Method and system for transmitting and receiving electromagnetic radiation beams with orbital angular momentum detection and related telecommunication methods and systems

Abstract

A method for transmitting and receiving an electromagnetic radiation beam is described, the method being suitable for determining the orbital angular momentum of the received electromagnetic radiation beam. A system for transmitting and receiving an electromagnetic radiation beam is further described, the system being capable of performing the aforementioned method. A method for performing telecommunication of signals modulated according to any modulation technique and grouped by means of orbital angular momentum multiplexing is further described. A telecommunication system is further described, the system being capable of performing the aforementioned method for performing telecommunication of modulated signals.

Description

Technical Field

[0001] The present invention generally relates to the technical field of emission and reception of electromagnetic beams (in particular light beams / laser beams and microwave beams) with detection of the orbital angular momentum of the beam, as well as to the field of telecommunications based on electromagnetic beams (in particular light beams / laser beams and microwave beams), orbital angular momentum modulation and / or orbital angular momentum multiplexing. Background Art

[0002] The propagation theory of electromagnetic beams (especially laser beams and microwave beams) has recently demonstrated the existence of orbital angular momentum.

[0003] From a traditional perspective, orbital angular momentum is a concept related to the different transverse modes of beam propagation.

[0004] This can also be considered as an illustration of the fact that the propagation front of the orbital angular momentum (OAM) wave is not a simple plane, but has an evolution that can be represented by a helicoid.

[0005] In other words, the Poynting vector and the wave vector are no longer simply parallel to the propagation direction, but are twisted around the propagation direction.

[0006] From a quantum perspective, orbital angular momentum is treated as another quantum number than spin.

[0007] Recently, beams with orbital angular momentum different from zero and capable of taking different values ​​have also been experimentally demonstrated.

[0008] Due to its aforementioned characteristics, the "orbital angular momentum" variable is particularly difficult to detect and characterize when the detector is illuminated by only a limited portion of the radiation beam, even when the singularity is far away. In fact, there are no reliable systems and methods that allow the orbital angular momentum of an electromagnetic beam to be detected, for example, by means of local measurement of the received laser light, even when only a limited portion of the beam is incident on the detector, even when the singularity is far away.

[0009] On the other hand, there is a felt need to detect the orbital angular momentum of a received beam for various reasons including, for example, characterization of the beam and utilization of the angular momentum variable for telecommunication purposes.

[0010] This requirement cannot currently be met by known technical solutions through local measurements.

[0011] Applicants have also recognized the possibility of utilizing the orbital angular momentum variable as an additional degree of freedom, which may be advantageous both for modulating and multiplexing signals.

[0012] However, the background art in the considered technical field does not provide a solution for reliable long-distance communication based on orbital angular momentum multiplexing and / or modulation. Therefore, a particular need for such a solution is felt. Summary of the Invention

[0013] In view of the above, the object of the present invention is to provide a method for transmitting and receiving electromagnetic radiation beams, which method is suitable for determining the orbital angular momentum of the received electromagnetic radiation beam, for example to allow at least part of eliminating the disadvantages of the prior art referred to above and to meet the above-mentioned needs that are particularly felt in the technical field under consideration.

[0014] This object is achieved by a method for transmitting and receiving an electromagnetic radiation beam according to an embodiment of the present invention, said method being suitable for determining the orbital angular momentum of the received electromagnetic radiation beam. Such a method comprises the following steps:

[0015] - generating at least one main electromagnetic radiation beam characterized by a first orbital angular momentum, a first spectrum in a first frequency band, and a first beam curvature radius;

[0016] - generating a reference beam of electromagnetic radiation characterized by a second orbital angular momentum, a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius substantially identical to the first beam curvature radius;

[0017] - generating a composite electromagnetic radiation beam comprising a superposition of said at least one main electromagnetic radiation beam and said reference electromagnetic radiation beam;

[0018] - emitting the resulting composite electromagnetic radiation beam;

[0019] - receiving the composite electromagnetic radiation beam by means of a first beam detector located in a first position to generate a first composite beam electrical signal, the first composite beam electrical signal being representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the first position;

[0020] - receiving the composite electromagnetic radiation beam by means of a second beam detector located in a second position different from the first position to generate a second composite beam electrical signal, the second composite beam electrical signal being representative of the electric field and / or magnetic field of the composite electromagnetic radiation beam and / or the intensity of the received electromagnetic radiation in the second position;

[0021] performing frequency discrimination of the first composite beam electrical signal to obtain a first main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main electromagnetic radiation beam in the first position and a first reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the first position;

[0022] - performing frequency discrimination of the second composite beam electrical signal to obtain a second main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main electromagnetic radiation beam in the second position and a second reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the second position;

[0023] -Determining the orbital angular momentum of the main electromagnetic radiation beam and / or the spatial phase variable of the main electromagnetic radiation beam attributable to the orbital angular momentum of the main electromagnetic radiation beam based on the first main beam electrical signal, the second main beam electrical signal, the first reference beam electrical signal and the second reference beam electrical signal.

[0024] The present invention also relates to a system for transmitting and receiving electromagnetic radiation beams, which system is capable of performing the above method. Such a system comprises:

[0025] means for generating a main electromagnetic radiation beam, the means for generating a main electromagnetic radiation beam being configured to generate a main electromagnetic radiation beam characterized by a first orbital angular momentum, a first spectrum in a first frequency band, and a first beam curvature radius;

[0026] - means for generating a reference electromagnetic radiation beam, the means for generating a reference electromagnetic radiation beam being configured to generate a reference electromagnetic radiation beam characterized by a second orbital angular momentum, a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius substantially identical to the first beam curvature radius;

[0027] - means for generating a composite electromagnetic radiation beam, configured to generate a composite electromagnetic radiation beam comprising a superposition of the main electromagnetic radiation beam and the reference electromagnetic radiation beam, and means for emitting the composite electromagnetic radiation, configured to emit the generated composite electromagnetic radiation beam;

[0028] - means for receiving said composite beam of electromagnetic radiation, comprising:

[0029] a first beam detection device located in a first position and configured to generate a first composite beam electrical signal representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the first position;

[0030] a second beam detection device located in a second position different from the first position and configured to generate a second composite beam electrical signal representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the second position;

[0031] a first frequency discrimination device configured to perform frequency discrimination of the first composite beam electrical signal to obtain a first main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main electromagnetic radiation beam in the first position and a first reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the first position;

[0032] - a second frequency discrimination device configured to perform frequency discrimination of the second composite beam electrical signal to obtain a second main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main electromagnetic radiation beam in the second position and a second reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the second position;

[0033] - a device for determining orbital angular momentum, the device for determining orbital angular momentum being configured to determine the orbital angular momentum of the main electromagnetic radiation beam and / or the spatial phase variable of the main electromagnetic radiation beam attributable to the orbital angular momentum of the main beam based on the first main beam electrical signal, the second main beam electrical signal, the first reference beam electrical signal and the second reference beam electrical signal.

[0034] The invention also relates to a method for performing telecommunication of signals modulated according to any modulation technique and grouped by means of orbital angular momentum multiplexing. This method comprises the following steps:

[0035] - generating a first beam of electromagnetic radiation characterized by a first orbital angular momentum, and generating at least one second beam of electromagnetic radiation characterized by a corresponding at least one second orbital angular momentum,

[0036] wherein the first beam of electromagnetic radiation and the at least one second beam of electromagnetic radiation have respective spectra in the same first frequency band and further have respective radii of curvature that are substantially consistent with the value of the first beam radius of curvature;

[0037] - modulating a first piece of information to be transmitted on said first beam of electromagnetic radiation by means of any modulation technique, so as to obtain a first modulated beam, said first piece of information to be transmitted being represented by a first modulation function a(t);

[0038] - modulating at least one second piece of information to be transmitted on said at least one second beam of electromagnetic radiation by means of any modulation technique to obtain a second modulated beam, said second piece of information to be transmitted being represented by a second modulation function b(t);

[0039] - generating a reference beam of electromagnetic radiation characterized by a second orbital angular momentum, a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius having a value substantially identical to the value of the first beam curvature radius;

[0040] - superimposing and / or combining the reference electromagnetic radiation beam, the first modulated beam and the second modulated beam to produce a composite electromagnetic radiation beam comprising a superposition of the reference electromagnetic radiation beam and a main beam, and further comprising a superposition of the first modulated beam and at least one second modulated beam;

[0041] - emitting the resulting composite electromagnetic radiation beam;

[0042] - receiving the composite electromagnetic radiation beam by means of a first beam detector located in a first position to generate a first composite beam electrical signal, the first composite beam electrical signal being representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the first position;

[0043] - receiving the composite electromagnetic radiation beam by means of a second beam detector located at a second position different from the first position to generate a second composite beam electrical signal, the second composite beam electrical signal being representative of the electric field and / or magnetic field of the composite electromagnetic radiation beam and / or the intensity of the received electromagnetic radiation in the second position;

[0044] performing frequency discrimination of the first composite beam electrical signal to obtain a first main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main beam in the first position and a first reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the first position;

[0045] performing frequency discrimination of the second composite beam electrical signal to obtain a second main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main beam in the second position and a second reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the second position;

[0046] - determining a phase of the first main beam electrical signal and a phase of the second main beam electrical signal;

[0047] - determining the phase of the first reference beam electrical signal and the phase of the second reference beam electrical signal;

[0048] - determining a first phase difference value, the first phase difference value corresponding to the difference between the phase of the first main beam electrical signal and the phase of the second main beam electrical signal, the first phase difference value depending on the values ​​taken by the first modulation function a(t) and the second modulation function b(t);

[0049] - determining a second phase difference value, the second phase difference value corresponding to the difference between the phase of the first reference beam electrical signal and the phase of the second reference beam electrical signal;

[0050] - subtracting the second phase difference value divided by the second wave number k' from the first phase difference value divided by the first wave number k to obtain a difference,

[0051] wherein the first wave number is the wave number corresponding to the main beam, defined as k=2π / λ, λ being the wavelength of the main beam, and wherein the second wave number is the wave number corresponding to the reference electromagnetic radiation beam, defined as k'=2π / λ', λ' being the wavelength of the reference electromagnetic radiation beam,

[0052] said difference represents a combination of the values ​​taken by said first modulation function a(t) and said second modulation function b(t) independently of a positional inclination condition between said first beam detector and said second beam detector and independently of a phase variation caused by disturbances to which the transmitted composite electromagnetic radiation beam is subjected prior to reception;

[0053] - based on the determined difference, demultiplexing and demodulating information modulated on each of the first modulated beam and the at least one second modulated beam.

[0054] The present invention also relates to a telecommunication system capable of executing the above-mentioned method for performing telecommunication of modulated signals. Such a system comprises:

[0055] - a device for generating an electromagnetic beam, said device for generating an electromagnetic beam being configured to:

[0056] - generating a first beam of electromagnetic radiation characterized by a first orbital angular momentum, and generating at least one second beam of electromagnetic radiation characterized by a corresponding at least one second orbital angular momentum, wherein the first beam of electromagnetic radiation and the at least one second beam of electromagnetic radiation both have respective spectra in the same first frequency band and further have respective radii of curvature that are substantially consistent with the value of the first beam radius of curvature;

[0057] - generating a reference beam of electromagnetic radiation characterized by a second orbital angular momentum, a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius having a value substantially identical to the value of the first beam curvature radius;

[0058] - a modulation device, said modulation device being configured to:

[0059] - modulating the first piece of information to be transmitted in said first beam of electromagnetic radiation by means of any amplitude, and / or phase, and / or frequency modulation technique to obtain a first modulated beam, said first piece of information to be transmitted being represented by a first modulation function a(t);

[0060] - modulating at least one second piece of information to be transmitted on said at least one second beam of electromagnetic radiation by means of any amplitude and / or phase and / or frequency modulation technique to obtain a second modulated beam, said at least one second piece of information to be transmitted being represented by a second modulation function b(t);

[0061] - beam combining and / or superposition means configured to superpose and / or combine the reference electromagnetic radiation beam, the first modulated beam and the second modulated beam to generate a composite electromagnetic radiation beam comprising a superposition of the reference electromagnetic radiation beam and the main beam and, in turn, a superposition of the first modulated beam and at least one second modulated beam;

[0062] - a transmitting device configured to transmit the generated composite electromagnetic radiation beam;

[0063] - means for receiving the composite electromagnetic radiation beam, said means for receiving the composite electromagnetic radiation beam comprising:

[0064] a first beam detection device located in a first position and configured to generate a first composite beam electrical signal representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the first position;

[0065] a second beam detection device located in a second position different from the first position and configured to generate a second composite beam electrical signal representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the second position;

[0066] a first frequency discrimination device configured to perform frequency discrimination of the first composite beam electrical signal to obtain a first main beam electrical signal and a first reference beam electrical signal, the first main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main beam in the first position, and the first reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference beam in the first position;

[0067] a second frequency discrimination device configured to perform frequency discrimination of the second composite beam electrical signal to obtain a second main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main beam in the second position and a second reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference beam in the second position;

[0068] - a phase determination device, said phase determination device being configured to:

[0069] - determining a phase of the first main beam electrical signal and a phase of the second main beam electrical signal;

[0070] - determining the phase of the first reference beam electrical signal and the phase of the second reference beam electrical signal;

[0071] - determining a first phase difference value corresponding to the difference between the phase of the first main beam electrical signal and the phase of the second main beam electrical signal, the first phase difference value depending on the values ​​taken by the first modulation function a(t) and the second modulation function b(t);

[0072] - determining a second phase difference value corresponding to a difference between a phase of the first reference beam electrical signal and a phase of the second reference beam electrical signal;

[0073] - subtracting the second phase difference value divided by the second wave number k' from the first phase difference value divided by the first wave number k to obtain a difference value, the difference value representing the combination of the values ​​taken by the first modulation function a(t) and the second modulation function b(t) independently of the positional inclination conditions between the first beam detector and the second beam detector and independently of phase variations caused by disturbances to which the transmitted composite electromagnetic radiation beam was subjected before reception;

[0074] wherein the first wave number is a wave number corresponding to the main beam, defined as k=2π / λ, λ being the wavelength of the main beam belonging to the first frequency band, and wherein the second wave number k′ is a wave number corresponding to the reference beam, defined as k′=2π / λ′, λ′ being the wavelength of the reference beam belonging to the second frequency band;

[0075] - processing means configured to demultiplex and demodulate information modulated on each of said first modulated beam and said at least one second modulated beam based on said determined difference value. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Further features and advantages of the above-described method and system according to the invention will become apparent from the following description of a preferred embodiment given by way of indicative and non-limiting example with reference to the accompanying drawings, in which:

[0077] - Figure 1 A simplified diagram showing the transmitting portion of an embodiment of a system for transmitting and receiving a beam of electromagnetic radiation according to the present invention; Figure 1 Some steps of the corresponding method are also shown;

[0078] - Figure 2 A simplified diagram showing the receiving portion of an embodiment of a system for transmitting and receiving beams of electromagnetic radiation according to the present invention; Figure 2 Some other steps of the corresponding method are also shown;

[0079] - Figure 3 A simplified diagram showing the transmitting portion of an embodiment of a system for telecommunication according to the present invention; Figure 3 Some steps of the corresponding method are also shown;

[0080] - Figure 4 A simplified diagram showing the receiving portion of an embodiment of a system for telecommunication according to the invention; Figure 4 Some other steps of the corresponding method are also shown;

[0081] - Figure 5 An embodiment of a system according to the present invention is shown, comprising a correlator;

[0082] - Figure 6 Describes some of the geometric quantities used in system diagrams. DETAILED DESCRIPTION

[0083] refer to Figures 1 to 6 , a method for transmitting and receiving a beam of electromagnetic radiation is described, the method being suitable for determining the orbital angular momentum of the received beam of electromagnetic radiation.

[0084] The method first includes the steps of generating at least one main electromagnetic radiation beam F1, and the step of generating a reference electromagnetic radiation beam F0, wherein the main electromagnetic radiation beam is characterized by a first orbital angular momentum L1, a first spectrum in a first frequency band, and a first beam curvature radius, and the reference electromagnetic radiation beam F0 is characterized by a second orbital angular momentum L0, a second spectrum in a second frequency band different from the above-mentioned first frequency band, and a second beam curvature radius substantially consistent with the above-mentioned first beam curvature radius.

[0085] It should be noted that the above characterization based on the first orbital angular momentum L1 and the second orbital angular momentum L0 can also be described in terms of the topological charge (l1, l0) because the angular momentum L and the topological charge l are related by the following relationship:

[0086] L = (l*h) / 2π (where h is Planck's constant).

[0087] Thus, the method comprises generating a composite electromagnetic radiation beam Q1 comprising a superposition of the at least one primary beam F1 and the reference beam F0, and emitting the composite electromagnetic radiation beam Q1 thus generated.

[0088] The method also includes the steps of receiving the above-mentioned composite electromagnetic radiation beam Q1 by means of a first beam detector 1 located in a first position to generate a first composite beam electrical signal D1, which represents the electric field, and / or magnetic field, and / or the intensity of electromagnetic radiation of the composite beam in such a first position; and the step of receiving the above-mentioned composite electromagnetic radiation beam Q1 by means of a second beam detector 2 located in a second different position relative to the above-mentioned first position to generate a second composite beam electrical signal D2, which represents the electric field, and / or magnetic field, and / or the intensity of the received electromagnetic radiation of the composite beam in such a second position.

[0089] The method also includes the following steps: performing frequency identification of the first composite beam electrical signal D1 to obtain a first main beam electrical signal P1 and a first reference beam electrical signal R1, wherein the first main beam electrical signal P1 represents the electric field, and / or magnetic field, and / or intensity attributed to the main beam in the first position, and the first reference beam electrical signal R1 represents the electric field, and / or magnetic field, and / or intensity attributed to the reference beam in the first position; and performing frequency identification of the second composite beam electrical signal D2 to obtain a second main beam electrical signal P2 and a second reference beam electrical signal R2, wherein the second main beam electrical signal P2 represents the electric field, and / or magnetic field, and / or intensity attributed to the main beam in the second position, and the second reference beam electrical signal R2 is the electric field, and / or magnetic field, and / or intensity attributed to the reference beam in the second position.

[0090] Ultimately, the method includes determining the orbital angular momentum L1 of the main electromagnetic radiation beam and / or the spatial phase variable of the main electromagnetic radiation beam attributable to the main beam orbital angular momentum L1 based on the above-mentioned first main beam electrical signal P1, second main beam electrical signal P2, first reference beam electrical signal R1 and second reference beam electrical signal R2.

[0091] According to one embodiment of the method, the determining step includes: determining a first phase difference value ΔP, which corresponds to the difference between the phase of the first main beam electrical signal P1 and the phase of the second main beam electrical signal P2; further, determining a second phase difference value ΔR, which corresponds to the difference between the phase of the first reference beam electrical signal R1 and the phase of the second reference beam electrical signal R2; then, subtracting the second phase difference value ΔR divided by the second wave number k' from the first phase difference value ΔP divided by the first wave number k to obtain a difference value (Q2 = ΔP / k-ΔR / k'), the above difference value is independent of the position inclination condition between the above-mentioned first detector and the second detector, but is derived from the relative position of the two detectors relative to the beam propagation, and the difference value is independent of the phase variable caused by the interference to which the transmitted composite beam is subjected before reception; and then determining the orbital angular momentum of the main electromagnetic radiation beam based on the above-mentioned difference value (Q2 = ΔP / k-ΔR / k').

[0092] The first wave number k is the wave number corresponding to the main beam and is defined as k=2π / λ, where λ is the wavelength of the main beam belonging to the first frequency band. The second wave number k' is the wave number corresponding to the reference beam and is defined as k'=2π / λ', where λ' is the wavelength of the reference beam belonging to the second frequency band.

[0093] "Positional inclination" (or "positional tilt") is defined as the angle formed between a line connecting two detectors and the (orthogonal) projection of this line onto a plane orthogonal to the beam propagation axis.

[0094] According to a specific implementation example, the step of determining the orbital angular momentum of the main electromagnetic radiation beam comprises determining the orbital angular momentum of the main electromagnetic radiation beam based on the following formula:

[0095] ΔP / k–ΔP / k'∝(L1 / k-L0 / k')(θ2-θ1)

[0096] Wherein θ1 is the angular position of the first detector measured on a plane orthogonal to the composite beam propagation vector containing the first detector; θ2 is the angular position of the second detector measured on a plane orthogonal to the composite beam propagation vector containing the second detector; and ∝ indicates proportional.

[0097] According to one implementation option, the step of determining the first phase difference value ΔP includes comparing the phase of the first main beam electrical signal P1 with the phase of the second main beam electrical signal P2 by means of a first phase comparator 3; the step of determining the second phase difference value ΔR includes comparing the phase of the first reference beam electrical signal R1 with the phase of the second reference beam electrical signal R2 by means of a second phase comparator 4.

[0098] According to another implementation option, the step of determining the first phase difference value ΔP includes performing a correlation operation between the first main beam electrical signal P1 and the second main beam electrical signal P2; and the step of determining the second phase difference value ΔR includes performing a correlation operation between the first reference beam electrical signal R1 and the second reference beam electrical signal R2.

[0099] According to an embodiment of the method, the orbital angular momentum of the reference beam is always known.

[0100] According to an implementation option, the orbital angular momentum of the reference beam takes a constant value L0=0.

[0101] According to an embodiment of the method, the first position of the first detector 1 and the second position of the second detector 2 are fixed and constant and differ from the position of the singularity point of the beam.

[0102] According to another embodiment of the method, the first position of the first detector 1 and / or the second position of the second detector 2 are movable and the reciprocal relationship between the first and second positions is always known.

[0103] According to an implementation option, the second frequency band is substantially monochromatic.

[0104] According to a particular implementation option, the second frequency band is adjacent to the first frequency band.

[0105] According to a possible embodiment of the method, the step of performing frequency discrimination of the first composite beam electrical signal or the second composite beam electrical signal comprises performing frequency filtering or performing frequency separation by means of heterodyning techniques or other frequency separation methods.

[0106] According to an embodiment of the method, the at least one main electromagnetic radiation beam is unmodulated.

[0107] According to further embodiments of the method, the at least one main electromagnetic radiation beam is amplitude-modulated, and / or phase-modulated, and / or frequency-modulated, and / or orbital angular momentum-modulated.

[0108] According to one embodiment of the method, all of the aforementioned emitted and received electromagnetic beams are light beams and / or laser beams.

[0109] In the following, a specific implementation example of this method is given using relevant physical and mathematical analysis.

[0110] In the following description and in Figure 1 and Figure 2 , for simplicity, the points where different signals are located (first composite beam electrical signal D1, second composite beam electrical signal D2, first main beam electrical signal P1, first reference beam electrical signal R1, second main beam electrical signal P2, second reference beam electrical signal) are referred to as the same names as their respective signals.

[0111] As already observed, the composite beam Q1 is generated by superimposing at least one beam with orbital angular momentum L=L1 (other than 0) (herein defined as the main beam F1) on a beam with angular momentum L=L0 (herein defined as the reference beam F0).

[0112] The main beam can be modulated or unmodulated. The reference beam has a frequency band that does not overlap with the frequency band of the main beam. The frequency band of the reference beam is preferably quasi-monochromatic and adjacent to the frequency band of the main beam. The reference beam has substantially the same curvature and propagation vector as the main beam. The reference beam preferably has a topological charge l0 = 0, which also implies an orbital angular momentum L0 = 0.

[0113] The identification of the spatial phase difference caused by the main beam with orbital angular momentum L1 is obtained by using two detectors at any position in space except the point of singularity of the vortex.

[0114] As is known, the expression "singularity of a vortex" refers to the point in a vortex at which the result of the electromagnetic field is reduced to zero and at which the phase of the field cannot be determined.

[0115] In the case of an unmodulated main beam, the electric field E1 or the associated signal (at Figure 2 Indicated as D1) can be represented by the following analytical expression:

[0116]

[0117] where t is time, A1 and B1 are arbitrary non-zero amplitudes, l1 is the topological charge of the main beam, l0 is the topological charge of the reference beam, θ1 is the angular position of the detector measured in a plane orthogonal to the composite beam propagation vector containing the first detector 1, and is the arbitrary phase due to position tilt, and and is an arbitrary phase due to interference of the propagating wavefront.

[0118] Likewise, the electric field E2 or the associated signal ( Figure 2 Indicated as D2) can be represented by the following analytical expression:

[0119]

[0120] where t is time, A2 and B2 are arbitrary non-zero amplitudes, l1 is the topological charge of the main beam, l0 is the topological charge of the reference beam, θ2 is the angular position of detector 2 measured in a plane orthogonal to the composite beam propagation vector containing detector 2, and is the arbitrary phase due to position tilt, and and is an arbitrary phase due to interference of the propagating wavefront.

[0121] As a further illustration of the geometric quantities defined above, Figure 6 The composite beam generating system described above (in Figure 6 The propagation axis z of the composite beam Q1 produced is indicated by reference numeral 30 in FIG. Figure 6 Also indicated are the plane xy perpendicular to the propagation axis z, the position vectors of the two detectors 1 and 2, respectively. and and the aforementioned angular positions θ1 and θ2 of the two detectors, respectively.

[0122] The fields or correlation signals are separated in frequency by means of various possible techniques (which are known per se) so that in R1 and R2 only the fields or correlation signals in the frequency band of the reference beam are present, while in P1 and P2 only the fields or correlation signals in the frequency band of the main beam are present.

[0123] Therefore, the following analytical expression can be obtained:

[0124] In R1:

[0125] In R2:

[0126] In P1:

[0127] In P2:

[0128] The second phase comparator 4 provides a quantity proportional to the phase difference of the field and the associated signal between R1 and R2:

[0129]

[0130] The first phase comparator 3 provides a quantity proportional to the phase difference of the fields and the associated signal between P1 and P2:

[0131]

[0132] Because the main beam has a curvature substantially equal to that of the reference beam, and a propagation direction substantially identical to that of the reference beam, the phase difference associated with the tilt (tilt) has an excellent approximation:

[0133]

[0134] Because the distortion phenomena due to propagation are very similar for the primary and reference beams (which are superimposed and emitted in the composite beam), the phase difference associated with the distortion has an excellent approximation:

[0135]

[0136] Furthermore, the proportionality constants of the two phase comparators may be chosen so that the phase differences are consistent.

[0137]

[0138] Based on the above, the signal Q2 provides a quantity proportional to the difference:

[0139]

[0140] As desired, such quantities are independent of position tilt and interference due to propagation.

[0141] Once the value of Q2 is measured (i.e., ΔP / k–ΔR / k'), the topological charge of the main beam, l1, and hence the orbital angular momentum, L1, of the main beam are easily obtained from the equation above, provided that the values ​​of θ1, θ2, k, k', and l0 (the topological charge of the reference beam, which can be initially set) are known, remembering that:

[0142] L=(l*h) / 2π.

[0143] If the main beam is phase modulated, the equations at points R1, R2, P1, and P2 become:

[0144] In R1:

[0145] In R2:

[0146] In P1:

[0147] In P2:

[0148] where δ(t) is the time-varying phase term due to the phase modulation detected equally on the first and second detectors. Since the phase term δ(t) is compensated at the output of the second phase comparator 2, the following result is also obtained:

[0149]

[0150] If the main beam is frequency-modulated, the equations at points R1, R2, P1, and P2 become:

[0151] In R1:

[0152] In R2:

[0153] In P1:

[0154] In P2:

[0155] Where m(τ) is the time-varying modulation signal, and k f is a constant. Compensating at the output of the second phase comparator still yields the following result:

[0156]

[0157] A method will now be described, also included in the present invention, for carrying out the telecommunication of signals modulated according to any known modulation technique and grouped by means of orbital angular momentum variable multiplexing.

[0158] The method comprises the steps of generating a first electromagnetic radiation beam F1 characterized by a first orbital angular momentum L1, and generating at least one second electromagnetic radiation beam F2 characterized by at least one corresponding third orbital angular momentum L2. The first electromagnetic radiation beam F1 and the at least one second electromagnetic radiation beam F2 have respective spectra in the same first frequency band and further have respective radii of curvature that are substantially identical to the value of the first beam radius of curvature.

[0159] The method then includes: modulating a first piece of information to be transmitted (represented by a first modulation function a(t)) on a first electromagnetic radiation beam F1 by means of any modulation technology to obtain a first modulated beam Fm1; further, modulating at least one second piece of information to be transmitted (represented by a second modulation function b(t)) on at least one second electromagnetic radiation beam F2 by means of any modulation technology to obtain a second modulated beam Fm2; and then, generating a reference electromagnetic radiation beam F0, which is characterized by a second orbital angular momentum L0, a second spectrum in a second frequency band different from the above-mentioned first frequency band, and a second beam curvature radius, and the second beam curvature radius has a value substantially consistent with the value of the above-mentioned first beam curvature radius.

[0160] The method then includes: a step of superimposing and / or combining the above-mentioned reference beam F0, the first modulated beam Fm1 and the second modulated beam Fm2 to produce a composite electromagnetic radiation beam Q1, which composite electromagnetic radiation beam Q1 includes the superposition of the reference beam F0 and the main beam, and further includes the superposition of the above-mentioned first modulated beam Fm1 and at least one second modulated beam Fm2.

[0161] The method then comprises the step of emitting the resulting composite beam of electromagnetic radiation Q1.

[0162] The method then includes: receiving the above-mentioned composite electromagnetic radiation beam with the aid of a first beam detector 1 located at a first position to generate a first composite beam electrical signal D1, which represents the electric field, and / or magnetic field, and / or the intensity of electromagnetic radiation of the composite beam in the above-mentioned first position; and receiving the above-mentioned composite electromagnetic radiation beam with the aid of a second beam detector located at a second different position relative to the first position to generate a second composite beam electrical signal D2, which represents the electric field, and / or magnetic field, and / or the intensity of the received electromagnetic radiation of the composite beam in the second position.

[0163] The method also includes: a step of performing frequency identification of the first composite beam electrical signal D1 to obtain a first main beam electrical signal P1 and a first reference beam electrical signal R1, wherein the first main beam electrical signal P1 represents the electric field, and / or magnetic field, and / or intensity attributed to the main beam in the first position, and the first reference beam electrical signal R1 represents the electric field, and / or magnetic field, and / or intensity attributed to the reference beam in the first position; and a step of performing frequency identification of the second composite beam electrical signal D2 to obtain a second main beam electrical signal P2 and a second reference beam electrical signal R2, wherein the second main beam electrical signal P2 represents the electric field, and / or magnetic field, and / or intensity attributed to the main beam in the second position, and the second reference beam electrical signal R2 represents the electric field, and / or magnetic field, and / or intensity attributed to the reference beam in the second position.

[0164] The method further comprises: determining the phase of the first main beam electrical signal P1 and the phase of the second main beam electrical signal P2; further determining the phase of the first reference beam electrical signal R1 and the phase of the second reference beam electrical signal R2; and then determining the first phase difference ΔP ab , the first phase difference ΔP ab corresponds to the difference between the phase of the first main beam electrical signal P1 and the phase of the second main beam electrical signal P2, wherein such a first phase difference value ΔP ab Depending on the values ​​of the first modulation function a(t) and the second modulation function b(t), a second phase difference ΔR is determined, which corresponds to the difference between the phase of the first reference beam electrical signal R1 and the phase of the second reference beam electrical signal R2.

[0165] Then, the method includes: starting from the first phase difference value ΔP ab Divide the first wave number k minus the second phase difference ΔR divided by the second wave number k' to obtain the difference (Q2 = ΔP ab The first wave number k corresponds to the wave number of the main beam and is defined as k = 2π / λ, where λ is the wavelength of the main beam belonging to the first frequency band. The second wave number k' corresponds to the wave number of the reference beam and is defined as k' = 2π / λ', where λ' is the wavelength of the reference beam belonging to the second frequency band.

[0166] The above-mentioned difference Q2 represents a combination of the values ​​of the first modulation function a(t) and the second modulation function b(t), and is independent of the positional inclination condition between the first detector 1 and the second detector 2, and is independent of the phase variable caused by the interference to the transmitted composite light beam before reception.

[0167] Finally, the method comprises: based on the difference (Q2 = ΔP ab / k-ΔR / k′) demultiplexes and demodulates information modulated on each of the first modulated beam Fm1 and the at least one modulated beam Fm2.

[0168] According to an embodiment of this method, the number of modulation beams of the orbital angular momentum multiplexing is greater than two.

[0169] According to an embodiment of this method, the first electromagnetic radiation beam F1 and the at least one second electromagnetic radiation beam F2 are digitally amplitude modulated according to the amplitudes of a first modulation function a(t) and at least one second modulation function b(t).

[0170] In this case, the difference (Q2 = ΔP ab / k-ΔR / k') can take multiple expected values, each expected value representing a corresponding combination of digital amplitude values ​​taken by the first modulation function a(t) and the at least one second modulation function b(t).

[0171] According to one implementation option, the first electromagnetic radiation beam F1 and the at least second electromagnetic radiation beam F2 are digitally amplitude modulated in a binary manner, and the amplitudes of the first modulation function a(t) and the at least one second modulation function b(t) can take logical values ​​0 or 1.

[0172] In this case, the method further comprises the step of detecting the received power or intensity Q3 corresponding to the first main beam electrical signal P1 or the second main beam electrical signal P2 (by means of the detector 16) and comparing the received power or intensity with a minimum threshold.

[0173] Determine the difference (Q2 = ΔP ab / k-ΔR / k') can take the first expected value (ΔP 10 / k-ΔR / k'), or the second expected value (ΔP 01 / k-ΔR / k'), or the third expected value (ΔP 11 / k-ΔR / k'), the first expected value depends on the first orbital angular momentum (L1), the second expected value depends on the third orbital angular momentum (L2), and the third expected value depends on the combination of the first angular momentum and the second angular momentum.

[0174] The steps of demodulating, demultiplexing and demodulating the modulated information include: if the difference (ΔP ab / k-ΔR / k') takes the first expected value (ΔP 10 / k-ΔR / k'), it is recognized that the first modulated beam Fm1 carries information corresponding to 1 and the second modulated beam Fm2 carries information corresponding to 0; if the determined difference (ΔP ab / k-ΔR / k') takes the second expected value (ΔP 01 / k-ΔR / k'), it is recognized that the first modulated beam Fm1 carries information corresponding to 0 and the second modulated beam Fm2 carries information corresponding to 1; if the determined difference (ΔP ab / k-ΔR / k') takes the third expected value (ΔP 11 / k-ΔR / k'), it is identified that the first modulated beam Fm1 carries information corresponding to 1 and the second modulated beam Fm2 carries information corresponding to 1; if the received power or intensity Q3 is less than the above-mentioned minimum threshold, it is identified that the first modulated beam Fm1 carries information corresponding to 0 and the second modulated beam Fm2 carries information corresponding to 0.

[0175] According to another embodiment of this method, the first electromagnetic radiation beam F1 and the at least one second electromagnetic radiation beam F2 are digitally modulated based on angular momentum. In this case, the angular momentum of the first beam F1 can take two different discrete values ​​based on a first modulation function a(t), and the angular momentum of the at least one second beam F2 can take two different discrete values ​​based on the respective at least one second modulation function b(t).

[0176] Difference (Q2 = ΔP ab / k-ΔR / k') can take multiple expected values, each expected value representing a corresponding combination of digital amplitude values ​​taken by the first modulation function a(t) and at least the second modulation function b(t).

[0177] According to an implementation option, the amplitudes of the first modulation function a(t) and at least the second modulation function b(t) can take logical values ​​0 or 1.

[0178] Determine the difference (ΔP ab / k-ΔR / k') can be: when the first modulation function a(t) takes the value 1 and the second modulation function takes the value 0, the first expected value (ΔP 10 / k-ΔR / k'); or, when the first modulation function a(t) takes a value of 0 and the second modulation function takes a value of 1, take the second expected value (ΔP 01 / k-ΔR / k'); or, when the first modulation function a(t) takes a value of 1 and the second modulation function takes a value of 1, take the third expected value (ΔP 11 / k-ΔR / k'); or, when the first modulation function a(t) takes a value of 0 and the second modulation function takes a value of 0, take the fourth expected value (ΔP 00 / k-ΔR / k').

[0179] In this case, the steps of demodulating, demultiplexing and demodulating the modulated information include: if the determined difference (ΔP ab / k-ΔR / k') takes the first expected value (ΔP 10 / k-ΔR / k'), it is recognized that the first modulated beam Fm1 carries information corresponding to 1 and the second modulated beam Fm2 carries information corresponding to 0; if the determined difference (ΔP ab / k-ΔR / k') takes the second expected value (ΔP 01 / k-ΔR / k'), it is recognized that the first modulated beam Fm1 carries information corresponding to 0 and the second modulated beam Fm2 carries information corresponding to 1; if the determined difference (ΔP ab / k-ΔR / k') takes the third expected value (ΔP 11 / k-ΔR / k'), it is recognized that the first modulated beam Fm1 carries information corresponding to 1 and the second modulated beam Fm2 carries information corresponding to 1; if the determined difference (ΔPab / k-ΔR / k') takes the fourth expected value (ΔP 00 / k-ΔR / k'), it is recognized that the first modulated beam Fm1 carries information corresponding to 0 and the second modulated beam Fm2 carries information corresponding to 0.

[0180] According to an embodiment of the method, the above-mentioned emitted and received electromagnetic beams are light beams and / or laser beams.

[0181] The following is a specific implementation example of the above-mentioned remote communication method using relevant physical-mathematical analysis.

[0182] In the following description and Figures 3 to 5 , for simplicity, the points where different signals (first composite beam electrical signal D1, second composite beam electrical signal D2, first main beam electrical signal P1, first reference beam electrical signal R1, second main beam electrical signal P2, second reference beam electrical signal R2) are located are indicated with the same names as their respective signals.

[0183] A first beam with angular momentum L1 (herein defined as the first principal beam F1) and a second beam with angular momentum L2 (herein defined as the second principal beam F2) are superimposed on the reference beam with angular momentum L0, as shown in FIG. Figure 3 The two main beams have coincident and / or overlapping frequency bands and (in the examples detailed herein) are digitally amplitude-modulated. Furthermore, the two main beams have substantially identical curvatures.

[0184] The electric field at the electric signal D1 can be described by the following analytical expression:

[0185]

[0186] where t is time, A1(t) and C1(t) are the time-varying amplitudes of the principal beams, B1 is an arbitrary non-zero amplitude of the reference beam, l1 is the topological charge of the first principal beam, l2 is the topological charge of the second principal beam, l0 is the topological charge of the reference beam, θ1 is the angular position of the first detector measured in a plane orthogonal to the composite beam propagation vector containing the first detector 1, and is the arbitrary phase due to position tilt, and and is an arbitrary phase due to interference of the propagating wavefronts.

[0187] The electric field at the electric signal D2 can be described by the following analytical expression:

[0188]

[0189] where t is time, A2(t) and C2(t) are the time-varying amplitudes of the principal beams, B2 is an arbitrary non-zero amplitude of the reference beam, l1 is the topological charge of the first principal beam, l2 is the topological charge of the second principal beam, l0 is the topological charge of the reference beam, θ2 is the angular position of the second detector measured in a plane orthogonal to the composite beam propagation vector containing the second detector 2, and is the arbitrary phase due to position tilt, and and is an arbitrary phase due to interference of the propagating wavefronts.

[0190] As already observed, the signals D1 and D2 are measured with the aid of two detectors, the reference beam being distinguished from the main beam in frequency, and thus the signals in R1, R2, P1, P2 are obtained using the following equations:

[0191] -In R1:

[0192] -In R2:

[0193] -In P1:

[0194]

[0195] -In P2:

[0196]

[0197] In R1 and R2 there is only the reference beam, and in P1 and P2 there is the superimposed main beam.

[0198] The second phase comparator 4 provides a quantity proportional to the phase difference:

[0199]

[0200] In digital modulation, the amplitude can be written as A1 = A 1max a(t), A2=A 2max a(t), C1=C 1max b(t), C2=C 2max b(t), where the functions a(t) and b(t) take the value 0 or 1, depending on the information digitally modulated in the first modulator and the second modulator, respectively.

[0201] A 1max 、C 1max is the maximum amplitude of the field or signal representing the primary beam (first and second, respectively) received by the first detector; A 2max 、C 2maxis the maximum amplitude of the field or signal representing the primary beams (first and second respectively) received by the second detector. In the transmitter it is possible to set the amplitudes of the primary beams so that they are equal, i.e.:

[0202] A 1max =C 1max , A 2max =C 2max .

[0203] The first phase comparator 3 provides a quantity which is proportional to the phase difference between the fields or signals in P1 and P2, which phase difference depends on the digital encoding of the modulation functions a(t), b(t).

[0204] All possible combinations will now be considered.

[0205] When a(t)=0 and b(t)=0, the amplitudes of the main beams cancel each other out, so the phase difference is indeterminate.

[0206] When a(t)=1 and b(t)=0, there is only the first principal bundle with angular momentum L1, so a similar relationship applies as already described above in the case of a single principal bundle:

[0207]

[0208] When a(t) = 0 and b(t) = 1, there is only a second principal beam with angular momentum L2, so a relationship similar to that already described above in the case of a single principal beam applies:

[0209]

[0210] When a(t) = 1 and b(t) = 1, there is a principal bundle, so the following relationship holds:

[0211]

[0212] Based on the above relations, it is possible to calculate all possible combinations of modulation signals in order to eliminate phase arbitrariness due to positional tilt and propagation-dependent wavefront distortions, similarly to what was described in the case of a single primary beam.

[0213] In summary, the following relationship is obtained.

[0214] When a(t)=0 and b(t)=0, the amplitudes of the main beams cancel each other out, so the phase difference is indeterminate.

[0215] When a(t) = 1 and b(t) = 0, the following results are obtained:

[0216]

[0217] When a(t) = 0 and b(t) = 1, the following results are obtained:

[0218]

[0219] When a(t) = 1 and b(t) = 1, considering that the main beam also has a substantially uniform curvature, the following results are obtained:

[0220]

[0221] The above quantities (ΔP ) can be easily distinguished simply by appropriately choosing the topological charges l0, l1, l2 of the reference beam and the two main beams (i.e., the respective orbital angular momentum). 10 / k–ΔR / k'), (ΔP 01 / k-ΔR / k')、(ΔP 11 The quantities are identifiable as being / k-Δr / k', i.e., set to three different predefined, known values. These quantities measured upon reception are therefore identifiable and are indicative of the modulation value 0 or 1 applied to each of the two primary beams. The information encoded in these quantities can thus be decoded, i.e., demodulated and identified.

[0222] Furthermore, these quantities are advantageously made independent of phase differences due to positional tilt and independent of distortions of the propagating wavefront, which can be eliminated due to the presence of the reference beam (as already noted above).

[0223] Possible examples of choices of topological charge values ​​are:

[0224] l0=0, l1=0, l2=2.

[0225] Other combinations are clearly detectable.

[0226] There remains a state to be identified, a(t) = 0, b(t) = 0, the phase of which is undetermined (as shown above). This state is easily identified because it is the only combination in which the amplitudes of the fields or signals received by the two main beams are canceled. Therefore, when the signal detected at point Q3 (by means of Figure 4 When the intensity or power of the detector 16 shown in FIG. 1 is below a predefined threshold, the state a(t) = 0, b(t) = 0 is deterministically identified. Alternatively, both the first composite beam electrical signal D1 and the second composite beam electrical signal D2 can be monitored to identify the situation where both signals are below their respective predefined thresholds.

[0227] The following is a specific implementation example of the above-mentioned method of remote communication based on orbital angular momentum modulation and using relevant physical-mathematical analysis.

[0228] Angular momentum modulation can be described using parameters similar to those already developed for the case of digital amplitude modulation.

[0229] The modulation functions a(t) and b(t) take the values ​​0 or 1, depending on the information digitally modulated in the first modulator and the second modulator, respectively. Such modulation functions determine the discrete variables of the angular momentum of the first electromagnetic radiation beam and the at least one second electromagnetic radiation beam, respectively, according to the binary values ​​they take, i.e., the functions L1 and L2, depending on the values ​​a(t) and b(t) take:

[0230] L1=L1(a(t)), L2=L2(b(t))

[0231] That is, equivalently referring to the topological charge: l1=l1(a(t)), l2=l2(b(t)).

[0232] Therefore, the signal present in R1, R2, P1, and P2 can be expressed as:

[0233] -In R1:

[0234] -In R2:

[0235] -In P1:

[0236]

[0237] -In P2:

[0238]

[0239] In R1 and R2 there is only a reference beam; in P1 and P2 there is a superimposed main beam.

[0240] The second phase comparator 4 provides a quantity proportional to the phase difference (as in the general case):

[0241]

[0242] The first phase comparator 3 provides a quantity which is proportional to the phase difference between the fields or signals in P1 and P2, which phase difference depends on the digital encoding of the modulation functions a(t), b(t).

[0243] Considering all possible combinations, we get the following results:

[0244]

[0245] The combination is determined by the indices a, b and the corresponding values ​​taken by the functions a(t) and b(t).

[0246] Then, the difference ΔP ab / k-ΔR / k' is calculated for all possible combinations of modulation signals with the aid of the following formula in order to eliminate the phase arbitrariness due to positional inclination and propagation-related wavefront distortion:

[0247]

[0248] The topological charge values ​​l0, l1(0), l1(1), l2(0), l2(1) or their corresponding orbital angular momentum can be chosen so that the corresponding quantity (ΔP 00 / k-ΔR / k')、(ΔP 01 / k-ΔR / k')、(ΔP 10 / k-ΔR / k')、(ΔP 11 / k-ΔR / k') are different from each other and are therefore identifiable to allow decoding (demodulation) of the coded (modulated) information.

[0249] Furthermore, the above quantities are independent of phase differences due to positional tilts and distortions of the propagating wavefront, which can be eliminated due to the presence of the reference beam.

[0250] An example of the selection of topological charge values ​​is l0=0, l1(0)=0, l1(1)=1, l2(0)=0, l2(1)=2, which yields:

[0251]

[0252] As can be seen, the above four quantities are different and can therefore be identified.

[0253] Similar to the examples reported above, other value assignments are obviously possible.

[0254] It should be noted that angular momentum modulation is similar to amplitude modulation in many respects, Figure 3 and Figure 4 The block diagram shown in also applies to angular momentum modulation, the only significant difference being that the modulator modulates angular momentum instead of amplitude. Furthermore, in this case, Figure 4 and Figure 5 A threshold detector is not required.

[0255] refer to Figure 1 and Figure 2 , a system for transmitting and receiving a beam of electromagnetic radiation is now described, the system being suitable for determining the orbital angular momentum of the received beam of electromagnetic radiation.

[0256] Such a system comprises means 5 for generating a main electromagnetic radiation beam F1, means 6 for generating a reference electromagnetic radiation beam F0, means for generating a composite electromagnetic radiation beam Q1 (e.g. Figure 1 ) and emits a composite electromagnetic radiation beam Q1 (as shown in FIG. Figure 1, a device 14 for receiving a composite electromagnetic radiation beam, a first beam detection device 1, a second beam detection device 2, a first frequency identification device 8, a second frequency identification device 9 and a device 10 for determining an orbital angular momentum (as shown in FIG. Figure 2 shown).

[0257] The means 5 for generating a main electromagnetic radiation beam is configured to generate a main electromagnetic radiation beam F1 characterized by a first orbital angular momentum L1 , a first spectrum in a first frequency band and a first beam curvature radius.

[0258] The device 6 for generating a reference electromagnetic radiation beam is configured to generate a reference electromagnetic radiation beam F0, which is characterized by a second orbital angular momentum L0, a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius substantially consistent with the first beam curvature radius.

[0259] The device for generating a composite electromagnetic radiation beam 7 and the device for emitting a composite electromagnetic radiation beam 14 are configured to generate a composite electromagnetic radiation beam Q1 comprising a superposition of the main beam F1 and the reference beam F0 and to emit the generated composite electromagnetic radiation beam Q1.

[0260] The device for receiving a composite electromagnetic radiation beam includes: a first beam detection device 1 located in a first position, the first beam detection device being configured to generate a first composite beam electrical signal D1, the first composite beam electrical signal representing the intensity of the electric field, and / or magnetic field, and / or electromagnetic radiation of the composite beam in the first position; and a second beam detection device 2 located in a second position, the second beam detection device being configured to generate a second composite beam electrical signal D2, the second position being different from the above-mentioned first position, the second composite beam electrical signal representing the intensity of the electric field, and / or magnetic field, and / or electromagnetic radiation of the composite beam in the second position.

[0261] The first frequency identification device 8 is configured to perform frequency identification of the first composite beam electrical signal D1 to obtain a first main beam electrical signal P1 and a first reference beam electrical signal R1, wherein the first main beam electrical signal P1 represents the electric field, and / or magnetic field, and / or intensity attributed to the main beam in the first position, and the first reference beam electrical signal R1 represents the electric field, and / or magnetic field, and / or intensity attributed to the reference beam in the first position.

[0262] The second frequency identification device 9 is configured to perform frequency identification of the second composite beam electrical signal to obtain a second main beam electrical signal P2 and a second reference beam electrical signal R2, wherein the second main beam electrical signal P2 represents the electric field, and / or magnetic field, and / or intensity attributed to the main beam in the second position, and the second reference beam electrical signal R2 represents the electric field, and / or magnetic field, and / or intensity attributed to the reference beam in the second position.

[0263] The device 10 for determining the orbital angular momentum is configured to determine the orbital angular momentum L1 of the main electromagnetic radiation beam, and / or the spatial phase variable of the main electromagnetic radiation beam attributed to the main beam orbital angular momentum L1 based on the above-mentioned main beam first electrical signal P1, second main beam electrical signal P2, first reference beam electrical signal R1 and second reference beam electrical signal R2.

[0264] According to different implementation options, the system is configured to perform the method for transmitting and receiving a beam of electromagnetic radiation according to any of the embodiments described above.

[0265] According to an embodiment of the system, the means 5 for generating the main electromagnetic radiation beam and the means 6 for generating the reference electromagnetic radiation beam comprise one or more electromagnetic beam sources or emitters known per se (eg, in an implementation option, lasers).

[0266] According to an embodiment option, the device 5 for generating the main electromagnetic radiation beam further comprises an amplitude, and / or frequency, and / or phase modulator 50, and / or one or more angular momentum modulators 50 (for example, such angular momentum modulator 50 may be a spatial light modulator).

[0267] According to an embodiment of the system, the means 7 for generating a composite electromagnetic radiation beam comprises an electromagnetic beam combiner (eg a beam combiner) having two or more inputs and outputs known per se.

[0268] According to one embodiment of the system, the first beam detection means 1 comprises one or more diaphragms (optical openings), or an antenna, or a group of antennas, or any other electromagnetic beam receiver known per se, suitable for operating at the frequencies of the first and second beams. For example, the means 14 for transmitting the electromagnetic beam comprises one or more transmitting antennas.

[0269] According to an embodiment of the system, the second beam detection means 2 comprise one or more diaphragms (optical openings), or an antenna, or a set of antennas, or any other electromagnetic beam receiver known per se, adapted to operate at the frequencies of the first and second beams.

[0270] According to various embodiments, the first frequency identification means 8 and the second frequency identification means 9 may comprise frequency filters known per se.

[0271] According to an embodiment of the system, the device 10 for determining orbital angular momentum comprises: at least two phase comparators 3, 4 and at least one processing device 15, and the device for determining orbital angular momentum is configured to derive the orbital angular momentum based on the output signals from the phase comparators by means of processing (for example, according to the formula shown above).

[0272] According to one embodiment of the system, the device 10 for determining orbital angular momentum comprises: at least two correlators 11, 12 and at least one processing device 15, and the device for determining orbital angular momentum is configured to derive the orbital angular momentum based on the output signals from the correlators by means of processing (for example, according to the formula shown above).

[0273] refer to Figure 5 , further details regarding implementation options involving the use of correlators are provided further herein.

[0274] In this case, instead of using a phase comparator that provides a value proportional to the phase difference ΔP or ΔR, a correlator that provides a value proportional to the cosine of the phase difference cos(ΔP) or cos(ΔR) is used. The phase difference is then determined by the inverse function:

[0275] ΔP=arccos[cos(ΔP)]

[0276] ΔR=arccos[cos(ΔR)]

[0277] The correlation can be determined by means of the direct product of the fields or signals represented by P1 and P2 or R1 and R2.

[0278] Alternatively, the intensity I at P1 and P2 can be measured by P1 and I P2 The field between R1 and R2 has an intensity of I R1 and I R2 The average interference intensity between the fields The interference to determine the correlation, knowing that:

[0279] cos(ΔP)=( -I P1 -I P2 ) / (2(I P1 I P2 ) 1 / 2 )

[0280] cos(ΔR)=( -I R1 -I R2 ) / (2(I R1 I R2 ) 1 / 2 )

[0281] According to an embodiment of the above system, the above-mentioned emitted and received electromagnetic beams are light beams and / or laser beams.

[0282] refer to Figure 3 and Figure 4 , a system for telecommunication of signals modulated according to any known modulation technique and grouped by means of orbital angular momentum variable multiplexing will now be described.

[0283] Such a system comprises means 5 , 6 for generating an electromagnetic beam, modulation means 50 , beam combining and / or superposition means 7 , transmitting means 14 , beam receiving means 1 , 2 , 8 , 9 , phase determination means 20 and processing means 15 .

[0284] The means for generating an electromagnetic beam 5 , 6 are configured to generate a first beam F1 of electromagnetic radiation characterized by a first orbital angular momentum L1 and to generate at least one second beam F2 of electromagnetic radiation characterized by at least one corresponding third orbital angular momentum L2 .

[0285] The first electromagnetic radiation beam F1 and the at least one second electromagnetic radiation beam F2 have respective spectra in the same first frequency band and also have respective radii of curvature that substantially correspond to the value of the first beam radius of curvature.

[0286] The means 5, 6 for generating an electromagnetic beam are further configured to generate a reference electromagnetic radiation beam F0, which is characterized by a second orbital angular momentum L0, a second spectrum in a second frequency band different from the above-mentioned first frequency band, and a second beam curvature radius, the second beam curvature radius having a value substantially consistent with the above-mentioned first beam curvature radius value.

[0287] The modulation device 50 is configured to modulate a first piece of information to be transmitted, represented by a first modulation function a(t), on a first electromagnetic radiation beam F1 by means of any amplitude, and / or phase, and / or frequency modulation technique to obtain a first modulated beam Fm1; and to modulate at least one second piece of information to be transmitted, represented by a second modulation function b(t), on at least one second electromagnetic radiation beam F2 by means of any amplitude, and / or phase, and / or frequency modulation technique to obtain a second modulated beam Fm2.

[0288] The beam combining and / or superposition device 7 is configured to superimpose and / or combine the above-mentioned reference beam F0, the first modulated beam Fm1 and the second modulated beam Fm2 to generate a composite electromagnetic radiation beam Q1, which contains the superposition of the reference beam and the main beam, and further contains the superposition of the above-mentioned first modulated beam Fm1 and at least one second modulated beam Fm2.

[0289] The transmitting device 14 is configured to transmit the composite electromagnetic radiation beam generated as described above.

[0290] The device for receiving a composite electromagnetic radiation beam comprises a first beam detection device 1 , a second beam detection device 2 , a first frequency discrimination device 8 , and a second frequency discrimination device 9 .

[0291] The first beam detection device 1 is located in a first position and is configured to generate a first composite beam electrical signal D1 representing the intensity of the electric field and / or magnetic field and / or electromagnetic radiation of the composite beam in the first position.

[0292] The second beam detection device 2 is located in a second position different from the first position and is configured to generate a second composite beam electrical signal D2 representing the intensity of the electric field and / or magnetic field and / or electromagnetic radiation of the composite beam in the second position.

[0293] The first frequency identification device 8 is configured to perform frequency identification of the first composite beam electrical signal D1 to obtain a first main beam electrical signal P1 and a first reference beam electrical signal R1, wherein the first main beam electrical signal represents the electric field, and / or magnetic field, and / or intensity attributed to the main beam in the first position, and the first reference beam electrical signal represents the electric field, and / or magnetic field, and / or intensity attributed to the reference beam in the first position.

[0294] The second frequency identification device 9 is configured to perform frequency identification of the second composite beam electrical signal to obtain a second main beam electrical signal P2 and a second reference beam electrical signal R2, wherein the second main beam electrical signal represents the electric field, and / or magnetic field, and / or intensity attributed to the main beam in the second position, and the second reference beam electrical signal represents the electric field, and / or magnetic field, and / or intensity attributed to the reference beam in the second position.

[0295] The phase determining device 20 is configured to determine the phases of the first main beam electrical signal P1 and the second main beam electrical signal P2 and also to determine the phases of the first reference beam electrical signal R1 and the second reference beam electrical signal R2.

[0296] The phase determining device 20 is further configured to determine a first phase difference value ΔP corresponding to the difference between the phase of the first main beam electrical signal P1 and the phase of the second main beam electrical signal P2. ab , where the first phase difference ΔP ab Depending on the values ​​of the first modulation function a(t) and the second modulation function b(t), a second phase difference value ΔR corresponding to the difference between the phase of the first reference beam electrical signal R1 and the phase of the second reference beam electrical signal R2 is determined; further, from the first phase difference value ΔP ab Divide by the wave number k minus the second phase difference ΔR divided by the wave number k' to obtain the difference Q2 = ΔP ab / k–ΔR / k'. The first wave number k is the wave number corresponding to the main beam and is defined as k = 2π / λ, where λ is the wavelength of the main beam belonging to the first frequency band. The second wave number k' is the wave number corresponding to the reference beam and is defined as k' = 2π / λ', where λ' is the wavelength of the reference beam belonging to the second frequency band.

[0297] The above difference Q2 = ΔP ab / k-ΔR / k' represents the combination of the values ​​taken by the first modulation function a(t) and the second modulation function b(t), and is independent of the positional inclination condition between the first detector 1 and the second detector 2, and is independent of the phase variable caused by the interference to which the transmitted composite beam is subjected before reception.

[0298] The processing device 15 is configured to determine the difference Q2 = ΔP based on the above determination. ab / k-ΔR / k′ to demultiplex and demodulate the modulation information on each of the first modulation beam Fm1 and the at least one second modulation beam Fm2.

[0299] According to various embodiments, the system is configured to perform the method for electromagnetic radiation beam telecommunication according to any of the above embodiments.

[0300] According to an embodiment of the system, the means 5 , 6 for generating an electromagnetic beam comprise one or more electromagnetic beam sources or emitters known per se (for example, in an implementation option, lasers).

[0301] According to one embodiment of the system, the modulation means 50 comprise amplitude, and / or frequency, and / or phase, and / or angular momentum modulators known per se.

[0302] According to one embodiment of the system, the first beam detection device 1 and the second beam detection device 2 comprise one or more diaphragms (optical openings), or an antenna, or a group of antennas, or any other electromagnetic beam receiver known per se, each adapted to operate at the frequency of the first beam and the second beam.

[0303] According to one embodiment of the system, the first frequency discrimination means 8 and the second frequency discrimination means 9 comprise frequency filters known per se.

[0304] According to one embodiment of the system, the phase determination device 20 comprises at least two phase comparators 3 , 4 known per se.

[0305] According to an embodiment of the system, the first frequency discrimination means and the second frequency discrimination means comprise per se known correlators 11, 12. With regard to such correlators, the same considerations apply as above with reference to the system for transmitting and receiving an electromagnetic beam.

[0306] According to one embodiment of the system, the processing device 15 includes one or more processors known per se, and related software.

[0307] According to an embodiment of the above system, the above-mentioned emitted and received electromagnetic beams are light beams and / or laser beams.

[0308] It can be noted that the purpose of the present invention is entirely achieved through the above-mentioned system and method, relying on the functional and structural characteristics of the above-mentioned system and method.

[0309] In fact, the system and method for transmitting and receiving an electromagnetic beam described above enable accurate and reliable detection of the orbital angular momentum of the received beam in a manner that is independent of the position inclination of the receiver and independent of the distortions undergone by the beam during propagation.

[0310] This is achieved by means of a dual spatial detection at two different points of a composite beam which, in addition to the beam to be studied, also includes a reference beam.

[0311] The possibility to accurately and reliably detect the orbital angular momentum of a received beam is in turn advantageously suitable for a variety of different applications, including, for example, characterization of the beam and utilization of the angular momentum variable for telecommunication purposes.

[0312] With reference to telecommunication applications, the method and system of the present invention allow the use of orbital angular momentum variables as an additional degree of freedom, which is advantageous for both signal modulation and signal multiplexing.

[0313] In particular, orbital angular momentum provides an additional level of multiplexing (with its attendant obvious advantages), allowing signals that are identical from the perspective of other multiplexing variables (e.g., time or frequency) to be grouped and distinguished based on their different orbital angular momentum.

[0314] Those skilled in the art may modify and adjust the embodiments of the above-described systems and methods to meet possible needs without departing from the scope of the appended claims, and replace them with other functionally equivalent elements. Each feature described as belonging to a possible embodiment can be implemented without considering the other embodiments described.

Claims

1. A method for transmitting and receiving an electromagnetic radiation beam, said method being adapted to determine the orbital angular momentum of the received electromagnetic radiation beam, said method comprising the steps of: - generating at least one main electromagnetic radiation beam (F1) characterized by a first orbital angular momentum (L1), a first spectrum in a first frequency band, and a first beam curvature radius; - generating a reference electromagnetic radiation beam (F0) characterized by a second orbital angular momentum (L0), a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius corresponding to the first beam curvature radius; - generating a composite electromagnetic radiation beam (Q1) comprising a superposition of said at least one main electromagnetic radiation beam (F1) and said reference electromagnetic radiation beam (F0); - emitting said generated composite electromagnetic radiation beam (Q1); - receiving the composite electromagnetic radiation beam by means of a first beam detector (1) located in a first position to generate a first composite beam electrical signal (D1), the first composite beam electrical signal being representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the first position; - receiving the composite electromagnetic radiation beam by means of a second beam detector (2) located in a second position different from the first position to generate a second composite beam electrical signal (D2), the second composite beam electrical signal being representative of the electric field and / or magnetic field of the composite electromagnetic radiation beam and / or the intensity of the received electromagnetic radiation in the second position; - performing frequency discrimination of the first composite beam electrical signal (D1) to obtain a first main beam electrical signal (P1) and a first reference beam electrical signal (R1), the first main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main electromagnetic radiation beam in the first position, and the first reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the first position; - performing frequency discrimination of the second composite beam electrical signal (D2) to obtain a second main beam electrical signal (P2) and a second reference beam electrical signal (R2), the second main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main electromagnetic radiation beam in the second position, and the second reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the second position; -Determine the orbital angular momentum (L1) of the main electromagnetic radiation beam and / or the spatial phase variable of the main electromagnetic radiation beam attributed to the orbital angular momentum (L1) of the main electromagnetic radiation beam based on the first main beam electrical signal (P1), the second main beam electrical signal (P2), the first reference beam electrical signal (R1) and the second reference beam electrical signal (R2).

2. The method according to claim 1, wherein The steps to determine include: - determining a first phase difference value (ΔP), the first phase difference value corresponding to the difference between the phase of the first main beam electrical signal (P1) and the phase of the second main beam electrical signal (P2), - determining a second phase difference value (ΔR) corresponding to a difference between a phase of the first reference beam electrical signal (R1) and a phase of a second reference beam electrical signal (R2), - subtracting the second phase difference value (ΔR) divided by the second wave number (k') from the first phase difference value (ΔP) divided by the first wave number (k) to obtain a difference value (Q2=ΔP / k−ΔR / k'), said difference value being independent of a positional inclination condition between the first beam detector and the second beam detector, being derived from the relative positions of the first beam detector and the second beam detector with respect to beam propagation, and being independent of phase variations due to disturbances to which the transmitted composite electromagnetic radiation beam was subjected prior to reception, wherein the first wave number (k) is the wave number corresponding to the main electromagnetic radiation beam and is defined as k=2π / λ, λ being the wavelength of the main electromagnetic radiation beam, and wherein the second wave number (k') is the wave number corresponding to the reference electromagnetic radiation beam and is defined as k'=2π / λ', λ' being the wavelength of the reference electromagnetic radiation beam; - Based on said difference obtained (Q2 = ΔP / k - ΔR / k'), determining said orbital angular momentum of said main beam of electromagnetic radiation.

3. The method according to claim 2, wherein: The step of determining the orbital angular momentum of the main beam of electromagnetic radiation comprises: - determining the orbital angular momentum of the main electromagnetic radiation beam according to the following formula ΔP / k–ΔR / k'∝(L1 / k-L0 / k')(θ2-θ1) wherein θ1 is the angular position of the first beam detector measured on a plane orthogonal to the composite beam propagation vector containing the first beam detector, and θ2 is the angular position of the second beam detector measured on a plane orthogonal to the composite beam propagation vector containing the second beam detector.

4. The method according to claim 2, wherein: - the step of determining the first phase difference value (ΔP) comprises: comparing the phase of the first main beam electrical signal (P1) with the phase of the second main beam electrical signal (P2) by means of a first phase comparator (3); - the step of determining the second phase difference value (ΔR) comprises comparing the phase of the first reference beam electrical signal (R1) with the phase of the second reference beam electrical signal (R2) by means of a second phase comparator (4).

5. The method according to claim 2, wherein: - the step of determining the first phase difference value (ΔP) comprises: performing a correlation operation between the first main beam electrical signal (P1) and the second main beam electrical signal (P2); - the step of determining the second phase difference value (ΔR) comprises: performing a correlation operation between the first reference beam electrical signal (R1) and the second reference beam electrical signal (R2).

6. A method according to any one of the preceding claims, wherein The orbital angular momentum of the reference beam of electromagnetic radiation is always known.

7. The method according to claim 6, wherein: The orbital angular momentum of the reference electromagnetic radiation beam takes a constant value L0=0.

8. The method according to any one of claims 1 to 5, wherein The first position of the first beam detector (1) and the second position of the second beam detector (2) are fixed and constant and are different from the position of a singularity of a vortex of the composite electromagnetic radiation beam.

9. The method according to any one of claims 1 to 5, wherein The first position of the first beam detector (1) and / or the second position of the second beam detector (2) are movable, and the mutual relationship between the first position and the second position is always known.

10. The method according to any one of claims 1 to 5, wherein The second frequency band is quasi-single frequency.

11. The method according to claim 10, wherein The second frequency band is adjacent to the first frequency band.

12. The method according to any one of claims 1 to 5, wherein: The step of performing frequency identification of the first composite beam electrical signal or the second composite beam electrical signal comprises: - perform frequency filtering; or - Frequency separation is performed with the help of heterodyning techniques or other frequency separation methods.

13. The method according to any one of claims 1 to 5, wherein: The at least one main beam of electromagnetic radiation is unmodulated.

14. The method according to any one of claims 1 to 5, wherein: The at least one main electromagnetic radiation beam is amplitude modulated, and / or phase modulated, and / or frequency modulated, and / or orbital angular momentum modulated.

15. The method according to any one of claims 1 to 5, wherein: The emitted and received electromagnetic beams are light beams and / or laser beams.

16. A method for telecommunication of signals modulated according to any known modulation technique, said modulated signals being grouped by multiplexing in orbital angular momentum variables, said method comprising the steps of: - generating a first beam (F1) of electromagnetic radiation characterized by a first orbital angular momentum (L1), and generating at least one second beam (F2) of electromagnetic radiation characterized by a corresponding at least one third orbital angular momentum (L2), wherein the first electromagnetic radiation beam (F1) and the at least one second electromagnetic radiation beam (F2) have respective spectra in the same first frequency band and further have respective radii of curvature corresponding to the value of the first beam radius of curvature; - modulating a first piece of information to be transmitted on said first beam of electromagnetic radiation (F1) by means of any modulation technique, so as to obtain a first modulated beam (Fm1), said first piece of information to be transmitted being represented by a first modulation function a(t); - modulating, by means of any modulation technique, at least one second piece of information to be transmitted on said at least one second beam of electromagnetic radiation (F2) to obtain a second modulated beam (Fm2), said second piece of information to be transmitted being represented by a second modulation function b(t); - generating a reference electromagnetic radiation beam (F0) characterized by a second orbital angular momentum (L0), a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius having a value corresponding to the value of the first beam curvature radius; - superimposing and / or combining the reference electromagnetic radiation beam (F0), the first modulated beam (Fm1) and the second modulated beam (Fm2) to produce a composite electromagnetic radiation beam (Q1), the composite electromagnetic radiation beam comprising a superposition of the reference electromagnetic radiation beam (F0) and a main beam, and further comprising a superposition of the first modulated beam (Fm1) and at least one second modulated beam (Fm2); - emitting said generated composite electromagnetic radiation beam (Q1); - receiving the composite electromagnetic radiation beam by means of a first beam detector (1) located in a first position to generate a first composite beam electrical signal (D1), the first composite beam electrical signal being representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the first position; - receiving the composite electromagnetic radiation beam by means of a second beam detector (2) located at a second position different from the first position to generate a second composite beam electrical signal (D2), the second composite beam electrical signal being representative of the electric field and / or magnetic field of the composite electromagnetic radiation beam and / or the intensity of the received electromagnetic radiation in the second position; - performing frequency discrimination of the first composite beam electrical signal (D1) to obtain a first main beam electrical signal (P1) and a first reference beam electrical signal (R1), the first main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main beam in the first position, the first reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the first position; - performing frequency discrimination of the second composite beam electrical signal (D2) to obtain a second main beam electrical signal (P2) and a second reference beam electrical signal (R2), the second main beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the main beam in the second position, the second reference beam electrical signal representing the electric field and / or magnetic field and / or intensity attributable to the reference electromagnetic radiation beam in the second position; - determining the phase of the first main beam electrical signal (P1) and the phase of the second main beam electrical signal (P2); - determining the phase of the first reference beam electrical signal (R1) and the phase of the second reference beam electrical signal (R2); - Determine the first phase difference (ΔP ab ), the first phase difference value corresponds to the difference between the phase of the first main beam electrical signal (P1) and the phase of the second main beam electrical signal (P2), the first phase difference value (ΔP ab ) depends on the values ​​taken by the first modulation function a(t) and the second modulation function b(t); - determining a second phase difference value (ΔR), the second phase difference value corresponding to the difference between the phase of the first reference beam electrical signal (R1) and the phase of the second reference beam electrical signal (R2); - From the first phase difference value (ΔP ab ) divided by the first wave number k minus the second phase difference (ΔR) divided by the second wave number k' to obtain the difference (Q2 = ΔP ab / k–ΔR / k'), wherein the first wave number k is the wave number corresponding to the main beam and is defined as k=2π / λ, λ being the wavelength of the main beam, and wherein the second wave number k′ is the wave number corresponding to the reference electromagnetic radiation beam and is defined as k′=2π / λ′, λ′ being the wavelength of the reference electromagnetic radiation beam, The difference (Q2 = ΔP ab / k–ΔR / k') represents a combination of the values ​​taken by the first modulation function a(t) and the second modulation function b(t), independently of the positional inclination conditions between the first beam detector and the second beam detector, and independently of phase variations caused by disturbances to which the transmitted composite electromagnetic radiation beam is subjected before reception; - Based on the difference (Q2 = ΔP ab / k−ΔR / k′), demultiplexing and demodulating information modulated on each of the first modulated beam (Fm1) and the at least one second modulated beam (Fm2).

17. The method according to claim 16, wherein The number of modulation beams of orbital angular momentum multiplexing is greater than two.

18. The method according to any one of claims 16 or 17, wherein digitally amplitude modulating the first electromagnetic radiation beam (F1) and the at least one second electromagnetic radiation beam (F2) according to the amplitude of the first modulation function a(t) and the amplitude of the at least one second modulation function b(t), And wherein, the difference (Q2 = ΔP ab / k−ΔR / k′) can take a plurality of expected values, each expected value representing a corresponding combination of digital amplitude values ​​taken by the first modulation function a(t) and the at least one second modulation function b(t).

19. The method according to claim 18, wherein: - said first beam of electromagnetic radiation (F1) and said at least one second beam of electromagnetic radiation (F2) are digitally amplitude modulated in a binary manner, and said amplitude of said first modulation function a(t) and said amplitude of said at least one second modulation function b(t) can take logical values ​​0 or 1; - the method comprises the further step of detecting a received power or intensity (Q3) corresponding to the first main beam electrical signal (P1) or the second main beam electrical signal (P2) and comparing the received power or intensity with a minimum threshold; - the determined difference (Q2 = ΔP ab / k–ΔR / k') can take the first expected value (ΔP 10 / k–ΔR / k'), or the second expected value (ΔP 01 / k–ΔR / k'), or the third expected value (ΔP 11 / k–ΔR / k'), the first expected value depends on the first orbital angular momentum (L1), the second expected value depends on the third orbital angular momentum (L2), and the third expected value depends on a combination of the first orbital angular momentum and the second orbital angular momentum; - The steps of demodulating, demultiplexing and demodulating the modulated information include: - If the determined difference (ΔP ab / k–ΔR / k') takes the first expected value (ΔP 10 / k–ΔR / k'), it is identified that the first modulated beam (Fm1) carries information corresponding to 1 and the second modulated beam (Fm2) carries information corresponding to 0; - If the determined difference (ΔP ab / k–ΔR / k') takes the second expected value (ΔP 01 / k–ΔR / k'), it is identified that the first modulated beam (Fm1) carries information corresponding to 0 and the second modulated beam (Fm2) carries information corresponding to 1; - If the determined difference (ΔP ab / k–ΔR / k') takes the third expected value (ΔP 11 / k–ΔR / k'), it is identified that the first modulated beam (Fm1) carries information corresponding to 1 and the second modulated beam (Fm2) carries information corresponding to 1; - if the received power or strength (Q3) is below said minimum threshold, identifying that said first modulated beam (Fm1) carries information corresponding to 0 and that said second modulated beam (Fm2) carries information corresponding to 0.

20. The method according to any one of claims 16 or 17, wherein The first electromagnetic radiation beam (F1) and the at least one second electromagnetic radiation beam (F2) are digitally angular momentum modulated, wherein the angular momentum of the first electromagnetic radiation beam (F1) takes two different discrete values ​​based on a first modulation function a(t), and the angular momentum of the at least one second electromagnetic radiation beam (F2) takes two different discrete values ​​based on a corresponding at least one second modulation function b(t), And wherein, the difference (Q2 = ΔP ab / k−ΔR / k′) can take a plurality of expected values, each expected value representing a corresponding combination of digital amplitude values ​​taken by the first modulation function a(t) and the at least one second modulation function b(t).

21. The method according to claim 20, wherein: - the amplitudes of the first modulation function a(t) and the at least one second modulation function b(t) can take logical values ​​0 or 1; - The determined difference (ΔP ab / k–ΔR / k') can: When the first modulation function a(t) takes a value of 1 and the second modulation function takes a value of 0, the first expected value (ΔP 10 / k–ΔR / k'); or, when the first modulation function a(t) takes a value of 0 and the second modulation function takes a value of 1, take the second expected value (ΔP 01 / k–ΔR / k'); or, when the first modulation function a(t) takes a value of 1 and the second modulation function takes a value of 1, take a third expected value (ΔP 11 / k–ΔR / k'); or, when the first modulation function a(t) takes a value of 0 and the second modulation function takes a value of 0, take a fourth expected value (ΔP 00 / k–ΔR / k'); - The steps of demodulating, demultiplexing and demodulating the modulated information include: - If the determined difference (ΔP ab / k–ΔR / k') takes the first expected value (ΔP 10 / k–ΔR / k'), it is identified that the first modulated beam (Fm1) carries information corresponding to 1 and the second modulated beam (Fm2) carries information corresponding to 0; - If the determined difference (ΔP ab / k–ΔR / k') takes the second expected value (ΔP 01 / k–ΔR / k'), it is identified that the first modulated beam (Fm1) carries information corresponding to 0 and the second modulated beam (Fm2) carries information corresponding to 1; - If the determined difference (ΔP ab / k–ΔR / k') takes the third expected value (ΔP 11 / k–ΔR / k'), it is identified that the first modulated beam (Fm1) carries information corresponding to 1 and the second modulated beam (Fm2) carries information corresponding to 1; - If the determined difference (ΔP ab / k–ΔR / k') takes the fourth expected value (ΔP 00 / k−ΔR / k′), it is identified that the first modulated beam (Fm1) carries information corresponding to 0 and the second modulated beam (Fm2) carries information corresponding to 0.

22. The method according to claim 16 or 17, wherein: The emitted and received electromagnetic beams are light beams and / or laser beams.

23. A system for transmitting and receiving a beam of electromagnetic radiation, the system being adapted to determine the orbital angular momentum of the received beam of electromagnetic radiation, the system comprising: - means (5) for generating a main electromagnetic radiation beam, the means for generating a main electromagnetic radiation beam being configured to generate a main electromagnetic radiation beam (F1) characterized by a first orbital angular momentum (L1), a first spectrum in a first frequency band, and a first beam curvature radius; - means (6) for generating a reference electromagnetic radiation beam, the means for generating a reference electromagnetic radiation beam being configured to generate a reference electromagnetic radiation beam (F0) characterized by a second orbital angular momentum (L0), a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius corresponding to the first beam curvature radius; - means (7) for generating a composite electromagnetic radiation beam, and means (14) for emitting the composite electromagnetic radiation, said means for generating a composite electromagnetic radiation beam being configured to generate a composite electromagnetic radiation beam (Q1) comprising a superposition of said main electromagnetic radiation beam (F1) and a reference electromagnetic radiation beam (F0), said means for emitting the composite electromagnetic radiation being configured to emit said generated composite electromagnetic radiation beam (Q1); - means for receiving said composite beam of electromagnetic radiation, comprising: a first beam detection device (1) located in a first position and configured to generate a first composite beam electrical signal (D1) representing the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the first position; a second beam detection device (2) located in a second position different from the first position and configured to generate a second composite beam electrical signal (D2), the second composite beam electrical signal being representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the second position; a first frequency discrimination device (8) configured to perform frequency discrimination of the first composite beam electrical signal (D1) to obtain a first main beam electrical signal (P1) and a first reference beam electrical signal (R1), the first main beam electrical signal representing the electric field, and / or magnetic field, and / or intensity attributable to the main electromagnetic radiation beam in the first position, and the first reference beam electrical signal representing the electric field, and / or magnetic field, and / or intensity attributable to the reference electromagnetic radiation beam in the first position; a second frequency discrimination device (9) configured to perform frequency discrimination of the second composite beam electrical signal to obtain a second main beam electrical signal (P2) and a second reference beam electrical signal (R2), the second main beam electrical signal representing the electric field, and / or magnetic field, and / or intensity attributable to the main electromagnetic radiation beam in the second position, and the second reference beam electrical signal representing the electric field, and / or magnetic field, and / or intensity attributable to the reference electromagnetic radiation beam in the second position; - A device (10) for determining orbital angular momentum, the device for determining orbital angular momentum being configured to determine the orbital angular momentum (L1) of the main electromagnetic radiation beam and / or a spatial phase variable of the main electromagnetic radiation beam attributable to the orbital angular momentum (L1) of the main electromagnetic radiation beam based on the first main beam electrical signal (P1), the second main beam electrical signal (P2), the first reference beam electrical signal (R1) and the second reference beam electrical signal (R2).

24. A system for telecommunication of signals modulated according to any known modulation technique, said modulated signals being grouped by means of orbital angular momentum variable multiplexing, said system comprising: - means (5, 6) for generating an electromagnetic beam, said means for generating an electromagnetic beam being configured to: - generating a first electromagnetic radiation beam (F1) characterized by a first orbital angular momentum (L1), and generating at least one second electromagnetic radiation beam (F2) characterized by a corresponding at least one third orbital angular momentum (L2), wherein the first electromagnetic radiation beam (F1) and the at least one second electromagnetic radiation beam (F2) both have respective spectra in the same first frequency band and also have respective radii of curvature corresponding to the value of the first beam radius of curvature; - generating a reference electromagnetic radiation beam (F0) characterized by a second orbital angular momentum (L0), a second spectrum in a second frequency band different from the first frequency band, and a second beam curvature radius having a value corresponding to the value of the first beam curvature radius; - a modulation device (50), said modulation device being configured to: - modulating the first piece of information to be transmitted on said first beam of electromagnetic radiation (F1) by means of any amplitude, and / or phase, and / or frequency modulation technique, so as to obtain a first modulated beam (Fm1), said first piece of information to be transmitted being represented by a first modulation function a(t); - modulating at least one second piece of information to be transmitted on said at least one second beam of electromagnetic radiation (F2) by means of any amplitude and / or phase and / or frequency modulation technique, so as to obtain a second modulated beam (Fm2), said at least one second piece of information to be transmitted being represented by a second modulation function b(t); - beam combining and / or superposition means (7) configured to superpose and / or combine the reference electromagnetic radiation beam (F0), the first modulated beam (Fm1) and the second modulated beam (Fm2) to produce a composite electromagnetic radiation beam (Q1), the composite electromagnetic radiation beam comprising a superposition of the reference electromagnetic radiation beam (F0) and the main beam and, in turn, a superposition of the first modulated beam (Fm1) and at least one second modulated beam (Fm2); - a transmitting device (14) configured to transmit the generated composite electromagnetic radiation beam (Q1); - means for receiving the composite electromagnetic radiation beam, said means for receiving the composite electromagnetic radiation beam comprising: a first beam detection device (1) located in a first position and configured to generate a first composite beam electrical signal (D1) representing the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the first position; a second beam detection device (2) located in a second position different from the first position and configured to generate a second composite beam electrical signal (D2), the second composite beam electrical signal being representative of the electric field and / or magnetic field and / or the intensity of the electromagnetic radiation of the composite electromagnetic radiation beam in the second position; a first frequency discrimination device (8) configured to perform frequency discrimination of the first composite beam electrical signal (D1) to obtain a first main beam electrical signal (P1) and a first reference beam electrical signal (R1), the first main beam electrical signal representing the electric field, and / or magnetic field, and / or intensity attributable to the main beam in the first position, and the first reference beam electrical signal representing the electric field, and / or magnetic field, and / or intensity attributable to the reference beam in the first position; a second frequency discrimination device (9) configured to perform frequency discrimination of the second composite beam electrical signal to obtain a second main beam electrical signal (P2) and a second reference beam electrical signal (R2), wherein the second main beam electrical signal represents the electric field, and / or magnetic field, and / or intensity attributable to the main beam in the second position, and the second reference beam electrical signal represents the electric field, and / or magnetic field, and / or intensity attributable to the reference beam in the second position; - a phase determination device (20), said phase determination device being configured to: - determining the phase of the first main beam electrical signal (P1) and the phase of the second main beam electrical signal (P2); - determining the phase of the first reference beam electrical signal (R1) and the phase of the second reference beam electrical signal (R2); - determining a first phase difference value (ΔP) corresponding to the difference between the phase of the first main beam electrical signal (P1) and the phase of the second main beam electrical signal (P2); ab ), the first phase difference (ΔP ab ) depends on the values ​​taken by the first modulation function a(t) and the second modulation function b(t); - determining a second phase difference value (ΔR) corresponding to a difference between a phase of the first reference beam electrical signal (R1) and a phase of the second reference beam electrical signal (R2); - From the first phase difference value (ΔP ab ) divided by the first wave number k minus the second phase difference (ΔR) divided by the second wave number k' to obtain the difference (Q2 = ΔP ab / k–ΔR / k'), the difference (Q2=ΔP ab / k–ΔR / k') represents the combination of the values ​​taken by the first modulation function a(t) and the second modulation function b(t), independently of the positional inclination conditions between the first beam detector (1) and the second beam detector (2), and independently of the phase variation caused by the disturbances to which the transmitted composite electromagnetic radiation beam is subjected before reception; wherein the first wave number k is a wave number corresponding to the main beam, defined as k=2π / λ, λ is the wavelength of the main beam belonging to the first frequency band, and wherein the second wave number k' is a wave number corresponding to the reference beam, defined as k'=2π / λ', λ' is the wavelength of the reference beam belonging to the second frequency band; - processing means (15) configured to determine the difference (Q2 = ΔP ab / k−ΔR / k′) demultiplexes and demodulates information modulated on each of the first modulated beam (Fm1) and the at least one second modulated beam (Fm2).

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