JP2005051257A - Multi-wavelength measuring system having time-division wavelength multiplex pulse light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-wavelength measuring system having a time-division wavelength division multiplex pulse light source, which can change multiplexed super-short pulse light of various wavelengthes at a high speed over a wide band at a desired time-division period by installing an oscillator synchronous with output of a short pulse light source to the short pulse light source, a light intensity modulator , and an optical fiber, and by driving the light intensity modulator with the output of the oscillator. <P>SOLUTION: The muli-wavelength measuring system is equipped with the time-division wavelength multiplex pulse light source A, outputting a pulse light temporally changing the wavelength periodically, which includes the short pulse light source 1, the oscillator 5 synchronous with repeated frequencies of the output of the short pulse light source 1, the light intensity modulator 2 which is driven by the output of the oscillator 5 and changes the intensity of transmitted light, and an optical fiber 7 by which a soliton pulse of wavelength shifted linearly to the intensity of the incident pulse light from the light intensity modulator 2; a to-be-measured object 21 which introduces the short pulse light output from the pulse light source A; and a device which evaluates the to-be-measured object 21. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multi-wavelength light source having a time-division wavelength multiplex pulse light source that generates an ultra-short pulse whose wavelength of light periodically changes with time using a single ultra-short pulse light source, an optical intensity modulator and an optical fiber. It relates to a measurement system.

Conventionally, ultra-short pulse light has been generated by using a dye laser or a solid-state laser. However, the optical system is large and complicated, and the variable wavelength range is as narrow as several tens of nm.
None

  In addition, since the wavelength variable light source so far has changed the wavelength by mechanically rotating an optical component such as a mirror, the wavelength cannot be changed at high speed, and the apparatus is large.

  Further, although the wavelength-variable light can be periodically output by a wavelength variable light source or the like, soliton pulses having different wavelengths cannot be periodically output almost simultaneously.

  In the present invention, the above problems are eliminated, and an oscillator synchronized with the output of the short pulse light source is added to the short pulse light source, the light intensity modulator, and the optical fiber, and the light intensity modulator is driven by the output of the oscillator. Another object of the present invention is to provide a multi-wavelength measurement system having a time-division wavelength-multiplexed pulse light source capable of changing multiple ultrashort pulse lights having different wavelengths at an arbitrary time-division period over a wide band at high speed.

In order to achieve the above object, the present invention provides
[1] In a multi-wavelength measurement system having a time division wavelength multiplexed pulse light source, a short pulse light source, an oscillator synchronized with the repetition frequency of the output of the short pulse light source, driven by the output of the oscillator, and the intensity of transmitted light A light intensity modulator that periodically changes with respect to time, and an optical fiber that generates a soliton pulse having a wavelength shifted substantially linearly with respect to the intensity of the incident pulse light from the light intensity modulator. In contrast, a time-division wavelength multiplex pulse light source that outputs pulsed light whose wavelength changes periodically, an object to be measured that introduces short pulse light output from the pulsed light source, and an apparatus for evaluating the object to be measured It is characterized by comprising.

  [2] In the multi-wavelength measurement system having the time-division wavelength multiplex pulse light source described in [1], the output light from the measurement object is measured using a single light receiver, and the signal is measured in a time-division manner. It is characterized by that.

  [3] The multi-wavelength measurement system having the time-division wavelength multiplex pulse light source according to [1], wherein output light from the measurement object is separated according to wavelength, and each signal is measured.

  [4] In a multi-wavelength measurement system having a time-division wavelength multiplex pulse light source, a short pulse light source, an oscillator synchronized with the repetition frequency of the output of the short pulse light source, and an output of the oscillator to drive the intensity of transmitted light. A light intensity modulator that periodically changes with respect to time, and an optical fiber that generates a soliton pulse having a wavelength shifted substantially linearly with respect to the intensity of the incident pulse light from the light intensity modulator. A time-division wavelength-multiplexed pulse light source that outputs pulse light whose wavelength changes periodically and is assembled in a portable manner, a measurement object that introduces short pulse light output from the pulse light source, and the measurement object It is characterized by comprising a device for evaluating the above.

  [5] In the multi-wavelength measurement system having the time-division wavelength multiplex pulse light source as described in [4] above, the output light from the measurement object is measured using a single light receiver, and the signal is measured in a time-division manner. It is characterized by that.

  [6] The multi-wavelength measurement system having the time-division wavelength multiplex pulse light source according to [4], wherein output light from the measurement target is separated according to wavelength, and each signal is measured.

  [7] The multi-wavelength measurement system having the time-division wavelength multiplex pulse light source according to [1] or [4], wherein the short pulse light source is a femtosecond fiber laser.

  [8] In the multi-wavelength measurement system having the time-division wavelength-multiplexed pulse light source according to [1] or [4], the optical fiber is a constant polarization fiber.

  [9] In the multi-wavelength measurement system having the time-division wavelength multiplex pulse light source described in [8] above, the polarization direction of the incident light is tilted from the birefringence axis of the constant polarization fiber, and simultaneously two different wavelength pulses are generated. It is characterized by.

Since it was configured as above,
(A) Ultrashort pulse light whose wavelength changes at high speed can be output from a single fiber.
(B) The wavelength of the pulsed light can be periodically varied over time in a wide band.
(C) An ideal soliton pulse can be output over a wide band with a compact system.

  According to the present invention, the following effects can be achieved.

  (A) In the time division wavelength multiplexed pulsed light generator (light source), the wavelength of the light changes depending on the intensity of the light. Can vary.

  Further, the generated pulse light becomes an ideal soliton pulse.

  (B) The multi-wavelength measurement system having the time-division wavelength multiplex pulse light source of the present invention makes it possible to perform spectroscopic measurement and various optical measurements depending on the wavelength with a simple system at high speed.

  The multi-wavelength measurement system having a time-division wavelength multiplex pulse light source of the present invention includes a short pulse light source, an oscillator synchronized with the repetition frequency of the output of the short pulse light source, and an output of the oscillator to drive the intensity of transmitted light. A light intensity modulator that periodically changes with respect to time, and an optical fiber that generates a soliton pulse having a wavelength shifted substantially linearly with respect to the intensity of the incident pulse light from the light intensity modulator. In contrast, a time-division wavelength multiplex pulse light source that outputs pulsed light whose wavelength changes periodically, an object to be measured that introduces short pulse light output from the pulsed light source, and an apparatus for evaluating the object to be measured It has. Therefore, it is possible to perform spectroscopic measurement and various optical measurements depending on the wavelength at high speed with a simple system.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a block diagram of a time division wavelength multiplexing light source showing a first embodiment of the present invention.

  As shown in this figure, the short pulse light output from the fs (femtosecond) fiber laser 1 is passed through a light intensity modulator 2 which is an optical characteristic adjuster. Further, the repetition signal 3 of the pulsed light output from the fs fiber laser 1 is passed through the frequency divider 4, and the oscillator 5 is driven by the signal from the frequency divider 4, thereby generating an arbitrary repetitive waveform. The light intensity modulator 2 is driven by the output of the oscillator 5 to periodically change the intensity of transmitted light with respect to time. Reference numeral 8 denotes a wavelength filter.

  On the other hand, in the optical fiber 7, a soliton pulse having a wavelength shifted substantially linearly with respect to the intensity of the pulsed light is generated.

  FIG. 2 represents the output of the optical fiber, the horizontal axis represents time, and the vertical axis represents light wavelength and light intensity.

  As is clear from this figure, beautiful soliton pulses (wavelength 1 to wavelength 4) whose wavelength is periodically changed are repeatedly output at equal intervals.

  Therefore, a soliton whose wavelength changes periodically can be obtained at the output of the optical fiber 7. At this time, although the excitation pulse that has not been converted into the soliton pulse is also output to the output of the optical fiber 7, these components can be removed using the wavelength filter 8 to generate only the soliton pulse.

  Next, FIG. 3 is a diagram showing the time change of the oscillator output and the time change of the wavelength of the soliton pulse according to the embodiment of the present invention, and FIG. 3 (a) shows when the oscillator output is a sawtooth wave. FIG. 3B shows the case where the signal changes stepwise.

  Since the light intensity modulator 2 is driven by the output of the oscillator 5, the wavelength of the soliton pulse also changes according to the output of the oscillator 5. Therefore, if a sawtooth wave is output from the oscillator 5, as shown in FIG. 3A, if a soliton pulse whose wavelength changes to a sawtooth wave or a signal which changes stepwise is used, FIG. As shown in (b), a soliton pulse whose wavelength changes stepwise can be output.

  In the first embodiment, a short pulse light source (fs fiber laser) 1, an oscillator 5 synchronized with the repetition frequency of the output of the short pulse light source 1, and an output of the oscillator 5 are driven. A light intensity modulator 2 that modulates the output of the light, and an optical fiber 7 that receives the incident pulse from the light intensity modulator 2 and changes the wavelength of the output pulse. Outputs changing pulse light.

  For example, a constant polarization optical fiber is used as the optical fiber 7.

  In this case, the polarization direction of the incident light is tilted from the birefringence axis of the constant polarization optical fiber, and pulses of two different wavelengths are generated simultaneously.

  Furthermore, the short pulse light source (fs fiber laser) 1, an oscillator 5 synchronized with the repetition frequency of the output of the short pulse light source 1, and the output from the short pulse light source 1 are driven by the output of the oscillator 5. A light intensity modulator 2 and an optical fiber 7 that receives an incident pulse from the light intensity modulator 2 and changes the wavelength of the output pulse, and outputs pulsed light whose wavelength periodically changes with time. In addition, it was assembled into a portable type.

  Further, the optical fiber is a constant polarization optical fiber.

  Further, the polarization direction of incident light is tilted from the birefringence axis of the constant polarization fiber, and pulses of two different wavelengths are generated simultaneously.

  FIG. 4 is a diagram showing an optical spectrum obtained by measuring the output of the time division wavelength multiplex pulse light source according to the embodiment of the present invention using an optical spectrum observer. The horizontal axis represents wavelength and the vertical axis represents spectrum intensity.

  Since pulsed light whose wavelength periodically changes at high speed is output, the spectrum observer simultaneously observes multiple wavelength spectra. The spectrum wavelength is a beautiful sech2 type. In the figure, when the optical fiber length is 220 m, time-division wavelength multiplexed pulse light is generated at four wavelengths of 1.56 μm, 1.625 μm, 1.675 μm, and 1.725 μm. So far, wavelength shifts of up to 1.56-2.03 μm have been observed.

FIG. 5 is a diagram showing an autocorrelation waveform of a soliton pulse showing an embodiment of the present invention.
In this figure, the time waveform of the generated soliton pulse is an ideal sech2 type without a pedestal. The time waveform is observed stably. When the optical fiber length was 220 m, the time width of the autocorrelation waveform was 430 fs. At this time, the width of the time waveform is estimated to be 280 fs.

  FIG. 6 is a block diagram of a two-wavelength time division multiplexed multi-wavelength pulsed light generation system showing a second embodiment of the present invention.

  In this embodiment, a constant polarization optical fiber 11 is used as an optical fiber. When pulsed light is incident with the polarization direction tilted with respect to the birefringence axis of the polarization optical fiber 11, two polarization components simultaneously generate soliton pulses, so that a two-wavelength soliton pulse can be obtained at the output. . By combining this method with the above-described method of modulating the light intensity modulator using an oscillator, the wavelength of the time-division wavelength multiplexed pulse light can be further doubled. Here, 12 is a wavelength filter, and 13 is a polarization beam splitter. In this polarization beam splitter 13, the two deflection components can be separated.

  Next, a multi-wavelength measurement system having the above-described time division wavelength multiplex pulse light source will be described.

  FIG. 7 is a diagram (part 1) illustrating a time division multi-wavelength measurement system having a time division wavelength multiplexed pulse light source according to an embodiment of the present invention.

  As shown in this figure, using the time-division wavelength multiplex pulse light source A shown in FIG. 1, the change in transmittance and reflectance of the object to be measured 21 at multiple wavelengths is changed to a single light receiver (photodiode). The time division signal processing unit 23 and the personal computer 24 are used for time division measurement. The signal received by the photodiode 22 is amplified and then temporally divided and processed by the time division signal processing unit 23 and measured for each wavelength.

  FIG. 8 is a diagram showing a signal processing system of a time division multi-wavelength measurement system showing an embodiment of the present invention.

  In this figure, 31 is a photodiode, 32 is an amplifier, 33 to 36 are sample and hold circuits 1 to 4, 37 is a control signal generator, and 38 is a personal computer.

  As shown in FIG. 8, time division wavelength multiplexed pulse light is received by a photodiode 31 and amplified using an amplifier 32. Further, a signal for controlling the sample and hold circuits 33 to 36 is generated by the control signal generator 37 using the oscillator output signal, and when the pulsed light of wavelength 1 is received, the sample and hold circuit 33 (circuit 1). The signal is held, and when the pulsed light of wavelength 2 is received, the signal is held by the sample & hold circuit 34 (circuit 2). In this way, after the signals of the respective wavelengths are held by the sample and hold circuits 33 to 36, they are taken into the personal computer 38 and the signals of the respective wavelengths are simultaneously measured.

  FIG. 9 is a diagram showing measurement results of time-division multi-wavelength spectroscopic measurement for atoms / molecules in gas using time-division wavelength multiplex pulse light according to an embodiment of the present invention. The horizontal axis represents time, and the vertical axis represents transmitted light intensity. The change in transmitted light intensity corresponds to the change in the density of each atom and molecule.

  As is apparent from this figure, the change in the transmitted light intensity of the medium with respect to the change in time can be simultaneously measured at multiple wavelengths. Such spectral measurement at multiple wavelengths has not been possible with a single optical system.

  FIG. 10 is a diagram (part 2) illustrating a multi-wavelength spectroscopic measurement system having a time-division wavelength multiplex pulse light source according to an embodiment of the present invention. In this embodiment, the same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 10, the output from the time-division wavelength multiplex pulse light source A is incident on the object 21 to be measured, separated for each wavelength component by the diffraction grating 41 or the wavelength filter, received, amplified by the amplifier 42, and signal processing. The data is taken into the personal computer 44 via the unit 43.

As mentioned above, according to the present invention,
(1) It is possible to simultaneously perform measurement using multi-wavelength ultrashort pulse light in a single system in a time division manner.
(2) With a compact system, multi-wavelength measurement using ultra-short pulse light can be performed over a wide band.
(3) An ideal soliton pulse can be generated.

  In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.

  The multi-wavelength measurement system having the time-division wavelength multiplex pulse light source of the present invention is suitable for spectroscopic measurement and various optical measurements depending on the wavelength.

It is a block diagram of the time division wavelength multiplexing light source which shows 1st Example of this invention. It is a figure which shows the soliton pulse of the time division wavelength multiplexing light source which shows the Example of this invention. It is a figure which shows the time change of the wavelength of the soliton pulse accompanying the time change of the oscillator output which shows the Example of this invention. It is a figure which shows the optical spectrum which measured the output of the time division wavelength multiplexing pulse light source which shows the Example of this invention using the optical spectrum observer. It is a figure which shows the autocorrelation waveform of the soliton pulse which shows the Example of this invention. It is a block diagram of the 2 wavelength time division multiplexing multiwavelength pulsed light generation system which shows 2nd Example of this invention. It is FIG. (1) which shows the time division multiwavelength measuring system which has a time division wavelength multiplexing pulse light source which shows the Example of this invention. It is a figure which shows the signal processing system of the time division multiwavelength measuring system which shows the Example of this invention. It is a figure which shows the measurement result of the time division multiwavelength spectroscopy measurement with respect to the atom and molecule | numerator in the gas using the time division wavelength multiplexed pulse light which shows the Example of this invention. It is FIG. (2) which shows the multiwavelength spectroscopy measuring system which has a time division wavelength multiplexing pulse light source which shows the Example of this invention.

Explanation of symbols

1 Short pulse light source [fs (femtosecond) fiber laser]
2 Light intensity modulator (light characteristic adjuster)
3 Repetitive signal of pulsed light 4 Divider 5 Oscillator 7 Optical fiber 8, 12 Wavelength filter 11 Constant polarization optical fiber 13 Polarized light splitter 21 Object to be measured 22 Single receiver (photodiode)
23 Time Division Signal Processing Unit 24, 38, 44 Personal Computer 31 Photodiode 32, 42 Amplifier 33-36 Sample & Hold Circuit 37 Control Signal Generator 41 Diffraction Grating 43 Signal Processing Unit

Claims (9)

(A) a short pulse light source, an oscillator synchronized with the repetition frequency of the output of the short pulse light source, a light intensity modulator driven by the output of the oscillator and periodically changing the intensity of transmitted light with respect to time, An optical fiber that generates a soliton pulse whose wavelength is substantially linearly shifted with respect to the intensity of incident pulsed light from the light intensity modulator, and outputs pulsed light whose wavelength changes periodically with respect to time A split wavelength multiplexed pulse light source;
(B) an object to be measured for introducing short pulse light output from the pulse light source;
(C) A multi-wavelength measurement system having a time-division wavelength-multiplexed pulse light source, characterized by comprising a device for evaluating the measurement object.   The multi-wavelength measurement system having a time-division wavelength multiplex pulse light source according to claim 1, wherein the output light from the object to be measured is measured using a single light receiver, and the signal is measured in a time-division manner. A multi-wavelength measurement system having a time-division wavelength multiplex pulse light source.   2. A multi-wavelength measurement system having a time-division wavelength multiplex pulse light source according to claim 1, wherein output light from the object to be measured is separated according to wavelength and each signal is measured. Multi-wavelength measurement system with light source. (A) a short pulse light source, an oscillator synchronized with the repetition frequency of the output of the short pulse light source, a light intensity modulator driven by the output of the oscillator and periodically changing the intensity of transmitted light with respect to time, The optical intensity modulator comprises an optical fiber that generates a soliton pulse whose wavelength is substantially linearly shifted with respect to the intensity of incident pulsed light, and outputs pulsed light whose wavelength changes periodically with respect to time. A time-division wavelength multiplex pulse light source that is assembled into a portable type,
(B) an object to be measured for introducing short pulse light output from the pulse light source;
(C) A multi-wavelength measurement system having a time-division wavelength-multiplexed pulse light source, characterized by comprising a device for evaluating the measurement object.   The multi-wavelength measurement system having a time-division wavelength multiplex pulse light source according to claim 4, wherein the output light from the object to be measured is measured using a single light receiver, and the signal is measured in a time-division manner. A multi-wavelength measurement system having a time-division wavelength multiplex pulse light source.   5. A multi-wavelength measurement system having a time-division wavelength multiplex pulse light source according to claim 4, wherein output light from the object to be measured is separated according to wavelength and each signal is measured. Multi-wavelength measurement system with light source.   5. The multi-wavelength measurement system having a time-division wavelength multiplex pulse light source according to claim 1, wherein the short pulse light source is a femtosecond fiber laser.   5. A multi-wavelength measurement system having a time-division wavelength-multiplexed pulse light source according to claim 1, wherein the optical fiber is a polarization maintaining fiber.   9. A multi-wavelength measurement system having a time-division wavelength multiplex pulse light source according to claim 8, wherein the polarization direction of incident light is tilted from the birefringence axis of the constant polarization fiber, and pulses of two different wavelengths are generated simultaneously. A multi-wavelength measurement system having a time-division wavelength multiplex pulse light source.

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