WO2005099051A1 - Dispositif de decalage de frequence dans un chemin optique a source laser continue - Google Patents
Dispositif de decalage de frequence dans un chemin optique a source laser continue Download PDFInfo
- Publication number
- WO2005099051A1 WO2005099051A1 PCT/EP2005/051104 EP2005051104W WO2005099051A1 WO 2005099051 A1 WO2005099051 A1 WO 2005099051A1 EP 2005051104 W EP2005051104 W EP 2005051104W WO 2005099051 A1 WO2005099051 A1 WO 2005099051A1
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- WO
- WIPO (PCT)
- Prior art keywords
- optical
- modules
- frequency
- optical path
- evolution
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/06209—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in single-section lasers
- H01S5/0622—Controlling the frequency of the radiation
Definitions
- the present invention relates to a frequency shift device in a continuous emission laser source optical path.
- a frequency variation Doppler effect
- This frequency variation is generally determined by mixing the received signal with a signal generated by a local oscillator and affected by a permanent frequency offset which is produced by a modulator of the electro-optical or acousto-optical type.
- Document CA 2 476 805 discloses a fiber optic sensor in which a light signal is modulated as a function of physical phenomena acting on the length of an optical path.
- the measuring device of this interferometric sensor receives pulse modulation signals shifted in phase on each of the two channels, and mixes the modulated optical signals in order to obtain an interference signal indicative of the distance to be measured.
- This interferometric device does not have a constant and permanent frequency shift function.
- the subject of the present invention is a frequency shift device in an optical path with a continuous emission laser source, a device which is as inexpensive as possible, compact, which is not a source of parasitic radiation, and which can be integrated. in an architecture comprising optical fibers.
- the device according to the invention is characterized in that it comprises at least two frequency shift modules placed in parallel and each containing an optical propagation medium, the optical path length of which is modified as a function of the desired frequency offset, each of these modules being controlled separately, this device comprising a switch connected to the outputs of these modules and controlled so as to choose , at each instant, the module ensuring the desired frequency offset, the switch providing at its output a continuous optical beam, the frequency of which is adjusted by contiguous sections.
- the evolution of the length of the optical path of the optical propagation medium is linear, this evolution taking place by virtue of a triangular modulation law, the slopes of the ascending segments or descendants of the triangular modulation law remain identical over time for the duration of the application of the modulation signal.
- the slopes of the ascending or descending segments vary over time to obtain a variable frequency shift, of the “chirp” type.
- the optical propagation medium can be either an optical fiber, an optical waveguide, or an electro-optical crystal.
- the evolution of the length of the optical path of the optical propagation medium is advantageously linear, and it is carried out by linear evolution of the stress applied to the optical fiber or to the waveguide or the voltage applied to the electro-optical crystal.
- at least two frequency shift modules are connected in parallel, their respective triangular modulations being identical and phase-shifted, a switch being connected to the outputs of these modules and controlled to collect the optical beam alternately, including the frequency shift. is constant.
- FIG. 1 is a simplified block diagram of a Lidar of the prior art, of the type mentioned in the preamble
- - Figure 2 is a simplified block diagram of a Lidar comprising a frequency shift circuit according to the invention
- - Figure 3 is a simplified block diagram of an example of a set of two modules frequency shift according to the invention.
- the present invention is described below with reference to a Lidar, but it is understood that it is not limited to this single application, and that it can be implemented in various fields in which it is necessary to produce a frequency shift on high frequencies such as frequencies above a few Ghz.
- FIG. 1 shows a laser source 1 connected to an input of a coupler 2 with polarization maintenance.
- a first output of the coupler 2 corresponding to the “signal” channel, is connected to an acousto-optical modulator 3, followed by an amplifier 4.
- the amplifier 4 is connected to a first terminal of a coupler 5 with separation of polarizations.
- An output of the coupler 5 is connected to a Lidar beam transmission-reception system, referenced 6 as a whole.
- the second output of coupler 2 is connected to a first input of a polarization maintaining coupler 7, the other input of which is connected to coupler 5.
- the output of coupler 7 is connected to a mixing and detection unit 8, followed a filter circuit 9 and signal processing circuits 10.
- the device 11 can comprise one or more elementary frequency shift modules.
- Each of these elementary modules includes an optical propagation medium such as an optical fiber, an optical waveguide or an electro-optical crystal.
- This support acts on this support so as to vary the length of the optical path. This variation in path length corresponds to a variation in the refractive index of the optical medium. In the case where this support is an optical fiber or a waveguide, this variation can be obtained by imposing a mechanical stress on the optical support.
- the variation is obtained by applying an appropriate electrical voltage to its electrodes.
- the electro-optical crystal then does not operate in a conventional electro-optical modulator, but in a device causing a shift, fixed or variable, in the frequency of the laser beam it receives.
- the evolution of the mechanical stress or the electric tension must, in the present case, be linear as a function of time. This linear evolution generates a constant Doppler shift, and consequently a fixed frequency shift between the “signal” and “local oscillator” channels, which allows coherent heterodyne detection.
- This Doppler shift is imposed on the “signal” channel into which the device 11 is inserted (as shown in solid lines in FIG.
- the second device with shift modules is then referenced 11A and drawn in broken lines in FIG. 2).
- a variation in the length of the optical path is generated when the speed of the beam passing through the device 11 (and / or 11 A) varies. This speed varies inversely proportional to the refractive index of the medium crossed.
- the length of the optical path in the device 11 (and / cm 11 A) is varied linearly as a function of time, which generates a constant Doppler shift.
- the device 11 (and / or 11 A) is provided with two identical shift modules 12, 13, connected in parallel, and followed by a switch 14.
- the device 11 may include more than two modules.
- each of the modules 12, 13, an identical triangular modulation is applied, the modulation in one of the two modules being offset in phase, for example by ⁇ , with respect to that of the other.
- ⁇ the modulation in one of the two modules
- the ascending and descending slopes of these triangular modulations can be identical, but can also be different, for example the descending slope can be much steeper than the other. We do not use in the present case that the ascending slopes, by alternately switching the switch 14 at the output of the module 12 and of the module 13.
- phase shift between the two triangular modulations must be such that the top of the ascending part of one corresponds at least at the beginning of the ascending part of the other.
- a continuous optical beam is obtained at the output of the switch 14, the frequency of which is adjusted by contiguous sections.
- either a single offset module is used, the switch 14 then being deleted, or at least two modules, but in these two cases, only a part is used (ascending, for example) of modulation among n consecutive, with the same direction of variation (n can be greater than 2 or even 10).
- Such a characteristic requires the interruption of the emission of the laser beam during the generation of the unused modulation parts (ascending and / or descending parts), but allows a doubt to be resolved while awaiting the arrival of the real echo. , corresponding to a portion of the laser beam emitted during an ascending modulation part, before emitting the next beam portion.
- the laser beam is passed two or more times through the shifting device. The first reason is economic: if the applied voltage slope is not sufficient to obtain the desired offset over the duration of the pulse, the beam is passed through the module again to reach the desired final offset.
- the frequency offset generated by the device 11 can be controlled using the value of the offset measurement at the output of each offset module.
- the electro-optical control voltage or the mechanical stress applied to the optical propagation medium of these modules can then be controlled by a fixed value or evolving according to a determined law which is a function of the application considered, as for example in the case where “narcissus” phenomena occur (parasitic reflections).
- This frequency offset measurement can be used in the post-processing carried out in the signal processing circuits of the backscattered signal.
- the invention is also applicable when blending in SSB (in phase and in phase quadrature) is carried out.
- the applications of the device of the invention are numerous: in addition to the application considered here at telemetry and velocimetry Lidars, with, if necessary, “chirped” beams, mention will be made of telecommunications (multiplexers and demultiplexers, for example, etc.) )
- the device of the invention thanks to the replacement of the conventional acousto-optical or electro-optical modulator by an offset device with variation in optical path length, makes it possible to avoid the emission of annoying harmonic lines, and to avoid the production of a radio frequency modulation.
- the mechanical or electrical stresses involved in this shifting device are low and therefore easy to produce.
- the electro-optical technologies used by the invention come from those commonly used in telecommunications, the components used being compact and inexpensive, since they are produced in integrated technique. The costs of these components can be further reduced by hybridizing them on a planar waveguide, which reduces the number of connections by wires and optical fibers.
Landscapes
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Optics & Photonics (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
- Optical Radar Systems And Details Thereof (AREA)
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/592,587 US7495822B2 (en) | 2004-03-12 | 2005-03-11 | Frequency shifter in an optical path containing a continuous laser source |
EP05717001A EP1723705B1 (fr) | 2004-03-12 | 2005-03-11 | Dispositif de decalage de frequence dans un chemin optique a source laser continue |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0402600A FR2867620B1 (fr) | 2004-03-12 | 2004-03-12 | Dispositif de decalage de frequence dans un chemin optique a source laser continue |
FR04/02600 | 2004-03-12 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2005099051A1 true WO2005099051A1 (fr) | 2005-10-20 |
Family
ID=34896498
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2005/051104 WO2005099051A1 (fr) | 2004-03-12 | 2005-03-11 | Dispositif de decalage de frequence dans un chemin optique a source laser continue |
Country Status (4)
Country | Link |
---|---|
US (1) | US7495822B2 (fr) |
EP (1) | EP1723705B1 (fr) |
FR (1) | FR2867620B1 (fr) |
WO (1) | WO2005099051A1 (fr) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2867619B1 (fr) * | 2004-03-12 | 2006-06-23 | Thales Sa | Dispositif de decalage de frequence dans un chemin optique a source laser pulsee |
FR2867620B1 (fr) | 2004-03-12 | 2008-10-24 | Thales Sa | Dispositif de decalage de frequence dans un chemin optique a source laser continue |
FR2922314B1 (fr) | 2007-10-16 | 2010-02-26 | Thales Sa | Dispositif optique de mesure de parametres anemometriques |
FR2953934B1 (fr) * | 2009-12-11 | 2011-12-09 | Thales Sa | Sonde anemometrique optique a deux axes de mesure |
US8897654B1 (en) * | 2012-06-20 | 2014-11-25 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | System and method for generating a frequency modulated linear laser waveform |
DE102020123558A1 (de) * | 2020-09-09 | 2022-03-10 | OSRAM Opto Semiconductors Gesellschaft mit beschränkter Haftung | Optoelektronisches halbleiterbauelement, optoelektronische halbleitervorrichtung und lidar-system |
FR3139391A1 (fr) * | 2022-09-02 | 2024-03-08 | Office National D'etudes Et De Recherches Aérospatiales | Systeme lidar pour mesures velocimetriques |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0536783A1 (fr) * | 1991-10-11 | 1993-04-14 | Hughes Aircraft Company | Radar à laser pour détecter des fils |
US5847817A (en) * | 1997-01-14 | 1998-12-08 | Mcdonnell Douglas Corporation | Method for extending range and sensitivity of a fiber optic micro-doppler ladar system and apparatus therefor |
EP1055941A2 (fr) * | 1999-05-28 | 2000-11-29 | Mitsubishi Denki Kabushiki Kaisha | Appareil laser radar et système de communication radar/optique |
US20020075475A1 (en) * | 2000-09-22 | 2002-06-20 | Holton Carvel E. | Doppler rotational velocity sensor |
US20030103211A1 (en) * | 2001-12-04 | 2003-06-05 | Honeywell International Inc. | Sensor and method for detecting fiber optic faults |
CA2476805A1 (fr) * | 2002-02-19 | 2003-08-28 | Honeywell International Inc. | Capteur a fibre optique a type sagnac en ligne avec reglage de la modulation |
Family Cites Families (16)
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US3435230A (en) | 1966-12-08 | 1969-03-25 | Bell Telephone Labor Inc | Optical information transmission system |
US4329664A (en) | 1980-06-09 | 1982-05-11 | Ali Javan | Generation of stable frequency radiation at an optical frequency |
US4856092A (en) * | 1984-11-24 | 1989-08-08 | Plessey Overseas Limited | Optical pulse generating arrangements |
US5272513A (en) | 1991-12-06 | 1993-12-21 | Optical Air Data Systems, L.P. | Laser doppler velocimeter |
US5289252A (en) | 1992-12-08 | 1994-02-22 | Hughes Aircraft Company | Linear frequency modulation control for FM laser radar |
FR2757640B1 (fr) | 1996-12-24 | 1999-04-09 | Thomson Csf | Systeme optique de mesure de vitesse et/ou de distance d'objet |
US6847477B2 (en) * | 2001-02-28 | 2005-01-25 | Kilolamdia Ip Limited | Optical system for converting light beam into plurality of beams having different wavelengths |
US7280674B2 (en) | 2001-06-05 | 2007-10-09 | University Of Florida Research Foundation | Device and method for object illumination and imaging using time slot allocation based upon road changes |
FR2832878B1 (fr) | 2001-11-27 | 2004-02-13 | Thales Sa | Procede de detection et de traitement de signaux pulses dans un signal radioelectrique |
FR2833784B1 (fr) | 2001-12-18 | 2004-02-13 | Thales Sa | Procede d'antibrouillage pour recepteur de signaux radioelectriques a spectre etale |
FR2834563B1 (fr) | 2002-01-08 | 2004-04-02 | Thales Sa | Procede de suppression de signaux radioelectriques pulses et dispositif de mise en oeuvre du procede |
FR2857101B1 (fr) | 2003-07-01 | 2007-01-05 | Thales Sa | Procede de rejection d'interferences perturbant la reception d'un signal de transmission et dispositif |
FR2867619B1 (fr) | 2004-03-12 | 2006-06-23 | Thales Sa | Dispositif de decalage de frequence dans un chemin optique a source laser pulsee |
FR2867620B1 (fr) | 2004-03-12 | 2008-10-24 | Thales Sa | Dispositif de decalage de frequence dans un chemin optique a source laser continue |
FR2880134B1 (fr) | 2004-12-23 | 2007-03-02 | Thales Sa | Dispositif de detection de turbulances atmospheriques |
FR2885744B1 (fr) | 2005-05-10 | 2007-07-20 | Thales Sa | Dispositif de mesure optique actif avec amplification de faible signal |
-
2004
- 2004-03-12 FR FR0402600A patent/FR2867620B1/fr not_active Expired - Fee Related
-
2005
- 2005-03-11 US US10/592,587 patent/US7495822B2/en active Active
- 2005-03-11 EP EP05717001A patent/EP1723705B1/fr active Active
- 2005-03-11 WO PCT/EP2005/051104 patent/WO2005099051A1/fr not_active Application Discontinuation
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0536783A1 (fr) * | 1991-10-11 | 1993-04-14 | Hughes Aircraft Company | Radar à laser pour détecter des fils |
US5847817A (en) * | 1997-01-14 | 1998-12-08 | Mcdonnell Douglas Corporation | Method for extending range and sensitivity of a fiber optic micro-doppler ladar system and apparatus therefor |
EP1055941A2 (fr) * | 1999-05-28 | 2000-11-29 | Mitsubishi Denki Kabushiki Kaisha | Appareil laser radar et système de communication radar/optique |
US20020075475A1 (en) * | 2000-09-22 | 2002-06-20 | Holton Carvel E. | Doppler rotational velocity sensor |
US20030103211A1 (en) * | 2001-12-04 | 2003-06-05 | Honeywell International Inc. | Sensor and method for detecting fiber optic faults |
CA2476805A1 (fr) * | 2002-02-19 | 2003-08-28 | Honeywell International Inc. | Capteur a fibre optique a type sagnac en ligne avec reglage de la modulation |
Also Published As
Publication number | Publication date |
---|---|
EP1723705A1 (fr) | 2006-11-22 |
US20070206190A1 (en) | 2007-09-06 |
EP1723705B1 (fr) | 2012-05-30 |
FR2867620A1 (fr) | 2005-09-16 |
FR2867620B1 (fr) | 2008-10-24 |
US7495822B2 (en) | 2009-02-24 |
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