoreceivers 200 of the abovementioned sub- portion is transformed into an electrical voltage or current signal v7'(t), i7'(t) which is sent as an input to a receiver as described above, and in particular to the demodulator thereof, in a manner such to subsequently proceed with an extraction of the replication of the signal s(t) of interest.

According to an aspect of the invention, in the system 300 a tracking algorithm is also performed through which the selection means are configured to search, preferably without temporal interruption, whether the point of the reception area 302 or on the sub-section of the reception area 302 in which said change in intensity of optical radiation lr(t) according to the predefined modulation scheme, in particular according to the predefined modulation scheme as described in the previous description portion and in the previously mentioned aspects, moves, and to perform an automatic tracking, without the need for user intervention.

The Applicant has in particular observed that when such system 300 is installed on a camera, on a video camera or on binoculars - in particular if provided with enlarging or telephoto lenses - it can easily happen that during the pointing operation, especially if manual, the sought-after point can be subjected to movements over the reception area 302 due to accidental movements of the pointing axis of the lens or objective. Advantageously, the Applicant has realized that by implementing the tracking algorithm on the video camera, camera or binoculars integrating the system 300, it is advantageously possible to transform the aforesaid camera, video camera or binoculars into a reception device for receiving signals transmitted over an optical channel and modulated by modulation comprising an amplitude modulation and a frequency modulation, in particular a hybrid amplitude modulation and/or a hybrid numerical/analog modulation, and in particular a hybrid FM and AM modulation, which, even if able to capture an image in the visible spectrum, is also simultaneously able to receive a signal transmitted by an optical source present in said image, even if the source itself is - to the human eye - barely visible and/or even if the modulation of the brightness of the source might appear non-existent to the human eye. For this particular aspect, the Applicant has observed from its tests that an audio signal can be received even at a considerable distance, up to several kilometers, above all in non-foggy or cloudy weather conditions, through the light emission of one or more LEDs of conventional type, which, even if modulated, to the human eye appear to entirely lack light intensity variation.

In other words, a data signal and in particular an audio signal can be modulated on a photoemitter 100 or on multiple photoemitters 100 adapted for example to illuminate an environment, with a relative modulation of very low light intensity, even lower than 1/1000, without losing data and therefore without the human eye being able to perceive such modulation, not only due to its speed but also through the very limited variation of the amplitude between modulated or non-modulated signal peaks.

In particular the Applicant has observed that it is convenient to allow the photoemitter 100 - in the absence of modulation - to have a constant non-zero light intensity I, on which a hybrid modulated signal is superimposed. In other words, the optical, in particular light, radiation intensity lr(t) is given by two components according to the following formula:

/r(t) = I + kV₇(t)

where the first component I is the constant and/or continuous component and the second component kV₇(t) is that which follows the abovementioned law

Acos [(27r _c + 277-/^2 (t)) t]- In order to avoid zero transitions, in particular if the photoemitter is an LED diode, and in particular to make the aforementioned diode work in a linearity zone so as to prevent modulation distortions, the portion kV₇(t) should preferably but non limited have an absolute value that is always kept lower than the absolute value of the continuous component I. This task is advantageously carried out by the driver stage 104. Therefore, the driver stage 104 processes and/or conditions the driving signal v7(t), i7(t), feeding at the input to the photoemitter 100 an electrical signal comprising a first component of a voltage or direct current signal, of a value independent of the value assumed by the driving signal v7(t), i7(t) and a second signal component variable over time, direct function of the driving signal, in which the second component variable over time is lower by absolute value than the absolute value assumed by the first component; in other words, the output signal from the driver stage 104 and supplied to said photoemitter 100 is always positive and/or greater than zero.

The Applicant has also considered that operating the driver stage 104 in accordance with that specified above allows preventing the risk that, in the absence of signal s(t), the photoemitter 100 is driven with a zero or in any case overly low voltage such that it cannot be turned on or in any case not visibly turned on.

Through the hybrid modulation described herein, the Applicant has surprisingly found that even if the photoemitter 100 present or made to work in a region where the characteristic of optical radiation power or intensity as a function of the driving signal is non-linear, it is possible to obtain very accurate reproductions of the audio signal s'(t) when received.

The Applicant has also observed that through the device, object of the present invention, it is possible to obtain a conveyed wave transmission system 400, comprising a transmitter element 401 and a receiver element 402, each of which connectable to the home power grid at an input 403 thereof. The transmitter element 401 comprises an output 404 in order to supply a photoemitter 100 while the receiver element integrates at least one photoreceiver 200.

The transmitter element 401 as in figure 4 integrates, at its interior, one or more modulator stages 101 with the previously-described characteristics, and also integrates at its interior an isolator stage 405, comprising at least one transformer therein adapted to separate the network voltage section from the rest of the circuitry, especially from the modulator stage 101 , whose characteristics are those described above (reference being made thereto). In the same manner, also the receiver element 402 comprises an isolator stage 405 therein in order to separate the demodulator stage 201 from the network voltage. During use, the user can inject, on the home network, a base band signal s(t). This signal is diffused up to the transmitter element 401 , which modulates it through the aforementioned modulator stage 101 with a hybrid type modulation as previously described and transmits it on its output 404 to supply a photoemitter 100 with such modulation. In another side of the room, on the contrary, the receiver element 402 receives the hybrid modulated optical signal as previously described and, with the same procedure, demodulates it and reconverts it into a replication s'(t). The Applicant has verified that the conveyed wave system 400 as described above allows diffusing, through light signals, or in any case in the radiation domains previously described, data signals s(t) which preferably though not in a limiting manner integrate audio signals, also over electrical lines that are decoupled from each other, with an optical transmission which also ensures that the aforesaid two electrical lines decoupled from each other are in perfect galvanic isolation with respect to each other.

The Applicant has also verified that, in a particular embodiment, the transmitter element 401 can also integrate the photoemitter 100, thus realizing a photoemitter with integrated hybrid modulator, hence a kind of intelligent lamp capable of electronically processing a data signal s(t) superimposed on the network signal and causing the transmission thereof via light by means of a hybrid modulation, as previously described.

The Applicant has also observed that it is convenient to introduce a filtering stage of the network frequency 406, which allows isolating the component of the data signal s(t) from the 50 Hz or 60 Hz signal typical of the network frequency. Advantageously, this contributes to preventing the network frequency component, which does not represent a useful signal, from entering into the modulation of the optical radiation intensity lr(t) transmitted by the photoemitter 100.

The Applicant has observed that the advantages of the invention, especially in terms of indirect receivability, through the hybrid modulation and demodulation as described above are attained independently from the type of photoemitter 100, and in particular independent of whether the photoemitter is coherent - with "coherent" it being intended a monochromatic photoemitter such as a LASER - or incoherent, with "incoherent" it being intended a photoemitter that emits a polychromatic optical beam. The Applicant in any case has observed that the use of coherent photoemitters improves the reception performances with respect to what could be obtained with an incoherent photoemitter.

Parts of the process described in the present invention can be - when possible - attained by means of a data processing unit, technically substitutable with one or more computers conceived for performing a software or firmware program portion that is predefined and loaded on a non-transient memory medium. Such software program can be written in any one programming language of known type. The computers, if there are two or more of these, can be connected together by means of a data connection such that their calculation powers are shared in any manner; the same computers can therefore be installed in positions that are even geographically different from each other.

The data processing unit can be a processor of general purpose type, especially configured through said software or firmware program in order to perform one or more parts of the method identified in the present invention, or be an ASIC or dedicated processor, specifically programmed for performing at least part of the operations of the method or process of the present invention.

It is finally apparent that additions, modifications or variations obvious to a person skilled in the art may apply to the object of the present invention, without thereby departing from the scope of protection provided by the accompanying claims.

Claims

1. A transmitter device (99) configured to transmit a signal through an optical radiation (108), said transmitter device (99) being characterized in that it comprises at least one modulator stage (101 ) having:

2. Device according to claim 1 , wherein the at least one modulator stage (102, 103) is configured to produce a driving signal (v7(t), i7(t)) such as to cause the transmission of the optical radiation (108) modulated in frequency and amplitude according to the predefined modulation scheme and/or is configured to cause an optical radiation transmission (108) with a variable radiation intensity (lr(t)) according to the predefined modulation scheme.

3. Device according to claim 1 or claim 2, wherein:

the predefined modulation scheme is a hybrid analog/numerical modulation scheme comprising at least one amplitude modulation and/or one phase or frequency modulation,

and/or wherein the modulator stage (101 ) is a hybrid analog/numerical modulator stage, configured to perform at least one amplitude modulation and/or an at least partially numerical phase or frequency modulation.

4. Device according to one or more of the preceding claims, wherein between said input (105) and said output (107) of said modulator stage (101 ), a cascade of a first AM modulator (102) and of a second FM modulator (103) is present, said FM modulator (103) being placed downstream of said AM modulator (102) and having an own output directly connected to the output (107) of said modulator stage (101 ), in which said AM modulator (102) has an input directly connected to said input (105) of said modulator stage and is directly powered by means of said electrical signal (s(t)) to be modulated, and in which said AM modulator (102) has an output on which it generates an intermediate signal (s2(t)) powered at input at said FM modulator (103).

5. Device according to one or more of the preceding claims, wherein said photoemitter (100) comprises an LED and/or a SLED and/or an amplified spontaneous emission LED and/or wherein the photoemitter (100) has a bandwidth greater than the band of the data signal (s(t)) and/or of the driving signal (v7(t), i7(t)), and/or has a bandwidth greater than the speed with which said data signal (s(t)) is received by the transmitter device (99).

6. Device according to one or more of the preceding claims, wherein:

- the photoemitter (100) is configured to emit an optical radiation (108) with radiation intensity (lr(t)) variable according to the said driving signal (v7(t), i7(t)); said radiation comprising a first continuous part (I), independent from said driving signal and a second time variable part direct function of said driving signal (v7(t), i7(t)), wherein said time variable part direct function of said driving signal (v7(t), i7(t)) is lower in absolute value than the absolute value taken by said first continuous part; and/or - wherein a driving stage (104) is also present for said at least one photoemitter (100) interposed between said output (107) of said modulator stage (101 ) and said at least one photoemitter (100), wherein said driving stage (104) is configured to condition and/or process the driving signal (v7(t), i7(t)); optionally said driving stage (104) comprising means and/or a device for signal processing comprising at least one operating configuration such that said radiation intensity (lr(t)) variable in accordance with said driving signal comprises a first continuous part (I), independent of said driving signal and a second time variable part that is a direct function of said driving signal (v7(t), i7(t)), wherein said time variable part that is a direct function of said driving signal (v7(t), i7(t)) is lower in absolute value than the absolute value taken by said first continuous part.

7. Device according to one or more of the preceding claims, configured to transmit the optical radiation (108) according to at least a first and a second average power;

said transmitter device (99) comprising a plurality of photoemitters (100) selectively simultaneously activable according to an automated activation algorithm, so that as the required average optical power increases, the number of photoemitters (100) simultaneously activated increases.

8. Use of a transmitter device (99) according to one or more of the preceding claims, for the optical transmission of multimedia data signals, comprising audio and/or video data present even simultaneously, and/or for transmitting data signals received for streaming and/or burst type data signals.

9. Method for modulating and transmitting a data signal (s(t)) by optical radiation (108), wherein the optical radiation (108) is capable of, and/or suitable for, being propagated also by reflection and/or indirect diffusion, said method being characterized in that it comprises:

- a step of adjusting the radiation intensity (lr(t)) of said optical radiation (108) emitted by at least one photoemitter (100), by means of, and/or according to, said driving signal (v7(t), i7(t)).

10. Method according to claim 9, wherein the modulation step comprises a hybrid, numerical and/or analog modulation step, and/or wherein the modulation step is performed by means of a modulator configured to perform an amplitude modulation and a frequency and/or phase modulation and/or wherein the modulation step is performed by means of a modulator comprising an AM modulator (102) and an FM and/or phase modulator (103).

1 1 . Method according to claim 9 or claim 10, wherein the modulation step comprises:

- a first amplitude modulation step of said data signal (s(t)), preferably by means of an AM modulator (102), wherein following said amplitude modulation step an intermediate signal (s2(t)) is generated of which said data signal (s(t)) is a modulating signal;

- a second step of modulating the frequency of said intermediate signal (s2(t)), preferably by means of an FM modulator (103), wherein, following said frequency modulating step, a driving signal (v7(t), i7(t)) is generated, in particular voltage or current;

- a step of adjusting the radiation intensity (lr(t)) of said optical radiation (108) emitted by at least one photoemitter (100) by means of and/or according to said driving signal (v7(t), i7(t)).

12. Method according to one or more of the preceding claims 9 to 1 1 , further comprising a step of providing said driving signal (v7(t), i7(t)) to a photoemitter (100) whose radiation intensity curve as a function of said driving signal (v7(t), i7(t)) is not constant and/or wherein said photoemitter (100) is configured to emit, and/or during use emits, an optical radiation variable in accordance with said driving signal (v7(t), i7(t)).

13. Method according to one or more of the preceding claims 9 to 12, further comprising:

- a step of simultaneous activation of a plurality of photoemitters (100) according to an algorithm or automated selective activation process according to an average power of required optical radiation, in which as such an average optical radiation power required increases, the number of photoemitters (100) simultaneously activated increases; or - a step of defining at least a first average optical radiation transmission power and a second average optical radiation transmission power, in which the second power is greater than the first power; said method further comprising a selection step of a first plurality of photoemitters (100) simultaneously activated for the transmission of said optical radiation (108) when said first power is required, or a selection step of a second plurality of photoemitters (100) simultaneously activated for the transmission of said optical radiation (108) when said second power is required, said second plurality of photoemitters (100) being greater than the first plurality of photoemitters (100).

14. Method according to one or more of the preceding claims 9 to 13, wherein in said step of adjusting the radiation intensity, the radiation intensity (lr(t)) of the optical radiation (108) made variable in accordance with said driving signal comprises a first continuous part (I), independent of said driving signal, and a second time variable part, direct function of said driving signal (v7(t), i7(t)), and wherein said time variable part that is a direct function of said driving signal (v7(t), i7(t)) is lower in absolute value than the absolute value taken by said first continuous part (I).

15. A receiver device (199) for receiving optical radiation (108), said device being adapted to cooperate with a transmitter device (99) according to one or more of the preceding claims 1 to 7, said receiver device (199) being adapted to output a replication (s'(t)) of an electrical data signal (s(t)) by means of a demodulation of the optical radiation (108) received according to the at least one predefined modulation scheme comprising a frequency modulation and an amplitude modulation;

said receiver device (199) is characterized in that it comprises at least one demodulator stage (201 ) comprising:

- an input (205) adapted to receive in use a voltage or current driving signal (v7'(t), i7'(t)) modulated and generated through a photoreceiver (200) operatively connected thereto and receiving in use an optical radiation (108) also reflected and/or rediffused, and

- an output (207) transmitting an output replication signal (s'(t)) for which said electrical signal (s(t)) represents a modulating signal, and wherein, between said input and said output of said demodulator stage (201 ) there is at least one demodulator (202, 203) configured to demodulate according to a predefined modulation scheme comprising a frequency and/or phase modulation and an amplitude modulation.

16. Receiver device according to claim 15, wherein the demodulator is a demodulator (202, 203) configured to perform a hybrid numerical and analog demodulation and/or wherein the demodulator (202, 203) comprises and/or implements an FM demodulator (203) and an AM demodulator (202).

17. Receiver according to one or more of claims 15 or 16, comprising a plurality of photoreceivers (200) arranged according to a predefined spatial configuration and selectively activable according to the power of the received optical radiation (108), preferably said receiver device (199) is configured to increase the number of photoreceivers (200) simultaneously activated as the power of the received optical radiation increases, optionally when a predetermined power threshold is exceeded.

18. Receiver device according to one or more of claims 15 to 17, wherein the demodulator (202, 203) comprises a cascade of a first FM demodulator (203) and a second AM demodulator (202) is present, said FM demodulator (203) being placed upstream of said AM demodulator (202), wherein said AM demodulator (202) has an input directly connected to the output of said FM demodulator (203).

19. Method for demodulation and reception of a data signal (s(t)) by means of optical radiation (108) even with indirect reflection, said method being characterized in that it comprises:

- a step of receiving, through at least one photoreceiver (200), an optical radiation (108) with its own radiation intensity (lr(t)) wherein through said at least one photoreceiver (200), a driving signal (v7'(t), i7'(t)) is generated, in particular in voltage or current, adapted to be transmitted and/or sent and/or demodulated to a demodulator (201 ); - a demodulation step of the driving signal (v7'(t), i7'(t)) for obtaining an output data signal, wherein the demodulation step is a demodulation step according to at least one predefined demodulation scheme comprising a frequency demodulation and an amplitude demodulation.

20. Method according to claim 19, wherein the demodulation step comprises:

- a first step of frequency demodulation by means of a FM demodulator (203), wherein following said frequency modulation step, an intermediate signal s2'(t)) is generated, starting from said voltage or current driving signal (v7'(t), i7'(t));

21. Method according to claim 19 or claim 20, wherein the radiation intensity (lr(t)) of said optical radiation (108) comprises a first continuous part (I) and a second part variable over time, and wherein the time-variable part comprises an amplitude and frequency modulation and/or is performed by amplitude and frequency modulation, in particular AM modulation and FM modulation.

22. Method according to one or more of claims 19 to 21 , comprising a measurement step of a power of the received optical radiation, and a step of selective simultaneous activation of a plurality of photoreceivers (200) simultaneously used for receiving the optical radiation (108) in accordance with the measured power, in which as the power of the optical radiation increases, the number of simultaneously activated photoreceivers (200) increases.

23. Reception system (300) comprising a receiver device (199) according to one or more of the preceding claims 15-18, said system at its interior comprising an optically sensitive element (301 ) provided with a reception area (302) thereof and on which one or more photoreceivers (200) are installed, wherein said one or more photoreceivers (200) achieve a reception area (302) adapted to acquire at least one image in which a variation of radiation intensity (lr(t)) transmitted by a modulated and/or modulating photoemitter according to a predefined modulation scheme is present, said reception system (300) comprising means for selecting a part of the reception area (302) formed by the plurality of photoreceivers (200), configured to automatically select part of the reception area (302) in which a variation of radiation intensity (lr(t)) transmitted by a modulated photoemitter is present, and to cause the sending of a signal substantially corresponding to said variation of radiation intensity (lr(t)) towards said demodulator stage (201 ) of said receiver device.

24. System according to claim 23, configured to execute a tracking algorithm through which said selection means are configured in order to find if a point of the reception area (302) or the point on the sub-portion of the reception area (302) in which said variation of radiation intensity (lr(t)) arrives, moves, and in order to perform an automatic tracking thereof.