JP3406523B2 - Electro-optic sampling oscilloscope - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-optical sampling oscilloscope used for measuring various signals.

[0002]

2. Description of the Related Art Recently, for example, an electro-optic sampling oscilloscope capable of measuring without disturbing a circuit under test is used for signal measurement of a circuit under test that handles a signal having an ultra-high bit rate of 2.4 Gbps. Has been.
Here, the electro-optic sampling oscilloscope uses an electro-optic probe that detects the signal under measurement by utilizing the electro-optic effect.

Further, the above-mentioned electro-optical sampling oscilloscope (1) is easy to measure because it does not require a ground line when measuring a signal. (2) The metal pin at the tip of the electro-optical probe is removed from the circuit system. Since they are isolated from each other, a high input impedance can be realized, and as a result, the state of the measured point is hardly disturbed. (3) Since the optical pulse is used, wideband measurement up to GHz order is possible. , It is especially used for the measurement of communication information systems, which are becoming faster.

FIG. 5 is a schematic side view showing the structure of an electro-optic probe used in a conventional electro-optic sampling oscilloscope. In this figure, reference numeral 4 denotes an electro-optical probe which, when a laser beam is incident on the electro-optical crystal in a state where an electric field generated by a signal under measurement is applied to the electro-optical crystal, polarizes the laser beam. The signal to be measured is detected based on the principle that the state changes.

In the electro-optical probe 4, reference numeral 5 is a metal pin having a tapered tip portion, which is brought into contact with a signal line (not shown). The metal pin 5 serves to facilitate the action of an electric field by the signal under measurement transmitted through the signal line on the electro-optic crystal 7 described later. Reference numeral 6 is a disk-shaped insulator, and the end of the metal pin 5 is attached to the center of the back surface thereof. That is, the metal pin 5
It is held by the insulator 6. The electro-optic crystal 7 is B
SO (Bi ₁₂ SiO ₂₀ ) is formed into a cylindrical shape,
It has an optical property that its refractive index is changed by the Pockels effect, which is a first-order electro-optical change, according to an electric field coupled through the metal pin 5.

Reference numeral 8 is a reflecting mirror, which is a dielectric multilayer film mirror deposited on the back surface of the electro-optic crystal 7. The reflecting mirror 8 reflects the laser light La that has passed through the electro-optic crystal 7. The electro-optic crystal 7 is bonded to the surface of the insulator 6 via the reflecting mirror 8.

Reference numeral 9 denotes a substantially cylindrical case, which has a cylindrical cylindrical portion 9b and a tip portion 9a formed in a tapered shape at one end of the cylindrical portion 9b and having a through hole formed along the axis. And are integrally formed. The metal pin 5, the insulator 6, the electro-optic crystal 7, and the reflecting mirror 8 are housed in the tip portion 9a.

Reference numeral 10 is a polarization maintaining optical fiber for connecting the connector 11 and a laser generator (not shown).
The laser generator generates a linearly polarized laser beam La. Further, in the connector 11, the laser light La emitted from the emitting end 11 a of the connector 11 is electro-optical crystal 7 and the reflecting mirror 8.
It is arranged at a position where it is incident perpendicularly to. 12
Is a collimator lens arranged on the left side of the connector 11 and converts the laser light La into parallel light.

Reference numeral 13 denotes a polarization beam splitter disposed on the left side of the collimator lens 12, which linearly advances the polarization component of the laser light La parallel to the paper surface and at the same time is perpendicular to the paper surface. The polarized light component of is bent 90 degrees with respect to the straight direction of the laser light La and goes straight.
Reference numeral 14 is a Faraday element disposed on the left side of the polarization beam splitter 13, and rotates the polarization of the laser light La transmitted through the polarization beam splitter 13 by 45 degrees with respect to the paper surface.

A half-wave plate 15 is arranged on the left side of the Faraday element 14 so that the crystal axis azimuth is inclined by 22.5 degrees, and the polarized light rotated by the Faraday element 14 is oriented with respect to the paper surface. Make them parallel. Reference numeral 16 denotes a polarization beam splitter disposed on the left side of the half-wave plate 15, and has the same configuration as the polarization beam splitter 13. Reference numeral 17 denotes a wave plate disposed on the left side of the polarization beam splitter 16, which is a laser beam La transmitted through the polarization beam splitter 16.
By adjusting the intensity balance of the S / N (Signal / Nois) of the output signal of the electro-optical probe 4 finally obtained.
Adjust e).

Reference numeral 18 denotes a first photodiode arranged above the polarization beam splitter 16, and the first laser beam La is split by the polarization beam splitter 16.
Is converted into an electric signal S1 and output to a differential amplifier (not shown). Reference numeral 19 denotes a second photodiode disposed above the polarization beam splitter 13, which converts the laser light La branched by the polarization beam splitter 13 into a second electric signal S2, which is not shown in the figure. Output to the dynamic amplifier.

In the above structure, the metal pin 5 shown in FIG.
When the tip end of is contacted with a signal line (not shown), an electric field corresponding to the level of the signal under measurement transmitted through the signal line is coupled with the electro-optic crystal 7. As a result, the refractive index of the electro-optic crystal 7 changes according to the strength of the electric field. In this state, when the laser light La is emitted from a laser light generator (not shown), the laser light La is emitted from the emission end 11a of the connector 11, and then the collimator lens 12, the polarization beam splitter 13, and the Faraday element 14 are emitted. , 1/2 wave plate 15, polarization beam splitter 16 and wave plate 17
Is incident on the surface of the electro-optic crystal 7 via.

As a result, the polarization state of the laser light La propagating inside the electro-optic crystal 7 changes. Then, the laser light La having undergone the polarization change is reflected by the reflecting mirror 8, then emitted from the surface of the electro-optic crystal 7, and branched by the polarization beam splitter 16. The one branched laser beam La is converted into a first electric signal S1 by the first photodiode 18, and the first electric signal S1 is converted into the first electric signal S1.
Are input to the differential amplifier.

The other laser beam La split by the polarization beam splitter 16 is split by the polarization beam splitter 13 in the direction of the second photodiode 19 and then by the second photodiode 19 a second electric signal. Converted to S2. Then, the second electric signal S2 is
Input to the differential amplifier. Thereby, in the differential amplifier, after the first electric signal S1 and the second electric signal S2 are differentially amplified, the differentially amplified signal is output as the output signal of the electro-optical probe 4 by the electro-optical sampling oscilloscope. Input to the input terminal of. As a result, the waveform of the signal under measurement transmitted through the signal line is displayed on the display unit of the electro-optical sampling oscilloscope.

[0015]

By the way, in the above-mentioned conventional electro-optical sampling oscilloscope,
A direct detection system configuration is adopted in which the polarization state of the laser light La that has undergone polarization change is directly detected by the first photodiode 18 and the second photodiode 19. However, in the electro-optic sampling oscilloscope described above, in order to realize the direct detection method, the collimator lens 12 and the polarization beam splitter 1
3, the Faraday element 14, the half-wave plate 15, the polarization beam splitter 16, and the wavelength plate 17 are used, so that the optical system becomes complicated and the device becomes large. The present invention has been made under such a background, and an object thereof is to provide an electro-optical sampling oscilloscope capable of simplifying the configuration of an optical system and further downsizing the apparatus.

[0016]

According to a first aspect of the present invention, a light emitting means for generating a reference laser beam and a signal to be measured are provided.
The generated electric field is applied, and the
An electro-optic crystal with a changing folding rate and a back surface of the electro-optic crystal.
A reflecting mirror provided on the surface and adjacent to the reflecting mirror
The reflector and the reference laser light are converted into parallel light and
Irradiate the surface of the electro-optic crystal and the reflector in parallel with the line light.
On the other hand, it passes through the electro-optic crystal and is reflected by the reflecting mirror.
Signal light that has been incident and is reflected by the reflection plate
A laser that combines and collects the emitted reference light and emits it as combined light.
And a detector for detecting a signal under measurement based on the combined light.
Output means . In addition, claim 2
In the electro-optical sampling oscilloscope according to claim 1, the invention described in (1) is a method in which a light source is incident from the light emitting means.
While emitting the quasi-laser light toward the lens,
Directionality of emitted combined light incident from the detector toward the detection means
It is characterized by further comprising a coupler . According to a third aspect of the present invention, a light emitting means for generating a reference laser beam and an electric field generated by a signal under measurement are applied,
An electro-optical crystal whose refractive index changes according to the intensity of the
Converts the reference laser light into parallel light and forwards part of the parallel light.
A first lens for irradiating the electro-optic crystal, and the first lens
And the electro-optic crystal are placed opposite to each other,
Passes through the signal light that is transmitted and incident and the electro-optic crystal
Reference light that has been incident without
A second lens that emits light and a signal to be measured based on the combined light.
And a detection means for detecting the signal.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION <First Embodiment> An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a main part of an electro-optical sampling oscilloscope according to the first embodiment of the present invention. The electro-optic sampling oscilloscope shown in this figure detects a signal under measurement by homodyne detection.

In this figure, 20 is a light emitting circuit provided in the main body of an electro-optical sampling oscilloscope (not shown), and emits the reference laser beam La0 to one end face of the optical fiber 21. Reference numeral 22 denotes a directional coupler, which emits the reference laser light La0 incident through the optical fiber 21 to one end surface of the optical fiber 23, and outputs a later-described signal light La3 incident through the optical fiber 23. The light is emitted to one end surface of the optical fiber 24.

Reference numeral 25 is an electro-optical probe, and as described above, when a laser beam is incident on the electro-optical crystal in a state where an electric field generated by a signal under measurement is applied to the electro-optical crystal, The signal to be measured is detected based on the principle that the polarization state of the laser light changes.
In the electro-optic probe 25, 26 is a lens, which converts the reference laser light La0 emitted from the other end surface of the optical fiber 23 into parallel light, and the signal light L described later.
The a1 and the reference light La2 are condensed and emitted to the other end surface of the optical fiber 23 as the signal light La3.

Reference numeral 27 is a metal pin, 28 is an electro-optic crystal, and 29 is a reflecting mirror. These metal pins 2
7, the electro-optic crystal 28 and the reflecting mirror 29 have the same configuration as the metal pin 5, the electro-optic crystal 7 and the reflecting mirror 8 shown in FIG. That is, the electro-optic crystal 28 has an optical property that its refractive index is changed by the Pockels effect, which is a first-order electro-optic change, according to the electric field due to the signal under measurement coupled via the metal pin 27. ing.
The reflecting mirror 29 is vapor-deposited on the back surface of the electro-optic crystal 28, and reflects the reference laser light La0 that has passed through the lens 26 as the signal light La1.

Reference numeral 30 denotes a reflecting plate provided in parallel with the reflecting mirror 29, and reflects the standard laser beam La0 transmitted through the lens 26 as the reference beam La2. Reference numeral 31 denotes a dummy optical circuit that is provided between the lens 26 and the reflection plate 30 and is provided in parallel with the electro-optical crystal 28 (see FIG. 2), and is made of, for example, glass. Here, the difference between the round-trip optical path length from the other end surface of the optical fiber 23 to the reflecting mirror 29 and the round-trip optical path length from the other end surface of the optical fiber 23 to the reflector plate 30 is half a wavelength. At half wavelength, high sensitivity is obtained. Note that the difference between the two round-trip optical path lengths does not necessarily have to be a half wavelength. Further, as shown in FIG. 2, the dummy optical circuit 31 is formed so that the sectional area of the dummy optical circuit 31 and the sectional area of the electro-optic crystal 28 have the same area. This is the electro-optical crystal 28 and the dummy optical circuit 31.
This is because the reference laser beam La0 is evenly transmitted.

A light receiving circuit 32 receives the signal light La3 incident through the optical fiber 24, and has an optical / electrical conversion function of converting the signal light La3 into an electric signal. This electric signal is a signal corresponding to the signal under measurement. Further, as the above-mentioned optical fibers 21, 23 and 24, it is desirable to use polarization maintaining optical fibers.

In the above structure, the metal pin 2 shown in FIG.
When the tip of 7 is brought into contact with a signal line (not shown), an electric field corresponding to the level of the signal under measurement transmitted through the signal line is coupled with the electro-optic crystal 28. As a result, the refractive index of the electro-optic crystal 28 changes according to the strength of the electric field. In this state, when the reference laser beam La0 is emitted from the light emitting circuit 20, the reference laser beam La0 is guided to the optical fiber 23 via the optical fiber 21 and the directional coupler 22. Then, the reference laser beam La0 is emitted from the optical fiber 2
After being emitted from the other end surface of 3, the light passes through the lens 26.
At this time, the reference laser light La0 is converted into parallel light.

Then, the reference laser beam La0 which is a parallel light beam
Propagates toward the reflecting mirror 29 and the reflecting plate 30 through the electro-optical crystal 28 and the dummy optical circuit 31 as shown in FIG. Here, when the reference laser beam La0 is circularly polarized light,
The x-component x1 and the y-component y1 of the reference laser light La0 propagating through the electro-optic crystal 28 are expressed by the following equation (1) and (1), where ω is the angular frequency of the reference laser light La0, t is time, and A is a constant. It is represented by the formula 2). x1 = A · sin (ωt) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1) y1 = A ・ cos (ωt) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (2)

Further, the polarization state of the reference laser beam La0 propagating inside the electro-optic crystal 28 changes. During propagation, the crystal axis of the electro-optic crystal 28 is adjusted so that the phase of the x component x1 of the reference laser beam La0 does not change and the phase of the y component y1 changes. Then, the reference laser beam La0 that has undergone the polarization change is reflected by the reflecting mirror 29 as the signal beam La1 and then passes through the lens 26 to transmit the optical fiber 23.
Is incident on the other end surface of. Here, the x component x1 'in the signal light La1 is expressed by the following equation (3), where m is a coefficient determined by the number of reflections and the reflection state, and
The y component y1 'is defined by the following (4) when the phase change amount is Δφ.
It is represented by a formula. x1 ′ = A · sin (ωt + mπ) ···· (3) y1 ′ = A · cos (ωt + mπ + Δφ) ··· (4)

On the other hand, the reference laser beam La0 propagating through the dummy optical circuit 31 is reflected as the reference beam La2 by the reflecting plate 30 without undergoing polarization change, and then passes through the lens 26 to pass through the optical fiber 23. It is incident on the other end surface. Here, the frequency of the signal light La1 and the frequency of the reference light La2 have the same value. Further, the phase of the signal light La1 and the phase of the reference light La2 are opposite to each other, like a signal in a balanced light receiving circuit used for coherent optical fiber communication. Here, the reference light La
The x component x2 ′ in 2 is represented by the following equation (5), where n is an integer, while the y component y2 ′ is represented by the following (6).
It is represented by a formula. x2 '= A * sin (ωt + nπ) ... (5) y2' = A * cos (ωt + nπ) ... (6)

As a result, in the optical fiber 23,
The signal light La1 and the reference light La2 are combined to generate a signal light La3.
Is generated. Here, the signal light La3 is light of a signal indicating a change in the polarization plane of the signal light La1 propagating in the electro-optic crystal 28, in other words, light of a signal corresponding to a change in the signal under measurement. . Here, the y component y3 in the signal light La3 is expressed by the following equation (7). y3 = y1 '+ y2' (7) Then, by substituting the equations (4) and (5) into the right side of the equation (7), the following equation is obtained. Equation (8) is derived. y3 = A · cos (ωt + mπ + Δφ) + 0.25 · cos (ωt + nπ) = A · 2 · cos (ωt + (m + n) π / 2 + Δφ / 2) · cos (Δφ / 2 + (m−n) · π / 2) (8)

In the above equation (8), A · 2 · c in the preceding paragraph
os (ωt + (m + n) π / 2 + Δφ / 2) represents the baseband signal (carrier) component of the reference laser light La0, and cos (Δφ / 2 + (m−n) · π /
2) represents the envelope of the signal component under measurement.
Further, as can be seen from the above cos (Δφ / 2 + (m−n) · π / 2), the condition for maximum sensitivity to a slight variation Δφ is that the phase difference between the signal light La1 and the reference light La2 is Since it is a half wavelength (π + 2 · k · π (k is an integer)), it is expressed by the following equation (9). (M−n) · π / 2 = π / 2 + k · π (9)

The signal light La3 is guided to the light receiving circuit 32 via the directional coupler 22 and the optical fiber 24, and then converted into an electric signal by the light receiving circuit 32. As a result, the waveform of the signal under measurement transmitted through the signal line is displayed on the display unit of the electro-optical sampling oscilloscope.

As described above, according to the electro-optic sampling oscilloscope according to the first embodiment, the polarization beam splitter 13, which is necessary for the direct detection method,
Since the polarization beam splitter 16 and the like (see FIG. 5) are unnecessary, the configuration of the optical system can be simplified as compared with the conventional electro-optical sampling oscilloscope, and the device can be downsized.

<Second Embodiment> Next, the configuration of an electro-optic sampling oscilloscope according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, FIG.
The same reference numerals are given to the portions corresponding to the respective portions, and the description thereof will be omitted. In FIG. 3, the directional coupler 2 shown in FIG.
Instead of 2 and the optical fiber 24, a lens 33 and an optical fiber 34 are provided. Further, the electro-optic sampling oscilloscope shown in FIG. 3 has a configuration in which the reflecting mirror 29 and the reflecting plate 30 shown in FIG. 1 are not provided.

The lens 33 shown in FIG. 3 is the electro-optic crystal 2
8 and the dummy optical circuit 31 are arranged on the right side of the figure, and the signal light La1 ′ transmitted through the electro-optical crystal 28 and the reference light La2 ′ transmitted through the dummy optical circuit 31 are condensed to generate the signal light. It is emitted to one end surface of the optical fiber 34 as La3 '. That is, the lens 33 is arranged to face the lens 26, and the electro-optical crystal 28 and the dummy optical circuit 31 are arranged between the lens 26 and the lens 33. The optical fiber 34 receives the signal light La3 ′ from the light receiving circuit 3
Lead to 2. It is desirable to use a polarization-maintaining optical fiber as the optical fiber 34.

The optical path length from the other end surface of the optical fiber 21 to the one end surface of the optical fiber 34 via the lens 26, the electro-optic crystals 28 and 33, and the other end surface of the optical fiber 21 to the lens 26, The difference from the optical path length to the one end surface of the optical fiber 34 via the dummy optical circuit 31 and the lens 33 is half the wavelength. When the difference is half wavelength, high sensitivity is obtained. Therefore, the refractive index of the dummy optical circuit 31 is set to a value such that the difference between the optical path lengths becomes a half wavelength. The difference between the two optical path lengths does not necessarily have to be a half wavelength.

In the above structure, the metal pin 2 shown in FIG.
When the tip end of 7 is brought into contact with a signal line (not shown), an electric field corresponding to the level of the signal under measurement transmitted through the signal line is coupled to the electro-optic crystal 28 in the same manner as the above-described operation. .
In this state, the reference laser beam La is emitted from the light emitting circuit 20.
When 0 is emitted, the reference laser light La0 is emitted from the optical fiber 2
Guided to 1. Then, the reference laser beam La0 is emitted from the other end surface of the optical fiber 21 and then passes through the lens 26. At this time, the reference laser light La0 is converted into parallel light.

Then, the reference laser beam La0 which is a parallel light beam
Passes through the electro-optic crystal 28 and the dummy optical circuit 31. As a result, the polarization state of the signal light La1 propagating inside the electro-optic crystal 28 changes. Then, the signal light La1 that has undergone the polarization change is transmitted as the signal light La1 ′, then passes through the lens 33 and is incident on one end surface of the optical fiber 34.

On the other hand, the standard laser beam La0 propagating through the dummy optical circuit 31 is transmitted as the reference beam La2 'without being changed in polarization, and then is transmitted through the lens 33 to be incident on one end face of the optical fiber 34. To be done. Here, the frequency of the signal light La1 ′ and the frequency of the reference light La2 ′ have the same value.

As a result, in the optical fiber 34,
The signal light La1 ′ and the reference light La2 ′ are combined to generate the signal light L
a3 'is generated. Here, the signal light La3 ′ is light of a signal indicating a change in the polarization plane of the signal light La1 ′ propagating through the electro-optic crystal 28, in other words, a light of a signal corresponding to the change of the signal under measurement. Is.

Then, the signal light La3 is guided to the light receiving circuit 32 through the optical fiber 34, and thereafter, the light receiving circuit 3
2 is converted into an electric signal. As a result, the waveform of the signal under measurement transmitted through the signal line is displayed on the display unit of the electro-optical sampling oscilloscope.

As described above, according to the electro-optic sampling oscilloscope according to the second embodiment described above, since the lens 33 is provided, the directional coupler 22, the reflecting mirror 29 and the reflecting plate shown in FIG. 1 are provided. Since 30 is unnecessary, the configuration can be simplified as compared with the electro-optical sampling oscilloscope according to the first embodiment.

<Third Embodiment> FIG. 4 is a view showing the arrangement of the main parts of an electro-optical sampling oscilloscope according to the third embodiment of the present invention. In this figure, parts corresponding to those in FIG. In FIG. 5, an optical waveguide device 100 is provided instead of the directional coupler 22 shown in FIG. The optical waveguide device 100 shown in FIG. 4 has a function of branching / coupling optical signals similarly to the directional coupler 22 (see FIG. 1). In this optical waveguide device 100, 100a
Is an optical waveguide connected to the other end of the optical fiber 21, and guides the reference laser light La0 to the optical branching / coupling portion 100b. This optical branching / coupling portion 100b is used for the reference laser light La0
On the other hand, the signal light La1 and the reference light La2 are coupled (combined) while being branched, and this is output as the signal light La3.

An optical waveguide 100c guides the signal light La1 branched by the optical branching / coupling portion 100b to the optical fiber 23, while the signal light La3 incident through the optical fiber 23 is directed to the optical branching / coupling portion 100b. Lead. 100d
Is an optical waveguide provided alongside the optical waveguide 100c, and is not used in the example of FIG. An optical waveguide 100e guides the signal light La3 branched by the optical branching / coupling unit 100b to the optical fiber 24.

In the above structure, the metal pin 2 shown in FIG.
When the tip of 7 is brought into contact with a signal line (not shown), an electric field corresponding to the level of the signal under measurement transmitted through the signal line is coupled with the electro-optic crystal 28. As a result, the refractive index of the electro-optic crystal 28 changes according to the strength of the electric field. In this state, when the reference laser beam La0 is emitted from the light emitting circuit 20, the reference laser beam La0 is guided to the optical branching / coupling portion 100b via the optical fiber 21 and the optical waveguide 100a. The reference laser beam La0 is branched by the optical branching / coupling unit 100b, and then the optical waveguide 100c.
Through the optical fiber 23. Then, the reference laser beam La0 is emitted from the other end surface of the optical fiber 23 and then passes through the lens 26. At this time, the reference laser light L
a0 is converted into parallel light.

Then, the reference laser beam La0 which is parallel light
Propagates through the electro-optic crystal 28 and the dummy optical circuit 31 toward the reflecting mirror 29 and the reflecting plate 30. Further, the polarization state of the reference laser beam La0 propagating inside the electro-optic crystal 28 changes in the same manner as the above-mentioned operation. The reference laser beam La0 that has undergone polarization change is reflected by the reflecting mirror 2
After being reflected as signal light La1 by the lens 9,
And is incident on the other end surface of the optical fiber 23.

On the other hand, the standard laser beam La0 propagating through the dummy optical circuit 31 is reflected as the reference beam La2 by the reflection plate 30 without undergoing polarization change, and then passes through the lens 26 to pass through the optical fiber 23. It is incident on the other end surface. Here, the frequency of the signal light La1 and the frequency of the reference light La2 have the same value. As a result, in the optical fiber 23, the signal light La1 and the reference light La2 are multiplexed to generate the signal light La3. Here, the signal light La3 is light of a signal indicating a change in the polarization plane of the signal light La1 propagating in the electro-optic crystal 28, in other words, light of a signal corresponding to a change in the signal under measurement. .

Then, the signal light La3 is supplied to the optical waveguide 1.
After being guided to the optical branching / coupling portion 100b via 00c, it is guided to the optical waveguide 100e by the optical branching / coupling portion 100b. Further, the signal light La3 is guided to the light receiving circuit 32 via the optical fiber 24 and then converted into an electric signal by the light receiving circuit 32. As a result, the waveform of the signal under measurement transmitted through the signal line is displayed on the display unit of the electro-optical sampling oscilloscope.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. However, it is included in the present invention. For example, in the electro-optic sampling oscilloscope according to the first and second embodiments described above, the example in which BSO is used as the electro-optic crystal 28 has been described, but the present invention is not limited to this, and LN ( LiNbO
₃ ), CdTe or BTO (Bi ₁₂ TiO ₂₀ ) may be used.

Further, in the electro-optic sampling oscilloscope according to the first and second embodiments described above,
When the electric field due to the measured signal sufficiently acts on the electro-optic crystal 28, the metal pin 27 may be omitted.

Further, in the electro-optic sampling oscilloscope according to the above-mentioned first, second and third embodiments, the example in which the dummy optical circuit 31 is provided has been described, but the lens 26 is not provided without the dummy optical circuit 31.
The configuration may be such that the space between the reflector and the reflection plate 30 (lens 33) is spatially coupled.

Further, in the electro-optic sampling oscilloscope according to the above-mentioned first, second and third embodiments, an example in which the cross-section area of the electro-optic crystal 28 and the cross-section area of the dummy optical circuit 31 shown in FIG. As described above, it is not always necessary to equalize both cross-sectional areas, and it is sufficient that the reference laser beam La0 is transmitted through both the electro-optic crystal 28 and the dummy optical circuit 31.

[0050]

As described above, according to the present invention,
Since the polarization beam splitter or the like used in the conventional electro-optic sampling oscilloscope is not necessary, the structure of the optical system can be simplified, and the size of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part of an electro-optical sampling oscilloscope according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA shown in FIG.

FIG. 3 is a diagram showing a configuration of a main part of an electro-optical sampling oscilloscope according to the second embodiment.

FIG. 4 is a diagram showing a configuration of a main part of an electro-optical sampling oscilloscope according to the third embodiment.

FIG. 5 is a diagram showing a configuration of an electro-optic probe in a conventional electro-optic sampling oscilloscope.

[Explanation of symbols]

20 Light emitting circuit 22 Directional coupler 25 Electro-optic probe 26 lenses 28 Electro-optic crystal 29 Reflector 30 reflector 31 Dummy optical circuit 32 light receiving circuit 33 lenses 100 Optical waveguide device

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Kikuchi 4-19-7 Kamata, Ota-ku, Tokyo Within Ando Electric Co., Ltd. (72) Nobuichi Banjo 4-19-7 Kamata, Ota-ku, Tokyo Ando Electric Co., Ltd. (72) Inventor Yoshio Endo 4-19-7 Kamata, Ota-ku, Tokyo Ando Electric Co., Ltd. (72) Inventor Mitsuru Shinagawa 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nihon Telegraph Telephone Co., Ltd. (72) Inventor Tadao Nagatsuma 3-19-3 Nishishinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Junzo Yamada 3-19-3 Nishishinjuku, Shinjuku-ku, Tokyo (56) Reference JP 64-18070 (JP, A) JP 6-34675 (JP, A) JP 63-300970 (JP, A) JP 7- 225108 (JP, A) -209396 (JP, A) JP 9-292415 (JP, A) JP 63-151869 (JP, A) JP 6-258351 (JP, A) (58) Fields investigated (Int.Cl . ⁷ , DB name) G01R 13/00-13/42 G01R 31/302 G01R 15/24

Claims (3)

(57) [Claims] 1. A light emitting means for generating a reference laser beam and an electric field generated by a signal under measurement are applied, and the intensity of the electric field is increased.
An electro-optical crystal whose refractive index changes according to the degree, a reflecting mirror provided on the back surface of the electro-optical crystal, a reflecting plate disposed adjacent to the reflecting mirror, and the reference laser beam converted into parallel light. , The parallel light
While irradiating the surface of the electro-optic crystal and the reflector in parallel,
After passing through the electro-optic crystal, it is reflected by the reflecting mirror and enters.
The reflected signal light and the incident light reflected by the reflector are incident.
An electro-optical sampling oscilloscope, comprising: a lens that combines and collects illumination light and emits the combined light, and a detection unit that detects a signal under measurement based on the combined light . 2. The reference laser light incident from the light emitting means
Light is emitted toward the lens, while it is incident from the lens
A directional coupler that emits the combined light toward the detection means is added.
Electro-optic sampling oscilloscope according to claim 1, characterized in that it comprises a. 3. A light emitting means for generating a reference laser beam and an electric field generated by a signal under measurement are applied, and the intensity of the electric field is increased.
A part of the parallel light that converts the reference laser light into parallel light and the electro-optic crystal whose refractive index changes according to the degree
A first lens for irradiating the electro-optic crystal with the first lens, and the first lens and the electro-optic crystal are disposed so as to face each other.
Signal light and electro-optical coupling incident through the aero-optical crystal
The incident reference light is combined and condensed without passing through the crystal.
An electro-optic sampling oscilloscope comprising: a second lens that emits as combined light; and a detection unit that detects a signal under measurement based on the combined light .