JPS6211834A - Waveguide type optical a/d converter - Google Patents

Abstract

PURPOSE:To execute an operation by using only one piece each of photoelectric converting element and optical fiber irrespective of the number of bits of a digital signal which is obtained in the end, by providing an optical branching means, a modulating element, and a P/S converting means on a substrate. CONSTITUTION:Y-shaped optical waveguides 25-27, Mach-Zehnder type optical waveguides 21-24 being light intensity modulating elements, optical waveguides 41, 41a-44 and 44a for executing an optical parallel/serial (P/S) conversion, and Y-shaped optical waveguides 45-47 for condensing the light which has been brought to the P/S conversion are formed on a substrate 10 of a waveguide type optical A/D converting part. Light from a semiconductor laser 14 is made to multiplex equally to four lights by the Y-shaped optical waveguides 25-27, modulated by the Mach-Zehnder type optical waveguides 21-24, and thereafter, brought to the P/S conversion by the optical waveguides 41, 41a-44 and 44a, condensed by the Y-shaped optical waveguides 45-47, and led into an optical fiber 16.

Description

Detailed Description of the Invention: Summary of the Invention An A/D converter generates a plurality of modulated lights representing applied analog physical quantities, and a serial converter that converts the plurality of parallel optical signals output from the A/D converter 1. A waveguide type optical A/D conversion device, which includes a P/S conversion section that converts the optical signal into an optical signal, and the P/S conversion section includes a leading waveguide branching at an angle twice the Bragg angle.

[Technical Field] The present invention relates to a waveguide type optical A/D conversion device that uses light to convert analog voltage signals and other analog physical quantities into digital signals representing values corresponding thereto.

[Prior Art] Waveguide type optical A/D converters that use light have attracted the attention of many people because they have a relatively simple configuration and can be expected to perform high-speed sampling (1 to 2 G samples/sec). There is. A representative example of a conventional waveguide type optical A/D converter is shown in Nishihara, Haruna, and Suhara, "Optical Integrated Circuits," 1st edition (1986-2-25), Ohmsha p., 358-361. For example, when trying to obtain a 4-bit digital signal, four optical signals are output from the substrate, so four photoelectric conversion elements are required to convert these optical signals into electrical signals.

To obtain an 8-bit digital signal, eight photoelectric conversion elements are required. When trying to guide the optical signal output from the board to the photoelectric conversion element using an optical fiber, 4
A problem arises in that one or eight optical fibers are required.If the optical transmission distance is long, the installation cost of the optical fibers becomes quite high.

[Object of the invention] An object of the present invention is to provide a waveguide type optical A/D conversion device that requires only one photoelectric conversion element and one optical fiber, regardless of the number of bits of the digital signal finally obtained. With the goal.

[Configuration and Effects of the Invention] The waveguide type optical A/D conversion device according to the present invention has a substrate whose optical characteristics change depending on the applied physical quantity; Branching means for branching into light; a plurality of modulation elements formed on the substrate and modulating the intensity of the single branched light to different degrees depending on the applied physical quantity; first optical waveguides each connected to the output side of the modulation element; part, a second optical waveguide part branched from the first optical waveguide part at a predetermined angle, and a first optical waveguide part.
includes a means for black diffracting the light propagating through the optical waveguide section and generating a pulsed surface acoustic wave that guides the diffracted light to the second optical waveguide section, which temporally serializes the plurality of lights output from the modulation element. P/S conversion means for converting into an optical signal;
means for condensing the P/S converted light; a photoelectric conversion element that converts the condensed light into an electrical signal representing its intensity; then = 3 - and discriminating the output signal of the photoelectric conversion element at a required level It is characterized by comprising a comparator.

A P/S conversion means is provided, which converts the plurality of lights output from the plurality of modulation elements into a temporally serial optical signal, so that this optical signal can be transmitted through a single optical fiber. I can do it.

One photoelectric conversion element that converts this optical signal into an electrical signal is also sufficient.

Further, in this invention, since a branching means for branching the light introduced into the substrate-lx into a plurality of lights is provided, it is possible to introduce light into the substrate through a single optical fiber. However, light from a light source such as a semiconductor laser may be directly optically coupled to the substrate.

Furthermore, in the P/S conversion means, the light propagates while being confined within the optical waveguide, so the spread of the light is suppressed.
Bragg diffraction by SAW is achieved with high efficiency, and a high-intensity optical digital signal can be obtained.

[Description of Embodiments] 1) A/D conversion device using a branching interferometric modulator This embodiment converts an analog voltage signal into a digital voltage signal.

In FIG. 1, Y-cut LiNbO3 having an electro-optic effect is used as the substrate IO of the waveguide type optical A/D converter. This substrate 10 is provided with 7-shaped optical waveguides 25 to 27 for equally splitting the input light into four beams. Four Matsuhatsu Enda type optical waveguides 21 that serve as light intensity modulation elements
~24. Optical waveguides 41.41a to 44.44a and P for optical parallel/serial (P/S) conversion
7-shaped optical waveguide 45 for condensing /S-converted light
~47 are formed.

Input light is generated from a semiconductor laser 14. The semiconductor laser is directly end face coupled to the input side (end face of the substrate 10) of the Y-shaped guide waveguide 25. Input light can be introduced into the Y-shaped leading waveguide 25 by guiding light from a light source using an optical fiber and optically coupling this optical fiber to the optical waveguide 25 through a suitable optical coupler or directly. achieved.

The Matsuhatsu Enda type optical waveguide 21 includes an input optical waveguide portion 21c, two branched optical waveguide portions 21a and 21b branched at equal angles from this optical waveguide portion 21c, and these optical waveguide portions 21a+' 2lb join together. It is composed of an output optical waveguide portion 21d. The other Matsuhatsu Enda type optical waveguides 22 to 24 have exactly the same configuration.

A pair of electrodes 31 are formed on the substrate 10 at positions on both sides of one branched optical waveguide portion 21b of the Matsuhatsu-Enda type optical waveguide 21. These electrodes 31 are electrically connected by a wiring pattern 35 to a pair of terminals 30 to which an analog voltage to be A/D converted is applied. Similarly,
A pair of electrodes 32 to 34 are also provided on both sides of one branched optical waveguide portion of the other Matsuhatsu Enda type leading waveguides 22 to 24, respectively, and are connected to the terminal 30. 1 pair of electrodes 3
The length of the overlapping portion with the branched optical waveguide portion 21b in between is 28L. This length is the length to which the analog voltage of the branched optical waveguide portion 21b is applied. Similarly.

The lengths of the overlapping portions of the other electrodes 32, 33.84 are set to 2L-2L, 2L-4L, and 23L=8L, respectively.

The input light introduced into the figure-7 optical waveguide 25 is equally demultiplexed by this optical waveguide 25. The two demultiplexed lights are split into two lights of equal intensity by the 7-shaped optical waveguides 26 and 27, respectively, and guided to the input optical waveguide portions of the four Matsuhatsu Enda-shaped optical waveguides 21-24.

In this way, nine lights of equal intensity are input to the Matsuhatsu Enda type optical waveguides 21 to 24.

The output ends of the output optical waveguide portions (21d, etc.) of the Matsuhatsu Enda type optical waveguides 21-24 are connected to the leading waveguides 41a-44a, respectively. An example of a substrate IDT is an interdigital transducer (abbreviated as IDT).
a is formed. As described later, a high frequency voltage is applied to the IDT 13 in a pulsed manner, and a pulsed surface acoustic wave (SAW) is generated from the IDT 13, and the substrate 10
We will continue to spread the word. The directions of the optical waveguides 41a to 44a and the arrangement of the IDT 13 are determined so that the light propagating through the optical waveguides 41a to 44a and the SAW satisfy Bragg diffraction conditions.

At points of interaction between the light propagating through the optical waveguides 41a-44a and the SAW, guide waveguides 41-44 for guiding the light diffracted by the SAW are branched from the optical waveguides 41a-44a. This divergence angle is equal to twice the Bragg angle. It is preferable to prevent light reflection from occurring at the ends of the optical waveguides 41a to 44a.

The guide waveguides 41 and 42 are connected to a figure-7 optical waveguide 46,
The optical waveguides 43 and 44 are connected to a figure-7 optical waveguide 47. These 7-shaped optical waveguides 46, 47 are further connected to a 7-shaped optical waveguide 45, and one diffracted light is collected. 7
The output side of the letter-shaped optical waveguide 45 is optically coupled to one optical fiber 16 . The other end of the optical fiber 16 is connected to an electrical processing section including a photoelectric-optical conversion element and a level discrimination circuit, which will be described later. Instead of the optical fiber 16, a photoelectric conversion element may be optically coupled directly to the optical waveguide 45.

Matsuha Tsuenda type optical waveguides 21 to 24. Y-shaped optical waveguides 25 to 27. Optical waveguides 41a, 41-44a,
The 4Q and 7-shaped optical waveguides 45 to 47 are formed, for example, on the substrate 10 using Ti sputtering and a lift-off method in a predetermined pattern to a thickness of 200 angstroms.

After this, the temperature was 970℃ for 1 hour and 5 hours, and the atmosphere was 0.
It can be produced by thermal diffusion under the conditions of □. The leading waveguides 21 to 27, 11 such as 41 to 47, have a diameter of 5 μm, and allow single mode light to propagate in directions horizontal and perpendicular to the substrate. The IDT 13 and the electrodes 31 to 34 have a two-layer structure of Ti and Ail and are manufactured by a normal lift-off method.

If the width and interval of each electrode of the IDT 13 is 2.5 μm, the Black angle is 0.82° when the wavelength of light is 0.29 μm.

Next, the modulation of light in the Matsuhatsu Enda type optical waveguide will be explained. Four Matsuhatsu Enda type optical waveguides 21 to 2
4 differs only in the length of the electrode pair.

Since the other configurations are exactly the same, the Matsuhatsu Enda type optical waveguide 21 will be described as a representative of these optical waveguides.

Input optical waveguide part 2 of Matsuha Tsuender type optical waveguide 21
The light propagating through 1c is divided into two branched optical waveguide sections 21a and 2.
1b, and these optical waveguide portions 21a, 2
1b, and is multiplexed at the output optical waveguide portion 21d. The length of the two branched optical waveguide portions 21a and 21b,
el, jl! 2 (the length from the branch point to the confluence point as shown by the broken line) is equal, the two lights propagating through the two-branch optical waveguide portions 21a and 21b are branched from one light. The phases match when the signals are combined in the output optical waveguide portion 21d. Therefore, if propagation loss is not considered, the intensity of light obtained at the output optical waveguide section 21d is equal to that at the input optical waveguide section 21c. Generally speaking, one-branch optical waveguide portion 21a
, 21b, if the phase difference between them is 2mπ (m is 0 or an integer) when the two lights propagated through the output optical waveguide section 21d are combined, the output optical waveguide section 21d will pass through the Matsuhatsu Enda type optical waveguide. Light having the same intensity as the light input to the wave path 21 (this is referred to as maximum intensity ■) is obtained l1ax. The fact that the phase difference between the two lights is 2 mπ is determined by the difference Δ between the lengths of the 1-branch optical waveguide portions 21 a and 2 l b = nil! When expressed as 2, it is expressed as quadratic.

Δp=m・(λo/n)...
(1) Here, n is the refractive index of the optical waveguide, and λ0 is the wavelength of light in vacuum.

If the difference Δ between the lengths of the branched optical waveguide portions 21a and 21b has the following relationship, then these optical waveguide portions 2+a, 2
When the light propagated through 1b is combined at the output optical waveguide portion 21d, the phase difference thereof becomes (2m+1)π.

At Δ=[(2m+1)/2] ・(λo/n
)...(2) In this case, since two lights of opposite phases are superimposed, the light intensity obtained at the output optical waveguide portion 21 (1) becomes 0.

Now, since L iN b 03 is a crystal with an electro-optic effect, its refractive index changes when an electric field is applied. Electric field E (E=V/d) in the Z direction of the substrate 10.

When V: applied voltage, d: distance between a pair of electrodes),
The refractive index changes by Δn=-(n/2)·γ·E. Here, 733 is an electro-optic constant. The phase of light propagating through the portion where the refractive index has changed is Δφ−(2π/λ.

)・(・(−n/2)・γ33・E changes. Here, it is the length of the part to which the electric field is applied. In the Matsuhatsu Enda type optical waveguide 21, it is marked as =, and in other Matsuhatsu Enda type optical waveguides J knee 2L and 4L on 22, 23 and 24 respectively.

It becomes 8L.

The voltage required to change the phase difference of two lights propagating through the branched optical waveguide portions (21a, 21b, etc.) by π is called a half-wavelength voltage V.sub.2. Since the four Matsuhatsu π-type optical waveguides 21 to 24 differ in length, the half-wavelength voltage V also differs. If the half-wave voltage of the Matsuhatsu Enda type leading wave π path 21 is V, then M1. The half-wavelength voltages of the Notsuta-type optical waveguides 22, 23, and 24 are respectively V/2. V/4. It becomes V/8. Like this π π
π, four Matsuhatsu Enda type optical waveguides 21 to 24
are modulation elements with different sensitivities and dynamic ranges.

FIG. 2 shows the voltage applied between the electrodes 31 and the light obtained at the output optical waveguide portion 21 [I] when the difference in length Δ°C between the one-branch optical waveguide portions 21a and 21b satisfies equation (1). It shows the relationship with strength. As described in , the phase of the light changes depending on the applied voltage in one branch optical waveguide section 2lb, so the output light intensity is I-I eos''
(Δφ/2).

1laX π of the maximum intensity I when the applied voltage is ±2mV
Iax
When light is obtained and the applied voltage is ±(2m+1)V, the intensity of the light becomes 0.

FIG. 3 shows the voltage applied between the electrodes 31 and the intensity of light obtained in the output optical waveguide 21d when the length difference Δ( of the two-branch optical waveguide portions 21a and 21b satisfies Equation (2)). It shows the relationship that the applied voltage is ±(2m+1)V
When the light π of maximum intensity I
Iax is obtained and the light intensity π becomes 0 when the applied voltage is ±2 mV.

Figure 4 shows the output light intensity (vertical axis) to the analog voltage applied to terminal 30 (
(horizontal axis). The applied voltage is conveniently divided into a number of discrete regions A-P.

The light intensity curve is shown using the electrode length as a parameter for convenience.

That is, L is the output light intensity of the Matsuhatsu Enda type optical waveguide 21, and 2L, 4L, and 8L are the output light intensity of the optical waveguide 22, respectively.
, 23.24. When these output lights are converted into electrical signals by a photoelectric conversion element, the output signal curve also has a shape that is the same as or inverted from this light intensity curve.

A photoelectric conversion element output signal with such a waveform.

11 with threshold level I of I /2
8X
When the S level discrimination circuit performs level discrimination and binarizes it.

A 4-bit digital signal representing an analog voltage is obtained as shown in the lower half of FIG. It will be readily understood that the analog voltage signal applied across terminals 30 is thus uniquely converted into a 4-bit digital signal. The accuracy of A/D conversion is the width of the above-mentioned divided voltage regions.

It goes without saying that even under conditions where the characteristics shown in Figure 2 are obtained (that is, when Δ(satisfies equation (1)), a 4-bit digital signal representing the analog applied voltage is similarly obtained. Also, the discrimination level may be any level, and discrimination may be made at a plurality of levels.

Now, returning to FIG. 1, in the process in which the pulsed SAW generated from the IDT 13 propagates through the substrate 10, it first interacts with the output light of the Matsuhatsu Enda type guide waveguide 24 propagating through the guide wavepath 44a, and this output light diffract. The diffracted light travels to the optical waveguide 44. At this time, the SAW does not interact with the output light of the Matsuhatsu Enda type optical waveguides 23 to 21 that propagates through the other optical waveguides 43a to 41a. Next, the SAW interacts with the output light of the Matsuhatsu Enda type optical waveguide 23 propagating through the optical waveguide 43a and diffracts this output light.

This diffracted light travels to the optical waveguide 43. In this way, 4
The output lights of the three Matsuhatsu Enda type optical waveguides 24 to 21 are sequentially diffracted by the SAW, so that they become serial optical signals on the time axis. Therefore, the figure-7 optical waveguides 45 to 4
Serial diffracted light focused by 7 = 15
- Transmission via a single optical fiber becomes possible.

Since the light that interacts with the SAW is confined in the optical waveguides 41a to 44a, it does not spread much and most of the light interacts with the SAW.
It is also noteworthy that high efficiency P/S conversion is achieved.

In the case where the substrate 10 is 2-cut L　iN　b　03.

Branch optical waveguide portion 21 of Matsuha Tsuenda type optical waveguide 21
Electrodes 31 are provided on both a and 21b. Electrode 3
When a voltage is applied between 1 and 2, the branched optical waveguide portion 218°2
The refractive index increases on one side of 1b and decreases on the other, creating a phase difference in the light propagating through them, and the intensity of the light output from the output optical waveguide portion 21d is modulated in the same way as in the above case. . The same applies to the other Matsuhatsu Enda type optical waveguides 22 to 24.

Analog physical quantities that are converted into digital signals are not limited to voltage. A sensor for light, temperature, pressure, humidity, gas concentration, etc. may be provided and this output voltage may be applied between the terminals 30,
It is also possible to use optical waveguide materials and substrate materials whose refractive index, etc. of the Matsuhatsu-Enda optical waveguide changes directly depending on these physical quantities, and it is also possible to load such materials into the optical waveguide. A light modulation element can also be constructed by changing the refractive index and the like. .

Of course, the number of Matsuhatsu Enda type optical waveguides formed on the substrate can also be set arbitrarily. In addition to the optical intensity modulation element using the above-mentioned Matsuhatsu Enda type optical waveguide and the Fapley-Bello type described later, examples of optical intensity modulation elements include those using, for example, a directional coupler between optical waveguides; No. 118178 (JP 511-202408
Examples include those using a waveguide optical beam splitter as disclosed in Japanese Patent Publication No.

The creation of optical waveguides on the substrate can also be done by various methods.

All of the light propagating through the optical waveguides 41a to 44a is SAW
It is not necessarily biased by The light propagating through these optical waveguides 41a to 44a without being deflected is SA again.
For deflection by W, optical waveguides 41a to 44a
is extended, another branch is provided on this extension, and a second IDT that generates a second SAW directed toward these branches is provided on the substrate 10. Then, the polarized light directed toward the optical waveguide 44 and the light polarized at the other branching portion are simultaneously deflected (diffraction) by the two SAWs. The same applies to the other optical waveguides 43 to 41 and the polarization of light at another branch section corresponding to them. In this way even higher deflection efficiency can be obtained.

2) A/D conversion device using Fapley-Perot type modulators In this embodiment, the waveguide type optical A/D conversion section is composed of four Fapley-Perot type modulators.

In FIG. 5, the same components as those shown in FIG. 1 are given the same reference numerals.

On the platen 10, instead of the Matsuhatsu Enda type leading waveguide,
Four optical waveguides 51 to 54 are formed consecutively and parallel to the four output ends of the 7-shaped optical waveguide 28, 27. These leading waveguides 51 to 54 are optical waveguides 4+a to 4.
It is bonded to 4a. A pair of electrodes 31 to 34 are provided on both sides of each of these optical waveguides 51 to 54, respectively. In this embodiment, the electrode 31 of the optical waveguide 51
The length of the overlapping portion of the optical waveguide 54 is the longest, and that of the electrode 34 of the optical waveguide 54 is the shortest. The lengths of the mutually overlapping portions of these electrodes 31, 32, 33, and 34 are 8L, 4L, and 2L.

It is L. Grooves 68 for configuring a resonator so as to cross the vicinity of both ends of each of the optical waveguides 51 to 54.
．． 89 are formed respectively. Further, phase adjustment electrodes 61 to 64 are formed on both sides of each leading waveguide 51 to 54 and in a portion other than the electrodes 31 to 34.

The optical waveguides 25 to 2 are formed on the substrate IO by thermal diffusion of Ti.
7, 51-54.41.41a-44.44a, 4
6 to 48 are formed.

Thereafter, resist is uniformly applied again to the surface I- of the substrate 10 and exposed except for the areas where the grooves 68 and 69 are to be formed, so that the resist remains only on these areas. Then, when Ti is sputtered to a thickness of about 3 μm and the resist shown in L is removed, the entire surface of the substrate 10 except for the portion where the grooves H and 69 are to be formed is covered with a Ti film. When Ar ion beam etching is performed, grooves 68.
69 is formed. The depth of these grooves 68 and 69 is made deeper than the depth of the optical waveguide 51, etc. (see FIGS. 6 and 7). These full 68. [The mutually facing wall surfaces C and D of i9 become the resonator surfaces.

Furthermore, after this, the Ti film is removed and the voltage application electrode 31 is
~341 Phase adjustment electrodes 61 to 64 and IDT 13 are manufactured by a lift-off method. These electrodes 31-3
Between 4.61 to 64 and the surface of the substrate 10, an S io 2 film having a thickness of 2000 mm is preferably interposed as a buffer layer.

Optical waveguide (eg 51) and groove 68. [i9 constitutes a Fapley-Bello type optical modulator, and as mentioned above, the C and D surfaces of the grooves 68 and 69 are resonator surfaces. A voltage application electrode 31 and a phase adjustment electrode 61 are provided on both sides of the optical waveguide 51, and by applying a voltage to these electrodes, the light propagating between the resonator surfaces C and D is adjusted. The phase changes.

The intensity of light emitted from the optical waveguide 51 changes.

Generally, if the applied voltage is ■ and the electrode spacing is d.

The strength of the electric field generated in the direction across the optical waveguide is given by V/d. If the length of the electrode is , and the direction of the electric field is the Z direction, then in the case of LiNbO3 crystal, the amount of phase change δ of light is given by δ−n·T33·V −J/2 d. When the intensity of the incident light on the optical waveguide is I, and the intensity of the output light is I, the ratio I/I changes periodically with respect to the amount of phase change δ. This change is shown in FIG. In this figure, m is an integer. The above phenomenon applies in the same way to the light that propagates through all the optical waveguides 51 to 54 and is output.

Let's focus on the optical waveguide 51. When a voltage V is applied between the electrodes 31, a phase change appears in the light propagating through the optical waveguide 51, which is given by n.T33.V.8L/2d. Applying an appropriate bias voltage to the phase adjustment electrode 61,
(2) If the phase of the light at =0, that is, the intensity of the emitted light, is taken appropriately, from the optical waveguide 51.

The output light intensity with respect to the applied voltage V as shown in FIG. 9(b) is obtained. FIG. 9(a) shows the amount of phase change of light with respect to applied voltage. The output light of the leading waveguide 51 is converted into an electric signal by a photoelectric conversion element, amplified by an amplifier, and then binarized by discrimination using an appropriate threshold level I by a level discrimination circuit, as shown in FIG. A signal shown in C) is obtained.

The length of the electrodes 32 provided on both sides of the optical waveguide 52 is 4, which is 1/2 of the length of the electrode 31.

The amount of phase change of the light in the leading waveguide 52 is n・γ33・V・4
It becomes L/2 d. Therefore, as shown in FIG. 9(d), the period of the binary signal obtained from the output light of the optical waveguide 52 is twice that of the output light of the optical waveguide 51. In this case as well, of course, an appropriate bias is applied between the one phase adjustment electrodes 62.

Similarly, since the length of the electrodes 33 that sandwich the leading waveguide 53 is 2, and the length of the electrode 34 of the optical waveguide 53 is L,
2 generated from the output light of these optical waveguides 53 and 54
The period of the digitized signal is 2.23 times as shown in FIGS. 9(e) and 9(f').

The following table shows the binary signal (1 or 0) for each region of applied voltage.

(Left below) - 24 Understand that the analog voltage signal applied between one terminal 30 is converted to a gray code digital value as shown in this table, and that this digital value uniquely represents the analog voltage signal. It will be. The error due to quantization becomes the width of each region of the applied voltage.

The light output from the optical waveguides 54 to 51 is deflected by the pulsed SAW generated from the IDTLI, and the light is output from the optical waveguide 4.
It goes without saying that the light is directed from 4a to 41a to 44 to 41, is focused by the Y-shaped leading waveguide 46, 47, and 48, enters the optical fiber 16, and is guided to the photoelectric conversion element as a serial 4-bit signal. do not have.

The 4-bit signal shown in the lower half of Figure 4 and the 4-bit signal shown in the table above
It is slightly different from a bit signal. This is because in the embodiment shown in FIG. 5, phase adjustment electrodes 61 to 64 are provided,
This is because an appropriate voltage is applied to this electrode.

The Fapley-Perot optical modulator has one type of resonant surface other than the one shown in FIG.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a first embodiment of the invention. FIGS. 2 and 3 are graphs showing the relationship between applied voltage and output light intensity. FIG. 4 shows the relationship between the applied voltage and the output light intensity of the four Matsuhatsu Enda type optical waveguides, and the 4-pitch I signal obtained by binarizing the output light intensity. FIG. 5 is a perspective view showing a second embodiment of the invention. Figures 6 and 7 are the VI-VI line in Figure 5 and ■-
■ Each line is an enlarged sectional view. FIG. 8 is a graph showing the characteristics of the output light with respect to the optical phase change of the Fapley-Perot resonator. FIG. 9 is a waveform diagram showing the output signal waveform. 10... Board, 13... IDT. 21-24...Matsuhatsu Enda type optical waveguide. 25-27.46-48...7-shaped optical waveguide. 31-34... Analog voltage application electrodes. 41 to 44. 41a to 44a... Leading wavepath for P/S conversion. 51-54... Optical waveguide, 61-64... Phase adjustment electrode. 6g, fi9... groove, C, D... mirror surface. From l-

Claims (1)

[Claims] A substrate whose optical properties change depending on an applied physical quantity; A branching means for branching light introduced onto the substrate into a plurality of lights of approximately equal intensity; a plurality of modulation elements that each modulate the intensity of the light at different degrees depending on the physical quantity applied; a first optical waveguide section each connected to the output side of the modulation element; a second optical waveguide section, and means for generating a pulsed surface acoustic wave that black-diffracts the light propagating through the first optical waveguide section and guides the diffracted light to the second optical waveguide section; A P/S conversion means formed on a substrate that converts a plurality of output lights into temporally serial optical signals, a means for condensing the P/S converted light, and a means for converting the condensed light to its intensity. A waveguide type optical A/D conversion device comprising: a photoelectric conversion element that converts the output signal into an electric signal representing the signal; and a comparator that discriminates the output signal of the photoelectric conversion element at a required level.