JP2005069845A - Method and system of phase measurement of light pulse - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and system of phase measurement of light pulses for obtaining a plurality of short pulse lights by expanding a frequency region interference method to a plurality of light pulses to be measured. <P>SOLUTION: The system is provided with a spectrum measuring means 4 to which a pulse series with a certain time interval including a reference light pulse 2 and a plurality of light pulses to be measured #1 to #n-1 for measuring power spectrum of the pulse series, and a phase calculation means 5 for calculating the phase corresponding to the reference light pulse 2 of a plurality of the light pulses to be measured #1 to #n-1 from the power spectrum. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for measuring a phase of a plurality of short pulse lights by frequency domain interferometry, and in particular, in the fields of optical communication and optical signal processing, it is used for detecting and measuring the phase of an optical pulse. The present invention relates to a method and apparatus for measuring short-pulse light such as seconds and femtosecond pulses.

  Conventionally, frequency domain interferometry is a technique in which a reference optical pulse and a measured optical pulse are separated by a time τ and a spectrum that interferes in the frequency domain is measured to determine the phase of the measured optical pulse with respect to the reference optical pulse. (See Non-Patent Document 1 below).

  Since the optical carrier frequency is very high, it is very difficult to directly observe the waveform of the light wave. For this reason, phase measurement using the above-described interference is used, and one of them is frequency domain interferometry (Spectrum interferometry). The frequency domain interferometry utilizes a phenomenon in which pulses that are separated on the time axis overlap each other on the frequency axis to cause interference. Specifically, this is a method of calculating the relative phase of the measured optical pulse with respect to the reference optical pulse by combining the reference optical pulse and the measured optical pulse while shifting them by time τ and measuring the power spectrum.

  FIG. 11 is a block diagram of such a conventional optical pulse phase measuring apparatus.

In this figure, 101 is a timing adjusting means for inputting the measured light pulse 100, 103 is a multiplexing means for combining the output light of this timing adjusting means 101 and the reference light pulse 102, and 104 is this multiplexing means 103. The spectrum measuring means 105 to which the output light combined by the signal is input is a phase calculating means to which the output from the spectrum measuring means 104 is input. The phase calculating means 105 includes a Fourier transform unit 106 and a Fourier transform component. The extraction unit 107, the horizontal axis movement unit 108, the inverse Fourier transform unit 109, and the inverse tangent (tan ⁻¹ ) calculation unit 110 are provided.

Therefore, the timing adjusting unit 101 adjusts the time interval between the measured light pulse 100 and the reference light pulse 102 so as to have an appropriate value τ. These pulses are combined by the combining means 103, and the power spectrum is measured by the spectrum measuring means 104. In the phase calculation means 105, the measured power spectrum is Fourier-transformed by the Fourier transform unit 106, the Fourier transform component extraction unit 107 extracts the Fourier transform component corresponding to the time difference τ from the Fourier transform result, and the horizontal axis moving unit 108 The Fourier transform component is moved to the origin on the time axis, the component moved by the Fourier inverse transform unit 109 is subjected to Fourier inverse transform, and the inverse tangent (tan ⁻¹ ) calculation unit 110 performs the real part and the imaginary part of the Fourier inverse transform result. To calculate the arc tangent (tan ^-1 ) to obtain the phase.

  Details of the conventional frequency domain interferometry are shown below.

The time waveform of the electric field of the reference light pulse is e ₀ (t), and the time waveform of the electric field of the light pulse to be measured is e ₁ (t). When the measured light pulse is shifted by time τ and the two pulses are combined, the total electric field e (t) is

である。ｅ₀ （ｔ）のフーリエ変換をＥ₀ （ω），ｅ₁ （ｔ）のフーリエ変換をＥ₁ （ω）とすると、全パワースペクトルＩ（ω）は、

It is. When the Fourier transform of e ₀ (t) is E ₀ (ω) and the Fourier transform of e ₁ (t) is E ₁ (ω), the total power spectrum I (ω) is

で表される。Ｆはフーリエ変換を表す。ここで、Ｅ₀ （ω）のパワースペクトルをＩ₀ （ω）、位相を０（基準位相）、Ｅ₁ （ω）のパワースペクトルをＩ₁ （ω）、位相をφ₁ （ω）とすると、

It is represented by F represents a Fourier transform. Here, if the power spectrum of E ₀ (ω) is I ₀ (ω), the phase is 0 (reference phase), the power spectrum of E ₁ (ω) is I ₁ (ω), and the phase is φ ₁ (ω). ,

（７）式の第３項と第４項は、１つのパルスのパワースペクトルには見られない振動で、基準光パルスと被測定光パルスの周波数領域での干渉である。この干渉項に被測定光パルスの位相φ₁ が含まれているので、以下干渉項を抽出する方法を示す。ここで、

The third and fourth terms of equation (7) are vibrations that are not found in the power spectrum of one pulse, and are interference in the frequency domain of the reference light pulse and the measured light pulse. Since this interference term includes the phase φ _{1 of the} optical pulse to be measured, a method for extracting the interference term will be described below. here,

とおくと、Ｉ（ω）は、

I (ω) is

で表される。次にＩ（ω）をフーリエ変換する。周波数の関数であるＩ（ω）をフーリエ変換すると単位の上では時間の関数となる。

It is represented by Next, Fourier transform is performed on I (ω). When I (ω), which is a function of frequency, is Fourier transformed, it becomes a function of time in terms of units.

The frequency domain interferometry has the following features. First, the measurement system is simple because only power spectrum measurement is required. Further, since a non-linear phenomenon requiring a large optical power such as second harmonic generation is not used, the sensitivity is relatively high. Furthermore, the power spectrum may be measured with a short response time because the response speed of the light receiver or the electric circuit may be slow. In order to measure the power spectrum of a short pulse, it is necessary to measure a spectrum in a wide wavelength range, which can be easily realized with the current spectroscopic technology.
L. Lepetit, et al. , J .; Opt. Soc. Am. B, vol. 12, no. 12, pp. 2467-2474, 1995

  However, conventional frequency domain interferometry can only measure the phase of one pulse. If a plurality of pulses are measured, it is necessary to measure every pulse. Further, in the case of a pulse train in which a plurality of pulses are connected, it is necessary to separately extract and measure the pulses one by one. Further, in order to separate high-speed pulses, a high-speed modulator or the like is required, and there is a problem that it is expensive and complicated.

  In order to solve the above problems, the present invention extends the conventional frequency domain interferometry to a plurality of pulses, combines the reference light pulse and the plurality of light pulses to be measured with a time interval τ, and combines the power. By measuring the spectrum, the phase of a plurality of light pulses to be measured can be calculated in one measurement.

  That is, an object of the present invention is to provide an optical pulse phase measurement method and apparatus for obtaining the phases of a plurality of short pulse lights by extending the frequency domain interferometry to a plurality of optical pulses to be measured.

In order to achieve the above object, the present invention provides
[1] In the optical pulse phase measurement method, a spectrum measurement process for measuring a power spectrum in which a reference optical pulse and a plurality of measured optical pulses interfere with each other in light frequency regions positioned at different timings, A phase calculating step of calculating phases of a plurality of measured light pulses with respect to the reference light pulse.

  [2] In the optical pulse phase measurement method, a timing adjustment process for adjusting the reference light pulse and the plurality of measured light pulses at a constant time interval, and a combination of the reference light pulse and the plurality of measured light pulses. A wave process; a spectrum measurement process for measuring a power spectrum of the combined light; and a phase calculation process for calculating phases of the plurality of light pulses to be measured with respect to the reference light pulse from the power spectrum.

  [3] In the optical pulse phase measurement method according to [1] or [2], the phase calculation step includes a step of separating the power spectrum into a plurality of Fourier transform components, and the plurality of Fourier transform components from the plurality of Fourier transform components. Calculating a phase of a plurality of optical pulses to be measured.

  [4] In the optical pulse phase measurement method described in [1] or [2] above, the phase calculation process includes a process of Fourier transforming the power spectrum, and the Fourier transform result is converted into a plurality of components at regular time intervals. A process of separating, a process of moving each component on the time axis, a process of inversely transforming each of the moved components, and a phase of the plurality of optical pulses to be measured with respect to the reference light pulse from the result of the inverse Fourier transform The process of calculating.

  [5] In the optical pulse phase measurement method according to [1] or [2], the phase calculation process includes a process of multiplying the power spectrum by a sine wave and moving on a time axis, and a plurality of filters by a filter. A process of extracting a Fourier transform component and a process of calculating phases of the plurality of measured optical pulses from the plurality of Fourier transform components are included.

  [6] In the optical pulse phase measurement method described in [3], [4] or [5] above, the process of calculating the phases of the plurality of optical pulses to be measured from the Fourier transform component includes a plurality of optical signals to be measured. A step of setting an initial value of the phase of the pulse and repeatedly correcting the phase value of the plurality of measured optical pulses to obtain the phase of the plurality of measured optical pulses.

  [7] A pulse train having a constant time interval including a reference light pulse and a plurality of light pulses to be measured is input, spectrum measuring means for measuring a power spectrum of the pulse train, and the plurality of light pulses to be measured from the power spectrum. Phase calculating means for calculating a phase with respect to the reference light pulse.

  [8] In the optical pulse phase measurement apparatus, a timing adjustment unit that adjusts the reference light pulse and the plurality of measured light pulses at a constant time interval, and a combination of the reference light pulse and the plurality of measured light pulses. Wave measuring means; spectrum measuring means for measuring a power spectrum of the combined light; and phase calculating means for calculating a phase of the plurality of light pulses to be measured with respect to the reference light pulse from the power spectrum.

  [9] In the optical pulse phase measurement device according to [7] or [8], the phase calculation means includes means for separating the power spectrum into a plurality of Fourier transform components; Means for calculating the phase of a plurality of optical pulses to be measured.

  [10] In the optical pulse phase measurement apparatus according to [7] or [8], the phase calculation means includes means for Fourier transforming the power spectrum, and the Fourier transform result is converted into a plurality of components at regular time intervals. Means for separating, means for moving each component on the time axis, means for inversely transforming each moved component, and phase of the plurality of optical pulses to be measured with respect to the reference light pulse from the result of inverse Fourier transform Calculating means.

  [11] In the optical pulse phase measurement device according to [7] or [8], the phase calculation means includes a means for multiplying the power spectrum by a sine wave and moving on a time axis, and a filter. Means for extracting a Fourier transform component, and means for calculating the phase of the plurality of optical pulses to be measured from the plurality of Fourier transform components.

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

  (A) The phases of a plurality of light pulses can be measured collectively, and it is not necessary to separate the plurality of light pulses and measure them one by one.

  (B) The sensitivity is high with a simple configuration, and short pulses can be measured without depending on the speed of the light receiver.

  (C) When the present invention is applied to optical label recognition, a label can be recognized with a simple configuration.

  First, the principle of the present invention will be described.

N pulses are combined at a time interval τ, and the power spectrum is measured. If the Fourier transform of the i-th pulse electric field is E _i (ω), the power spectrum I (ω) is

ｋ＝ｉ₁ −ｉ₂ とおいて変形すると、

When deformed with k = i ₁ −i ₂ ,

Assuming that the intensity I _i (ω) of each pulse is equal, equation (15) can be simplified as follows.

これを解くと、パルス位相φ_i （ω）を求めることができる。

When this is solved, the pulse phase φ _i (ω) can be obtained.

  FIG. 1 is a block diagram of an optical pulse phase measuring apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of another embodiment of phase detecting means of the optical pulse phase measuring apparatus.

In this figure, 1-1 to ₁ -n _-1 are timing adjusting means, 2 is a reference light pulse, 3 is multiplexing means, 4 is spectrum measuring means, 5 is phase calculating means, and this phase calculating means 5 is A Fourier transform unit 6, a Fourier transform component extraction unit 7, a horizontal axis moving unit 8, a Fourier inverse transform unit 9, and a simultaneous equation solution calculation unit 10.

Therefore, the timing adjusting means 1-1 to ₁ -n- ₁ adjust the reference light pulse 2 and the n-1 measured light pulses # 1 to # n-1 so as to have an appropriate time interval τ. The timing adjusting units 1-1 to ₁ -n ₋₁ can be realized by a delay line (delay line) having a mechanically variable optical path length. These pulses are combined by combining means 3 such as an optical coupler or a beam splitter to form an optical pulse train in which each pulse is temporally connected. Here, the case where the reference light pulse 2 and the plurality of measured light pulses # 1 to # n-1 are separately shown is shown. However, when the input light is originally a pulse train, the timing adjusting means 1 and the combining means 3 are not necessary. It is.

  Next, the power spectrum of the optical pulse train is measured by the spectrum measuring means 4 such as an optical spectrum analyzer. The phase calculation means 5 includes a Fourier transform unit 6 that is a part that performs Fourier transform on the measured power spectrum, and a Fourier transform component extraction that is a part that extracts a plurality of Fourier transform components from the Fourier transform result at intervals corresponding to time τ. Unit 7, a horizontal axis moving unit 8 that is a stage for moving each Fourier transform component to the origin on the time axis, a Fourier inverse transform unit 9 that is a part that performs inverse Fourier transform on each of the moved components, and this Fourier inverse It consists of a calculation unit 10 for solving simultaneous equations, which is a part for solving the simultaneous supplementary formulation from the conversion result and obtaining the phase of the optical pulse to be measured. The specific configuration of the phase calculation means 5 of the optical pulse phase measuring device will be described later with reference to FIGS.

  Hereinafter, the procedure of the present invention will be described with reference to the drawings.

  FIG. 3 shows an example of a time waveform of an optical pulse train obtained by combining the reference optical pulse and the measured optical pulse. Here, the first pulse is a reference light pulse, and the remaining seven pulses are light pulses to be measured. The pulse width is 1 ps and the pulse interval τ is 6.25 ps. The pulse phase was a random value shown in FIG.

  The power spectrum of this optical pulse train is shown in FIG. When this power spectrum is Fourier-transformed, it becomes as shown in FIG. 6, and 15 peaks are obtained. Each peak has an interval of 6.25 ps corresponding to the time interval τ, and can be separated into each Fourier transform component at an interval of 6.25 ps. For example, when the fourth component is extracted from the center to the left side, it becomes as shown by the broken line in FIG. When this is moved to the origin on the time axis, a solid line in FIG. 7 is obtained. FIG. 8 shows the inverse Fourier transform of the moved component. In FIG. 8, the amplitude of the inverse Fourier transform result is plotted on a graph, but it is actually a complex number. This is performed in the same way for the first to seventh components from the center to the left in FIG. 6 to obtain seven inverse Fourier transform results and solve the simultaneous equations to calculate the phase of the optical pulse to be measured. . Here, the left component from the center of FIG. 6 is used, but the right component from the center may be used.

  The configuration of the phase calculation means is not limited to the above means, and the following configuration may be adopted.

  FIG. 2A shows the order of the Fourier transform component extraction unit 7 and the horizontal axis movement unit 8 shown in FIG. The broken line in FIG. 9 is obtained by moving the Fourier transform result in FIG. 6 by 25 ps on the time axis. From this, when the center 6.25 ps width is extracted, it becomes a solid line in FIG. 9, and it can be seen that the order is equivalent even if the order is changed.

  Further, the procedure of performing Fourier transform to extract some components and performing inverse Fourier transform can be replaced with a bandpass filter. The bandpass filter can also be realized by a digital filter operation. The procedure of Fourier transform, moving the horizontal axis, and performing inverse Fourier transform can be replaced with sine wave multiplication. Sine wave multiplication can also be realized by numerical calculation. Thus, it is possible to perform an operation equivalent to the procedure of the phase calculation means without performing Fourier transform. In the configuration of FIG. 2B, the Fourier transform component is first extracted by the band pass filter unit 11, and then the movement on the time axis is performed by multiplication of the sine wave by the multiplication unit 13. Here, 12 is a sine wave generator connected to the multiplier 13. In the configuration of FIG. 2C, the multiplication unit 13 is first moved on the time axis by multiplication of a sine wave, and the low-pass filter unit 15 is configured to extract a Fourier transform component. Here, since the movement on the time axis is the movement to the origin, the Fourier transform component after the movement on the time axis is extracted in the vicinity of the origin on the time axis. For this reason, the Fourier transform component is extracted by a low-pass filter. The extraction of the Fourier transform component and the movement on the time axis can be combined with a method using the Fourier transform and a method not using it.

  Next, the details of the phase measurement procedure of the optical pulse of the present invention will be described using mathematical expressions.

If the time waveform of the electric field of the i-th pulse is e _i (t) and the time interval of the pulse is τ, the total electric field e (t) composed of n pulses is

である。ｅ_i （ｔ）のフーリエ変換をＥ_i （ω）とすると、全パワースペクトルＩ（ω）は、

It is. If the Fourier transform of e _i (t) is E _i (ω), the total power spectrum I (ω) is

で表される。このＦはフーリエ変換を表す。ここで、ｉ番目のパルスのパワースペクトルをＩ_i （ω）、位相をφ_i （ω）とすると、

It is represented by This F represents a Fourier transform. Here, if the power spectrum of the i-th pulse is I _i (ω) and the phase is φ _i (ω),

となる。ｋ＝ｉ₁ −ｉ₂ とおいて変形すると、

It becomes. When deformed with k = i ₁ −i ₂ ,

となる。ここで、

It becomes. here,

とおくと、式（２３）は、

Then, equation (23) becomes

で表される。式（２５）のｋ＝０以外の項が周波数領域での干渉成分である。時間間隔τが大きくなると周波数軸上での振動が速くなり、スペクトル測定の分解能を越えるとパワースペクトルが正しく測定できなくなる。よって、式（２５）で表される振動がスペクトル測定の分解能を越えないように時間間隔τを設定する必要がある。また、後述のように時間間隔τはパルス幅よりも長くする必要があるので、この範囲内に時間間隔τを設定する必要がある。次にＩ（ω）のωを時間とみなしてフーリエ変換を行う。なお、Ｉ（ω）は実数のパワースペクトルである。周波数の関数であるＩ（ω）をフーリエ変換すると単位の上では時間の関数となるが、複素数のＥ（ω）をフーリエ逆変換してｅ（ｔ）を求めるのとは異なる。

It is represented by A term other than k = 0 in Equation (25) is an interference component in the frequency domain. When the time interval τ increases, the vibration on the frequency axis becomes faster, and when the spectrum measurement resolution is exceeded, the power spectrum cannot be measured correctly. Therefore, it is necessary to set the time interval τ so that the vibration represented by Expression (25) does not exceed the resolution of spectrum measurement. Further, since the time interval τ needs to be longer than the pulse width as will be described later, it is necessary to set the time interval τ within this range. Next, Fourier transform is performed by regarding ω of I (ω) as time. Note that I (ω) is a real power spectrum. When I (ω), which is a function of frequency, is Fourier-transformed, it becomes a function of time in terms of units, but is different from obtaining e (t) by Fourier-transforming a complex number E (ω).

  An application example of the present invention is shown in FIG.

  The input signal is an optical label 21 and a payload 22 modulated with data to be transmitted. It is necessary for the node to recognize the optical label 21 and drop it if it is data addressed to itself, otherwise pass it through and transfer it to another node. Here, the phase-modulated pulse train is referred to as an optical label 21. In the node, the wavelength that is the band pass filter 24 is selected and received by the light receiver 25 to control the through / drop of the optical switch 27. The holding circuit 26 holds the state of the optical switch 27 for the time of the payload 22. For example, the spectrum of label 1 has a peak at the wavelength of the bandpass filter 24 and the optical switch 27 is set to the drop side, but the label 2 has no peak at the wavelength of the bandpass filter 24. 27 is a through side. Reference numeral 23 is an optical coupler, and 28 is an optical fiber for timing adjustment.

  The optical pulse phase measurement method of the present invention is a method for obtaining a pulse phase from a power spectrum. By utilizing this, the peak of the optical spectrum can be changed by phase modulation of the pulse train of the label, and several labels can be created.

  Since it comprised as mentioned above, according to this invention, the phase of several optical pulses can be measured collectively, and it becomes unnecessary to isolate | separate several optical pulses and to measure one by one. As in the conventional frequency domain interferometry, the sensitivity is high with a simple configuration, and short pulses can be measured without depending on the speed of the light receiver.

  When the present invention is applied to optical label recognition, a label can be recognized with a simple configuration. Since the light receiver does not need to respond to individual pulses, a label composed of a high-speed pulse train can be recognized by a relatively low-speed light receiver. A complicated and inefficient setting such as lowering the bit rate of the optical label than the payload is also unnecessary.

  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 optical pulse phase measuring method and apparatus of the present invention are used for detecting and measuring the phase of an optical pulse in the field of optical communication and optical signal processing, and measuring short pulses such as picoseconds and femtosecond pulses. Suitable for

It is a block diagram of the optical pulse phase measuring apparatus showing an embodiment of the present invention. It is a block diagram of the other Example of the phase detection means of the phase measuring apparatus of the optical pulse of this invention. It is a figure which shows an example of the time waveform of the optical pulse train which combined the reference | standard optical pulse of this invention, and the to-be-measured optical pulse. It is a figure which shows the phase (Pulse # 0 is a reference | standard light pulse) of a reference | standard light pulse and a to-be-measured light pulse. It is a figure which shows the power spectrum of the optical pulse train containing a reference | standard optical pulse and a to-be-measured optical pulse. It is a figure which shows the Fourier-transform result (a horizontal axis is a unit of time) of the power spectrum which shows the Example of this invention. It is a figure which shows the extraction of the Fourier-transform component which shows the Example of this invention, and the movement to the origin on a time axis. It is a figure which shows the Fourier inverse transform result of the moved Fourier-transform component which shows the Example of this invention. It is the figure which moved on the time-axis the Fourier-transform result of the power spectrum which shows the Example of this invention. It is a figure which shows the application to the optical label recognition which shows the Example of this invention. It is a block diagram of the conventional phase measurement apparatus of an optical pulse.

Explanation of symbols

1-1 to ₁ -n- ₁ timing adjusting means 2 reference light pulse 3 combining means 4 spectrum measuring means 5 phase calculating means 6 Fourier transform unit 7 Fourier transform component extracting unit 8 horizontal axis moving unit 9 Fourier inverse transform unit 10 simultaneous Calculation unit for equation solution 11 Bandpass filter unit 12 Sine wave generation unit 13 Multiplying unit 15 Lowpass filter unit 21 Optical label 22 Payload modulated with data to be transmitted 23 Optical coupler 24 Bandpass filter 25 Light receiver 26 Retention circuit 27 Optical switch 28 Optical fiber for timing adjustment

Claims (11)

(A) a spectrum measurement process for measuring a power spectrum in which a reference light pulse and a plurality of light pulses to be measured interfere with each other in the frequency domain of light positioned at different timings;
(B) a phase calculation process for calculating a phase of the plurality of optical pulses to be measured with respect to the reference optical pulse from the power spectrum. (A) a timing adjustment process for adjusting the reference light pulse and the plurality of light pulses to be measured at fixed time intervals;
(B) a multiplexing process for combining the reference light pulse and the plurality of light pulses to be measured;
(C) a spectrum measurement process for measuring a power spectrum of the combined light;
(D) a phase calculation process for calculating a phase of the plurality of optical pulses to be measured with respect to the reference optical pulse from the power spectrum.   3. The optical pulse phase measurement method according to claim 1, wherein the phase calculation step includes a step of separating the power spectrum into a plurality of Fourier transform components, and the plurality of optical pulses to be measured from the plurality of Fourier transform components. A method for measuring the phase of an optical pulse, comprising: calculating a phase of the optical pulse.   3. The optical pulse phase measurement method according to claim 1, wherein the phase calculation step includes a step of Fourier transforming the power spectrum, a step of separating the Fourier transform result into a plurality of components at regular time intervals, and A process of moving the components on the time axis, a process of Fourier transforming each moved component, and a process of calculating the phase of the plurality of optical pulses to be measured with respect to the reference light pulse from the Fourier transform result. A method for measuring a phase of an optical pulse, comprising:   3. The optical pulse phase measurement method according to claim 1, wherein the phase calculation step includes a step of multiplying the power spectrum by a sine wave and moving on a time axis, and extracting a plurality of Fourier transform components by a filter. And a phase calculating method for calculating the phase of the plurality of optical pulses to be measured from the plurality of Fourier transform components.   6. The optical pulse phase measuring method according to claim 3, wherein the step of calculating the phase of the plurality of measured optical pulses from the Fourier transform component sets an initial value of the phase of the plurality of measured optical pulses. A phase measurement method for an optical pulse comprising the step of repeatedly correcting the phase values of the plurality of optical pulses to be measured to obtain the phases of the plurality of optical pulses to be measured. (A) a spectrum measuring means for inputting a pulse train having a constant time interval including a reference light pulse and a plurality of light pulses to be measured, and measuring a power spectrum of the pulse train;
(B) An optical pulse phase measuring device comprising phase calculating means for calculating a phase of the plurality of optical pulses to be measured with respect to the reference optical pulse from the power spectrum. (A) timing adjusting means for adjusting the reference light pulse and the plurality of light pulses to be measured at fixed time intervals;
(B) multiplexing means for multiplexing the reference light pulse and the plurality of measured light pulses;
(C) spectrum measuring means for measuring a power spectrum of the combined light;
(D) An optical pulse phase measuring device comprising phase calculating means for calculating a phase of the plurality of optical pulses to be measured with respect to the reference optical pulse from the power spectrum.   9. The optical pulse phase measuring apparatus according to claim 7 or 8, wherein the phase calculating means separates the power spectrum into a plurality of Fourier transform components, and the plurality of measured optical pulses from the plurality of Fourier transform components. And a means for calculating the phase of the optical pulse.   9. The optical pulse phase measuring apparatus according to claim 7 or 8, wherein said phase calculating means includes means for Fourier transforming said power spectrum, means for separating said Fourier transform result into a plurality of components at regular time intervals, and Means for moving the components on the time axis, means for inversely transforming each of the moved components, and means for calculating the phase of the plurality of optical pulses to be measured with respect to the reference light pulse from the inverse Fourier transform result An optical pulse phase measuring device comprising:   9. The optical pulse phase measuring apparatus according to claim 7 or 8, wherein said phase calculating means extracts a plurality of Fourier transform components by means for multiplying said power spectrum by a sine wave and moving on a time axis, and a filter. And a means for calculating the phase of the plurality of optical pulses to be measured from the plurality of Fourier transform components.

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