JP5224213B2 - Fiber optic gyro - Google Patents

Description

  The present invention detects the rotational angular velocity of a looped optical fiber based on the frequency difference generated between the clockwise light propagating clockwise in the looped optical fiber and the counterclockwise light propagating counterclockwise. In particular, the present invention relates to a technique for increasing the detection accuracy of a rotational angular velocity.

  A loop-shaped optical fiber, a clockwise light propagating clockwise in the loop-shaped optical fiber inserted in a state optically coupled to a predetermined position of the loop-shaped optical fiber, and a counter-current propagating counterclockwise An optical signal amplifying device for amplifying each clockwise light, and rotation of the loop optical fiber based on a frequency difference generated between the clockwise light and the counterclockwise light propagating in the loop optical fiber. Optical fiber gyros that detect angular velocity are known. For example, this is an optical fiber gyro described in Patent Document 1.

According to this optical fiber gyroscope, many optical couplers, that is, optical couplers, are provided to amplify laser light propagating clockwise and counterclockwise in the loop optical fiber, and are amplified via the optical coupler. There is an advantage that the structure of the optical fiber gyro is simplified as compared with a conventional brilliant type optical fiber gyro that amplifies laser light by light.
JP 2001-71614 A

  By the way, in the above optical fiber gyro, due to the relationship between the preset beat frequency and the rotational angular velocity, it is caused by the frequency difference generated between the clockwise light and the counterclockwise light propagating in the loop optical fiber. The rotational angular velocity is calculated on the basis of the frequency of the beat signal generated. However, the clockwise light and the counterclockwise light propagating in the loop-shaped optical fiber are not in a constant wavelength such as oscillated by an optical resonator, although they are in a steady state with relatively uniform wavelengths. Is not sufficiently high, the peak of the beat signal generated by the frequency difference between them is not obtained sharply, and the beat frequency obtained from the analysis of the beat signal and the accuracy of the rotational angular velocity obtained from the beat frequency are sufficiently obtained. There were cases where it was not possible.

  The present invention has been made in the background of the above circumstances, and an object of the present invention is to provide an optical fiber gyro having a simple structure and capable of detecting a rotational angular velocity with high accuracy.

  That is, the invention according to claim 1 for achieving the above object includes: (a) a loop-shaped optical fiber and the loop-shaped optical fiber inserted in a state optically coupled to a predetermined position of the loop-shaped optical fiber. An optical signal amplifying device for amplifying the clockwise light propagating clockwise in the optical fiber and the counterclockwise light propagating counterclockwise, respectively, and the clockwise light and counterclockwise propagating in the loop optical fiber An optical fiber gyro that detects a rotational angular velocity of the loop optical fiber based on a frequency difference generated between directional lights, wherein (b) the optical signal amplifying device is (b-1) the clockwise light. When the counterclockwise light and the counterclockwise light are input, the clockwise light and the counterclockwise light are respectively amplified and output, and the clockwise light and the intensity of the clockwise light and the counterclockwise light are inverted. Counterclock A semiconductor optical amplifier that emits ambient light other than the wavelength of the counter light; and (b-2) all or part of the ambient light other than the wavelengths of the clockwise light and the counterclockwise light emitted from the semiconductor optical amplifier. And a wavelength-selective reflecting element that reflects and enters the semiconductor optical amplifier.

  The invention according to claim 2 is the optical fiber gyroscope according to claim 1, wherein (c) the wavelength-selective reflecting element is one end of the loop-shaped optical fiber optically coupled to the semiconductor optical amplifier. Of the light emitted from the semiconductor optical amplifier and reflecting all or part of ambient light other than the wavelengths of the clockwise light and the counterclockwise light among the light emitted from the semiconductor optical amplifier. It is an optical fiber grating portion that is incident on an amplifier.

  According to a third aspect of the present invention, in the optical fiber gyro according to the second aspect, (d) a tip lens is provided on an end surface of the end portion of the loop optical fiber where the optical fiber grating portion is provided. The output light from the semiconductor optical amplifier is directly incident on the tip lens.

  The invention according to claim 4 is the optical fiber gyro according to any one of claims 1 to 3, wherein (e) the semiconductor optical amplifier is a semiconductor optical amplifier including an active layer made of a pn junction. The active layer is composed of a bulk, a quantum well, a strained superlattice, or a quantum dot.

  The invention according to claim 5 is the optical fiber gyro according to any one of claims 1 to 4, wherein (f) the clockwise light propagating in the loop optical fiber is provided in the loop optical fiber. A bidirectional light extraction optical coupler that respectively extracts a part of the light and a part of the counterclockwise light; and (g) a part of the clockwise light extracted from the loop optical fiber by the bidirectional light extraction coupler. An optical multiplexing element that multiplexes a part of the clockwise light and outputs beat light caused by a frequency difference generated between the clockwise light and the counterclockwise light; and (h) the optical multiplexing element A combined light detector that converts the combined beat light into an electrical signal; (i) a frequency analysis unit that analyzes the frequency of the beat signal included in the electrical signal converted by the combined light detector; and (j) From the pre-stored relationship, the frequency analyzer Ri and rotational angular velocity calculating unit for calculating a rotational angular velocity of the loop shaped optical fiber on the basis of the frequency of the analyzed beat signal, characterized in that it contains.

  According to a sixth aspect of the present invention, there is provided (a) a loop-shaped optical fiber and a loop-shaped optical fiber inserted in a state optically coupled to a predetermined position of the loop-shaped optical fiber in a clockwise direction. An optical signal amplifying device for amplifying the propagating clockwise light and the counterclockwise light propagating in the counterclockwise direction, and is generated between the clockwise light and the counterclockwise light propagating in the loop optical fiber. An optical fiber gyro that detects a rotational angular velocity of the loop optical fiber based on a frequency difference between the optical fiber and the optical signal amplifying device; (b-1) when the clockwise light is input, A first semiconductor optical amplifier that amplifies and outputs clockwise light and emits first ambient light other than the wavelength of the clockwise light that is inverted in intensity with respect to the intensity of the clockwise light; (b-2) Before being emitted from the first semiconductor optical amplifier to the input side A first wavelength-selective reflecting element that reflects all or part of the first ambient light to enter the first semiconductor optical amplifier; and (b-3) when the counterclockwise light is input, A second semiconductor optical amplifier that amplifies and outputs directional light and emits second ambient light other than the wavelength of the counterclockwise light that is inverted in intensity with respect to the intensity of the counterclockwise light; (b-4) A second wavelength-selective reflecting element that reflects all or part of the second ambient light emitted from the second semiconductor optical amplifier to the input side and enters the second semiconductor optical amplifier; and (b-5) A third wavelength-selective reflecting element that reflects all or part of the first ambient light radiated from the first semiconductor optical amplifier to the output side and enters the output side of the second semiconductor optical amplifier; b-6) A part of the counterclockwise light in the loop optical fiber is taken out and output from the second semiconductor optical amplifier. And an optical coupler that causes the output light of the first semiconductor optical amplifier and the second semiconductor optical amplifier to enter the loop optical fiber as clockwise light.

  The invention according to claim 7 is the optical fiber gyroscope according to claim 6, wherein: (c) the first wavelength-selective reflective element is the loop shape optically coupled to the first semiconductor optical amplifier. A first light that is provided at one of the one end and the other end of the optical fiber and reflects all or part of the first ambient light emitted from the first semiconductor optical amplifier to enter the first semiconductor optical amplifier. (D) the second wavelength selective reflection element is provided on the other end of the loop-shaped optical fiber optically coupled to the second semiconductor optical amplifier, It is a second optical fiber grating part that reflects all or a part of the second ambient light emitted from the second semiconductor optical amplifier and makes it incident on the second semiconductor optical amplifier.

  The invention according to claim 8 is the optical fiber gyro according to claim 7, wherein (e) both end portions of the loop optical fiber provided with the first optical fiber grating portion and the second optical fiber grating portion are provided. Each of the first and second semiconductor optical amplifiers is provided with a front-end lens, and output light from the first and second semiconductor optical amplifiers is directly incident on the front-end lens.

  The invention according to claim 9 is the optical fiber gyro according to any one of claims 6 to 8, wherein (f) a first optically coupled to the output side of the first semiconductor optical amplifier and the second semiconductor optical amplifier. A Y-shaped fiber comprising a one-branch fiber portion and a second branch fiber portion, and a common fiber portion in which the first branch fiber and the second branch fiber are melt-drawn and coupled to the optical coupler; The third wavelength selective reflection element is provided in the common fiber portion, reflects all or a part of the first ambient light emitted from the first semiconductor optical amplifier, and outputs the second semiconductor optical amplifier. It is the 3rd optical fiber grating part made to enter into the side, It is characterized by the above-mentioned.

  According to a tenth aspect of the present invention, in the optical fiber gyro according to any one of the sixth to ninth aspects, (h) the first semiconductor optical amplifier and the second semiconductor optical amplifier each include an active layer made of a pn junction. The semiconductor optical amplifier is characterized in that the active layer is composed of a bulk, a quantum well, a strained superlattice, or a quantum dot.

  The invention according to claim 11 is the optical fiber gyro according to any one of claims 6 to 10, wherein (i) the clockwise light propagating in the loop optical fiber is provided in the loop optical fiber. A bidirectional light extraction optical coupler that extracts a part of the light and a part of the counterclockwise light, respectively, and (j) a part of the clockwise light extracted from the loop optical fiber by the bidirectional light extraction coupler An optical multiplexing element that multiplexes a part of the clockwise light and outputs beat light caused by the frequency difference generated between the clockwise light and the counterclockwise light; and (k) the optical multiplexing element A combined light detector that converts the combined beat light into an electrical signal; (l) a frequency analysis unit that analyzes the frequency of the beat signal included in the electrical signal converted by the combined light detector; and (m) Frequency analysis from pre-stored relationships A rotational angular velocity calculating unit for calculating a rotational angular velocity of the loop shaped optical fiber on the basis of the frequency of the analyzed beat signal by, characterized in that it contains.

  According to the optical fiber gyro of the invention according to claim 1, when the optical signal amplifying device (b-1) receives the clockwise light and the counterclockwise light, the clockwise light and the counterclockwise light are respectively received. A semiconductor optical amplifier that amplifies and outputs and emits ambient light other than the wavelength of the clockwise and counterclockwise light that is inverted in intensity relative to the intensity of the clockwise and counterclockwise light; and (b- 2) a wavelength-selective reflecting element that reflects all or part of ambient light other than the wavelengths of the clockwise light and counterclockwise light emitted from the semiconductor optical amplifier and enters the semiconductor optical amplifier; Since all or a part of the ambient light other than the wavelengths of the clockwise light and the counterclockwise light is reflected by the wavelength selective reflection element and input again to the semiconductor optical amplifier, the ambient light indicating the intensity inversion is fed back. Et Since negative feedback light amplification effect by modulating in accordance with the input optical signal gain of the semiconductor optical amplifier is obtained by Rukoto, distortion of the clockwise light and the counterclockwise direction light wave is reduced. As a result, the degree of modulation of the clockwise light and the counterclockwise light is increased, so that the peak of the beat signal generated by the frequency difference between them is sharply obtained, and the beat frequency obtained from the analysis of the beat signal and the beat frequency are obtained. The accuracy of the rotational angular velocity obtained from the above is sufficiently obtained.

  According to the optical fiber gyro of the invention according to claim 2, the wavelength selective reflection element is at least one of one end and the other end of the loop optical fiber optically coupled to the semiconductor optical amplifier. An optical fiber grating unit that reflects all or part of ambient light other than the wavelengths of the clockwise light and the counterclockwise light out of the light emitted from the semiconductor optical amplifier so as to be incident on the semiconductor optical amplifier Therefore, the optical coupling structure between the semiconductor optical amplifier and the end of the loop optical fiber is simple and small.

  According to the optical fiber gyro of the invention according to claim 3, a tip ball lens is provided on an end face of the loop optical fiber where the optical fiber grating portion is provided, and the output from the semiconductor optical amplifier is provided. Since light is directly incident on the tip lens, the optical coupling structure between the semiconductor optical amplifier and the end of the loop optical fiber becomes simpler and smaller.

  According to the optical fiber gyro of the invention according to claim 4, the semiconductor optical amplifier is a semiconductor optical amplifier provided with an active layer made of a pn junction, and the active layer includes a bulk, a quantum well, and a strained superlattice. Or an optical signal amplifying device that is further miniaturized and can be made into one chip, and particularly when an active layer is configured from quantum wells and quantum dots, Since the signal can be amplified in the high frequency region of the order of 10 GHz and the frequencies of the clockwise light and the counterclockwise light are increased, the accuracy of the rotational angular velocity obtained from the beat frequency is further enhanced.

  According to the optical fiber gyro of the invention according to claim 5, a part of the clockwise light and a part of the counterclockwise light, which are provided in the loop optical fiber and propagate in the loop optical fiber, respectively. Bidirectional light extraction optical coupler to be extracted, and a part of clockwise light and a part of counterclockwise light extracted from the loop-shaped optical fiber by the bidirectional light extraction coupler to each other, An optical multiplexing element that outputs beat light resulting from a frequency difference generated between the light and the counterclockwise light, and a combined optical detector that converts the beat light combined by the optical multiplexing element into an electrical signal; A frequency analysis unit that analyzes the frequency of the beat signal included in the electrical signal converted by the combined optical detector, and a frequency based on the frequency of the beat signal that is analyzed by the frequency analysis unit from a previously stored relationship. A rotational angular velocity calculating unit for calculating a rotational angular velocity of the loop shaped optical fiber, since it contains, has a simple structure, it is possible to obtain a fiber-optic gyroscope which can detect the rotational angular velocity with high accuracy.

  According to the optical fiber gyro of the invention of claim 6, the optical signal amplifying device (b-1) amplifies and outputs the clockwise light when the clockwise light is input, and A first semiconductor optical amplifier that emits first ambient light other than the wavelength of the clockwise light that is inverted in intensity with respect to the intensity of the clockwise light; and (b-2) emitted from the first semiconductor optical amplifier to the input side. A first wavelength-selective reflecting element that reflects all or part of the first ambient light to be incident on the first semiconductor optical amplifier; and (b-3) when the counterclockwise light is input, A second semiconductor optical amplifier that amplifies and outputs the counterclockwise light and emits second ambient light other than the wavelength of the counterclockwise light that is inverted in intensity with respect to the intensity of the counterclockwise light; -4) Reflecting all or part of the second ambient light emitted from the second semiconductor optical amplifier to the input side, A second wavelength-selective reflecting element to be incident on the semiconductor optical amplifier; and (b-5) reflecting all or part of the first ambient light radiated from the first semiconductor optical amplifier to the output side, A third wavelength-selective reflecting element incident on the output side of the semiconductor optical amplifier; and (b-6) extracting a part of the counterclockwise light in the loop-shaped optical fiber to the output side of the second semiconductor optical amplifier. And an optical coupler that causes the output light of the first semiconductor optical amplifier and the second semiconductor optical amplifier to enter the loop optical fiber as clockwise light, and includes the clockwise light and the counterclockwise light. Since all or part of the ambient light other than the wavelength is reflected by the first wavelength selective reflection element and the second wavelength selective reflection element and is input again to the first semiconductor optical amplifier and the second semiconductor optical amplifier, it is compact. 3 terminal light In addition to obtaining a signal amplifying device, the gain of the semiconductor optical amplifier is modulated according to the input optical signal by feeding back the ambient light indicating the intensity inversion, so that a negative feedback optical amplification effect can be obtained. Counterclockwise light waveform distortion is reduced. As a result, the degree of modulation of the clockwise light and the counterclockwise light is increased, so that the peak of the beat signal generated by the frequency difference between them is sharply obtained, and the beat frequency obtained from the analysis of the beat signal and the beat frequency are obtained. The accuracy of the rotational angular velocity obtained from the above is sufficiently obtained.

  Further, according to the optical fiber gyro of the invention according to claim 7, the first wavelength selective reflection element includes one end and the other end of the loop optical fiber optically coupled to the first semiconductor optical amplifier. A first optical fiber grating unit that is provided on one side of the unit and reflects all or a part of the first ambient light emitted from the first semiconductor optical amplifier to enter the first semiconductor optical amplifier; The two-wavelength selective reflection element is provided on the other end of the loop-shaped optical fiber optically coupled to the second semiconductor optical amplifier, and is radiated from the second semiconductor optical amplifier. 2 Since the second optical fiber grating unit reflects all or part of the ambient light and enters the second semiconductor optical amplifier, the first semiconductor optical amplifier, the second semiconductor optical amplifier, and the loop optical fiber Optical coupling structure between the both ends simply and becomes compact.

  According to the optical fiber gyro of the invention according to claim 8, in the optical fiber gyro according to claim 7, (e) the first optical fiber grating portion and the second optical fiber grating portion of the loop optical fiber. Since the front spherical lenses are respectively provided on the end surfaces of the both ends provided with the first semiconductor optical amplifier, the output light from the first semiconductor optical amplifier and the second semiconductor optical amplifier is directly incident on the front spherical lens. The optical coupling structure between the optical amplifier, the second semiconductor optical amplifier, and both ends provided with the first optical fiber grating portion and the second optical fiber grating portion of the loop optical fiber becomes simpler and smaller.

  According to the optical fiber gyro of the invention according to claim 9, a first branch fiber portion and a second branch fiber portion optically coupled to the output sides of the first semiconductor optical amplifier and the second semiconductor optical amplifier, A third fiber having a Y-shaped fiber including a common fiber portion in which the first branch fiber and the second branch fiber are melt-drawn and coupled to the optical coupler, and the third wavelength selective reflection element includes the common fiber portion. A third optical fiber grating part that reflects all or part of the first ambient light emitted from the first semiconductor optical amplifier and makes it incident on the output side of the second semiconductor optical amplifier, A small three-terminal optical signal amplifier can be applied to the optical fiber gyro.

  According to the optical fiber gyro of the invention of claim 10, the first semiconductor optical amplifier and the second semiconductor optical amplifier are semiconductor optical amplifiers having an active layer made of a pn junction, and the active layer is Since it is composed of a bulk, a quantum well, a strained superlattice, or a quantum dot, the optical signal amplifying device can be further miniaturized and made into one chip. Is configured, signal amplification is possible in a high frequency region of the order of 10 GHz, and the frequencies of the clockwise light and the counterclockwise light are increased. Therefore, the accuracy of the rotational angular velocity obtained from the beat frequency is further increased. Enhanced.

  According to the optical fiber gyro of the invention according to claim 11, a part of the clockwise light and a part of the counterclockwise light that are provided in the loop optical fiber and propagate in the loop optical fiber, respectively. Bidirectional light extraction optical coupler to be extracted, and a part of clockwise light and a part of counterclockwise light extracted from the loop-shaped optical fiber by the bidirectional light extraction coupler to each other, An optical multiplexing element that outputs beat light resulting from a frequency difference generated between the light and the counterclockwise light, and a combined optical detector that converts the beat light combined by the optical multiplexing element into an electrical signal; Based on the frequency of the beat signal analyzed by the frequency analysis unit from a pre-stored relationship, the frequency analysis unit for analyzing the frequency of the beat signal included in the electrical signal converted by the combined optical detector A rotational angular velocity calculating unit for calculating a rotational angular velocity of the serial looped optical fiber, since it contains, has a simple structure, it is possible to obtain a fiber-optic gyroscope which can detect the rotational angular velocity with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings used for the following description, the dimensional ratios of the respective parts are not necessarily drawn accurately. Needless to say, optical elements such as an optical fiber, an optical coupler, and an optical fiber grating section described later have reversibility.

  FIG. 1 is a diagram showing a configuration of an optical fiber gyroscope 10 according to an embodiment of the present invention. The optical fiber gyro 10 is inserted in a looped optical fiber 12 formed in an annular shape and a predetermined position of the looped optical fiber 12 in an optically coupled state, and circulates in the looped optical fiber 12 in both directions. The optical signal amplifying device 14 that amplifies the pair of clockwise light Lcw and counterclockwise light Lccw and the optical signal amplifying device 14 of the loop optical fiber 12 are provided at predetermined positions different from those in the loop optical fiber 12. Bidirectionally extracting, for example, about 1% of a part of the clockwise light Lcw having the wavelength λ1 and a part of the counterclockwise light Lccw propagating in the counterclockwise direction having the wavelength λ1. An optical coupler 16 for extracting light, a part of the clockwise light Lcw extracted by the optical coupler 16 and transmitted through the pair of transmission optical fibers 18 and counterclockwise A portion of the counterclockwise light Lccw propagating in the direction is combined with each other to output combined light, that is, beat light Lb formed by the frequency difference Δf, and beat light from the optical combiner 20 The photodetector 22 that receives and converts the beat signal SB, which is an electrical signal, and outputs it, and the frequency analysis of the beat signal SB output from the photodetector 20, and the frequency fp of the peak point P of the beat signal SB is obtained. A rotational angular velocity for calculating the rotational angular velocity ω of the loop-shaped optical fiber 12 based on the frequency fp to be output and the frequency fp of the peak point P of the beat signal SB analyzed by the frequency analyzing portion 24 from the relationship stored in advance. And a calculation unit 26.

  The loop optical fiber 12 is formed in an annular shape having a diameter of about 1 m, for example, and is fixed to a frame or a case (not shown) of the optical fiber gyro 10. The loop-shaped optical fiber 12 and the transmission optical fiber 18 are, for example, a clad type or self-hoc type optical fiber having cores 12c and 18c having a refractive index of about 1.4, as shown in FIG. . FIG. 2 shows a configuration example of the optical coupler 16. The optical coupler 16 is in a state where the loop-shaped optical fiber 12 and the transmission light 18 are in contact with each other by a predetermined length so that about 1% of light leaks between the cores 12c and 18c of the loop-shaped optical fiber 12 and the transmission optical fiber 18. A holder 28 for holding the fiber 18 is provided, and the loop optical fiber 12 and the transmission optical fiber 18 are optically coupled to each other.

  The optical multiplexer 20 melts and extends the ends of the pair of transmission optical fibers 18, for example, so that a part of the clockwise light Lcw respectively transmitted by the pair of transmission optical fibers 18 and the counterclockwise direction. Part of the propagating counterclockwise light Lccw is multiplexed with each other at a ratio of 1: 1, for example. This combined light has a frequency difference Δf (= fcw−fccc) between the frequency fcw of the clockwise light Lcw circulated constantly in the loop optical fiber 12 and the frequency fcw of the counterclockwise light Lccw. When generated, it becomes beat light Lb having the same beat frequency fb as the frequency difference Δf. The photodetector 20 includes a photosensor such as a well-known photocell or phototransistor and a square wave detection circuit, and receives the beat light Lb and outputs a beat signal SB representing the pulsation.

  The frequency analysis unit 24 includes calculation means such as a microcomputer, for example, and the calculation means is well known on the basis of the frequency sine wave superposition using the Fourier transform. The frequency characteristics of the input signal is analyzed, and the peak frequency of the input signal, that is, the frequency fp of the peak point P of the beat signal SB is output. The rotational angular velocity calculation unit 26 includes calculation means such as a microcomputer, for example, and the calculation means calculates the beat frequency of the beat signal SB analyzed by the frequency analysis unit 24 from the pre-stored relationship shown in FIG. The rotational angular velocity ω of the loop optical fiber 12 is calculated based on the frequency difference Δf between fb, that is, the frequency fcw of the clockwise light Lcw and the frequency fcw of the counterclockwise light Lccw.

  The measurement principle of the optical fiber gyro 10 configured as described above will be described below. (Electric field) intensity Icw of the clockwise light Lcw and the counterclockwise light Lccw that are circulated at a constant intensity by the bidirectional optical amplification by the optical signal amplifier 14 in the loop optical fiber 12. And Iccw are expressed by the following equations (1) and (2). acw and accw indicate the amplitude, and φcw and φccw indicate the phase. When the clockwise light Lcw and the counterclockwise light Lccw are combined (superposed), the intensity I of the combined light detected by the photodetector 20 is expressed by the following equation: Since it is the square of the added value, it is expressed by the following equation (3). In equation (3), Δ = φcw−φccw.

Icw = acw · cos (2πfcwt + φcw) (1)
Iccw = accw ・ cos (2πfccc t + φccw) (2)
I = (Icw + Iccw) ²
= (Acw ² + accw ² ) / 2 + 2 acwaccw · cos (2πfb t + Δ) ··· (3)

From the above equation (3), since the direct current component of the intensity I of the combined light is (acw ² + accw ² ) / 2 and the alternating current component is 2 acwaccw · cos (2πfb t + Δ), the photodetector 20 By receiving the light Lb and performing its square detection, an alternating current component is extracted from the intensity I of the combined light, and a beat signal SB that is the alternating current component is output. The beat frequency fb of the beat signal SB is explained by the following theoretical formula (4). In equation (4), A is the area surrounded by the loop optical fiber 12, n is the refractive index of the loop optical fiber 12, λ1 is the wavelength of the clockwise light Lcw and the counterclockwise light Lccw, and P is the clockwise light. Lcw and the path length (optical path length) of the counterclockwise light Lccw, ω is the rotational angular velocity of the loop optical fiber 12.

fb = (4A / (n · λ1 · P)) ω (4)

  The relationship between the frequency fb of the beat signal SB and the power Wb of the beat signal SB is as shown in FIG. 4 for each rotation angular velocity of the loop optical fiber 12, for example. In FIG. 4, the rotational angular velocity of the loop optical fiber 12 is 10 ° (10 ° / s) per second, 30 ° (30 ° / s) per second, 50 ° (50 ° / s) per second, and 70 ° per second (70 ° / s). s) and the characteristics for the case of 90 ° per second (90 ° / s) are shown. Each beat signal SB has a power peak P, and the frequency when the peak P is formed is specified as the beat frequency fb of the beat signal SB. As apparent from FIG. 4, the beat frequency fb increases as the rotational angular velocity of the loop optical fiber 12 increases. FIG. 3 is preset based on such a relationship. Therefore, the rotation angular velocity calculation unit 26 calculates the beat frequency fb of the beat signal SB analyzed by the frequency analysis unit 24 from the previously stored relationship shown in FIG. 3, that is, the frequency fcw of the clockwise light Lcw and the counterclockwise light Lccw. The rotational angular velocity ω of the loop optical fiber 12 can be calculated based on the frequency difference Δf with respect to the frequency fccw.

  As shown in FIG. 5, for example, the optical signal amplifying apparatus 14 of the present embodiment includes a semiconductor optical amplifier 30 optically coupled between one end 12a and the other end 12b of the loop optical fiber 12, An optical fiber grating portion 32 formed in one of the one end portion 12a and the other end portion 12b (one end portion 12a in this embodiment) is provided in the case 34. The semiconductor optical amplifier 30 amplifies the clockwise light Lcw input from the one end 12a to the end face 30g and the counterclockwise light Lccw input from the other end 12b to the end face 30h and outputs the amplified light from the end face 30h and the end face 30g. Along with the intensity of the clockwise light Lcw and the counterclockwise light Lccw (input light) from the one end 12a and the other end 12b, light other than the wavelength λ1 of the input light, that is, ambient light of wavelength λ1 (naturally generated light) ) Is modulated, and the light amplified from the input light and the light (ambient light) other than the wavelength λ1 whose intensity is inverted with respect to the intensity of the input light are output. The output light obtained by amplifying the input light is light having the same phase with the amplitude of the input light being increased, and is output from the output end face opposite to the incident end face. On the other hand, light (ambient light) other than the wavelength λ1 whose intensity is inverted with respect to the intensity of the input light has a phase inverted with respect to the input light and is output from both end faces. The optical fiber grating unit 32 reflects the ambient light and re-inputs it to the semiconductor optical amplifier 30, and causes the semiconductor optical amplifier 30 to generate a negative feedback light amplification function with a relatively low but extremely stable amplification factor.

  The semiconductor optical amplifier 30 is composed of, for example, a chip-like element shown in FIG. 6, and includes a semiconductor substrate 30a composed of a compound semiconductor, such as indium phosphorus InP, and a III-V group mixed crystal epitaxially grown thereon. An optical waveguide 30b made of a semiconductor and formed of a multilayer film having a relatively high refractive index formed to a predetermined width by photolithography, and a pn junction constituting a part of the multilayer film in the optical waveguide 30b, An active layer 30c composed of any one of a multiple quantum well, a strained superlattice, and a quantum dot, an upper electrode 30e fixed to the upper surface of the optical waveguide 30b, and a lower electrode 30f fixed to the lower surface of the semiconductor substrate 30a Is provided. In a state in which an injection current flows between the upper electrode 30e and the lower electrode 30f, when the input light L having a predetermined wavelength λ1 is incident and propagated through the optical waveguide 30b, the active layer 30c is passed through. The light is amplified by the induced radiation action and output. At the same time, the so-called mutual gain modulation action generates ambient light (naturally generated light) having an ambient wavelength other than the wavelength λ1 except for the wavelength λ1 and the intensity increasing and decreasing in inverse proportion to the intensity modulation of the input light. This is also output. When the injection current is initially supplied, spontaneous emission light having a predetermined wavelength band corresponding to the energy gap in the active layer 30 c is generated in the semiconductor optical amplifier 30, and this circulates in the loop optical fiber 12. It is stabilized and aggregated to a predetermined wavelength λ1. Industrially, a filter or the like is used so that the wavelength λ1 is easily aggregated.

  When the active layer 30c is composed of multiple wells, for example, it is composed of six pairs of InGaAs and InGaP of about 100 nm lattice-matched by being epitaxially grown from the semiconductor substrate 30a, and on the active layer 30c, A guide layer (2000 mm) having a GRIN structure in which the composition (refractive index) is changed stepwise is sequentially provided. The device length of the active layer 30c is, for example, about 600 μm.

  Returning to FIG. 5, the end surfaces of the one end portion 12 a and the other end portion 12 b of the loop optical fiber 12 are each provided with a tip lens R that functions as a convex lens, and the clockwise light Lcw is transmitted from the loop optical fiber 12. The clockwise light Lcw that is directly input from one end 12a to one end face 30g of the semiconductor optical amplifier 30 and amplified is directly output from the other end face 30h to the other end 12b of the loop optical fiber 12, and counterclockwise. The light Lccw is directly input from the other end portion 12b of the loop optical fiber 12 to the other end face 30h of the semiconductor optical amplifier 30, and the counterclockwise light Lccw amplified is sent from one end face 30g to one end portion of the loop optical fiber 12. The data is directly output to 12a. That is, between one end portion 12 a of the loop-shaped optical fiber 12 and one end surface 30 g of the semiconductor optical amplifier 30 and between the other end surface 30 h of the semiconductor optical amplifier 30 and the other end portion 12 b of the loop-shaped optical fiber 12. Are optically coupled directly.

  The optical fiber grating portion 32 formed at the one end portion 12 a of the loop optical fiber 12 reflects ambient light emitted from one end face 30 g of the semiconductor optical amplifier 30 toward the one end portion 12 a of the loop optical fiber 12. By re-inputting to the semiconductor optical amplifier 30, a negative feedback light amplification action is generated, the response performance of the semiconductor optical amplifier 30 is enhanced, the noise of the output light is reduced, the waveform distortion is reduced, and the degree of modulation is increased. The optical fiber grating 32 allows light of wavelength λ1 that is clockwise light Lcw and counterclockwise light Lccw to pass, but reflects ambient light (naturally generated light) having an ambient wavelength other than the light of wavelength λ1. It is a wavelength selective reflection element. The distance between one end face 30g of the semiconductor optical amplifier 30 and the end face of the optical fiber grating section 32, that is, the optical path length L does not decrease the efficiency, and the waveforms of the clockwise light Lcw and the counterclockwise light Lccw are affected. It is set not to receive.

The loop shaped optical fiber 12, for example, a core 12c of substantially cylindrical shape made of quartz SiO ₂ with the addition of germanium Ge, quartz SiO ₂ in a substantially cylindrical shape covering the outer peripheral surface of it and a lower refractive index than the core 12c It is the optical fiber comprised by the grad 12d which is. For example, as shown in FIG. 7, the optical fiber grating portion 32 typically uses a phase mask or the like for the core 12 c in the one end portion 12 a of the loop optical fiber 12, and is typically caused by light-induced refractive index change due to ultraviolet irradiation. Is formed by forming a periodic refractive index change of about 10,000 to 20,000 layers in one or more groups in the propagation direction in the one end portion 12a of the loop optical fiber 12. The refractive index change may have an equal period, but it may be one in which the period is sequentially changed in a chirp shape. The optical fiber grating 32 has a characteristic of selectively reflecting light having a wavelength corresponding to the period of the refractive index and the effective refractive index, and transmits light having a wavelength λ1 centered at 1551 nm, for example. It functions as a wavelength selective filter that reflects light (ambient light) having a wavelength of at least 3 nm or more different from λ1 and having a bandwidth of, for example, about 6.5 nm. FIG. 8 shows the spectrum of the amplified input light (clockwise light Lcw and counterclockwise light Lccw) that is selectively passed by the optical fiber grating section 32. FIG. 9 shows the optical fiber grating section. The spectrum of ambient light that is selectively reflected by 32 is shown.

  FIG. 9 shows ambient light including the wavelength bands on both sides of the wavelength λ1, but the reflection characteristic of the optical fiber grating 32 is a part of the ambient light, for example, with respect to the wavelength λ1. It is also possible to reflect a wavelength band on one side or a part thereof.

  As described above, according to the optical fiber gyroscope 10 of the present embodiment, when the optical signal amplifying device 14 receives (b-1) the clockwise light Lcw and the counterclockwise light Lccw, the clockwise light Lcw is inputted. And the counterclockwise light Lccw are amplified and output, respectively, and the clockwise light Lcw and the counterclockwise light Lccw of the wavelength λ1 are inverted with respect to the intensity of the clockwise light Lcw and the counterclockwise light Lccw. A semiconductor optical amplifier 30 that emits ambient light other than light; and (b-2) all of ambient light other than light of wavelength λ1 that is clockwise light Lcw and counterclockwise light Lccw emitted from the semiconductor optical amplifier 30. Or a wavelength-selective reflecting element (optical fiber grating portion 32) that partially reflects and enters the semiconductor optical amplifier 30, and surroundings other than light of wavelength λ1 that is clockwise light Lcw and counterclockwise light Lccw light Is reflected by the optical fiber grating section 32 and is input again to the semiconductor optical amplifier 30, so that the ambient light indicating the intensity inversion is fed back, so that the gain of the semiconductor optical amplifier 30 depends on the input light. Since the negative feedback light amplification effect is obtained by modulation, the waveform distortion and noise of the clockwise light Lcw and the counterclockwise light Lccw are reduced. As a result, the degree of modulation of the clockwise light Lcw and the counterclockwise light Lccw is increased, so that the peak P of the beat signal SB generated by the frequency difference Δf is also sharply obtained and obtained from the analysis of the beat signal SB. The accuracy of the beat frequency fb and the rotational angular velocity ω obtained from the beat frequency fb can be sufficiently obtained.

  Further, according to the optical fiber gyroscope 10 of the present embodiment, one of the one end 12a and the other end 12b of the loop optical fiber 12 optically coupled to the semiconductor optical amplifier 30 (one end) Part 12a) of the light emitted from the semiconductor optical amplifier 30 and reflects all or part of the ambient light other than the light of wavelength λ1 which is the clockwise light Lcw and the counterclockwise light Lccw, and the semiconductor light Since the optical fiber grating portion 32 that enters the amplifier 30 is used, the optical coupling structure between the semiconductor optical amplifier 30 and the one end portion 12a of the loop optical fiber 12 becomes simple and small.

  Further, according to the optical fiber gyroscope 10 of the present embodiment, the front spherical lens R is provided on the end surface of the one end portion 12 a where the optical fiber grating portion 32 of the loop optical fiber 12 is provided, and the output from the semiconductor optical amplifier 30. Since light is directly incident on the tip lens R, the optical coupling structure between the semiconductor optical amplifier 30 and the one end portion 12a of the loop optical fiber 12 becomes simpler and smaller.

  Further, according to the optical fiber gyro 10 of the present embodiment, the semiconductor optical amplifier 30 includes the active layer 30c formed of a pn junction, and the active layer 30c is a bulk, a quantum well, a strained superlattice, or a quantum Since it is composed of dots, the optical signal amplifying device can be further miniaturized and made into one chip. Especially when the active layer is composed of quantum wells and quantum dots, it is of the order of 10 GHz. Since the signal can be amplified in the high frequency region and the frequencies of the clockwise light Lcw and the counterclockwise light Lccw are increased, the accuracy of the rotational angular velocity ω obtained from the beat frequency fb is further improved.

  Further, according to the optical fiber gyroscope 10 of the present embodiment, a part of the clockwise light Lcw and a part of the counterclockwise light Lccw that are provided in the loop-shaped optical fiber 12 and propagate in the loop-shaped optical fiber 12 are used. A bidirectional light extraction optical coupler 16 to be extracted, and a part of the clockwise light Lcw and a part of the counterclockwise light Lccw extracted from the loop optical fiber 12 by the bidirectional light extraction coupler 16 are mutually connected. An optical multiplexer 20 that combines and outputs beat light Lb caused by a frequency difference Δf generated between the clockwise light Lcw and the counterclockwise light Lccw, and beat light combined by the optical multiplexer 20 The photodetector 22 that converts Lb into a beat signal SB that is an electrical signal, and the frequency fp of the peak point P of the beat signal SB included in the beat signal SB converted by the photodetector 22 are analyzed. Rotational angular velocity calculation for calculating the rotational angular velocity ω of the loop optical fiber 12 based on the frequency fp of the beat signal SB analyzed by the frequency analyzing unit 24 and the beat signal SB analyzed by the frequency analyzing unit 24 from the previously stored relationship shown in FIG. Since the portion 26 is included, the optical fiber gyroscope 10 having a simple structure and capable of detecting the rotational angular velocity with high accuracy can be obtained.

  Next, another embodiment of the present invention will be described. In the following description, parts common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

  In the optical fiber gyroscope 10 of the embodiment shown in FIG. 10, an optical signal amplifier 40 to which a three-terminal optical signal amplifier is applied is used in place of the optical signal amplifier 14 of the above-described embodiment. This point is similarly configured. The optical signal amplifying apparatus 40 will be described below.

  When the clockwise light Lcw is input to one end face 42g, the optical signal amplifying device 40 amplifies the clockwise light Lcw and outputs the amplified light from the other end face 42h, and against the intensity of the clockwise light Lcw. A first semiconductor optical amplifier 42 that bi-directionally emits first ambient light other than the wavelength λ1 of the clockwise light whose intensity is inverted is provided at one end 12a of the loop optical fiber 12, and allows light of wavelength λ1 to pass therethrough. The first ambient light emitted from the first semiconductor optical amplifier 42 to the one end face 42g side is reflected or re-input to the first semiconductor optical amplifier 42 to generate a negative feedback light amplification function. When one optical fiber grating section (first wavelength selective reflection element) 44 and counterclockwise light Lccw are input to one end face 46g, the counterclockwise light Lccw is amplified and output from the other end face 46h. As well as A second semiconductor optical amplifier 46 that radiates second ambient light other than the wavelength λ1 of the counterclockwise light Lccw inverted in intensity with respect to the intensity of the counterclockwise light Lccw, and the other end of the loop optical fiber 12 The second semiconductor optical amplifier is provided in the portion 12b and transmits light of wavelength λ1, but reflects all or part of the second ambient light emitted from the second semiconductor optical amplifier 46 toward the one end face 46g. A second optical fiber grating section (second wavelength selective reflection element) 48 that re-inputs to 46 and generates a negative feedback light amplification function. The first semiconductor optical amplifier 42 and the second semiconductor optical amplifier 46 are configured in the same manner as the semiconductor optical amplifier 30 described above. The first optical fiber grating portion 44 and the second optical fiber grating portion 48 are configured in the same manner as the optical fiber grating portion 32 described above. Further, the one end portion 12a and the other end portion 12b of the loop optical fiber 12 are provided with a tip lens R on the end face thereof as in the above-described embodiment, and the one end face 42g side of the first semiconductor optical amplifier 42 is provided. And optically coupled directly to one end face 46g side of the second semiconductor optical amplifier 46.

  Further, the optical signal amplifying device 40 is inserted into the loop-shaped optical fiber 12 and propagates in the loop-shaped optical fiber 12. An optical coupler 50 for extracting 10% of light and a leading ball lens R are provided, respectively, and optically directly coupled to the other end face 42 h side of the first semiconductor optical amplifier 42 and the other end face 46 h side of the second semiconductor optical amplifier 46. A pair of first branch fiber portion 52 and second branch fiber portion 54, and a common fiber portion 56 in which the first branch fiber 52 and the second branch fiber 54 are melt-drawn and coupled to the optical coupler 50. Provided in the Y-shaped fiber 58 and its common fiber portion 56 and allows light of wavelength λ1 to pass through, but all or one of the first ambient light emitted from the first semiconductor optical amplifier 42. And a third optical fiber grating 60 to be incident to the output side of second semiconductor optical amplifier 46 to reflect comprises.

  According to the optical fiber gyro 10 having the optical signal amplifying apparatus 40 configured as described above, the clockwise light Lcw and the counterclockwise light Lccw that circulate around the loop optical fiber 12 are negatively fed back by re-input of the ambient light. Since the first semiconductor optical amplifier 42 and the second semiconductor optical amplifier 46 having an amplifying action are bi-directionally amplifying and are steadily propagated with a relatively high intensity, they are loop-like as in the above-described embodiment. The rotational angular velocity ω of the optical fiber 12 is detected.

  At this time, in the optical signal amplifying apparatus 40, the clockwise light Lcw passes through the first semiconductor optical amplifier 42 from the end 12a of the loop optical fiber 12, and the first optical fiber grating portion 44 and the third optical fiber. After negative feedback amplification due to re-input of ambient light from the grating unit 60, the light is returned to the loop optical fiber 12 through the first branch fiber 52, the common fiber unit 56, and the optical coupler 50. At the same time, a part of the counterclockwise light Lccw taken out from the optical coupler 50 enters the second semiconductor optical amplifier 46 from the second branch fiber portion 54 and passes through the second semiconductor optical amplifier 46 in the second process. After negative feedback amplification due to re-input of ambient light from the optical fiber grating unit 46 and the third optical fiber grating unit 60, the clockwise light Lcw is transmitted from the second semiconductor optical amplifier 46 to the end 12b of the loop optical fiber 12. Returned.

  In the optical signal amplifying apparatus 40, the other part of the counterclockwise light Lccw extracted from the optical coupler 50 is subjected to negative feedback amplification in the first semiconductor optical amplifier 42 via the first branch fiber 52, It is returned to the end 12a of the loop optical fiber 12. Further, the counterclockwise light Lccw that has passed through the optical coupler 50 and reached the end 12b of the loop optical fiber 12 undergoes negative feedback amplification in the process of passing through the second semiconductor optical amplifier 46, and then the second branch. After passing through the fiber 54 and the common fiber portion 56 and the optical coupler 50, the light is returned to the loop optical fiber 12 as clockwise light Lcw. As a result of such an action, the characteristics shown in FIG. 11 are obtained.

  According to the optical fiber gyroscope 10 of the present embodiment, all or part of the ambient light other than the wavelength λ1 of the clockwise light Lcw and the counterclockwise light Lccw is made to be the first optical fiber grating portion 44 (first wavelength selective reflection element). ) And the second optical fiber grating section 48 (second wavelength selective reflection element) and input again to the first semiconductor optical amplifier 42 and the second semiconductor optical amplifier 46, so that a small three-terminal optical signal is obtained. In addition to obtaining an amplifying device, the gain of the semiconductor optical amplifiers 42 and 46 is modulated according to the input optical signal by feeding back the ambient light indicating the intensity inversion, so that a negative feedback optical amplification effect can be obtained. Waveform distortion of the light Lcw and the counterclockwise light Lccw is reduced. Thereby, the noise of the clockwise light Lcw and the counterclockwise light Lccw is reduced and the degree of modulation is increased, so that the peak of the beat signal SB generated by the frequency difference Δf is also sharply obtained, and the beat signal SB The accuracy of the beat frequency fb obtained from this analysis and the rotational angular velocity ω obtained from the beat frequency fb can be sufficiently obtained.

  Further, according to the optical fiber gyroscope 10 of the present embodiment, the first wavelength selective reflection element is provided at the one end portion 12a of the loop optical fiber 12 optically coupled to the first semiconductor optical amplifier 42. A first optical fiber grating unit 44 that reflects all or part of the first ambient light emitted from the first semiconductor optical amplifier 42 and makes it incident on the first semiconductor optical amplifier 42; And provided at the other end of the loop optical fiber 12 optically coupled to the second semiconductor optical amplifier 46, and reflects all or part of the second ambient light emitted from the second semiconductor optical amplifier 46. Since the second optical fiber grating portion 48 that enters the second semiconductor optical amplifier 46 is used, the first semiconductor optical amplifier 42 and the second semiconductor optical amplifier 46 are connected to the loop. Optical coupling structure between the two ends 12a and 12b of the optical fiber 12 becomes simple and compact.

  Further, according to the optical fiber gyroscope 10 of the present embodiment, the front lens is provided on the end faces of both end portions 12a and 12b provided with the first optical fiber grating portion 44 and the second optical fiber grating portion 48 of the loop optical fiber 12. R is provided, and the output light from the first semiconductor optical amplifier 42 and the second semiconductor optical amplifier 46 is directly incident on the front lens R, so that the first semiconductor optical amplifier 42 and the second semiconductor optical amplifier The optical coupling structure between the two end portions 12a and 12b provided with the first optical fiber grating portion 44 and the second optical fiber grating portion 48 of the loop optical fiber 12 becomes simpler and smaller.

  Further, according to the optical fiber gyroscope 10 of the present embodiment, the first branch fiber portion 52 and the second branch fiber portion 54 that are optically coupled to the output sides of the first semiconductor optical amplifier 42 and the second semiconductor optical amplifier 46, and The first branch fiber 52 and the second branch fiber 54 include a Y-shaped fiber 58 having a common fiber portion 56 that is melt-drawn and coupled to the optical coupler 50, and serves as a third wavelength-selective reflection element. A third optical fiber grating that is provided in the common fiber portion 56 and reflects all or a part of the first ambient light emitted from the first semiconductor optical amplifier 42 to enter the output side of the second semiconductor optical amplifier 46. Since the unit 60 is used, a small three-terminal optical signal amplifying device can be applied to the optical fiber gyro 10.

  As mentioned above, although one Example of this invention was described based on drawing, this invention is applied also in another aspect.

  For example, in the embodiment shown in FIG. 5 described above, the optical fiber grating section 32 is configured separately from the semiconductor optical amplifier 30. However, when the optical fiber grating section 32 is configured in the optical waveguide 30b of the semiconductor optical amplifier 30, The amplifier 30 may be integrated with the amplifier 30.

  In the embodiment shown in FIG. 5 described above, the optical fiber grating portion 32 functioning as a wavelength selective reflection element is provided at the end portion 12a of the loop optical fiber 12. Instead, the wavelength selective reflection is performed. A wavelength selective mirror that functions as an element may be provided between the end 12 a of the loop optical fiber 12 and the semiconductor optical amplifier 30. In this case, for example, between the end portion 12a of the loop optical fiber 12 and the semiconductor optical amplifier 30 is optically connected through a pair of convex lenses and a wavelength selective mirror interposed between the pair of convex lenses. Combined.

  Further, in the embodiment of FIG. 5 described above, the optical fiber grating portion 32 functioning as a wavelength selective reflecting element is provided at the end portion 12a of the loop optical fiber 12, but the optical fiber grating portion 32 is made of a semiconductor. You may provide in the edge part 12b of the loop-shaped optical fiber 12 located in the opposite side with respect to the optical amplifier 30. FIG. Moreover, the optical fiber grating part which functions as a wavelength selective reflection element may be provided in both the end part 12a and the end part 12b of the loop-shaped optical fiber 12.

  Although not illustrated one by one, the present invention can be implemented in variously modified and improved modes based on the knowledge of those skilled in the art.

1 is a schematic diagram illustrating a basic configuration of an optical fiber gyro to which an optical signal amplification device according to an embodiment of the present invention is applied. It is a figure explaining the structure of the optical coupler for bidirectional | two-way light extraction used for the optical fiber gyro of FIG. It is a figure which shows an example of the relationship memorize | stored previously used by the rotational angular velocity calculation part of FIG. It is a figure which shows the relationship between the beat signal which generate | occur | produces in the optical fiber gyro of FIG. 1, and the rotation angular velocity of the loop-shaped optical fiber provided in the optical fiber gyro. FIG. 2 is a schematic diagram for explaining a main configuration of the optical signal amplifying apparatus of FIG. 1. FIG. FIG. 6 is a perspective view showing an example of a semiconductor optical amplifier provided in the optical signal amplifying device of FIG. 5. It is a figure explaining the structure of the optical fiber grating part with which the optical signal amplification apparatus of FIG. 5 is equipped. It is a figure which shows the transmission characteristic of the optical fiber grating part of FIG. It is a figure which shows the reflective characteristic of the optical fiber grating part of FIG. It is a figure explaining the structure of the optical signal amplifier of the other Example of this invention. It is a figure explaining the characteristic of the optical signal amplifier in the Example of FIG.

Explanation of symbols

10: Optical fiber gyroscope 14, 40: Optical signal amplifier 12: Loop optical fiber (wavelength selective reflection element)
16: Optical coupler (Optical coupler for bidirectional light extraction)
26: Rotational angular velocity calculation unit 30: Semiconductor optical amplifier 32: Optical fiber grating unit 42: First semiconductor optical amplifier 44: First optical fiber grating unit (first wavelength selective reflection element)
46: Second semiconductor optical amplifier 48: Second optical fiber grating section (second wavelength selective reflection element)
50: Optical coupler R: Tip ball lens

Claims (11)

A loop-shaped optical fiber, a clockwise light propagating clockwise in the loop-shaped optical fiber inserted in a state optically coupled to a predetermined position of the loop-shaped optical fiber, and a counter-current propagating counterclockwise An optical signal amplifying device for amplifying each clockwise light, and rotating the loop optical fiber based on a frequency difference generated between the clockwise light and the counterclockwise light propagating in the loop optical fiber. An optical fiber gyro that detects angular velocity,
The optical signal amplifier is
When the clockwise light and the counterclockwise light are input, the clockwise light and the counterclockwise light are respectively amplified and output, and the intensity is inverted with respect to the intensity of the clockwise light and the counterclockwise light. A semiconductor optical amplifier that emits ambient light other than the wavelengths of clockwise and counterclockwise light; and
A wavelength-selective reflecting element that reflects all or part of ambient light other than the wavelengths of the clockwise light and counterclockwise light emitted from the semiconductor optical amplifier and enters the semiconductor optical amplifier. Features an optical fiber gyro.   The wavelength selective reflection element is provided on at least one of one end and the other end of the loop optical fiber optically coupled to the semiconductor optical amplifier, and the light is emitted from the semiconductor optical amplifier. 2. An optical fiber gyroscope according to claim 1, wherein the optical fiber gyroscope is an optical fiber grating portion that reflects all or a part of ambient light other than the wavelengths of clockwise light and counterclockwise light and enters the semiconductor optical amplifier.   A tip ball lens is provided on an end surface of the end portion of the loop optical fiber where the optical fiber grating portion is provided, and output light from the semiconductor optical amplifier is directly incident on the tip ball lens. The optical fiber gyro according to claim 2.   The semiconductor optical amplifier is a semiconductor optical amplifier having an active layer composed of a pn junction, and the active layer is composed of a bulk, a quantum well, a strained superlattice, or a quantum dot. Any one of the optical fiber gyros. A bidirectional optical extraction optical coupler that is provided in the loop-shaped optical fiber and extracts a part of the clockwise light and a part of the counterclockwise light propagating through the loop-shaped optical fiber;
A part of the clockwise light and a part of the counterclockwise light extracted from the loop-shaped optical fiber by the bidirectional light extraction coupler are combined with each other, and between the clockwise light and the counterclockwise light. An optical multiplexing element that outputs beat light caused by the generated frequency difference;
A combined light detector that converts beat light combined by the optical combining element into an electrical signal;
A frequency analysis unit that analyzes the frequency of the beat signal included in the electrical signal converted by the combined photodetector;
5. A rotation angular velocity calculation unit that calculates a rotation angular velocity of the loop optical fiber based on a frequency of a beat signal analyzed by the frequency analysis unit from a previously stored relationship. Any one of the optical fiber gyros. A loop-shaped optical fiber, a clockwise light propagating clockwise in the loop-shaped optical fiber inserted in a state optically coupled to a predetermined position of the loop-shaped optical fiber, and a counter-current propagating counterclockwise An optical signal amplifying device for amplifying each clockwise light, and rotating the loop optical fiber based on a frequency difference generated between the clockwise light and the counterclockwise light propagating in the loop optical fiber. An optical fiber gyro that detects angular velocity,
The optical signal amplifier is
When the clockwise light is input, the clockwise light is amplified and output, and first ambient light other than the wavelength of the clockwise light whose intensity is inverted with respect to the intensity of the clockwise light is emitted. 1 semiconductor optical amplifier;
A first wavelength-selective reflecting element that reflects all or part of the first ambient light emitted from the first semiconductor optical amplifier to the input side and enters the first semiconductor optical amplifier; and the counterclockwise light A second semiconductor that, when input, amplifies and outputs the counterclockwise light and emits second ambient light other than the wavelength of the counterclockwise light whose intensity is inverted with respect to the intensity of the counterclockwise light An optical amplifier;
A second wavelength-selective reflecting element that reflects all or part of the second ambient light radiated from the second semiconductor optical amplifier to the input side and enters the second semiconductor optical amplifier; and the first semiconductor optical amplifier A third wavelength-selective reflecting element that reflects all or part of the first ambient light radiated from the light source to the output side and enters the output side of the second semiconductor optical amplifier;
A part of the counterclockwise light in the loop optical fiber is taken out and made incident on the output side of the second semiconductor optical amplifier, and the output light of the first semiconductor optical amplifier and the second semiconductor optical amplifier is looped. An optical fiber gyro, comprising: an optical coupler that enters the optical fiber as clockwise light. The first wavelength selective reflection element is provided at one of one end and the other end of the loop optical fiber optically coupled to the first semiconductor optical amplifier, and is radiated from the first semiconductor optical amplifier. A first optical fiber grating part that reflects all or part of the first ambient light to be incident on the first semiconductor optical amplifier,
The second wavelength selective reflection element is provided on the other end of the looped optical fiber optically coupled to the second semiconductor optical amplifier, and is emitted from the second semiconductor optical amplifier. 7. The optical fiber gyro according to claim 6, wherein the optical fiber gyro is a second optical fiber grating part that reflects all or part of the second ambient light to be incident on the second semiconductor optical amplifier.   From the first semiconductor optical amplifier and the second semiconductor optical amplifier, front end lenses are respectively provided on end faces of both ends of the loop optical fiber where the first optical fiber grating portion and the second optical fiber grating portion are provided. 8. The optical fiber gyro according to claim 7, wherein the output light is directly incident on the tip lens. A first branch fiber portion and a second branch fiber portion optically coupled to an output side of the first semiconductor optical amplifier and the second semiconductor optical amplifier, and the first branch fiber and the second branch fiber are melt-drawn and the A Y-shaped fiber with a common fiber portion coupled to an optical coupler;
The third wavelength selective reflection element is provided in the common fiber portion and reflects all or a part of the first ambient light emitted from the first semiconductor optical amplifier to output the second semiconductor optical amplifier. The optical fiber gyroscope according to any one of claims 6 to 8, wherein the optical fiber gyroscope is a third optical fiber grating portion to be incident on the optical fiber.   The first semiconductor optical amplifier and the second semiconductor optical amplifier are semiconductor optical amplifiers having an active layer composed of a pn junction, and the active layer is composed of a bulk, a quantum well, a strained superlattice, or a quantum dot The optical fiber gyro according to any one of claims 6 to 9. A bidirectional optical extraction optical coupler that is provided in the loop-shaped optical fiber and extracts a part of the clockwise light and a part of the counterclockwise light propagating through the loop-shaped optical fiber;
A part of the clockwise light and a part of the counterclockwise light extracted from the loop-shaped optical fiber by the bidirectional light extraction coupler are combined with each other, and between the clockwise light and the counterclockwise light. An optical multiplexing element that outputs beat light caused by the generated frequency difference;
A combined light detector that converts beat light combined by the optical combining element into an electrical signal;
A frequency analysis unit that analyzes the frequency of the beat signal included in the electrical signal converted by the combined photodetector;
A rotational angular velocity calculation unit for calculating a rotational angular velocity of the loop optical fiber based on the frequency of the beat signal analyzed by the frequency analysis unit from a previously stored relationship;
The optical fiber gyro according to any one of claims 6 to 10, further comprising:

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