SU1503038A1 - Optronic a-d converter - Google Patents

Abstract

The invention relates to optoelectronics and can be used to convert analog signals to digital binary code. The aim of the invention is to improve the circuit properties, simplify the topology, improve the manufacturability of the device. To accomplish the goal, the Fabry-Perot resonator in the form of a strip waveguide on a substrate made of electro-optical material with reflective elements in the form of planar interdigital electrode structures was used in the analog-digital converter. 3 il.

Description

An image of the United States of America (: to the optoelectronics and can be used for conversion) and the signal converter

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with computer systems and system-digital signal processing.

The aim of the invention is to improve the circuit properties, simplify the topology, the desallation of the technology and the KMHOCTH manufactured -) - 1 device.

Fig. 1 shows a schematic diagram of a converter; FIG. 2 is a diagram of the Fabri-1ero waveguide resonator; n f. ig, 3 wiring diagrams of converter operation

For definiteness, consider. three-bit analog-to-digital converter (ADC), The device is completed on an electro-optical substrate 1,

which is formed on the left side of the waveguide laser. 3. A photodetector 4, an amplifier 5 and a comparator 6 are docked on the right side. Reflecting elements 7-10 are located across the surface of the substrate across the waveguide control electrodes 11–13 are located.

To understand the operation of the device as a whole, it is necessary to consider the operation of a separate Fabry-Perot waveguide resonator (VRFP).

Figure 2 shows the substrate 1, a single-mode waveguide 2, metal electrodes 11 arranged along the waveguide and a reflective element 7.

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about

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When the electrical voltage Vj is turned on, the counter-pin electrodes, of which the reflective elements 7 consist, form, due to the electro-optical effect, a phase grating in the dielectric. When fulfilling the conditions

2A

w m -,

where A is the period of location of the electrodes 1 1;

m 1,2,3 ... is the order of the Bragg diffraction;

 DD is the wavelength of the light emission in vacuum;

n.j is the effective refractive index of the wave mode, this phase grating acts as a reflecting surface with some coefficient of reflection of light on intensity R and coefficient of transmittance of light on intensity T, Thus, the reflective elements will form a Fabry-Perot diffuser in the substrate, Excluding losses.

Since the waveguide is formed in an electro-optical material, the voltage V applied to the electrodes 11 introduces into the light mode propagating through the waveguide the phase shift

) oi.vi,

where oi, is the coefficient of proportionality, depending on the properties of the substrate material, size and relative position in: 1 wire and electrodes; 1 - the length of the electrodes.

The total phase shift in a single pass of the light mode along the resonator is

 (V) iL + ucfjCv),

where ft is the distribution constant

this fashion;

L is the length of the resonator, i.e. distance between reflective elements.

The dependence of the skipping coefficient t of the Fabry-Perot resonator (in the absence of losses) on R is given by

T2

  1 T + ARsin fAi CV)

where Ij, is the intensity of the light introduced into the resonator;

0

0

,

50

five

Q

five

I is the intensity of light transmitted through the resonator.

Note that this is a periodic function of V, and the form of this function depends on the coefficients T and R. Thus, on the VRFP, it is possible to realize the ADC bit. The operation of the device is explained by time diagrams (Fig. 3), where V (t) is an analog input signal; b, f. , j transmittance coefficients of FGFD, formed by respectively reflecting 1 elements 7 and 8, 7 and 9, 7 and 10; Y; - control pulses applied to the reflecting elements i + 7, (, 2); I is the output digital signal; r is the decimal representation of the binary number generated at the output of I.

The Converter operates as follows.

The three-digit binary number corresponding to the input analog signal V (t) is generated in three cycles (Fig. 3, V, V, V). In the first cycle the voltage is applied to the reflective elements 7 and 8, which form a VRFP of length 1, which leads to the formation of the output of the comparator 6 high binary bit. In the second cycle, reflective elements 7 and 9 are included, which form a VRFP of length 1, which leads to the formation of a second discharge, since the total length of electrodes 11 and 12 is twice the length of electrodes 11. In the third cycle, reflective elements 7 and 10 are included, The VFPP is long, and the least significant bit appears at the output of the ADC. Thus, a three-bit binary number is formed at the output in a sequential code. I

The proposed converter by. Compared to the known one, it has a simpler topology and is more technological in manufacturing, since, unlike the well-known one having one waveguide per k, each discharge, the proposed converter has only one waveguide. In addition, the end mirrors that make up Fabry-Perot resonators in a known transducer require precision fabrication methods, because dielectric waveguides are almost always on the surface of the substrate and their depth usually does not exceed 1-2 µm. Photolithographic method of deposition on the surface

The substrates of the counter-pin electrode structures that form the Fabry-Perot resonators in the described device are much simpler. The converter also has significant circuitry advantages. In the prototype, the number of output elements (photodetectors, comparators, amplifiers) is equal to the output number, In the described device, only one photodetector, one comparator, one amplifier are needed, In addition, the proposed converter in contrast from the known generates a number in a binary code, expanded in time, and therefore its output can be directly connected to the input of a fiber optic communication line without using delay lines ki or multiplexing schemes,

Claims (1)

Invention Formula An optoelectronic analog-to-digital converter containing a single-mode single-wavelength waveguide mounted on a substrate made of electro-optical material, with a system of control electrodes, the output of which is connected in series with a photodetector, amplifier, and comparator, which, in order to improve circuit properties , simplify the topology, improve the manufacturability of manufacturing, it additionally introduces controllable reflective elements located on the substrate surface along waveguide between the control electrodes, made in the form of counter-pin structures with a period L determined from the condition 2A. "- b-, where m 1,2,3 ... is the order of the Bragg diffraction; Ld is the wavelength of the light emission in vacuum; n is the effective refractive index of the waveguide mode, and the distances between the reflective elements are equal L, (C) L E fi where i 1,2 ..,; | 3 - constant distribution waveguide mode; n is the order number of the gap between the corresponding reflective elements. and the lengths of the control electrodes are 1 "equal In 1,2 pt 0 five where 1 is the length of the shortest control electrode; p 2,3,4, ..- the order of the legs of the remaining electrodes, the number of electrode pairs being equal to the number of double digits of the formed number, and the number of reflective elements exceeding the number of digits of the formed number by one. 0 ft) b Ultrasound 456 Sh 1st year f uB.2