JP3052281B2 - Jitter measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ps superimposed on an ultrashort pulse signal to be measured, which is necessary for evaluating an ultra-high-speed optical or electric signal handled in fields such as communication, computer, medical and basic science. The present invention relates to a jitter measuring apparatus for measuring a very small jitter in the order of (picosecond; 10 ^-12 s) to fs (femtosecond; 10 ^-15 s) with high resolution.

[0002]

2. Description of the Related Art
In order to measure the jitter of the laser pulse, there is a method in which the laser pulse is converted into an electric signal by a photodetector and then measured by a high-resolution sampling oscilloscope. In this case, there is a drawback that the measurement accuracy is limited to several tens of ps of trigger jitter generated when sampling an electric signal. In addition, even if the photodiode used in the photodetector is of a high-speed type, a jitter of several tens of ps is generated, which also has the disadvantage that the measurement accuracy is limited.

Conventionally, to measure the jitter of a laser pulse, there is a method of directly measuring a laser pulse with an optical oscilloscope using a streak camera as a light detecting means. In this case, there is a disadvantage that the measurement accuracy is limited to an electric circuit jitter of about 20 ps for controlling the sampling light inside the optical oscilloscope. Conventionally, to measure the jitter of a laser pulse, the laser pulse is converted into an electric signal by a photodetector, then the higher order frequency of the pulse generation frequency is observed by a spectrum analyzer, and integrated in a specific frequency band with that frequency component. There is also a method of calculating the jitter by converting the result obtained from the frequency domain to the time domain. In this case, the photodetector is generally constituted by a photodiode, and even if the frequency band of the photodiode is a high-speed type, it is about several GHz.
There is a drawback that the order of the observation frequency is limited and high-accuracy jitter cannot be measured. Further, there is a disadvantage that the photodiode itself generates jitter of several tens of ps, which also limits measurement accuracy. Furthermore, because of the characteristics of the spectrum analyzer, the measurement accuracy of frequency components separated by several tens of Hz from the laser pulse generation frequency is low, and the influence of peripheral noise such as the power supply frequency often controls the amount of jitter. There is also a disadvantage that accurate jitter measurement cannot be performed.

As another conventional method for measuring the jitter of a laser pulse, a laser pulse is converted into an electric signal by a photodetector, then subjected to quadrature detection with a reference signal using a mixer to extract a jitter frequency component. There is a method of integrating a signal level and measuring the integrated signal with a voltmeter. In this case, even if the photodiode used in the photodetector is of a high-speed type, jitter of several tens of ps is generated, which also has the disadvantage that the measurement accuracy is limited.

[0005] It is an object of the present invention to convert a pulse to be measured synchronized with a reference clock of a jitter measuring apparatus from ps (picosecond; 10 ^-12 s) to fs (femtosecond; 10 ^-15 s) which could not be measured conventionally. It is intended to enable high-precision order jitter measurement.

[0006]

[Means for Solving the Problems]

(1) A jitter measuring device according to claim 1, a reference oscillator for generating a reference frequency (timing) of the entire jitter measuring device and a generation timing of a laser pulse to be measured, a frequency divider for dividing the reference frequency, and a frequency divider for the frequency divider. A synthesizer for generating a probe signal synchronized with the peripheral output and having a slight frequency difference (Δf) with respect to the reference frequency; an electric short pulse generator for shortening the probe signal; A circuit comprising a photoconductor module for convolving the output of the short pulse generator and a detector for detecting an envelope of the output, a counter for measuring the period of the output pulse of the detector, and measurement of the counter A jitter calculator for calculating the jitter amount of the laser pulse to be measured from the value.

(2) A jitter measuring device according to a second aspect of the present invention is a reference oscillator for generating a reference frequency (timing) of the entire jitter measuring device and a generation timing of a laser pulse to be measured, and a first frequency divider for dividing the reference frequency. And a frequency difference (Δ
a) a synthesizer for generating a probe signal having a frequency f), and a second synthesizer for dividing the output of the first frequency divider to a lower frequency.
A frequency divider, a pulse modulator for pulse-modulating the probe signal at the output timing of the second frequency divider, an electric short pulse generator for shortening the pulse-modulated probe signal, and a device under measurement with a small power A circuit comprising a photoconductor module for convolving the output of the laser pulse and the electric short pulse generator, and a lock-in amplifier for detecting an envelope of the output thereof in synchronization with the output timing of the second frequency divider; It comprises a counter for measuring the period of the output pulse of the in-amplifier, and a jitter calculator for calculating the jitter amount of the laser pulse to be measured from the measured value of the counter.

(3) A jitter measuring apparatus according to a third aspect of the present invention is a reference oscillator for generating a reference frequency (timing) of the entire jitter measuring apparatus and a generation timing of an electric short pulse to be measured, and a frequency divider for dividing the reference frequency. And a frequency difference (Δf) synchronized with the divided output and slightly with respect to the reference frequency.
Synthesizer that generates a probe signal with a pulse, an electric short pulse generator that shortens the probe signal, a mixer that convolves the output of the measured electric short pulse and the electric short pulse generator, and an envelope of the output of the mixer , A counter that measures the period of the output pulse of the detector, and a jitter calculator that calculates the amount of jitter of the electrical short pulse to be measured from the measured value of the counter.

(4) The jitter measuring apparatus according to claim 4 is a reference oscillator for generating a reference frequency (timing) of the entire jitter measuring apparatus and a generation timing of an electric short pulse to be measured, and a first divider for dividing the reference frequency. And a slight frequency difference (Δ
a) a synthesizer for generating a probe signal having a frequency f), and a second synthesizer for dividing the output of the first frequency divider to a lower frequency.
A frequency divider, a pulse modulator for pulse-modulating the probe signal at the output timing of the second frequency divider, an electric short pulse generator for shortening the pulse-modulated probe signal, and an electric short pulse to be measured. A circuit comprising a mixer for convolving the output of the electric short pulse generator and a lock-in amplifier for detecting an envelope of the output in synchronization with the output timing of the second frequency divider; and an output of the lock-in amplifier. It comprises a counter for measuring the pulse period, and a jitter calculator for calculating the amount of jitter of the measured electrical short pulse from the measured value of the counter.

(5) In the invention of claim 5, in any one of the above (1) to (4), the reference frequency is fr, the period measurement value of the counter is T _xi (i = 1, 2,...), And η = Fr
/ Δf, the jitter calculator calculates J (i) = (T _xi −Δf ⁻¹ ) / η; i = 1, 2,... As the jitter amount of the pulse to be measured.

(6) The invention according to claim 6 is the method according to any one of (1) to (4), wherein the jitter calculation section calculates the jitter amount of the pulse to be measured as:

[0012]

(Equation 3)

Is to calculate the following. (7) The invention according to claim 7 is the method according to any one of (1) to (4), wherein the jitter calculation section calculates the jitter amount of the pulse to be measured as:

[0014]

(Equation 4)

Here, T _xa = (T _x1 + T _x2 +... T _xN ) / N
Is calculated. (8) In the invention according to claim 8, in any one of the above (1) to (4), a semi-insulating substrate which becomes a conductor when the photoconductor module irradiates light, and a minute gap is formed on the semi-insulating substrate. And a pair of opposing electrodes formed to face each other.

(9) In a ninth aspect of the present invention, in the above (8), the pair of opposed electrodes of the photoconductor module has a comb-shaped electrode portion formed so as to mesh with each other via a minute gap. . (10) In a tenth aspect of the present invention, in the above (8), the semi-insulating substrate of the photoconductor module is composed of an InP (indium phosphide) substrate.

(11) The invention according to claim 11 is the method according to (8).
In the above, the pair of counter electrodes and the ground electrode formed on the semi-insulating substrate are formed of a gold thin film.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention reduces a minute jitter of the order of ps to fs superimposed on a pulse to be measured by about 100 million (1 × 10
⁹ ) Magnify with a double conversion rate η, convert it to jitter on the order of several ms to several μs, measure it with a general-purpose counter, and divide the measured jitter by the conversion rate η to increase the jitter of the pulse under measurement. It is measured with precision. [Embodiment 1] As shown in FIG. 1, a reference oscillator 1 generates a reference frequency fr of the entire apparatus. The measured laser system 2 generates a laser pulse P at a period T _P = T _r + J (1) obtained by adding or subtracting the jitter J to the period T _r = 1 / fr of the reference frequency fr. On the other hand, the reference frequency fr
To the desired frequency (typically 10 MHz or 5 MHz)
z) is divided by the frequency divider 3 and input as an external reference frequency of the synthesizer 4, and a known small frequency difference Δf (for example, several H) with respect to the generation frequency fr of the laser pulse P
A stable frequency fr−Δf (or fr + Δf) having several hundred mHz from z (0.1 Hz in the embodiment) is obtained from the synthesizer 4 as the probe signal S. Here, Δf is called a scanning frequency. Next, at the timing of the synthesizer output S, 100 ps (= 0.1
ns) about say electrical short pulse (probe signal pulse having a pulse width) is generated S ", is input to one end of the counter electrode of the photoconductor module 6. period T _P = T _r
When the measured laser pulse P generated at + J is irradiated on the photoconductor portion of the photoconductor module 6,
Only the resistance value between the opposed electrodes is low when the laser pulse P is irradiated, then the probe signal pulse S "is transmitted to the other end of the counter electrode. Of the output signal S _o of the photoconductor module 6 by detecting the envelope in detector 8, the period T _P of the measured laser pulses P is the period _{T xi T xi = ηT P (} i) = η {T r + J (i)} = ηT r + ηJ (i) = (1 / Δf) + ηJ (i) (2) (see FIG. 2).

This means that the product of the time function of the probe signal pulse S ″ ≡x (t) and the time function of the laser pulse to be measured h (t) is obtained by the photoconductor module 6, and the time function y (t However, these two signals are integrated by the detector 8 after adding a time lag due to a slight frequency difference Δf set by the synthesizer. The convolution operation shown in FIG.

[0020]

(Equation 5)

[0021] The convolution by the laser pulse generating period T _P is converted into is multiplied conversion eta T _xi,
Nominal value of T _xi (nominal value) is a scanning period (1 / Δf). Conversion rate η = reference frequency (fr) / scanning frequency (Δf) (4) Then, at this conversion rate η, the minute jitter J superimposed on the laser pulse P to be measured is also enlarged. That is, η is also the jitter magnification. Then, to measure the pulse generation cycle T _xi of the detected envelope in counter. The period _Txi measured here is the scanning period (1 / Δf) when no jitter is present.
_Where the deviation of the period _Txi observed with respect to the scanning period (1 / Δf) represents the jitter. Then, the deviation from the scanning cycle (1 / Δf) actually measured by the counter, that is, the variation T _xi − (1 / Δf) = ηJ (i) of the scanning cycle is divided by the conversion rate η to obtain the actual measured laser. The pulse jitter J (i) can be calculated. That is, J (i) = { _Txi− (1 / Δf)} / η (5) Also, the scanning period (1 / Δ) of the period _Txi of the detector output S _o ′
standard deviation Σ ′ for f)

[0022]

(Equation 6)

Then,】 ′ is divided by the conversion rate η to obtain a statistical jitter amount σ ′ of the laser pulse to be measured. σ ′ = Σ ′ / η (7) Alternatively, N average values T of the period T _xi of the detector output S _o ′
_xa T _xa = (T _x1 + T _x2 ... + T _xN ) / N (8) is obtained, and the standard deviation に 対 す る of the average value T _xa of the period T _xi , that is, a more general standard deviation よ り is obtained from the following equation. Asked,

[0024]

(Equation 7)

By dividing Σ by the conversion rate η, the statistical jitter amount σ of the pulse to be measured can be obtained. σ = Σ / η (10) Next, the photoconductor module 6 will be described with reference to FIGS. The photoconductor unit 12 is formed on an InP (indium phosphide) substrate 11 doped with Fe (iron), which is a semi-insulator. A semi-insulator is a substance that is usually an insulator, but becomes a conductor when irradiated with light.
A conductor such as gold (Au) is vapor-deposited on the InP substrate 11, and transmission lines (transmission electrodes) 13a and 13b are formed on the center line by coplanar lines, which are a kind of strip line having a characteristic impedance of 50Ω in general. Earth lines (earth electrodes) 15a and 15b are formed on both outer sides of the transmission electrodes 13a and 13b. The characteristic impedance is determined by the properties of the substrate, the width of the transmission line 13, the distance between the transmission line 13 and the ground line 15, and the like. For example, when the width of the transmission line is about 50 μm on the InP substrate, the distance between the transmission line 13 and the ground line 15 is 70 to 80.
μm. The characteristic impedance of the coplanar line is not limited to 50Ω.

Near the center of the transmission line 13, a pair of opposed electrodes 14a and 14b facing each other via a gap are formed. The shape of the opposing electrodes 14a and 14b is preferably a comb-shaped electrode in which the teeth are incorporated into each other. Here, the pair of opposed electrodes means the electrode conductor thin film facing with a gap width W _i of several μm on a semi-insulating substrate. I
The size of the nP substrate 11 is about 1 × 2 mm square, and the electrode gap interval W _i is, for example, about 1 to 2 μm for the width of one comb tooth and the interval between teeth even in the case of a comb electrode. Very small. Thus, when the frequency band is 1
A photoconductor having a high-speed response of 00 GHz or more can be produced.

The semi-insulating substrate 11 is mounted in a case in which, for example, a small high-frequency coaxial connector or the like is connected and attached to both ends of the transmission lines 13a and 13b of the semi-insulating substrate prepared as described above to form a module. Here, the photoconductor module 6 is used. The photoconductor module 6 has an on-resistance of several tens Ω to several kΩ when irradiating laser, an off-resistance of several hundred MΩ when not irradiating laser, and an interelectrode capacitance of 10 fF or less. The large on / off resistance difference and the extremely low interelectrode capacitance enable the laser pulse to be efficiently converted into an electric signal over a wide band, and the comb-shaped counter electrode 14 effectively reduces the amount of laser light. Available.

Next, the embodiment of FIG. 1 will be specifically described with reference to numerical examples. When the measured laser system 2 is _Tr = 10 ns
, Ie, the case where the laser pulse P to be measured can be generated at a repetition rate of 100 MHz, the frequency fr of the reference oscillator 1 is oscillated at 100 MHz in order to set the reference timing _{Tr of the} entire apparatus to 10 ns. The frequency division ratio of the frequency divider 3 is set to 1/10, and 10M
Hz frequency division output is obtained. Using this 10 MHz as a reference frequency, a synthesizer 4 generates a probe signal S of 99.9999999 MHz, that is, fr-Δf = 100 MHz-0.1 Hz. This Δf = 0.1 Hz is the scanning frequency. Therefore, the conversion rate η is η = fr / Δf = 100 × 10 ⁶ /0.1=10 ⁹ (11), and the jitter J of the laser pulse P to be measured is multiplied by 10 ⁹ .

As the synthesizer 4, a commercially available high-purity synthesizer is used. Signal rate fr-Δf of probe signal S output from synthesizer 4 = 100 MHz-0.1H
As the short pulse generator 7 for obtaining the probe signal pulse S ″ having z, a commercially available broadband harmonic generator (com generator) made of a step recovery diode for high-speed switching is used. The comb generator requires a large amplitude input signal of about several tens of dBm. However, since a commercially available synthesizer 4 cannot output such a large amplitude, the signal S 'obtained by amplifying the output signal level of the synthesizer 4 by the low noise amplifier 5 is used. Is input to the short pulse generator 7. The short pulse generator 7 outputs the output signal rate fr−Δf = 100 MHz−0.1 Hz of the synthesizer 4.
Generates an electric short pulse having a pulse width of about 100 ps = 0.1 ns. This probe signal pulse S ″ is applied to one end of the counter electrode 14 of the photoconductor module 6.

On the other hand, a repetition rate of fr = 100 MHz
The measured laser pulse P generated by the
Directly or on the photoconductor portion 12 of the module 6
Irradiation is performed by an optical fiber 16 or the like (see FIGS. 3 and 4).
As a result, the other end of the photoconductor module 6
Output signal S obtained from the counter electrode of FIG. _o
Is the difference between the measured laser pulse P and the probe signal pulse S ″.
Only when the timing of both occurrences matches, the level
Where they change, and where they do not match,
Become. Photoconductor output S_o(i) Envelope wave
Shape varies over time. In other words, it is fluctuating (Fig. 2
reference). General envelope with resistor R and capacitor C
Loop detector 8 (see FIG. 5)
Force signal S _oScan rate 1 / Δf
= Generation period T of pulse generated once every 10 seconds_xi= ΗT_P
(i) is measured by the counter 9 about 100 times, for example. So
And the measured value T obtained by the counter 9 in the jitter calculator 10
_xiTo 10 s obtained by subtracting the scanning period 1 / Δf = 10 s from
Fluctuation range T_xi-100 standard deviations of (1 / Δf)
Σ ′ is obtained, and the value is calculated as the conversion rate η = 10⁹Divided by
This is the actual jitter amount σ ′ of the measured laser pulse.

For example, the period of the pulse S ₀ ′ to be measured is approximately 10 seconds, but it is measured 100 times, and 1
Assuming that the standard deviation Σ ′ of the fluctuation value with respect to 0 second is 1 ms, the actual jitter amount σ ′ of the laser pulse P is 1 ms.
/ 10 ⁹ can be calculated as 1 ps. Next, an embodiment of the photoconductor 6 will be described.

A semi-insulating substrate 1 having a size of about 1 × 2 mm square
1, for example, a pair of counter electrodes 14a,
14b and a pair of transmission lines 1 consisting of a coplanar line connected to this electrode.
3a and 13b are configured. The characteristic impedance is determined by the distance between the transmission line 13 and the earth line 15, the width of the transmission line 13, the material of the substrate, and the like. Here, the characteristic impedance is designed to be a typical 50Ω characteristic impedance.

The method of forming is to apply a resist on the InP substrate 11, leave the resist only at the portion where the metal is removed by mask exposure and peeling, and peel off the other resist. A metal film, for example, Au is vapor-deposited on the entire surface, and the metal in the resist portion is removed together with the resist using a removing solution. By a technique called the lift-off method, the photoconductor portion 1 including the counter electrode is
2. Transmission lines 13a and 13b and earth line 15
a and 15b are created.

In the examples of FIGS. 3 and 4, the counter electrodes 14a, 14
b is composed of a comb-shaped electrode. The comb-shaped electrode has a structure in which two comb teeth each penetrate each other from the comb branches. Comb tooth width and tooth-to-teeth spacing W
₁ , W ₂ and W ₃ are each about 2 to 6 μm. The semi-insulating substrate 10 appears directly between the gaps.
Usually, it is electrically insulated at about several hundred MΩ.

An electric short pulse S "is applied to one end of the pair of electrodes. That is, a voltage is applied to one of the transmission lines 13a in an extremely short time. , Semi-insulating substrate 11
For example, InP is activated, and conduction is performed only for an extremely short time during which laser irradiation is performed, and an output is obtained on the other transmission line 13b. [Embodiment 2] When the laser system to be measured 2 is a mode-locked laser system or the like having a relatively large laser pulse emission intensity, the output level of the photoconductor module 6 can be as high as several hundred mV, so that a simple detection circuit However, when the laser diode emits light using a gain switch method or the like to generate a laser pulse to be measured, the emission intensity of the laser diode is weak.
The output level of the photoconductor module 6 is several mV
Alternatively, the signal may be less than that, the desired signal is buried in the noise, and even if the signal level is simply amplified, the detection circuit cannot detect the envelope. Therefore,
As shown in FIG. 6, an envelope of a desired signal buried in noise is detected on the order of μV using a lock-in amplifier 21 which is often used for detecting a minute voltage. In this embodiment, in addition to the first embodiment, the output signal S (100M
Hz-0.1 Hz) is input to a pulse modulator 20 composed of a general double-balanced mixer or the like, and pulse-modulated at a reference signal frequency of 1 kHz for lock-in detection. The reference signal CK ₂ for lock-in is obtained by further dividing 10 MHz which is the output CK ₁ of the frequency divider 3 into 10
It is made by dividing by 000, and its frequency becomes 1 kHz.
However, the frequency is not limited to 1 kHz. Probe signal S _sw pulse-modulated at 1 kHz (100 MHz-0.1H
In z), the probe signal pulse S _sw ″ shortened by the short pulse generator (com generator) 7 is applied to one end of the counter electrode of the photoconductor module 6 as in the above-described embodiment. Since the light emission intensity of the diode is weak, the level of the output signal S ₀ of the photoconductor module 6 becomes weak and is buried in a noise component. Here, since the probe signal pulse S _sw ″ is pulse-modulated, the photoconductor The output signal S _{0 of the} module 6 is also pulse-modulated at the same modulation frequency of 1 kHz and output. This pulse-modulated photoconductor
The output signal of the module 6, the output signal CK ₂ of the frequency divider 19 obtained by pulse modulation of the probe signal S to the lock-in amplifier 21, synchronous detection only true photoconductor output signal S ₀ at the pulse modulation frequency 1kHz Then, the noise component superimposed on the photoconductor output signal S ₀ is driven to the modulation frequency band, and only the interferogram is extracted by the low-pass filter in the lock-in amplifier 21. This means that the interferogram is detected at the same time. This interferogram corresponds to the output of the detector 8 in the embodiment of FIG. 1 and is input to the counter 9. Subsequent processing is the same as in the above-described embodiment, and a description thereof will be omitted. [Embodiment 3] The embodiments 1 and 2 described above are aimed at measuring the jitter of the laser pulse. Also enables jitter measurement.

In the third embodiment shown in FIG.
The electrical short pulse generator 23 generates the electrical short pulse P 'to be measured at the output timing (fr), and the electrical short pulse P' and the probe signal pulse S obtained by shortening the output S of the synthesizer 4 "the mixer 24 is convolution. interferograms obtained as the output S ₀ of the mixer 24 corresponds to the output of the photo conductor module 6 of examples 1 and 2, detects an envelope of the output signal of the mixer 24 The detection signal S ₀ ′ is input to the counter 9. The subsequent processing is the same as in the first and second embodiments, and a description thereof will be omitted. When the level of the pulse is relatively large, the envelope of the output of the mixer 24 can be detected by a simple detection circuit as in the third embodiment (see FIG. 7). Small case, the lock-in amplifier 21 in the same manner as in Example 2 as shown in FIG. 8 may be detected envelope of the output of mixer 24.

[0037]

As described above, according to the present invention, the reference oscillator 1 synchronizes the timings of the jitter measuring device and the measured pulse generator 2 as a whole, while generating the laser or electric pulses P and P 'at the same frequency. Probe signal pulse S ″ having a particularly small frequency difference Δf with respect to fr
And by convolving the two, a small jitter J superimposed on the measured pulses P and P 'can be expressed as η = f
ps, which was previously impossible because it can be expanded by r / Δf times
High-precision measurement of jitter on the order of (picoseconds) to fs (femtoseconds) has become possible.

Therefore, the time resolution for evaluating ultra-high-speed optical or electrical signals in the fields of communication, computer, medicine, basic science, etc. is greatly improved by using the present invention, and the technical effect is extremely large. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram of a main part of FIG.

FIG. 3 is an enlarged perspective view of the photoconductor module 6 of FIG. 1;

FIG. 4 is a plan view of a photoconductor unit of the photoconductor module 6 of FIG. 3;

FIG. 5 is a circuit diagram showing an example of the detector 8 of FIG. 1;

FIG. 6 is a block diagram showing an embodiment of the invention of claim 2;

FIG. 7 is a block diagram showing an embodiment of the invention of claim 3;

FIG. 8 is a block diagram showing an embodiment of the invention of claim 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reference oscillator 2 Laser system to be measured 3 Divider 4 Synthesizer 5 Low noise amplifier 6 Photoconductor module 7 Electric short pulse generator 8 Detector 9 Counter 10 Jitter operation part 11 Semi-insulating substrate 11a, 11b Semi-insulating substrate Exposure surface 12 Photoconductor 13a, 13b Transmission line / transmission electrode 14, 14a, 14b Comb electrode / counter electrode 15, 15a, 15b Earth line / earth electrode 16 Optical fiber 19 Divider 20 Pulse modulator 21 Lock-in amplifier 23 Electric short pulse generator to be measured 24 Mixer

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) G01M 11/00-11/02 G01R 29/02 H04L 25/02 JICST file (JOIS) Practical file (PATOLIS) Patent File (PATOLIS)

Claims (11)

(57) [Claims] A reference oscillator for generating a reference frequency (timing) of the entire jitter measuring apparatus and a generation timing of a laser pulse to be measured; a frequency divider for dividing the reference frequency; A synthesizer for generating a probe signal having a slight frequency difference (Δf) with respect to a reference frequency; an electric short pulse generator for shortening the probe signal; a laser pulse to be measured and the electric short pulse generator A circuit consisting of a photoconductor module and a detector for detecting the envelope of the output, a counter for measuring the period of the output pulse of the detector, and a measured value based on the measured value of the counter. A jitter measuring device, comprising: a jitter calculator that calculates a jitter amount of a laser pulse. 2. A reference oscillator for generating a reference frequency (timing) of the entire jitter measuring apparatus and a generation timing of a laser pulse to be measured, a first frequency divider for dividing the reference frequency, and synchronizing with the divided output. A synthesizer for generating a probe signal having a slight frequency difference (Δf) with respect to a reference frequency, a second frequency divider for dividing the output of the first frequency divider to a lower frequency, and the probe A pulse modulator for pulse-modulating a signal at an output timing of a second frequency divider, an electric short pulse generator for shortening the pulse-modulated probe signal, a laser pulse to be measured having a small power, and the electric pulse A photoconductor module for convolving the output of the pulse generator and a lock for detecting an envelope of the output in synchronization with the output timing of the second frequency divider. A circuit comprising an in-amplifier; a counter for measuring a period of an output pulse of the lock-in amplifier; and a jitter calculator for calculating a jitter amount of the laser pulse to be measured from a measured value of the counter. Jitter measuring device. 3. A reference oscillator for generating a reference frequency (timing) of the entire jitter measuring apparatus and a generation timing of an electric short pulse to be measured, a frequency divider for dividing the reference frequency, and synchronizing with the divided output. A synthesizer for generating a probe signal having a slight frequency difference (Δf) with respect to a reference frequency, an electric short pulse generator for shortening the probe signal, an electric short pulse to be measured, and the electric short pulse A circuit comprising a mixer and a detector for detecting the envelope of the output of the generator, a counter for measuring the period of the output pulse of the detector, and an electric short circuit to be measured based on the measured value of the counter. A jitter measuring device, comprising: a jitter calculating unit that calculates a jitter amount of a pulse. 4. A reference oscillator for generating a reference frequency (timing) of the entire jitter measuring apparatus and a generation timing of an electric short pulse to be measured, a first frequency divider for dividing the reference frequency, and a divided output. A synthesizer for synchronizing and generating a probe signal having a slight frequency difference (Δf) with respect to a reference frequency, a second frequency divider for dividing the output of the first frequency divider to a lower frequency, A pulse modulator for pulse-modulating the probe signal at the output timing of the second frequency divider, an electric short pulse generator for shortening the pulse-modulated probe signal, an electric short pulse to be measured, and the electric short pulse generation A circuit comprising a mixer and a lock-in amplifier for detecting the envelope of the output of the mixer in synchronization with the output timing of the second frequency divider. A jitter measuring apparatus comprising: a counter for measuring a cycle of an output pulse of a quin amplifier; and a jitter calculator for calculating a jitter amount of an electric short pulse to be measured from a measured value of the counter. 5. The method according to claim 1, wherein the reference frequency is fr, and the period measurement value of the counter is T _xi.
When (i = 1, 2,...) And η = fr / Δf, the jitter calculation unit calculates J (i) = (T _xi −Δf ⁻¹ ) / η; i as the jitter amount of the pulse to be measured. = 1, 2,... 6. The method according to claim 1, wherein the reference frequency is fr, and the period measurement value of the counter is T _xi.
(I = 1, 2,...) And η = fr / Δf, the jitter calculator calculates the jitter amount of the pulse to be measured as: And a jitter measuring device. 7. The method according to claim 1, wherein the reference frequency is fr, and the period measurement value of the counter is T _xi.
(I = 1, 2,...) And η = fr / Δf, the jitter calculator calculates the jitter amount of the pulse to be measured as Here, a jitter measuring apparatus that calculates T _xa = (T _x1 + T _x2 +... T _xN ) / N. 8. A semi-insulating substrate according to claim 1, wherein said photo-conductor module becomes a conductor by irradiating light, and is formed on said semi-insulating substrate with a small gap therebetween. And a pair of opposed electrodes. 9. The jitter measuring apparatus according to claim 8, wherein the pair of opposed electrodes of the photoconductor module has a comb-shaped electrode portion formed so as to mesh with each other via a minute gap. 10. The jitter measuring apparatus according to claim 8, wherein the semi-insulating substrate of the photoconductor module is an InP (Indium Phosphorus) substrate. 11. The jitter measuring apparatus according to claim 8, wherein the pair of counter electrodes and the ground electrode formed on the semi-insulating substrate are made of a gold thin film.