JPH01302126A - Light pulse measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain the direction of the time axis of the waveform of a light pulse to be measured, by measuring the autocorrelation waveforms of the light pulse to be measured with respec to both of a state wherein a medium whose wavelength dispersion characteristic is known is inserted in a light path and a state wherein said medium is not inserted. CONSTITUTION:The Fourier transform fE(omega) of the complex amplitude E(t) of the electric field of a light pulse L to be measured is measured according to the known method using a waveform memory device 17 ad a computer 18. The Fourier transform fE'(omega) of the electric field E'(t) of a light pulse when a medium 31 whose wavelength dispersion characteristic T(omega) is inserted in the light path of the light pulse L to be measured is also measured in the same way. By utilizing that there is the relation of phi'(omega)=phi(omega)+theta(omega) between phases phi(omega), phi'(omega) and theta(omega) of fE, fE', and T, the codes (positive or negative) of phi, phi' indifinite in a conventional measuring method, that is, the time axial directions of E, E' are determined. When the instantaneous frequency change (charp) of the light pulse is linear, the time axis directions of E, E' can be also determined from the change in the time width of the light pulse caused by the presence of the medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is utilized for measuring the light emission characteristics, transmission characteristics, and other optical characteristics of optical elements. In particular, the wavelength of light in the pulse waveform and each part of the pulse, or the frequency equivalent to the wavelength,
Light for detailed measurement of the intensity waveform and phase waveform corresponding to the integral of the instantaneous frequency change for short optical pulses that change rapidly over a very short time width that is comparable to or less than the response time of existing photodetectors; This invention relates to a pulse measuring device.

[Conventional technology]

Characteristics of optical elements used in optical communication, optical measurement, optical signal processing, and other devices that utilize optical pulses, such as output characteristics of light emitting elements and optical amplification elements, output characteristics of predecessor output elements, and transmission characteristics of filters. In order to measure other things, it is necessary to know in detail the waveform of the optical pulse and the wavelength of the light at each part of the pulse. However, in order to improve measurement accuracy, short optical pulses with extremely short time widths are required.
A device is needed to measure it.

The present applicant has developed the following research into the intensity waveform and instantaneous frequency of short optical pulses in which the pulse waveform and the wavelength of light in each part of the pulse change rapidly over a very short time width that is comparable to or less than the response time of existing photodetectors. We have already filed a patent application (Japanese Patent Application No. 62-73547, hereinafter referred to as the "prior application") for a method for measuring in detail the phase waveform corresponding to the integral of change. This method splits the optical pulse beam to be measured into two beams, gives a relative optical path length difference to the optical paths of these two beams, combines these two beams, and divides the combined beam into two beams. A nonlinear crystal having the ability to generate harmonics is made to coaxially enter a live beam to generate second harmonic light, and the intensity of the combined light of the two light beams that passed through the nonlinear crystal and the second harmonic light is adjusted to that intensity. The intensity of the optical pulse to be measured is determined by converting it into a proportional electrical signal, recording the intensity change of the combined light and second harmonic light with respect to the change in the relative optical path length difference, and performing Fourier transform of the recorded measurement value. The waveform and phase waveform are calculated.

FIG. 5 is a block diagram of an apparatus for carrying out this method.

Beam splitter 1, fixed prism 2 and moving stage 4
The movable prism 3 attached to constitutes a Michelson interferometer. The optical pulse L to be measured is branched from a beam splitter 1, reflected by a fixed prism 2 and a movable prism 3, multiplexed by a beam splitter 1, and passed through a lens 5 to a nonlinear beam having the ability to generate second harmonics. The light is coaxially incident on the crystal 7. The difference in optical path length between the two beams split by the beam splitter 1 can be changed by moving the movable prism 3.

The light that has passed through the nonlinear crystal 7 is composed of second harmonic light and light that has not been converted into second harmonic (hereinafter referred to as "fundamental wave light").
including. These lights enter the beam splitter 24 through the lens 6, where they are separated into second-order harmonic light and fundamental wave light, and each wavelength (frequency) component is selected by an optical filter 8.30 and photodetected. 9.28. The detection outputs of the photodetectors 9.28 are respectively amplified by preamplifiers 10.29 and output as voltages proportional to the second harmonic light intensity and the fundamental wave light intensity. This output is stored in the waveform storage device 17.

To record the intensities of the fundamental wave light and the second harmonic light with respect to relative optical path length differences at appropriate intervals, a light source 11 that generates continuous light with a pure wavelength, such as a continuous wave He--Ne laser, is used. The light from the light source 11 enters the Michelson interferometer via the reflecting mirror 12, and similarly to the optical pulse L to be measured, it is divided into two parts, given a relative optical path length difference, and then combined. At this time, a 178 wavelength plate 1 is placed on one of the two optical paths.
9 is inserted, and the combined light beam is separated by a polarizing beam splitter 20 and incident on photodetectors 21 and 22. The photodetectors 21, 22 receive signals that vary sinusoidally with the interference fringe period as the relative optical path length difference changes.

Therefore, if a trigger signal is generated from the trigger signal generation circuit 23 every time the phase of the signal becomes 0, π/2, etc., the relative Optical path length difference can be calibrated.

The output voltage value of the preamplifier 10 is: 1 + 2 cz(r)+4Re CF+(r) e
xp (i (tlo r)) ten Re [' 7 (r)
exp(2i (11or) :1(1) where G2(τ) is the second-order intensity autocorrelation waveform, F2
(τ) represents the second harmonic optical electric field autocorrelation waveform, τ represents the delay time difference (the value obtained by dividing the relative optical path length difference by the high speed), and ω. =2πC/λ. , C is the speed of light, λ. is the center angular frequency of the optical pulse to be measured. Also, l is an imaginary unit, Re
represents the real part of a complex number.

Further, the output voltage value of the preamplifier 29 is 1+Re(G+
(r)'exp(ia+of)--proportional to (2). G+(τ) is an electric field autocorrelation waveform.

The computer 18 stores the second-order intensity autocorrelation waveform G2(τ), the second-order harmonic optical electric field autocorrelation waveform F2(τ), and the electric field autocorrelation waveform G, (τ
) to analyze the pulse waveform.

Here, the Fourier transform of these three autocorrelation waveforms will be explained. Expressing the Fourier transform as F, T, and D, F, T, Cc+(r) E = l E-+ 2-
- (3) F, T, [G2(r))=lI(co)l”
−−−−(4) F, T, (Fz(r) 〕=
l uh) l 2--- (5). Here, E■ is the Fourier transform of the complex amplitude E (t) of the optical pulse electric field, ■- is the Fourier transform of the optical pulse intensity 1 (t),
U(to) is the Fourier transform of the complex amplitude u (t) of the second harmonic optical electric field. Between the complex amplitude E (t), the optical pulse intensity 1 (t), and the complex amplitude u (t), I (t)
= l E(t) l 2, u(t) = E(t)”
--The relationship (6) holds true. E((IJ),' I
Since − and U− are generally complex numbers, using the absolute value and phase, respectively, E(a+)= l EM l exp(iφ−) (7)
1(A= l Ih) lexp(i z(ti)) )
−(8) u(u)= l u(n l e)jp
It is expressed as (iψ(u>) ・(9).

Therefore, if E■ is found, E
(t) is obtained, the intensity waveform is obtained by the absolute value of E (t), and the phase waveform is obtained by the phase of E (t).

E ■'s absolute 1i! 1E ((13) For l, (3)
As shown in the formula, it is obtained by Fourier transforming the measured value of G + (r). Therefore, it is necessary to find the phase φ■ included in equation (7).

In the method of the previous application, IE-1, 1I-1 and 1
The intensity waveform and phase waveform of the optical pulse to be measured were obtained by calculating u■1 and repeatedly calculating their phase φ), χ- and ψ- so as to satisfy the relationship of equation (6). .

Furthermore, a method of measuring the second-order intensity autocorrelation waveform G2(τ) and the spectrum 1Eldl has been widely known. Examples of such a measuring method include (1) Japanese Patent Application No. 1983-24993. , ``Optical pulse measurement method'' (2) ``Nobel method of uniform evaluation of altrashort
"Optical Pulseize", Altrafast Phenomina (Sbringa Belag, New York 198
4th year) page 93 (“Novel Method of
Waveform Evaluation ofLll
trashort 0ptical Pulses”,
in Ultrafast Phenomena IV
(Springer-Verlag, New Yo
rk1984), pp93). Method (1) is a method that combines the measurement of the second-order intensity autocorrelation waveform G2(τ) using a Michelson interferometer and the measurement of the spectra lfJ+)l" and 1u-1 using a spectrometer. , (2) is a method that combines the measurement of G 2 (τ) using a Michelson interferometer and the measurement of IE(u)l'' using a spectrometer.

[Problem that the invention seeks to solve]

However, the conventional optical pulse measurement method has a drawback that it is not possible to determine the time axis direction of the intensity waveform and phase waveform obtained by calculation. That is, a pulse waveform obtained by time-reversing the obtained pulse waveform may also be a true pulse waveform with exactly the same probability.

Therefore, it is not possible to determine which of the two pulse waveforms is the waveform of the optical pulse to be measured.

To explain using the example of the prior application method, if we replace χ−→−χ− ψ■→−ψ− to state→−φ for all ω, as a result, the optical pulse electric field in the time domain complex amplitude E (t), optical pulse intensity 1
(t) and the complex amplitude of the second-order, harmonic optical electric field u (t
) is replaced by E (t)→E '' (-t) 1 (t) → I (-t) u (t) → u '' (-t). Here, the symbol 0 represents a complex conjugate number. Regarding the optical pulse intensity I (t), this is a real number and remains unchanged even when complex conjugate is taken.

These replaced values also always satisfy the relationship in equation (6). That is, if we replace t with -t in equation (6) and take the conjugate complex numbers on both sides, we get 1 (-t) =
l E(-t) l "u"(-t) = E"(-
t) becomes 2.

Therefore, IE-1, l IvJl and 1ull or their equivalent G+(τ), G2(τ) right and F
, (τ), and when E(t) is obtained as one solution, E''(-t), which is time-reversed, is also a solution.

These values have different signs of phase in frequency space.

The problem is that -order measured quantities G, (γ), G2(r
), and F2(τ) are all symmetrical with respect to the delay time τ.

Also, IE-1, ll-1 and 1ull are each C
Since it is a Fourier transform of The above-mentioned problems also occur in the pulse measurement method.

Conventionally, two methods have been considered to solve this problem.

The first method is to measure third-order or higher-order intensity autocorrelation waveforms. A third-order or higher-order intensity autocorrelation waveform has a property of being asymmetric with respect to the delay time difference τ when the optical pulse is asymmetric. Since the asymmetry is directly reflected in the correlation waveform, the waveform of the optical pulse including the direction of the time axis can be easily determined. To measure third-order or higher-order intensity correlation waveforms, it is necessary to utilize third-order or higher-order optical nonlinear effects. However, such optical nonlinear effects are generally much smaller than second harmonic generation due to second order optical nonlinear effects, and their signals are much weaker. Therefore, this method can only be used when the optical intensity of the optical pulse to be measured is particularly high (instantaneous intensity of about IIV or higher).

The second method is to use a light pulse whose time width is sufficiently narrow compared to the light pulse to be measured and which is temporally synchronized with the light pulse to be measured, that is, a gate pulse. In this method, the intensity cross-correlation waveform between the gate pulse and the optical pulse to be measured is measured. This is called sampling, and is similar to the sampling measurement of electrical pulses.
The waveform of the optical pulse to be measured can be determined, including the direction of the time axis. However, the gate pulse can be used only when the time width of the pulse to be measured is equal to or greater than loPS, and measurement becomes difficult when the time width is less than loPS.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide an optical pulse measuring device that measures the waveform of an optical pulse including the direction of the time axis.

[Means for solving problems]

The optical pulse measuring device of the present invention includes a means for measuring an autocorrelation waveform in a state in which a medium with known wavelength dispersion characteristics is inserted into the incident optical path of the optical pulse to be measured, and in a state in which this medium is not inserted. , means for determining the direction of the time axis of the waveform of the optical pulse to be measured from the two autocorrelation waveforms.

[For production]

When a medium is inserted into the incident optical path of the optical pulse to be measured, the time width of the pulse waveform to be measured changes depending on the sign of the group velocity dispersion of the medium. Therefore, the time axis of the pulse waveform can be determined from this change. Furthermore, the time axis of the pulse waveform can also be determined based on changes in the phase component of Fourier transform caused by the wavelength dispersion characteristics of the medium.

〔Example〕

FIG. 1 is a block diagram of an optical pulse measuring device according to an embodiment of the present invention.

This device includes a dispersion medium 31 with known wavelength dispersion characteristics, a switch 32 for selectively inserting the dispersion medium 31 into the incident optical path of the optical pulse L to be measured, and a state in which the dispersion medium 31 is inserted and a state in which the dispersion medium 31 is not inserted. and an optical pulse measuring device 33 that measures the waveform of the optical pulse L to be measured for each state in which the optical pulse is not present.

In this embodiment, the device shown in the specification and drawings of the aforementioned prior application is used as the optical pulse measuring device 33. That is, the optical pulse measuring device 33 includes a beam splitter 1, a fixed prism 2, a movable prism 3, a movable stage 4, a lens 5.6,
nonlinear crystal 7, beam splitter 24, optical filter 8.30, photodetector 9.28, preamplifier 10.29,
Light source 11, reflector 12, waveform storage device 17, wavelength plate 19, polarizing beam splitter 20, photodetector 21.
22 and a trigger signal generator 23, and a calculation means, that is, a computer 18, for calculating the intensity waveform and phase waveform of the optical pulse to be measured from the output of the measurement means.

The optical pulse measuring device 33 also measures autocorrelation waveforms under the control of the computer 18 in a state in which the dispersion medium 31 is inserted into the incident optical path of the optical pulse to be measured and in a state in which the dispersion medium 31 is not inserted. and means to do so. The computer 18 also includes means for determining the direction of the time axis of the waveform of the optical pulse to be measured from the two autocorrelation waveforms.

At the time of measurement, first, the dispersion medium 31 is removed from the optical path of the optical pulse L to be measured by the switch 32, and in this state,
A first measurement is performed using the optical pulse measuring device 33. continue,
The dispersion medium 31 is inserted onto the optical path of the optical pulse L to be measured by the switch 32, and in this state, a second measurement is performed by the optical pulse measuring device 33.

These two measurements yield the intensity waveform and phase waveform of the optical pulse, respectively. The time axis direction of these waveforms is not determined. Therefore, the time axis of the pulse waveform is determined from the dispersion characteristics of the dispersion medium 31.

Here, the Fourier transform of the optical pulse electric field E (t) in a state where the dispersion medium 31 is not inserted on the optical path is expressed as E (n = l IJ) lexp (i φ-), and when the dispersion medium 31 is inserted The optical pulse electric field E'(t
The Fourier transform of Let φl■, φ2-.

As described above, in the measurements up to this point, there remains uncertainty regarding the sign reversal of the phase of the Fourier transform.

Additionally, there are trivial indeterminacies, ie, indeterminacies regarding the overall phase of the pulse and the time movement of the pulse. Due to these indeterminacies, it is not possible in principle to determine the zeroth and first order terms with respect to ω of the phase of the Fourier transform. Therefore, the true phase φ−1φ′■ is φ−=±φl■+pω+q ・ αQφ′■=±φ
It is expressed as 2−+p′ω+q′・αυ. Decoding is arbitrary, and pSp', q and q' are arbitrary real numbers. At this stage, even after excluding the trivial uncertainty mentioned above, there are still four types of uncertainties, which are expressed as the arbitrariness of decoding in (L1 equation and 60 equation).

Now, assume that the transmission characteristic of the dispersion medium 31 is T-. This is generally a complex number, and using the absolute value and phase, Th) = l T(A ley; p(iθ-)・-
It can be expressed as (12). Since the dispersion characteristics of this dispersion medium 31 are known, IT-1 and θ- are also known quantities. By the way, E■ and E'- are the dispersion medium 31, respectively.
Since this is the Fourier transform of the pulsed electric field before and after inserting into the optical path, there is a relationship of E' U = Tit) E■ · α■. If we divide this relationship into the absolute value part and the phase part and write it down, we get: l E' Ml = l TMI I E(u)l
・α0φ′(e) = φ−+ θ−QSI is obtained. Here, the relationship of equation 043 does not contribute to eliminating the above-mentioned uncertainty. On the other hand, the above-mentioned four types of indeterminacy can be removed by the relationship of Equation 09. This is the principle of the invention.

A procedure for removing the above-mentioned indeterminacy based on α expressions will be explained. φ-1φ'- in Equation 09 includes arbitrary coefficients p, p', q, and q' due to trivial arbitrariness, as shown in Equations 00 and 09. In order to remove these, α0. Ql) and formula 09 as n (n≧2
) times, then substitute an appropriate optical frequency ω=ω weight. As a result, (d”φ/dad”)(act) =±(d”φ+/d
al”) (03υαQ′ (d″φ’ /dω0)(ω1)=±(d”φa/dω
″) (ωi) αυ′ (d″φ’/d(1)”) (town) = (d″φ/dal″
) (town) + (d”θ/dω7) (ω1) αω′ is obtained. Here, α, = (dhφ/dω′″) (ω1) α,' = (
d”φ' /dω′′)(ωi)β, = (d”θ/
dω'') (ωi), the Q!it' formula becomes β.=-α, +α7'(n≧2) QS). This is the relationship that should hold for the differential of the true phase, This is the equation for determining the direction of the time axis.

It will be explained that the solution to Equation 00 is uniquely determined. Here, αr−= l (d”φ+/da”)(a’t) 1
If we write α2−”l (d”φZ/dω0)(ω1)1, α7=±αIRsα by the 002 formula and 0υ formula.
, / = ±αh. Substituting this into the α0 equation yields β,=±αIn±α27 (decoding arbitrary, n≧2).

Since the decoding is arbitrary, this formula becomes β7=±1αI
It is equivalent to the surface n±α, , l (arbitrary decoding, n≧2).

As long as β≠0, a combination of decoding that satisfies the α force equation is uniquely determined. This is because the first decoding can be determined by the sign of βゎ, and the second code can be determined by the magnitude of the value. When β7=0 for all n≧2,
Although it becomes impossible to determine the decoding combination, this case corresponds to a vacuum case, that is, a case where the dispersion medium 31 is not used. Therefore, any substance can be used as the dispersion medium 31, and uncertainty regarding time reversal can be completely removed.

Practically speaking, it is sufficient to use β2≠00 as the dispersion medium 31 and to determine the decoding from the 00 equation with n=2. Cross-checking can also be performed using higher order terms. β2 is proportional to the group velocity dispersion of the medium. Therefore, when using an optical fiber near the zero dispersion wavelength as the dispersion medium 31, β2 is small, so the equation for n; 3 or later is used.

As a special case, the light pulse has a linear instantaneous frequency change (
char, ping), the direction of the time axis can be determined from the change in the time width of the pulse when it passes through the dispersion medium 31 and when it does not pass through the dispersion medium 31, without using the procedure including the Fourier transform described above. .

This will be explained below.

The instantaneous frequency f (t) of the optical pulse is obtained by time-differentiating the phase of the complex amplitude E (t) of the optical pulse electric field, multiplying by −1, and further dividing this by 2π. This instantaneous frequency f (t) is between the instantaneous wavelength λ(1) and λ(t
) = c/ f (t) (c is the speed of light in vacuum)
There is a relationship between

Here, when the instantaneous frequency of an optical pulse increases linearly with time, it is said that the pulse is truly linearly chirped. Also, when it decreases linearly, it is said to be "negatively linear chirping."

If the sign of the linear chart can be determined, the direction of the time axis can be determined.

For this purpose, group velocity dispersion by the dispersion medium 31 is utilized. When light propagates through a medium exhibiting positive group velocity dispersion, light with a higher frequency (shorter wavelength) has a lower propagation speed than light with a lower frequency. Conversely, in a medium exhibiting negative group velocity dispersion, the propagation velocity of high-frequency light is high. Therefore, if a material with positive group velocity dispersion is used as the dispersion medium 31 and the pulse incident on the dispersion medium 310 is negatively linearly channeled, while propagating through the dispersion medium 31, the low frequency part at the rear end of the pulse catches up with the high-frequency part at the front end, and as a result, the time width of the pulse becomes short.On the other hand, if the incident pulse is exactly linear chirped,
The pulse width when passing through the dispersion medium 31 increases.

In this way, the sign of the group velocity dispersion of the dispersion medium 31,
The time axis of the pulse waveform can be determined from the change in the time width of the pulse when it passes through the dispersion medium 31. This method is intuitive and simple, but is effective when the pulse chirp is substantially linear.

FIG. 2 shows the measurement results when the dispersion medium 31 is not inserted on the optical path. The solid line shows the intensity waveform, and the dashed line shows the phase waveform. In this measurement, a light pulse with a wavelength of 600 nm generated by a mode-locked dye laser was used as the light pulse L to be measured.

In this measurement, the directions of the time axes are reversed as shown in Figure 2 (
Two pulse waveforms are obtained: a) and FIG. 2(b). However, at this stage it is not possible to determine which of the two is the true pulse waveform.

Figure 3 shows the same optical pulse using a dispersion medium 31 on the optical path.
The measurement results are shown when inserting . Similar to FIG. 2, the solid line indicates the intensity waveform, and the broken line indicates the phase waveform. As the dispersion medium 31, BK7 glass with a thickness of 5 Qmm was used.

Similarly, in this measurement, the direction of the time axis is reversed as shown in Figure 3 (
Two pulse waveforms a) and FIGS. 3, et al.) are obtained, and it is not determined which one is the true pulse waveform.

Accordingly, the direction of the time axis of each pulse waveform shown in FIGS. 2 and 3 was determined by the above-described procedure. When the pulse waveform in Figure 2 (a) is Fourier transformed and the second differential of the phase after the transformation is calculated, α2 = 0.00728.
It was [:ps2]. Similarly, for the pulse waveform in Figure 2, etc.), α2 = -0,00728 (ps"). For the pulse waveform in Figure 3(a), αa' =
O', 0106 Cps"], and in the pulse waveform of Fig. 3, etc.), α2' = 0.0106 [
pS']. Also, from the refractive index data of BK7 glass, the group velocity dispersion at a wavelength of 600 nm is n”
= 6.55 x 10-' Cps2/mm), and the thickness d is 5Qmm, so the group velocity dispersion of this dispersion medium 31 is β2 = n'' x d = 0.00328 (ps
') is easily calculated. Here, α that satisfies formula 00
2 and α2′ are respectively α, = 0,00728 [:ps2]α2′
= 0.0106 (ps2). Therefore, it can be seen that the pulse waveform shown in FIG. 2(a) and the pulse waveform shown in FIG. 3(c) are true pulse waveforms.

FIG. 4 shows these pulse waveforms. Figure 4(a) shows
The waveforms are shown when the light does not pass through BK7 glass, and the waveforms when the light passes through the BK7 glass are shown in FIGS. Similar to FIGS. 2 and 3, the solid line indicates the intensity waveform, and the broken line indicates the phase waveform.

In the above embodiment, an example was shown in which BK7 glass was used as the dispersion medium 31, but a medium exhibiting group velocity dispersion of an appropriate size or higher-order dispersion, such as an optical fiber,
The present invention can also be carried out using liquids or other liquids contained in cells. Further, the present invention can be similarly implemented using a Fabry-Perot etalon, a diffraction grating, or other elements whose dispersion characteristics can be set artificially. Furthermore, the present invention can be implemented in the same way by using a medium whose surface reflects the light pulse instead of transmitting it, such as a dielectric evaporated film or a Ziel-Tournoy interferometer.

Furthermore, the present invention can be implemented in the same manner by combining various conventional measurement methods as the optical pulse measuring device 33.

〔Effect of the invention〕

As explained above, the optical pulse measurement device of the present invention can determine the direction of the time axis of a short optical pulse, which was impossible with conventional measurement methods. As a result, (1) it can be used for ultra-high-speed time-resolved measurements using optical pulses, making it possible to rigorously evaluate the pulses themselves, greatly improving measurement accuracy, and (2) using them for signal transmission using optical pulses. This enables precise measurement of pulse intensity and phase waveforms, which are the limiting factors for transmission capacity, and can be used to optimize pulse control and improve the accuracy of experimental evaluations of transmission methods that utilize various nonlinear effects. There is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical pulse measuring device according to an embodiment of the present invention. FIG. 2 is a diagram showing measurement results of the intensity waveform and phase waveform of a light pulse when no dispersion medium is inserted on the optical path. FIG. 3 is a diagram showing measurement results of the intensity waveform and phase waveform of a light pulse when a dispersion medium is inserted on the optical path. FIG. 4 is a diagram showing true intensity waveforms and phase waveforms. FIG. 5 is a block diagram of a conventional optical pulse measuring device. 1124...Beam splitter, 2...Fixed prism, 3...Movable prism, 4...Moving table, 5.6
... Lens, 7... Nonlinear crystal, 8.30... Optical filter, 9.28... Photodetector, 10.29...
・Preamplifier, 11... Light source, 12... Reflector, 1
7... Waveform storage device, 18... Computer, 19
...178 Wave plate, 20... Polarizing beam splitter, 21.22... Photodetector, 23... Trigger signal generator, 31... Dispersion medium, 32... Switch, 33
...Light pulse measuring device. Patent applicant: Nippon Denchu Telephone Co., Ltd. Representative: Patent attorney Nao Takashi Ide 4- - , ,
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Claims (1)

[Scope of Claims] 1. An optical pulse measuring device comprising a measuring means for measuring an autocorrelation waveform of an optical pulse to be measured, and a calculating means for calculating the waveform of the optical pulse to be measured from the output of the measuring means. , the measuring means includes means for measuring the autocorrelation waveforms with respect to a state in which a medium with known wavelength dispersion characteristics is inserted into the incident optical path of the optical pulse to be measured and a state in which this medium is not inserted, respectively, An optical pulse measurement device characterized in that the calculation means includes means for determining the direction of the time axis of the waveform of the optical pulse to be measured from the two autocorrelation waveforms.