RU276U1 - Light guide speed sensor - Google Patents

Abstract

A fiber-optic speed sensor consisting of optical and electronic units, the optical unit being made up of a low-coherent emitter, a first coupler depolarizer, a polarizer and a second coupler depolarizer, the outputs of which are interconnected via a serial optical fiber of the sensing element and a phase modulator, and a photodetector, input which is connected to the second input of the first splitter, and the electronic unit is made of a sinusoidal generator and the circuit processing tats of measurements, characterized in that the electronic unit additionally includes regulators of the amplitude of the photo signal, the phase modulation depth and the optimal frequency of the phase modulation, and a control signal circuit, and the circuit of the processing of measurement results additionally includes series-connected first key, analog-to-digital converter, register the shift, the subtraction scheme, the second key, the battery and the shaper of the code package, while the control inputs of the regulators of the amplitude of the photo signal, the depth of the phase mode The parameters, the optimal phase modulation frequency, and the processing circuit of the measurement results are connected to the output of the photodetector, the output of the amplitude regulator of the photo signal is connected to the current input of a low coherent emitter, the output of the depth modulator of the phase modulation is connected to the control input of the phase modulator, and the signal input of this regulator is connected to the first output of the sinusoidal generator , the second output and the control input of which are connected respectively to the control input and the output of the optimal frequency controller f

Description

ROTATION SPEED SENSOR

The utility model relates to the field of measurement technology and can be used in the development of light guide speed sensors of rotation and navigation systems based on them.

Closest to the proposed utility model is a device according to European patent A2 0160.450 MKI 20IC I9 / 64 with a priority of 04.25.84, which consists of optical and electronic units. The optical unit is made according to the so-called minimal structure and consists of a low-coherent radiation source, the output of which through a series-connected depolarizer, the first splitter and polarizer is connected to the input of the second splitter, the outputs of which are interconnected through a series-connected optical fiber of the sensing element and a phase modulator, the input of the photodetector is connected to the second input of the first splitter. The electronic unit is made of a sinusoidal generator and a circuit for processing measurement results, consisting of a two-channel switch, the input of which is connected to the output of the photodetector, two narrow-band filters connected to the outputs of the switch, and a phase detector, the inputs of which are connected to the outputs of the filters. In this case, the first output of the sinusoidal generator is connected to the control input of the phase modulator, and its second output via the delay line, or phase shifter, is connected to the control input of the switch.

The performance of this sensor is very low. Since this circuit does not have mechanisms for automatically adjusting the parameters of the electronic circuit depending on the specific characteristics of the optical circuit, and the sensor is operable only with strict phasing of the control signal of the switch and with strictly set values of the effective depth of the phase yOIC 19/64

Because of the frequency of phase modulation, then in a wide temperature range it cannot be used: zero drift already in laboratory conditions exceeds hundreds of degrees per hour. The scale factor is fundamentally non-linear and strongly depends on variations in the characteristics of the optical and electronic units.

The objective of this utility model is to create a light guide rotational speed sensor with high performance.

The technical result that can be obtained by implementing the inventive model is to ensure the stability and linearity of the scale factor and zero drift close to the limits determined by the quality of the optical unit.

The problem is solved in such a way that the electronic unit additionally includes controllers for the amplitude of the photo signal, the phase modulation depth and the optimal frequency of the phase modulation, and a control signal circuit, and the first key, an analog-to-digital converter, and the register are additionally included in the processing circuit of the measurement results shift, deduction scheme, second key, battery and shaper of the code package. In this case, the control inputs of the controllers for the amplitude of the photo signal, the depth of the phase modulation and the frequency of the phase modulation, and the circuit for processing the measurement results are connected to the output of the photodetector, the output of the controller for the amplitude of the photo signal is connected to the current input of a low coherent emitter, the output of the depth modulator for phase modulation is connected to the control input of the phase modulator, and the signal the input of this controller is connected to the first output of the syth generator (the second output and the control input of which are connected, respectively Actually, with the control input and the output of the controller of the optimal phase modulation frequency, the third output of the sine wave generator is connected to the input of the control signal circuit, the output of which is connected in parallel to the control inputs of the first key and shift register, the fourth output of the sine wave generator is sub-connected to the control input of the second key, and the second analog output a digital converter is connected to the second input of the subtraction circuit,

The proposed technical solution is illustrated by the drawings: on fvg.1 presents a diagram of a fiber-optic speed sensor in accordance with the formula of the utility model; figure 2 presents a timing diagram of the sensor of figure 1.

The operation of the light guide rotational speed sensor (figure 1) is as follows. The radiation of a low coherent light source I (mainly a superluminescent semiconductor diode) of arbitrary elliptical polarization is transmitted to depolarizer 2 (made, for example, by welding two birefringent optical fibers with their mutual angular shift of the polarization axes at an angle of 45 ° (which carries out circular polarization of radiation through the first splitter 3, the radiation enters the polarizer 4, which suppresses one of the orthogonal components, and then, passing through the second splitter An amplifier 5, transmitting the polarization state of the radiation, is supplied in equal proportions to its two outputs, circling the optical fiber of the sensing element 6 (Sagnac interferometer) in two opposite directions.On one of the outputs of the second splitter 5, a phase modulator 7 is installed, to the control input of which a sinusoidal signal from sine & dlnoy generator 8:

Uy () - Ј # (2)

where is the depth of phase modulation.

For the electric field, E, optical radiation at the output of the polarizer 4, you can write the expression:

E &) && p {j & Y + U + (3)

Ј2 ewjj & Ј + & «- where Ет« is the amplitude of the electric field of the beam circling the fiber

of a sensitive element clockwise or counterclockwise, respectively, O is the circular frequency of optical radiation, the travel time of the radiation along the fiber of the sensitive element, 0 is the Sagnac phase shift due to the rotation of the sensitive element.

Assuming EjsErjwE and taking into account that photodetector 9 is a quantum device, we can write the expression for the photodiode current:

e. (4)

In the future, we will be interested only in the heterodyne term:

LsJettfapbrt- 1 + & -A (fe $ m to + e) t

hLvk-2 Ґ - Pr Ј jr (6)

 and, i.e., maximum efficiency is achieved

phase modulation, therefore in the future the value of g will

be called the optimal circular frequency of the phase modulation, and the value of Cho is the effective depth of the phase modulation.

The fulfillment of condition (6) is also desirable from the point of view of minimizing the noise of the optical circuit.

negative feedback covering the photodetector 9 and the optical element circuit.

The phase modulation depth adjusters II to the optimum phase modulation frequency 12 are intended to automatically maintain condition (6).

The amplitude-stabilized photo signal from the output of the photodetector 9 is fed to the input of the first key 13, which performs the gating of the signal at the maximum points of the function), corresponding to the values of jr. Gating times determine ML

with the control signal circuit 14. From the output of the key 13, the samples of the function% are input to the input of the analog-to-digital converter 15, which converts the sample amplitude to a digital stream, which simultaneously arrives at the inputs of the shift register 16, also controlled by the control signal circuit 14, and the subtraction circuit 17. Due to the delay of the digital stream in the shift register 16 by one clock cycle, a fixed time delay is equal to the half-period of the phase modulation signal. As a result, at the output of the subtraction scheme 17, a sample of the function is formed:

q fa) {b & 3, ()

which for small 9 can be approximated as

q fa) J & (bk in) (8)

Function (8) has extrema at

Al (K + fa) jr (9)

Јk + l

, X- / C-TJ j-

 r-j

Щ (Yu)

Expression (10) corresponds to the maximum of function (8) (see FIG. 2B), or to the zeros of function (5) at (solid line of FIG. 26). When zeros, functions (5) are shifted (dashed line in Fig. 26) and ampZM + f

Since function (5) is even, then, as can be seen from Fig. 26 (dashed line), the shift of its zeros has the opposite sign in the first and second wave periods relative to the phase-modulating signal (Fig. Ze). As can be seen from figv the sign of the difference of the samples - digital streams coming directly from the output of the AED 15 and from the output of the shift register 16, will vary depending on the half-period, therefore, to preserve the sign of the measured value, 0, it is necessary to use only one of the half-periods, for example, the first, which is done with the help of the second key 18 (§§ 2d, f). Using the battery 19 is the accumulation and averaging of measurement results; the shaper code SENDING 20 according to the instructions of the consumer of information transmits averaging data in accordance with a given information exchange protocol.

Claims (1)

A fiber-optic speed sensor consisting of optical and electronic units, the optical unit being made up of a low-coherent emitter, a first coupler depolarizer, a polarizer and a second coupler depolarizer, the outputs of which are interconnected via a serial optical fiber of the sensing element and a phase modulator, and a photodetector, input which is connected to the second input of the first splitter, and the electronic unit is made of a sinusoidal generator and the circuit processing tats of measurements, characterized in that the electronic unit additionally includes regulators of the amplitude of the photo signal, the phase modulation depth and the optimal frequency of the phase modulation, and a control signal circuit, and the circuit of the processing of measurement results additionally includes series-connected first key, analog-to-digital converter, register the shift, the subtraction scheme, the second key, the battery and the shaper of the code package, while the control inputs of the regulators of the amplitude of the photo signal, the depth of the phase mode The parameters, the optimal phase modulation frequency, and the processing circuit of the measurement results are connected to the output of the photodetector, the output of the amplitude regulator of the photo signal is connected to the current input of a low coherent emitter, the output of the depth modulator of the phase modulation is connected to the control input of the phase modulator, and the signal input of this regulator is connected to the first output of the sinusoidal generator , the second output and the control input of which are connected respectively to the control input and the output of the optimal frequency controller f basic modulation, the third output of the sinusoidal generator is connected to the input of the control signal circuit, the output of which is connected in parallel to the inputs of the control, the first key and the shift register, the fourth output of the sinusoidal generator is connected to the control input of the second key, the second output of the analog-to-digital converter is connected to the second input of the circuit subtractions.