JPH0772522A - Optical ad converter and optical da converter - Google Patents

Abstract

PURPOSE:To provide the optical AD converter of simple constitution which can operate at an extremely high speed. CONSTITUTION:A frequency modulator 9 modulates the frequency of a local oscillator 11 with an input electric signal generated by an input electric signal source 10 and outputs a modulated wave including amplitude information on the input electric signal as frequency information. Then a spatial optical phase modulator 3 excites an ultrasonic wave in a medium having acoustooptic effect with the modulated wave. Then the medium varies in refractive index through optoelastic effect to impose phase modulation on a passing light beam. When the phase-modulated light beam is processed by Fourier transformation through an optical lens 5, the spectrum distribution of the modulated wave is generated and displacement of the light beam corresponding to the amplitude of the input electric signal is obtained. A photodiode arranged on the projection surface of the optical lens 5 receives the spectrum distribution of the modulated wave and outputs of respective elements of the photodiode array 6 are passed through a comparator 7 having a proper threshold value and are converted into a digital signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical AD converter for converting an analog signal into a digital signal by using light, and an optical DA converter for performing DA conversion in the reverse process of the optical AD converter. is there.

[0002]

2. Description of the Related Art Conventionally, as an optical AD converter for modulating light with an analog signal and converting the modulated light into a digital signal, one using light intensity modulation by an electro-optical effect or a magneto-optical effect is known. There is. Figure 2 shows Li Nb O ₃
2 shows a conventional optical AD converter using the branch interfering optical intensity modulators 21 to 24. In FIG. 2, the optical intensity of the light output from the branch interfering optical intensity modulators 21 to 24 is the applied voltage. periodically changes in correspondence with, the half-wave voltage V _[pi respective control electrodes of the interferometric type optical intensity modulator 21 to 24 25-2
It is inversely proportional to the electrode length L of 8. When the electric signal V is simultaneously applied to the respective control electrodes 25 to 28 of the branching interference type optical intensity modulators 21 to 24, the phase shift amount Δφ _n becomes the electrode of the control electrode of the nth branching interference type optical intensity modulator. If the length L _n is L _n = 2 ⁿ · L ₁ , Δφ _n = 2 ⁿ⁻¹ · π · V / V _π1 . Here, n = 1, 2, ..., N, N is the number of branch interference type optical intensity modulators. The light intensity of the light output from the branch interference type light intensity modulator is I _n = I _n0 · COS ² (Δφ _n + φ _n ). Here, I _n0 is the modulation amplitude, and φ _n is the steady phase shift amount due to the DC bias current. The output light of the branch interference type light intensity modulators 21 to 24 becomes an electric signal in the photodetector 29 and is amplified in the amplifier 30.

[0003]

However, the above-mentioned conventional optical AD converter has a problem that the structure is complicated and it is difficult to manufacture, and the element length must be increased in order to improve the resolution. However, there is a problem that the response speed is reduced because it must be done. Furthermore, DA in the reverse process
Difficult to convert.

The present invention has been made in view of the above, and takes advantage of the inherent parallel property of light,
Optical AD converter and optical D that can operate at a very high speed with a simple configuration
It is intended to provide an A converter.

[0005]

In order to achieve the above-mentioned object, the solution means specifically taken by the invention of claim 1 is a light A
An optical deflector for a D converter, which deflects light so as to have a deflection angle corresponding to the amplitude of an analog electric signal, and a plurality of optical deflectors arranged in the deflection direction of the light and receiving the light deflected by the optical deflector. And a plurality of comparators provided corresponding to the plurality of light receivers and converting output signals from the corresponding light receivers into binary signals by a predetermined threshold. To do.

The invention of claim 2 is specifically, claim 1.
In addition to the configuration of the invention of claim 1, the optical deflector adds a configuration for deflecting light by an acousto-optic effect.

The invention of claim 3 is, specifically, claim 1
In addition to the configuration of the invention described above, the optical deflector adds a configuration for deflecting light by an electro-optical effect.

The invention of claim 4 is, specifically, claim 1
In addition to the configuration of the invention described above, the optical deflector adds a configuration for deflecting light by a magneto-optical effect.

The invention of claim 5 is, specifically, claim 1
In addition to the configuration of the invention of 1, the optical deflector has a configuration including a spatial light phase modulator and an optical lens.

Further, in order to achieve the above-mentioned object, a solution means specifically taken by the invention of claim 6 is an optical DA converter, which is arranged in a predetermined direction, and outputs an optical signal according to the value of a binary signal. And a light receiver for converting the light emitted from the plurality of light emitters into an analog electric signal having an amplitude according to the incident angle of the light. .

[0011]

According to the present invention, the optical deflector spatially deflects the light according to the amplitude information of the analog electric signal, and a plurality of light receivers arranged in the direction of deflection of the light, for example, a photo detector. By receiving the light deflected by the diode array, the amplitude of the analog electrical signal can be read discretely. As a result, it is possible to perform the comparator operation at an extremely high speed with an extremely simple configuration.

According to the structure of the sixth aspect of the invention, a plurality of light emitters arranged in a predetermined direction emit light in accordance with the value of the binary signal, and the light receiver receives the light and makes the light incident angle thereof. It is converted into an analog electric signal with an amplitude according to. Thus, with a simple configuration, a digital signal can be converted into an analog electric signal at an extremely high speed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an optical AD converter according to an embodiment of the present invention using a spatial light phase modulator 3 based on the acousto-optic effect. In FIG. 1, the frequency modulator 9 is an input electric signal source 10. The local oscillator 1 is generated by the input electric signal generated by
By frequency-modulating the frequency of 1, the amplitude information of the input electric signal is replaced with the frequency information. Here, the frequency modulator 9 may be a wide band VCO. next,
In the spatial light phase modulator 3, the modulated wave containing the amplitude information of the input electric signal as the frequency information causes Pb Mo O
An ultrasonic wave is excited in a medium having an acousto-optic effect such as ₄ . Then, the refractive index of the medium changes due to the photoelastic effect, and the light beam passing through the medium undergoes phase modulation. The optical phase modulation caused in the cross section of the light beam occurs in proportion to the modulated wave applied to the transducer 4,
When the phase-modulated light beam is Fourier-transformed by the action of the optical lens 5, the spectrum of the modulated wave containing the amplitude information of the input electric signal as frequency information can be decomposed. In short, the displacement of the light beam according to the amplitude of the input electric signal can be obtained by replacing the amplitude information of the input electric signal with the frequency information and performing optical spectrum analysis. A photodiode array 6 is arranged on the projection surface of the optical lens 5. The light distribution projected on the photodiode array 6 is a spectral distribution of the modulated wave applied to the transducer 4, and the peak point of the distribution is displaced by the voltage of the original input electric signal. In this way, the voltage of the input electric signal is projected onto the photodiode array 6 as an analog displacement of the light beam. Originally, since the respective elements of the photodiode array 6 are spatially and discretely arranged,
The output of each element of the photodiode array 6 is converted into a digital signal by passing through a comparator 7 having an appropriate threshold value. In FIG. 1, 1 is a light source, 2 is an optical lens, and 8 is an encoding circuit.

The principle of optical spectrum analysis will be described below. If the input analog electric signal is v (t) and the modulated wave frequency-modulated by the input analog electric signal v (t) is f (t), then f (t) = Re [Aexp (jθ (t)) ] Becomes However, the instantaneous angular frequency is defined as follows.

Ω _i = dθ / dt = ω _c + k _f · v (t) When the phase velocity of the ultrasonic wave in the crystal is v _p , the change in the refractive index at the coordinate x is g (x−v _p · t). Occurs in proportion to. The light is changed by this spatially distributed refractive index change,
It undergoes phase modulation spatially. The spatially phase-modulated light is represented as follows.

[0017]

[Equation 1] Here, α is a constant. The image to be produced at infinity by this light can be projected close by the action of the optical lens. The projected light distribution is a Fourier-exchanged version of g (x), and the frequency spectrum distribution of g (x) is obtained as follows.

H (k _x ) = δ (k _x ) + jα · G
_{(K x) exp (-jk x} · v p · t) This is the principle of the optical spectrum analyzer. On the other hand, since each frequency component of g (t) is proportional to the input analog electric signal v (t), the spectral distribution of g (t) should be the intensity distribution of v (t). is there. Therefore, a deflection of the light beam proportional to the input analog electrical signal v (t) is obtained.

As described above, the voltage can be exchanged for the spatial displacement of the light beam, and each output of the photodiode array placed on the projection surface of the optical lens is converted into a binary signal by an appropriate threshold value. The analog signal is converted into a digital signal.

The optical AD converter of the present invention is not limited to the above-described embodiment, but in this embodiment,
Although the optical deflector is composed of the spatial light phase modulator based on the acoustooptic effect, the spatial light phase modulator is not limited to the spatial light phase modulator based on the acoustooptic effect. Further, the optical deflector is not limited to the one configured by the spatial light phase modulator. Various changes can be made without departing from the spirit of the invention. For example, the spatial light phase modulator is not limited to the bulk type and may be a waveguide type. Further, the spatial light phase modulator is not limited to one based on the acousto-optic effect, but may be based on the electro-optic effect or the magneto-optic effect. In short, it suffices that the voltage change of the electric signal can be converted into the spatial displacement of the light beam. Therefore, the wavelength of the light may be changed by the electric signal and the optical spectrum decomposition may be performed by the prism or the diffraction grating. Further, as in the present embodiment, the diffraction angle of the light beam may be changed corresponding to the electric signal by changing the grating interval of the diffraction grating by the electric signal while keeping the wavelength of the light constant. Further, the spatial light phase modulator is not limited to one-dimensional type, but may be a two-dimensional type depending on the traveling direction of ultrasonic waves.

Further, the present embodiment can be applied to an optical DA converter, and a plurality of light emitters arranged in a predetermined direction and emitting light according to the value of a binary signal, and a plurality of light emitters emitting light. A digital signal can be converted into an analog electric signal at an extremely high speed by a light receiver which converts the received light into an analog electric signal having an amplitude corresponding to the incident angle of the light.

[0022]

As described above, according to the optical AD converters according to the inventions of claims 1 to 5, the light beam is spatially deflected by the amplitude information of the analog electric signal, and the deflected light beam is, for example, a photodiode. By receiving in the array,
The amplitude of the electric signal can be read discretely. As a result, it becomes possible to convert an analog electric signal that changes at an extremely high speed into a digital signal in real time with a simple configuration.

According to the optical DA converter according to the invention of claim 6 applied to DA conversion, a plurality of light emitters arranged in a predetermined direction emit light according to the value of the binary signal, and the light receiver. Can receive the light and convert the light into an analog electric signal having an amplitude corresponding to the incident angle, so that the digital signal can be converted into the analog electric signal at an extremely high speed with a simple configuration.

As described above, according to the present invention, it is possible to provide an optical AD converter and an optical DA converter that can operate at a very high speed with a simple structure. The optical AD converter of the present invention is an optoelectronic integrated circuit. Suitable for AD converter or comparator.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an optical AD converter according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a conventional optical AD converter.

[Explanation of symbols]

 1 Light source 2, 5 Optical lens 3 Spatial light phase modulator by acousto-optic effect 4 Transducer 6 Photodiode array 7 Comparator 8 Encoding circuit 9 Frequency modulator 10 Input electric signal source 11 Local oscillator

Claims (6)

[Claims] 1. An optical deflector for deflecting light so as to have a deflection angle according to the amplitude of an analog electric signal, and a plurality of optical deflectors arranged in the deflection direction of the light for receiving the light deflected by the optical deflector. And a plurality of comparators provided respectively corresponding to the plurality of light receivers and converting output signals from the corresponding light receivers into binary signals according to a predetermined threshold value. Optical AD converter that does. 2. The optical AD converter according to claim 1, wherein the optical deflector deflects light by an acousto-optic effect. 3. The optical AD converter according to claim 1, wherein the optical deflector deflects light by an electro-optical effect. 4. The optical AD converter according to claim 1, wherein the optical deflector deflects light by a magneto-optical effect. 5. The optical AD converter according to claim 1, wherein the optical deflector has a spatial light phase modulator and an optical lens. 6. A plurality of light emitters arranged in a predetermined direction and emitting light according to the value of a binary signal, and light emitted from the plurality of light emitters having an amplitude corresponding to an incident angle of light. An optical DA converter comprising: a light receiver for converting into an analog electric signal.