Pulsed LiDAR with Semiconductor Optical Amplifier Controlled by a Modulated Signal

Abstract

The present invention relates to a pulsed LiDAR comprising a master laser capable of emitting a master laser beam, a pulse generator configured to generate a pump signal comprising at least one pulse having a varying peak value during the at least one pulse of the pump signal, and a semiconductor optical amplifier (SOA) configured to amplify and modulate the master laser beam based on the pump signal, wherein the amplified and modulated laser beam forms a measurement laser beam.

Description

[Technical field]

[0001] LiDAR is used, among other things, to observe the atmosphere and determine atmospheric properties, which may be, among other things, wind speed, the concentration of particles in the atmosphere, the size and / or shape of the particles, and the temperature of the atmosphere.

[0002] The present invention relates in particular to the modulation and amplification of pulsed optical signals used by such LiDARs, and is particularly aimed at generating pulsed signals with high cadence, narrow spectral width and modulatable frequency.

[0003] The present invention relates to a pulsed LiDAR with an optical amplifier, more precisely to a pulsed LiDAR with a semiconductor optical amplifier, also called SOA, and to a method of amplification for such a LiDAR. [Background technology]

[0004] Known from the state of the art is French patent specification 1 461 407 relating to a LiDAR with a semiconductor optical amplifier, called SOA-LiDAR, which describes the use of an SOA configured to ensure the function of intensity modulation of a master laser beam and the function of amplification of the master laser beam.

[0005] A drawback of state-of-the-art SOA-LiDAR is the inability to determine the sign of the wind speed. Therefore, in order to determine the sign of the wind speed, it is necessary to incorporate an acousto-optic modulator (AOM) or a phase quadrature optical demodulator to be able to determine the sign of the wind speed. In practice, the AOM introduces a given frequency shift across the amplified signal relative to the signal from the local oscillator, i.e. the master laser. This frequency shift must be controlled, precise and constant. This frequency shift allows the sign of the wind speed during heterodyne detection to be determined.

[0006] Another drawback of state-of-the-art SOA-LiDAR is due to the nonlinearity of the transfer function of the SOA, which results in the signal amplified and modulated by the SOA being not square and symmetrical, which causes spectral spreading of the amplified and modulated signal and a decrease in the signal-to-noise ratio.

[0007] Another drawback of the state of the art SOA-LiDAR is that it leads to 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. The frequency drift can lead to deviations in the measured wind speed values. The broadening of the measured Doppler peak as well as secondary peaks reduces the accuracy and repeatability of the measurements. The object of the present invention is in particular to Determining the sign of wind speed using LiDAR without AOM, and / or To improve the signal-to-noise ratio and therefore the availability of LiDAR, and / or Improving the reliability of measurements of atmospheric properties performed by LiDAR; and / or The objective of the present invention is to provide a more accurate measurement of atmospheric properties.

[0008] To this end, a master laser capable of emitting a master laser beam; a pulse generator configured to generate a pump signal including at least one pulse whose peak value varies over the course of the at least one pulse of the pump signal and / or to keep constant or vary the phase of at least one pulse of the signal amplified and modulated by the SOA; A pulsed LiDAR is proposed that includes a semiconductor optical amplifier (SOA) configured to amplify and modulate a master laser beam as a function of a pump signal, where the amplified and modulated master laser beam forms a measurement laser beam.

[0009] A peak value of the at least one pulse of the pump signal may vary over all or a portion of the at least one pulse. A phase of the at least one pulse of the signal amplified and modulated by the SOA may be constant or may vary over all or a portion of the at least one pulse of the signal amplified and modulated by the SOA.

[0010] In this application, the term "signal" as used by itself can refer to a pump signal and / or a pulse signal and / or a signal amplified and modulated by an SOA and / or the phase of a signal amplified and modulated by an SOA.

[0011] In this application, the master laser beam or the measurement laser beam amplified and modulated by the SOA may be referred to as the signal amplified and modulated by the SOA. The signal amplified and modulated by the SOA is preferably a pulsed signal. Upon reading this application, one skilled in the art would directly deduce that a pulse may include a peak value as well as a leading edge and / or a trailing edge.

[0012] The pulse generator is A generator configured to generate a pulse signal; and a control unit configured to vary at least one pulse of the pump signal, preferably a peak value, a rise and / or a fall, respectively, of at least one pulse of the pump signal, by modulating the pulse signal, preferably a peak value, a rise and / or a fall, respectively, of at least one pulse of the pulse signal generated by the generator.

[0013] Preferably, the pump signal, more preferably at least one pulse of the pump signal, corresponds respectively to a pulsed signal modulated by the control unit, preferably to at least one pulse of a pulsed signal modulated by the control unit.

[0014] The control unit can be configured to vary a phase of at least one pulse of the signal amplified and modulated by the SOA by modulating the pulse signal generated by the generator.

[0015] The control unit is preferably configured to vary a peak value of one or more, or each, of the pulses of the pulsed signal generated by the generator. The control unit may be configured to modulate at least one pulse of the pulsed signal.

[0016] The control unit is preferably configured to modulate a peak value of at least one pulse of the pulsed signal. The control unit may be configured to modulate at least one pulse of the pulsed signal and not modulate at least one pulse of the pulsed signal, preferably to modulate a peak value of at least one pulse of the pulsed signal and not modulate a peak value of at least one pulse of the pulsed signal.

[0017] In this application, the terms “peak value” and / or “rise” and / or “fall” used alone may refer to the peak value and / or rise and / or fall of 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.

[0018] The pulse generator is preferably configured to vary the phase and / or frequency of the signal amplified and modulated by the SOA by modulating 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, and more preferably by modulating the variation of the peak value of the at least one pulse of the pump signal.

[0019] The control unit is preferably configured to vary the phase and / or frequency of the signal amplified and modulated by the SOA by modulating at least one pulse of the pulsed signal, preferably by modulating the rising and / or falling edge of at least one pulse of the pulsed signal, and further preferably by modulating the peak value of at least one pulse of the pulsed signal.

[0020] The control unit may be configured to vary a phase of at least one pulse of the signal amplified and modulated by the SOA, preferably by modulating the pulsed signal.

[0021] The control unit Keeping the phase of at least one pulse of the signal amplified and modulated by the SOA constant, or The phase of at least one pulse of the signal amplified and modulated by the SOA may be varied, preferably to increase over at least one period of the at least one pulse, and / or preferably to decrease over at least one period of the at least one pulse of the signal amplified and modulated by the SOA.

[0022] The control unit may be configured to vary the phase of at least one pulse of the signal amplified and modulated by the SOA such that an average value of the phase over a period of at least one pulse of the signal amplified and modulated by the SOA, preferably with an increasing or decreasing phase, respectively, is equal to an average value of the phase over another period of at least one pulse of the signal amplified and modulated by the SOA, preferably with an increasing or decreasing phase, respectively,.

[0023] The control unit may be configured to vary the phase of at least one pulse of the signal amplified and modulated by the SOA such that an average value of the phase over a period of a pulse of the signal amplified and modulated by the SOA, preferably over a period of a pulse of the signal amplified and modulated by the SOA in which the phase is increasing or decreasing, respectively, is smaller or larger than an average value of the phase over another period of a pulse of the signal amplified and modulated by the SOA, preferably over a period of a pulse in which the phase is increasing or decreasing, respectively.

[0024] The control unit may be configured to vary the phase of at least one pulse of the signal amplified and modulated by the SOA such that a value of the phase changes modulo 2π at least once over the course of the at least one pulse of the signal amplified and modulated by the SOA.

[0025] The control unit may preferably be configured to vary the phase of at least one pulse of the signal amplified and modulated by the SOA such that over the course of the at least one pulse of the signal amplified and modulated by the SOA the value of the phase changes several times, preferably periodically modulo 2π. The control unit may be configured to vary the phase of at least one pulse of the signal amplified and modulated by the SOA according to a pattern or triangular shape.

[0026] According to a first preferred embodiment of the invention, one or more, preferably each, pulse of 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 may include, and preferably is composed of, a rising edge of the signal, a peak signal and a falling edge of the signal. The rising edge of the signal is preferably performed from a minimum level to the peak signal, which may be a local minimum of the signal. The minimum level of the signal preferably corresponds to the 0 value of the signal. The falling edge of the signal is preferably performed from the peak signal to a minimum level of the signal at which the rising edge is caused or to a local minimum of the signal different from the minimum level at which the rising edge is caused.

[0027] According to a first aspect, the peak signal of a pulse can correspond to the portion of the signal of the pulse contained between the end of the rising edge of the pulse and the beginning of the falling edge of the pulse. As a non-limiting example, in the case of a rectangular pulse signal, the peak signal corresponds to a plateau, i.e. a constant maximum value of the signal contained between the end of the rising edge of the pulse and the beginning of the falling edge of the pulse.

[0028] According to the first aspect, the peak signal of a pulse may refer to the entire signal value included between the signal value at the end of the rising edge of the pulse and the signal value at the start of the falling edge of the pulse.

[0029] According to a second aspect of the invention, which is not compatible with the first aspect of the invention, one or more, preferably each, pulse of 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 may comprise a rising or falling edge and a peak signal. In other words, according to the invention, the pulse under consideration corresponds either to a pulse according to the first aspect or to a pulse according to the second aspect.

[0030] According to a second aspect of the invention, the pulse comprises: Peak signal, or A rising edge followed by a peak in the signal, or It may include, preferably includes only, more preferably consists of, and more preferably consists of, a peak signal and a trailing edge thereafter.

[0031] According to a second aspect of the invention, the pulse may comprise, preferably only comprises, more preferably consists of, a leading edge followed by a peak signal. The leading edge of the signal is preferably made from a minimum level, which may be a local minimum of the signal, to a maximum level, which may be a local maximum of the signal. The minimum level of the signal preferably corresponds to a zero value of the signal. The peak signal of the pulse may preferably correspond to a portion of the signal of the pulse comprised between the maximum level of the signal and the minimum level of the signal at which the leading edge is made, or to a local minimum of the signal different from the minimum level at which the leading edge is made.

[0032] According to a second aspect of the invention, the pulse may comprise, preferably only comprise, more preferably only consist of, a peak signal followed by a trailing edge. The peak signal of the pulse may correspond to a part of the signal of the pulse comprised between a minimum level of the signal, which may preferably be a local minimum, and a maximum level of the signal, which may be a local maximum. The minimum level of the signal preferably corresponds to a zero value of the signal. The trailing edge of the signal is preferably made from the maximum level of the signal to a minimum level of the signal which is the signal from which the peak signal extends, or to a local minimum value of the signal different from the minimum level from which the peak signal extends.

[0033] According to a second aspect of the invention, the pulse may comprise, preferably only comprises, more preferably consists of, more preferably only consists of a peak signal. In this case, the peak signal preferably corresponds to the signal of the pulse. In this case, the peak signal, preferably the signal of the pulse, is and / or preferably followed by or preceding, more preferably followed by, a portion of the signal of a pulse included between a minimum level of the signal, which may be a signal minimum and preferably the level from which the peak signal extends, and a maximum level of the signal, which may be a signal maximum. It may include a portion of the signal of the pulse that is included between a maximum level of the signal, which may be a maximum value of the signal, to a minimum level of the pump signal, which may preferably be a minimum value of the signal from which the peak signal extends, or to a minimum value of the pump signal that is different from the minimum level from which the peak signal extends.

[0034] According to the present invention, the phase of the pump signal and / or the pulse signal and / or the signal amplified and modulated by the SOA and / or the signal amplified and modulated by the SOA can be At least one pulse according to the first aspect of the invention, and / or It comprises at least one pulse according to the second aspect of the invention.

[0035] The remainder of the disclosure similarly relates to the first aspect and its alternative, i.e., the second aspect of the invention.

[0036] According to the invention, the signal and / or the peak value and / or the rise and / or fall may be defined by a mathematical function and / or a periodic function or may vary according to a mathematical function and / or a periodic function or may be modulated according to a mathematical function and / or a periodic function. "Signal" may refer to the entire value of the signal in question.

[0037] The term "peak signal" as used within the framework of this application can be, but is not only related to, the peak power. In particular, the term "peak signal" as used within the framework of this application can be, but is not only related to, the peak power of the measurement signal. The peak signal of a pulse may correspond to the entire peak value of the pulse under consideration. According to the invention, the signal may comprise successive pulses which are identical or different from each other. One or more, preferably each, pulse of the signal is preferably periodic. The pulse generator is preferably any signal generator.

[0038] The control unit is preferably configured to vary a peak value of each pulse of the pump signal by modulating each pulse of the pulsed signal.The control unit is preferably configured to vary a peak value of each pulse of the pump signal by modulating the peak value of each pulse of the pulsed signal.

[0039] The variation in peak value of at least one pulse of the pump signal is the variation of at least a portion, preferably the entirety, of the peak signal of at least one pulse of the pump signal, or This may mean a characteristic in which the peak signal of at least one pulse of the pump signal includes at least a portion that is not constant, and preferably the entirety of the peak signal of at least one pulse of the pump signal is not constant.

[0040] As a non-limiting example of pulse-related characteristics, all or part of the characteristics of the pump signal described in this application can be replaced by the phase of the pulse of the signal amplified and modulated by the SOA, which preferably has the same characteristics as the phase of the peak signal of at least one pulse of the pump signal according to the present invention.

[0041] A peak value of the at least one pulse of the pump signal may vary monotonically over at least one period of the at least one pulse of the pump signal.

[0042] The control unit may be configured to monotonically vary the peak value of at least one pulse of the pump signal over at least one period of the at least one pulse of the pump signal by modulating at least one pulse of the pulsed signal generated by the generator, preferably by modulating the peak value of the at least one pulse of the pulsed signal generated by the generator.

[0043] The control unit may be configured to linearly vary all or a portion of a peak value of at least one pulse of the pump signal by modulating at least one pulse of the pulsed signal generated by the generator.

[0044] The control unit may be configured to linearly vary a series of peak values, e.g. a series of peak value segments, of at least one pulse of the pump signal by modulating at least one pulse of the pulsed signal generated by the generator.

[0045] The control unit may be configured to generate a function of a peak value of at least one pulse of the pump signal by modulating at least one pulse of the pulsed signal generated by the generator. The period of a pulse may refer to a period contained within the duration of the pulse.

[0046] The control unit may preferably be configured to monotonically vary all or a portion of the peak signal of at least one pulse of the pump signal by modulating at least one pulse of the pulsed signal generated by the generator.

[0047] The control unit may be preferably configured to vary the peak signal during a given pulse of the pump signal by modulating at least one pulse of the pulsed signal generated by the generator independently of the peak signal during another period of the given pulse of the pump signal.

[0048] A peak value of the at least one pulse of the pump signal may vary monotonically over the entire duration of the at least one pulse of the pump signal. The control unit may be configured to modulate at least one pulse of the pulsed signal generated by the generator to monotonically vary a peak value of the at least one pulse of the pump signal over an entire duration of the at least one pulse of the pump signal. The total duration of a pulse may mean the entire pulse or the entire duration of the pulse.

[0049] A peak value of the at least one pulse of the pump signal can vary to increase over at least one period of the at least one pulse of the pump signal and / or can vary to decrease over at least one period of the at least one pulse of the pump signal.

[0050] The control unit may be configured to vary the peak value of at least one pulse of the pump signal by modulating at least one pulse of the pulsed signal generated by the generator, preferably by modulating a peak value of at least one pulse of the pulsed signal generated by the generator, and / or by modulating at least one pulse of the pulsed signal generated by the generator, preferably by modulating a peak value of at least one pulse of the pulsed signal generated by the generator, to increase over at least one period of at least one pulse of the pump signal and / or to decrease over at least one period of at least one pulse of the pump signal.

[0051] The control unit may be configured to generate at least one increase and at least one decrease in a peak value of the at least one pulse of the pump signal, or vice versa, by modulating the at least one pulse of the pulsed signal.

[0052] The peak value of the pump signal before the first of the at least one increment is preferably equal to the value of the pump signal at the end of the leading edge of the pulse, and the peak value of the pump signal after the last of the at least one increment is preferably equal to the value of the pump signal at the beginning of the trailing edge of the pulse.

[0053] The peak value of at least one pulse of the pump signal preferably varies alternately or continuously from increasing to decreasing or vice versa, in other words, the peak value of at least one pulse of the pump signal can vary to form an alternation or succession between periods of increasing peak value and periods of decreasing peak value, or vice versa. The peak value of at least one pulse of the pump signal preferably varies according to a trigonometric function.

[0054] The rise and / or fall rates of the signal; the rate of increase of the peak value of the signal, i.e., the speed at which the peak value of the signal increases or increases, and / or the rate of decrease of the peak value of the signal, i.e., the speed at which the peak value of the signal decreases or decreases; The ratio of It may be 2 or more, preferably 5, more preferably 10, even more preferably 100, and most preferably 1000. The rate of increase of the peak value of the signal may be different from the rate of decrease of the peak value of the signal.

[0055] The ratio of the rate of decrease of at least one of the signal peak values ​​to the rate of increase of at least one of the signal peak values ​​is preferably greater than or equal to 1, preferably 2, even more preferably 5, more preferably 10, even more preferably 100, and most preferably 1000. The rate of decrease of at least one of the peak values ​​of the signal may preferably be equal to the rate of fall of the signal.

[0056] The rise rate, fall rate, rate of increase and rate of decrease can be defined as the signal fluctuations per second. As a non-limiting example, the pump signal can be a voltage, intensity or luminous flux. Thus, the peak value of the pump signal can be expressed in volts (V), amperes (A), or watts (W), or watts / second (W / s), or any unit. As a non-limiting example, the rise rate, fall rate, rate of increase or rate of decrease can be defined in volts / second or amperes / second or watts / second.

[0057] As a non-limiting example, the rate of rise (or rise) and / or rate of fall (or fall) should preferably be exactly 1.10 in absolute value. 8 Amperes per second (A / s) or greater, preferably 1.10 9 It can be more than A / s.

[0058] As a non-limiting example, the rate of increase (or increase) and / or rate of decrease (or decrease) may be greater than or equal to 2.10 in absolute value. 8 A / s or less, preferably strictly less than 1.10 7 A / s, preferably 1.10 6 As a non-limiting example, the rate of increase (or increase) and / or rate of decrease (or decrease) may be greater than or equal to 1.10 in absolute value. 4 A / s greater than and / or 1.10 in absolute value 5 It can be greater than Amperes per second (A / s).

[0059] The variation of the peak value of the signal can be achieved with a rise rate over at least one period of at least one pulse and / or a fall rate over at least one period of at least one pulse and / or a rise rate over at least one period of at least one pulse and / or a fall rate over at least one period of at least one pulse.

[0060] Variations in the peak value of the pump signal in rise and / or fall rates preferably result in non-zero variations in the phase P of the signal amplified and modulated by the SOA. Variations in the peak value of the pump signal in the rate of increase and / or decrease preferably result in zero variation in the phase P of the signal amplified and modulated by the SOA, ie a constant phase.

[0061] The peak value of at least one pulse of the pump signal may include an average peak value over the period of at least one pulse of the pump signal, preferably over the period of at least one pulse of the pump signal having an increasing or decreasing peak value, which is equal to an average peak value over another period of at least one pulse of the pump signal, preferably over the period of a pulse of the pump signal having an increasing or decreasing peak value.

[0062] The control unit may be configured to vary the peak value of at least one pulse of the pump signal, preferably by modulating at least one pulse of the pulsed signal, and further preferably by modulating the peak value of at least one pulse of the pulsed signal generated by the generator, such that an average peak value over the period of the at least one pulse of the pump signal, preferably over the period of the at least one pulse of the pump signal having an increasing or decreasing peak value, is equal to an average peak value over another period of the at least one pulse of the pump signal, preferably over the period of the at least one pulse of the pump signal having an increasing or decreasing peak value, respectively.

[0063] The intervals of the at least one pulse during which the peak value of the at least one pulse of the pump signal is increasing preferably have one and the same average peak value. The intervals of the at least one pulse during which the peak value of the at least one pulse of the pump signal is reduced preferably have one and the same average peak value.

[0064] Preferably, the interval of the at least one pulse during which the peak value of the at least one pulse of the pump signal is increasing and the interval of the pulse during which the peak value of the at least one pulse of the pump signal is decreasing have the same average peak value, in other words, each of the intervals of the at least one pulse during which the function of the peak value of the at least one pulse of the pump signal is increasing or decreasing can have the same average peak value as each of the peak values ​​of the other intervals of the at least one pulse during which the function of the peak value of the at least one pulse of the pump signal is increasing or decreasing.

[0065] The average peak value over a period of time taking into account at least one pulse in which the function of the peak value of at least one pulse of the pump signal is increasing or decreasing is preferably a function of the peak value of at least one pulse of the pump signal is increasing or decreasing and is identical to an average peak value over the period of at least one pulse following in time the period under consideration; A function of the peak value of at least one pulse of the pump signal is increasing or decreasing and is identical to the average peak value over the period of at least one pulse preceding in time the period under consideration.

[0066] According to the present invention, as a non-limiting example, the average value over a period of a quantity of pulse phase or pulse intensity, or pulse peak value or pulse phase value or pulse peak value, can be defined as being equal to the overall arithmetic mean of the values ​​obtained by that quantity over the period of time.

[0067] The peak value of at least one pulse of the pump signal may include an average peak value over the period of at least one pulse of the pump signal, preferably over the period of at least one pulse of the pump signal having an increasing or decreasing peak value, which is smaller or larger than an average peak value over another period of at least one pulse of the pump signal, preferably over the period of at least one pulse of the pump signal having an increasing or decreasing peak value.

[0068] The control unit may be configured to vary the peak value of at least one pulse of the pump signal, preferably by modulating at least one pulse of the pulsed signal, and further preferably by modulating the peak value of at least one pulse of the pulsed signal generated by the generator, so that an average peak value over the period of at least one pulse of the pump signal, preferably over the period of at least one pulse of the pump signal having an increasing or decreasing peak value, is smaller or larger than an average peak value over another period of at least one pulse of the pump signal, preferably over the period of at least one pulse of the pump signal having an increasing or decreasing peak value.

[0069] The intervals of the at least one pulse during which the peak value of the at least one pulse of the pump signal is increasing preferably have different average peak values, i.e. greater or smaller average peak values, respectively. Preferably, the intervals between the at least one pulse during which the peak value of the at least one pulse of the pump signal is reduced each have a different average peak value.

[0070] The interval of at least one pulse during which the peak value of the at least one pulse of the pump signal is increasing preferably has an average peak value different from the average peak value of the interval of at least one pulse during which the peak value of the at least one pulse of the pump signal is decreasing.

[0071] The average peak value over a period taking into account at least one pulse in which the peak value of at least one pulse of the pump signal is increasing or respectively decreasing is preferably the peak value of at least one pulse of the pump signal is increasing or respectively decreasing and is greater than, or preferably smaller than, the average peak value over the period of at least one pulse following in time the period under consideration; The peak value of at least one pulse of the pump signal is increasing or respectively decreasing and is smaller or preferably larger than the average peak value over the period of at least one pulse preceding in time the period under consideration.

[0072] The average peak value over a period of time taking into account at least one pulse during which the peak value of at least one pulse of the pump signal is increasing or decreasing is preferably the peak value of at least one pulse of the pump signal is increasing or decreasing and is greater than, or preferably smaller than, the average peak value over the period of at least one pulse following over time the period under consideration; The peak value of at least one pulse of the pump signal is increasing or decreasing and is less than, or preferably greater than, the average peak value over the period of at least one pulse preceding in time the period under consideration.

[0073] The control unit may include at least one switch configured to control and / or modulate the pulse signal. At least one switch may be a transistor. The transistor may be a metal oxide semiconductor field effect transistor, denoted MOS. The transistor may be an n-type, i.e., nMOS transistor, or a p-type, i.e., pMOS transistor. The at least one switch may be configured to vary the pump signal by modulating and / or switching a pulsed signal emitted by the generator.

[0074] The LiDAR can include an optical fiber amplifier configured to amplify the master laser beam that is amplified and modulated by the SOA.

[0075] The LiDAR, or a control unit of the LiDAR or SOA, may be configured to vary the peak value of the master laser beam amplified and modulated by the SOA, preferably in a linear increasing or decreasing manner.

[0076] The LiDAR, or the control unit of the LiDAR or the SOA, may preferably be configured to vary, preferably in a linear increasing or decreasing manner, the signal, or the average signal, or the power or the average power, of the laser beam amplified by the optical fiber amplifier, i.e. the peak value of the master laser beam amplified and modulated by the SOA and then amplified by the optical fiber amplifier, is constant over at least one pulse.

[0077] According to the invention, a method for amplifying a pulsed LiDAR master laser beam is also proposed, the method comprising: generating a pump signal comprising at least one pulse, the peak value of which varies over the course of said at least one pulse of said pump signal, preferably by a pulse generator which varies over the course of said at least one pulse of the pump signal, preferably comprising at least one pulse whose peak value, rising edge and / or falling edge varies over the course of said at least one pulse of said pump signal, preferably by keeping constant or varying the phase of at least one pulse of the signal amplified and modulated by the SOA;

[0078] and amplifying and modulating a master laser beam by a semiconductor optical amplifier (SOA) of the pulsed LiDAR as a function of the generated pump signal, where the amplified and modulated master laser beam forms a measurement laser beam.

[0079] The method may comprise a step consisting of varying, preferably by the control unit, a peak value of at least one pulse of the pump signal by modulating at least one pulse of the pulse signal, preferably by modulating a peak value, a rising edge and / or a falling edge of at least one pulse of a pulse signal which may be generated by a generator.

[0080] The method may preferably comprise a step consisting of varying the phase and / or frequency of the signal amplified and modulated by the SOA, preferably by modulating, preferably by a pulse generator, at least one pulse of the pump signal, preferably by modulating the peak value, the rising edge and / or the falling edge of the at least one pulse of the pump signal, further preferably by modulating the variation of the peak value of the at least one pulse of the pump signal.

[0081] The method may preferably comprise a step consisting of varying, preferably by a control unit, the phase and / or frequency of the signal amplified and modulated by the SOA by modulating at least one pulse of the pulsed signal, preferably by modulating the rising and / or falling edge of at least one pulse of the pulsed signal, further preferably by modulating the peak value of at least one pulse of the pulsed signal.

[0082] The method may comprise a step consisting of varying, preferably by the control unit, the phase of at least one pulse of the signal amplified and modulated by the SOA, preferably by modulating the pulse signal.

[0083] This method is keeping constant the phase of at least one pulse of the signal amplified and modulated by the SOA, preferably by modulating a pulsed signal, preferably by a control unit; or The method may include varying, preferably by modulating a pulsed signal, preferably by a control unit, the phase of at least one pulse of the signal amplified and modulated by the SOA in an increasing manner, preferably over at least one period of the at least one pulse, and / or in a decreasing manner, preferably over at least one period of the at least one pulse of the signal amplified and modulated by the SOA.

[0084] The method can include steps consisting of shifting a frequency of at least one pulse of a signal amplified and modulated by the SOA in proportion to a slope of change of the phase of the at least one pulse of the signal amplified and modulated by the SOA over at least one period of the at least one pulse during which the phase is increasing or decreasing.

[0085] The method may comprise a step of varying the phase of at least one pulse of the signal amplified and modulated by the SOA such that an average value of the phase over a period of at least one pulse of the signal amplified and modulated by the SOA, preferably with an increasing or decreasing phase, respectively, is equal to an average value of the phase over another period of at least one pulse of the signal amplified and modulated by the SOA, preferably with an increasing or decreasing phase, respectively,.

[0086] The method may comprise a step of varying the phase of at least one pulse of the signal amplified and modulated by the SOA such that an average value of the phase over a period of the pulse of the signal amplified and modulated by the SOA, preferably over a period of the pulse of the signal amplified and modulated by the SOA where the phase is increasing or decreasing, respectively, is smaller or larger than an average value of the phase over another period of the pulse of the signal amplified and modulated by the SOA, preferably over a period of the pulse where the phase is increasing or decreasing, respectively.

[0087] The method may comprise a step of varying the phase of at least one pulse of the signal amplified and modulated by the SOA, for at least one pulse under consideration, such that the value of the phase changes by 2π modulo over at least one period of the at least one pulse taking into account the signal amplified and modulated by the SOA, i.e. such that the value of the phase changes by 2π modulo over the course of at least one pulse at least once taking into account the signal amplified and modulated by the SOA.

[0088] The method preferably comprises a step consisting of changing the phase of at least one pulse of the signal amplified and modulated by the SOA for at least one pulse under consideration such that the value of the phase changes by 2π modulo over several periods of the at least one pulse taking into account the signal amplified and modulated by the SOA, i.e. such that the value of the phase changes by 2π modulo several times over the course of the at least one pulse of the signal amplified and modulated by the SOA.

[0089] The method comprises: determining the phase of at least one pulse of a signal amplified and modulated by an SOA such that the average value of the phase P over a period considering at least one pulse in which the phase is increasing or, respectively, decreasing, is: is identical to the average peak value over the period of at least one pulse that follows in time the period under consideration; The step of varying the peak value may include varying the peak value so as to be identical to an average peak value over the period of at least one pulse preceding in time the period under consideration.

[0090] The method comprises: determining the phase of at least one pulse of a signal amplified and modulated by an SOA such that the average value of the phase P over a period considering at least one pulse in which the phase is increasing or, respectively, decreasing, is: the phase is increasing or decreasing, respectively, and is smaller or larger than the average value of the phase P over the duration of at least one pulse that follows in time the period under consideration, The phase may be increasing or decreasing, respectively, and may include a step of varying the phase P to be greater or smaller than an average value over the period of at least one pulse preceding in time the period under consideration.

[0091] The peak value of the pump signal is preferably modulated by a control unit, preferably by modulating a pulsed signal, so that over the course of a pulse of the signal amplified and modulated by the SOA, the phase of the signal amplified and modulated by the SOA is Being or remaining constant, or The change may be such that it is increasing for at least one period of the pulse and decreasing for at least one period of the pulse.

[0092] The peak value of the pump signal can change over the course of at least one pulse of the signal amplified and modulated by the SOA such that an average value of the phase over the period of at least one pulse of the signal amplified and modulated by the SOA, preferably over the period of at least one pulse of the signal amplified and modulated by the SOA with an increasing or decreasing phase, respectively, is equal to an average value of the phase over another period of at least one pulse of the signal amplified and modulated by the SOA, preferably over the period of at least one pulse of the signal amplified and modulated by the SOA with an increasing or decreasing phase, respectively.

[0093] The peak value of the pump signal can vary over the course of a pulse of the signal amplified and modulated by the SOA such that an average value of the phase over the period of at least one pulse of the signal amplified and modulated by the SOA, preferably over the period of at least one pulse of the signal amplified and modulated by the SOA in which the phase is increasing or decreasing, respectively, is smaller or larger than an average value of the phase over another period of at least one pulse of the signal amplified and modulated by the SOA, preferably over the period of at least one pulse of the signal amplified and modulated by the SOA in which the phase is increasing or decreasing, respectively.

[0094] The peak value of at least one pulse of the pump signal is may vary monotonically over at least one period of at least one pulse of the pump signal; and / or It may be increasing over at least one period of at least one pulse of the pump signal and / or decreasing over at least one period of at least one pulse of the pump signal.

[0095] At least one period of at least one pulse of the pump signal whose peak value changes monotonically and / or at least one period of at least one pulse of the pump signal whose peak value is increasing and / or at least one period of at least one pulse of the pump signal whose peak value is decreasing may be all or a portion of the total duration of the at least one pulse of the pump signal. The variation in peak value of at least one pulse of the pump signal may comprise, be or consist of a triangular signal. The peak value of the at least one pulse of the pump signal may vary monotonically over the entire duration of the at least one pulse of the pump signal.

[0096] The frequency of at least one pulse of the signal amplified and modulated by the SOA can be shifted, adjusted, or modulated as a function of the slope of the peak value of at least one pulse of the pump signal over at least one period of the at least one pulse of the pump signal whose peak value is increasing and / or as a function of the slope of the peak value of at least one pulse of the pump signal over at least one period of the at least one pulse of the pump signal whose peak value is decreasing.

[0097] The frequency of at least one pulse of the signal amplified and modulated by the SOA is preferably: and / or by varying the peak value, preferably the rising edge and / or the falling edge of at least one pulse of the pump signal; Preferably by the control unit, at least one pulse of a pulse signal, which may be generated by the generator, is shifted, further preferably by modulating the peak value, the rising edge and / or the falling edge of at least one pulse of the pulse signal.

[0098] The "slope of the peak value of at least one pulse of the pump signal" may be the leading coefficient of the peak value of at least one pulse of the pump signal, where the function is increasing or decreasing. The slope of the peak value of the pump signal is preferably the same over each period of the pulse whether the peak value is increasing or decreasing.

[0099] The peak value of at least one pulse of the pump signal preferably increases over at least one period of the at least one pulse of the pump signal and decreases over at least one period of the at least one pulse of the pump signal such that the 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 the peak value of the at least one pulse of the pump signal.

[0100] Preferably, the peak value of at least one pulse of the pump signal increases over at least one period of at least one pulse of the pump signal and decreases over at least one period of at least one pulse of the pump signal such that the 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, and preferably proportional to, the rate of variation of the peak value of the at least one pulse of the pump signal.

[0101] Preferably, a peak value of the at least one pulse of the pump signal increases over at least one period of the at least one pulse of the pump signal and decreases over at least one period of the at least one pulse of the pump signal; The variation of the peak signal over at least one period during which the peak signal is increasing or decreasing, respectively, is greater than 1.10 in absolute value 8 Greater than Amperes per Second (A / s), preferably 1.10 9 A / s greater than or equal to 1.10 10 A / s is larger than The variation in the peak signal over at least one period during which the peak signal is decreasing or increasing, respectively, is greater than 1.10 in absolute value 8 Less than amperes per second (A / s), preferably 1.10 7 A / s or less, preferably 1.10 in absolute value 4 Greater than Amperes per Second (A / s), preferably 1.10 5 Amperes per second (A / s) greater than and / or preferably 1.10 6 A / s or less, preferably 1.10 7 A / s or less, and even more preferably 1.10 8 the variation of the peak signal over at least one period during which the peak signal is decreasing or increasing, respectively, at a rate called the rate of variation of the peak value, which is less than A / s; In this way, the frequency of at least one pulse of the signal amplified and modulated by the SOA is shifted, adjusted or modulated as a function of the rate of variation of the peak value of at least one pulse of the pump signal, or preferably is shifted, adjusted or modulated or tends to be shifted, adjusted or modulated proportionally to the rate of variation of the peak value of at least one pulse of the pump signal.

[0102] The peak value of at least one pulse of the pump signal may include an average peak value over at least one period of the at least one pulse of the pump signal, preferably over at least one period during which the peak value is increasing or over at least one period during which the peak value is decreasing, which is equal to an average peak value over at least one other period of the at least one pulse of the pump signal, preferably over at least one period during which the peak value is increasing or over at least one period during which the peak value is decreasing.

[0103] The peak value of at least one pulse of the pump signal can preferably be varied, preferably by the control unit, by modulating at least one pulse of the pulse signal, further preferably by modulating the peak value, to the rise and / or fall of at least one pulse of the pulse signal, which may be generated by the generator, such that an average peak value over at least one period of at least one pulse of the pump signal, preferably over at least one period during which the peak value is increasing or over at least one period during which the peak value is decreasing, is equal to an average peak value over at least one other period of at least one pulse of the pump signal, preferably over at least one period during which the peak value is increasing or over at least one period during which the peak value is decreasing.

[0104] The peak value of at least one pulse of the pump signal may include an average peak value over at least one period of the at least one pulse of the pump signal, preferably over at least one period during which the peak value is increasing or over at least one period during which the peak value is decreasing, and the average peak value is smaller or larger than the average peak value over at least one other period of the at least one pulse of the pump signal, preferably over at least one period during which the peak value is increasing or over at least one period during which the peak value is decreasing.

[0105] The peak value of at least one pulse of the pump signal can be varied, preferably by modulating at least one pulse of the pulsed signal, more preferably the peak value, the rising edge and / or the falling edge of at least one pulse of the pulsed signal, preferably by a control unit, as can be generated by a generator, such that an average peak value over at least one period of at least one pulse of the pump signal, preferably over at least one period during which the peak value is increasing or over at least one period during which the peak value is decreasing, is smaller or larger than an average peak value over at least one other period of at least one pulse of the pump signal, preferably over at least one period during which the peak value is increasing or over at least one period during which the peak value is decreasing.

[0106] The method can include measuring data related to the phase of a signal amplified and modulated by an SOA. Measurement of the phase data of the signal amplified and modulated by the SOA can be performed by a phase quadrature detector, a coherent detector or a phase quadrature optical demodulator.

[0107] The method comprises: It is related to the phase of the signal amplified and modulated by the SOA, The method may include determining a modulation of at least one pulse of the pulsed signal and / or a variation of at least one pulse of the pump signal based on data of the peak value of at least one pulse of the pump signal as a function of the amplification and modulation of the master laser beam.

[0108] This method can be carried out without, i.e. in some cases without, a step of calibrating the peak value, i.e. a step of determining the modulation of at least one pulse of the pulse signal and / or the variation of at least one pulse of the pump signal.

[0109] The method may not include a step of measuring or determining data on the phase of the signal amplified and modulated by the SOA. These data may be collected before and / or independently of the method according to the invention. The data on the phase of the signal amplified and modulated by the SOA may be data stored, received or transmitted, for example, to a control unit, during the implementation of the method according to the invention. For example, the data on the phase of the signal amplified and modulated by the SOA may be data stored in a storage device of a computer medium.

[0110] Data relating to the phase of the signal amplified and modulated by the SOA can preferably be determined and / or measured during the implementation of the method according to the invention. In other words, the calibrating step may be performed independently of the method, and the method may be performed without the step of determining the modulation of the pulse signal or the variation of the pump signal.

[0111] "Determining a modulation of at least one pulse of a pulsed signal and / or a variation of at least one pulse of a pump signal" may mean determining a modulation applied to a pulsed signal and / or determining a variation applied to a pump signal.

[0112] Determining the modulation of the applied pulse signal and / or the variation of the pump signal may include, be or consist of calibrating the modulation and / or the variation.

[0113] Determining the modulation of the pulse signal and / or the variation of the pump signal may comprise a step consisting of adjusting, adapting or adjusting the modulation of the applied pulse signal and / or the variation of the applied pump signal.

[0114] According to a first variant, the modulation of the pulse signal and / or the determination of the variation of the pump signal is carried out by: modulating the pulse signal, preferably the peak value, the rise and / or the fall of at least one pulse of the pulse signal, and / or modulating the variation of the pump signal, preferably the variation of the peak value, the rise and / or the fall of at least one pulse of the pump signal, and / or amplifying and modulating a master laser beam by an SOA as a function of a pump signal; and adjusting, adapting or regulating the modulation of the applied pulse signal and / or the modulation of the variation of the applied pump signal.

[0115] According to a second variant, the determination of the modulation of the peak values ​​is - modulating a reference pulse signal, preferably a square pulse signal, with a preferably constant peak value, further preferably a peak value, rising edge and / or falling edge of at least one pulse of the reference pulse signal and / or modulating the variation of the pump signal, preferably the variation of the peak value, rising edge and / or falling edge of at least one pulse of the pump signal; determining a modulation of at least one pulse of the applied pulsed signal and / or a variation of at least one pulse of the applied pump signal.

[0116] The method can include the step of amplifying, by an optical fiber amplifier, a master laser beam that has been amplified and modulated by the SOA.

[0117] The method may include a step of compensating or modulating or adapting or correcting, preferably by a control unit of the LiDAR or SOA, the amplification of a master laser beam operated by the SOA as a function of or in relation to the amplification of the amplified and modulated master laser beam operated by the optical fiber amplifier.

[0118] The device according to the invention is suitable, preferably arranged and more preferably specially designed for carrying out the method according to the invention.

[0119] The method according to the invention can preferably be specially designed to be carried out by the device according to the invention. [Brief description of the drawings]

[0120] Other advantages and features of the invention will become apparent from the accompanying drawings, in which: FIG. [Figure 1] Schematic diagram of the Mach-Zehnder type experimental setup used to determine the phase and amplitude evolution of a master laser beam amplified and modulated by an SOA. [Diagram 2] FIG. 13 shows the evolution of the intensity and phase of the signal amplified and modulated by the SOA obtained based on a square pump signal, averaged over 1000 pulses. [Diagram 3] Figures 3a and 3b show the evolution over an average of 1000 pulses of the intensity, phase P and frequency f of the amplified and modulated signal 2 obtained based on a square pump signal, and Figures 3c and 3d show the power spectral density (logarithmic and linear scale) obtained by coherent detection based on a square pump signal as a function of the spectrum of frequency integrated over the duration of the pulse. [Figure 4] Figures 4a and 4b show the evolution of the intensity, phase P and frequency of the amplified and modulated signal 2 obtained based on a pump signal whose pulse peak value is modulated over an average of 1000 pulses, while Figures 4c and 4d show the power spectral density obtained by coherent detection based on a pump signal whose pulse peak value is modulated as a function of the spectrum of frequency integrated over the pulse duration. [Diagram 5]Figures 5a and 5b show the evolution of the intensity, phase P and frequency of the amplified and modulated signal 2 obtained based on a pump signal whose pulse peak value is modulated over an average of 1000 pulses, and Figures 5c and 5d show the power spectral density obtained by coherent detection based on a pump signal whose pulse peak value is modulated as a function of the spectrum of frequency integrated over the pulse duration. [Figure 6] FIG. 1 is a schematic diagram of a pulsed LiDAR for coherent detection. [Figure 7] Figure 7a is a diagram showing the evolution of the intensity of a square pump signal injected into SOA3, Figure 7b is a diagram showing the evolution over the course of a pulse of the power of signal 2 amplified and modulated by SOA3 obtained based on the square pump signal of Figure 7a, Figure 7c is a diagram showing the evolution over the course of a pulse of the frequency of signal 2 amplified and modulated by SOA3 obtained based on the square pump signal of Figure 7a, and Figure 7d is a diagram showing the power spectral density obtained by coherent detection based on the square pump signal as a function of the spectrum of frequency integrated over the duration of the pulse. [Figure 8] 1 is a schematic diagram of an embodiment of a control unit including one or more switches configured to control a pump signal. [Figure 9] Figure 9a is a diagram showing the evolution of the intensity of the pump signal injected into SOA3, Figure 9b is a diagram showing the evolution over the course of the pulse of the power of signal 2 amplified and modulated by SOA3 obtained based on a pump signal whose pulse peak value is modulated as shown in Figure 9a, Figure 9c is a diagram showing the evolution over the course of the pulse of the frequency of signal 2 amplified and modulated by SOA3 obtained based on a pump signal whose pulse peak value is modulated as shown in Figure 9a, and Figure 9d is a diagram showing the power spectral density obtained by coherent detection based on a pump signal whose pulse peak value is modulated as shown in Figure 9a as a function of the spectrum of frequency integrated over the pulse duration. [Figure 10]Figure 10a is a diagram showing the evolution of the intensity of the pump signal injected into SOA3, Figure 10b is a diagram showing the evolution over the course of the pulse of the power of signal 2 amplified and modulated by SOA3 obtained based on a pump signal whose pulse peak value is modulated as shown in Figure 10a, Figure 10c is a diagram showing the evolution over the course of the pulse of the frequency of signal 2 amplified and modulated by SOA3 obtained based on a pump signal whose pulse peak value is modulated as shown in Figure 10a, and Figure 10d is a diagram showing the power spectral density obtained by coherent detection based on a pump signal whose pulse peak value is modulated as shown in Figure 10a as a function of the spectrum of frequency integrated over the pulse duration. Description of the embodiments

[0121] Since the embodiments described below are in no way limiting, a variation of the invention can be considered to include only a selection of the described characteristics, in particular in isolation from the other described characteristics, if this selection of characteristics confers a technical advantage or is sufficient to distinguish the invention with respect to the prior art (even if this selection is isolated within a phrase including these other characteristics), this selection includes at least one, preferably functional, feature without structural details or including only a part of the structural details, if only a part of the structural details confers a technical advantage or is sufficient to distinguish the invention with respect to the state of the prior art.

[0122] Figure 1 shows the experimental setup 1 used to characterize the properties of a master laser beam 2 amplified and modulated by an SOA 3 as a function of the pump signal 4. The setup 1 is driven by a reference frequency f ref The laser diode “Emcore DFB-CW-FC-PM” sold by the company “Ixblue” continuously emits a master laser beam with a wavelength of 1545 nm, which corresponds to a frequency of 194 THz, called the master laser diode 5 .

[0123] The SOA 3 used is a semiconductor optical amplifier "BOA1004P" sold by the company "Thorlabs". The master laser beam 6 emitted by the diode 5 is split into two beams 61, 62 by a "50 / 50" splitter 71 or 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 sold by the company "AFR" or an optical fiber attenuator in order not to saturate the SOA 3.

[0124] The pulse generator 10 comprises a generator 110 "BFS-VRM-03", trademark Picolas, 2.5 Amperes (A), 5 Volts (V), which generates a current in the form of a square pulse signal as shown in FIG. 7a. The SOA 3 combines the functions of modulation and amplification with each other. The pump signal 4 in this 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 that varies over the course of the pulse. The control unit 15 according to the invention varies the pump signal by modulating the square pulse signal (shown in FIG. 7a) emitted by the generator 110. The master laser beam 6 is amplified and modulated by the SOA 3 as a function of the pump signal 4 injected into the SOA 3. The amplified and modulated beam 2 is attenuated by the attenuator 9, 92 so as not to saturate the detector 11. The amplified, modulated and attenuated beam 21 is split in two by an additional coupler 72. A portion of the amplified, modulated and attenuated beam 21 is injected into a phase quadrature optical demodulator 8 .

[0125] I a The intensity of the other part of the amplified, modulated and attenuated beam 21, denoted by I, is measured by a detector 11, DET01CFC, sold by the company Thorlabs. m The intensity of the amplified and modulated beam 2, denoted by a 21. The coefficient k is proportional to the intensity I according to the following relationship:a I m Associate with. I a =kI m , Equation 1

[0126] A balanced detector 23, “PDB480C-AC”, trademark “Thorlabs”, is coupled to the demodulator 8 and measures the bandwidth of the amplified, modulated and attenuated signal 21 in phase and quadrature with the signal of the local oscillator 61. Thus, the evolution of the phase, denoted P, and the intensity I of the amplified and modulated signal 2 during the pulse are a It is possible to track.

[0127] As explained with reference to FIG. 1, the intensity measurements performed by the detector 11 and the phase measurements P performed by the demodulator 8 are not necessary to carry out the method according to the invention. The method according to the invention has the advantage that such measurements are not necessary, in particular to determine the direction of the wind speed. The measurements described have the purpose of demonstrating the technical benefits and advantages of the invention over state-of-the-art LiDAR. However, it is not excluded that the method includes such measures.

[0128] The amplified and modulated signal 2 shown in Figures 2-4 was obtained using a 400 nanosecond (ns) square pump signal 4 and an intensity of 0.6 A injected into the SOA 3 to modulate and amplify the master laser beam 6. The peak value 14 of the "conventional" or "standard" square pump signal 4 used in state of the art is constant over the entire duration of the pulse. Each pulse of the pump signal 4 includes a signal rise 12, a signal peak 14, and a signal fall 13.

[0129] Figure 2 shows the intensity I in arbitrary units (au) of the amplified and modulated signal 2 averaged over 1000 pulses. a and the evolution of the phase P in radians (rad). In fact, the phase P is proportional to the signal intensity I a Note that the phase P follows the intensity I of the amplified and modulated signal 2. aFigure 2b zooms in on the first 80 nanoseconds of the pulse in Figure 2a. The phase P of the pulse in radians (rad) is plotted on the y-axis and time in seconds (s) is plotted on the x-axis. In addition, strength I a The value of the phase P when is 0 has no direction. This observation remains valid throughout the explanation.

[0130] Intensity I of the amplified and modulated signal 2 averaged over 1000 pulses a The evolution of the phase P is shown in Fig. 3a. The pump signal 4, which is injected into the SOA 3 and amplifies and modulates the master laser beam 6, is a square signal. The evolution of the phase P follows the same trend as the evolution in Fig. 2. Moreover, now the intensity I a Note that does not undergo slight variations in the first half of the pulse. The phase of the pulse P (in radians) is plotted on the y-axis and time (in seconds) on the x-axis. The intensity I of the amplified and modulated signal 2 a is an arbitrary unit.

[0131] Intensity I of the amplified and modulated signal 2 averaged over 1000 pulses a The instantaneous evolution of the phase and frequency f is shown in Fig. 3b. The frequency f of the amplified and modulated signal 2 was calculated based on the phase data of Fig. 3 according to the following formula:

[0132] JPEG2024527366000002.jpg10170

[0133] The frequency f of the pulse in megahertz (MHz) is plotted on the y-axis and time in seconds on the x-axis. The intensity I of the amplified and modulated signal 2 a is an arbitrary unit.

[0134] Note the resulting variation in frequency f of the amplified and modulated signal 2 during the leading edge 12 and trailing edge 13. Also, the frequency f of the amplified and modulated signal 2 is unstable across the pulse.

[0135] The spectrum of the frequency integrated over the duration of the pulse obtained by coherent detection on the basis of the amplified and modulated pulse signal 2 obtained by linearly varying the peak value 14 of the pump signal 4 and the local oscillator 61 is represented in Fig. 3c and 3d. The power spectral density is shown, in terms of relative amplitude, on the y-axis as a logarithmic scale in Fig. 3c and on a linear scale in Fig. 3d, and on the x-axis as a function of the frequency in MHz. The shift induced by the SOA corresponds to the shift of the master laser beam 6, i.e. the reference frequency f of the local oscillator 61. ref and the frequency f of the amplified and modulated signal 2. With reference to Figures 4c and 4d, a shift induced by the 2.2 MHz SOA is observed, resulting from a variation in the phase of the amplified and modulated signal 2 during the pulse. This phase variation is frequent, but not systematic. Moreover, it is uncontrollable and depends on the drift of 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 at the base of this peak, or more generally a deformation of this peak (see Figure 3d).

[0136] To overcome the different problems mentioned above, in particular to mitigate the frequency shift of the peak induced by the drift of the phase of the amplified and modulated signal 2 during the pulse, the solution provided by the present invention is to keep the phase P of the signal 2 amplified and modulated by the SOA 3 constant or as constant as possible during the pulse. To do this, it is possible, for example, to vary the peak value 14 of the pulse of the pump signal 4 using a pulse generator 10 according to the present invention and a pulsed LiDAR 1, a specific embodiment of which is shown in FIG. 8 and described below.

[0137] According to a particular embodiment, the modulation of the peak value 14 consists of varying the peak value 14 of the pump signal 4 according to a monotonic function over the duration of the pulse. The amplified and modulated signal 2 shown in FIG. 4 is obtained 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, with the peak value 14 varying linearly in an increasing manner over the duration of the pulse. In this case, the function defining the peak value 14 of the pump signal 4 is increasing and monotonic over the duration of the pulse.

[0138] The evolution of the phase P as a function of time is shown in Fig. 4a. The intensity I in arbitrary units of the pulse signal 2 amplified and modulated by the SOA 3 measured by the demodulator 8 a is also shown.

[0139] It is observed that by injecting a linear current ramp into the SOA 3 that increases as, for example, the peak value 14 of the pump signal 4, one can obtain an almost constant amplified and modulated phase P of the pulse signal 2. The phase P has a variation of less than 0.3 radians over the duration of the pulse, in contrast to the variation of 6 radians over the duration of the pulse for a square pump signal as shown in Figure 3a.

[0140] Figure 4b represents the evolution of the frequency f of the amplified and modulated pulse signal 2 over the course of the pulse, calculated based on the phase data of Figure 5a according to Equation 2. The frequency f of the pulse (in megahertz (MHz)) is plotted on the y-axis and time (in seconds) on the x-axis.

[0141] The spectrum of frequencies integrated over the duration of the pulses obtained by coherent detection on the basis of the amplified and modulated pulse signal 2 and the local oscillator 61, obtained by linearly varying the peak value 14 of the pump signal 4, is represented in Fig. 4c and Fig. 4d. The power spectral density is shown, in terms of relative amplitude, as a logarithmic scale on the y-axis in Fig. 4c and as a linear scale on the x-axis as a function of frequency in MHz in Fig. 4d. With reference to Fig. 4c and Fig. 4d, the use of a pump signal whose peak value is a linear current ramp, in comparison with the square pump signal 4, makes it possible to obtain a peak centered on frequency 0, i.e., without the shift induced by the SOA, over the frequencies of the master laser beam 6. Moreover, this also makes it possible to reduce the broadening of the measured peaks and to damp the lobes at their base.

[0142] To overcome the different problems mentioned above, and in particular to be able to determine the sign of the wind speed without having to use additional devices such as AOMs or phase quadrature demodulators, the solution provided by the invention is to vary the phase P of the pulses of the signal 2 amplified and modulated by the SOA 3 according to a function that increases over at least one period of the pulse and decreases over at least one period of the pulse. According to an embodiment, the phase P increases or decreases so as to form a triangular signal. To do this, it is possible, for example, to modulate the peak value 14 of the pulses of the pump signal 4 by the pulse generator 10 of the pulsed LiDAR 1.

[0143] According to a particular embodiment, the modulation of the peak value 14 consists of varying the peak value 14 of at least one pulse of the pump signal 4 according to a function that increases over at least one period of the pulse and decreases over at least one period of the pulse.

[0144] In fact, the peak value 14 of the pump signal 4 resembles a triangular signal 14. The amplified and modulated signal 2 shown in FIG. 5 is obtained 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, the peak value 14 forming a triangular signal. The triangular peak value 14 of the pump signal 4 includes a linear increase in intensity from 0.4 A to 0.6 A over a period of 80 ns and a linear decrease in intensity from 0.6 A to 0.4 A over a period of 20 ns. In fact, the triangular pump signal 4 includes four triangles over the course of the pulse. Moreover, the peak value 14 at the end of the rising edge 12 of the triangle under consideration is equal to the peak value 14 at the end of the rising edge 12 of the triangle preceding the triangle under consideration in time. Moreover, the peak value 14 at the end of the falling edge 13 of the triangle under consideration is equal to the peak value 14 at the end of the falling edge 13 of the triangle preceding the triangle under consideration in time.

[0145] The evolution of the phase as a function of time is shown in Fig. 5a. The intensity I in arbitrary units of the pulse signal 2 amplified and modulated by the SOA 3 measured by the demodulator 8 a Figure 5b represents the evolution of the frequency f of the amplified and modulated pulse signal 2 over the course of the pulse, calculated based on the phase data of Figure 5a according to Equation 2. The frequency f of the pulse (in megahertz (MHz)) is plotted on the y-axis and time (in seconds) on the x-axis.

[0146] The modulation of the peak values ​​14 of the pulses of the pump signal 4 comprises a variation of the peak values ​​14. This variation of the peak values ​​14 is such that the average peak value 14 over the period of the pulses in which the function is increasing or decreasing is equal to each of the other average peak values ​​14 of each of the other periods of the pulses in which the function is increasing or decreasing. The average peak value 14 over the interval considering the pulses in which the function of the peak value of at least one pulse of the pump signal is increasing or decreasing is a function of the peak value of at least one pulse of the pump signal is increasing or decreasing and is identical to an average peak value 14 over the period of the pulse, which continues over time during the period under consideration; A function of the peak value of at least one pulse of the pump signal is increasing or decreasing and is identical to an average peak value 14 over the period of the pulse preceding in time the period under consideration.

[0147] The phase P of the signal 2 amplified and modulated by the SOA 3 is modulated to be a triangular signal. Furthermore, the average value of the phase P over a period considering the pulses in which the phase P is increasing or decreasing is the phase P is increasing or decreasing and is greater than the average value of the phase P over the period following the period under consideration in time; The phase P is increasing or decreasing and is less than the average value of the phase P over the period preceding in time the period under consideration.

[0148] In particular, the peak value 14 of the pump signal 4 increases and decreases continuously over the course of one and the same pulse under consideration. This has the effect that the phase P of the pulse of the signal 2 amplified and modulated by the SOA 3 as a function of the pulse under consideration of the pump signal 4 has a phase value P that varies by several times modulo 2π over the course of the pulse of the signal 2 amplified and modulated by the SOA 3. Each 2π variation of the phase over the course of the pulse of the signal 2 amplified and modulated by the SOA 3 is preferably 1.10 8 The increase in phase value at moderate speeds of about rad / s and as fast as possible, typically 1.10 10 and a sudden decrease, called a phase jump, at a speed of the order of rad / s. According to an embodiment, the peak value 14 of at least one pulse of the pump signal 4 varies in an increasing manner over at least one period of at least one pulse of the pump signal 4 and varies in a decreasing manner over at least one period of at least one pulse of the pump signal 4. In this case, preferably, by way of non-limiting example, the variation of the peak value 14 of the pump signal 4 over the increasing portion, or, as is the case according to the presented embodiment, over the course of one and the same pulse under consideration, is greater than or equal to 1.10 in absolute value. 8 Greater than Amperes per Second (A / s), preferably 1.10 9A / s greater than or equal to 1.10 10 Greater than A / s.

[0149] In FIG. 5a, the phase P of the signal 2 amplified and modulated by the SOA 3 evolves in the same way as the pump signal 4, in contrast to FIG. 4a, where the monotonic increase in the peak value of the pump signal 4 over the entire duration of the pulse implied a constant phase. Thus, the rapid fluctuations in the peak value of the pump signal 4 (typically 1.10 8 A rate of change exceeding 1.10 A / s has the effect of obtaining a non-zero variation in the phase P of the signal 2 amplified and modulated by the SOA 3. A gradual change in the peak value of the pump signal 4 (typically 1.10 7 A rate of change of less than A / s has the effect of obtaining zero change in the phase P of the signal 2 amplified and modulated by the SOA 3, i.e. a constant phase.

[0150] The spectrum of the frequency integrated over the duration of the pulse obtained by coherent detection on the basis of the peak value 14 of the pump signal 4 in the form of a triangular signal and the amplified and modulated pulse signal 2 obtained by the local oscillator 61 is represented in Fig. 5c and Fig. 5d. The power spectral density is shown in terms of relative amplitude as a logarithmic scale on the y-axis and as a linear scale on the x-axis as a function of the frequency in MHz. With reference to Fig. 5c and Fig. 5d, the use of the peak value 14 of the triangular pump signal 4 in comparison with the square pump signal 4 makes it possible to obtain a frequency shift induced by the SOA, here of a control value of 19.1 MHz. In fact, the frequency shift introduced by the SOA is a function of the slope of the increase of the peak value 14 of the pump signal 4. With reference to Fig. 5a and Fig. 5b, as shown in Fig. 5d, the frequency shift introduced by the SOA is a function of the slope of the increase of the peak value 14 of the pump signal 4. With reference to Fig. 5a and Fig. 5b, the frequency shift introduced by the SOA is a function of the slope of the increase of the peak value 14 of the pump signal 4 over the decreasing part of the triangular peak signal 14, here of 1.10. 8 Greater than Amperes per Second (A / s), preferably 1.10 9 A / s greater than or equal to 1.10 10A / s, the frequency shift introduced by the SOA is proportional or tends to be proportional to the advance factor of the increasing portion of the triangle peak signal 14. Alternatively (not shown), the frequency shift introduced by the SOA may be proportional to the advance factor of the increasing portion of the triangle peak signal 14 by a factor of 1.10. 8 Greater than Amperes per Second (A / s), preferably 1.10 9 A / s or 1.10 10 For values ​​greater than A / s, it is proportional, or tends to be proportional, to the leading factor of the decreasing portion of the triangular peak signal 14. Furthermore, compared to Figure 3d, a broadening of the peak and a reduced attenuation of the lobe at the base of the peak are noted, similar to Figure 4d.

[0151] According to the presented embodiment, with reference to FIG. 6, the pulsed LiDAR 1 according to the invention comprises a master laser 5 capable of emitting a master laser beam 6, a pulse generator 10 capable of generating a pulsed pump signal 4, and an SOA 3 configured to amplify and modulate the master laser beam 6 as a function of the pump signal 4. The amplified and modulated master laser beam 2 forms a measurement laser beam 2. The pulsed LiDAR 1 also comprises a control unit 15 configured to modulate a peak value 14 of at least one pulse of a square pulse signal (represented in FIG. 7a) emitted by a generator 110. According to the embodiment, the pulsed LiDAR 1 further comprises a beam circulator or splitter 16, a telescope 17, an optical sensor 18 and an optical fiber 19 arranged to connect the components and transmit a signal from one element of the LiDAR 1 to the other. Upon reaching a target, e.g. a particle, the measurement laser beam 2 is partially reflected and / or backscattered towards the LiDAR 1. This reflected and / or backscattered portion, called return laser beam 24, returns through telescope 17, enters circulator 16 through the second input / output and exits through the third input / output to be directed to optical sensor 18. The reference numbers described in Figure 1 remain unchanged.

[0152] Referring to Fig. 7a, the use of a square pump signal 4 as described in the prior art is shown. Fig. 7b shows the evolution of the power of a signal 2 amplified and modulated by a SOA 3 during a pulse. Fig. 7c shows the evolution of the frequency f of a signal 2 amplified and modulated by a SOA 3 during a pulse. The reference frequency f of the local oscillator ref The variation in frequency of the amplified and modulated signal 2 around the reference frequency f is observed. ref From frequency f2, which is greater than the reference frequency f ref 7d. The spectrum of the frequency integrated over the duration of the pulse obtained by coherent detection based on the square pump signal 4 and the amplified and modulated pulse signal 2 obtained by the local oscillator 61 is represented in Fig. 7d. Fig. 7d shows the power spectral density in terms of the relative amplitude on the y-axis as a function of the frequency (MHz) on the x-axis. Here, the ideal peak that should be theoretically obtained based on a square signal and the real peak obtained in practice with the square pump signal 4 are shown. It is possible to observe the broadening of the peak and the appearance of a lobe at the base of the peak, caused by the drift of the frequency of the amplified and modulated signal 2.

[0153] An embodiment of the control unit 15 according to the invention is shown in Fig. 8. The control unit 15 comprises one or more switches 22 configured to vary the pump signal 4 by switching, modulating and controlling the square pulse signal (shown in Fig. 7a) emitted by the generator 110. The pulse generator 10 further comprises the control unit 15, a power supply 101, an energy storage device 20, e.g. a capacitor 20, and a control circuit 22 for the switch 22. The control unit 15 is configured to modulate the square pulse signal (shown in Fig. 7a) emitted by the generator 110 so as to generate variations in the peak values ​​14 of the pulses of the pump signal 4, as defined above.

[0154] The control unit 15 makes it possible to obtain pulses of the pump signal 4 of several amperes, or even tens of amperes, of a short duration of a few tens of nanoseconds, with rapid rising 12 and falling 13 edges, typically shorter than 10 ns. 8a and 8b, the switch 22 is an nMOS, and in FIG. 8c and 8d, the switch 22 is a pMOS.

[0155] 8b and 8d, the control unit 15 includes a switch 221, referred to as the primary switch 221, and a switch 222, referred to as the secondary switch 222. The secondary switch 222 is configured to switch and modulate the electrical signal more quickly than the primary switch 221. The secondary switch 222 ensures a very good optical extinction, typically above 70 dB, and allows to improve the fall time 12 of the SOA 3. The secondary switch 222 has the function of dissipating the load of the SOA 3 more quickly when the SOA 3 is amplifying the master laser beam 6.

[0156] Referring to Figure 9, there is shown the use of a control unit 15 to modulate the peak value 14 of the pump signal 4 by linearly and monotonically increasing the peak value 14 of the square pulse signal (represented in Figure 7a) emitted by the generator 110.

[0157] FIG. 9a shows a pulse of the pump signal 4 which varies linearly in an increasing monotonic manner over the course of the pulse. FIG. 9b represents the evolution of the frequency f of the signal 2 amplified and modulated by the SOA 3 during the pulse. FIG. 9c represents the evolution of the power of the signal 2 amplified and modulated by the SOA 3 during the pulse. The spectrum of the amplified and modulated pulse signal 2 obtained by different pump signals 4 and the frequency integrated over the duration of the pulse obtained by coherent detection from the local oscillator 61 is represented in FIG. 9d. FIG. 9d shows the power spectral density in terms of the relative amplitude on the y-axis as a function of the frequency (MHz) on the x-axis. As described in FIG. 9a, the ideal peak required for the requirements of the LiDAR, the uncompensated peak obtained based on the square pump signal 4 and the compensated peak obtained based on the pump signal 4 are shown there. It is observed that the uncompensated peak obtained based on the square pump signal 4 is broad and has a lobe at its base. This is caused by the drift of the frequency of the amplified and modulated signal 2. The compensated peak obtained based on the pump signal 4 as described in FIG. 9a is centered on the reference frequency of the master laser beam 6 at Δf=0, where Δf is the ratio between the frequency of the signal 2 amplified and modulated by the SOA 3 and the frequency of the master laser beam (or local oscillator) 61 (f ref ) in the uncompensated peak. Furthermore, a broadening of the peak and a reduction in the attenuation of the lobes at the base of the peak are noted, as in Figure 4d, compared to the uncompensated peak.

[0158] With reference to FIG. 10, the use of a control unit 15 to vary the peak value 14 of the pump signal 4 by modulating the square pulse signal (represented in FIG. 7a) emitted by the generator 110 is by successively increasing or decreasing the peak value 14 of the pump signal 4, and 7a) is shown by increasing the peak value 14 of the pump signal 4 non-linearly and non-monotonically over the duration of the pulse. More precisely, the control unit 15 is configured to vary the peak value 14 of the pulse of the pump signal 4 by modulating the square pulse signal (shown in FIG. 7a) emitted by the generator 110, so that the average peak value 14 over the period of a pulse in which the function is increasing or respectively decreasing is smaller or larger than the average peak value 14 over another period of a pulse in which the function is increasing or respectively decreasing. Even more precisely, the average peak value 14 over the period considering the pulse in which the function is increasing or decreasing is the function is increasing or decreasing and is less than the average peak value 14 over the interval of successive pulses over the period under consideration; - the function is increasing or decreasing and is greater than the average peak value 14 over the interval of the pulse preceding in time the period under consideration.

[0159] In practice, the pulse generator 10 is configured to generate a triangular pump signal 4. The pump signal 4 comprises five triangles over the course of the pulse. Moreover, the peak value 14 at the end of the leading edge 12 of the triangle under consideration is greater than the peak value 14 at the end of the leading edge 12 of the triangle preceding the triangle under consideration in time. Moreover, the peak value 14 at the end of the trailing edge 13 of the triangle under consideration is less than the peak value 14 at the end of the trailing edge 13 of the triangle preceding the triangle under consideration in time. In other words, the pulse generator 10 is configured to non-linearly and non-monotonically increase or decrease the average peak value 14 of the pump signal 4 over the course of the pulse.

[0160] FIG. 10a shows a pulse of a non-monotonically increasing triangular pump signal 4. FIG. 10b represents the frequency evolution of the signal 2 amplified and modulated by the SOA 3 during the pulse. FIG. 10c represents the power evolution of the signal 2 amplified and modulated by the SOA 3 during the pulse. The spectrum of the frequency integrated over the duration of the pulse obtained by coherent detection based on the amplified and modulated pulse signal 2 obtained by different pump signals 4 and the local oscillator 61 is represented in FIG. 10d. FIG. 10d shows the power spectral density in terms of the relative amplitude on the y-axis as a function of the frequency (MHz) on the x-axis. Shown therein are the ideal peaks required for LiDAR applications, the uncompensated peaks actually obtained based on the square pump signal 4, and the peaks with compensation and frequency control obtained based on the non-monotonically increasing triangular pump signal 4 shown in FIG. 10a. It is observed that the uncompensated peak obtained based on the square pump signal 4 is broad and has a lobe at its base. This is caused by the drift of the frequency of the amplified and modulated signal 2. The compensated and frequency-controlled peak obtained based on a triangular pump signal 4 has a frequency shift of the peak at a controlled value. The shift is a function of the slope of the average increase of the peak value 14 of the pump signal 4. Furthermore, in comparison with the uncompensated peak actually obtained based on a square pump signal 4, a broadening of the peak and a reduced attenuation of the lobe at the base of the peak are noted with respect to FIG. 4d.

[0161] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without going beyond the scope of the invention. Therefore, in a possible variant of the above embodiment, the peak value 14 of at least one pulse of the pump signal 4 comprises an average peak value 14 over the period of at least one pulse of the pump signal 4, preferably over the period of at least one pulse of the pump signal in which the peak value 14 is increasing or decreasing, which is smaller or larger than an average peak value 14 over another period of at least one pulse of the pump signal 4, preferably over the period of at least one pulse of the pump signal 4 in which the peak value 14 is increasing or decreasing; and / or The frequency of at least one pulse of signal 2 amplified and modulated by SOA 3 is shifted, adjusted or modulated as a function of the slope of peak value 14 of at least one pulse of pump signal 4 over at least one period of at least one pulse of pump signal 4 in which peak value 14 is increasing and / or as a function of the slope of peak value 14 of at least one pulse of pump signal 4 over at least one period of at least one pulse of pump signal 4 in which peak value 14 is decreasing.

[0162] The peak value 14 of at least one pulse of the pump signal 4 is varies monotonically over at least one period of at least one pulse of the pump signal 4, and / or is increasing over at least one period of at least one pulse of the pump signal 4 and / or is decreasing over at least one period of at least one pulse of the pump signal 4, and / or The method comprises: The phase of signal 2 amplified and modulated by SOA 3, and determining a modulation of the peak value 14 to be applied based on data of the peak value 14 of at least one pulse of the pump signal 4, as a function of which the master laser beam 2 is amplified and modulated; and / or The phase of the pulses of signal 2 amplified and modulated by SOA 3 is such that the average value of phase P over the period considering the pulses whose phase is increasing or decreasing, respectively, is is identical to the average peak value over the duration of the pulses following in time the period under consideration, is identical to the average peak value over the period of the pulse that precedes in time the period of interest; Further, various features, forms, variations and embodiments of the invention can be combined together in various combinations, unless they are compatible or mutually exclusive.

Claims

1. A pulsed LiDAR (1), a master laser (5) capable of emitting a master laser beam (6); a pulse generator (10) configured to generate a pump signal (4) including at least one pulse whose peak value (14) varies over the course of the at least one pulse of the pump signal; a semiconductor optical amplifier (SOA) (3) configured to amplify and modulate the master laser beam as a function of the pump signal, the amplified and modulated master laser beam (2) forming a measurement laser beam; A pulsed LiDAR (1), comprising:

2. The pulse generator (10) A generator (110) configured to generate a pulse signal; a control unit (15) configured to vary the peak value (14) of the at least one pulse of the pump signal (4) by modulating at least one pulse of the pulsed signal generated by the generator; The LiDAR (1) of claim 1, comprising:

3. The LiDAR (1) of claim 1 or 2, wherein the peak value (14) of the at least one pulse of the pump signal (4) varies monotonically over at least one period of the at least one pulse of the pump signal.

4. The LiDAR (1) of any one of claims 1 to 3, wherein the peak value (14) of the at least one pulse of the pump signal (4) varies monotonically over the duration of the at least one pulse of the pump signal.

5. The LiDAR (1) of any one of claims 1 to 4, wherein the peak value (14) of the at least one pulse of the pump signal (4) varies to increase over at least one period of the at least one pulse of the pump signal and / or varies to decrease over at least one period of the at least one pulse of the pump signal.

6. The LiDAR (1) of any one of claims 1 to 5, wherein the peak value (14) of the at least one pulse of the pump signal (4) comprises an average peak value over a period of the at least one pulse of the pump signal that is equal to an average peak value over another period of the at least one pulse of the pump signal.

7. The LiDAR (1) of any one of claims 1 to 5, wherein the peak value (14) of the at least one pulse of the pump signal (4) comprises an average peak value over a period of the at least one pulse of the pump signal that is less than or greater than an average peak value over another period of the at least one pulse of the pump signal.

8. The LiDAR (1) described in any one of claims 1 to 7, wherein the control unit (15) includes at least one switch (22, 221, 222) configured to control and / or modulate the pulse signal.

9. The LiDAR (1) according to any one of claims 1 to 8, comprising an optical fiber amplifier configured to amplify the amplified and modulated master laser beam (2).

10. 1. A method for amplifying a pulsed LiDAR master laser beam, comprising: generating a pump signal including at least one pulse whose peak value varies over the course of the at least one pulse of the pump signal; amplifying and modulating the master laser beam by a semiconductor optical amplifier (SOA) of the pulsed LiDAR as a function of the generated pump signal, the amplified and modulated master laser beam forming a measurement laser beam; A method comprising:

11. The method of claim 10 comprising varying the peak value of the at least one pulse of the pump signal by modulating at least one pulse of a pulsed signal.

12. The peak value of the at least one pulse of the pump signal is varies monotonically over at least one period of the at least one pulse of the pump signal; and / or increasing over at least one period of the at least one pulse of the pump signal and / or decreasing over at least one period of the at least one pulse of the pump signal.

12. The method according to claim 10 or 11.

13. 13. The method of claim 12, wherein a frequency of at least one pulse of the signal amplified and modulated by the SOA is shifted as a function of a slope of the peak value of the at least one pulse of the pump signal over the at least one period of the at least one pulse of the pump signal where the peak value is increasing and / or as a function of a slope of the peak value of the at least one pulse of the pump signal over the at least one period of the at least one pulse of the pump signal where the peak value is decreasing.

14. 14. The method of claim 10, wherein the peak value of the at least one pulse of the pump signal comprises an average peak value over at least one period of the at least one pulse of the pump signal that is equal to an average peak value over at least one other period of the at least one pulse of the pump signal.

15. 15. The method of claim 10, wherein the peak value of the at least one pulse of the pump signal comprises an average peak value over at least one period of the at least one pulse of the pump signal that is smaller or larger than an average peak value over at least one other period of the at least one pulse of the pump signal.

16. A method according to any one of claims 10 to 15, comprising measuring data relating to the phase of the signal amplified and modulated by the SOA.

17. determining the modulation of the at least one pulse of the pulsed signal and / or the variation of the peak signal of the at least one pulse of the pump signal based on data, the data comprising: related to the phase of the signal amplified and modulated by the SOA, the master laser beam is amplified and modulated as a function of the peak value of the at least one pulse of the pump signal; 17. The method of claim 16.

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