JPH04148873A - Optical sampling device - Google Patents

Abstract

PURPOSE:To enable a high-speed measurement signal to be measured with a high S/N ratio by measuring a voltage waveform of a circuit to be measured based on an output of a calculation circuit. CONSTITUTION:This device is provided with an electric optical element 31 which changes a polarization surface by an electric field corresponding to an operation voltage of a circuit 15 to be measured by entering an output light of an optical pulse generation means 10 which outputs optical pulses with an optical frequency of light; a laser light source 20 which outputs a continuous light with a second optical frequency; a synthesizing means 22 for synthesizing both; a light-receiving element 23 which receives an output light of the means 22; and a calculation circuit 24 which calculates voltage waveform of the circuit to be measured 15 based on this output. A polarization surface of optical pulses with the first optical frequency is rotated by an electric optical element 31 and is entered into the light-receiving element 23 along with a local oscillation light with the second optical frequency for performing optical frequency heterodyne detection, thus enabling signal to the amplified equivalently and internal voltage waveform of the circuit to be measured 15 is measured with a high S/N ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a device for measuring high-speed electrical signals, and more particularly to an optical sampling device with improved S/N ratio.

<Prior Art> Recently, many high-speed electronic devices have been developed with high distances. For example, HE M T (H1(Ih f +e
ctr.

The gate delay time of the N Nobility'transistor is approximately 1.0 ps, and the direct modulation band of semiconductor lasers used in optical communications has reached several tens of GHz. A sampling oscilloscope is usually used to measure high-speed phenomena using such high-speed electronic devices. Figure 4 does not show the principle of a sampling oscilloscope. That is, as shown in (A), N consecutive signals under test are measured while changing the gate time little by little, and the results are synthesized (F
Measurements like ()? ).

In this technique, the sampling width becomes the resolution of the measurement result.

However, in the sampling oscillator I7 scope of the 111th system, the sampling width is limited by the speed of the step recovery diode, and the limit is about 25 ps, while the limit of the sampling width is about 610 ps in the optical oscillator 17 scope that uses optical pulses. There are drawbacks to the upside.

On the other hand, since the GaAs substrate has an E-optical effect, the one-power wavefront of the returned light changes depending on the magnitude of the electric field. Taking advantage of this phenomenon, measurement devices using light have been developed. FIG. 5 shows the configuration of a measuring device using such light. The output light of the YAG laser 1 is compressed to a pulse width of approximately ps in the pulse compression section 2, and then
The signal is input to the G a AS integrated circuit 5 via the wave plate 4 . Further, the returned light passes through the wavelength plate 4, is reflected by the polarizer 3, and its intensity is determined by the light receiving probe 6 as A1, and the display section 8
will be displayed.

When the drive circuit 7 changes the electric field generated by the G a A,s integrated circuit 5, the polarization plane of the returned light changes, and the intensity of the light incident on the light receiving probe 6 changes by the polarizer 3. The driving circuit 7 synchronizes the timing of the output light of the YAG laser 1 and the timing of driving the GaAs integrated circuit 5, and by gradually shifting the phase difference, the timing of the output light of the YAG laser 1 and the timing of driving the GaAs integrated circuit 5 are synchronized. Same as Zambrink technology 1. ]
Based on this principle, the internal voltage waveform of the GaAs integrated circuit 5 can be measured. According to this device, measurement can be performed with a sampling width of ps order. IJ Noh.

<Problems to be Solved by the Invention> However, the device shown in Fig. 5 uses an Nd:YAG laser pumped by an F1a5h lamp, and this has disadvantages in terms of size (total length: 2 m), power consumption, cost l~, and band. There are problems and improvements are desired. Therefore, it is currently being considered to replace it with a semiconductor laser or a solid-state laser pumped by a semiconductor laser, but this has the problem of low optical power and poor S/N.

<Purpose of the Invention> This invention was made to solve the problems listed in L.
The purpose is to realize an optical sampler device that can measure by ratio.

Means for Solving the Problems> The present invention changes the state of the polarization plane of an optical pulse according to the operating voltage of the circuit under test, detects this change in the polarization plane, and measures the voltage waveform of the circuit under test. The f-type optical sunblink system is characterized by a light pulse generating means for outputting a light pulse having a first light frequency, and a light pulse generating means for inputting the output light of the light pulse generating means. C: an electro-optical element that changes the plane of polarization by an electric field corresponding to the operating voltage of the circuit under test; a laser light source that outputs continuous light having a second optical frequency; return light from the electro-optical element; and the laser light source. A sonic wave hand 1jQ that combines the output of ) ~1 and this combined wave 1
A light-receiving element r- that receives the output light of the stage and an arithmetic circuit that calculates the voltage waveform of the circuit under test based on the output of this light-receiving element. It is configured to measure the electric waveform of [7].

Effect> The optical pulse having the first optical frequency is rotated in the polarization plane in the electro-optical element to which the electric field of the circuit under test is applied, and is incident on the light receiving element together with the locally oscillated light having the second optical frequency, thereby changing the optical frequency. By performing heterotine detection, the signal is amplified isometrically and the internal voltage waveform of the circuit under test has a high S/N.
It can be measured as a ratio.

<Embodiment> FIG. 1 shows an embodiment of the optical sampling device according to the present invention.

In FIG. 1, reference numeral 10 denotes an optical pulse generating means that outputs an optical pulse having a first optical frequency of 1-Dl, and is composed of a highly coherent semiconductor laser. An optical isolator that collects the returned light IJ-1, 12 a surface photon that transmits the light output from the optical isolator, 13 a wavelength plate that adjusts the plane of polarization of the output light from the polarizer 13, and 14 (a wavelength plate) The light output from 13 is connected to the limb measurement circuit consisting of Ga and A s integrated circuits.
．． 5 (C is a beam condensing beam. 16 is a semiconductor, one IO is 1) a pulse generation circuit that mediates an electric pulse that moves, 17 is a light pulse θ) repetition 1-7 frequency f' 1.
of! A high frequency oscillator 18 drives the pulse generation circuit 16 with a sinusoidal wave No. 111, a drive circuit 18 drives the circuit under test 15 at a frequency that is synchronized with the oscillator 17 and is slightly shifted from the frequency by a small frequency Δf, and 20 a locally mediated JI6 light source. 21 is a semiconductor laser light source that outputs continuous light with a second optical frequency f1.2 and high coherency; 22 directs the reflected light from the circuit under test 15 to the lens 1. Wavelength & 13
and a half mirror that forms a t-wave means that makes sound waves with the output light of the optical isolator 21 through the polarizer 12.
223 is a light receiving element 1 that receives the output light from the half mirror 22.
'-12.'1 is an arithmetic display circuit which calculates the internal voltage waveforms of the four R1, 5 to be measured based on the electrical output of the light receiving element-1'23.

The operation of the apparatus having the above configuration will be explained next.

The semiconductor laser 10 generates a narrow optical pulse by the electric pulse output of the pulse generator iN816. This light pulse is transmitted to the optical isolator 11. Polarizer 12. The light passes through the wave plate 13 and is focused on the circuit under test 15I- by the lens 14.

As shown in FIG. 2, this incident light enters from the back surface of the circuit under test 15, passes through the Ga A...s substrate 31, and
The light is reflected by the back surface of the IC pattern 32 on the front surface of the circuit under test 15, passes through the Ga, As substrate 31 in the opposite direction, and is emitted from the back surface. Since the GaAs substrate of the circuit under test 15 has an electro-optic effect, the plane of polarization of this reflected light depends on the electric field intensity generated in response to the intensity of the electric signal on the IC pattern with respect to the plane of polarization of the incident light pulse. Change. This reflected light pulse is transmitted to the lens 14. After passing through the wavelength plate 13 in the opposite direction, the light is reflected by the polarizer 12 and undergoes light intensity modulation according to its plane of polarization. The reflected light from the light beam 12 is combined with the continuous output light from the semiconductor laser 20 that has passed through the optical isolator 21 by the barf mirror 22, and is detected by the light receiving element 23. Error detection is performed. Arithmetic display device 24
displays the internal signal waveform of the circuit under test 15 based on the output of the light receiving element 23.

The 17th dyne detection will be explained below using equation-1. For example, if the optical frequency of the optical output from the semiconductor laser 10 is ω1, it is expressed as E1 sin ω11, and the optical output from the semiconductor laser 20 has an optical frequency of 6.
12, then 1-”) 2 S 1 n O,
)2[, is expressed as. Are these two lights? Hafmirah-22
When the light is combined by ,
; in (me) 2 t)...
1). f after being converted into an electrical signal by the light receiving element 23 and passing through a circuit to a low-pass filter and DC cutter;
-1 is E −E C08(ω ω2)t, = (2)
becomes. Here ω −ω −2π(f −f )1 2
1D1 +112...(3). In equation (2), El is covered by )11 constant circuit 1
Although the internal voltage signal of 6 contains useful information, normally E << F, , E2 --- is constant, so El(El ・E2, and isometrically the signal It is clear that E1 is amplified by E2 times, and the S/N ratio is improved.

Furthermore, since the sampling technique is used, the fundamental frequency go'd of the drive signal of the circuit under test 15 output from the drive circuit 18 is expressed as fd2N-f, +Δf (4). Here, N=1.2, 3. ...1, Δf is a minute frequency. Due to the presence of Δf in equation (4), it is possible to sample the telegram to be measured in the circuit under test 15 using optical pulses with a slight phase shift, thereby converting a fast phenomenon into a slow one. It can be treated as The difference in explaining this in terms of the fundamental frequency is that the high frequency fd in the object under test is converted to a low frequency Δf.

According to an optical sampler device having such a configuration, the S/N ratio can be improved by using heterodyne detection, and the optical power can be improved by using a semiconductor laser or a semiconductor laser pumped solid-state laser. Although it is small, it allows the use of light sources that are low in power consumption, cost, and bandwidth.

Covered again! 11. Since the optical power incident on the constant object can be reduced, it is possible to prevent the occurrence of photoelectrons and reverse electro-optic effects caused by excessive optical power, and the influence on the circuit under test can be suppressed.

Although a semiconductor laser is used as a light source in the above embodiment, a solid-state laser pumped by a semiconductor laser with high coherency may also be used.

FIG. 3 is a block diagram showing a main part configuration of a modification of the device shown in FIG. 1, in which the detection section has a differential configuration in order to further improve the S/N ratio. The same parts as in FIG. 1 are given the same symbols. The light output from the semiconductor device 10 passes through the photon 33, the rotator 37, and the polarized light r-12, and is guided to the circuit under test 15.The output light from the circuit under test 15 has its plane of polarization. For X and Y direction components, +
The 1iI photon 12 and the polarized light -r-33 are separated and each of the 6 separated lights is outputted by a barf mirror 38.39
It is combined with the optical output of the semiconductor laser 20 at. Each of the multiplexed lights is detected by light receiving elements 34 and 35, and subtracted from each other by a subtracter 36. Since the polarization plane of the optical pulse is modulated in the circuit under test 15 with the X and Y direction components having opposite polarities, the light receiving probe 34. ．． If the optical system alignment 1~ is performed so that equal amounts of opposite phase components are incident on the light receiving element 34 and 35, the noise of the light source itself is irrelevant to the phase.
The signals are in phase and canceled by subtraction, and the signal components of the detection light modulated by the circuit under test 15 are in opposite phase and are added together by subtraction. As a result, the S/N ratio becomes even whiter.

Note that in these examples, the case where the object to be measured is a Ga, As integrated circuit, that is, the case where the object to be measured itself is made of an electro-optic material, has been explained, but it is also possible to use a material such as silicon which does not have an electro-optic effect. This also applies to A1 fees. In this case, 1-7j′I″a O
3. A material having an electro-optic effect, such as a single crystal, is arranged, and the light is totally crystallized in this L i 'I''aO3 crystal, so that the electro-optic effect is caused by the electric field generated by the circuit under test made of silicon or the like. The deviation is good.

Furthermore, instead of detecting a change in the state of one wavefront of reflected light from the circuit under test, transmitted light may be detected.

<Effects of the Invention> As described above in detail based on the embodiments, the present invention provides an optical sampling device that can measure high-speed measurement No. 18 with a high S/N ratio using a semiconductor laser or the like. can be realized with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a configuration block I7 diagram showing an embodiment of the optical sampler device according to the present invention, FIG. 2 is a block diagram 1 explaining the operation of the device shown in FIG. Figure 41 is a block diagram showing a modification of the apparatus; Figure 41 is a diagram showing the principle of the Sunblink technology; Figure 5 is a diagram showing the configuration of a conventional optical sampler apparatus.

Claims (1)

[Scope of Claims] An optical sampling device that changes the state of the polarization plane of an optical pulse according to the operating voltage of the circuit under test, and measures the voltage waveform of the circuit under test by detecting the change in the polarization plane, comprising: an optical pulse generating means for outputting an optical pulse having an optical frequency of 1; an electro-optical element for receiving the output light of the optical pulse generating means and changing the plane of polarization by an electric field corresponding to the operating voltage of the circuit under test; a laser light source that outputs continuous light having a second optical frequency; a multiplexer that multiplexes the return light from the electro-optical element and the output light of the laser light source; and a receiver that receives the output light of the multiplexer. and a calculation circuit that calculates the voltage waveform of the circuit under test based on the output of the calculation circuit, and is configured to measure the voltage waveform of the circuit under test based on the output of the calculation circuit. Optical sampling device.