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Optical fourier transform device and method

外国特許コード F110004201
整理番号 Y0426WO
掲載日 2011年7月12日
出願国 欧州特許庁(EPO)
出願番号 04807872
公報番号 1705516
公報番号 1705516
出願日 平成16年12月27日(2004.12.27)
公報発行日 平成18年9月27日(2006.9.27)
公報発行日 平成27年6月3日(2015.6.3)
国際出願番号 JP2004019517
国際公開番号 WO2005066707
国際出願日 平成16年12月27日(2004.12.27)
国際公開日 平成17年7月21日(2005.7.21)
優先権データ
  • 2004JP019517 (2004.12.27) WO
  • 特願2004-000464 (2004.1.5) JP
発明の名称 (英語) Optical fourier transform device and method
発明の概要(英語) Optical Fourier transform is executed over a wide time range.
A quadratic function type optical pulse generator (7) generates a control light pulse of a shape expressed by a quadratic function or a parabola according to a clock signal based on a signal light pulse from an optical coupler (1).
The signal light pulse inputted is multiplexed by a multiplexer (9) with the control light pulse optically delayed by an optical delay element (8) so that the timing is matched with the signal light pulse, and introduced into an optical Kerr medium (10).
In the optical Kerr medium (10), the signal light pulse inputted by the mutual phase modulation between the signal light pulse and the control light pulse is subjected to a linear phase modulation (frequency chirp) over the entire pulse or a wide time range.
After that, the signal light pulse isolated by an optical filter (11) is introduced into the dispersion medium (12) having a group velocity dis persion (secondary dispersion), thereby converting the time waveform of the inputted signal light pulse into the shape of the frequency spectrum.(see diagramm)
特許請求の範囲(英語) [claim1]
1. An optical Fourier transform device comprising: phase modulation means (10) adapted to linearly chirp a signal optical pulse at a rate K; and a dispersive medium (12) having a group-velocity dispersion and whose dispersion amount D is D=1/K, wherein the device is configured such that the chirped signal optical pulse emitted from the phase modulation means (10) is made to pass through the dispersive medium (12), such that the temporal waveform of the optical pulse obtained at the output of the dispersive medium (12) is proportional to the spectrum shape of the signal optical pulse; characterized by: an optical pulse generator (7) comprising an optical pulse transmitter (13), wherein the optical pulse transmitter (13) is adapted to be driven by a clock signal extracted from said signal optical pulse by a clock extraction circuit (4), and wherein said optical pulse generator (7) is adapted to generate a control optical pulse of a shape expressed by a quadratic function or a parabola from an optical pulse generated by the optical pulse transmitter (13), wherein the device is configured such that said control optical pulse is synchronized with said signal optical pulse; and a coupler (9) adapted to couple the signal optical pulse with the control optical pulse; wherein said phase modulation means (10) is adapted to receive the coupled signal optical pulse and control optical pulse, and comprises an optical Kerr medium (10) adapted to linearly chirp the signal optical pulse over the entire signal optical pulse by cross phase modulation between the signal optical pulse and the control optical pulse.
[claim2]
2. The optical Fourier transform device according to claim 1, wherein
the device is configured such that: the signal optical pulse having passed through the dispersive medium (12) and the control optical pulse are again coupled and are introduced into the optical Kerr medium (10), the signal optical pulse having passed through the dispersive medium (12) is again linearly chirped by the optical Kerr medium (10) by the cross phase modulation between the signal optical pulse and the control optical pulse, thereby, the temporal waveform of the optical pulse obtained at the output of the Kerr medium (10) is proportional to the spectrum shape of the signal optical pulse and the frequency spectrum of the optical pulse obtained at the output of the Kerr medium (10) is proportional to the temporal waveform of the signal optical pulse.
[claim3]
3. The optical Fourier transform device according to claim 1 or 2, wherein
the device is configured such that the signal optical pulse is made to pass through the optical Kerr medium (10) twice so that chirp is completely compensated, and a transform-limited waveform without chirp is obtained at output.
[claim4]
4. The optical Fourier transform device according to claim 2, further comprising: an optical filter (11) adapted to separate the signal optical pulse having passed through the optical Kerr medium (10) from the control optical pulse and to introduce the separated signal optical pulse into the dispersive medium (12); and a coupler (9') adapted to again couple the signal optical pulse having passed through the dispersive medium and the separated control optical pulse and introduce them into the optical Kerr medium (10).
[claim5]
5. An optical Fourier transform device comprising: a dispersive medium (12) having a group-velocity dispersion, the device being configured such that a signal optical pulse is made to pass through the dispersive medium (12); an optical pulse generator (7) adapted to generate a control optical pulse; a coupler (9) adapted to couple the signal optical pulse emitted from the dispersive medium with the control optical pulse; an optical Kerr medium (10) adapted to receive the coupled signal optical pulse and control optical pulse and to linearly chirp the signal optical pulse at a rate K by cross phase modulation between the signal optical pulse and the control optical pulse; wherein the dispersive medium has a dispersion amount D = 1/K; and wherein the optical pulse generator comprises an optical pulse transmitter (13) adapted to generate an optical pulse; characterized in that: the optical pulse transmitter (13) is adapted to be driven by a clock signal extracted from the signal optical pulse by a clock extraction circuit (4); the optical pulse generator (7) further comprises a dispersion-decreasing fiber (16) adapted to decrease an absolute value of a normal dispersion in a longitudinal direction; the optical pulse generator (7) is adapted to generate a control optical pulse of a shape expressed by a quadratic function or a parabola from the optical pulse generated by the optical pulse transmitter (13); the device is configured such that the control optical pulse is synchronized with the signal optical pulse; the optical Kerr medium (10) is adapted to linearly chirp the signal optical pulse over the entire signal optical pulse by the cross phase modulation between the signal optical pulse and the control optical pulse; and the frequency spectrum of the optical pulse obtained at the output of the Kerr medium (10) is proportional to the temporal waveform of the signal optical pulse.
[claim6]
6. The optical Fourier transform device according to claim 5, wherein
the device is configured such that the signal optical pulse linearly chirped by the optical Kerr medium (10) is again made to pass through the dispersive medium (12), thereby, the temporal waveform of the optical pulse obtained at the output of the dispersive medium (12) is proportional to the spectrum shape of the signal optical pulse and the frequency spectrum of the optical pulse obtained at the output of the dispersive medium (12) is proportional to the temporal waveform of the signal optical pulse.
[claim7]
7. The optical Fourier transform device according to claim 5 or 6, wherein
the device is configured such that the signal optical pulse is made to pass through the dispersive medium (12) twice so that chirp is completely compensated, and a transform-limited waveform without chirp is obtained at output.
[claim8]
8. The optical Fourier transform device according to claim 1, wherein
the chirp rate K can be adjusted by changing one of or a plurality of a peak power of the control optical pulse, a length of the optical Kerr medium (10), and a nonlinear refractive index of the optical Kerr medium (10).
[claim9]
9. The optical Fourier transform device according to claim 1, wherein the optical pulse generator (7) further comprises an optical fiber amplifier (14) which has a normal dispersion and through which the optical pulse from the optical pulse transmitter (13) is transmitted.
[claim10]
10. The optical Fourier transform device according to claim 1, wherein
the optical pulse generator (7) further comprises: a dispersion-decreasing fiber (16) in which an absolute value of a normal dispersion is decreased in a longitudinal direction.
[claim11]
11. The optical Fourier transform device according to claim 10, wherein
the dispersion-decreasing fiber (16) includes fibers in which a change in a dispersion value is discretely approximated in each section by cascading plural kinds of optical fibers in which a dispersion value is continuously changed, or a dispersion value is constant or is linearly changed in a longitudinal direction, or one fiber in which a dispersion value is continuously changed, and the change in the dispersion value is expressed by a following expression or is approximated by the following expression (Equation image 28 not included in text)
where D(z) is a function expressing the change in the dispersion value, z is a coordinate of the fiber in the longitudinal direction, D 0 is a function value at the incident end of the fiber for z = 0, and GAMMA is a rate of decrease of magnitude of the normal dispersion.
[claim12]
12. The optical Fourier transform device according to claim 1, wherein the optical pulse generator (7) comprises: an optical pulse transmitter (13) adapted to generate an optical pulse; an optical filter (17) whose amplitude transmission characteristic is expressed by a quadratic function or a parabola, adapted to change a frequency spectrum of the optical pulse from the optical pulse transmitter (13) into a quadratic function type or a parabola; and an optical Fourier transform circuit (18) adapted such that the temporal waveform of the optical pulse obtained at the output thereof is proportional to the spectrum shape of the optical pulse having passed through the optical filter (17).
[claim13]
13. The optical Fourier transform device according to claim 1, wherein
a low dispersion optical Kerr medium (10) is used as the optical Kerr medium, or a wavelength of the signal light and/or the control light is set so that wavelengths of the signal light and the control light become wavelengths symmetrical to each other with respect to a zero-dispersion wavelength of the optical Kerr medium (10).
[claim14]
14. The optical Fourier transform device according to claim 1, further comprising: a clock extraction circuit (4) adapted to extract the clock signal based on the signal optical pulse, and an optical delay element (8) adapted to give an optical delay to the control optical pulse, wherein the optical delay element (8) is adapted to give the optical delay to the control optical pulse such that the centre time position of the control optical pulse is matched with that of the signal optical pulse.
[claim15]
15. An optical Fourier transform method comprising: linearly chirping a signal optical pulse at a chirp rate K; and passing the chirped signal optical pulse through a dispersive medium (12) having a group-velocity dispersion whose dispersion amount D is D=1/K, such that the temporal waveform of the optical pulse obtained at the output of the dispersive medium is proportional to the spectrum shape of the signal optical pulse; characterized by: generating a control optical pulse, having a shape expressed by a quadratic function or a parabola, from an optical pulse generated by an optical pulse transmitter (13), the optical pulse transmitter (13) being driven by a clock signal extracted from the signal optical pulse by a clock extraction circuit (4), synchronizing the control optical pulse with the signal optical pulse; coupling the signal optical pulse and the control optical pulse; introducing the signal optical pulse and the control optical pulse into an optical Kerr medium (10), linearly chirping the signal optical pulse at a chirp rate K over the entire signal optical pulse by the optical Kerr medium (10) by the cross phase modulation between the signal optical pulse and the control optical pulse, and making the signal optical pulse emitted from the optical Kerr medium (10) pass through the dispersive medium (12).
[claim16]
16. The optical Fourier transform method according to claim 15, wherein
the signal optical pulse having passed through the dispersive medium (12) and the control optical pulse are again coupled and are introduced into the optical Kerr medium (10), the signal optical pulse having passed through the dispersive medium (12) is again linearly chirped by the optical Kerr medium (10) by the cross phase modulation between the signal optical pulse and the control optical pulse, thereby, the temporal waveform of the optical pulse obtained at the output of the Kerr medium (10) is proportional to the spectrum shape of the signal optical pulse and the frequency spectrum of the optical pulse obtained at the output of the Kerr medium (10) is proportional to the temporal waveform of the signal optical pulse.
  • 出願人(英語)
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
  • 発明者(英語)
  • HIROOKA TOSHIHIKO
  • NAKAZAWA MASATAKA
国際特許分類(IPC)
欧州特許分類/主・副
  • G01J011/00
  • G02F001/35C
指定国 Contracting States: DE FR GB IT SE
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