METHOD AND DEVICE FOR BIDIRECTIONAL POWER SUPPLY AND COMMUNICATION ON AT LEAST ONE OPTICAL FIBER HAVING AT LEAST ONE WAVELENGTH

Abstract

The invention relates to a bidirectional power supply and communication device, comprising: - at least one optical fiber (2) between a master terminal (4) and at least one slave terminal (6); - the master terminal (4) comprising a light source (8) at at least one wavelength (λ), a photo-detector (10) and means (12) for directing a signal which comes from the slave terminal (6) via the optical fiber (2) to the photo-detector (10) and for directing a signal which comes from the light source (8) to the optical fiber (2); - the slave terminal (6) comprising at least one modulator (24) and a photovoltaic cell (20). Figure 2A

Description

Title of the invention: METHOD AND DEVICE FOR POWER SUPPLY AND COMMUNICATION-BIDIREC TIONAL ON AT LEAST ONE OPTICAL FIBER HAS AT LEAST ONE WAVELENGTH TECHNICAL FIELD AND PRIOR ART

[0001] The invention relates to the field of power transmission by fiber (Power Over Fiber (PoF) in English).

[0002] This technique uses fiber optic cables as the transfer medium for the laser power beam.

[0003] Considerably lighter than copper wires, PoF technology allows for remote sensors and actuators to be used without the traditional logistical and application challenges of wire weight and electrical wiring installation distance. It provides complete electrical isolation, has no emitted electrical noise (EMC) and therefore can last longer, go further and maneuver more.

[0004] More specifically, a high light intensity is emitted by a power laser and transmitted by an optical fiber, converted into electrical power by a photovoltaic power converter (PPC) at the other end of the fiber, at the node end of the chain.

[0005] Then, the electrical energy extracted from the PPC can drive sensors, processors and other electronic devices. Because fibers are used as power lines instead of electrical counterparts, the power delivery is inherently immune to surrounding electromagnetic fields, lightning and high voltages, and also avoids the bulky shielding of the power lines.

[0006] Currently, several fibers are needed: one fiber is dedicated to power and at least a second to communication.

[0007] We are particularly familiar with the article by J. Wang et al. entitled “Power-Over-Fiber Technique based Sensing System for Internet Of Things”, published in 2016 in the 15th International Conference on Optical Communications and Networks (ICOCN), 978-1-5090-3491-8 / 16.

[0008] In this document, the PoF system, illustrated in [Fig.l], consists of three parts:

[0009] - the base station 104, which includes a high power laser diode (HPLD) for the optical power supply, an optical receiving unit for receiving the optical data signal and a microprocessing unit for processing the detection data

[0010] - a remote unit 106, which comprises a photovoltaic power converter, a power management module, a microcontroller for processing the sensing data signal and a laser diode (LD) unit for transmitting the sensing data to the base station;

[0011] - the optical link, which comprises 2 fibers, a 102i multimode fiber with a diameter of core (105pm) for power transmission and another 1022 single-mode fiber (with a core diameter of 9 pm) for data transmission.

[0012] We seek to reduce the number of components used in such a system.

[0013] In particular, there is the problem of communicating bidirectionally with sensors and powering them, all with a single fiber using at least one wavelength, particularly in difficult environments.

[0014] Bidirectional optical communication with a remote terminal poses other problems when the latter operates in a harsh environment or with high environmental constraints such as for example at high temperatures (>200°C), or at low temperatures (<-40°C). In particular, this type of environment, and in particular high temperatures, does not tolerate the use of a laser-type light source on the side of the remote or slave terminal, because the performance of the latter depends greatly on its operating temperature.

[0015] Beyond the technological aspects, the various applications may also require significant constraints in terms of size, and / or weight, and / or flexibility, and / or ease of integration, and / or robustness and / or signal integrity for security reasons.

[0016] In particular, in order to increase the robustness of such a terminal to the surrounding conditions, it is appropriate to reduce the nomenclature constituting it, in particular the optical components requiring precise positioning and alignment (sensitivity to vibrations, accelerations) and / or containing specific surface treatments (delamination, pollution, oxidation, etc.).

[0017] Furthermore, in conventional architectures providing, in addition to communication, the optical fiber power supply of the remote terminal uses an additional optical fiber.

[0018] We therefore seek to reduce the complexity and nomenclature of such a system and to choose robust components, particularly under severe operating conditions (temperature, vibrations, acceleration, pressure, etc.) to ensure the reliability and robustness of such a communication and power supply solution. Statement of the invention

[0019] The invention aims to solve all or part of the problems set out above or in the remainder of the present application.

[0020] The invention firstly relates to a bidirectional power supply and communication device, comprising:

[0021] - at least one optical fiber, preferably a single optical fiber, between a first terminal, called master terminal and at least one second terminal, called slave terminal;

[0022] - the master terminal comprising a light source with at least a first wavelength (XJ, a photo-detector and means for directing a signal which comes from at least one slave terminal, via the optical fiber, towards the photo-detector and for directing a signal which comes from the light source towards the optical fiber;

[0023] - at least one, or each, slave terminal comprising at least one modulator and at least one less photo-detector and / or a photovoltaic cell to convert light signals into electrical signals for power and communication.

[0024] The or each slave terminal may further comprise an optical device making it possible to share the light between a photovoltaic cell and a photodetector.

[0025] Hereinafter, “the” slave terminal is also understood to also cover “at least one” slave terminal and / or the case of “each” slave terminal.

[0026] The modulator of the slave terminal makes it possible to reflect modulated light (which can therefore contain a message) towards the master terminal. The latter comprises, for example, a circulator making it possible to direct the light coming from the slave terminal towards a photo-detector.

[0027] The invention also relates to a method of power supply and bidirectional communication between a master terminal and at least one second terminal, for example implementing a device as described above and in the remainder of the present application.

[0028] A method according to the invention, or a method as defined above, may comprise the following steps:

[0029] - generating optical signals, including a power signal and one or more data signals, at at least a first wavelength in the master terminal and transmit them, by at least one optical fiber, for example by the single optical fiber, at least to the second terminal;

[0030] - the slave terminal receives the signals sent by the master terminal, even actually modulates them (in all or nothing or in analog), and returns all or part of a modulated signal or signals to the first terminal, via at least one optical fiber;

[0031] - the photo-detector of the master terminal receives the signals sent by the terminal slave via optical fiber.

[0032] The invention allows:

[0033] - not to use any light source in the slave terminal(s);

[0034] - to use, in certain embodiments, a single optical fiber;

[0035] - to optically power the slave terminal(s) from the light issued by the master terminal;

[0036] - a two-way communication (from the master terminal to the slave terminal and from the slave terminal to the master terminal) on the same optical fiber, possibly in “Full Duplex” (full duplex or simultaneous bidirectional) or in “half duplex” (alternate bidirectional);

[0037] - the exchange of digital and analog data;

[0038] - to operate in harsh environments (in particular, in temperature) due to the absence of fragile components, particularly light sources, in the second terminal.

[0039] The slave terminal can be connected to one or more sensors and / or actuator(s) to supply them with energy and to collect data from this / these sensor(s) and / or actuator(s) and send this data to another interface on the side of the first terminal, all through a single optical fiber.

[0040] The master terminal (for example a computer interface) can collect data from one or more sensors and / or actuators (second terminal) transmitted via the optical fiber.

[0041] In particular embodiments:

[0042] - the optical fiber can be a single-mode or multi-mode fiber.

[0043] - and / or:

[0044] - the master terminal is capable of transmitting, to the second terminal, a light signal continuous and a data signal, at the first wavelength (XI);

[0045] - the slave terminal is capable of transmitting a data signal to the master terminal, at the first wavelength (XI).

[0046] The light source can be monochromatic; this embodiment allows:

[0047] - to use a single wavelength for two-way communication, possibly in Full Duplex;

[0048] - an optical power supply of the slave terminal;

[0049] - an exchange of digital and / or analog data between the terminals.

[0050] Alternatively, the light source further emits at least a second (X2) wavelength, the master terminal further comprising a multiplexer for selecting said first wavelength (Xi) or said second (X2) wavelength.

[0051] This achievement allows:

[0052] - to use fewer components / complexity (simplifies demo electronics dulation which separates the data and power signals), particularly in energy efficiency mode;

[0053] - easier optical power supply;

[0054] - two-way communication, possibly in Full Duplex;

[0055] - a stable power supply of the second terminal.

[0056] In the latter case, the master terminal may comprise wavelength multiplexing means, a technique often called WDM (Wavelength Division Mul-tiplexing in English) which makes it possible to increase a high rate of digital and / or analog data on an optical fiber by circulating several signals of different wavelengths on a single optical fiber. The optical link then comprises a single fiber for the transport of energy and the transmission of data (with two different wavelengths Xi and X2) using wavelength division multiplexing (WDM).

[0057] In the latter case (polychromatic source), an operating mode, called energy efficiency, can be implemented:

[0058] - the master terminal being able to transmit, to the slave terminal:

[0059] *a continuous light signal (power), at the second wavelength (X2);

[0060] * a data signal, at the first wavelength (XI).

[0061] - the slave terminal being able to transmit to the master terminal, a signal of data, at the first wavelength (XI).

[0062] In other words, a wavelength is then dedicated to the transfer of power in order to supply the slave terminal with a stable power supply; this power does not vary or varies little and is supplied continuously.

[0063] Alternatively, another mode of operation, called high data rate, can be implemented:

[0064] - the master terminal being able to transmit, to the second terminal, a signal of continuous light (power) and a data signal, at the second wavelength (X2);

[0065] - the slave terminal being able to transmit to the master terminal, a signal of data, at the first wavelength (XI).

[0066] In other words, one wavelength is then dedicated to the communication data in one direction (from the slave terminal to the master terminal) and the second wavelength is dedicated to the power supply and to the data transmitted in the opposite direction (from the master terminal to the second terminal). In particular embodiments of a device or a method according to the invention:

[0067] - the slave terminal comprises at least one coupler / separator, the modulator and the photovoltaic cell being mounted in parallel;

[0068] - and / or the master terminal is capable of transmitting, to the second terminal, a signal offset, the slave terminal being able to transmit a data signal to the master terminal, by modulating the offset signal;

[0069] - and / or the device further comprises means for carrying out:

[0070] *a frequency modulation, at a first frequency (fpl), of the signals transmitted from the master terminal to the second terminal,

[0071] *-a frequency modulation, at a second frequency (fp2), of the signals transmitted from the slave terminal to the master terminal.

[0072] The modulator can be of the all-or-nothing type. For example, the modulator includes a switch or an optical switch which reflects the signal received from the master terminal (to possibly send it back to this same master terminal or which transmits it, for example to the photovoltaic cell.

[0073] The modulator may be of the analog type. For example, the slave terminal further comprises a mirror which reflects the entire signal modulated by the analog attenuator. In a particular embodiment, a device according to the invention comprises a plurality of slave terminals, coupling means between the optical fiber and said plurality of slave terminals.

[0074] In another particular embodiment, a device according to the invention comprises a plurality of slave terminals, and at least one optical fiber, for example a single optical fiber, between the master terminal and each of the slave terminals.

[0075] Alternatively, the modulator may be a spectral modulator. For example, it comprises a Bragg grating and / or a Fabry Pérot cavity associated with at least one mechanical stress generator and / or a heating and / or cooling element.

[0076] An example of a spectral modulator may include:

[0077] -a part of said optical fiber, which extends at least partly along an axis (XX') and comprising optical functionalization means, for example comprising a Bragg grating and / or a Fabry-Pérot cavity, having a reflection spectrum of a part of a light radiation circulating in the fiber; the optical functionalization means may have a reflection spectrum which totally or partially reflects the light in a spectral band between two wavelengths Xi and X2; and / or have a reflection spectrum which includes a front which varies with the wavelength;

[0078] - a deformable element, for example a piezoelectric type element, in a direction parallel to the same axis (XX') and having a length L; means for controlling this deformable element may also be provided; said optical fiber may be arranged outside the deformable element, or partly inside it;

[0079] -a first mechanical element and a second mechanical element fixed to the deformable element and capable of undergoing a relative deformation or a relative displacement (or a displacement of the first mechanical element relative to the second mechanical element) under the action of this deformable element, said optical fiber being fixed to the first mechanical element at a first fixing point and to the second mechanical element at a second fixing point, these two fixing points being arranged on either side of the optical functionalization means, the distance (d) between the first fixing point and the second fixing point preferably being less than the length (L) of the deformable element, the ratio L / d being for example at least equal to five.

[0080] In this example of a spectral modulator:

[0081] - if the fiber is arranged outside the deformable element, the first element mechanical element may comprise a first lateral surface and the second mechanical element may comprise a second lateral surface, aligned with each other and parallel to the direction of extension of the deformable element and the fiber, the first fixing point being located on the first lateral surface and the second fixing point being located on the second lateral surface, these two lateral surfaces being separated by a distance (D) less than the distance (d) which separates the fixing points;

[0082] - if the fiber is partly arranged inside the deformable element:

[0083] - the first mechanical element may comprise a semi-cylindrical core forming a first internal positioning surface of the optical fiber, the first fixing point being located on this first internal positioning surface;

[0084] - the second mechanical element may comprise an elongated part which penetrates the interior of the deformable element and which comprises an internal channel for receiving a first part of the optical fiber, this elongated part comprising a semi-cylindrical end part forming a second surface for positioning a second part of the fiber, the second fixing point being located on this second internal positioning surface, aligned with the first internal positioning surface, the two positioning surfaces being separated by a distance (D') less than the distance (d) which separates the fixing points.

[0085] The slave terminal of a device or method according to the invention may comprise several sensors connected to the slave terminal, which therefore communicate with the master terminal via a single optical fiber 2 with two wavelengths. In particular, the modulator may be one of those which have already been described above.

[0086] A device or method according to the invention may comprise several slave terminals, each comprising a sensor and a modulator; the master terminal and the second terminals therefore communicate using the optical fiber 2 with two wavelengths; each modulator may be one of those which have already been described above.

[0087] Each sensor is then associated with a modulator in a second terminal. The different second terminals are for example associated with a coupler / splitter arranged at the fiber output and upstream of each of the second terminals. BRIEF DESCRIPTION OF THE FIGURES

[0088] [Fig.l] represents an exemplary embodiment of a device according to the prior art;

[0089] [Fig.2A] represents a device according to an embodiment of the invention, implementing a power supply and bidirectional communication on a single fiber and capable of using a single wavelength;

[0090] Figures 2B-2D represent (Figures 2B and 2C) examples of signals transmitted between 2 terminals of a device according to an embodiment of the invention and ([Fig.2D]) modulation frequencies;

[0091] Figures 3A - 3B show an all-or-nothing modulator and examples of waveforms of the communication signals in full-duplex mode;

[0092] [Fig.4] represents an analog modulator, for communication in Full-duplex mode;

[0093] Figures 5A-5G show a mechanical modulator and examples of operating modes of such a modulator;

[0094] [Fig.6] represents a device according to an embodiment of the invention, implementing a power supply and bidirectional communication on a single fiber using two wavelengths (XI and X2);

[0095] [Fig.7] represents a device according to one embodiment of the invention, implementing bidirectional communication in energy-efficient power supply mode;

[0096] [Fig.8] represents a device according to an embodiment of the invention, implementing bidirectional communication in data mode on two wavelengths;

[0097] [Fig.9] represents a device according to an embodiment of the invention, implementing a modulator operating in all-or-nothing mode with communication in Full duplex mode;

[0098] [Fig. 10] represents a device according to an embodiment of the invention, implementing an analog modulator with communication in Full duplex mode;

[0099] [Fig. 11] represents a device according to one embodiment of the invention, implementing an optical spectrum modulator;

[0100] Figures 1 IA - 1 IB represent examples of operating modes of an optical spectrum modulator;

[0101] [Fig. 12] represents a device according to one embodiment of the invention, connected to a node of several sensors;

[0102] [Fig.l3A] represents a device according to one embodiment of the invention, connected to several sensor nodes.

[0103] [Fig.l3B] represents another device according to an embodiment of the invention, implementing multiple sensors.

[0104] [Fig.l4A] and [Fig.l4B] represent an example of a spectral modulator according to one embodiment;

[0105] Figures 15A and 15B show another example of a spectral modulator according to another embodiment;

[0106] [Fig.16A], [Fig.16B], [Fig.16C], [Fig.16D], [Fig.16E] and [Fig.16F] represent assembly steps of an example of a spectral modulator;

[0107] Figures 17A - 17B represent a reflection spectrum of a modulator, in two different states;

[0108] Figures 18A - 18B represent another reflection spectrum of a modulator, in 2 different states and with respect to two lines of two laser sources;

[0109] [Fig. 19] shows in an enlarged view means of functionalizing an optical fiber in the context of an embodiment.

[0110] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0111] [Fig.2A] represents a first example of embodiment of a device 1 according to the invention.

[0112] It comprises at least one optical fiber 2, for example a single optical fiber, capable of transmitting at least one wavelength X. This fiber, like all the fibers in the remainder of this application, has an input 2e and an output 2S; it is arranged between:

[0113] - a first terminal, or master terminal 4, also called an interrogator terminal;

[0114] - a second terminal, or slave terminal 6 (sensor node), which may be located in a harsh environment; this terminal is also called a remote terminal; this slave terminal 6 makes it possible both to supply one or more sensors and / or actuators (with energy) but also to ensure the collection of data from this / these sensor(s) / actuator(s) and to send them to the master terminal 4 through the single optical fiber 2; the sensors and / or actuators can communicate with the slave terminal 6 via a wired connection, for example by implementing a known communication protocol of the SPI or I2C type.

[0115] The optical link comprises the single fiber 2 for the transport of energy and the transmission of data at wavelength X. Its input 2e is arranged on the side of the master terminal, which is therefore located downstream of this input, and its output 2S on the side of the slave terminal, which is therefore located downstream of this output. The same applies to the various fibers 2, 2; presented in this description.

[0116] According to one embodiment, the interrogator terminal 4 comprises:

[0117] - a light source 8, which can be monochromatic (at wavelength X), adapted to emit light which can be detected by the detector 10 of terminal 4, and by the PV cell 20 of terminal 6;

[0118] - a photo-detector 10, which makes it possible to convert light into electric current;

[0119] - means, for example a circulator 12, which make it possible to direct the light from the source 8 to the remote terminal 6 and the light coming from the latter, re-emitted by the modulator, to the photo-detector 10.

[0120] The remote terminal 6 comprises:

[0121] - a photovoltaic cell 20 for converting light into current electrical; electronic demodulation means make it possible to separate data signals from power signals (the latter being intended for power supply);

[0122] - a modulator 24 allowing on the one hand to modulate the light emitted by the source 8 of the interrogator terminal 4 and on the other hand to return light to the photodetector 10 via the optical fiber 2 and the circulator 12. This modulator 24 is controlled by means or control electronics 25 (these means can be implemented in most of the embodiments described in this application).

[0123] [Fig.2B] represents an example of signal Ts transmitted from master terminal 4 to slave terminal 6:

[0124] - initially, a continuous signal (S'power), constant and non-zero is transmitted to the slave terminal 6, with data to be communicated to it; the data are superimposed on S'power (S'power + data);

[0125] - in a second step, only the continuous signal S'power, constant and non-zero, continues to be transmitted to the slave terminal 6.

[0126] [Fig.2C] represents an example of a reflected RM signal transmitted from the slave terminal 6 to the master terminal 4:

[0127] - firstly, a data signal is transmitted to the master terminal 4, this signal being obtained using a S”POwer part of the power signal which provides a reference signal for data communication from the slave terminal 6 to the master terminal 4;

[0128] - in a second step, only the reference S”POwer signal, constant and non-zero, continues to be transmitted to the master terminal 4.

[0129] As can be understood from these figures 2B and 2C, to supply power to the slave terminal 6, the master terminal 4 continuously sends a continuous signal SPOWer which is shared between S'power (which serves as power supply) and S”POwer (which serves as a reference signal for communication between the 2 terminals).

[0130] The transfer of signals / data in “Full-duplex” mode, i.e. the case where the two terminals can communicate simultaneously, is possible thanks to a frequency modulation, for example as illustrated in [Fig.2D], where the signals between the two terminals are carried by two distinct frequencies fpl and fp2 which are preferably sufficiently far apart to take into account the bandwidths BPI and BP2 of the signals / data involved.

[0131] Generally speaking, for the different embodiments presented in the present application:

[0132] a) - the modulator 24 operates on the basis of the Transmission (T) and the Reflection (R) of the light;

[0133] b) - when the master terminal 4 sends data or a light signal comprising the power signal SPOwer and the data D0Ut to be communicated to the slave terminal 6, the modulator 24 transmits these signals in full to the photovoltaic cell 20;

[0134] c) - when the slave terminal 6 sends a signal to the master terminal 4, the latter continues to transmit at least the SPOwer signal to the slave terminal 6;

[0135] d) - the modulator makes it possible to modulate the reflection, that is to say, the light returned to the master terminal 4 with a rate ranging from 0% to 100%.

[0136] The embodiments described in connection with figures 2A-2D and 3A-5G make it possible to implement 2 modulator architectures of the slave terminal 6:

[0137] - all or nothing, with total transmission or total reflection;

[0138] - analog, with partial transmissions and reflections.

[0139] The architecture of the all-or-nothing modulator of the slave terminal 6 will be explained in connection with Figures 3A-3B.

[0140] In the slave terminal 6, a device providing the coupler and splitter functions 26 (also called an optical divider or beam distributor) makes it possible to mount the photovoltaic cell 20 and the modulator 24 in parallel, and to share the power of the signal coming from the master terminal 4 between the modulator 24 and the photovoltaic cell 20, the energy distribution between these 2 elements depending on the needs.

[0141] The modulator 24 comprises a “switch” 23 (or optical switch), arranged downstream of the distributor 26 and allowing either the transmission of all the light or its total reflection (all or nothing). It is controlled by control electronics 25 to switch between the two states: transmission (T), reflection (R).

[0142] When the switch 23 is in the “Transmission” state, it routes the light either to an absorber 241 or, for example, to the photovoltaic cell 20 for greater energy efficiency. When the switch 23 is in the “reflection” state, it routes the light to a mirror 242 whose role is to reflect the light, which is then returned to the master terminal 4.

[0143] Figures 2B - 2C show examples of signals transmitted and reflected between terminals 4 and 6, see the comments above in connection with these figures.

[0144] The master terminal 4 continuously sends a non-zero offset signal S”POWer, partly routed to the modulator. This continuous offset allows the slave terminal 6 to send data to the master terminal 4 at any time by modulating it (state high, low state) by switch 23. The latter can switch between two states according to two possible configurations:

[0145] (i) Reflection towards the master terminal 4 or absorption: the offset is either reflected to return a state X (X = low, respectively high) to the master terminal 4, or absorbed to return a state Y (Y = high, respectively low) to the master terminal 4;

[0146] (ii) Reflection towards the master terminal 4 or transmission towards the photovoltaic cell 20: the offset is either reflected to return a state X (X = low, respectively high) towards the master terminal 4 or transmitted to the photovoltaic cell 20 to return a state Y (Y = high, respectively low) towards the master terminal 4; in this case, not only is the energy efficiency better, but the slave terminal 6 is capable of verifying the integrity of the returned data (Data) which are exactly inverse (logically complementary) (Dàta) of the data detected by the photovoltaic cell 20 (see [Fig.3B]).

[0147] The transfer of signals / data in Full-duplex mode, that is to say, the case where the two terminals can communicate simultaneously, is also possible thanks to a frequency modulation where the signals from the slave terminal 6 to the master terminal 4, and vice versa, are carried by two distinct frequencies fp 1 and fp2 ([Fig.2D]) which are preferably sufficiently far apart to take into account the bandwidths BPI and BP2 of the signals / data involved.

[0148] This solution allows:

[0149] - to supply power to the slave terminal 6;

[0150] - for both terminals to communicate in full-duplex;

[0151] - to transmit digital or analog signals from the master terminal 4 to the slave terminal 6;

[0152] - to transmit digital data from the slave terminal 6 to the terminal master 4;

[0153] - to facilitate the verification of the integrity of the signals transmitted from the slave terminal 6 to master terminal 4.

[0154] An architecture with analog modulator of the slave terminal 6 and communication in Full duplex mode will be explained in connection with [Fig.4].

[0155] The modulator 34 comprises an analog attenuator 33 for modulating the transmission / reflection in an analog manner. This attenuator is controlled by control electronics 25 to control its transmission. In series with this attenuator is mounted a mirror 36 to reflect the light towards the master terminal 4. The modulator 34 and the photovoltaic cell 20 are mounted in parallel via the coupler 26 for sharing the power of the signal coming from the master terminal 4 between the modulator 34 and the photovoltaic cell 20.

[0156] To supply power to the slave terminal 6, the master terminal 4 continuously sends a continuous signal SPOwer which is then shared by the coupler 26 into S' power (which serves as a power supply via the photovoltaic cell 20) and S”POwer (which serves as a reference signal for communication between the 2 terminals).

[0157] When the master terminal 4 sends data (analog and / or digital, of lower power than SPOWer), these are superimposed on SPOwer- The electronics associated with the photovoltaic cell 20 decouple the power part (S'POWer from S power) from the part relating to the data.

[0158] When the slave terminal 6 communicates with the master terminal 4, the attenuator 34 coupled to its mirror 36, modulates the S”POWer signal in amplitude to generate the data (analog or digital) reflected towards the master terminal 4.

[0159] Figures 2B - 2C show examples of signals transmitted between terminals 4 and 6, see the comments above in connection with these figures.

[0160] For a “Full-duplex” communication to take place, the waveforms (signals / data) sent by the master terminal 4 are carried by two frequencies fpl and fp2 ([Fig.2D]), which are preferably sufficiently far from each other taking into account the bandwidths (BPI and BP2) of the signals involved. Under these conditions, the two terminals can communicate simultaneously and at any time.

[0161] This solution allows:

[0162] - transmit digital and / or analog signals from the master terminal 4 to the slave terminal 6 and vice versa;

[0163] - to establish bidirectional communication in full duplex or half-duplex;

[0164] - to supply power to the slave terminal 6.

[0165] Another architecture with analog modulator and communication in Full duplex mode will be explained in connection with Figures 5A-5G.

[0166] The modulator 44 ([Fig.5A]) here comprises means 43, for example a Bragg grating and / or a Fabry Pérot cavity; associated with means 46 forming a mechanical stress generator.

[0167] This type of modulator can be integrated into the optical fiber 2 which also serves as a communication channel or can be independent of it. It is controlled by means or control electronics 25.

[0168] This type of modulator makes it possible to produce a spectral modulator, which makes it possible to transmit / reflect partially or completely the light emitted by the master terminal 4 for a well-defined range of wavelengths.

[0169] When actuated, the mechanical stress generator 46 modifies the physical properties of the means 43, which generates modifications of the spectral properties in transmission / reflection of the modulator, as explained further in the link with figures 5B-5G, 11A-11B and 17A-18B. In these figures, the wavelength is on the abscissa and the intensity Ispectrum of the spectrum(s) concerned on the ordinate.

[0170] A more particular example of an embodiment of a generator 46 of mechanical constraints and of a modulator 44 is given further on in connection with figures 14A-16F and 19.

[0171] When the master terminal 4 sends a signal to the slave terminal 6 in the form of light, the wavelength(s) of the latter is (are) fully or partially transmitted by the spectral modulator 44 to the photovoltaic cell 20.

[0172] When the slave terminal 6 sends a signal to the master terminal 4, the modulator 44 transmits or reflects this signal according to the following cases:

[0173] * if there is total transmission and reflection (case of figures 5B and 5C): the data and the SPOwer power are either fully transmitted or fully reflected. When the master terminal 4 communicates with the slave terminal 6, the modulator 44 transmits the signals in full. In the case of reverse communication, the modulator switches between full transmission and full reflection to represent the digital data. During the communication phases, the slave terminal 6 receives a SPOwer signal (power) attenuated to an average value (the modulator reflects or transmits the entire signal, the latter is not modulated); under these conditions, the communication is in half duplex;

[0174] * if there is total transmission and partial reflection (case of figures 5D and 5E): the Slave terminal 6 continuously and uninterruptedly receives a SPOWer signal for its power supply with a level that can fluctuate slightly during communication phases. When the master terminal 4 sends data to the slave terminal 6, the modulator transmits all of the signals. In the opposite case (slave terminal 6 to the master terminal 4), the modulator can switch between the two states: partial reflection (with a rate X <100%) and total transmission to represent digital data. Under these conditions, full-duplex communication is possible using frequency modulations.

[0175] * if there is linear modulation in transmission / reflection (case of figures 5F and 5G): the modulator 44 has a linear characteristic on its reflection slope. This offers the possibility of performing analog amplitude modulations and therefore of exchanging analog signals in both directions of communication, which is not possible in the two previous cases. In one use case, A is defined as the maximum reflection rate (%) of the modulator 44 to guarantee a SPOWer power level sufficient to supply the slave terminal 6 (SPOWer- A x SPOwer)-In this case, the modulator is adjusted so that the wavelength of the source coincides with a reflection rate of A. Under these conditions, when the master terminal 4 communicates with the slave terminal 6, the modulator transmits inte generally digital and / or analog signals as well as SPOWer- When the slave terminal 6 sends data, the modulator linearly reflects a portion of the signals passing through it ranging from 0% to A%. When the master terminal 4 communicates with the slave terminal 6, the modulator transmits the entire signal power. In this case, full-duplex communication is possible using frequency modulations.

[0176] When full-duplex communication is possible, the bandwidths of the signals involved in both directions (BPi and BP2, see [Fig.2D]) are preferably taken into account in the choice of carrier frequencies^ / andfp2.

[0177] This optical spectrum modulator solution offers all the advantages of the modulator architectures presented above; in addition, it offers:

[0178] - the possibility of full-duplex communication without additional optical components tional (e.g. coupler / splitter, and / or mirror);

[0179] - reduced bulk and nomenclature because this spectral modulator can be directly integrated into the optical fiber serving as a communication channel, thus contributing to improving the reliability and robustness of the invention;

[0180] - simpler verification of the integrity of data sent by the terminal slave 6 to master terminal 4.

[0181] The other embodiments, described in particular in connection with figures 6-13B, make it possible to implement four architectures of the modulator: all or nothing; analog; Half duplex; or Full duplex. The principles a) - d) already set out above concerning the modulator also apply to these other embodiments.

[0182] [Fig.6] represents another example of embodiment of a device 1' according to the invention.

[0183] The differences from the diagram in [Fig.2A] are as follows:

[0184] - the optical fiber 2 is capable of transmitting two wavelengths Xi and X2;

[0185] This optical link ensures the transport of energy and the transmission of data (with two different wavelengths Xi and X2);

[0186] - the light source 8 is adapted to emit light, with two lengths of different waves Xi and X2, which can be detected by the detector 10 of the terminal 4, and the photovoltaic cell 20 of the terminal 6; a laser source with two different wavelengths Xi and / .2pcut suitable using wavelength multiplexing means 14 (WDM, DWMD or AWG ("Array Waveguide Grating") for a wide spectrum source);

[0187] - in the master terminal 4, the detector 10 is sensitive to at least the wavelength Xi; furthermore, it implements 14 wavelength division multiplexing (WDM) means; wavelength division multiplexing, often called "WDM" (Wavelength Division Multiplexing in English), is a technique used in communication optics that allows the flow rate on an optical fiber to be increased by circulating several signals of different wavelengths on a single fiber.

[0188] The advantages of this technique are as follows:

[0189] * Full utilization of the low loss band of optical fiber to increase its transmission capacity of it and double its physical limit of information transmission; currently, a very small part of the optical loss spectrum (1310nm-1550nm) is used, wavelength division multiplexing (WDM) can take full advantage of the huge bandwidth of an optical fiber (multimode or single-mode) and sufficient transmission bandwidth;

[0190] * the possibility of transmitting two or more unsynchronized signals in the same optical fiber facilitates compatibility between digital signals and analog signals,

[0191] - the slave terminal 6 comprises:

[0192] * an assembly comprising a photovoltaic cell 20 making it possible to convert the light into electric current;

[0193] - a modulator 24 for modulating the light emitted by the source 8 of the master terminal 4 and send it back to the photo-detector 10 via the optical fiber 2 and the circulator 12.

[0194] An architecture such as that of [Fig.6] makes it possible to supply power to a remote terminal 6 and to establish bidirectional communication between the interrogator terminal 4 and the remote terminal 6 using a single optical fiber with two wavelengths.

[0195] This embodiment of the invention here proposes an optical solution for bidirectional communication and power supply based on a single optical fiber, capable of operating at two wavelengths using the wavelength division multiplexing (WDM) technique.

[0196] Two modes of two-way communication, which will be explained below, can be implemented within the framework of this embodiment:

[0197] - An energy efficiency mode;

[0198] - a high data rate mode.

[0199] In energy efficiency mode ([Fig.7]):

[0200] - a wavelength X2 is dedicated to the power transfer in order to supply the slave terminal 6 with a stable power supply over time;

[0201] - the other wavelength (Xi) is dedicated to data transfer between the terminal master 4 and slave terminal 6.

[0202] The master terminal 4 sends a signal comprising:

[0203] - a power part on the wavelength X2;

[0204] - a data signal on wavelength Xb

[0205] More precisely he sends:

[0206] - a SPOWER power part (wavelength X2), comprising a light signal which represents a constant, non-zero continuous signal, serving as an energy level to be supplied to the slave terminal 6

[0207] - a part, at wavelength Xb containing the data D0Ut to be communicated to the slave terminal 6 and a non-zero continuous signal (OFFSET).

[0208] The slave terminal 6 sends to the master terminal 4 a signal composed of data (D1N), on the wavelength Xb. In this case, the master terminal 4 sends beforehand, on the same wavelength, a non-zero continuous signal serving as a signal to be modulated by the modulator 24 to generate the data to be transmitted (D1N) to the master terminal 4.

[0209] In this mode, the bidirectional communication can be in “full duplex” (the two terminals can communicate simultaneously) using two different carrier frequencies, as explained above in connection with [Fig.2D]: thanks to an amplitude modulation for example (or frequency, or phase), the signals from the slave terminal 6 to the master terminal 4, and vice versa, are carried for example by two distinct frequencies fp 1 and fp2 which are sufficiently far apart to take into account the bandwidths BPI and BP2 of the signals / data involved.

[0210] This mode is more interesting, with better energy efficiency and a very stable power supply, because a wavelength is dedicated to the light signal which represents a constant and non-zero continuous signal serving as an energy level to be brought from the master terminal 4 to the slave terminal 6.

[0211] In high data rate mode ([Fig.8]):

[0212] - there is sharing of the power transfer and the transmitted data, from the terminal master 4 to slave terminal 6, on the same wavelength (X2);

[0213] - the other wavelength (Xi) is dedicated to the communication data in the other way, from slave terminal 6 to master terminal 4.

[0214] The master terminal 4 sends a signal composed of a power part SPOwer (on the wavelength X2) as well as a data signal DOuT (also on the wavelength X2). More precisely, it sends, on the same wavelength (X2):

[0215] - a SPOWer power part, comprising a light signal which represents a signal constant and non-zero continuous, serving as energy level to be supplied to the slave terminal 6;

[0216] - a part containing the DOut data to be communicated to the slave terminal 6.

[0217] Subsequently, it is explained that the modulator 24 transmits this signal (DOut + SPOWer) in integrally to the photovoltaic cell 20.

[0218] The slave terminal 6 sends to the master terminal 4 a signal composed of data, on the wavelength Xb In this case, the master terminal 4 sends beforehand, on the same wavelength, a non-zero continuous signal serving as a signal to be modulated by the modulator 24 to generate the data to be transmitted (D1N) to the master terminal 4.

[0219] In this mode, communication can be in “full duplex”, without the need for carrier frequencies. This mode is more interesting when there are no energy constraints. This mode makes it possible to increase the bandwidth of the optical fiber 2 and to increase the transmission bandwidth of the data from the sensor(s) (therefore increasing the data rate).

[0220] The architecture of the on-off modulator with full duplex communication will be explained in connection with [Fig.9]. The modulator itself is identical or similar to that of [Fig.3A].

[0221] This architecture makes it possible to integrate a coupler / splitter 26 into the slave terminal 6 in order to allow bidirectional signal / data transfer.

[0222] To this end, the photovoltaic cell 20 and the modulator 24 (which comprises a “switch” or optical switch 23, as in [Fig.3A]) are connected in parallel via the coupler 26. The latter therefore makes it possible to share the power of the signal coming from the master terminal 4 between the modulator 24 and the photovoltaic cell 20. In this case, only the signal carried by the wavelength Xi is fully directed by the coupler 26 towards the optical switch 25, while the signal X2 is fully transmitted towards the photovoltaic cell 20.

[0223] The master terminal 4 continuously sends a non-zero signal (offset) carried by Xi and routed entirely to the modulator 24. This continuous offset allows the slave terminal 6 to send data at any time to the master terminal 4 by modulating it (high state, low state) by the switch 23. The latter can switch between two states according to two possible configurations:

[0224] (i) Reflection towards the master terminal 4 and absorption: the offset is either reflected to return an X state (X = low or high) to the master terminal 4, or absorbed to return a Y state (Y = high or low) to the master terminal 4;

[0225] (ii) Reflection towards the master terminal 4 and transmission towards the slave terminal 6: the offset is either reflected to return a state X towards the Master or transmitted to the photovoltaic cell 20 to return a state Y towards the master terminal 4; in this case, the slave terminal 6 is capable of verifying the integrity of the returned data (Data} which are exactly the inverse (logical complement) (Data') of the data transmitted towards the photovoltaic cell 20.

[0226] The transfer of signals / data in Full-duplex mode, i.e., the case where the two terminals can communicate simultaneously, is also possible as already explained above, thanks to a modulation where, for example, the signals from the slave terminal 6 to the master terminal 4, and vice versa, are carried by two distinct frequencies fpl and fp2 which are sufficiently far apart to take into account takes into account the BPI and BP2 bandwidths of the signals / data involved.

[0227] An architecture with analog modulator and full duplex communication will be explained in connection with [Fig. 10]. The modulator itself is identical or similar to that of [Fig.4].

[0228] The modulator 34 here comprises an analog attenuator 33 making it possible to modulate the transmission / reflection in an analog manner. This attenuator is controlled by control electronics 25 to control its transmission. In series with this attenuator is mounted a mirror 36 to reflect the light towards the master terminal 4. The modulator 34 and the photo-detector 20 are mounted in parallel via a coupler / splitter 26 making it possible to share the power of the signal coming from the master terminal 4 between the modulator 34 and the photo-detector 20.

[0229] The master terminal 4 can send signals in analog or digital form, the waveforms of which are then extracted using the photo-detector 20 and its associated electronics. On the other hand, so that the slave terminal 6 can communicate with the master terminal 4, the latter sends a non-zero continuous signal (example “offset”) which is then modulated by the analog attenuator 34 and reflected by the mirror 36 downstream to be sent back to the master terminal 4.

[0230] For “Full-duplex” communication, the waveforms (signals / data) sent by the master terminal 4 can be superimposed on a non-zero continuous signal (for example an “offset”) and carried by a frequency fpl. Under these conditions, the slave terminal 6 can communicate at any time by modulating the offset coming from the master terminal 4, thanks to the modulator 34, at a frequency fp2, preferably sufficiently far from fpl, for example by taking into account the bandwidths (BPI and BP2) of the signals involved.

[0231] This solution allows:

[0232] - transmit digital and / or analog signals from the master terminal 4 to the slave terminal 6 and vice versa;

[0233] - to establish two-way communication in full duplex and half duplex.

[0234] Another architecture with analog modulator and full duplex communication will be explained in connection with [Fig. 11]. The modulator itself is identical or similar to that of [Fig.5A].

[0235] The modulator 44 comprises means 43, for example a Bragg grating (FBG) and / or a Fabry Pérot cavity (CFP), coupled to a generator 46 of mechanical constraints (for example as described in connection with FIGS. 14A-15F) or a heating / cooling element.

[0236] The Bragg grating and / or the Fabry Pérot cavity can be integrated into the same optical fiber 2 serving as a communication channel or they can be independent of it (as in [Fig. 11]).

[0237] The mechanical stress generator 46 and / or a heating / cooling element can be controlled by control electronics 25. When it / they are actuated, the variations in stress and / or length of the generator 46 are transmitted to the means 43 (Bragg grating and / or Fabry Pérot cavity), the physical properties of which are modified, in particular their spectral properties in transmission / reflection.

[0238] The system can thus perform spectral modulation: the modulator is capable of transmitting / reflecting partially or completely the light emitted by the master terminal 4 for a well-defined range of wavelengths.

[0239] As explained above in connection with Figures 5B-5G, the architecture of [Fig.l 1] can operate in all or nothing mode with communication in Full duplex mode.

[0240] The optical spectrum modulator 44 makes it possible to do all or nothing on the signals emitted by the master terminal 4.

[0241] The optical spectrum modulator 44 is configured so as to be able to be in one of the following two modes:

[0242] Mode 1: modulator 44 is passable for both wavelengths Xi and X2:

[0243] In this mode, the two wavelengths emitted by the master terminal 4 arrive at the detector of the slave terminal 6. X2 can be a continuous and non-zero signal for the supply of the slave terminal 6. The spectral modulator has the transmission curve of [Fig.l 1 A] (passing for the 2 wavelengths).

[0244] Mode 2: modulator 44 is blocked for wavelength Xi and is passing for wavelength X2:

[0245] This mode allows X2 to pass in order to supply the slave terminal 6 with power and to reflect Xb. The spectral modulator has the transmission curve of [Fig.1 IB] (blocked for one wavelength, passing for another wavelength).

[0246] Thus:

[0247] - when communication is carried out from the master terminal 4 to the slave terminal 6, modulator 44 is in mode 1 (Xi carries data and an offset signal and X 2 is continuous; optical spectrum modulator 44 passes both wavelengths). The detector of master terminal 4 separates the data from the continuous signal;

[0248] - when communication is made from the slave terminal 6 to the master terminal 4, the Master terminal 4 outputs both signals Xi (data and an offset signal) and X2 (non-zero offset signal). And the spectral modulator can switch between mode 1 and mode 2 (mode 1: data output from slave terminal 6 to master terminal 4 = 0; mode 2: data output from slave terminal 6 to master terminal 4 = 1).

[0249] Thus, it is possible to set up full duplex communication while powering the slave terminal 6.

[0250] The embodiments explained above in connection with [Fig. 11] offer more advantages than the two architectures described in connection with figures 9 and 10. In particular, these embodiments allow:

[0251] - full-duplex communication without additional optical components (eg. coupler, mirror);

[0252] - reduced bulk and nomenclature because this spectral modulator can be directly integrated into the optical fiber 2 serving as a communication channel, thus contributing to improving the reliability and robustness of the invention.

[0253] An alternative embodiment is shown in [Fig. 12]: it is a device comprising several sensors 71-74 which communicate using a single optical fiber 2 with two wavelengths; the other elements of this alternative may be those described above in connection with Figures 6-11. In particular, the modulator may be one of those which have already been described above. One or more of the sensors 71 - 74 may be connected to one of the structures described in Figures 2, 3A, 4, 5A, 6-9.

[0254] Another embodiment is presented in [Fig.l3A]: it is a device comprising several slave terminals 6i, (i = 1, ..., N) each comprising a photovoltaic power converter 20i (photovoltaic cell) and a modulator 24i. The master terminal 4 and the slave terminals 6i communicate using a single optical fiber 2 with two wavelengths; the other elements of this variant may be those described above in connection with figures 6-11. In particular, each modulator 24i may be one of those which have already been described above. Each modulator 24i is controlled by means or control electronics 25i (i = 1, ..., N) in the time frame of the transmitted signals, a specific time interval may be dedicated to each of the terminals 6i.

[0255] The different slave terminals 6; are associated with a coupler / splitter 27 (sensor node) arranged at the output 2S of the fiber 2, or downstream of this output, and upstream of each of the slave terminals 6;.

[0256] Similarly, in the cases set out above in connection with Figures 2A-5G, we can have:

[0257] - the master terminal 4 connected to the terminals 6; with a single optical fiber 2. One terminals 6; uses an optical multiplexer (coupler) to address the other terminals 6;. This configuration is similar to that of [Fig. 13A], but without the means 14, since a single wavelength is sufficient;

[0258] - or the master terminal 4 connected to the terminals 6; with a single optical fiber 2 and several wavelengths Xi5 each wavelength Xi being associated with one and only one slave terminal 6; (as illustrated in [Fig.l3B]); an optical coupler or optical switch is used to address each of the terminals 6i. This element (coupler or optical switch) is arranged to output it from the 2i fibers, on the side of the master terminal 4. The frame of the transmitted data can include a time interval dedicated to each 6i terminal.

[0259] The invention allows a reduction in the wiring between the interrogator (or master) terminal 4 and the sensor node(s) and / or actuator(s), located on the side of the remote (or slave) terminal(s) 6, which may be in harsh environments (high temperature), by transferring the power and data from the sensors through bidirectional communication on a single optical fiber (with two wavelengths and a modulator on the slave side).

[0260] The invention also offers numerous advantages:

[0261] - the “slave” node, or remote terminal 6, does not contain a light source, for example a laser;

[0262] - communication is bidirectional, in half duplex or in full duplex;

[0263] - a single optical fiber is sufficient;

[0264] - two wavelengths can be used on the same fiber;

[0265] - the power supply is carried out through the optical fiber;

[0266] - a reduction in bulk and nomenclature is obtained.

[0267] Figures 14A and 14B represent a particular example of an embodiment of a mo controller that can be implemented within the framework of the present invention.

[0268] This modulator comprises at least one fiber 2 extending at least partly along an axis XX', this fiber 2 being fixed to the outside of an element 46 deformable or mobile along a direction parallel to the same axis XX'.

[0269] The fiber 2 is functionalized by means 44, for example a Bragg grating or a Fabry-Pérot cavity, each having light reflection properties as a function of the wavelength, properties which will evolve as a function of the deformation of the element 46.

[0270] The device further comprises a first support or mechanical element 8 and a second support or mechanical element 14. In this example, the first support or mechanical element 80 is fixed and the second support or mechanical element 14 is movable, but two supports or mechanical elements movable relative to each other are also usable. Each of these two supports or mechanical elements is connected on the one hand to the deformable or movable element 46 and on the other hand to a part of the optical fiber 2, so that the means 44 are arranged between a first point 16 for fixing or anchoring the fiber to the support 80 and a second point 18 for fixing or anchoring the fiber to the support 14.

[0271] The deformable or mobile element 46 is preferably of the piezoelectric type; as a variant, it may be a MEMS, or a motor, or a translation element (for example a plate), or a worm screw, or a spring, which makes it possible to modulate the spectrum at high rates: up to several hundred kHz or even more (for example at frequencies less than or equal to 500 kHz or 1 MHz, or even > 1 MHz). For example, this piezoelectric element deforms longitudinally, along the axis XX', parallel to the optical fiber 2. An example of such a piezoelectric element 46 is illustrated in [Fig.l5B]. It can be controlled or commanded by means (or an electrical circuit) 55, which will make it possible to control the voltage and its frequency applied to the terminals of the piezoelectric element.

[0272] The fixed mechanical support 80 preferably has a parallelepiped shape, with:

[0273] - a flat lateral face 80b parallel to the direction XX' of extension of at least one part of fiber 2 and against which the latter can be fixed;

[0274] - a main face 80a, facing the piezoelectric element 46, which can have in its middle a hollow 80c forming a reception volume into which one end of this element 46 can penetrate in order to ensure solid fixing of the latter with the support 80.

[0275] The mobile mechanical support 14 preferably has an overall “U” shape, the lateral branches 14bi, 14b2 of the “U” being parallel to each other and to the direction XX' of extension of at least a part of the fiber 2 and of movement of the element 46. As a variant (not shown in the figures), the mobile mechanical support 14 has a single lateral branch 14bl (therefore no branch 14b2). But the presence of a 360° elbow 14b2 makes it possible to position several optical fibers and to parallelize the phenomena.

[0276] Thus, the distance D between the movable mechanical support 14 and the fixed mechanical support 8 is less than the distance d which separates the fixing points 16, 18 of the optical fiber against the surfaces 80b and 14b. The fiber is fixed against the outer wall 14b of the branch 14bi, located on the same side, relative to the deformable element 46, as the surface 80b against which the fiber is fixed. This movable mechanical support 14 may have in its middle a stud 14a which penetrates into the piezoelectric element 46 in order to ensure a solid fixing of the latter with the support 14.

[0277] The outer surface 14b of the mechanical support 14 and the surface 80b of the fixed mechanical support 80 against which the fiber 2 is fixed are flat and aligned in the same plane.

[0278] Fiber 2 is made integral:

[0279] - on the one hand of the fixed mechanical support 80 by means of a first means of fixing or anchoring at the first point 16;

[0280] - on the other hand of the mobile mechanical support 14 by means of a second means of fixing or anchoring at the second point 18.

[0281] Each anchoring means is for example a glue, or a cement, or an adhesive tape, or thermal projections, or any means allowing the fiber to be fixed.

[0282] Steps for assembling such a device may be as follows:

[0283] - first, one end of the piezoelectric element 460 is positioned in the reception volume 80c, if present; this end can be glued into the fixed mechanical support 80;

[0284] - the mobile mechanical support 14, comprising its lateral branches 14bb 14b2 and its central stud 14a is then fixed to the other end of the piezoelectric element; more precisely, the central stud 14a, if present, can be inserted into a hollow made in this other end, and can be fixed there by gluing, so that the surfaces 14b and 80b are aligned;

[0285] - finally, the functionalized fiber 2 (therefore comprising a Bragg grating or a cavity Fabry Perrot 4) is positioned against the lateral surfaces 80b and 14b on which it is fixed as explained above, the means 4 being arranged between the 2 fixing or anchoring points 16, 18.

[0286] Figures 15A and 15B represent another example of embodiment of a modulator 1' that can be implemented within the framework of the present invention. In this variant, the fiber 2, which extends at least partly along an axis XX', passes inside the deformable or mobile element 46 along the same axis XX'.

[0287] As previously, the fiber 2 is functionalized by means 44, for example a Bragg grating or a Fabry-Pérot cavity.

[0288] The device further comprises a fixed support or mechanical element 38 and a mobile support or mechanical element 34, in the shape of a “T”, comprising a head 34 and an elongated body 34a; here again, it is possible to have two mobile supports or mechanical elements.

[0289] Each of these two supports or mechanical elements is linked on the one hand to the deformable or mobile element 46 and on the other hand to a part of the optical fiber 2, so that the means 44 are arranged between a first point 260 for fixing or anchoring the fiber to the support 38 and a second point 280 for fixing or anchoring the fiber to the support 34.

[0290] For the reasons already explained above, the deformable or mobile element 46 is preferably of the piezoelectric type; alternatively, it may be a MEMS, or a motor, or a translation element (for example a plate), or a worm screw, or a spring. It deforms longitudinally, along the axis XX'. An example of such a piezoelectric element has already been given above in [Fig.l4B]; it is also shown in [Fig.l6D].

[0291] The fiber 2 is positioned in an inner channel 34c of the movable mechanical support and in an inner channel 38c (see Figures 16E and 16F) of the fixed mechanical support. The end 34d of the elongated body 34a is not solid and comprises a solid half-cylinder and a hollow half-cylinder, as illustrated in Figures 16B and 16C, so that a flat surface 34e, in the conduit extension 34c into which the fiber is introduced, forms a receiving surface for the latter, on which it can be fixed.

[0292] Thus, the distance D' between the mobile mechanical support 34 and the fixed mechanical support 38 is less than the distance d which separates the fixing points 260, 280 of the optical fiber against these supports, more precisely against the surfaces 34e and 38e (see below).

[0293] Figures 16A-16E show various parts of the device of [Fig.15A].

[0294] The piezoelectric element ([Fig.16D]) is of elongated shape, and comprises an internal channel 46a inside which the body 34a of the movable mechanical support can be introduced.

[0295] The fixed mechanical support 38 (figures 16E and 16F) preferably has a cylindrical shape, with:

[0296] - an internal channel 38c parallel to the direction of extension of the fiber 2 and in which the latter can be inserted;

[0297] - a main face 38a, facing the piezoelectric element 46, which can have in its middle a hollow 38d forming a reception volume into which one end of the element 46 can penetrate in order to ensure solid fixing of the latter with the support 38.

[0298] The inner end of this support 38 is hollowed out to form a half-cylinder, as illustrated in FIGS. 16E and 16F, so that a flat surface 38e forms a receiving surface 38e for the fiber, on which it can be fixed.

[0299] When assembling the device, the surfaces 34e and 38e are arranged so as to be located in the same plane, so that the fiber 2 can be positioned and fixed on these 2 surfaces.

[0300] More precisely, fiber 2 is made integral:

[0301] - on the one hand of the surface 34e of the movable mechanical support 34 by means of a anchoring means 280;

[0302] - on the other hand of the surface 38e of the fixed mechanical support by means of a means anchor 260.

[0303] Each anchoring means 260, 280 is for example a glue, or a cement, or an adhesive tape, or thermal projections, or any means allowing the fiber to be fixed.

[0304] During assembly, the movable mechanical support 34 is introduced into the channel 46a of the element 46. Then the fiber 2, provided with its functionalization element 44, is introduced into the channel 34c, along the surface 34e. The structure of [Fig.l5B] is thus obtained.

[0305] The free end of the element 46 is then introduced into the hollow part 38d of the fixed mechanical support, the free end of the fiber enters the channel 38c and runs along the surface 38th.

[0306] Then the surfaces 34th and 38th are aligned with each other.

[0307] An anchoring point 280 makes it possible to fix the fiber on the surface 34e and an anchoring point 260 makes it possible to fix the fiber on the surface 38e. The means 44 are arranged between these 2 points of fixing or anchoring of the fiber.

[0308] In the embodiments presented above, in connection with figures 14A-16F, the distance d between the points 16, 18 or 260, 280 for fixing the fiber, on the one hand on the fixed mechanical support and on the other hand on the mobile mechanical support, is small, less than the extension L of the piezoelectric element itself; in particular, it is possible to have a ratio L / d at least equal to 5 or 10. [Fig. 19] shows schematically the part of the fiber 2 which comprises the element 44 as well as the fixing points 16, 18, on either side of the latter and separated by the distance d.

[0309] Consequently, when activating the element 46, the relative variation Ad / d of the portion of the fiber located between these fixing points is much greater (from 10 to 20 times) than in the case where these points are separated by a distance substantially equal to the length of the element 46; for example Ad / d can be between 0 and 3%, and go up to 3% (i.e. the deformation limit of a fiber in general), therefore in particular be greater than the usual values ​​which are of the order of 0.15% or 0.2%. These variations will affect the optical properties of the functionalization element 4, for example a Bragg grating or a Fabry Pérot cavity. These properties will now be presented.

[0310] Generally speaking, a Bragg grating makes it possible to generate a bandpass filter, which can completely reflect (up to about 100%) the light in a certain region of the spectrum and completely let (up to about 100%) the light pass elsewhere (outside of said region).

[0311] Such a Bragg grating makes it possible to generate very different spectral profiles, for example:

[0312] - a profile showing several peaks in reflection over a range of wavelengths between Xi and X2; for example 2 peaks, one at X'i and the other at X'2(Xi < X'i< X'2< X2), or a multitude of peaks at X'; (i=l,..., n, Xi < X';< X2); such a filter completely reflects the light at X'i and X'2 or at each X'; (i=l,.., n), the light being in fact reflected on a narrow spectral band around each of the wavelengths X'i, X'2, X'; since each peak has a certain spectral width;

[0313] - or a broadband filter profile, between X'i and X'2>; such a filter reflects as completely the light between X'i and X'2 and transmits light outside this spectral band;

[0314] - or a profile comprising a single reflection peak at X'i; such a filter reflects as completely the light at X'i (or on a weak spectral band around X'i).

[0315] The shape of the reflection or transmission spectrum of a Bragg grating and / or the various wavelengths Xb X2, X'b X'2, X'i can be adapted according to the physical properties of the grating, for example according to the writing pitch and / or the writing energy and / or the type of writing implemented (filament grating(s) or bubble grating(s) or plane grating(s)). For example, the spectral width X'2 - X\ of a broadband filter is configurable and is for example between ten or a few tens of nanometers and a hundred nm, for example between 10 nm and 100 nm.

[0316] A Bragg grating can therefore comprise a single reflection peak, or several reflection peaks, or form a broadband filter.

[0317] Thus, it is possible to obtain a bandpass filter with a configurable width (for example up to several tens of nanometers of spectral width).

[0318] A Fabry-Pérot cavity also makes it possible to generate very varied spectral profiles. Here again, the shape of the reflection or transmission spectrum of a Fabry-Pérot cavity can be adapted according to its properties (for example, dimension, and / or reflectivity, etc.). It is possible to modulate the length of the cavity and / or to introduce an effect according to the reflexivity of the faces of the Fabry-Pérot cavity.

[0319] A functionalizing element 44 forms a reflective or transmissive optical element or component or a bandpass filter, which can completely or partially reflect (up to X%, X = 100 or X < 100) the light in a certain region of the spectrum and completely or partially let (up to (100-X)%) the light pass elsewhere (outside said region).

[0320] In the case of a modulation device according to the invention, each modulation of length Ad between the fixing points, on either side of the element 44, imposed by the element 46 also affects the element 4 whose optical properties are in turn modulated.

[0321] It is thus possible:

[0322] - in the case of an element 44 having at rest (or in a first state) a spectrum in reflection between two wavelengths Xi and X2 (as for example in [Fig.5B]), to modulate the spectrum so that in an "excited" state (or second state) of the element 44 the spectrum in reflection is shifted between two other wavelengths X3 and X4 (as for example in [Fig.5C]); thus the light from a laser source having a spectrum lying outside the reflection window of the modulator, but between the wavelengths X3 and X4, is first transmitted ([Fig.5B], first state of the modulator) then, when the modulator is excited ([Fig.5C], second state of the modulator), is reflected, the modulator then acting as an open switch (blocking for the laser wavelength);

[0323] - in the case of a partially reflective element 44, having at rest (or in a first state) a spectrum in partial reflection at X% (0 < X ​​< 100) between two wavelengths Xi and X2 (as for example in [Fig.5D]), to modulate the spectrum so that in an "excited" state (or second state) of the element 44 the spectrum in partial reflection is shifted between two other wavelengths X3 and X4 (as for example in [Fig.5E]); thus the light from a laser source having a spectrum lying outside the reflection window of the modulator, but between wavelengths X3 and X4, is first transmitted ([Fig.l IA], first state of the modulator) then, when the modulator is excited (second state of the modulator), is partially reflected and partially (100-X)% transmitted; the modulator then acts as a partially open switch (partially blocking for the laser wavelength);

[0324] - in the case of an element 44 having at rest (or in a first state) a spectrum in reflection having a rising edge between two wavelengths Xi and X2 (as for example in [Fig.5F]), then a constant value for X > X2, to modulate the spectrum so that, in an "excited" state (or second state) of the element 44, this edge is displaced between two other wavelengths X3 and X4 (as for example in [Fig.5G]); thus the light from a laser source having a spectrum initially within the reflection window of the modulator, but between wavelengths X3 and X4, is first reflected ([Fig.5F], first state of the modulator) then, when the modulator is excited (second state of the modulator), partially transmitted, the modulator then acting as a variable analog modulator (modulating the proportion of laser light transmitted).

[0325] - in the case of an element 44 having at rest (or in a first state) a spectrum in reflection around a single wavelength Xi ([Fig.l7A]), to modulate this spectrum so that in an “excited” state (or second state) of the element 44 the reflection spectrum is shifted around another wavelength X2 ([Fig.l7B]), the element 44 becoming at least partially transparent for the wavelength X^

[0326] Alternatively, shown in [Fig. 18A] and 18B, the modulator may act as a wavelength selector; for example, in the case of a first laser source having a spectrum located in a transmission zone of a modulator, between two wavelengths X3 and X4 and a second laser source having a spectrum located in a reflection zone of the modulator, between two wavelengths X1 and X2:

[0327] - in a first state ([Fig. 18A]), the first laser source is located in the area of transmission of the modulator and the second laser source is located in the reflection zone of the latter; the modulator then acts as a closed (passing) switch for the first laser source and as an open switch for the second laser source;

[0328] - in a second state ([Fig.l8B]), the first laser source is located in the area reflection of the modulator and the second laser source is located in the area of transmission of it; the modulator then acts as a closed (passing) switch for the second laser source and as an open switch for the first laser source.

[0329] In other words, the modulator will make it possible to select the transmitted wavelength.

[0330] Generally speaking, various combinations of the operating modes set out above can be implemented; for example, a modulator can be combined with a wavelength selector.

[0331] In a general manner again, the optical frequencies f and their wavelengths X are linked by the relation f = c / X, where c is the speed of light in a vacuum.

Claims

Claims

1. Bidirectional power supply and communication device, comprising: - at least one optical fiber (2) between a master terminal (4) and at least one slave terminal (6, 6i); - the master terminal (4) comprising a light source (8) at at least one wavelength (X), a photo-detector (10) and means (12) for directing a signal which comes from the slave terminal (6) via the optical fiber (2) to the photo-detector (10) and for directing a signal which comes from the light source (8) to the optical fiber (2); - the slave terminal (6) comprising at least one modulator (24, 34, 44) and a photovoltaic cell (20).

2. Device according to claim 1, the optical fiber (2) being single-mode or multi-mode.

3. Device according to one of claims 1 or 2, the light source (8) being monochromatic.

4. Device according to one of claims 1 to 3: - the master terminal (4) being capable of transmitting, to the slave terminal (6), a continuous light signal and a data signal, at the first wavelength; - the slave terminal (6) being capable of transmitting to the master terminal (4), a data signal, at the first wavelength.

5. Device according to one of claims 1 or 2, the light source (8) further emitting at least one second wavelength (X2), the master terminal (4) further comprising a multiplexer (14) for selecting said first wavelength (Xi) or said second wavelength (X2).

6. Device according to claim 5: - the master terminal (4) being able to transmit, to the slave terminal (6): *a continuous light signal, at the second wavelength; *a data signal, at the first wavelength. - the slave terminal (6) being able to transmit to the master terminal (4), a data signal, at the first wavelength.

7. Device according to claim 5: - the master terminal (4) being capable of transmitting, towards the slave terminal (6), a continuous light signal and a data signal, at the second wavelength; - the slave terminal (6) being capable of transmitting to the master terminal (4), a data signal, at the first wavelength.

8. Device according to one of claims 1 to 7, the slave terminal (6) comprising at least one coupler / separator (26), the modulator (24) and the photovoltaic cell (20) being mounted in parallel.

9. Device according to one of claims 1 to 8, the master terminal (4) being capable of transmitting, to the slave terminal (6), an offset signal, the slave terminal (6) being capable of transmitting to the master terminal (4), a data signal, by modulating the offset signal.

10. Device according to one of claims 1 to 9, further comprising means for carrying out: - a frequency modulation, at a first frequency (fpl), of the signals transmitted from the master terminal (4) to the slave terminal (6), - a frequency modulation, at a second frequency (fp2), of the signals transmitted from the slave terminal (6) to the master terminal (6).

11. Device according to one of claims 1 to 10, comprising a plurality of slave terminals (6i), means (27) for coupling between the optical fiber (2) and said plurality of slave terminals (6i).

12. Device according to one of claims 1 to 10, comprising a plurality of slave terminals (6i), and an optical fiber (2;) between the master terminal (4) and each of the slave terminals (6;).

13. Device according to one of claims 1 to 10, the modulator (44) being a spectral modulator.

14. Device according to claim 13, the spectral modulator (44) comprising a Bragg grating and / or a Fabry Pérot cavity associated with at least one mechanical stress generator (46) and / or a heating and / or cooling element.

15. Device according to claim 13, the spectral modulator (44) comprising: - a portion of said optical fiber (2) extending at least partly along an axis (XX') and comprising optical functionalization means (44), presenting a spectrum in reflection of a portion of a light radiation circulating in the fiber; - an element (46) deformable in a direction parallel to the same axis (XX') and having a length L; - a first mechanical element (80) and a second mechanical element (14) fixed to the deformable element (46) and capable of undergoing a relative deformation or a relative displacement under the action of this element (46) de- formable, said optical fiber being fixed to the first mechanical element (80) at a first fixing point (16, 260) and to the second mechanical element (14) at a second fixing point (18, 280), these 2 fixing points being arranged on either side of the optical functionalization means (44), the distance (d) between the first fixing point and the second fixing point being less than the length (L) of the deformable element (46), the ratio L / d being at least equal to five.

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