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Optical fourier transform device and method

外国特許コード F110005758
整理番号 Y0426WO
掲載日 2011年9月14日
出願国 アメリカ合衆国
出願番号 58493204
公報番号 20070273958
公報番号 7352504
出願日 平成16年12月27日(2004.12.27)
公報発行日 平成19年11月29日(2007.11.29)
公報発行日 平成20年4月1日(2008.4.1)
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
  • 特願2004-000464 (2004.1.5) JP
  • 2004WO-JP19517 (2004.12.27) WO
発明の名称 (英語) Optical fourier transform device and method
発明の概要(英語) (US7352504)
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 dispersion (secondary dispersion), thereby converting the time waveform of the inputted signal light pulse into the shape of the frequency spectrum.
特許請求の範囲(英語) [claim1]
1. An optical Fourier transform device comprising: a parabolic optical pulse generator to generate a control optical pulse of a shape expressed by a quadratic function or a parabola;
a coupler to couple a signal optical pulse with the control optical pulse;an optical Kerr medium to linearly chirp the signal optical pulse over an entire pulse, or a wide time range by cross phase modulation between the signal optical pulse and the control optical pulse;
and
a dispersive medium having a group-velocity dispersion, wherein the launched signal optical pulse and the control optical pulse are coupled by the coupler and are introduced into the optical Kerr medium, the launched signal optical pulse is linearly chirped at a chirp rate K by the optical Kerr medium by the cross phase modulation between the signal optical pulse and the control optical pulse, the signal optical pulse emitted from the optical Kerr medium is made to pass through the dispersive medium whose dispersion amount D is D=1/K, to convert a temporal waveform of the launched signal optical pulse into a shape of a frequency spectrum thereof.
[claim2]
2. The optical Fourier transform device according to claim 1, wherein the signal optical pulse having passed through the dispersive medium and the control optical pulse are again coupled and are introduced into the optical Kerr medium, the signal optical pulse having passed through the dispersive medium is again linearly chirped by the optical Kerr medium by the cross phase modulation between the signal optical pulse and the control optical pulse, to convert the temporal waveform of the launched signal optical pulse into the shape of the frequency spectrum thereof, and the shape of the frequency spectrum of the launched signal optical pulse into the temporal waveform thereof.
[claim3]
3. The optical Fourier transform device according to claim 2, comprising: an optical filter that separates the signal optical pulse having passed through the optical Kerr medium from the control optical pulse and introduces the separated signal optical pulse into the dispersive medium;
and
a coupler that again couples the signal optical pulse having passed through the dispersive medium and the separated control optical pulse and introduces them into the optical Kerr medium.
[claim4]
4. The optical Fourier transform device according to claim 2, wherein the signal optical pulse is made to pass through the optical Kerr medium twice so that chirp is completely compensated, and a transform-limited waveform without chirp is obtained at output.
[claim5]
5. The optical Fourier transform device according to claim 1, wherein the signal optical pulse is made to pass through the optical Kerr medium twice so that chirp is completely compensated, and a transform-limited waveform without chirp is obtained at output.
[claim6]
6. The optical Fourier transform device according to claim 1, wherein a chirp rate K of a frequency chirp applied to the signal optical pulse by the cross phase modulation between the signal optical pulse and the control optical pulse by the optical Kerr medium and a dispersion amount D of the dispersive medium satisfy a relation of D=1/K, and the chirp rate K can be adjusted by one of or plurality of a peak power of the control optical pulse, wherein a length of the optical Kerr medium, and a nonlinear refractive index of the optical Kerr medium.
[claim7]
7. The optical Fourier transform device according to claim 1, wherein the parabolic optical pulse generator comprises: an optical pulse transmitter to generate an optical pulse;
and
an optical fiber amplifier which has a normal dispersion, and through which the optical pulse from the optical pulse transmitter is transmitted.
[claim8]
8. The optical Fourier transform device according to claim 1, wherein the parabolic optical pulse generator comprises: an optical pulse transmitter to generate an optical pulse;
an optical filter whose amplitude transmission characteristic is expressed by a quadratic function or a parabola, which changes a frequency spectrum of the optical pulse from the optical pulse transmitter into a quadratic function type or a parabola;
and
an optical Fourier transform circuit to convert a temporal waveform of the optical pulse into a shape of a frequency spectrum waveform of the optical pulse having passed through the optical filter.
[claim9]
9. The optical Fourier transform device according to claim 1, wherein in order to efficiently generate the high-speed cross phase modulation between the control light and the signal light, a low dispersion optical Kerr medium having a small dispersion value 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.
[claim10]
10. The optical Fourier transform device according to claim 1, comprising: a clock extraction circuit to extract a clock signal based on the signal optical pulse, andan optical delay element to give an optical delay to the control optical pulse, wherein the parabolic optical pulse generator generates the control optical pulse in accordance with the clock signal from the clock extraction circuit, and/or the optical delay element gives the optical delay to the control optical pulse so that timing is matched with the signal optical pulse.
[claim11]
11. An optical Fourier transform device comprising: a parabolic optical pulse generator to generate a control optical pulse of a shape expressed by a quadratic function or a parabola;a coupler to couple a signal optical pulse with the control optical pulse;an optical Kerr medium to linearly chirp the signal optical pulse over an entire pulse or a wide time range by cross phase modulation between the signal optical pulse and the control optical pulse;
and
a dispersive medium having a group-velocity dispersion, wherein the parabolic optical pulse generator comprises:a optical pulse transmitter to generate a optical pulse;
and
a dispersion-decreasing fiber in which an absolute value of a normal dispersion is decreased in a longitudinal direction, whereinthe launched signal optical pulse is made to passes through the dispersive medium, the signal optical pulse emitted from the dispersive medium and the control optical pulse are coupled by the coupler and are introduced into the optical Kerr medium, the signal optical pulse emitted from the dispersive medium is linearly chirped by the optical Kerr medium by the cross phase modulation between the signal optical pulse and the control optical pulse, to convert a shape of a frequency spectrum of the launched signal optical pulse into a temporal waveform.
[claim12]
12. The optical Fourier transform device according to claim 11, wherein the signal optical pulse linearly chirped by the optical Kerr medium is again made to pass through the dispersive medium, to convert the temporal waveform of the launched signal optical pulse into the shape of the frequency spectrum thereof, and the shape of the frequency spectrum of the launched signal optical pulse into the temporal waveform thereof.
[claim13]
13. The optical Fourier transform device according to claim 12, wherein the signal optical pulse is made to pass through the dispersive medium twice so that chirp is completely compensated, and a transform-limited waveform without chirp is obtained at output.
[claim14]
14. The optical Fourier transform device according to claim 11, wherein the signal optical pulse is made to pass through the dispersive medium twice so that chirp is completely compensated, and a transform-limited waveform without chirp is obtained at output.
[claim15]
15. An optical Fourier transform device comprising: a parabolic optical pulse generator to generate a control optical pulse of a shape expressed by a quadratic function or a parabola;a coupler to couple a signal optical pulse with the control optical pulse;an optical Kerr medium to linearly chirp the signal optical pulse over an entire pulse or a wide time range by cross phase modulation between the signal optical pulse and the control optical pulse;
and
a dispersive medium having a group-velocity dispersion, wherein the parabolic optical pulse generator comprises:an optical pulse transmitter to generate a optical pulse;
and
a dispersion-decreasing fiber in which an absolute value of a normal dispersion is decreased in a longitudinal direction, wherein the launched signal optical pulse and the control optical pulse are coupled by the coupler and are introduced into the optical Kerr medium, the launched signal optical pulse is linearly chirped by the optical Kerr medium by the cross phase modulation between the signal optical pulse and the control optical pulse, the signal optical pulse emitted from the optical Kerr medium is made to pass through the dispersive medium, to convert a temporal waveform of the launched signal optical pulse into a shape of a frequency spectrum thereof.
[claim16]
16. The optical Fourier transform device according to claim 15, wherein the dispersion-decreasing fiber 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 D(z)=D0/(1+D0GAMMA z) (where D(z): a function to express the change in the dispersion value, z: a coordinate of the fiber in the longitudinal direction, D0: a function value at an incident end (z=0), and GAMMA : a rate of decrease of magnitude of the normal dispersion).
[claim17]
17. An optical Fourier transform method wherein a launched signal optical pulse and a control optical pulse of a shape expressed by a quadratic function or a parabola are coupled and are introduced into an optical Kerr medium, the launched signal optical pulse is linearly chirped at a chirp rate K over an entire pulse or a wide time range by the optical Kerr medium by the cross phase modulation between the signal optical pulse and the control optical pulse, the signal optical pulse emitted from the optical Kerr medium is made to pass through the dispersive medium having a group-velocity dispersion whose dispersion amount D is D=1/K, to convert a temporal waveform of the launched signal optical pulse into a shape of a frequency spectrum thereof.
[claim18]
18. The optical Fourier transform method according to claim 17, wherein the signal optical pulse having passed through the dispersive medium and the control optical pulse are again coupled and are introduced into the optical Kerr medium, the signal optical pulse having passed through the dispersive medium is again linearly chirped by the optical Kerr medium by the cross phase modulation between the signal optical pulse and the control optical pulse, to convert the temporal waveform of the launched signal optical pulse into the shape of the frequency spectrum thereof, and the shape of the frequency spectrum of the launched signal optical pulse into the temporal waveform thereof.
  • 発明者/出願人(英語)
  • HIROOKA TOSHIHIKO
  • NAKAZAWA MASATAKA
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • G01J011/00
  • G02F001/35C
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