EP0536025B1 - Frequenzkorrelator - Google Patents

Frequenzkorrelator Download PDF

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Publication number
EP0536025B1
EP0536025B1 EP92402633A EP92402633A EP0536025B1 EP 0536025 B1 EP0536025 B1 EP 0536025B1 EP 92402633 A EP92402633 A EP 92402633A EP 92402633 A EP92402633 A EP 92402633A EP 0536025 B1 EP0536025 B1 EP 0536025B1
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EP
European Patent Office
Prior art keywords
correlated
signals
light
fiber
light source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP92402633A
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English (en)
French (fr)
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EP0536025A1 (de
Inventor
Jean-Luc Thomson-Csf Ayral
Daniel Thomson-Csf Dolfi
Jean-Pierre Thomson-Csf Huignard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
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Thomson CSF SA
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    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06E—OPTICAL COMPUTING DEVICES
    • G06E3/00—Devices not provided for in group G06E1/00, e.g. for processing analogue or hybrid data
    • G06E3/001—Analogue devices in which mathematical operations are carried out with the aid of optical or electro-optical elements
    • G06E3/005—Analogue devices in which mathematical operations are carried out with the aid of optical or electro-optical elements using electro-optical or opto-electronic means

Definitions

  • the invention relates to a frequency correlator and more particularly to a correlator of electrical signals.
  • the invention is particularly applicable to an information processing device ensuring the correlation of very broadband signals - typically 1 to 20 GHz.
  • This device which exploits the non-linear optical properties of single-mode optical fibers (Kerr effect) is particularly well suited to the processing of signals having a large instantaneous bandwidth.
  • This invention is based on a spatial integration of the optical nonlinearities induced in a single mode fiber. It can be extended to the production of broadband programmable filters.
  • FIGS. 1a and 1b show diagrams of the correlation device which is the subject of the invention.
  • This device uses a single-mode fiber F1 having a third order optical non-linearity. That is to say a fiber in which a variation of photoinduced index is proportional to the intensity of the optical field in the core of the fiber.
  • the fiber F1 receives, by its two ends A1, A2, two optical waves whose incident optical fields are perpendicular to the axis of the fiber F1.
  • FIG. 1b two signals to be correlated S 1 (t) and S 2 (t) are transposed on an optical beam of frequency ⁇ o by means of broadband light intensity modulators M 1 and M 2 .
  • These modulators can be made in integrated optics according to known techniques.
  • the modulated beams E1 and E2 are transmitted to the ends A1 and A2 respectively of the fiber.
  • the fiber is therefore the seat of variations in photoinduced indices by the interference of the modulated optical signals. These variations in indices are illustrated in FIG. 2 where ⁇ n (t, z) represents the amplitude of the photoinduced network and ⁇ represents the spatial period of the network of photoinduced index.
  • the signals S 1 (t) and S 2 (t) to be correlated are electrical signals and the modulators M 1 , M 2 are electrooptical modulators.
  • FIG. 3 represents the optical fiber F1 in which an array of indices has been registered by the interference of the modulated optical fields transmitted to the inputs A1 and A2.
  • a reading optical beam (E L ) is transmitted to an input A1 of the fiber M. This transmission can be done using a semi-reflecting mirror MS. The optical beam is partly reflected by the photoinduced index grating. The reflected flux E d is returned by the mirror MS to a photodetector P.
  • the reading beam E L has the same wavelength ⁇ as the modulated beams E 1 and E 2 . Its intensity I o is proportional to E 2 o .
  • Each elementary portion of fiber of length dz (taken equal to c / ⁇ f RF where f RF is the maximum frequency of the microwave signals) at the abscissa z, leads, at each instant t, to a reflection coefficient R determined in amplitude of the probe wave E o .
  • the intensity of the backscattered probe, and therefore the current of the photodetector, is directly proportional to the correlation product of the two signals S 1 and S 2 .
  • FIG. 4 represents a detailed embodiment of the device of the invention.
  • This device comprises a light source L1 (laser) emitting a beam of coherent light of wavelength ⁇ .
  • This beam is transmitted to two electrooptical modulators M1, M2 which modulate the light received from the source L1, using electrical signals S 1 (t) and S 2 (t) to be correlated.
  • the modulated beams E1 and E2 are transmitted to the ends A1 and A2 of the fiber F1.
  • the two beams E1 and E2 interfere in the fiber F1 and give rise to the creation of one or more index networks in the fiber F1.
  • a second light source L2 emits a light beam of the same wavelength ⁇ but of short coherence length corresponding to the inverse of the maximum frequency to be correlated.
  • This beam is transmitted by two semi-reflecting mirrors MS1 and MS2 to the input A1 of the fiber. It is reflected by the photoinduced index networks.
  • the reflected beam (s) are retransmitted by the mirrors MS1 and MS2 to a detector P of light intensity which thus identifies the correlation peaks.
  • a time clock HT is put into service at the instant of application of the signals S 1 (t) and S 2 (t) to be correlated.
  • the detector P informs a processing circuit which records the position of the time clock. The system can thus know the position of each detected correlation peak with respect to the start of the signals S 1 (t) and S 2 (t), that is to say the position of each peak of correlation within the signals S 1 (t) and S 2 (t).
  • the modulators allow very wide band modulation (from 1 to 20 GHz for example) and can be produced in integrated optics.
  • Such a system makes it possible to store pulses of duration 5 ⁇ s on a fiber of 1 km which makes it possible to correlate signals of duration 5 ⁇ s.
  • signals of duration 5 ⁇ s According to another example, on 5 meters of fiber we can correlate pulses of 25 ns.
  • FIG. 5 represents a broadband correlator with amplification of the optical signals transmitted to the fiber F1.
  • the device of FIG. 5 comprises elements which complete the invention.
  • An isolator I1 prevents any return of light to the source L1.
  • the transmission of the beam emitted by the source L1 to the modulators M1 and M2 is done by a coupler C1 achievable in integrated optics.
  • the beams modulated by the modulators M1 and M2 are amplified by fiber amplifiers AF1 and AF2.
  • these amplifiers each include an Erbium doped fiber.
  • the read laser L2 is coupled, to the optical path of the beam modulated by the modulator M1, between the modulator M1 and the amplifier AF1 so that the read beam benefits from the amplification by the amplifier AF1.
  • This coupling is done by an isolator I2 and a coupler C2 (in optics integrated for example).
  • the detector P is coupled to the access A1 of the fiber F1 by a coupler C3 (achievable in integrated optics). Although this is not shown, an amplifier can also be provided between the detector P and the coupler C3.
  • This device allows modulation at low levels, then to adjust the optical intensity to the level necessary to generate a sufficient index variation by the Kerr effect.
  • Amplification gains of 20 to 30 dB for 30 meters of fiber are achievable in fiber amplifiers, for example Erbium doped, at 1.55 ⁇ m.
  • the device of the invention allows a very compact embodiment using integrated optical techniques.
  • the amplifiers can be made as a semiconductor amplifier.
  • the device of the invention can also be applied to a programmable filter.
  • This reflectivity over a fiber length of 5 m makes it possible to use a probe laser with a coherence length of 5 mm to 1.32 ⁇ m of a few tens of mW.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Nonlinear Science (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Optical Communication System (AREA)

Claims (6)

  1. Frequenzkorrelator, dadurch gekennzeichnet, daß er enthält:
    - eine Monomoden-Lichtleitfaser (F1), die eine optische Nichtlinearität der dritten Ordnung aufweist und ein erstes Ende (A1) und ein zweites Ende (A2) besitzt;
    - wenigstens eine erste Lichtquelle (L1), die eine kohärente erste Lichtwelle aussendet;
    - einen ersten Lichtmodulator (M1), der einen Teil der ersten Lichtwelle empfängt, diesen unter der Steuerung eines ersten zu korrelierenden Steuersignals (S1t) moduliert und diese erste modulierte Welle zum ersten Ende der Lichtleitfaser überträgt;
    - einen zweiten Lichtmodulator (M2), der einen anderen Teil der ersten Lichtwelle empfängt, diesen unter der Steuerung eines zweiten zu korrelierenden Steuersignals (S2t) moduliert und diese zweite modulierte Welle zum zweiten Ende der Lichtleitfaser überträgt;
    - eine zweite Lichtquelle (L2), die ein Leselichtbündel in die Lichtleitfaser durch das eine der Enden,
    beispielsweise das erste Ende (A1), sendet;
    - einen Intensitäts-Detektor (P), der an das gleiche Ende der Faser wie die zweite Lichtquelle, gemäß dem gewählten Beispiel das erste Ende (A1), angekoppelt ist.
  2. Korrelator nach Anspruch 1, dadurch gekennzeichnet, daß die zweite Lichtquelle (L2) eine Kohärenzbreite aufweist, die im wesentlichen gleich dem Kehrwert des maximalen Wertes der Frequenzen der zu korrelierenden Signale ist.
  3. Korrelator nach Anspruch 1, dadurch gekennzeichnet, daß die von der ersten Lichtquelle (L1) ausgesendete erste Lichtwelle eine Wellenlänge hat, die im wesentlichen gleich derjenigen des von der zweiten Lichtquelle (L2) ausgesendeten Leselichtbündels ist.
  4. Korrelator nach Anspruch 1, dadurch gekennzeichnet, daß er einen Taktgeber (HT) enthält, der die Zeitpunkte des Empfangs der zu korrelierenden Signale (S1t und S2t) durch die Modulatoren (M1, M2) erfaßt und die Zeitpunkte der Erfassung jeder Korrelationsspitze durch den Detektor (P) angibt.
  5. Korrelator nach Anspruch 4, dadurch gekennzeichnet, daß er eine Verarbeitungsschaltung (CT) enthält, die vom Taktgeber (HT) die Empfangszeiten der zu korrelierenden Signale (S1t und S2t) und vom Detektor (P) die Erfassungszeit jeder Korrelationsspitze empfängt und dadurch die zeitliche Lage jeder Korrelationsspitze in jedem zu korrelierenden Signal berechnet.
  6. Korrelator nach Anspruch 1, dadurch gekennzeichnet, daß die zu korrelierenden Signale (S1t, S2t) elektrische Signale sind und daß die Modulatoren (M1, M2) elektrooptische Modulatoren sind.
EP92402633A 1991-10-01 1992-09-25 Frequenzkorrelator Expired - Lifetime EP0536025B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9112040 1991-10-01
FR9112040A FR2681953B1 (fr) 1991-10-01 1991-10-01 Correlateur de frequences.

Publications (2)

Publication Number Publication Date
EP0536025A1 EP0536025A1 (de) 1993-04-07
EP0536025B1 true EP0536025B1 (de) 1996-08-28

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EP92402633A Expired - Lifetime EP0536025B1 (de) 1991-10-01 1992-09-25 Frequenzkorrelator

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US (1) US5298740A (de)
EP (1) EP0536025B1 (de)
DE (1) DE69213148T2 (de)
FR (1) FR2681953B1 (de)

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5936484A (en) * 1995-02-24 1999-08-10 Thomson-Csf UHF phase shifter and application to an array antenna
FR2732783B1 (fr) * 1995-04-07 1997-05-16 Thomson Csf Dispositif compact de retroprojection
FR2755516B1 (fr) 1996-11-05 1999-01-22 Thomson Csf Dispositif compact d'illumination
DE19722370A1 (de) 1997-05-28 1998-12-03 Alsthom Cge Alcatel Empfänger für ein optisches Nachrichtenübertragungssystem und Verfahren zu dessen Betrieb
FR2769154B1 (fr) * 1997-09-30 1999-12-03 Thomson Csf Dispositif de synchronisation precise
FR2779579B1 (fr) 1998-06-09 2000-08-25 Thomson Csf Dispositif de commande optique pour l'emission et la reception d'un radar large bande
FR2819061B1 (fr) * 2000-12-28 2003-04-11 Thomson Csf Dispositif de controle de polarisation dans une liaison optique
FR2860291B1 (fr) * 2003-09-26 2005-11-18 Thales Sa Dispositif capteur de vitesse de rotation interferometrique a fibre optique
FR2880204B1 (fr) * 2004-12-23 2007-02-09 Thales Sa Source laser a recombinaison coherente de faisceaux
FR2945348B1 (fr) 2009-05-07 2011-05-13 Thales Sa Procede d'identification d'une scene a partir d'images polarisees multi longueurs d'onde
CN112187347B (zh) * 2020-09-18 2022-06-03 常州大学 一种用于测量光纤长度的装置和方法
CN112187345B (zh) * 2020-09-18 2021-07-27 常州大学 一种测量光纤长度的装置和方法

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2618278B1 (fr) * 1987-07-17 1989-12-01 Thomson Csf Correlateur a fibre optique.

Also Published As

Publication number Publication date
DE69213148T2 (de) 1997-01-23
US5298740A (en) 1994-03-29
EP0536025A1 (de) 1993-04-07
DE69213148D1 (de) 1996-10-02
FR2681953B1 (fr) 1993-11-05
FR2681953A1 (fr) 1993-04-02

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