WO2024024032A1 - Fiber optic gyroscope light source device - Google Patents

Abstract

Provided is a fiber optic gyroscope light source device that allows for a reduction in relative intensity noise in a fiber optic gyroscope even if a broadband light source containing relative intensity noise is used therein.　This fiber optic gyroscope light source device is intended for driving an interferometric fiber optic gyroscope 1 including an optical fiber coil, and comprises a broadband light source 10 and a noise reduction unit 20. The broadband light source 10 emits light containing relative intensity noise. With respect to relative intensity noise of the light emitted from the broadband light source 10, the noise reduction unit 20 reduces relative intensity noise at frequencies that are odd multiples of nth-order harmonics (n = 1, 2, 3...) of the natural frequency of the optical fiber coil.

Description

Light source device for optical fiber gyroscope

The present invention relates to a light source device for an optical fiber gyroscope, and particularly to a light source device for an optical fiber gyroscope for driving an interference type optical fiber gyroscope using an optical fiber coil.

With the rapid development of automatic control and autonomous navigation in recent years, the demand for improving the accuracy of the current location of moving objects is increasing year by year. As autonomous navigation technologies, GNSS (Global Navigation Satellite System) and INS (Inertial Navigation System) are known.

Here, a fiber optic gyroscope (FOG) is known as a sensor used in the INS (for example, Patent Document 1). FOG is a rotational angular velocity sensor that utilizes the Sagnac effect of light. Optical fiber gyroscopes use an optical fiber coil, have no moving parts, are smaller than conventional mechanical gyroscopes, and have the advantage of being maintenance-free, and are attracting attention.

但し、Ｒは光ファイバコイルの半径、Ｎは光ファイバコイルの巻き数、λは波長、ｃは光速である。 The phase difference ΔΦ generated according to the rotational angular velocity of the optical fiber gyroscope is obtained by multiplying the angular velocity Ω by a scale factor (SF) as a coefficient. That is, the coefficient of the angular velocity Ω on the right side of the formula for the phase difference ΔΦ expressed below is called a scale factor.

However, R is the radius of the optical fiber coil, N is the number of turns of the optical fiber coil, λ is the wavelength, and c is the speed of light.

The scale factor corresponds to the ratio of the angular velocity to the output signal, and as can be seen from Equation 1, it is subject to fluctuations in the wavelength λ. If the scale factor is not stable over time, the phase difference will fluctuate even under a constant angular velocity, and the sensor output will also fluctuate. As a result, no matter how high the sensitivity (output signal) is, the Allan deviation, which is an indicator of gyroscope accuracy, gets worse over time. Therefore, it is necessary to increase the stability of the scale factor in order to improve the Allan deviation.

Patent Document 1 is known as a method for increasing the stability of such a scale factor. Patent Document 1 relates to a symmetric wavelength multiplexer, and is a stabilized light source that reduces scale factor errors by reducing spectral asymmetry between orthogonal wavelength axes. However, although the stabilized light source disclosed in Patent Document 1 has a good scale factor, when used as a light source for an optical fiber gyroscope, the band of laser light is narrow, and light backscattering and polarization within the optical fiber coil occur. Performance deterioration due to wave coupling, etc. was unavoidable.

In order to avoid such light backscattering and polarization coupling within the optical fiber coil, a broadband laser beam may be used. Patent Document 2 by the same applicant as the applicant of the present application is known as a light source device for an optical fiber gyroscope that has a wide band while increasing the stability of the scale factor of the laser beam.

Here, when the laser light from the light source device for an optical fiber gyroscope is made to have a wide band, light of different frequencies interfere with each other, causing temporal fluctuations in intensity. This intensity fluctuation is called intensity noise, and the intensity noise per unit frequency divided by the average optical power is called relative intensity noise (RIN). In Patent Document 2, a multifunctional integrated optical circuit used not in a light source device for an optical fiber gyroscope but in an interferometric optical fiber gyroscope is phase-modulated at an odd multiple of the natural frequency of an optical fiber coil. , reducing RIN.

Japanese Patent Application Publication No. 2019-184599 International Publication No. 2021/124790

As mentioned above, in Patent Document 2, a light source device for an optical fiber gyroscope is made to have a wider band by increasing the stability of the scale factor, and also to provide light for a multifunctional integrated optical circuit used in an interferometric fiber optic gyroscope. RIN was reduced by performing phase modulation at an odd multiple of the fiber coil's natural frequency. On the other hand, random fluctuations between frequency components within a wide spectrum due to broadband light source devices cause very strong RIN in optical fiber gyroscopes. However, the noise that causes RIN in an optical fiber gyroscope has not been suppressed in advance on the optical fiber gyroscope light source device side. Therefore, it has been desired to develop a technique for suppressing the RIN of an optical fiber gyroscope by suppressing the RIN on the light source device side for the optical fiber gyroscope.

In view of these circumstances, the present invention seeks to provide a light source device for an optical fiber gyroscope that can suppress the relative intensity noise of the optical fiber gyroscope even when using a broadband light source that includes relative intensity noise.

In order to achieve the above-mentioned object of the present invention, the light source device for an optical fiber gyroscope according to the present invention includes a broadband light source that emits light that includes relative intensity noise, and a light source that emits light that includes relative intensity noise. , a noise suppression unit that suppresses relative intensity noise of frequencies that are odd multiples of the n-th harmonic (n=1, 2, 3, . . . ) of the natural frequency of the optical fiber coil.

Here, the noise suppression unit uses a beam splitter that splits light emitted from a broadband light source, a photodetector that converts the light split by the beam splitter into an electrical signal, and an electrical signal converted by the photodetector. Any device may be used as long as it includes a feedback control section that performs feedback control of the broadband light source.

The noise suppression unit further includes a filter circuit that extracts an electrical signal corresponding to an odd multiple of the n-th harmonic of the natural frequency of the optical fiber coil from the electrical signal converted by the photodetector. The feedback control section may be any device that performs feedback control of the broadband light source using the electrical signal extracted by the filter circuit.

The noise suppression section further includes a signal splitter that splits the electrical signal converted by the photodetector into a plurality of electrical signals, and the filter circuit splits the electrical signal converted by the signal splitter into a plurality of electrical signals. The feedback control section includes a plurality of bandpass filters that extract a plurality of electrical signals each having a frequency that is a different odd multiple of the n-th harmonic of the natural frequency of the optical fiber coil, and the feedback control section extracts a plurality of electrical signals that are extracted by the plurality of bandpass filters. The broadband light source may be feedback-controlled using a plurality of electrical signals.

Further, the noise suppressing section may suppress relative intensity noise at a frequency at least one time and three times the n-th harmonic of the natural frequency of the optical fiber coil.

Further, the light source device for an optical fiber gyroscope of the present invention is an interference type light source using an optical fiber coil having a low natural frequency such that the frequency of an odd multiple of the n-th harmonic is lower than the cutoff frequency of the feedback control section. It may also be something that drives a fiber gyroscope.

Further, the feedback control section may be any type as long as it controls the drive current of the broadband light source.

Furthermore, the noise suppression section may be composed of an intensity modulator that suppresses frequencies that are odd multiples of the n-th harmonic of the natural frequency of the optical fiber coil.

Furthermore, the noise suppression section may be composed of a semiconductor optical amplifier that suppresses frequencies that are odd multiples of the n-th harmonic of the natural frequency of the optical fiber coil.

The light source device for an optical fiber gyroscope of the present invention has the advantage that relative intensity noise of an optical fiber gyroscope can be suppressed even if a broadband light source that includes relative intensity noise is used.

FIG. 1 is a schematic block diagram for explaining a light source device for an optical fiber gyroscope according to the present invention. FIG. 2 is a schematic block diagram for explaining an example of the configuration of a general interference type optical fiber gyroscope driven using the optical fiber gyroscope light source device of the present invention. FIG. 3 is a schematic block diagram for explaining a specific example of the noise suppression section of the optical fiber gyroscope light source device of the present invention. FIG. 4 is a conceptual graph for explaining how the RIN of the modulation/demodulation frequency of light emitted from a broadband light source is suppressed by the filter circuit of the noise suppression section of the optical fiber gyroscope light source device of the present invention. FIG. 5 is a schematic block diagram for explaining another specific example of the noise suppression section of the light source device for an optical fiber gyroscope according to the present invention. FIG. 6 is a diagram for explaining how RIN of a plurality of odd multiple frequencies of light emitted from a broadband light source is suppressed by a plurality of bandpass filters of a noise suppression section of a light source device for an optical fiber gyroscope according to the present invention. This is an actual measurement graph. FIG. 7 is a sensitivity graph for explaining the suppression effect of RIN on the output of an optical fiber gyroscope by the optical fiber gyroscope light source device of the present invention. FIG. 8 is a schematic block diagram for explaining still another specific example of the noise suppression section of the optical fiber gyroscope light source device of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to illustrated examples. The light source device for an optical fiber gyroscope of the present invention can be used to drive an interference type optical fiber gyroscope using an optical fiber coil. The interference type optical fiber gyroscope is not particularly limited to a specific one, and any existing or future developed gyroscope can be applied. FIG. 1 is a schematic block diagram for explaining a light source device for an optical fiber gyroscope according to the present invention. As shown in the figure, the optical fiber gyroscope light source device of the present invention includes a broadband light source 10 and a noise suppressor 20. The light whose relative intensity noise has been suppressed by the noise suppressor 20 may be input to the interference type optical fiber gyroscope 1.

The broadband light source 10 emits light that includes relative intensity noise (RIN). In the case of a light source that does not include relative intensity noise, there is no need to suppress the relative intensity noise. Therefore, in the light source device for an optical fiber gyroscope of the present invention, if a broadband light source 10 that emits light that includes RIN is used, good. Further, the light emitted by the broadband light source 10 may be a laser beam. Specifically, as the broadband light source 10, for example, an SLD (Super Luminescent Diode) light source can be used. The SLD light source is a broadband light source that has the characteristics of a light emitting diode and a semiconductor laser, and has a wide spectrum like a light emitting diode, but emits high output light like a semiconductor laser. Since SLD light sources have excellent coupling with optical fibers, they are also commonly used as light sources for optical fiber gyroscopes.

The noise suppressor 20 suppresses the RIN of light emitted from the broadband light source 10. More specifically, the noise suppression unit 20 suppresses the RIN of the light emitted from the broadband light source 10 by suppressing an odd number of n-th harmonics (n=1, 2, 3...) of the natural frequency of the optical fiber coil. It is sufficient to suppress RIN of twice the frequency. In the interference type optical fiber gyroscope 1, the frequency ν of the n-th harmonic of the natural frequency of the optical fiber coil is determined for the counterclockwise light and clockwise light that have passed through the optical fiber coil, and the interference light that is recombined. By performing modulation and demodulation with _m , it is possible to extract the angular velocity signal. Therefore, if the noise suppressor 20 basically suppresses the RIN of the frequency ν _m used in this modulation/demodulation, it should be possible to suppress the RIN in the interferometric optical fiber gyroscope 1 as well. A more specific configuration of the noise suppressor 20 will be described later.

The light with the RIN of frequency ν _m suppressed in this manner is input to the interference type optical fiber gyroscope 1. Here, the general configuration of the interference type optical fiber gyroscope 1 will be explained. FIG. 2 is a schematic block diagram for explaining an example of the configuration of a general interference type optical fiber gyroscope driven using the optical fiber gyroscope light source device of the present invention. The interference type optical fiber gyroscope 1 mainly includes an optical circulator 2, a multifunctional integrated optical circuit 3, a phase modulation signal generator 4, a photodetector 5, and a synchronous detector 6. An optical fiber coil 7 is connected to the multifunctional integrated optical circuit 3.

The optical circulator 2 separates the light from the optical fiber gyroscope light source device of the present invention and interference light obtained by recombining the left-handed light and right-handed light that passed through the optical fiber coil 7. That is, the optical circulator 2 outputs the light from the optical fiber gyroscope light source device of the present invention to the multifunctional integrated optical circuit 3 side, and when the interference light returns to the optical circulator 2, it is output to the photodetector 5. It is output to the side. In the drawing, light from the light source device for an optical fiber gyroscope of the present invention enters from the left side of the optical circulator 2, and this light is output from the right side of the optical circulator 2. When the interference light, which is the recombination of the counterclockwise light and the clockwise light that passed through the optical fiber coil 7, returns, it enters the right side of the optical circulator 2 and is output to the photodetector 5 below, which will be described later. Ru.

The multifunctional integrated optical circuit 3 includes a polarizer 3a, a Y branch/recombiner 3b, a first phase modulator 3c, and a second phase modulator 3d. The light from the optical fiber gyroscope light source device of the present invention is incident on the polarizer 3a via the optical circulator 2. The polarizer 3a allows only a single polarized light to pass through. The Y branch/recombiner 3b branches the incident light from the polarizer 3a, that is, a single polarized light, and makes the split light incident on both ends of the optical fiber coil 7, respectively. The light incident on both ends of the optical fiber coil 7 becomes counterclockwise light and clockwise light, respectively. Then, the Y branch/recombiner 3b recombines the left-handed light and the right-handed light that have passed through the optical fiber coil 7, and outputs this as interference light to the optical circulator 2. The first phase modulator 3c modulates one of the incident lights incident on one end of the optical fiber coil 7. For example, it is sufficient to modulate the incident light that becomes clockwise light. Further, the second phase modulator 3d modulates the other incident light that is incident on the other end of the optical fiber coil 7. For example, it is sufficient to modulate the incident light that becomes counterclockwise light.

The phase modulation signal generator 4 generates a phase modulation signal. The phase modulation signal generator 4 outputs a phase modulation signal to the first phase modulator 3c and the second phase modulator 3d of the multifunctional integrated optical circuit 3. The phase modulation signal generator 4 multiplies a phase modulation signal so as to modulate the counterclockwise light and clockwise light that have passed through the optical fiber coil at a frequency ν _m of the n-th harmonic of the natural frequency of the optical fiber coil. It is generated for the functional integrated optical circuit 3.

The photodetector 5 receives the interference light of the counterclockwise light and the clockwise light that have passed through the optical fiber coil 7 from the optical circulator 2, and detects the light intensity signal of this interference light.

The synchronous detector 6 demodulates the phase modulated signal from the phase modulated signal generator 4 as a reference signal, and synchronously detects the optical intensity signal detected by the photodetector 5, thereby providing input to the optical fiber coil 7. It outputs an angular velocity detection signal.

The RIN of the optical fiber gyroscope is suppressed by driving such an interference type optical fiber gyroscope 1 using light with a frequency ν _m in which RIN is suppressed by the light source device for an optical fiber gyroscope of the present invention. .

Next, a specific example of the noise suppression unit 20 will be described. FIG. 3 is a schematic block diagram for explaining a specific example of the noise suppression section of the optical fiber gyroscope light source device of the present invention. In the figure, parts with the same reference numerals as in FIG. 1 represent the same parts. As shown in the figure, the noise suppressor 20 of the light source device for an optical fiber gyroscope of the present invention includes a beam splitter 21, a photodetector 22, a feedback controller 23, and a filter circuit 24.

The beam splitter 21 splits the light emitted from the broadband light source 10. Specifically, the light is divided into light directed toward the interference type optical fiber gyroscope 1 and light directed toward a photodetector 22, which will be described later.

The photodetector 22 converts the light split by the beam splitter 21 into electrical signals. The photodetector 22 receives the light split by the beam splitter 21, that is, the light from the broadband light source 10, and detects the light intensity signal of this light as an electrical signal.

The feedback control unit 23 performs feedback control of the broadband light source 10 using the electrical signal converted by the photodetector 22. Specifically, the feedback control unit 23 may control the drive current of the broadband light source 10, for example. For example, when an SLD light source is used as the broadband light source 10, there is a strong correlation between drive current and output light intensity of the SLD light source. Therefore, the photodetector 22 detects fluctuations in the light emitted from the SLD light source, and the feedback control section 23 performs feedback control of the drive current of the SLD light source so as to cancel out the fluctuations.

The filter circuit 24 extracts, from the electrical signal converted by the photodetector 22, an electrical signal corresponding to a frequency that is an odd multiple of the n-th harmonic of the natural frequency of the optical fiber coil 7. That is, when the modulation signal used in the phase modulation signal generator 4 of the optical fiber gyroscope 1 described using _{FIG .} Any bandpass filter that can extract the signal may be used.

The feedback control unit 23 performs feedback control of the broadband light source 10 using the electrical signal extracted by the filter circuit 24 . As a result, feedback control is performed using a signal of frequency ν _m , so it becomes possible to suppress the influence of noise at frequency ν _m . As a result, it becomes possible to suppress the RIN of the frequency ν _m of the light emitted from the broadband light source 10. Note that since it is sufficient to suppress the signal of frequency ν _m , feedback control may be performed using, for example, a low-pass filter that passes all signals of frequency ν _m or lower.

FIG. 4 is a conceptual graph for explaining how the RIN of the frequency ν _m of light emitted from the broadband light source is suppressed by the filter circuit of the noise suppression unit of the optical fiber gyroscope light source device of the present invention. In the figure, the horizontal axis is frequency and the vertical axis is noise intensity. As shown in the figure, it can be seen that RIN is suppressed around the frequency ν _m which is the modulation/demodulation frequency. By driving the optical fiber gyroscope 1 using light with the RIN of the modulation/demodulation frequency suppressed in this way, it becomes possible to suppress the RIN of the optical fiber gyroscope 1.

At first glance, since the optical fiber gyroscope 1 modulates and demodulates at the frequency ν _m , it seems that the light source device for the optical fiber gyroscope should also perform feedback control using only the signal at the frequency ν _m . . However, although the effect is high even with just the frequency ν _m , it was discovered for the first time that frequencies that are odd multiples of the n-th harmonic, such as the frequency 3ν _m and the frequency 5ν _m , also affect the output signal as noise. That is, it has been found that feedback control using not only a frequency of 1 ν _m but also a signal having a frequency of an odd multiple of the n-th harmonic, such as a frequency of 3 ν _m or a frequency of ₅ ν m, is more effective. The short-term stability can be further improved by using signals having a frequency of a plurality of odd multiples, such as a frequency of 3v _m , than in the case of a _frequency of 1vm.

A specific example of using signals of a plurality of odd-numbered frequencies in this way will be described. FIG. 5 is a schematic block diagram for explaining another specific example of the noise suppression section of the light source device for an optical fiber gyroscope according to the present invention. In the figure, parts with the same reference numerals as in FIG. 3 represent the same parts. As shown in the figure, the noise suppressor 20 of the optical fiber gyroscope light source device of the present invention further includes a signal distributor 25 in addition to the configuration shown in FIG. The signal distributor 25 divides the electrical signal converted by the photodetector 22 into a plurality of electrical signals. As shown in the illustrated example, the photodetector 22 may be one that divides the electrical signal into three, for example.

Then, the filter circuit 24 extracts a plurality of electrical signals having frequencies that are different odd multiples of the n-th harmonic of the natural frequency of the optical fiber coil from the plurality of electrical signals divided by the signal splitter 25. Any filter consisting of a plurality of band pass filters (BPF) 24a, 24b, and 24c may be used. That is, it is sufficient to prepare a plurality of bandpass filters according to the number of signals distributed by the signal distributor 25. The plurality of bandpass filters 24a, 24b, and 24c are capable of extracting signals with a frequency of _1vm , a frequency of _3vm , and a frequency of _5vm , respectively.

By using the signal splitter 25 and filter circuit 24 having such a configuration, the feedback control unit 23 can feedback the broadband light source 10 using a plurality of electrical signals extracted by a plurality of bandpass filters 24a, 24b, and 24c. Can be controlled. Note that the plurality of odd frequency signals is not necessarily limited to three as in the illustrated example.

FIG. 6 is a diagram for explaining how RIN of a plurality of odd multiple frequencies of light emitted from a broadband light source is suppressed by a plurality of bandpass filters of a noise suppression section of a light source device for an optical fiber gyroscope according to the present invention. This is an actual measurement graph. In the figure, the horizontal axis is frequency and the vertical axis is noise intensity. This example is an output signal of a light source device for an optical fiber gyroscope when RIN with a frequency of 1 ν _m and a frequency of 3 ν _m is suppressed. Further, the output signal of the optical fiber gyroscope light source device when RIN of frequencies 1v _m and 3v _m is suppressed is represented by a black line, and the signal output when RIN is not suppressed is represented by a gray line. As shown in the figure, it can be seen that RIN is suppressed around frequencies 1v _m and 3v _m , which are modulation/demodulation frequencies.

Although an example has been described in which bandpass filters are used to suppress individual odd-numbered multiples of frequencies, the present invention is not limited to this, and may be applied to a low-pass filter that passes all signals of multiple odd-numbered frequencies. Feedback control may also be performed using .

FIG. 7 is a sensitivity graph for explaining the suppression effect of RIN on the output of an optical fiber gyroscope by the optical fiber gyroscope light source device of the present invention. In the figure, the horizontal axis is the modulation index, and the vertical axis is the sensitivity (ARW (Angle Random Walk). As shown in the figure, the frequency It can be seen that when the RIN of 1ν _m is suppressed, the ARW is kept very low.Furthermore, when the two RINs of the frequency 1ν _m and the frequency 3ν _m are suppressed, the ARW is kept even lower. Furthermore, it can be seen that even when three RINs of frequency 1ν _m , frequency 3ν _m , and frequency 5ν _m are suppressed, the ARW is suppressed lower than when two RINs are suppressed. Furthermore, by suppressing RIN at frequencies that are odd multiples of the high frequency, _ARW can be further _{suppressed.However} , according to FIG. That is, it can be seen that it is necessary and sufficient to suppress the RIN of at least one frequency and three times the frequency, and is most efficient.

Next, another specific example of the noise suppressor 20 will be described. FIG. 8 is a schematic block diagram for explaining still another specific example of the noise suppression section of the optical fiber gyroscope light source device of the present invention. In the figure, parts with the same reference numerals as in FIG. 3 represent the same parts. As shown in the figure, the noise suppression section 20 of the light source device for an optical fiber gyroscope of the present invention includes a beam splitter 21, a photodetector 22, and a feedback control section 23. That is, the noise suppressor 20 shown in FIG. 8 does not include the filter circuit 24 used in the noise suppressor 20 shown in FIG. 3. When the light source device for an optical fiber gyroscope of the present invention is used to drive an interference type optical fiber gyroscope 1 that uses an optical fiber coil 7 having a low natural frequency, modulation can be performed without using the filter circuit 24. - It may be possible to suppress the RIN of the demodulation frequency. For example, when using an optical fiber coil with a low natural frequency such that the frequency of an odd multiple of the n-th harmonic is lower than the cutoff frequency of the feedback control unit 23 described above, the cutoff frequency of the feedback control unit 23 The function is similar to that of a filter circuit, specifically a low-pass filter. That is, when the frequency 1v _m is lower than the cutoff frequency of the feedback control unit 23, RIN including the frequency 1v _m lower than the cutoff frequency is suppressed by the feedback control. Note that when suppressing multiple RINs, if the frequency 3ν _m is lower than the cutoff frequency of the feedback control unit 23, for example, all RINs including the frequency 1ν _m and the frequency 3ν _m will be suppressed. .

Furthermore, the noise suppression section is not limited to the illustrated example described above, as long as it can suppress frequencies that are odd multiples of the n-th harmonic of the natural frequency of the optical fiber coil. For example, the noise suppressor 20 in FIG. 1 may be composed of an intensity modulator. That is, the intensity modulator may be of any type as long as it is capable of suppressing the light intensity at a frequency of 1 ν _m , for example. Furthermore, it may be possible to suppress the light intensity not only at a frequency of 1v _m but also at a frequency of 3v _m or a frequency of 5v _m . By suppressing the light intensity of a specific frequency as described above using an intensity modulator, the RIN of the modulation/demodulation frequency of light from a broadband light source is suppressed, and the RIN of the optical fiber gyroscope is suppressed. It is possible to suppress it.

Furthermore, the noise suppression section 20 may be composed of a semiconductor optical amplifier. Similar to the intensity modulator described above, by attenuating light at a specific frequency as described above using a semiconductor optical amplifier, the RIN of the modulation/demodulation frequency of light from a broadband light source is suppressed, and the optical fiber The RIN of the gyroscope can be suppressed.

As described above, according to the light source device for an optical fiber gyroscope of the present invention, by suppressing the RIN of the modulation/demodulation frequency that can be a problem in the optical fiber gyroscope in advance on the light source device side for the optical fiber gyroscope, RIN that may occur in an optical fiber gyroscope can be suppressed. This can improve the short-term stability of the fiber optic gyroscope.

Note that the light source device for an optical fiber gyroscope of the present invention is not limited to the illustrated example described above, and it goes without saying that various changes can be made without departing from the gist of the present invention.

1 Interferometric fiber optic gyroscope 2 Optical circulator 3 Multifunctional integrated optical circuit 3a Polarizer 3b Y branch/recombiner 3c First phase modulator 3d Second phase modulator 4 Phase modulation signal generator 5 Photodetector 6 Synchronization Detector 7 Optical fiber coil 10 Broadband light source 20 Noise suppression section 21 Beam splitter 22 Photodetector 23 Feedback control section 24 Filter circuit 24a, 24b, 24c Band pass filter 25 Signal distributor

Claims (9)

A light source device for an optical fiber gyroscope for driving an interference type optical fiber gyroscope using an optical fiber coil, the light source device for an optical fiber gyroscope includes:
a broadband light source that emits light with relative intensity noise;
suppressing relative intensity noise of frequencies that are odd multiples of the n-th harmonic (n=1, 2, 3...) of the natural frequency of the optical fiber coil with respect to the relative intensity noise of light emitted from the broadband light source; a noise suppression section;
A light source device for an optical fiber gyroscope, comprising: In the light source device for an optical fiber gyroscope according to claim 1, the noise suppressor comprises:
a beam splitter that splits light emitted from the broadband light source;
a photodetector that converts the light split by the beam splitter into an electrical signal;
a feedback control unit that performs feedback control of the broadband light source using the electrical signal converted by the photodetector;
A light source device for an optical fiber gyroscope, comprising: 3. The light source device for an optical fiber gyroscope according to claim 2, wherein the noise suppressing section further comprises, for the electric signal converted by the photodetector, an odd number multiple of the n-th harmonic of the natural frequency of the optical fiber coil. Equipped with a filter circuit that extracts an electrical signal corresponding to the frequency of
The feedback control unit feedback-controls the broadband light source using the electrical signal extracted by the filter circuit.
A light source device for an optical fiber gyroscope, characterized in that: 4. The light source device for an optical fiber gyroscope according to claim 3, wherein the noise suppression section further includes a signal splitter that divides the electrical signal converted by the photodetector into a plurality of electrical signals.
The filter circuit extracts a plurality of electrical signals each having a frequency that is a different odd multiple of the n-th harmonic of the natural frequency of the optical fiber coil from the plurality of electrical signals divided by the signal splitter. Consists of a pass filter,
The feedback control unit performs feedback control of the broadband light source using a plurality of electrical signals extracted by a plurality of bandpass filters.
A light source device for an optical fiber gyroscope, characterized in that: 5. The light source device for an optical fiber gyroscope according to claim 4, wherein the noise suppression unit suppresses relative intensity noise at a frequency at least one time and three times the n-th harmonic of the natural frequency of the optical fiber coil. A light source device for an optical fiber gyroscope, characterized in that: The light source device for an optical fiber gyroscope according to claim 2, wherein the light source device for an optical fiber gyroscope is configured such that the frequency of an odd multiple of the n-th harmonic is lower than the cutoff frequency of the feedback control section. A light source device for an optical fiber gyroscope, characterized in that it drives an interference type optical fiber gyroscope using an optical fiber coil with a low natural frequency. The light source device for an optical fiber gyroscope according to any one of claims 2 to 6, wherein the feedback control section controls a drive current of the broadband light source. 2. The light source device for an optical fiber gyroscope according to claim 1, wherein the noise suppression section includes an intensity modulator that suppresses frequencies that are odd multiples of the n-th harmonic of the natural frequency of the optical fiber coil. Light source device for optical fiber gyroscope. 2. The light source device for an optical fiber gyroscope according to claim 1, wherein the noise suppression section is comprised of a semiconductor optical amplifier that suppresses frequencies that are odd multiples of the n-th harmonic of the natural frequency of the optical fiber coil. Light source device for optical fiber gyroscope.

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