JP2001156368A - Time-division wavelength multiple pulse-light generator and multiple wavelength measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a time-division wavelength multiple pulse-light generator capable of changing multiple ultrashort pulse light having different wavelengths in an arbitrary time-division period extending over a wide band at high speed, by adding an oscillator synchronizing with an output from a short-pulse light source to the short-pulse light source, a light intensity adjustor and an optical fiber, and driving the light intensity adjustor by an output from the oscillator and a multiple wavelength measuring system. SOLUTION: The time-division wavelength multiple pulse-light generator has the short-pulse light source 1, the oscillator 5 synchronizing with the repetitive frequency of an output from the short-pulse light source 1, an intensity modulator 2 being driven by the output from the oscillator 5 and modulating the output from the short-pulse light source 1 and the optical fiber 7, to which incident pulses are projected from the intensity modulator 2 and which changes the wavelength of output pulses, and pulse light in which wavelengths are changed periodically to the time is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-division wavelength for generating an ultrashort pulse in which the wavelength of light periodically changes with time using a single ultrashort pulse light source, an optical intensity modulator, and an optical fiber. The present invention relates to a multi-pulse light generator and a multi-wavelength measurement system.

[0002]

2. Description of the Related Art Heretofore, ultrashort pulse light has been generated using a dye laser or a solid-state laser. However, the optical system is large and complicated, and the wavelength variable range is as narrow as tens of nm. Met.

[0003]

In the conventional variable wavelength light source, since the wavelength is changed by rotating optical components such as mirrors mechanically, the wavelength cannot be changed at high speed. Was a big deal.

Although light whose wavelength is tunable by a wavelength tunable light source or the like can be periodically output, soliton pulses having different wavelengths cannot be output periodically at substantially the same time.

In the present invention, an oscillator synchronized with the output of the short pulse light source is added to the short pulse light source, the light intensity adjuster, and the optical fiber, and the light intensity adjuster is driven by the output of the oscillator. It is an object of the present invention to provide a time division multiplexed pulsed light generator and a multi-wavelength measurement system capable of changing multiplexed ultrashort pulsed light having different wavelengths at an arbitrary time division period over a wide band at high speed. And

[0006]

According to the present invention, in order to achieve the above object, [1] a time-division multiplexed pulsed light generating apparatus, wherein a short pulse light source and a repetition frequency of an output of the short pulse light source are synchronized. An oscillator, an optical fiber driven by the output of the oscillator, for modulating the output from the short pulse light source, and an optical fiber that receives an incident pulse from the optical property adjuster and changes the wavelength of the output pulse. And outputting pulsed light whose wavelength periodically changes with time.

[2] In the time-division multiplexed pulse light generator according to [1], the optical characteristic adjuster is an optical intensity modulator.

[3] In the time-division multiplexed pulse light generator according to [1], the short pulse light source is a femtosecond fiber laser.

[4] The time-division multiplexed pulsed light generator according to [1], wherein the optical fiber is a constant polarization fiber.

[5] In the time-division multiplexed pulsed light generator according to [4], the polarization direction of the incident light is inclined from the birefringence axis of the constant polarization fiber, and pulses of two different wavelengths are simultaneously generated. Features.

[6] In a time-division WDM pulsed light generator, a short pulse light source, an oscillator synchronized with a repetition frequency of an output of the short pulse light source, and an output from the short pulse light source driven by the oscillator output And an optical fiber that changes the wavelength of an output pulse while receiving an incident pulse from the optical property adjuster, and outputs pulse light whose wavelength periodically changes with time. It is characterized by being assembled in a portable type.

[7] The time-division multiplexed pulse light generator according to the above [6], wherein the optical characteristic adjuster is an optical intensity modulator.

[8] The time-division multiplexed pulse light generator according to [6], wherein the short pulse light source is a femtosecond fiber laser.

[0014]

[9] The time-division multiplexed pulse light generator according to [6], wherein the optical fiber is a constant polarization fiber.

[10] The above

[9] The time-division multiplexed pulse light generating apparatus described in [9], characterized in that the polarization direction of the incident light is inclined from the birefringent axis of the constant polarization fiber, and pulses of two different wavelengths are simultaneously generated.

[11] In a multi-wavelength measurement system, a time-division multiplexed short pulse light source, an object to be measured into which short pulse light output from the pulse light source is introduced, and an apparatus for evaluating the object to be measured are described. It is characterized by having.

[12] The multi-wavelength measurement system according to the above [11], wherein the output light from the object to be measured is measured using one light receiver, and the signal is measured in a time-division manner. .

[13] In the multi-wavelength measurement system according to the above [11], the output light from the object to be measured is separated by wavelength and each signal is measured.

With the configuration described above, (A) it is possible to output ultrashort pulse light whose wavelength changes rapidly from a single fiber. (B) The wavelength of the pulse light can be periodically varied with time over a wide band. (C) A compact system can output ideal soliton pulses over a wide band.

[0020]

Embodiments of the present invention will be described below in detail.

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

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

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

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

As is apparent from this figure, beautiful soliton pulses (wavelengths 1 to 4) whose wavelengths are periodically changed are repeatedly output at regular intervals.

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

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

The output of the oscillator 5 causes the light intensity modulator 2
, 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, a soliton pulse whose wavelength changes to a sawtooth wave, and a signal which changes stepwise, as shown in 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
A fiber laser) 1, an oscillator 5 synchronized with the repetition frequency of the output of the short pulse light source 1, an optical intensity modulator 2 driven by the output of the oscillator 5, and modulating the output from the short pulse light source 1. An optical fiber 7 that changes the wavelength of an output pulse while receiving an incident pulse from the light intensity modulator 2 is provided, and outputs pulsed light whose wavelength periodically changes with time.

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 birefringent axis of the constant polarization optical fiber so that pulses of two different wavelengths are generated at the same time.

Further, a short pulse light source (fs fiber laser) 1, an oscillator 5 synchronized with a repetition frequency of the output of the short pulse light source 1, and an output from the short pulse light source 1 driven by the output of the oscillator 5 A light intensity modulator 2 that modulates the wavelength of light, and an optical fiber 7 that receives an incident pulse from the light intensity modulator 2 and changes the wavelength of an output pulse. It outputs light and is assembled into a portable type.

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

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

FIG. 4 is a diagram showing an optical spectrum obtained by measuring the output of the time division multiplexed 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 a pulse light whose wavelength periodically changes at a high speed is output to the output, the spectrum observer simultaneously observes a multi-wavelength spectrum. The spectral wavelength is a beautiful sech2 type. In the figure, when the optical fiber length is 220 m, 1.56 μm, 1.625 μm,
At four wavelengths of 1.675 μm and 1.725 μm, time division WDM pulsed light is generated. Up to now, wavelength shifts of up to 1.56 to 2.03 μm have been observed.

FIG. 5 is a diagram showing an autocorrelation waveform of a soliton pulse according to 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 is 220 m, the time width of the autocorrelation waveform is 430 f
s. At this time, the width of the time waveform is estimated to be 280 fs.

FIG. 6 is a configuration 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 on the birefringent axis of the constant polarization optical fiber 11 with the polarization direction inclined, the two polarization components simultaneously generate soliton pulses at the same time, so that a soliton pulse of two wavelengths can be obtained at the output. . By combining this technique with the technique of modulating the light intensity modulator using an oscillator, the wavelength of the time-division multiplexed pulse light can be further doubled. Here, 12 is a wavelength filter,
Reference numeral 13 denotes a polarized light splitter. In the polarized light splitter 13, two polarization components can be separated.

Next, a description will be given of a multi-wavelength measurement system using the above-described time-division multiplex short pulse light.

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

As shown in this figure, using the time-division multiplexed pulse light source A shown in FIG. 1, the change of the transmittance and the reflectance of the measured object 21 at multiple wavelengths can be measured by a single light receiver ( A time-division signal processing unit 2 using a photodiode
3 and the personal computer 24 to measure in a time sharing manner. After the signal received by the photodiode 22 is amplified, the signal is time-divided and processed by the time-division signal processing unit 23, and measurement is performed for each wavelength.

FIG. 8 is a diagram showing a signal processing system of a time-division multi-wavelength measuring system according to 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, the time-division multiplexed pulse light is received by the photodiode 31 and amplified by the amplifier 32. In addition, sample &
A signal for controlling the hold circuits 33 to 36 is generated in the control signal generator 37. When the pulse light of wavelength 1 is received, the signal is held by the sample & hold circuit 33 (circuit 1). When the pulse light is received, the signal is held by the sample & hold circuit 34 (circuit 2). After holding the signals of the respective wavelengths by the sample and hold circuit in this manner, the personal computer 38
And simultaneously measure signals of each wavelength.

FIG. 9 is a diagram showing the results of time-division multi-wavelength spectroscopy of atoms and molecules in a gas using time-division multiplexed pulsed 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 each atom / molecule density.

As is apparent from this figure, a change in the transmitted light intensity of the medium with respect to a change in time can be measured simultaneously at multiple wavelengths. Until now, such multi-wavelength spectral measurement could not be performed by a single optical system.

FIG. 10 is a diagram (part 2) illustrating a multi-wavelength spectrometry system using a time-division multiplexed 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 will be omitted.

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

As described above, according to the present invention, (1) the measurement using the ultrashort pulse light of multiple wavelengths can be simultaneously performed in a single system by time division. (2) Multi-wavelength measurement using ultrashort pulse light can be performed in a wide band with a compact system. (3) An ideal soliton pulse can be generated.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0053]

As described above, according to the present invention, the following effects can be obtained.

(A) In the time division wavelength multiplexed pulse light generator (light source), the wavelength of light changes depending on the intensity of the light. Therefore, the wavelength of the ultrashort pulse light is modulated by modulating the intensity of the light. It can be changed at high speed over a wide band.

The generated pulse light is an ideal soliton pulse.

(B) By using the time-division multiplexed pulsed light generator (light source) of the present invention, it becomes possible to perform a spectral measurement and a wavelength-dependent optical measurement in a simple system at high speed.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a soliton pulse of a time division multiplexed light source according to an embodiment of the present invention.

FIG. 3 is a diagram showing a time change of an oscillator output and a time change of a wavelength of a soliton pulse accompanying the change with time according to the embodiment of the present invention.

FIG. 4 is a diagram showing an optical spectrum obtained by measuring the output of the time division multiplexed pulse light source according to the embodiment of the present invention using an optical spectrum observer.

FIG. 5 is a diagram showing an autocorrelation waveform of a soliton pulse according to the embodiment of the present invention.

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

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

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

FIG. 9 is a diagram illustrating measurement results of time-division multi-wavelength spectrometry for atoms and molecules in a gas using time-division multiplexed pulsed light according to an embodiment of the present invention.

FIG. 10 is a diagram (part 2) illustrating a multi-wavelength spectroscopy measurement system using a time-division multiplexed pulse light source according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Short pulse light source [fs (femtosecond) fiber laser] 2 Optical intensity modulator (optical characteristic adjuster) 3 Repetition signal of pulse light 4 Divider 5 Oscillator 7 Optical fiber 8, 12 Wavelength filter 11 Constant polarization optical fiber 13 Polarized light splitter 21 Object under test 22 Single photodetector (photodiode) 23 Time-division signal processing unit 24, 38, 44 Personal computer 31 Photodiode 32, 42 Amplifier 33-36 Sample and hold circuit 37 Control signal generation Device 41 diffraction grating 43 signal processing unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G059 AA05 EE11 GG01 GG06 GG08 GG09 JJ02 JJ05 JJ17 KK01 5F072 AK06 JJ01 JJ20 KK30 QQ01 RR01 SS07 SS08 YY11 5K002 AA01 DA02 DA31 FA01

Claims (13)

[Claims] (A) a short pulse light source; and (b) an oscillator synchronized with a repetition frequency of an output of the short pulse light source.
(C) an optical characteristic adjuster driven by the oscillator output and modulating the output from the short pulse light source; and (d) an incident pulse is incident from the optical characteristic adjuster and changes the wavelength of the output pulse. (E) comprising an optical fiber;
A time-division multiplexed pulsed light generator, which outputs pulsed light whose wavelength periodically changes with time. 2. The time-division multiplexed pulsed light generator according to claim 1, wherein said optical characteristic adjuster is an optical intensity modulator. 3. The time-division multiplexed pulsed light generator according to claim 1, wherein said short pulse light source is a femtosecond fiber laser. 4. The time-division multiplexed pulsed light generator according to claim 1, wherein said optical fiber is a constant polarization fiber. 5. The time-division multiplexed pulse light generating apparatus according to claim 4, wherein the polarization direction of the incident light is inclined from the birefringence axis of the constant polarization fiber, and two different wavelength pulses are simultaneously generated. Time division multiplexed pulsed light generator. 6. A short pulse light source, and (b) an oscillator synchronized with a repetition frequency of an output of the short pulse light source.
(C) an optical characteristic adjuster driven by the oscillator output and modulating the output from the short pulse light source; and (d) an incident pulse is incident from the optical characteristic adjuster and changes the wavelength of the output pulse. (E) a time-division multiplexed pulsed light generation device characterized in that the device outputs (e) pulsed light whose wavelength periodically changes with time and is assembled in a portable manner. 7. The time-division wavelength-division multiplexed pulsed light generator according to claim 6, wherein said optical characteristic adjuster is an optical intensity modulator. 8. The time division multiplexed pulse light generator according to claim 6, wherein the short pulse light source is a femtosecond fiber laser. 9. The time division multiplexed pulsed light generator according to claim 6, wherein said optical fiber is a constant polarization fiber. 10. The time-division multiplexed pulse light generating apparatus according to claim 9, wherein the polarization direction of the incident light is inclined from the birefringent axis of the constant polarization fiber, and pulses of two different wavelengths are generated at the same time. Time division multiplexed pulsed light generator. (A) a time-division WDM short pulse light source;
A multi-wavelength measurement system comprising: (b) an object to be measured into which short-pulse light output from the pulse light source is introduced; and (c) a device for evaluating the object to be measured. 12. The multi-wavelength measurement system according to claim 11, wherein the output light from the object to be measured is measured using one light receiver, and the signal is measured in a time-division manner. Measurement system. 13. The multi-wavelength measurement system according to claim 11, wherein output light from the object to be measured is separated according to wavelength, and respective signals are measured.