Fiber optic receiver gradient of the sound pressure

 

(57) Abstract:

The invention relates to the field of hydro-acoustics and can be used in laboratory and field conditions to measure sound waves in the liquid. The essence of the invention lies in the fact that single-beam fiber Zehnder interferometer is a Mach, having as two sensor fiber coil located at a certain distance from each other, complemented by a multibeam dvuhgolosiem the interferometer having three associated optical fiber coil. With two coils of both interferometers are common. Junction interferometers is carried out through the use of different wavelengths generated by two lasers. Single-beam interferometer has a harmonic output curve and multibeam - acute fringes output curve. This allows for homodyne conversion to use multibeam interferometer for receiving weak acoustic signals, and one for receiving stronger acoustic signals. The receiver has an electronic circuit to automatically select the operation mode depending on the level of the acoustic signal. 1 C.p. f-crystals, 3 ill.

The invention from the parameters of the sound waves in the liquid.

Known fiber-optic receivers (GPS) gradient of the sound pressure [1, 2] used both in laboratory and in situ conditions. Any of known UXO may be adopted for the prototype.

Known UXO, for example, [2] contains the laser and the photodetector, optically coordinated through two fiber coils located at a certain distance from each other, in one-Zehnder interferometer is a Mach, and a high-pass filter, amplifier and multichannel recorder, and the output of the photodetector through the filter high-frequency connected to the input of an amplifier output connected to a multi-channel recorder.

A disadvantage of the known devices [1 and 2] is not sufficiently high sensitivity GPS mode homodyne conversion, limited by the limiting slope of the sine wave, which changes the output curve is known gradient receiver [2]

The technical result obtained by the invention is to increase the sensitivity of fiber-optic interferometric receiver gradient of the sound pressure by increasing the slope of the output curve of the interferometer mode homodyne conversion.

Dunn is the laser and the photodetector, optical coordinated through two fiber coils located at a certain distance from each other, in one-Zehnder interferometer is a Mach, and a high-pass filter, amplifier and multichannel recorder, and the output of the photodetector through a high pass filter connected to the input of an amplifier output connected to a multi-channel logger further comprises a third fiber coil, protected from sound pressure, a second laser, the second photodetector, the second high pass filter and a second amplifier when the lasers are made at different wavelengths, fibers of the first and second coils are made of material transparent to both the wavelength of the laser, and the third fiber coil of material transparent to the wavelength of the second laser, but not permeable to the wavelength of the first laser, the second laser and a second photodetector optically aligned with the first, second, and third fiber coils in the multibeam dvukhkontsevoi interferometer, while before the first photodetector has an interference filter at the wavelength of the first laser and the second photodetector has an interference filter at the wavelength of the second laser, and the output whoredom to multi-channel logger.

The first and second fiber coil is made of quartz glass fibers, and a third of the polymeric fiber, the first laser is performed on a wavelength A, and the second wavelength A.

The GP may further comprise two integrator, two Comparators, two blocks of reference voltages and two electronic key, the first integrator is connected by its input to the output of the first amplifier, and the output to the first input of the first comparator, a second input connected to the first block of the reference voltage, and the output from the controlled input of the first electronic switch, a second integrator connected by its input to the output of the second amplifier, and the output to the first input of the second comparator, a second input connected with the second block of the reference voltage, and the output from the controlled input of the second electronic key, moreover, the outputs of the first and second amplifiers connected to the multichannel inputs of the Registrar respectively through the first and second electronic switches.

The TPO further comprises a scaling device installed at the outlet of the first or second electronic keys.

The GP may further comprise two phase-shifting device, one of which ustanavlivaetsya drawings.

In Fig. 1 shows the optical scheme of the GP; Fig. 2 electronic circuit GP; Fig. 3 chart explaining the operation of the GPS.

Fiber optic receiver gradient of the sound pressure (Fig. 1) includes a laser 1 operating at a wavelength of1laser 2 operating at a wavelength of2and three fiber reels 3, 4 and 5 (coil 5 is conventionally shown in the form of one turn of the spiral). There are also two of the photodetector 6 and 7, before whom there is interference filters 8 and 9, one 8 length2and the other 9 on the length of the1.

The laser 1 and the photodetector 7 is optically aligned with the fiber coils 3 and 4 in single-beam Zehnder interferometer is a Mach. Coordination occurs with the introduction of the optical device 10, the fiber couplers 11, 12 and output optical device 13.

Laser 2 and the photodetector 6 is optically aligned in the multibeam dvukhkontsevoi the interferometer through the fiber coil 3, 4, 5.

Coordination occurs through the introduction of optical device 14, the fiber couplers 11, 12 and the optical output device 15.

Ways to coordinate the optical elements in a single beam in the multi-beam fiber interferometers presents the different coils 3 and 4 are made of material, transmissive length1and2waves of both lasers 1 and 2, and the fiber coil 5 is made of a material transparent to the wavelength of the2laser 2, but not permeable to the wavelength of the laser 1. In addition, before the photodetector 7 install the interference filter 9 per wavelength1and before photodetector 6 - filter 8 per wavelength2.

In the particular case of fiber coils 3 and 4 are made of quartz glass fibers and the fiber coil 5 of the polymeric fiber, the laser 2 use the ruby laser with a wavelength of A, and as the laser 1 helium-neon laser with a wavelength of A. Optical loss quartz radiation at first and second wavelengths respectively (5) 6 and 10 dB/km, and polymer fibers 60 and 7 dB/km i.e quartz fiber transmits selected wavelengths is almost the same, and polymer - skips only one wavelength.

The optical scheme of the TPO also includes two phase-shifting devices 16 and 17. The phase-shifting unit 16 is installed in the fiber coil 4, and the phase-shifting device 17 in the fiber coil 5.

The sensitive element of the GP are fiber coils 3 and 4, located on rasoun outside of the study area and to be made in the form of resveratol fiber length (i.e., straight cut fibers).

An electronic circuit GP (Fig. 2) includes a filter 18 and 19 high frequency amplifiers 20 and 21, the integrators 22 and 23, the Comparators 24 and 25, the Comparators 26 and 27, the electronic switches 28 and 29, the scaling unit 30 and multichannel recorder 31.

Connection diagram shown in the drawing.

Fiber optic receiver gradient of the sound pressure is as follows.

Install the sensing element of the TPO in the test environment so that the fiber coil 3 and 4 were located one behind the other with respect to the sound wave 32 (Fig. 1).

Suppose that the input signal GP has the appearance shown in Fig. 3, under item 33 (here under the positions 34 and 35 presents the output curves, respectively, single-beam and multibeam interferometers).

If the pre-use phase-shifting devices 16 and 17, the initial phase difference set in the point a (the point of greatest curvature and linearity of the output curves 34 and 35), the receiver can be considered ready for use.

Assume that you start working less sensitive single-beam interferometer.

Sound wave 32 (Fig. 1) causes the appearance on pricescope signal amplitude. The interference filter 9 passes useful optical signal on the photodetector 7, the output of which is allocated signal 36 (Fig. 3). The variable component proportional to the gradient of the sound pressure of an acoustic wave 32 (Fig. 1), is amplified by the amplifier 30 and is recorded on a multichannel recorder 31 (Fig. 2).

At the same Registrar you can register and the output signal is more sensitive multibeam interferometer. And subsequent analysis allows you to choose one or the other of the recorded output signals, depending on the magnitude of the input signal.

The selection of the mode of EO can be done automatically.

For this purpose, the integrator 22 directs the integrated output signal to a comparator 24 for comparing the output signal level with a reference voltage unit 26 reference voltages characterizing the limiting sensitivity of the single-beam interferometer and the maximum linear range of the multibeam interferometer. If the output signal of the single-beam interferometer more support, then the output signal is passed electronic key 28 on a multichannel recorder 31, if less, the signal is delayed and informaregulations interferometer with the photodetector 7 through the filter 19 to the high frequency and the amplifier 20 is fed to the integrator 22, after which, in the comparator 25 compares the value of the other reference voltage (block 27 reference voltages). The value of the second reference voltage is selected as the linearity of the plot output curve 35 multibeam interferometer for a given signal level. If the integrated value of the output signal of the multibeam interferometer does not exceed the reference, the signal passes through an electronic key 29 on a multichannel recorder 31. If exceeded, the signal is delayed electronic key 25 and begins to work one-beam interferometer.

The scaling unit 30 allows you to record the output signals of the various interferometers in the same scale.

Thus, the GP can increase the sensitivity of the device without reducing its operating range.

Sources of information:

1. G. B. Mills, S. L. Garrett, E. F. Carome. Fiber optic gradient Hydrophone "Proc. Soc. Photo-Opt. Instrum. Eng.", 1984, Fiber Opt. and Laser Sinsors II, Proc. Conf. Arlengton, Va, Tay 1-2, 1984, 98-103. (R. D. MIT, 1985, N 10.32.420).

2. U.S. patent N 4799752, CL 350-9615 (C 02 B 6/26), 1989.

1. Fiber optic receiver gradient of the sound pressure, containing a laser and a photodetector, optically coordinated through two fiber coils, RAS well as a high-pass filter, the amplifier and multichannel recorder, and the output of the photodetector through a high pass filter connected to the input of the amplifier, is connected by the output to multi-channel recorder, characterized in that it further contains a third fiber coil, protected from sound pressure, a second laser, the second photodetector, the second high pass filter and a second amplifier, and two phase-shifting device, one of which is installed in the first or second fiber coils, and the other in the third fiber coil, while the lasers are made at different wavelengths, fibers of the first and second coils are made of material transparent to the radiation of both lasers, and the third fiber coil of material transparent to radiation of the second laser, the second laser and a second photodetector optically aligned with the first, second, and third fiber coils with the formation of multibeam controllable two-annular interferometer, while before the first photodetector has an interference filter at the wavelength of the first laser and the second photodetector has an interference filter at the wavelength of the second laser, and the output of the second photodetector through the second filter high cha is 2. The receiver under item 1, characterized in that the first and second fiber coil is made of quartz glass fibers, and a third of the polymeric fiber, the first laser is performed on a wavelength and the second wavelength N

 

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