WO2023275332A1 - Lidar impulsionnel à amplificateur optique à semi-conducteur piloté par un signal modulé - Google Patents
Lidar impulsionnel à amplificateur optique à semi-conducteur piloté par un signal modulé Download PDFInfo
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- WO2023275332A1 WO2023275332A1 PCT/EP2022/068209 EP2022068209W WO2023275332A1 WO 2023275332 A1 WO2023275332 A1 WO 2023275332A1 EP 2022068209 W EP2022068209 W EP 2022068209W WO 2023275332 A1 WO2023275332 A1 WO 2023275332A1
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- 230000003287 optical effect Effects 0.000 title claims abstract description 19
- 239000004065 semiconductor Substances 0.000 title claims abstract description 11
- 238000005259 measurement Methods 0.000 claims abstract description 14
- 238000005086 pumping Methods 0.000 claims description 113
- 230000003247 decreasing effect Effects 0.000 claims description 92
- 238000000034 method Methods 0.000 claims description 39
- 239000013307 optical fiber Substances 0.000 claims description 3
- 230000006870 function Effects 0.000 description 46
- 230000007423 decrease Effects 0.000 description 18
- 230000001427 coherent effect Effects 0.000 description 14
- 238000001514 detection method Methods 0.000 description 14
- 230000003595 spectral effect Effects 0.000 description 14
- 238000001228 spectrum Methods 0.000 description 12
- 230000002238 attenuated effect Effects 0.000 description 6
- 230000003321 amplification Effects 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 239000000835 fiber Substances 0.000 description 5
- 238000003199 nucleic acid amplification method Methods 0.000 description 5
- 230000003121 nonmonotonic effect Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
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- 238000004146 energy storage Methods 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
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- 239000007924 injection Substances 0.000 description 1
- 238000007620 mathematical function Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
- G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/484—Transmitters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/95—Lidar systems specially adapted for specific applications for meteorological use
Definitions
- Pulse LIDAR with semiconductor optical amplifier driven by a modulated signal.
- LIDARs are, among other things, used for observing the atmosphere and determining the properties of the atmosphere.
- the properties of the atmosphere determined can be, in particular, the speed of the wind, the concentration of particles in the atmosphere, their dimensions and/or their shape, and the temperature of the atmosphere.
- the present invention relates to the modulation and amplification of pulsed optical signals used, in particular, by such LIDARs.
- the present invention aims, in particular, to generate pulsed signals at high rate, low spectral width and with adjustable frequency.
- the present invention relates to pulsed LIDARs with an optical amplifier.
- the invention relates, more specifically, to a pulsed LIDAR with a semiconductor optical amplifier, known as SOA for semiconductor optical amplifier, and to a method for amplifying such a LIDAR.
- SOA semiconductor optical amplifier
- Patent document FR1461407 is known in the state of the art, which deals with LIDAR with a semiconductor optical amplifier, known as SOA-LIDAR. This document describes the use of an SOA arranged to ensure the intensity modulation function of the master laser beam and the amplification function of the master laser beam.
- a drawback of state-of-the-art SOA-LIDARs is that they do not allow to determine the sign of the wind speed. To determine the sign of the wind speed, it is therefore necessary to incorporate an Acousto-Optical Modulator (AOM) or an optical demodulator in phase quadrature in order to be able to determine the sign of the wind speed.
- AOM Acousto-Optical Modulator
- the MAO introduces a given frequency shift on the amplified signal with respect to the signal of the local oscillator, that is to say the master laser. This frequency offset must be controlled, precise and constant. This frequency shift determines the sign of the wind speed during heterodyne detection.
- SOA-LIDARs Another disadvantage of state-of-the-art SOA-LIDARs is due to the non-linearity of the transfer function of the SOA which has the consequence that the signal amplified and modulated by the SOA is not square and symmetrical. This causes a spectral spreading of the amplified and modulated signal and a drop in the signal to noise ratio.
- SOA-LIDARs introduce a drift in the frequency of the signal modulated and amplified by the SOA and a broadening of the measured Doppler peak as well as the appearance of secondary peaks .
- Frequency drift can introduce a shift in the measured wind speed value. Broadening of the measured Doppler peak as well as secondary peaks decrease the accuracy and reproducibility of the measurements.
- An object of the invention is in particular:
- a pulsed LIDAR comprising:
- a pulse generator arranged to generate a pumping signal comprising at least one pulse whose peak value varies during said at least one pulse of said pumping signal and/or to keep constant or to vary a phase of at least one pulse of the signal amplified and modulated by the SOA,
- a semiconductor optical amplifier arranged to amplify and modulate the master laser beam according to the pump signal, the amplified and modulated master laser beam forming a measurement laser beam.
- the peak value of the at least one pulse of the pumping signal can vary over all or part of the at least one pulse.
- the phase of the at least one pulse of the signal amplified and modulated by the SOA can be constant or can vary over all or part of the at least one pulse of the signal amplified and modulated by the SOA.
- the term “signal” used alone can designate the pump signal and/or the pulsed signal and/or the signal amplified and modulated by the SOA and/or the phase of the signal amplified and modulated by the SOA.
- the master laser beam amplified and modulated by the SOA or the measurement laser beam can be referred to as a signal amplified and modulated by the SOA.
- the signal amplified and modulated by the SOA is a pulsed signal.
- a pulse can comprise a peak value and a rise and/or a fall.
- the pulse generator may include:
- control unit arranged to vary the at least one pulse of the pump signal, preferably respectively the peak value, a rise and/or a fall of the at least one pulse of the pump signal, by modulation of the pulse signal, preferably by respective modulation of a peak value, of a rise and/or of a fall of at least one pulse of the pulse signal produced by the electric generator.
- the pump signal corresponds respectively to the pulse signal modulated by the control unit, preferably to the at least one pulse of the pulse signal modulated by the 'control unit.
- the control unit can be arranged to vary the phase of at least one pulse of the signal amplified and modulated by the SOA by modulating the pulse signal produced by the electric generator.
- the control unit is arranged to vary the peak value of one, several or each of the pulses of the pulse signal produced by the electric generator.
- the control unit can be arranged to modulate at least one pulse of the pulse signal.
- control unit is arranged to modulate the peak value of at least one pulse of the pulse signal.
- the control unit can be arranged to modulate at least one pulse of the pulse signal and not to modulate at least one pulse of the pulse signal, preferably to modulate the peak value of at least one pulse of the pulse signal and to not modulating the peak value of at least one pulse of the pulse signal.
- peak value and/or “rise” and/or “fall” used alone can designate the peak value and/or the rise and/or the fall of the pumping signal and/or the pulsed signal and/or of the signal amplified and modulated by the SOA and/or of the phase of the signal amplified and modulated by the SOA.
- the pulse generator is arranged to vary a phase and/or a frequency of the signal amplified and modulated by the SOA by modulating the at least one pulse of the pumping signal, preferably by modulating the value of peak, of the rise and/or of the fall of the at least one pulse of the pumping signal, more preferably by modulating the variation of the peak value of the at least one pulse of the pumping signal.
- control unit is arranged to vary a phase and/or a frequency of the signal amplified and modulated by the SOA by modulating the at least one pulse of the pulsed signal, preferably by modulating the rise and /or the descent of the at least one pulse of the pulse signal, more preferably by modulation of the peak value of the at least one pulse of the pulse signal.
- the control unit can be arranged to vary a phase of at least one pulse of the signal amplified and modulated by the SOA, preferably by modulation of the pulse signal.
- the control unit can be arranged for:
- phase of the at least one pulse of the signal amplified and modulated by the SOA in an increasing manner, preferably over at least one time interval of the at least one pulse, and/or in a decreasing manner, preferably over at least one time interval of the at least one pulse of the signal amplified and modulated by the SOA.
- the control unit can be arranged to vary the phase of the at least one pulse of the signal amplified and modulated by the SOA so that an average value of the phase over a time interval of the at least one pulse of the signal amplified and modulated by the SOA, preferably over a time interval of at least one pulse of the signal amplified and modulated by the SOA over which the phase is increasing or decreasing respectively, or equal to an average value of the phase over another time interval of at least one pulse of the signal amplified and modulated by the SOA, preferably over a time interval of at least one pulse of the signal amplified and modulated by the SOA over which the phase is increasing or decreasing respectively.
- the control unit can be arranged to vary the phase of the at least one pulse of the signal amplified and modulated by the SOA so that an average value of the phase over a time interval of the pulse of the amplified signal and modulated by the SOA, preferably over a time interval of the pulse of the signal amplified and modulated by the SOA over which the phase is increasing or decreasing respectively, either lower or higher than an average value of the phase over another time interval of the pulse of the signal amplified and modulated by the SOA, preferably over a time interval of the pulse over which the phase is increasing or decreasing respectively.
- the control unit can be arranged to vary the phase of the at least one pulse of the signal amplified and modulated by the SOA so that a value of the phase varies by modulo 2n at least once during the at least one pulse of the signal amplified and modulated by the SOA.
- control unit can be arranged to vary the phase of the at least one pulse of the signal amplified and modulated by the SOA so that a value of the phase varies by modulo 2n several times, preferably periodically, during the at least one pulse of the signal amplified and modulated by the SOA.
- the control unit can be arranged to vary the phase of the at least one pulse of the signal amplified and modulated by the SOA according to a pattern or a triangular shape.
- control unit can be arranged to vary the phase of the at least one pulse of the signal amplified and modulated by the SOA according to a pattern or a triangular shape.
- one or more, preferably each, pulse of the pump signal and/or of the pulse signal and/or of the signal amplified and modulated by the SOA and/or of the phase of the amplified signal and modulated by the SOA may comprise, preferably consists of, a signal rise, a peak signal and a signal fall.
- the rise of the signal takes place from a minimum level, which may be a local minimum, of the signal up to the peak signal.
- the minimum level of the signal corresponds to a null value of the signal.
- the descent of the signal takes place from the peak signal to the minimum level of the signal, which is that from which the rise takes place, or to a local minimum of the signal which is different from the level minimum from which the ascent takes place.
- the peak signal of a pulse can correspond to the part of the signal of the pulse comprised between the end of the rise of the pulse and the start of the fall of the pulse.
- the peak signal corresponds to the plateau, that is to say to the constant and maximum value of the signal, which is between the end of the rise of the pulse and the beginning of the fall of the pulse.
- the peak signal of a pulse can be understood to mean all of the values of the signal comprised between a value of the signal at the end of the rise of the pulse and a value of the signal at the start of the fall of the pulse.
- one or more, preferably each, pulse of the pumping signal and/or of the pulsed signal and/or of the signal amplified and modulated by the SOA and/or the phase of the signal amplified and modulated by the SOA may include a rise or fall and a peak signal.
- a pulse considered corresponds either to a pulse according to the first aspect or to a pulse according to the second aspect.
- a pulse may comprise, preferably comprises only, more preferably consists of, more preferably consists only of:
- a pulse may comprise, preferably comprises only, more preferably consists of, more preferably consists only of, a rise followed by a peak signal.
- the rise of the signal takes place from then a minimum level, which can be a local minimum, of the signal up to a maximum level, which can be a local maximum, of the signal.
- the minimum level of the signal corresponds to a null value of the signal.
- the peak signal of the pulse can correspond to the part of the signal of the pulse between the maximum level of the signal and the minimum level of the signal, which is that from which the rise takes place, or a local minimum of the signal which is different from the minimum level from which the rise takes place.
- a pulse may comprise, preferably comprises only, more preferably consists, more preferably consists only, of a peak signal followed by a fall.
- the peak signal of the pulse may correspond to the part of the signal of the pulse comprised between a minimum level, which may be a local minimum, of the signal up to a level maximum, which may be a local maximum, of the signal.
- the minimum level of the signal corresponds to a null value of the signal.
- the descent of the signal takes place from the maximum level of the signal to the minimum level of the signal, which is that from which the peak signal extends, or to a local minimum of the signal which is different from the minimum level from which the peak signal extends.
- a pulse may comprise, preferably comprises only, more preferably consists, more preferably consists only, of a peak signal.
- the peak signal preferably corresponds to the pulse signal.
- the peak signal preferably the pulse signal, may include:
- a minimum level of the signal which can be a local minimum of the signal, preferably which is the level from which the peak signal extends, up to a maximum level of the signal, which may be a local maximum of the signal, and/or, preferably followed or preceded by, preferably still followed by,
- the maximum level of the signal which can be a local maximum, of the signal up to the minimum level of the pump signal, which can be a local minimum of the signal, preferably which is that from which the peak signal extends, or to a local minimum of the pump signal which is different from the minimum level from which the peak signal extends
- the pump signal and/or the pulse signal and/or the signal amplified and modulated by the SOA and/or the phase of the signal amplified and modulated by the SOA comprises:
- the signal and/or the peak value and/or the rise and/or the fall can be defined by, or can vary according to or be modulated according to, a mathematical function and/or a periodic function.
- signal can be understood to mean all of the values of the signal in question.
- peak signal used herein may refer but does not refer solely to peak power.
- peak signal used in the context of the present application may refer but does not refer solely to the peak power of the measurement signal.
- the peak signal of a pulse can correspond to all of the peak values of the pulse considered.
- the signal may comprise successive pulses which are identical or different from each other.
- one or more, preferably each, pulse of the signal is periodic.
- the pulse generator is an arbitrary signal generator.
- control unit is arranged to vary the peak value of each pulse of the pumping signal by modulating each pulse of the pulsed signal.
- control unit is arranged to vary the peak value of each pulse of the pumping signal by modulating the peak value of each pulse of the pulsed signal.
- the characteristics relating to the pulse can be transposed to the phase of the pulse of the signal amplified and modulated by the SOA.
- the phase of the pulse of the signal amplified and modulated by the SOA may have the same characteristics as that of the peak signal of at least one pulse of the pumping signal according to the invention.
- the peak value of the at least one pump signal pulse may vary monotonically over at least one time interval of the at least one pump signal pulse.
- the control unit can be arranged to vary the peak value of the at least one pulse of the pumping signal in a monotone manner over at least one time interval of the at least one pulse of the pumping signal by modulation of the at least one pulse of the pulse signal produced by the electric generator, preferably by modulating the peak value of the at least one pulse of the pulse signal produced by the electric generator.
- the control unit can be arranged to cause all or part of the peak value of the at least one pulse of the pumping signal to vary linearly by modulating the at least one pulse of the pulse signal produced by the electric generator.
- the control unit can be arranged to cause a succession of peak values to vary linearly, for example a succession of segments of peak values of the at least one pulse of the pumping signal by modulation of the at least one pulse of the pulse signal produced by the electric generator.
- the control unit can be arranged to generate a function of peak values of at least one pulse of the pumping signal by modulating the at least one pulse of the pulse signal produced by the electrical generator.
- time interval of the pulse a time interval comprised in the duration of the pulse.
- control unit can be arranged to cause all or part of the peak signal of the at least one pulse of the pumping signal to vary monotonically by modulating the at least one pulse of the pulse signal produced by the electric generator.
- control unit can be arranged to make the peak signal vary by a time interval of a given pulse of the pump signal, by modulating the at least one pulse of the pulse signal produced by the electric generator, regardless of the peak signal of another time interval of the given pulse of the pump signal.
- the peak value of the at least one pump signal pulse may vary monotonically over the entire duration of the at least one pump signal pulse.
- the control unit can be arranged to vary the peak value of the at least one pulse of the pumping signal in a monotone manner over the entire duration of the at least one pulse of the pumping signal by modulation of the at least one pulse of the pulse signal produced by the electric generator.
- the peak value of the at least one pulse of the pump signal can vary in an increasing manner over at least one time interval of the at least one pulse of the pump signal and/or can vary in an increasing manner over at least a time interval of the at least one pulse of the pump signal.
- the control unit can be arranged to vary the peak value of the at least one pulse of the pumping signal in an increasing manner over at least one time interval of the at least one pulse of the pumping signal by modulation of the at least one pulse of the pulse signal produced by the electric generator, preferably by modulating the peak value of the at least one pulse of the pulse signal produced by the electric generator and/or in a decreasing manner over at least a time interval of the at least one pulse of the pump signal by modulating the at least one pulse of the pulse signal produced by the electric generator, preferably by modulating the peak value of the at least one pulse of the pulse signal produced by the electric generator.
- the control unit can be arranged to generate at least one increase and at least one decrease, or vice versa, of the peak value of at least one pulse of the pump signal by modulating the at least one pulse of the pulse signal .
- the peak value of the pump signal before the first of the increases among the at least one increase is equal to the value of the pump signal at the end of the rise of the pulse.
- the peak value of the pump signal after the last of the increases among the at least one increase is equal to the value of the pump signal at the start of the descent of the pulse.
- the peak value of the at least one pulse of the pumping signal varies alternately or successively, increasing then decreasing, or vice versa.
- the peak value of the at least one pulse of the pumping signal can vary so as to form an alternation between, or succession of, a time interval over which the peak value is increasing and an interval of time over which the peak value is decreasing, or vice versa.
- the peak value of the at least one pulse of the pump signal varies according to a triangular function.
- a speed of increase in the peak value of the signal that is to say a speed at which the peak value of the signal increases or increases, and/or a speed of decrease in the peak value of the signal, it is a rate at which the peak value of the signal decays or decreases, may be equal to or greater than two, preferably five, more preferably ten, even more preferably 100 and most preferably between all of them at 1000.
- the rate at which the peak signal value increases may be different from the rate at which the peak signal value decreases.
- a ratio between the speed of the at least one decrease in the peak value of the signal and the speed of the at least one increase in the peak value of the signal is equal to or greater than one, preferably at two, more preferably five, more preferably ten, of even more preferably 100 and most preferably 1000.
- the speed of the at least one decrease in the peak value of the signal can be equal to the speed of the descent of the signal.
- the rate of rise, fall, increase and decrease can be defined as the variation of the signal per second.
- the pump signal can be a voltage, an intensity or a luminous flux.
- the peak value of the pump signal can be expressed in Volts (V), in Amperes (A) or in Watts (W) or in Watts per second (W/s), or an arbitrary unit.
- the rate of rise, fall, increase or decrease can be defined in Volts per second or in Amps per second or in Watts per second.
- the ascent speed (or the ascent) and/or the descent speed (or the descent) can be, preferably strictly, greater than or equal, preferably strictly greater than or equal, in absolute value , at 1.10 8 Amps per second (A/s) and more preferably at 1.10 9 A/s.
- the speed of increase (or the increase) and/or the speed of decrease (or the decrease) can be less than or equal, preferably strictly less than or equal, in absolute value, to 2.10 8 A/s, preferably 1.10 7 A/s, more preferably 1.10 6 A/s.
- the speed of increase (or increase) and/or the speed of decrease (or decrease) may be greater, in absolute value, than 1.10 4 A/s and/or greater than , in absolute value, at 1.10 5 Amps per second (A/s).
- the variation of the peak value of the signal can take place at the speed of rise over at least a time interval of at least one pulse and/or of descent over at least a time interval of at least one pulse and/or at the speed of increase over at least a time interval of at least one pulse and/or at the speed of descent over at least a time interval of at least one pulse.
- the variation of the peak value of the pump signal at the rise and/or fall speed generates a non-zero variation of the phase P of the signal amplified and modulated by the SOA.
- the variation of the peak value of the pumping signal at the speed of increase and/or decrease generates a zero variation of the phase P of the signal amplified and modulated by the SOA, that is to say a constant phase.
- the peak value of the at least one pulse of the pump signal may comprise an average peak value over a time interval of the at least one pulse of the pump signal, preferably over a time interval of at least one pulse of the pump signal over which the peak value is increasing or decreasing, which is equal to an average peak value over another time interval of the at least one pulse of the pump signal, preferably over a time interval of the pulse of the pump signal over which the peak value is increasing or decreasing.
- the control unit can be arranged to vary, preferably by modulation of the at least one pulse of the pulse signal, more preferably by modulation of the peak value of the at least one pulse of the pulse signal, produced by the electrical generator, the peak value of the at least one pulse of the pump signal so that an average peak value over a time interval of the at least one pulse of the pump signal, preferably over a time interval of the at least one pump signal pulse over which the peak value is increasing or decreasing, or equal to an average peak value over another time interval of the at least one pump signal pulse pump page, preferably over a time interval of at least one pulse of the pump signal over which the peak value is increasing or decreasing respectively.
- the intervals of the at least one pulse over which the peak value of the at least one pulse of the pumping signal is increasing have the same average peak value.
- the intervals of the at least one pulse over which the peak value of the at least one pulse of the pumping signal is decreasing have the same mean peak value.
- the intervals of the at least one pulse over which the peak value of the at least one pulse of the pump signal is increasing and the intervals of the pulse over which the peak value of the at least one pulse of the pumping signal is decreasing have an average peak value which is identical.
- each of the intervals of the at least one pulse over which the function of the peak value of the at least one pulse of the pumping signal is increasing or decreasing can have an average peak value which is identical to each of the peak values of the other intervals of the at least one pulse over which the function of the peak value of the at least one pulse of the pumping signal is increasing or decreasing.
- the average peak value over a considered time interval of the at least one pulse over which the function, of the peak value of the at least one pulse of the pumping signal, is increasing or decreasing is:
- the average value of a quantity by way of non-limiting example of the phase of the pulse or of the intensity of the pulse, or else of the peak value of the pulse or of the value of the phase of the pulse or of the peak value of the phase of the pulse, over a time interval, can be defined as being equal to the arithmetic mean of all the values taken by the quantity in question about the time interval.
- the peak value of the at least one pulse of the pump signal may comprise an average peak value over a time interval of the at least one pulse of the pump signal, preferably over a time interval of at least one pulse of the pump signal over which the peak value is increasing or decreasing, which is lower or higher than an average peak value over another time interval of the au least one pulse of the pump signal, preferably over a time interval of the at least one pulse of the pump signal over which the peak value is increasing or decreasing.
- the control unit can be arranged to vary the peak value of the at least one pulse of the pump signal, preferably by modulating the at least one pulse of the pulse signal, more preferably by modulating the value peak value of the at least one pulse of the pulse signal, produced by the electric generator, so that an average peak value over a time interval of the at least one pulse of the pump signal, preferably over a time interval of the at least one pulse of the pump signal over which the peak value is increasing or decreasing, either lower or higher than an average peak value over another time interval of the at least one pulse of the pumping signal, preferably over a time interval of at least one pulse of the pumping signal over which the peak value is increasing or decreasing.
- the intervals of the at least one pulse over which the peak value of the at least one pulse of the pumping signal is increasing each have a different average peak value, that is to say higher or lower .
- the intervals of the at least one pulse over which the peak value of the at least one pulse of the pumping signal is decreasing each have a different mean peak value.
- the intervals of the at least one pulse over which the peak value of the at least one pulse of the pumping signal is increasing have an average peak value which is different from the average peak value of the intervals of the pumping signal.
- the average peak value over a considered time interval of the at least one pulse over which the peak value of the at least one pulse of the pumping signal is increasing, or respectively decreasing is:
- the average peak value over a considered time interval of the at least one pulse, over which the peak value of the at least one pulse of the pumping signal is increasing or decreasing is:
- the control unit can comprise at least one switch arranged to control and/or modulate the pulse signal.
- the at least one switch may be a transistor.
- the transistor may be a metal-oxide gate field-effect transistor, denoted MOS.
- MOS metal-oxide gate field-effect transistor
- the transistor may be of the N type, that is to say an N MOS transistor, or of the P type, that is to say a PMOS transistor.
- the at least one switch can be arranged to vary the pumping signal by modulation and/or switching of the pulse signal emitted by the electric generator.
- the LIDAR may include a fiber optic amplifier arranged to amplify the master laser beam amplified and modulated by the SOA.
- the LIDAR, or a control unit of the LIDAR or the SOA, can be arranged to vary a peak value, preferably linearly increasing or decreasing, of the master laser beam amplified and modulated by the SOA.
- the LIDAR or a control unit of the LIDAR or the SOA, can be arranged to vary a peak value, preferably linearly increasing or decreasing, of the master laser beam amplified and modulated by the SOA so that the signal, or the average signal or the power or the average power, of the laser beam amplified by the fiber optic amplifier, i.e. the master laser beam amplified and modulated by the SOA and then amplified by the fiber optic amplifier is constant on the at least one pulse.
- a pump signal preferably by means of a pulse generator, comprising at least one pulse whose peak value varies during said at least one pulse of said pump signal, preferably generating a pump signal comprising at least one pulse whose peak value, rise and/or fall varies during said at least one pulse of said pump signal and/or, preferably, maintain constant or vary a phase by at least least one pulse of the signal amplified and modulated by the SOA,
- the method may comprise the step of varying the peak value of the at least one pulse of the pump signal by modulating, preferably by means of a control unit, at least one pulse of a signal pulsed, preferably by modulation of a peak value, a rise and/or a fall of at least one pulse of the pulse signal, which can be produced by an electric generator.
- the method may comprise the step consisting in varying, preferably by means of the pulse generator, a phase and/or a frequency of the signal amplified and modulated by the SOA by modulating the at least one pulse of the pump signal, preferably by modulating the peak value, the rise and/or the fall of the at least one pulse of the pump signal, more preferably by modulating the variation of the peak value of the at least one pulse of the page pump signal.
- the method may comprise the step consisting in varying, preferably by means of the control unit, a phase and/or a frequency of the signal amplified and modulated by the SOA by modulation of the at least one pulse of the pulsed signal, preferably by modulating the rise and/or the fall of the at least one pulse of the pulsed signal, more preferably by modulating the peak value of the at least one pulse of the pulsed signal.
- the method may include the step of varying the phase of the at least one pulse of the signal amplified and modulated by the SOA, preferably by modulation of the pulse signal, preferably by means of the control unit.
- the method may include the steps of:
- the method may comprise the step consisting in shifting a frequency of the at least one pulse of the signal amplified and modulated by the SOA proportionally to a variation gradient of the phase of the at least one pulse of the amplified and modulated signal by the SOA over the at least one time interval of the at least one pulse over which the phase is increasing or decreasing.
- the method may include the step of varying the phase of the at least one pulse of the signal amplified and modulated by the SOA such that an average value of the phase over a time interval of the at least one pulse of the signal amplified and modulated by the SOA, preferably over a time interval of at least one pulse of the signal amplified and modulated by the SOA over which the phase is increasing or decreasing respectively, or equal to an average value of the phase over another time interval of at least one pulse of the signal amplified and modulated by the SOA, preferably over a time interval of at least one pulse of the signal amplified and modulated by the SOA over which the phase is increasing or decreasing respectively.
- the method may include the step of varying the phase of the at least one pulse of the signal amplified and modulated by the SOA so that an average value of the phase over a time interval of the pulse of the amplified signal and modulated by the SOA, preferably over a time interval of the pulse of the signal amplified and modulated by the SOA over which the phase is increasing or decreasing respectively, either lower or higher than an average value of the phase over another time interval of the pulse of the signal amplified and modulated by the SOA, preferably over a time interval of the pulse over which the phase is increasing or decreasing respectively.
- the method may comprise the step consisting in varying the phase of the at least one pulse of the signal amplified and modulated by the SOA so that, for at least one pulse considered, a value of the phase varies by modulo 2n over at at least one time interval of the considered at least one pulse of the signal amplified and modulated by the SOA, i.e. the value of the phase varies by modulo 2n at least once during the at least one least one considered pulse of the signal of the signal amplified and modulated by the SOA.
- the method may comprise the step consisting in varying the phase of the at least one pulse of the signal amplified and modulated by the SOA so that, for at least one pulse considered, a value of the phase varies modulo 2n over several time intervals of the considered at least one pulse of the signal amplified and modulated by the SOA, i.e. the value of the phase varies by modulo 2n several times during the at least one pulse of the signal amplified and modulated by the SOA.
- the method may comprise the step consisting in varying the phase of the at least one pulse of the signal amplified and modulated by the SOA so that an average value of the phase P over a considered time interval of the at least a pulse on which the phase is increasing, or respectively decreasing, is:
- the method may comprise the step consisting in varying the phase of the at least one pulse of the signal amplified and modulated by the SOA so that an average value of the phase P over a considered time interval of the at least a pulse on which the phase is increasing, or respectively decreasing, is
- the peak value of the pump signal can be varied, preferably by modulation of the pulse signal, preferably by means of the control unit, so that during a pulse a signal amplified and modulated by the SOA , a phase of the signal amplified and modulated by the SOA: - either constant or kept constant, or
- the peak value of the pump signal may vary so that, during the at least one pulse of a signal amplified and modulated by the SOA, an average value of the phase over a time interval of the at least a pulse of the signal amplified and modulated by the SOA, preferably over a time interval of the at least one pulse of the signal amplified and modulated by the SOA on which the phase is increasing or decreasing respectively, is equal to an average value of the phase over another time interval the at least one pulse of the signal amplified and modulated by the SOA, preferably over a time interval of the at least one pulse of the signal amplified and modulated by the SOA on which the phase is increasing or decreasing respectively.
- the peak value of the pump signal may vary so that, during one pulse of a signal amplified and modulated by the SOA, an average value of the phase over a time interval of the at least one pulse of the signal amplified and modulated by the SOA, preferably over a time interval of at least one pulse of the signal amplified and modulated by the SOA over which the phase is increasing or decreasing respectively, either lower or higher than an average value of the phase over another time interval of the at least one pulse of the signal amplified and modulated by the SOA, preferably over a time interval of the at least one pulse of the signal amplified and modulated by the SOA over which the phase is increasing or decreasing respectively.
- the peak value of the at least one pulse of the pump signal can:
- the at least one time interval of the at least one pulse of the pump signal over which the peak value varies monotonically and/or the at least one time interval of the at least one pulse of the pump signal over which the peak value is increasing and/or the at least one time interval of the at least one pulse of the pump signal over which the peak value is increasing may be all or part of the total duration of the at least one pump signal pulse
- the variation of the peak value of the at least one pulse of the pump signal can comprise, or be or consist of, a triangular signal.
- the peak value of the at least one pump signal pulse may vary monotonically over the entire duration of the at least one pump signal pulse.
- a frequency of at least one pulse of the signal amplified and modulated by the SOA can be shifted, adjusted or modulated according to a gradient of the peak value of the at least one pulse of the pump signal on the at least a time interval of the at least one pump signal pulse over which the peak value increases and/or as a function of a gradient of the peak value of the at least one pump signal pulse over the at least one time interval of the at least one pulse of the pump signal over which the peak value is decreasing.
- the frequency of at least one pulse of the signal amplified and modulated by the SOA is shifted:
- the peak value of the at least one pulse of the pump signal preferably the peak value, the rise and/or the fall of the at least one pulse of the pump signal, and/or
- the control unit by modulating, preferably by means of the control unit, the at least one pulse of the pulse signal, more preferably the peak value, the rise and/or the fall of at least one pulse of the pulse signal, which can be produced by an electric generator.
- the “gradient of the peak value of the at least one pulse of the pumping signal” can be the guiding coefficient of the peak value of the at least one pulse of the pumping signal on which the function is increasing or decreasing.
- the gradient of the peak value of the pump signal is identical over each of the time intervals of the pulse over which the peak value is increasing or decreasing.
- the peak value of the at least one pulse of the pumping signal is increasing over at least one time interval of the at least one pulse of the pumping signal and decreasing over at least one time interval of l at least one pulse of the pump signal so that a frequency of the at least one pulse of the signal amplified and modulated by the SOA is shifted, adjusted or modulated according to the peak value of the at least one pulse of the pump signal.
- the peak value of the at least one pulse of the pumping signal is increasing over at least one time interval of the at least one pulse of the pumping signal and decreasing over at least one time interval of l at least one pulse of the pump signal so that a frequency of the at least one pulse of the signal amplified and modulated by the SOA is shifted, adjusted or modulated as a function of, preferably proportional to, the rate of variation of the peak value of the at least one pulse of the pump signal.
- the peak value of the at least one pulse of the pumping signal is increasing over at least one time interval of the at least one pulse of the pumping signal and decreasing over at least one time interval of the at least a pulse of the pump signal
- - a variation of the peak signal, over the at least one time interval over which the peak signal is increasing, or respectively decreasing, is greater, in absolute value, than 1.10 8 Amps per second (A/s) and of more preferably at 1.10 9 A/s or even at 1.10 10 A/s, and
- a variation of the peak signal, over the at least one time interval over which the peak signal is decreasing, or respectively increasing, is less, in absolute value, than 1.10 8 Amps per second (A/s) and of my most preferred manner less than or equal to 1.10 7 A/s; preferably a variation of the peak signal, over the at least one time interval over which the peak signal is decreasing, or respectively increasing, at a speed, called the speed of variation of the peak value, which is greater, in absolute value, at 1.10 4 Amps per second (A/s), preferably at 1.10 5 Amps per second (A/s) and/or preferably less than or equal to 1.10 6 A/s, more preferably less than or equal to 1.10 7 A/s and so still more preferably less than 1.10 8 A/s, so that a frequency of the at least one pulse of the signal amplified and modulated by the SOA is shifted, adjusted or modulated according to the rate of variation of the peak value of the at least one pulse of the pump signal or, preferably, either or modul
- the peak value of the at least one pulse of the pump signal may comprise an average peak value over at least one time interval of the at least one pulse of the pump signal, preferably over the at least one interval of time over which the peak value is increasing or over the at least one time interval over which the peak value is decreasing, which is equal to an average peak value over at least one other time interval of the at least one pulse of the pump signal, preferably over the at least one time interval over which the peak value is increasing or over the at least one time interval over which the peak value is decreasing.
- the peak value of the at least one pulse of the pump signal can vary, preferably by modulation, preferably by means of the control unit, of the at least one pulse of the pulse signal, more preferably by modulation of the peak value, of the rise and/or of the fall of the at least one pulse of the pulse signal, which can be produced by an electric generator, so that an average peak value over at least an interval of time of the at least one pump signal pulse, preferably over the at least one time interval over which the peak value is increasing or over the at least one time interval over which the peak value is decreasing , either equal to an average peak value over at least one other time interval of the at least one pumping signal pulse, preferably over the at least one time interval over which the peak value is increasing, or over the at least one time interval over which and the peak value is decreasing.
- the peak value of the at least one pump signal pulse may include an average peak value over at least an interval of time of the at least one pump signal pulse, preferably over the at least one time interval over which the peak value is increasing or over the at least one time interval over which the peak value is decreasing , which is lower or higher than an average peak value over at least one other time interval of the at least one pump signal pulse, preferably over the at least one time interval over which the peak value is increasing or over the at least one time interval over which the peak value is decreasing.
- the peak value of the at least one pulse of the pump signal can vary, preferably by modulation, preferably by means of the control unit, of the at least one pulse of the pulse signal, more preferably by the peak value, of the rise and/or of the fall of at least one pulse of the pulse signal, which can be produced by an electric generator, so that an average peak value over at least a time interval of l at least one pulse of the pump signal, preferably over the at least one time interval over which the peak value is increasing or over the at least one time interval over which the peak value is decreasing, or less or greater than an average peak value over at least one other time interval of the at least one pump signal pulse, preferably over the at least one time interval over which the peak value is increasing or over the at least one time interval on the which the peak value is decreasing.
- the method may include measuring data relating to a phase of the signal amplified and modulated by the SOA.
- the data measurement of the phase of the signal amplified and modulated by the SOA can be carried out by a phase quadrature detector, coherent detector or phase quadrature optical demodulator.
- the method may include determining the modulation of the at least one pulse of the pulse signal and/or the variation of the at least one pulse of the pump signal from data:
- the method can be implemented without, that is to say can not include, the step of calibrating the peak value, that is to say the step of determining the modulation of the at least one pulse of the pulse signal and/or of the variation of the at least one pulse of the pump signal.
- the method may not include the step of measuring or determining the data relating to the phase of the signal amplified and modulated by the SOA.
- These data can be collected beforehand and/or independently of the method according to the invention.
- the data relating to the phase of the signal amplified and modulated by the SOA can be data stored, received or transmitted, for example to the control unit during the implementation of the method according to the invention.
- the data relating to the phase of the signal amplified and modulated by the SOA can be data stored in a memory of a computer medium.
- the data relating to the phase of the signal amplified and modulated by the SOA can be determined and/or measured, preferably during the implementation of the method according to the invention.
- the calibration step can be implemented independently of the method and the method can be implemented without the step of determining the modulation of the pulsed signal or the variation of the pump signal.
- the determination of the modulation of the pulsed signal and/or of the variation of the pump signal, to be applied can comprise, or be or consist of, the calibration of the modulation and/or of the variation.
- Determining the modulation of the pulse signal and/or the variation of the pump signal may comprise the step of adjusting, adapting or setting, the modulation of the modulation of the applied pulse signal and/or the variation of the applied pumping.
- the determination of the modulation of the pulsed signal and/or of the variation of the pumping signal can include the steps consisting in:
- the pulse signal preferably the peak value, the rise and/or the fall of the at least one pulse of the pulse signal, and/or modulating the variation of the pumping signal, preferably the variation of the value of peak, rise and/or fall of the at least one pulse of the pump signal, and/or
- the determination of the modulation of the peak value may comprise the steps consisting in:
- a reference pulse signal preferably the peak value of which is constant, more preferably a square pulse signal, more preferably the peak value, the rise and/or the fall of at least one pulse of the pulse signal reference, and/or modulate the variation of the pump signal, preferably the variation of the peak, rise and/or fall value of the at least one pulse of the pump signal, and
- the method may include the step of amplifying, by means of a fiber optic amplifier, the master laser beam amplified and modulated by the SOA.
- the method may comprise the step of compensating or modulating or adapting or modifying, preferably by means of a control unit of the LIDAR or of the SOA, the amplification of the master laser beam operated by the SOA as a function of or by compared to the amplification of the amplified and modulated master laser beam operated by the optical fiber amplifier.
- the device according to the invention is suitable, preferably is arranged, more preferably is specially designed, to implement the method according to the invention.
- the method according to the invention can, preferably is specially designed, be implemented by the device according to the invention.
- FIG. 1 illustrates a schematic representation of the experimental setup, of the Mach Zhender type, used to determine the evolution of the phase and the amplitude of the master laser beam amplified and modulated by the SOA,
- figure 2 illustrates the evolution, averaged over 1000 pulses, of the intensity and phase of the signal amplified and modulated by the SOA obtained from a square pump signal
- FIGS. 3a and 3b illustrate the evolution, over an average of 1000 pulses, of the intensity, of the phase P and of the frequency f of the amplified and modulated signal 2 obtained from a square pumping signal and FIGS. 3c and 3d illustrate the power spectral density obtained (logarithmic and linear scale), by coherent detection from a square pump signal, as a function of the spectrum of frequencies integrated over the duration of the pulse,
- FIGS. 4a and 4b illustrate the evolution, over an average of 1000 pulses, of the intensity, of the phase P and of the frequency of the amplified and modulated signal 2 obtained from a pumping signal whose value of the peak of the pulses is modulated
- FIGS. 4c and 4d illustrate the power spectral density obtained, by coherent detection from a pumping signal whose peak value of the pulses is modulated, as a function of the spectrum of frequencies integrated on the pulse duration
- FIGS. 5a and 5b illustrate the evolution, over an average of 1000 pulses, of the intensity, of the phase P and of the frequency of the amplified and modulated signal 2 obtained from a pumping signal whose value of the peak of the pulses is modulated and
- FIGS. 5c and 5d illustrate the power spectral density obtained, by coherent detection from a pumping signal whose peak value of the pulses is modulated, as a function of the spectrum of frequencies integrated on the pulse duration
- FIG. 6 is a schematic representation of a pulsed LIDAR for coherent detection
- FIG. 7a represents the evolution of the intensity of the square pumping signal which is injected into the SOA 31a
- FIG. 7b represents the evolution, during of the pulse, of the power of the signal amplified and modulated 2 by the SOA 3 obtained from the square pumping signal of FIG. 7a
- FIG. 7c represents the evolution, during the pulse, of the frequency of the signal amplified and modulated 2 by the SOA 3 obtained from the square pump signal of figure 7a
- figure 7d illustrates the power spectral density obtained, by coherent detection from a square pump signal, as a function of the spectrum of frequencies integrated over the duration of the pulse
- FIG. 8 is a schematic representation of embodiments of the control unit comprising one or more switches arranged to control the pump signal
- FIG. 9a represents the evolution of the intensity of the pumping signal which is injected into the SOA 3
- FIG. 9b represents the evolution, during the pulse, of the power of the signal amplified and modulated 2 by the SOA 3 obtained from the pumping signal whose peak value of the pulses is modulated as shown in the figure
- FIG. 9c represents the evolution, during the pulse, of the frequency of the amplified signal and modulated 2 by the SOA 3 obtained from the pumping signal whose peak value of the pulses is modulated as illustrated in FIG. 9a
- FIG. 9d illustrates the power spectral density obtained, by coherent detection from the signal of pumping whose peak value of the pulses is modulated as illustrated in FIG. 9a, according to the spectrum of frequencies integrated over the duration of the pulse,
- FIG. 10a represents the evolution of the intensity of the pumping signal which is injected into the SOA 3
- FIG. 10b represents the evolution, during the pulse, of the power of the signal amplified and modulated 2 by the SOA 3 obtained from the pumping signal whose peak value of the pulses is modulated as illustrated in FIG. 10a
- FIG. 10c represents the evolution, during the pulse, of the frequency of the amplified signal and modulated 2 by the SOA 3 obtained from the pumping signal whose peak value of the pulses is modulated as illustrated in FIG. 10a
- FIG. 10d illustrates the power spectral density obtained, by coherent detection from the signal of pumping whose peak value of the pulses is modulated as illustrated in FIG. 10a, as a function of the spectrum of frequencies integrated over the duration of the pulse. Description of embodiments
- variants of the invention may in particular be considered comprising only a selection of characteristics described, isolated from the other characteristics described (even if this selection is isolated within a sentence including these other features), if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art.
- This selection includes at least one feature, preferably functional without structural details, or with only part of the structural details if only this part is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art .
- FIGURE 1 illustrates the experimental setup 1 used to characterize the properties of the amplified and modulated master laser beam 2 by the SOA 3 as a function of a pump signal 4.
- the setup 1 includes a 5 "Emcore DFB-CW-FC laser diode -PM” sold by the company “Ixblue” continuously emitting a master laser beam at a wavelength of 1545 nm, corresponding to a frequency of 194 THz, referred to as the fref reference frequency.
- the SOA 3 used is a “BOA1004P” semiconductor optical amplifier sold by the company “Thorlabs”.
- the master laser beam 6 emitted by the diode 5 is divided into two beams 61, 62 by a splitter 71 or “50/50” coupler sold by the company “AFR”.
- the beam 61 is used as a local oscillator 61 and is injected into a phase quadrature demodulator 8 “Kylia COH24” sold by the company “Kylia”.
- the beam 62 is attenuated by an attenuator 9, 91 or fiber optic attenuator sold by the company "AFR” so as not to saturate the SOA 3.
- a pulse generator 10 comprising an electric generator 110 “BFS-VRM-03” of the Picolas brand 2.5 Amps (A), 5 Volts (V) which generates an electric current in the form of square pulse signals as represented on the FIGURE 7a.
- the SOA 3 couples the modulation and amplification functions.
- the pump signal 4 according to the embodiment is generated by the pulse generator 10.
- the pulses of the pump signal 4 generated by the pulse generator 10 have a peak value which varies during the pulse.
- the control unit 15 according to the invention varies the pump signal by modulating the square pulse signals (represented in FIG. 7a) emitted by the electric generator 110.
- the master laser beam 6 is amplified and modulated, by the SOA 3, according to the signal pump 4 which is injected into the SOA 3.
- the amplified and modulated beam 2 is attenuated by an attenuator 9, 92 so as not to saturate the detector 11.
- the amplified, modulated and attenuated beam 21 is divided into two by a coupler additional 72. Part of the amplified, modulated and attenuated beam 21 is injected into the phase quadrature optical demodulator 8.
- a factor k links the intensity Ia to Im according to the following relationship:
- a balanced detector 23 “PDB480C-AC of the brand “Thorlabs” is coupled to the demodulator 8 to measure the bands of the amplified, modulated and attenuated signal 21 in phase and in quadrature with the signal from the local oscillator 61.
- P the evolution of the phase
- P the intensity la of the amplified and modulated signal 2 during the pulse.
- the intensity measurement made by the detector 11 and the phase measurements P made by the demodulator 8, as described with reference to FIGURE 1, are not necessary for the implementation of the method according to the invention.
- the method according to the invention has the advantage of not requiring such measurements, in particular for determining the direction of the wind speed.
- the purpose of the measurements described is to demonstrate the technical contributions and advantages of the invention with respect to the LIDARs of the state of the art. However, it is not excluded that the method includes such measures.
- the amplified and modulated signals 2 presented in FIGURES 2 to 4 were obtained by using a pump signal 4 square of 400 nanoseconds (ns) and an intensity of 0.6 A, injected into the SOA 3 to modulate and amplify the beam master laser 6.
- the peak value 14 of the pump signal 4 "classic" or "standard” square, as used in the state of the art, is constant over the entire duration of the pulse.
- Each pulse of the pump signal 4 comprises a rise 12 of the signal, a peak signal 14 and a fall 13 of the signal.
- FIGURE 2 illustrates the evolution of the intensity Ia in arbitrary units (u.a) and the phase P in radians (rad) of the amplified and modulated signal 2 averaged over 1000 pulses. It is in fact noted that the phase P follows the intensity Ia of the signal in the first tens of nanoseconds. Phase P subsequently deviates from the intensity la of the amplified and modulated signal 2.
- FIGURE 2b zooms in on the first eighty nanoseconds of the pulse of FIGURE 2a.
- the phase P of the pulse, in radians (rad) is plotted on the ordinate axis and the time in seconds (s) is plotted on the abscissa axis.
- FIG. 3a shows the evolution of the intensity 1a, of the phase P, of the amplified and modulated signal 2 averaged over 1000 pulses.
- the pump signal 4 injected into the SOA 3, to amplify and modulate the master laser beam 6, is a square signal.
- the evolution of the phase P follows the same trend as that of FIGURE 2.
- the intensity la of the amplified and modulated signal 2 is subject to non-negligible variations in the first half of the pulse .
- the phase P of the pulse, in radians is plotted on the ordinate axis and the time, in seconds, is plotted on the abscissa axis.
- the intensity la of the amplified and modulated signal 2 is in arbitrary units.
- FIG. 3b shows the instantaneous evolution of the intensity la and of the frequency f of the amplified and modulated signal 2 averaged over 1000 pulses.
- the frequency f of the amplified and modulated signal 2 was calculated from the phase data of FIGURE 3 according to the formula: formula 2.
- the frequency f of the pulse in Mega Hertz (MHz) is plotted on the y-axis and the time, in seconds, is plotted on the abscissa axis.
- the intensity la of the amplified and modulated signal 2 is in arbitrary units. Note a consequent variation in the frequency f of the amplified and modulated signal 2 during the rise 12 and the fall 13. In addition, the frequency f of the amplified and modulated signal 2 is unstable during the entire pulse.
- FIGS. 3c and 3d show the spectrum of frequencies integrated over the duration of the pulse obtained by coherent detection from the amplified and modulated pulse signal 2, obtained by varying the peak value 14 of the pumping signal linearly. 4, and of the local oscillator 61.
- the offset induced by the SOA corresponds to the offset between the reference frequency f ref of the master laser beam 6, that is to say of the local oscillator 61, and the frequency f of the amplified and modulated signal 2.
- an SOA-induced shift of 2.2 MHz is observed resulting from the variation in the phase of the amplified and modulated signal 2 during the pulse.
- This phase variation is frequent but not systematic. In addition, it is uncontrollable and depends on the drift in the phase of the amplified and modulated signal 2.
- This phase variation of the amplified and modulated signal 2 also causes a broadening of the observed frequency peak, the appearance of one or more lobes (s) at the base of this peak, or more generally a distortion of this peak (see FIGURE. 3 d)
- the solution provided by the invention is to maintain constant , or as constant as possible, the phase P of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- the modulation of the peak value 14 consists in varying the peak value 14 of the pumping signal 4 according to a monotonic function throughout the duration of the pulse.
- the amplified and modulated signals 2 presented in FIGURE 4 were obtained by using a pump signal 4 of 400 nanoseconds (ns) and an intensity of 0.6 A, injected into the SOA 3 to modulate and amplify the master laser beam 6, wherein the peak value 14 varies linearly increasing over the entire duration of the pulse.
- the function defining the peak value 14 of the pumping signal 4 is increasing and monotonous over the time interval of the pulse.
- FIGURE 4a is illustrated the evolution of the phase P as a function of time.
- the intensity Ia, in arbitrary units, of the pulsed signal amplified and modulated 2 by the SOA 3 measured by the demodulator 8 are also shown.
- FIGURE 4b represents the evolution of the frequency f of the amplified and modulated pulse signal 2, calculated from the phase data of FIGURE 5a according to formula 2, during the pulse.
- the frequency f of the pulse in Mega Hertz (MHz)
- MHz Mega Hertz
- FIGS. 4c and 4d show the spectrum of frequencies integrated over the duration of the pulse obtained by coherent detection from the amplified and modulated pulse signal 2, obtained by varying the peak value 14 of the pumping signal linearly. 4, and of the local oscillator 61.
- the use of a pumping signal whose peak value is a linear current ramp makes it possible to obtain a peak centered at the frequency 0 , that is to say without offset induced by the SOA, on the frequency of the master laser beam 6. In Besides, it also reduces the broadening of the measured peak and attenuates the lobes at its base
- the solution provided by the invention is to vary a phase P of a pulse of the signal amplified and modulated 2 by the SOA 3 according to a function which is increasing over at least one time interval of the pulse and which is decreasing over at least one interval pulse time.
- the phase P increases and decreases so as to form a triangular signal.
- the modulation of the peak value 14 consists in varying the peak value 14 of at least one pulse of the pumping signal 4 according to a function which is increasing over at least a time interval of l pulse and which is decreasing over at least one time interval of the pulse.
- the peak value 14 of the pump signal 4 is similar to a triangular signal 14.
- the amplified and modulated signals 2 presented in FIGURE 5 were obtained by using a pump signal 4 of 400 nanoseconds (ns) and with an intensity of 0.6 A, injected into the SOA 3 to modulate and amplify the master laser beam 6, in which the peak value 14 forms a triangular signal.
- the triangular 14 peak value of pump signal 4 includes a linear increase in intensity from 0.4 A down to 0.6 A over an 80 ns time interval and a linear decrease in intensity from 0.6 A down to 0.4 A over a time interval of 20 ns.
- the triangular pump signal 4 comprises four triangles during a pulse.
- FIGURE 5a is illustrated the evolution of the phase as a function of time.
- the intensity Ia, in arbitrary units, of the pulsed signal amplified and modulated 2 by the SOA 3 measured by the demodulator 8 is also represented.
- FIGURE 5b represents the evolution of the frequency f of the amplified and modulated pulse signal 2, calculated from the phase data of FIGURE 5a according to formula 2, during the pulse.
- the frequency f of the pulse in Mega Hertz (MHz), is plotted on the y-axis and the time, in seconds, is plotted on the abscissa axis.
- the modulation of the peak value 14 of the pulse of the pump signal 4 comprises a variation of the peak value 14.
- This variation of the peak value 14 is such that an average peak value 14 over a time interval of the pulse over which the function is increasing or decreasing is equal to each of the other average peak values of each of the other time intervals of the pulse over which the function is increasing or decreasing.
- the average peak value 14 over a considered interval of the pulse over which the function, of the peak value of at least one pulse of the pumping signal, is increasing or decreasing, is:
- phase P of the signal amplified and modulated 2 by the SOA 3 is modulated so as to form a triangular signal. Furthermore, the average value of the phase P over a considered time interval of the pulse, over which the phase P is increasing or decreasing, is
- the peak value 14 of the pumping signal 4 is successively increasing and decreasing during the same considered pulse.
- the phase P of the pulse of the signal amplified and modulated 2 by the SOA 3 as a function of the considered pulse of the pumping signal 4 has a phase value P which varies by modulo 2n several times during the pulse of the signal amplified and modulated 2 by the SOA 3.
- each variation of 2n in the phase during the pulse of the signal amplified and modulated 2 by the SOA 3 comprises an increase in the value of the phase at a moderate speed of the order of 1.10 8 rad/s and a sudden decrease qualified as a phase jump at the fastest possible speed, typically of the order of 1.10 10 rad/s.
- the peak value 14 of the at least one pulse of the pump signal 4 varies increasing over at least one time interval of the at least one pulse of the pump signal 4 and varies so decreasing over at least one time interval of the at least one pulse of the pumping signal 4.
- the variation of the peak value 14 of the pumping signal 4 over its increasing part or, as is the case according to the embodiment presented, its increasing part during the same pulse considered is greater, in their absolute value, than 1.10 8 Amps per second (A/s) and so more preferred at 1.10 9 A/s or else at 1.10 10 A/s.
- the phase P of the signal amplified and modulated 2 by the SOA 3 evolves in a similar way to the pump signal 4 unlike in FIG. 4a where the monotonous increase in the peak value of the pump signal 4 over the entire pulse duration implied a constant phase.
- the rapid variation (rate of variation typically greater than 1.10 8 A/s) of the peak value of the pumping signal 4 has the effect of obtaining a non-zero variation of the phase P of the amplified and modulated signal 2 by the SOA 3.
- a moderate variation (rate of variation typically less than 1.10 7 A/s) of the peak value of the pumping signal 4 has the effect of obtaining a zero variation of the phase P of the amplified and modulated signal 2 by the SOA 3, i.e. constant phase.
- FIGURES 5c and 5d the spectrum of frequencies integrated over the duration of the pulse obtained by coherent detection from the amplified and modulated pulse signal 2, obtained by means of a peak value 14 of the pump signal 4 in the form of a triangular signal, and of the local oscillator 61.
- the use of a peak value 14 of the triangular pump signal 4 makes it possible to obtain a frequency shift induced by the SOA of a value controlled, here 19.1 MHz.
- the frequency shift introduced by the SOA is a function of the gradient of the increase in the peak value 14 of the pump signal 4.
- the frequency shift introduced by the SOA such as 'illustrated in FIG.
- 5d is, or tends to become, proportional to the steering coefficient of the increasing parts of the triangular peak signal 14 when the variation of the peak value 14 of the pump signal 4 on the decreasing parts of the peak signal 14 triangular is greater than 1.10 8 Amps per second (A / s) and more preferably to 1.10 9 A / s or 1.10 10 A / s.
- the frequency shift introduced by the SOA is, or tends to become, proportional to the leading coefficient of the increasing dice portions of the triangular peak signal 14 as the variation in the peak value 14 of the pump signal 4 on the increasing parts of the triangular peak signal 14 is greater than 1.10 8 Amps per second (A/s) and more preferably 1.10 9 A/s or even 1.10 10 A/s.
- A/s Amps per second
- FIGURE 4d a reduction in the broadening of the peak and an attenuation of the lobes at the base of the peak.
- the pulsed LIDAR 1 comprises a master laser 5 capable of emitting a master laser beam 6, a pulse generator 10 capable of generating a pump signal 4 pulse, a SOA 3 arranged to amplify and modulate the master laser beam 6 according to the pump signal 4.
- the amplified and modulated master laser beam 2 forming a measurement laser beam 2.
- the Pulsed LIDAR 1 also comprises a control unit 15 arranged to modulate a peak value 14 of at least one pulse of the square pulse signal (represented in FIG. 7a) emitted by the electric generator 110.
- the Pulsed LIDAR 1 further comprises a circulator or a beam splitter 16, a telescope 17, an optical sensor 18 and optical fibers 19 connecting the components and arranged to route the signals from one element of the LIDAR 1 to the other.
- the measuring laser beam 2 when it reaches a target, for example a particle, is partly reflected and/or backscattered towards the LIDAR 1. This reflected and/or backscattered part is called the return laser beam 24, passes back through the telescope 17, enters the circulator 16 through the second input-output and leaves through a third input-output to be directed towards the optical sensor 18.
- the reference signs described in FIGURE 1 remain unchanged.
- FIGURE 7a there is illustrated the use of a 4 square pump signal as described in the state of the art.
- FIGURE 7b represents the evolution of the power of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- FIGURE 7c represents the evolution of the frequency f of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- a variation in the frequency of the amplified and modulated signal 2 around the reference frequency fre f of the local oscillator is observed.
- the frequency of the amplified and modulated signal 2 drifts from a frequency f2 higher than the reference frequency fre f to a frequency fi lower than the reference frequency fref.
- FIGURE 7d is shown the spectrum of frequencies integrated over the duration of the pulse obtained by coherent detection from the amplified and modulated pulse signal 2, obtained by means of a pump signal 4 square, and the local oscillator 61.
- FIGURE 7d illustrates the power spectral density, relative amplitude, ordinate versus frequency, MHz, abscissa. Illustrated are the ideal peak that should theoretically be obtained from a square wave signal and the actual peak that is actually obtained using a 4 square pump signal. We can observe the broadening of the peak and the appearance of a lobe at the base of the peak induced by the drift of the frequency of the amplified and modulated signal 2.
- FIGURE 8 are illustrated embodiments of the control unit 15 according to the invention.
- the control unit 15 comprises one or more switches 22 arranged to vary the pump signal 4 by switching, modulating and controlling the square pulse signal (shown in FIG. 7a) emitted by the electric generator 110.
- the pulse generator 10 further comprises a control unit 15, a power supply 101, an energy storage device 20, for example a capacitor 20, and a control circuit 22 of the switch(es) 22.
- the control unit 15 is arranged to modulate, as previously defined, the square pulse signal (shown in FIG. 7a) emitted by the electric generator 110 so as to generate a variation in the peak value 14 of the pulses of the pumping signal 4.
- the control unit 15 makes it possible to obtain pulses of the pumping signal 4 of several amperes, even tens of amperes, short, of a few tens of nanoseconds, and with fast rising 12 and falling 13 edges, typically lower at 10 ns.
- switch(es) 22 are NMOS.
- switch(es) 22 are PMOS.
- the control unit 15 comprises a switch 221, called primary switch 221, and a switch 222, called secondary switch 222.
- the secondary switch 222 is arranged to switch and modulate the electrical signal faster than the primary switch 221.
- the secondary switch 222 makes it possible to ensure very good optical extinction, typically greater than 70 dB, and to improve the fall time 12 of the SOA 3.
- the function of the secondary switch 222 is to dissipate the charges SOA 3 when SOA 3 is amplifying master laser beam 6.
- FIGURE 9 there is illustrated the use of the control unit 15 to modulate the peak value 14 of the pump signal 14 by linearly and monotonically increasing the peak value 14 of the square pulse signal ( shown in Figure 7a) emitted by the electric generator 110.
- FIGURE 9a illustrates a pulse of the pump signal 4 varying linearly increasing and monotonically during the pulse.
- FIGURE 9b represents the evolution of the frequency f of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- FIGURE 9c represents the evolution of the power of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- FIG. 9a illustrates a pulse of the pump signal 4 varying linearly increasing and monotonically during the pulse.
- FIGURE 9b represents the evolution of the frequency f of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- FIGURE 9c represents the evolution of the power of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- FIG. 9d shows the frequency spectra integrated over the duration of the pulse obtained by coherent detection from amplified and modulated pulse signals 2, obtained by different pump signals page 4, and from the local oscillator 61.
- the FIGURE 9d illustrates the power spectral density, in relative amplitude, in ordinate as a function of frequency, in MHz, in abscissa. It shows the ideal peak sought for the needs of the lidar, the peak without compensation which is obtained from a pump signal 4 square and the peak with compensation obtained from the pump signal 4 as described in the FIGURE 9a. It is observed that the peak without compensation obtained from the pump signal 4 square is broad and has lobes at its base. This is induced by the frequency drift of the amplified and modulated signal 2.
- Af is equal to the difference between the frequency of the signal amplified and modulated 2 by the SOA 3 and the frequency (fref) of the master laser beam (or local oscillator) 61 .
- control unit 15 to vary the peak value 14 of the pump signal 14 by modulation of the square pulse signal (shown in Figure 7a) emitted by the generator electrical 110:
- the control unit 15 is arranged to vary the peak value 14 of the pulses of the pumping signal 4 by modulation of the square pulse signal (represented in FIG. 7a) emitted by the electric generator 110 so that a peak value 14 averaged over a time interval of the pulse over which the function is increasing, or respectively decreasing, either lower or higher than an average peak value 14 over another time interval of the pulse over which the function is increasing, or respectively decreasing.
- the average peak value 14 over a considered interval of the pulse over which the function is increasing or decreasing is:
- the pulse generator 10 is arranged to generate a pump signal 4 triangular.
- the pump signal 4 comprises five triangles during a pulse.
- the peak value 14 of the end of rise 12 of a triangle considered is greater than the peak value 14 of the end of rise 12 of a triangle which chronologically precedes the triangle considered.
- the peak value 14 of the end of descent 13 of a triangle considered is lower than the peak value 14 of the end of descent 13 of a triangle which chronologically precedes the triangle considered.
- the pulse generator 10 is arranged to increase or decrease, during a pulse and in a non-linear and non-monotonic manner, the average peak value 14 of the pumping signal 4.
- FIGURE 10a illustrates a pulse of a non-monotonic increasing triangular pump signal.
- FIGURE 10b represents the evolution of the frequency of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- FIGURE 10c represents the evolution of the power of the signal amplified and modulated 2 by the SOA 3 during the pulse.
- FIG. 10d shows the frequency spectra integrated over the duration of the pulse obtained by coherent detection from amplified and modulated pulse signals 2, obtained by different pump signals 4, and from the local oscillator 61.
- lOd illustrates the power spectral density, in relative amplitude, in ordinates according to the frequency, in MHz, in abscissas.
- FIGURE 10a It shows the ideal peak sought for a lidar application, the peak without compensation actually obtained from a 4-square pump signal and the peak with compensation and frequency control obtained from the non-increasing triangular 4 pump signal.
- FIGURE 10a It is observed that the peak without compensation obtained from the pump signal 4 square is broad and has lobes at its base. This is induced by the drift in the frequency of the amplified and modulated signal 2.
- the peak with compensation and frequency control obtained from the non-monotonic increasing triangular pumping signal 4 has a frequency shift of the peak by a controlled value.
- the offset is a function of the gradient of the average increase in the peak value 14 of the pump signal 4.
- FIGURE 4d compared to the peak without compensation actually obtained from a square pom page 4 signal, one notices, as for FIGURE 4d, a reduction in peak broadening and attenuation of the lobes at the base of the peak.
- the peak value 14 of the at least one pulse of the pump signal 4 comprises an average peak value 14 over a time interval of the at least one pulse of the pump signal 4, preferably over a time interval of the at least one pulse of the pump signal over which the peak value 14 is increasing or decreasing, which is lower or higher than an average peak value 14 over another time interval of the at least one pulse of the signal pump 4, preferably over a time interval of the at least one pulse of the pump signal 4 over which the peak value 14 is increasing or decreasing, and/or
- a frequency of at least one pulse of the signal amplified and modulated 2 by the SOA 3 is shifted, adjusted or modulated according to a gradient of the peak value 14 of the at least one pulse of the pump signal 4 on the at least one time interval of the at least one signal pulse pumping 4 over which the peak value 14 is increasing and/or as a function of a gradient of the peak value 14 of the at least one pulse of the pumping signal 4 over the at least one time interval of the at least one pulse of the pump signal 4 on which the peak value 14 is decreasing,
- the method comprises determining the modulation of the peak value 14, to be applied, from data:
- phase of a pulse of the signal amplified and modulated 2 by the SOA 3 is modulated so that an average value of the phase P over a considered time interval of the pulse over which the phase is increasing, or respectively decreasing, is :
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Abstract
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CN202280055110.0A CN117795375A (zh) | 2021-07-01 | 2022-06-30 | 由经调制信号控制的带有半导体光学放大器的脉冲激光雷达 |
EP22744671.3A EP4363899A1 (fr) | 2021-07-01 | 2022-06-30 | Lidar impulsionnel à amplificateur optique à semi-conducteur piloté par un signal modulé |
CA3223737A CA3223737A1 (fr) | 2021-07-01 | 2022-06-30 | Lidar impulsionnel a amplificateur optique a semi-conducteur pilote par un signal module |
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FRFR2107164 | 2021-07-01 | ||
FR2107164A FR3124861B1 (fr) | 2021-07-01 | 2021-07-01 | LIDAR impulsionnel à amplificateur optique à semi-conducteur piloté par un signal modulé. |
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EP (1) | EP4363899A1 (fr) |
CN (1) | CN117795375A (fr) |
CA (1) | CA3223737A1 (fr) |
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WO (1) | WO2023275332A1 (fr) |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
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FR1461407A (fr) | 1965-06-09 | 1966-02-25 | Sobio Lab | Nouveaux pamoates d'amines et procédés de leur préparation |
EP3026455A1 (fr) * | 2014-11-25 | 2016-06-01 | Leosphere | Lidar pulsé à amplificateur optique à semi-conducteur |
-
2021
- 2021-07-01 FR FR2107164A patent/FR3124861B1/fr active Active
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2022
- 2022-06-30 CN CN202280055110.0A patent/CN117795375A/zh active Pending
- 2022-06-30 WO PCT/EP2022/068209 patent/WO2023275332A1/fr active Application Filing
- 2022-06-30 EP EP22744671.3A patent/EP4363899A1/fr active Pending
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Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1461407A (fr) | 1965-06-09 | 1966-02-25 | Sobio Lab | Nouveaux pamoates d'amines et procédés de leur préparation |
EP3026455A1 (fr) * | 2014-11-25 | 2016-06-01 | Leosphere | Lidar pulsé à amplificateur optique à semi-conducteur |
Non-Patent Citations (1)
Title |
---|
KOBTSEV SERGEY M ET AL: "Hybrid SOA/fibre topology for actively mode-locked laser with extended pulse-shaping capability", SPIE PROCEEDINGS; [PROCEEDINGS OF SPIE ISSN 0277-786X], SPIE, US, vol. 10896, 7 March 2019 (2019-03-07), pages 1089620 - 1089620, XP060120728, ISBN: 978-1-5106-3673-6, DOI: 10.1117/12.2509709 * |
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CN117795375A (zh) | 2024-03-29 |
CA3223737A1 (fr) | 2023-01-05 |
EP4363899A1 (fr) | 2024-05-08 |
FR3124861B1 (fr) | 2023-09-01 |
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