CN109099900B

CN109099900B - Self-reference optical gyroscope resisting noise interference and optical gyroscope denoising method

Info

Publication number: CN109099900B
Application number: CN201811077406.4A
Authority: CN
Inventors: 布兰特·埃弗雷特·李特尔
Original assignee: Qxp Technologies Inc
Current assignee: Qxp Technologies Inc
Priority date: 2018-09-15
Filing date: 2018-09-15
Publication date: 2020-11-03
Anticipated expiration: 2038-09-15
Also published as: CN109099900A

Abstract

The invention relates to an anti-noise interference self-reference optical gyroscope and an optical gyroscope denoising method, and solves the problems that the sensitivity of the conventional gyroscope is influenced by noise, and a denoising device is high in cost and large in size. The optical gyroscope includes a light source, an input coupler, a first Sagnac loop, an output coupler, a demodulator, a second Sagnac loop, and a state splitter; the optical signal sent by the light source comprises a first state optical signal and a second state optical signal, and the first state optical signal and the second state optical signal are received by the demodulator sequentially through the input coupler, the first Sagnac loop, the state wave splitter, the second Sagnac loop and the output coupler; the state wave separator comprises a first port, a second port, a third port and a fourth port; the first state optical signal is transmitted to the third port through the first port and transmitted to the fourth port through the second port; the second state optical signal is transmitted to the fourth port through the first port and transmitted to the third port through the second port.

Description

Self-reference optical gyroscope resisting noise interference and optical gyroscope denoising method

Technical Field

The invention relates to the field of optical sensors, in particular to an anti-noise self-reference optical gyroscope and an optical gyroscope denoising method.

Background

Gyroscopes are used to sense rotational motion, while optical gyroscopes sense rotational motion through the Sagnac effect. The Sagnac effect refers to the phenomenon that two identical optical signals, transmitted in opposite directions, in the same closed loop will experience two different phase or time delays, where the difference in delay is proportional to the effective length of the loop and the angular velocity in the plane of the loop. Sagnac optical gyroscopes are one of the most sensitive types of rotational sensors available.

But the sensitivity of the gyroscope is susceptible to noise, which is a random fluctuation in the light source signal or gyroscope loop, obscuring the signal from the Sagnac effect. Since the signal strength generated by the Sagnac effect is proportional to the rotation rate, the signal strength generated by the rotation speed cannot be detected when the signal strength generated by a minute rotation speed is smaller than the signal strength generated by random noise. Furthermore, in navigational tracking and positioning systems, where position is calculated by integrating the slew rate (and other motion) over a period of time, noise can produce random cumulative errors in position even though the signal strength is much greater than the noise strength.

Therefore, noise reduction is crucial to the gyroscope, and in the conventional method, noise reduction is achieved by selecting a light source and installing the gyroscope in a device that can reduce environmental noise. However, with this approach, the reduction of noise is limited and the better the noise reduction, the more expensive the solution may be and the more bulky the required device.

Disclosure of Invention

The invention aims to solve the problems of poor noise reduction effect, high noise reduction cost and large volume of a required device of the conventional gyroscope, and provides an anti-noise interference self-reference optical gyroscope and an optical gyroscope denoising method.

The technical scheme of the invention is as follows:

an optical gyroscope denoising method comprises the following steps:

1) dividing an optical signal emitted by a light source into a first state optical signal and a second state optical signal;

2) the first state light signal and the second state light signal operate in the same Sagnac loop, the first state light signal output by the Sagnac loop includes a Sagnac effect signal and a noise signal, and the second state light signal includes only the noise signal;

3) subtracting the first state optical signal obtained in the step 2) from the second state optical signal obtained in the step 2) to obtain an optical signal with the Sagnac effect, so as to remove the noise signal.

Meanwhile, the invention also provides an anti-noise interference self-reference optical gyroscope based on the method, which comprises a light source, an input coupler, a first Sagnac loop, an output coupler, a demodulator, a second Sagnac loop and a state wave splitter, wherein the first Sagnac loop and the second Sagnac loop have the same structure; optical signals sent by the light source comprise a first state optical signal and a second state optical signal, and the first state optical signal and the second state optical signal are received by the demodulator sequentially through the input coupler, the first Sagnac loop, the state wave splitter, the second Sagnac loop and the output coupler; the state wave separator comprises an input port and an output port, the input port comprises a first port and a second port, and the output port comprises a third port and a fourth port; the first state optical signal is transmitted to the third port through the first port and transmitted to the fourth port through the second port; the second state optical signal is transmitted to the fourth port through the first port and transmitted to the third port through the second port.

Further, the first state optical signal and the second state optical signal are an optical signal in a first polarization state and an optical signal in a second polarization state, respectively.

Further, a power divider, a polarization converter and a polarization beam combiner are arranged between the light source and the input coupler, one path of optical signal of the power divider is output through the polarization converter, the other path of optical signal is directly output, and the two paths of optical signals are combined into one optical signal by the polarization beam combiner.

Further, the first state optical signal and the second state optical signal are an optical signal of a first wavelength and an optical signal of a second wavelength, respectively.

Further, a modulator is arranged between the light source and the input coupler, and generates optical signals with different wavelengths and the first wavelength and the second wavelength.

Furthermore, a filter is arranged behind the modulator to eliminate other optical signals which are not the optical signal with the first wavelength and the optical signal with the second wavelength.

Further, the input coupler and the output coupler are identical in structure, and the first Sagnac loop is a single loop, a plurality of loops or a resonant loop structure.

Compared with the prior art, the invention has the following technical effects:

the invention discloses an anti-noise interference self-reference optical gyroscope and an optical gyroscope denoising method, which reduce noise in a light source and a gyroscope loop. The invention divides the signal into two different states, and then configures the configuration of the gyroscope loop, so that the two signals can run through the same gyroscope loop along the same path in different configurations, thereby achieving the purpose of removing noise. The output signal from one optical state will include the Sagnac effect and noise, the second output signal from the second optical state will include only noise, and the subtraction of the two signals from the two optical states results in a simple Sagnac effect.

Drawings

FIG. 1 is a schematic diagram of a conventional optical gyroscope system;

FIG. 2 is a schematic diagram of a self-reference gyroscope circuit with a state splitter according to the present invention;

FIG. 3 is a schematic diagram of a state splitter in accordance with the present invention;

FIG. 4 is a schematic diagram of the state 0 signal path direction of the state demultiplexer of the present invention;

FIG. 5 is a schematic diagram of the state 1 signal path direction of the state demultiplexer of the present invention;

FIG. 6 is a schematic diagram of a method for splitting a single wavelength signal into two similar wavelength signals according to the present invention;

FIG. 7 is a schematic diagram of a method of splitting a single polarization state signal into two signals of two orthogonal polarization states according to the present invention;

FIG. 8 is a schematic diagram of the self-referencing gyroscope system of the present invention.

Reference numerals: 11-light source, 12-input coupler, 13-output coupler, 14-Sagnac loop, 15-demodulator; 2-optical source, 3-input coupler, 4-first Sagnac loop, 5-state splitter, 6-second Sagnac loop, 7-output coupler, 8-demodulator; 51-first port, 52-second port, 53-third port, 54-fourth port.

Detailed Description

The invention is described in further detail below with reference to the following figures and specific examples:

the invention discloses a self-reference optical gyroscope which reduces noise in a light source and a gyroscope loop. The present invention achieves this effect by splitting the signal into two different states and then configuring the configuration of the gyroscope loop so that the two signals travel through the same gyroscope loop along the same path in different configurations. The output signal from one optical state will include the Sagnac effect and noise, the second output signal from the second optical state will include only noise, and the subtraction of the two signals from the two optical states results in a simple Sagnac effect. The gyroscope uses the second light state to establish its own reference.

The invention provides a denoising method of an optical gyroscope, which specifically comprises the following steps:

3) and 2) subtracting the obtained first state optical signal and the second state optical signal obtained in the step 2) to obtain an optical signal with the Sagnac effect, so as to remove a noise signal.

Fig. 1 is a schematic diagram showing basic components of a conventional optical gyroscope system. It comprises a light source 11, which light source 11 is divided into two signals S⁺And S^-The two signals are fed into the Sagnac loop through input coupler 12. The two signals propagate in opposite directions around the loop. This loop is an optical rotation sensor, commonly referred to as a Sagnac loop. It may be a single loop, or multiple loops, or a resonant loop configuration. The signal is then coupled out of the loop through an output coupler 13 and sent to a demodulator 15. Demodulator 15 interprets the signal to determine the Sagnac effect and thus the slew rate. In some configurations, the input and output couplers are the same coupler. Noise in the system (source or loop) will also be demodulated and will cause some degree of error in the true rotational Sagnac effect.

The invention provides a denoising method of an optical gyroscope and also provides a self-reference optical gyroscope resisting noise interference. The self-referencing optical gyroscope of the present invention employs a specially configured Sagnac loop. The characteristics of the light source, demodulator and input/output coupler can still be kept consistent with conventional gyroscopes. A schematic diagram of the basic components of the Sagnac loop of a self-referencing optical gyroscope is shown in fig. 2. It comprises a two-part optical loop (Sagnac loop), labelled "part 1" (first Sagnac loop 4) and "part 2" (second Sagnac loop 6), interconnected by a state splitter 5. There are two possible interconnection types of the status splitter 5, which differ according to the status of the optical signal. The state of an optical signal is defined as a particular property of the signal. For example, a state may describe the polarization state of a signal, or a state may describe the wavelength of light of a signal, which are two particularly useful states in optics, but may also fall into other states for a signal.

FIG. 8 is a diagram of a complete self-referencing optical gyroscope system. As in the conventional system of fig. 1, a light source 2 is provided which generates counter-propagating signals. In the present invention, the light source 2 also generates S₀And S₁Two synchronization signals of different states. The signal is injected into the self-reference Sagnac loop (inside the dashed box) through an input coupler 3. An output coupler 7 is provided to extract the signal and send it to a demodulator 8. The input and output couplers may be the same coupler. Demodulator 8 simultaneously resolves the two states of the signal to determine the Sagnac effect and the noise effect, and the resulting output is a pure Sagnac effect with no noise.

As shown in fig. 8, the self-reference optical gyroscope with noise interference resistance provided by the present invention includes a light source 2, an input coupler 3, a first Sagnac loop 4, an output coupler 7, a demodulator 8, a second Sagnac loop 6, and a state splitter 5, where the first Sagnac loop 4 and the second Sagnac loop 6 have the same structure; the optical signal emitted by the optical source 2 includes a first state optical signal and a second state optical signal, and the first state optical signal and the second state optical signal are received by the demodulator 8 through the input coupler 3, the first Sagnac loop 4, the state demultiplexer 5, the second Sagnac loop 6 and the output coupler 7 in sequence.

One key element of the self-reference gyroscope Sagnac is the state splitter 5. As shown in fig. 3, the state splitter 5 has an input port and an output port. The state splitter 5 is bi-directional, which means that the input port and the output port can be interchanged without any change in its response. The state branching filter 5 is used for transmitting the first state optical signal and the second state optical signal through different channels respectively; the state demultiplexer 5 comprises an input port and an output port, wherein the input port comprises a first port 51 and a second port 52, and the output port comprises a third port 53 and a fourth port 54; the first state optical signal is transmitted to the third port 53 through the first port 51 and transmitted to the fourth port 54 through the second port 52; the second status optical signal is transmitted through the first port 51 to the fourth port 54, and through the second port 52 to the third port 53. That is, for an optical signal in a first state (referred to as "state" 0), the first port 51 is connected to the third port 53, and the second port 52 is connected to the fourth port 54; for an optical signal in a second state (referred to as state "1"), the first port 51 is connected to the fourth port 54 and the second port 52 is connected to the third port 53. The routing is performed in dependence on the state of the signal, i.e. the state splitter 5 has a state-dependent interconnection configuration.

The design of a state splitter of the split-wavelength type can be accomplished by photonic device structures known in the art as gratings, MZIs, AWGs, and the like. The design of the state splitter of the polarization splitting type can be implemented by the method of mode coupling or mode evolution well known in the art. Reference may be made to: [1] liu, Liu, et al, "Silicon-on-insulator polarization splitting and deflecting device for polarization splitting" "Optics express 19.13(2011): 12646. 12651. articles such as [2] Chen, Long, Christopher R. Doerr, and Young-Kai Chen.

Fig. 4 and 5 show the paths traveled in the Sagnac loop by two different states of an optical signal in accordance with the present invention. As shown in FIG. 4, the signal is in the state "0", and the reverse transmission signal and the clockwise transmission signal are respectively S₀ ⁺And S₀ ^-And (4) showing. The subscript "0" indicates the state "0", and the superscript "+" or "-" indicates the direction of propagation of the particular signal, the state splitter 5 being in the state "0" in response to the state of the signal. In the Sagnac loop plane, each signal S₀ ⁺And S₀ ^-All traveling continuously in the same direction. For example, in the first Sagnac loop, signal S₀ ⁺Proceeding in the counterclockwise direction. Also, in the second Sagnac loop, signal S₀ ⁺Also in a counter clockwise direction. The additive effect of Sagnac is the sum of the Sagnac effects of the first and second Sagnac loops, so in this case the signal propagation directions are similar and the two are additive.

As shown in fig. 5The signal is in state "1" and the counter-propagating signal adopts S₁ ⁺And S₁ ^-And (4) showing. The subscript "1" indicates the state "1", and the superscripts "+" and "-" indicate the direction of the signal. The state splitter 5 in fig. 5 is in state "1" in response to the state of the signal. For these signals in state 1, the signal travels in one direction in the first Sagnac loop and in the opposite direction in the second Sagnac loop. For example, in the first Sagnac loop, signal S₁ ⁺Travelling in a counter-clockwise direction, while in the second Sagnac loop, the signal S₁ ⁺Travel in a clockwise direction. The total effect of Sagnac is the sum of the Sagnac effects of the first and second Sagnac loops, so in this case the signal propagation directions are reversed and the two are subtracted.

Considering that the first Sagnac loop and the second Sagnac loop have the same geometry, signal S in state "0" in fig. 4₀ ⁺And S₀ ^-The net Sagnac effect experienced is twice that of either part, signal S in state "1" in fig. 5₁ ⁺And S₁ ^-The net Sagnac effect experienced is the difference between the first and second Sagnac loop effects, which is zero at this time. The ambient noise contribution of the light source or Sagnac loop is independent of the path direction and affects both signal states almost equally. The signals of state 0 and state 1 are independently demodulated in the demodulation section of the gyroscope system. The demodulated output response of state 0 is the Sagnac effect plus the noise effect. The demodulated output response of state 1 is only a noise effect because the first and second Sagnac loops cancel the Sagnac effect, and the pure Sagnac effect can be extracted from the noise by subtracting the response of state 0 from state 1.

In the self-reference optical gyroscope Sagnac loop, signals of two states propagate simultaneously. The states are labeled "0" and "1" and the corresponding signals are labeled S₀And S₁. The two state types may be states with different wavelengths and states with different polarization directions, and other types of states may be used. The two states may come from two different light sources. However, in order to obtain maximum yield and noise immunity performance in a self-referencing gyroscope, particularly with respect to source noise, the two states should be from the same signal source. Fig. 6 and 7 show how these states can be derived for two different wavelengths and two different polarization directions, respectively.

Fig. 6 illustrates how two different wavelength states are obtained from a single wavelength light source. A signal S of wavelength lambda is input to a high-speed sinusoidal amplitude modulation modulator with a modulation depth of 100%. The modulator will generate two new signals at the two wavelengths of the new λ - Δ λ and λ + Δ λ, thereby generating two signal states S₀And S₁. Since most modulators are not perfectly sinusoidal, a filter should be placed after the modulator to eliminate all signals not of these two wavelengths, whose wavelength separation 2 Δ λ is determined by the modulation frequency.

Fig. 7 depicts how two different orthogonal polarization states can be obtained from a single polarized light source. The signal strength is A, the signal S with the polarization state S is input into a power divider, and the power divider generates two paths of output signals, wherein the power of the two paths of output signals is half of the input power. One output signal is input to a polarization converter which converts the s-polarization state to the orthogonal p-polarization state, and the other output signal is output directly, and the two signals are then combined into one beam in a polarization beam combiner. One polarization state is labeled as the "0" state and the other as the "1" state.

Claims

1. Self-referencing optical gyroscope resistant to noise disturbances, comprising a light source (2), an input coupler (3), a first Sagnac loop (4), an output coupler (7) and a demodulator (8), characterized in that: the device also comprises a second Sagnac loop (6) and a state wave splitter (5), wherein the first Sagnac loop (4) and the second Sagnac loop (6) have the same structure;

optical signals sent by the light source (2) comprise a first state optical signal and a second state optical signal, and the first state optical signal and the second state optical signal are received by the demodulator (8) sequentially through the input coupler (3), the first Sagnac loop (4), the state wave splitter (5), the second Sagnac loop (6) and the output coupler (7);

the state wave separator (5) comprises an input port and an output port, wherein the input port comprises a first port (51) and a second port (52), and the output port comprises a third port (53) and a fourth port (54); the first state optical signal is transmitted to a third port (53) through a first port (51) and transmitted to a fourth port (54) through a second port (52) respectively; the second state optical signal is transmitted to the fourth port (54) through the first port (51) and transmitted to the third port (53) through the second port (52), respectively.

2. The self-referencing optical gyroscope resistant to noise interference according to claim 1, characterized by: the first state optical signal and the second state optical signal sent by the light source (2) are respectively an optical signal in a first polarization state and an optical signal in a second polarization state.

3. The self-referencing optical gyroscope resistant to noise interference according to claim 2, wherein: a power divider, a polarization converter and a polarization beam combiner are arranged between the light source (2) and the input coupler (3), one path of optical signal of the power divider is output through the polarization converter, the other path of optical signal is directly output, and the two paths of optical signals are combined into one optical signal by the polarization beam combiner.

4. The self-referencing optical gyroscope resistant to noise interference according to claim 1, characterized by: the first state optical signal and the second state optical signal sent by the light source (2) are respectively an optical signal with a first wavelength and an optical signal with a second wavelength.

5. The self-referencing optical gyroscope resistant to noise interference according to claim 4, wherein: a modulator is arranged between the light source (2) and the input coupler (3) and generates optical signals with different wavelengths and first wavelengths and second wavelengths.

6. The self-referencing optical gyroscope resistant to noise interference according to claim 5, wherein: and a filter is arranged behind the modulator to eliminate optical signals with the first wavelength and optical signals with other wavelengths except the optical signals with the second wavelength.

7. Self-reference optical gyroscope resistant to noise interference according to any one of claims 1 to 6, characterized in that: the input coupler (3) and the output coupler (7) are identical in structure, and the first Sagnac loop (4) is a single loop, a plurality of loops or a resonant loop structure.

8. An optical gyroscope denoising method is characterized by comprising the following steps:

in the step 2), the Sagnac loop comprises a first Sagnac loop, a state wave splitter and a second Sagnac loop which are sequentially arranged; the state wave separator comprises an input port and an output port, the input port comprises a first port and a second port, and the output port comprises a third port and a fourth port; the first state optical signal is transmitted to the third port through the first port and transmitted to the fourth port through the second port; the second state optical signals are transmitted to the fourth port through the first port and transmitted to the third port through the second port respectively;

9. The optical gyroscope denoising method of claim 8, wherein: in step 1), the first state optical signal and the second state optical signal are an optical signal in a first polarization state and an optical signal in a second polarization state, respectively, or an optical signal in a first wavelength and an optical signal in a second wavelength, respectively.