RU2105990C1 - Fiber-optical device determining azimuthal direction to hydroacoustic beacon - Google Patents

Abstract

FIELD: underwater acoustics, navigation of undersurface and surface fleets. SUBSTANCE: turns of fibrous coils in interferometer are wound in agreement with sinusoidal law with period Λ. Turns of one coil are displaced by half-period relative to turns of another coil. Hydroacoustic beacon sends acoustic waves omnidirectionally with period Λ. Fibrous interferometer receives these waves turning fibrous coils in direction of arrival of waves with the aid of rotary system. Sought-for azimuth angle is read simultaneously. EFFECT: enhanced functional reliability of fiber-optical device. 2 cl, 3 dwg

Description

 The invention relates to the field of hydroacoustics and can be used for navigation of surface and underwater fleets.

 A device of the same purpose is known, containing several spatially separated hydrophones with known directivity characteristics and an information processing system with a recorder [1] that allows you to determine the azimuthal direction to the sonar beacon operating in a mode known to the operator.

 The disadvantage of this device is the lack of an optical signal at its output, which in the near future will be the main source of information in many branches of science and technology.

 Known sonar antenna, made on fiber-optic elements, which can be considered as a device for a similar purpose [2] since using the antenna in the receiving mode, it is possible to determine the azimuthal direction to the sonar beacon.

 This device is taken as a prototype.

 The prototype contains a subject fiber coil, made with the possibility of contacting the working medium, and a reference fiber coil, optically matched with a coherent light source and a photodetector to an interferometer, an information processing unit including an amplifier connected to the output of the photodetector, and also a rotary system with an azimuthal registration unit angle of rotation.

 A rotary system that allows you to change the direction of the directivity of the antenna is made in the form of known electronic means.

 The disadvantage of the prototype is the complexity of the hydroacoustic antenna associated with many fiber-optic hydrophones and an electronic system for generating directivity characteristics.

 The technical effect obtained from the implementation of the invention is to simplify the known device by eliminating many fiber-optic hydrophones from its composition. This allows us to reduce the useful volume and weight of the device, which in turn presents the possibility of replacing the electronic rotary system of the device with a simpler, for example mechanical.

 This technical effect is achieved due to the fact that in the known fiber-optic device for determining the azimuthal direction to the hydroacoustic beacon containing an object fiber coil made with the possibility of contacting with the working medium, and a reference fiber coil, optically matched with a coherent light source and a photodetector in interferometer, information processing unit, including an amplifier connected to the output of the photodetector, as well as a rotary system with an azimuthal registration unit angle of rotation, the support and the subject fiber coils are aligned and made with a winding density of the coils obeying the sinusoidal law, while the coils of the subject and support coils are spatially shifted relative to each other by half the winding period in the direction of the axis of the coils.

 The device may further comprise a series-connected bandpass filter, an extremator and a feedback unit, while the input of the bandpass filter is connected to the output of the amplifier, and the output of the feedback unit to the control input of the rotary system.

 In FIG. 1 shows a schematic optical-electronic circuit of the device, in FIG. 2 the spatial arrangement of the turns in the reference and subject fiber coils, in FIG. 3 diagram explaining the operation of the device.

 The device contains (Fig. 1) the subject and reference fiber coils 1, 2 optically matched with a coherent light source 3 and a photodetector 4 into an interferometer (in this case, Zehnder-Mach). The division of fiber coils 1, 2 into object and support is purely conditional. In fact, their functions are equivalent. There are also series-connected amplifier 5, a band-pass filter 6, an extremator 7 and a feedback unit 8. The input of the amplifier 5 is connected to the output of the photodetector 4.

 The device includes a rotary system 9, made, for example, in the form of a mechanical drive, the control input of which is connected to the output of the feedback unit 8, and the actuator is connected to the object and support coils (the last connection is not shown in the drawing).

 The output of the rotary system is connected to the block 10 registration of the azimuthal angle of rotation.

 A distinctive feature of the device is that the reference and subject fiber coils are aligned and made with a winding density of the coils obeying a sinusoidal law, while the turns of the subject and reference coils are spatially offset relative to each other by half the winding period in the direction of the axis of the coils.

 In FIG. 2 at the top are the sinusoidal laws of spatial winding of the coils of the subject and support coils. And below are the coils themselves, the density of the windings of which meets these laws. For clarity, FIG. 2 turns of one coil (solid lines) are shifted in the vertical direction relative to the turns of another coil (dashed lines). In fact, according to the claims, the turns of the support and object coils follow each other. The winding period in FIG. 2 marked Λ The axis of the coils coincides with the x axis.

 The device operates as follows.

 The hydroacoustic beacon (not shown) emits acoustic waves with a spatial period L (at a frequency of 1500 Hz, the period L 1 m) with an isotropic emitter. Sound waves 11 (Fig. 1) are received by a fiber optic device. Since the winding density of the turns of the subject and reference fiber coils 1, 2 obeys a sinusoidal law with a period L and the coils are spatially shifted half the period in the direction of wave propagation, the maximum output signal of the photodetector 4 will be observed at the moment of coincidence of the axis of the coils and the direction of arrival of the sound wave 11.

In FIG. 3 shows the output curve 12 of the interferometer, the initial phase difference of which by known means is set to point A equal to p / 2
The sinusoidal input signal 13 causes the appearance of the photodetector 4 signal 14 of the photocurrent, which is amplified by the amplifier 5, is filtered by a band-pass filter 6 and passes through the extremator 7. The latter in the case of a subsequent increase in the output signal 14 passes it to the feedback unit 8, which in turn gives to the control input of the rotary device 9, a mismatch signal with a given polarity to bring it into action.

 This process proceeds to the complete coincidence of the direction of the axis of the fiber coils with the direction of arrival of the acoustic wave 11.

 In this case, the rotation angle of the fiber coils 1, 2 is continuously monitored by the azimuthal rotation angle registration unit 10.

A change in the average speed of sound along the route of acoustic waves of a sonar beacon to a fiber-optic device will practically not affect the results of determining the azimuth angle. Even a temperature period of 25 ^o C causes a change in the speed of sound [3] not more than a tenth of a percent (less than the instrumental error of the device).

 Thus, the proposed device is actually using one fiber interferometer allows you to obtain a technical effect to reduce the effective length of the outer part to one meter (in the prototype tens of meters), as well as more than an order to reduce the useful weight of the equipment.

Sources of information
1. Japanese application N 48 7469, cl. 107 D21 (G 01 S 3/80), 1973.

 2. US patent N 4115753, CL. 340 6R (G 01 S 3/30), 1978 prototype.

 3. M. Greenspan, C.E. Tschieqo. Table of the Speed of sound in water. J. Acoust. Soc. Amer. 1959, 31, N 1, pp. 75 76.

Claims (2)

 1. Fiber-optic device for determining the azimuthal direction to the sonar beacon, containing a fiber interferometer made in the form of a coherent light source, object and reference fiber coils and a photodetector, as well as an information processing unit including an amplifier connected to the output of the photodetector of the interferometer, and a rotary a system with a unit for recording an azimuthal angle of rotation, characterized in that the support and subject fiber coils are aligned and made with a winding pitch in it, obeying a sinusoidal law, while the turns of the subject and support coils are spatially shifted relative to each other by half the winding pitch in the direction of the axis of the coils.  2. The device according to claim 1, characterized in that it further comprises a series-connected bandpass filter, an extremator and a feedback unit, while the input of the bandpass filter is connected to the output of the amplifier, and the output of the feedback unit to the control input of the rotary system.

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