RU203287U1 - Optical scheme of FOG for noise reduction of the radiation source - Google Patents

Abstract

The utility model relates to the field of optical interferometric measuring technology and concerns the optical circuit of a fiber-optic gyroscope. The optical scheme contains a source of optical radiation, an optical polarizer, two optical splitters, preserving polarization, and an optical circulator, preserving polarization. The first optical splitter provides separation into compensation and measurement optical paths. The compensation path is directed through the polarization converter and, then, to the second optical splitter connecting these paths. The measuring path is directed through the optical circulator into the multifunctional integrated-optical circuit and, then, into the fiber spool, and the output signal from the multifunctional integrated-optical circuit through the optical circulator is directed to the splitter connecting the paths, which directs the optical signals of both paths to the photodetector. The technical result consists in reducing the noise component of the fiber-optic gyroscope at a frequency equal to the natural frequency of the fiber gyroscope circuit. 1 wp f-ly, 1 dwg.

Description

Technical field to which the utility model belongs

The utility model relates to optical interferometric measuring equipment, in particular, to the field of measuring equipment that makes it possible to reduce the excess noise of an optical radiation source used in an angular velocity sensor (fiber-optic gyroscope).

State of the art

Known fiber-optic interferometric measuring sensor (US 20160363446 A1, 2016), in which the reduction of excess noise of the optical radiation source is implemented using the separation of the signals of the optical radiation source into two signals of orthogonal polarizations. One signal is fed to the measuring Sagnac interferometer, while the second is sent in the opposite direction to the photodetector of the sensor using optical dividers. The advantage is a high degree of consistency of the optical path lengths of the two signals. The disadvantages are the complexity of the optical circuit, due to the increase in the number of different optical components, as well as high losses in signal power, since optical signals experience excessive losses due to the need to pass through the same optical components repeatedly.

The problem to be solved by the technical solution is to create a sensitive element of a fiber-optic interferometric sensor with a simple design and providing a high dynamic range.

The essence of the utility model

This problem is achieved due to the fact that the radiation of a broadband source of optical radiation (for example, a spontaneous emission amplifier), polarized along one plane of polarization in an optical fiber, is divided into two signals, a measurement signal and a compensation signal. The measuring signal, passing through the optical path, enters directly into the circuit of the fiber-optic gyroscope, where the measuring signal, splitting into two beams going towards each other, and experiencing a phase shift as a result of the rotation of the gyroscope together with the object, interfere with each other. The interference signal is then returned through the optical path to the photodetector for processing and calculating the angular velocity of the gyroscope. The compensation signal, after separation from the measuring signal, is fed directly to the photodetector, while the polarization plane of the compensation signal is rotated relative to the measuring signal by 90 ° to eliminate possible interference effects on the photodetector. When it hits the photodetector, the measuring signal is delayed for a time t, corresponding to the length of the optical circuit of the fiber-optic gyroscope. Both signals, measurement and compensation, contain the same excess noise inherent in a broadband radiation source. When it hits the photodetector, the excess noise of the compensation signal is optically added to the excess noise of the measuring signal. Since the demodulation of the gyroscope signal is performed at the natural frequency of the fiber circuit, and the signal delay time is equal to half the demodulation period, then during optical addition of signals, the excess noise of the optical radiation source is actually subtracted from the gyroscope signal.

The technical result is to reduce the noise component of the fiber-optic gyroscope at a frequency equal to the natural frequency of the fiber gyroscope circuit. In this case, there is no significant loss of power of the useful signal.

The optical noise reduction circuit of a fiber gyroscope is designed and operates as follows. Optical radiation, leaving the broadband radiation source 110 (Fig. 1), passes through the fiber linear polarizer 111 (Fig. 1), acquiring the corresponding state of polarization. Linearly polarized light S _{1, ||} then enters through the optical path 12 into the fiber splitter 121 (Fig. 1), the division ratio of which can be predominantly in the range of 0.95 / 0.05 ~ 0.90 / 0.10, depending on the losses introduced by the sensitive element of the FOG. Optical signal S _{1, ||} is divided according to the division factor into signals S _{2, ||} and S _{3, ||} ... Signal S _{1, ||} passing through the optical path 231 through the optical circulator 131 (Fig. 1) is directed to the FOG sensor 140 (Fig. 1). Optical signal S _{2, ||} , having passed through the multifunctional integrated-optical circuit (SIOM) 141 (Fig. 1) and the fiber-optic circuit 142 (Fig. 1), and interfering, is converted into an optical signal S ₂ ' _{, ||} ... Optical signal S ₂ ' _{, ||} after passing through the sensitive element FOG 140 (Fig. 1) is directed through the optical circulator 131 along the optical path 312 into the optical splitter 132 with a division ratio of 50/50 (with an error of ± 5%) and then goes to the photodetector 150.

Optical signal S _{3, ||} is directed through the optical path 232. Passing through the optical path 232, the optical signal S _{3, ||} undergoes a rotation of the plane of polarization by passing through an optical welded joint 130, the polarization retention axes of which are connected at an angle of 90 ° ± 1 °. The optical signal S _{3, ﬩} after the rotation of the plane of polarization is directed through the optical splitter 132 to the photodetector 150. Further, the sum of the signals S ₂ ' _{, ||} and S _{3, ﬩ is} fed through the matching stages on the operational amplifiers to the analog-to-digital converter 160 and is then demodulated at the natural frequency of the loop, i.e. the values of the signal of odd clock cycles are subtracted from the even clock cycles, while the noise of the source is subtracted from the signal from the sensitive element of the FOG.

Claims (2)

1. The optical scheme of a fiber-optic gyroscope, containing an optical radiation source, an optical polarizer, two optical splitters, preserving polarization and an optical circulator, preserving polarization, characterized in that the first optical splitter, preserving the polarization of light and providing separation into two optical paths, one of which, "compensation", is directed through the polarization converter and, further, to the second optical splitter connecting these paths, which preserves polarization, and the second optical path - "measuring", is directed through the optical circulator, which preserves polarization, into a multifunctional integrated optical circuit and, then, into the fiber coil, and the output signal from the integrated optical multifunctional circuit through the specified optical circulator is directed to the splitter connecting the paths, which directs the optical signals of both paths to the photodetector. 2. The optical scheme of the FOG according to claim 1, characterized in that an optical adjustable attenuator, manually or automatically controlled, is built into the optical path of the compensation signal.

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