JP2008102057A - Optical gyroscope and gyro system using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical gyroscope detecting a rotation speed even when laser light propagating clockwise and laser light propagating counterclockwise are not overlapped. <P>SOLUTION: A semiconductor optical amplifier 1 oscillates pieces of laser light CW, CCW, amplifies the pieces of the laser light CW, CCW by induction discharge, and radiates the pieces of the laser light CW, CCW into an optical fiber 2 from end faces 1A, 1B respectively. A coupler 3 branches the laser light CW of the optical fiber 2 into the optical fiber 4 at a rate of 99%:1%. An optical detector 5 detects light intensity of the laser light CW of the optical fiber 4 and outputs the detected light intensity to a spectral analyzer 6. The spectral analyzer 6 detects a change frequency of the light intensity corresponding to the frequency of a beat signal obtained by square-detecting overlapped light of the pieces of the laser light CW, CCW and outputs the detected change frequency to a detector 7. The detector 7 detects a rotational angle speed corresponding to the change frequency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical gyro capable of detecting the rotational angular velocity of a rotating body and a gyro system using the same.

  The gyro is a sensor that can measure rotation with respect to inertial space, and is a sensor that can measure absolute rotation. As such gyros, there are mechanical gyros and optical gyros.

  The mechanical gyro is a gyro that uses the property that the rotating shaft of the rotating body always keeps a fixed direction with respect to the inertial space. However, mechanical gyroscopes require maintenance, are expensive, and are weak in vibration and acceleration, so that their application range is limited to aircraft, ships, rockets, artificial satellites, and the like.

  On the other hand, an optical gyro using the Sagnac effect has recently been put into practical use. This optical gyro propagates clockwise light and counterclockwise light in the optical path, and generates two light (clockwise light and counterclockwise light) caused by the rotation of the rotating body. This is a gyro using the fact that the frequency difference is proportional to the rotational angular velocity.

Optical gyros are roughly classified into optical fiber gyros and ring laser gyros, and there are three types of optical fiber gyros: interference optical fiber gyros, resonant optical fiber gyros, and Brillouin optical fiber gyros (Non-Patent Document 1). ).
Kazuo Hotate, “Practical application of optical fiber gyro and development of next generation technology”, Laser Research, Vol. 26, No. 4, April 1998, p297-303. LN Menegozzi and WE Lamb, Jr. Phys. Rev. A, 8, 2103, (1971). E. Landau and E. Lifshits, The Classical Theory of Fields, 2nd ed. (Addison-Wesley, Reading, Mass., 1962) P. Mester, M.M. Sargent III, “Basics of Quantum Optics”, Springer Fairlark Tokyo Ltd. (1995).

  However, the conventional optical gyro has a problem that the rotational speed cannot be detected unless the superposition light of the laser light propagating clockwise in the optical fiber and the laser light propagating counterclockwise is detected. .

  Therefore, the present invention has been made to solve such a problem, and its purpose is to detect the rotational speed without superimposing the laser light propagating clockwise and the laser light propagating counterclockwise. It is to provide a possible optical gyro.

  Another object of the present invention is to provide a gyro system including an optical gyro capable of detecting a rotational speed without superimposing a laser beam propagating clockwise and a laser beam propagating counterclockwise. It is.

    According to the present invention, the optical gyro includes a ring laser and detection means. The ring laser oscillates the first and second laser beams, amplifies the oscillated first and second laser beams, rotates the first laser beam clockwise, and generates the second laser beam. Rotate counterclockwise. The detecting means is a ring laser based on a change frequency of the light intensity of one of the first and second laser beams propagating through the ring laser when the ring laser rotates in a predetermined plane. Detects the rotational angular velocity of.

  Preferably, the ring laser includes a semiconductor optical amplifier and a waveguide. The semiconductor optical amplifier has a first end face and a second end face opposite to the first end face, and oscillates the first and second laser beams to cause the first and second end faces to oscillate from the first and second end faces, respectively. The second laser beam is emitted. The waveguide propagates the first and second laser beams emitted from the semiconductor optical amplifier. The waveguide rotates the first laser light emitted from the first end face clockwise to guide it to the semiconductor optical amplifier from the second end face, and also emits the second laser emitted from the second end face. The light is rotated counterclockwise and guided from the first end face to the semiconductor optical amplifier.

  Preferably, the waveguide is made of an optical fiber.

  Preferably, the waveguide includes first and second optical fibers and a coupler. The first optical fiber rotates the first laser beam clockwise, and rotates the second laser beam counterclockwise. The coupler guides a part of one of the first and second laser lights in the first optical fiber to the second optical fiber. And a detection means detects the rotation angular velocity of a ring laser based on the change frequency of the light intensity of any one laser beam in a 2nd optical fiber.

  According to the present invention, the optical gyro includes an activation region, a passive region, and a detection means. The activated region oscillates the first and second laser beams and amplifies the oscillated first and second laser beams. The passive region rotates the first laser light clockwise and the second laser light counterclockwise. The detection means is configured to emit either one of the first and second laser beams emitted from the activation region into the passive region when the activation region and the passive region rotate within a predetermined plane. The rotational angular velocities of the active region and the passive region are detected based on the intensity change frequency.

  Preferably, the activation region is composed of a semiconductor optical amplifier, and the passive region is composed of a semiconductor waveguide connected to both ends of the semiconductor optical amplifier.

  Preferably, the active region and the passive region are formed on the same semiconductor substrate.

  Furthermore, according to the present invention, the gyro system includes an optical gyro, a transmission device, and a reception device. The optical gyro is the optical gyro according to any one of claims 1 to 7. The transmission device converts the rotational angular velocity detected by the detection means into a radio signal and transmits it. The receiving device receives the radio signal transmitted from the transmitting device, decodes the received radio signal, and acquires the rotational angular velocity.

  In the optical gyro according to the present invention, the first and second laser beams before the first laser beam propagated clockwise by the laser light source and the second laser beam propagated counterclockwise are superimposed. The light intensity of either of these changes depending on the frequency of the beat signal when the first laser beam and the second laser beam are superimposed. Then, if the frequency at which the light intensity of one of the first and second laser beams changes is detected, the frequency of the beat signal is detected. A proportional relationship is established between the change frequency of the light intensity of one of the first and second laser beams and the rotational angular velocity. As a result, when the change frequency of the light intensity of one of the first and second laser lights is detected, the rotational angular velocity corresponding to the detected change frequency is detected.

  Therefore, according to the present invention, the rotational speed can be detected without overlapping the laser light propagating clockwise and the laser light propagating counterclockwise.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a schematic diagram showing a configuration of an optical gyro according to Embodiment 1 of the present invention. Referring to FIG. 1, an optical gyro 10 according to Embodiment 1 of the present invention includes a semiconductor optical amplifier (SOA) 1, optical fibers 2 and 4, a coupler 3, a photodetector 5, and a semiconductor optical amplifier (SOA). The spectrum analyzer 6 and the detector 7 are provided.

  The semiconductor optical amplifier 1 has an active layer made of indium gallium arsenide (InGaAs). The semiconductor optical amplifier 1 oscillates laser light having a wavelength of 1579 nm, for example, and emits the oscillated laser light from the end faces 1A and 1B as clockwise laser light CW and counterclockwise laser light CCW, respectively. The light is emitted into the fiber 2. Further, the semiconductor optical amplifier 1 amplifies the laser beams CW and CCW that have made one round in the optical fiber 2 by stimulated emission, and emits the amplified laser beams CW and CCW to the optical fiber 2 from the end faces 1A and 1B, respectively.

  The optical fiber 2 is connected to both ends of the semiconductor optical amplifier 1 in a loop shape, and has a length of 3.019 m and a refractive index (core refractive index) of 1.448, for example. Then, the optical fiber 2 rotates the laser light CW emitted from the end face 1A of the semiconductor optical amplifier 1 clockwise, guides the rotated laser light CW from the end face 1B into the semiconductor optical amplifier 1, and transmits the semiconductor light. The laser light CCW emitted from the end face 1B of the amplifier 1 is rotated counterclockwise, and the rotated laser light CCW is guided from the end face 1A into the semiconductor optical amplifier 1.

  The coupler 3 couples the optical fiber 2 with the optical fiber 4 so that the laser light CW propagating through the optical fiber 2 is 99% and the laser light CW propagating through the optical fiber 4 is 1%.

  The optical fiber 4 is coupled to the optical fiber 2 by the coupler 3, and guides a part (1%) of the laser light CW propagating through the optical fiber 2 to the photodetector 5.

  The photodetector 5 detects the light intensity of the laser light CW propagating through the optical fiber 4 and outputs the detected light intensity to the spectrum analyzer 6.

  The spectrum analyzer 6 detects the frequency Δν at which the light intensity detected by the photodetector 5 changes, and outputs the detected frequency Δν to the detector 7.

  The detector 7 receives the frequency Δν from the spectrum analyzer 6 and detects the rotational angular velocity of the rotating body based on the received frequency Δν by a method described later.

  The semiconductor optical amplifier 1 can oscillate and amplify the laser light CW that rotates clockwise and the laser light CCW that rotates counterclockwise by connecting the optical fiber 2 to both ends. 1 and the optical fiber 2 constitute a ring resonator type ring laser. That is, the ring laser comprising the semiconductor optical amplifier 1 and the optical fiber 2 is a laser comprising an activation region (semiconductor optical amplifier 1) and a passive region (optical fiber 2).

  When an experiment for examining the relationship between the frequency Δν and the rotational angular velocity in the optical gyro 10 is performed, the optical gyro 10 is placed on the table 20. The table 20 is rotated clockwise or counterclockwise by the servo mechanism 30 at various rotational angular velocities. The controller 40 controls the servo mechanism 30 to rotate the table 20 clockwise or counterclockwise at various rotational angular velocities.

  FIG. 2 is a plan view of the semiconductor optical amplifier 1 shown in FIG. Referring to FIG. 2, the semiconductor optical amplifier 1 includes an active layer 11, optical confinement layers 12 and 13, and antireflection films 14 and 15. The active layer 11 is sandwiched between the light confinement layers 12 and 13 and is in contact with the end faces 1A and 1B obliquely.

  The optical confinement layers 12 and 13 are formed of a barrier layer, a cladding layer, and the like, and are provided on both sides of the active layer 11 in contact with the active layer 11. The antireflection films 14 and 15 are formed in contact with the end faces 1A and 1B, respectively.

  As shown in FIG. 2, the structure in which the active layer 11 is disposed obliquely with respect to the end faces 1A and 1B forms a stacked body in which the active layer 11, the optical confinement layers 12 and 13 and the like are stacked, and is formed. The laminate is manufactured by cutting so that the active layer 11 is disposed obliquely.

  When a current is injected into the active layer 11 to cause laser oscillation, the laser light is confined by the light confinement layers 12 and 13 and propagates in the active layer 11 in the direction of the end faces 1A and 1B. The laser beam is emitted from the end surface 1A as the laser beam CW and is emitted from the end surface 1B as the laser beam CCW.

  The laser light CW goes around the optical fiber 2 clockwise and is introduced into the active layer 11 from the end face 1B through the antireflection film 15. The laser beam CW introduced into the active layer 11 is amplified by stimulated emission and is emitted from the end face 1A again.

  Further, the laser CCW goes around the optical fiber 2 counterclockwise and is introduced into the active layer 11 from the end face 1A via the antireflection film 14. The laser light CCW introduced into the active layer 11 is amplified by stimulated emission and is emitted from the end face 1B again.

  Thus, the semiconductor optical amplifier 1 oscillates and emits the laser beams CW and CCW into the optical fiber 2, amplifies the laser beams CW and CCW propagated in the optical fiber 2 by stimulated emission, and again, The light is emitted into the optical fiber 2.

Therefore, the laser beams CW and CCW need to pass through the end faces 1A and 1B many times. In order to maintain the intensity of the laser beams CW and CCW, the reflectance of the laser beams CW and CCW at the end faces 1A and 1B is It is set to 10 ⁻⁵ or less. Further, since it is necessary to prevent multiple reflections in the semiconductor optical amplifier 1, the reflectances of the laser beams CW and CCW at the end faces 1A and 1B are set to 10 ⁻⁵ or less.

  Thus, in order to keep the reflectance at the end faces 1A and 1B low, the active layer 11 is disposed obliquely with respect to the end faces 1A and 1B, and the antireflection films 14 and 15 are formed on the end faces 1A and 1B.

  The optical fiber 2 is connected to the antireflection films 14 and 15 of the semiconductor optical amplifier 1 so that the laser beams CW and CCW from the active layer 11 enter the core.

  FIG. 3 is a schematic diagram showing the configuration of the coupler 3 shown in FIG. Referring to FIG. 3, the coupler 3 includes guides 31 and 32. The guides 31 and 32 couple the two optical fibers by sandwiching the two optical fibers in contact with each other.

  When the optical fiber 4 is coupled to the optical fiber 2, the optical fiber 4 is disposed between the guides 31 and 32 so as to contact the optical fiber 2. In this case, the core 21 of the optical fiber 2 is disposed close to the core 41 of the optical fiber 4. Note that one end of the optical fiber 4 is terminated by a terminator 42.

  1% of the laser light CW propagating clockwise in the optical fiber 2 leaks from the core 21 to the core 41 in the vicinity of the core 21 and the core 41. Then, 1% of the laser light CW leaked to the core 41 propagates through the optical fiber 4.

  Thus, the laser beam CW propagating in the optical fiber 4 is a part (1%) of the laser beam CW propagating in the optical fiber 2.

  In the optical gyro 10, the rotational angular velocity is detected by detecting the frequency Δν at which the light intensity of the laser light CW changes without superimposing the laser light CW and the laser light CCW. That is, the optical gyro 10 detects the rotational angular velocity by detecting the frequency of the Sagnac beat signal without using a multiplexing element that combines the laser light CW and the laser light CCW.

  Therefore, a method for detecting the frequency Δν of the Sagnac beat signal without using a multiplexing element that combines the laser beam CW and the laser beam CCW will be described.

  In this method, the frequency Δν of the Sagnac beat signal is observed from the vibration frequency of the light intensity of one-way rotation by utilizing the effect of semiconductor mutual gain saturation (four-wave mixing).

  The principle that the light intensity oscillates at the frequency Δν of the Sagnac beat signal can be explained by the Maxwell-Bloch equation that is often used in the field of laser physics. Here, it is assumed only that the ring laser is composed of a passive waveguide and an active waveguide. For example, in the optical gyro 10, the passive waveguide is the optical fiber 2, and the active waveguide is the semiconductor optical amplifier 1.

  The laser beam in the link laser rotating at the rotation angular velocity Ω can be described by the Maxwell-Bloch equation derived in the rotating coordinate system. The Maxwell-Bloch equation is well known as a general equation describing the state of laser light (Non-Patent Documents 2 to 4).

  By assuming that light is confined in one dimension by an optical fiber and a semiconductor optical amplifier, the following Maxwell-Bloch equation is obtained.

  Here, s is a coordinate system along the ring waveguide, and n (s), R, and Ω are the refractive index, radius, and rotational angular velocity of the ring resonator, respectively. β (s) represents the loss of the ring resonator. The last term on the right side of Equation (1) corresponds to polarization, and N (s), κ and ρ (s) are the carrier density, coupling constant and macro polarization term, respectively. N (s) is a constant that is not 0 only inside the semiconductor amplifier. A semiconductor that is a laser medium is described by the Bloch equation of the following equations (2) and (3).

Here, W represents distribution inversion, and γ _⊥ and γ _// are a lateral relaxation constant and a vertical relaxation constant, respectively.

The electric field E (s, t) and the polarization ρ (s, t) are constituted by the natural mode U _j (s) of the rotating ring resonator as shown in the following equation.

Here, ν _j is the resonance frequency of mode j.

  In order to explain that the Sagnac effect occurs, it is sufficient to consider the existence of two eigenmodes that were in a near-degenerate state when the rotational angular velocity was zero. Accordingly, assuming that the electric field E (s, t) and the polarization ρ (s, t) are constituted only by these two modes (j = 1, 2), the following equations (5) and (6) Will be expanded as follows.

Here, E _j and ψ _j are the amplitude and phase of the mode indicated by j, respectively. ν ₀ is an arbitrary frequency close to ν _j (j = 1, 2) (ν _{0 to} ν _{1 to} ν ₂ ). By substituting Equation (5) and Equation (6) into Equation (1), the time evolution equations for each mode can be obtained.

A semiconductor laser is a medium belonging to class B (γ _⊥ >> γ _// , <β>). Therefore, the equation for polarization is expressed by the following equation according to the perturbation theory.

  Therefore, the equation for the distribution inversion is as follows (Non-Patent Document 4).

When the length L of the passive waveguide (optical fiber) is sufficiently longer than the length l of the active waveguide (L >> l), the effective light loss is the loss β _p in the passive waveguide. Determined by. In other words, <β> is a <β> ~β _p. Therefore, if there is a feature of γ _// >> _p , it can have a feature in class A (a ring resonator type ring laser comprising the semiconductor optical amplifier 1 and the optical fiber 2 satisfies this condition).

For example, β _p to 10 ³ (s ⁻¹ ) (optical fiber), β _a to 10 ⁹ -10 ¹¹ (s ⁻¹ ) (semiconductor amplifier) and γ _/// 10 ⁹ (s ⁻¹ ) (semiconductor). even if, as long as such a semiconductor optical amplifier 1 L (~1-10m) >> l ( ~1mm), it is possible meet the _{<β> ~β p << γ //} , class a Has the characteristics of a laser. Therefore, the distribution inversion can take a certain converged state sufficiently before the light state is moderately relaxed. According to popular perturbation theory, the distribution inversion is

  Therefore, by substituting equation (9) into equation (7) and using the following equation (10), the polarization for modes j = 1 and 2 can be obtained as in equation (11).

  Next, when Expression (5) and Expression (6) are substituted into Expression (1), the following expression can be obtained.

Here, Ψ = ψ ₁ −ψ ₂ (phase difference). Δν = ν ₁ −ν ₂ . That is, this Δν is the frequency of the Sagnac beat signal.

  The coefficients in the equations (12) to (14) are described as the following equations.

If the phase difference Φ does not satisfy the condition Φ >> | F (Φ) |, a lock-in phenomenon occurs as is well known, and dΦ / dt = 0. However, if this condition is satisfied, Φ (t) = Δνt. In this case, as shown in the equations (12) and (13), the amplitudes E ₁ and E ₂ of each mode oscillate at the frequency Δν through the modulation term. In particular, when E ₁ = E ₂ = t, that is, for a mode at the center of gain, the following equation holds.

Here, a = (α ₀ −β), b = s + 2c, d = 4 | Θ |, e = | ξ |, tan δ _k = −Δν / 2a, and tan δ _l = −Δν / a.

The amplitude _{E CCW} rotational wave amplitude _{E CW} and counterclockwise rotation wave clockwise (CW) (CCW), is obtained by the following equation.

Therefore, by substituting equation (22) into equation (5) and calculating equation (23), the amplitude I _{CW (CCW)} of the rotational wave in the CW direction and the CCW direction can be obtained as follows: it can.

The value in parentheses on the right side of the equation (24) is a constant, and E ² (t) varies depending on the frequency Δν of the Sagnac beat signal, as is clear from the equation (22). Therefore, the laser light CW and the laser light CCW The amplitude I _{CW (CCW)} (= light intensity) varies depending on the frequency Δν of the Sagnac beat signal.

Therefore, the frequency Δν of the Sagnac beat signal can be obtained by observing the amplitude I _CW (or I _CCW ) of one of the laser beam CW and the laser beam CCW without combining the laser beam CW and the laser beam CCW. Can be detected.

  The reason why such detection is possible is that there are amplitude modulation terms of Equation (12) and Equation (13). This term has a value proportional to the ratio L / l between the length L of the passive region and the length l of the active region. Therefore, this amplitude modulation term disappears when the ring laser is constituted only by an active medium, and amplitude modulation by the frequency Δν of the Sagnac beat signal does not occur. The fact that the link laser is composed of a passive region and an active region is an important factor causing an amplitude modulation term due to the frequency Δν of the Sagnac beat signal.

From the above, by observing the amplitude I _CW (or I _CCW ) of one of the laser beam CW and the laser beam CCW and calculating Δν using the equations (22) and (24), the Sagnac beat signal The frequency Δν can be detected.

Accordingly, the spectrum analyzer 6 receives the light intensity I _CW (or I _CCW ) of one of the laser light CW and the laser light CCW from the photodetector 5 and receives the received light intensity I _CW (or I _CCW). ), The frequency Δν of the Sagnac beat signal is detected by calculating the frequency Δν using the equations (22) and (24).

The optical gyro 10 is placed on the table 20, and the beat signal is based on the light intensity I _CW of the laser beam CW when the servo mechanism 30 and the controller 40 change the rotational angular velocity of the table 20 and the laser beams CW and CCW are not superimposed. The experimental result of detecting the frequency Δν of will be described. In the experiment, a current (62.5 mA) 1.03 times the threshold current was injected to oscillate the semiconductor optical amplifier 1 to generate laser beams CW and CCW.

  FIG. 4 is a diagram showing the relationship between the power and frequency of the beat signal, and FIG. 5 is a diagram showing the relationship between the frequency of the beat signal and the rotational angular velocity.

  In FIG. 4, the horizontal axis represents the frequency of the beat signal, and the vertical axis represents the power of the beat signal. FIG. 4 shows the relationship between the power and frequency of the beat signal when the optical gyro 10 is rotated at a rotational angular velocity of 270 degrees / s. In FIG. 5, the horizontal axis represents the rotational angular velocity, and the vertical axis represents the frequency and power of the beat signal.

  Referring to FIG. 4, the peak value of the beat signal was observed at a rotational angular velocity of 270 degrees / s.

  Therefore, it was found that the optical gyroscope 10 can observe the beat signal when the laser beams CW and CCW are not superimposed.

  Referring to FIG. 5, a straight line k1 indicates the relationship between the frequency and the rotational angular velocity. The frequency of the beat signal changes linearly with respect to the rotational angular velocity. More specifically, the frequency of the beat signal decreases linearly with respect to the rotational angular velocity in a region where the rotational angular velocity is negative, and linear with respect to the rotational angular velocity in a region where the rotational angular velocity is positive. (See the straight line k1). The proportionality coefficient (scale factor) on the straight line k1 is 3.9588 (kHz · sec / deg).

  Therefore, the rotational angular velocity can be detected by detecting the frequency Δν of the beat signal. On the straight line k1, the frequency of the beat signal is not observed in the range of −100 deg / sec to +80 deg / sec, because it is buried in 1 / (Δν) noise.

  The frequency Δν of the beat signal is theoretically expressed by Δν = (4A / (nλP)) Ω.

  Where A is the area of the region surrounded by the optical fiber 2, n is the refractive index of the optical fiber 2, λ is the wavelength of the laser light CW, CCW, and P is the laser light CW, CCW. Ω is the rotational angular velocity.

In the experiments shown in FIGS. 4 and 5, A = 0.998 m ² , n = 1.448, λ = 15788.0 nm, and P = 3.019 m. By substituting these values into the equation Δν = (4A / (nλP)) Ω and calculating the proportionality coefficient, a proportionality coefficient of 4.045 (kHz · sec / deg) is obtained.

  Therefore, the error between the experimentally obtained proportionality factor (3.958) and the theoretically obtained proportionality factor 4.045 is 2.2%, and the optical gyroscope 10 uses the Sagnac effect. It turns out that it is a light gyro.

  Upon receiving the beat signal frequency Δν from the spectrum analyzer 6, the detector 7 detects the rotational angular velocity corresponding to the received beat signal frequency Δν with reference to the straight line k 1. Thereby, in the optical gyro 10, the rotational angular velocity can be detected without superimposing the laser light CW and the laser light CCW.

  FIG. 6 is a schematic diagram showing the configuration of another optical gyro according to the first embodiment. The optical gyro according to the first embodiment may be an optical gyro 10A shown in FIG. The optical gyro 10A is the same as the optical gyro 10 except that the coupler 3 of the optical gyro 10 shown in FIG. 1 is replaced with the coupler 8 and the optical fiber 4 is replaced with the optical fiber 9.

  The coupler 8 couples the optical fiber 2 with the optical fiber 9 so that the laser light CCW propagating through the optical fiber 2 is 99% and the laser light CCW propagating through the optical fiber 9 is 1%.

  The optical fiber 9 is coupled to the optical fiber 2 by the coupler 8, and guides a part (1%) of the laser light CCW propagating through the optical fiber 2 to the photodetector 5.

  FIG. 7 is a schematic diagram showing the configuration of the coupler 8 shown in FIG. Referring to FIG. 7, the coupler 8 includes guides 81 and 82. The guides 81 and 82 couple the two optical fibers by sandwiching the two optical fibers in contact with each other.

  When the optical fiber 9 is coupled to the optical fiber 2, the optical fiber 9 is disposed between the guides 81 and 82 so as to contact the optical fiber 2. In this case, the core 21 of the optical fiber 2 is disposed close to the core 91 of the optical fiber 9. Note that one end of the optical fiber 9 is terminated by a terminator 92.

  1% of the laser light CCW propagating counterclockwise in the optical fiber 2 leaks from the core 21 to the core 91 in the vicinity of the core 21 and the core 91. Then, 1% of the laser light CCW leaked to the core 91 propagates through the optical fiber 9.

  Thus, the laser light CCW propagating through the optical fiber 9 is a part (1%) of the laser light CCW propagating through the optical fiber 2.

Also in the optical gyro 10A, the relationship between the beat signal frequency Δν and the rotational angular velocity is represented by a straight line k1 shown in FIG. In the optical gyro 10 </ b> A, the photodetector 5 detects the light intensity I _CCW of the laser light CCW propagating through the optical fiber 9 and outputs the detected light intensity I _CCW to the spectrum analyzer 6. Then, the spectrum analyzer 6 detects the frequency Δν of the Sagnac beat signal based on the light intensity I _CCW received from the photodetector 5, using the equations (22) and (24), and the detected frequency Δν Output to the detector 7. The detector 7 receives the frequency Δν from the spectrum analyzer 6 and detects the rotational angular velocity corresponding to the received frequency Δν with reference to the straight line k1. Thereby, in the optical gyro 10A, the rotational angular velocity is detected without superimposing the laser light CW and the laser light CCW.

  FIG. 8 is a schematic diagram showing a configuration of a gyro system using the optical gyro 10 shown in FIG. Referring to FIG. 8, the gyro system 100 includes a configuration in which the optical gyro 10 is configured using a wireless device 60 instead of the photodetector 7, and a remote controller 70 is added to the configured optical gyro 10.

  The wireless device 60 includes a digitizer 61, a controller 62, and an antenna 63. The remote controller 70 includes a personal computer 71 and an antenna 72.

  The digitizer 61 receives the beat signal frequency Δν from the spectrum analyzer 6 and outputs the received beat signal frequency Δν to the controller 62. The controller 62 detects the rotational angular velocity by the above-described method based on the beat signal frequency Δν. Then, the controller 62 modulates the detected rotational angular velocity into a predetermined method and transmits it through the antenna 63.

  The antenna 72 receives radio waves from the wireless device 60 and outputs the received radio waves to the personal computer 71. The personal computer 71 obtains the rotational angular velocity detected by the optical gyro 10 by demodulating radio waves from the antenna 72.

  As described above, in the gyro system 100, the optical gyro 10 receives the radio device 60 that transmits the detected rotation angular velocity by a radio signal and the radio wave from the radio device 60 and detects the rotation angular velocity detected by the optical gyro 10. Therefore, even if the optical gyro 10 rotates at high speed on the table 20, the rotational angular velocity detected by the optical gyro 10 can be acquired by the stationary remote controller 70.

  In the gyro system 100, an optical gyro 10A may be used instead of the optical gyro 10.

  In the above description, 1% of the laser light CW (or laser light CCW) propagating in the optical fiber 2 is leaked to the optical fiber 4 (or optical fiber 9). However, the present invention is not limited to this. Instead, 1% to 10% of the laser light CW (or laser light CCW) propagating through the optical fiber 2 may leak into the optical fiber 4 (or optical fiber 9).

[Embodiment 2]
FIG. 9 is a schematic diagram showing the configuration of the optical gyro according to the second embodiment. The optical gyro 10B according to the second embodiment is obtained by replacing the semiconductor optical amplifier 1, the optical fibers 2 and 4, the coupler 3, and the photodetector 5 of the optical gyro 10 shown in FIG. The same as the optical gyroscope 10.

  The semiconductor element 110 oscillates the laser beam CW and the laser beam CCW, propagates the oscillated laser beam CW clockwise, propagates the oscillated laser beam CCW counterclockwise, and also transmits the laser beam CW and the laser beam CCW. Is detected and output to the spectrum analyzer 6.

  FIG. 10 is a perspective view of the semiconductor element 110 shown in FIG. The semiconductor element 110 includes a substrate 111, a semiconductor optical amplifier 112, semiconductor waveguides 113 and 114, and a photodetector 115. The semiconductor waveguide 114 is terminated at one end by a terminator 1141.

  The substrate 111 is made of, for example, n-type gallium arsenide (GaAs). The semiconductor optical amplifier 112, the semiconductor waveguides 113 and 114, and the photodetector 115 are formed on the substrate 111.

  The semiconductor optical amplifier 112 is provided on a part of the circumference of the semiconductor waveguide 113. The semiconductor waveguide 113 has a substantially circular shape and has a square cross-sectional shape. The semiconductor waveguide 113 is in contact with both ends of the semiconductor optical amplifier 112. The semiconductor waveguide 114 has a generally arc shape and has a quadrangular cross section. The semiconductor waveguide 114 is in contact with the semiconductor waveguide 113 and the other end is in contact with the photodetector 115.

  The photodetector 115 is made of p-type GaAs / GaAs / n-type GaAs stacked in a direction perpendicular to the substrate 111.

  FIG. 11 is a cross-sectional view of the semiconductor optical amplifier 112 shown in FIG. The semiconductor optical amplifier 112 includes cladding layers 1121 and 1123, an active layer 1122, a contact layer 1124, a positive electrode 1125, and a negative electrode 1126.

  The cladding layer 1121, the active layer 1122, the cladding layer 1123, and the contact layer 1124 are sequentially stacked on the substrate 111. The positive electrode 1125 is formed on the contact layer 1124. The negative electrode 1126 is formed on the back surface of the substrate 111.

The clad layer 1121 is made of, for example, n-type Al _0.8 Ga _0.2 As. The active layer 1122 includes three well layers 220 and four barrier layers 221. The three well layers 220 and the four barrier layers 221 are alternately stacked. The well layer 220 is made of, for example, GaAs, and the barrier layer 221 is made of, for example, Al _0.2 Ga _0.8 As. That is, the active layer 1122 has a quantum well structure.

The clad layer 1123 is made of, for example, p-type Al _0.8 Ga _0.2 As. The contact layer 1124 is made of, for example, p-type GaAs.

  The semiconductor optical amplifier 112 laser-oscillates when current is injected from the positive electrode 1125 and the negative electrode 1126, emits laser light CW from one end face 112A, and emits laser light CCW from the other end face 112B.

12 is a cross-sectional view of a part of the semiconductor optical amplifier 112 and the semiconductor waveguide 113 shown in FIG. The semiconductor waveguide 113 is composed of semiconductor layers 1131 to 1133. The semiconductor layer 1131 is made of, for example, n-type Al _0.8 Ga _0.2 As, the semiconductor layer 1132 is made of, for example, GaAs, and the semiconductor layer 1133 is, for example, p-type Al _0.8 Ga _0.2 As. Consists of.

  The semiconductor layer 1131 is formed over the substrate 111, the semiconductor layer 1132 is formed over the semiconductor layer 1131, and the semiconductor layer 1133 is formed over the semiconductor layer 1132. The semiconductor layer 1131 is provided in contact with the cladding layer 1121 of the semiconductor optical amplifier 112, the semiconductor layer 1132 is provided in contact with the active layer 1122 of the semiconductor optical amplifier 112, and the semiconductor layer 1133 is provided in the semiconductor optical amplifier 112. It is provided in contact with the cladding layer 1123. The semiconductor layer 1132 has a refractive index of n1, and each of the semiconductor layers 1131 and 1133 has a refractive index of n2 smaller than n1.

  The semiconductor optical amplifier 112 oscillates laser light, emits the oscillated laser light as laser light CW from the end face 112A to the semiconductor layer 1132 in the semiconductor waveguide 113, and from the end face 112B as semiconductor laser 113 as the laser light CCW. The light is emitted to the inner semiconductor layer 1132. Then, since the semiconductor layers 1131 and 1133 having a refractive index lower than that of the semiconductor layer 1132 are provided above and below the semiconductor layer 1132, the laser beams CW and CCW emitted into the semiconductor layer 1132 are perpendicular to the substrate 111. Optically confined in any direction. Further, since the semiconductor waveguide 113 is in contact with air in the in-plane direction of the substrate 111, the laser beams CW and CCW emitted into the semiconductor layer 1132 are optically confined also in the in-plane direction of the substrate 111. Therefore, the laser beams CW and CCW emitted into the semiconductor layer 1132 are optically confined and propagate in the semiconductor waveguide 113.

  Note that the semiconductor waveguide 114 shown in FIG. 10 has the same configuration as the semiconductor waveguide 113 shown in FIG.

  FIG. 13 is a plan view of the semiconductor element 110 shown in FIG. The semiconductor optical amplifier 112 is disposed on a part of the circumference of the semiconductor waveguide 113, and the semiconductor waveguide 113 is disposed so as to be in contact with both end faces 112 </ b> A and 112 </ b> B of the semiconductor optical amplifier 112.

  The semiconductor waveguide 114 is terminated so that one end thereof is terminated by a terminator 1141 and is in contact with the semiconductor waveguide 113, and the other end is in contact with the photodetector 115. The contact portion between the semiconductor waveguide 113 and the semiconductor waveguide 114 functions as a coupler 116 that guides part of the laser light CW propagating through the semiconductor waveguide 113 to the semiconductor waveguide 114.

  The semiconductor optical amplifier 112 oscillates the laser beams CW and CCW, emits the oscillated laser beam CW from the end surface 112A into the semiconductor waveguide 113, and oscillates the oscillated laser beam CCW from the end surface 112B into the semiconductor waveguide 113. Exit. In addition, the semiconductor optical amplifier 112 amplifies the laser light CW that propagates clockwise through the semiconductor waveguide 113 and is incident from the end face 112B, and emits the amplified laser light CW from the end face 112A into the semiconductor waveguide 113. To do. Further, the semiconductor optical amplifier 112 amplifies the laser light CCW that has been propagated counterclockwise in the semiconductor waveguide 113 and entered from the end face 112A, and the amplified laser light CCW enters the semiconductor waveguide 113 from the end face 112B. Exit.

  The semiconductor waveguide 113 propagates the laser light CW clockwise and propagates the laser light CCW counterclockwise.

  The semiconductor waveguide 114 propagates a part of the laser light CW propagating in the semiconductor waveguide 113 to the photodetector 115 as the laser light CW.

The photodetector 115 detects the light intensity I _CW of the laser light CW propagating through the semiconductor waveguide 114, detects the light intensity I _CW , and outputs the light intensity I _CW to the spectrum analyzer 6.
The semiconductor optical amplifier 112 can oscillate and amplify the laser light CW rotating clockwise and the laser light CCW rotating counterclockwise by connecting the semiconductor waveguide 113 to both ends. The amplifier 112 and the semiconductor waveguide 113 constitute a ring resonator type ring laser. That is, the ring laser including the semiconductor optical amplifier 112 and the semiconductor waveguide 113 is a laser including an activation region (semiconductor optical amplifier 112) and a passive region (semiconductor waveguide 113).

  14 to 16 are first to third process diagrams showing a method of manufacturing the semiconductor element 110 shown in FIG. 9, respectively. FIG. 17 is a plan view of the semiconductor element 110 in the step (c) shown in FIG. 14 and the step (i) shown in FIG.

When the manufacture of the semiconductor element 110 is started, the semiconductor layers 121 to 124 are sequentially formed on the substrate 111 by metal organic chemical vapor deposition (MOCVD). The semiconductor layer 121 is made of n-type Al _0.8 Ga _0.2 As, the semiconductor layer 122 is made of a laminated structure in which GaAs and Al _0.2 Ga _0.8 As are alternately laminated, and the semiconductor layer 123 is made of P type Al _0.8 Ga _0.2 As, and the semiconductor layer 124 is made of p type GaAs (see FIG. 14A).

  Thereafter, a resist is applied onto the semiconductor layer 124, and the applied resist is patterned to form a resist pattern 120 on the semiconductor layer 124 (see FIG. 14B). In this case, the resist pattern 120 is a pattern that covers only a region where the semiconductor optical amplifier 112 is formed.

Then, the semiconductor layers 122 to 124 are etched using the resist pattern 120 as a mask, and the resist pattern 120 is removed. As a result, the semiconductor optical amplifier 112, the semiconductor layer 1131 for the semiconductor waveguides 113 and 114, and the n-type Al _0.8 Ga _0.2 As for the photodetector 115 are formed on the substrate 111 (FIG. 14 ( c)).

  When the step (c) shown in FIG. 14 is completed, the semiconductor optical amplifier 112 and the semiconductor layer 1131 for the semiconductor waveguides 113 and 114 are formed on the substrate 111 (see FIG. 17A).

  After step (c) shown in FIG. 14, a semiconductor layer 130 made of GaAs is formed on the entire surface of the substrate 111 by MOCVD (see FIG. 15D). In this case, the thickness of the semiconductor layer 130 is substantially the same as the thickness of the active layer 1122.

  Subsequently, a resist pattern 140 is formed on the surface of the semiconductor layer 130 in a region where the semiconductor waveguides 113 and 114 and the photodetector 115 are formed (see FIG. 15E).

Then, the semiconductor layer 130 is etched using the resist pattern 140 as a mask, and the resist pattern 140 is removed. As a result, semiconductor optical amplifier 112, semiconductor layers 1131 and 1132 for semiconductor waveguides 113 and 114, and n-type Al _0.8 Ga _0.2 As / GaAs for photodetector 115 are formed on substrate 111 ( (Refer to (f) of FIG. 15).

Thereafter, a semiconductor layer 150 made of p-type Al _0.8 Ga _0.2 As is formed on the entire surface of the substrate 111 by MOCVD (see FIG. 16G). In this case, the thickness of the semiconductor layer 150 is substantially the same as the thickness of the cladding layer 1123.

  Subsequently, a resist pattern 160 is formed on the surface of the semiconductor layer 150 in a region where the semiconductor waveguides 113 and 114 and the photodetector 115 are formed (see (h) of FIG. 16).

Then, the semiconductor layer 150 is etched using the resist pattern 160 as a mask, and the resist pattern 160 is removed. As a result, the semiconductor optical amplifier 112, the semiconductor layers 1131 to 1133 for the semiconductor waveguides 113 and 114, and the n-type Al _0.8 Ga _0.2 As / GaAs / p-type Al _0.8 Ga ₀ for the photodetector 115. _.2 As is formed on the substrate 111 (see (i) of FIG. 16). Then, the positive electrode 1125 is formed on the contact layer 1124, and the negative electrode 126 is formed on the back surface of the substrate 111 (see (i) of FIG. 16). Thus, the semiconductor element 110 is completed (see FIG. 17B).

In the semiconductor element 110, the semiconductor optical amplifier 112 is an active region, and the semiconductor waveguides 113 and 114 are passive regions. Therefore, the light intensity I _CW of the laser beam CW propagating through the semiconductor waveguides 113 and 114 is expressed by the above-described equation (24), and changes depending on the beat signal frequency Δν.

As a result, also in the optical gyro 10B, the rotational angular velocity can be detected by detecting the light intensity I _CW of the laser light CW before superposition.

  In the above description, the semiconductor waveguide 113 has a substantially circular shape. However, in the present invention, the semiconductor waveguide 113 is not limited thereto, and the semiconductor waveguide 113 has a polygonal shape such as a substantially triangular shape, a substantially rectangular shape, and a substantially pentagonal shape. You may have the shape of.

  In addition, the semiconductor element 110 may include a semiconductor waveguide that guides a part of the laser light CCW propagating through the semiconductor waveguide 113 to the photodetector 115 instead of the semiconductor waveguide 114.

  Furthermore, the gyro system according to the present invention may include an optical gyro 10B shown in FIG.

  Others are the same as in the first embodiment.

  In the first embodiment described above, the optical gyros 10 and 10A using the semiconductor optical amplifier 1 and the optical fibers 2 and 4 will be described. In the second embodiment, the semiconductor optical amplifier 112 and the semiconductor waveguide 113 are described. The optical gyro 10B using the optical regions of the optical gyro 10B is generally described. The optical gyro according to the present invention generally includes an activation region for oscillating and amplifying the lasers CW and CCW, and laser beams CW and CCW from the activation region. A passive region that is rotated clockwise and counterclockwise, and any of laser light CW and CCW emitted from the activation region into the passive region when the activation region and the passive region are rotated in a predetermined plane. Detecting means for detecting the rotational angular velocities of the active region and the passive region based on the change frequency of the light intensity of one of the laser beams It may be one.

  In the present invention, the optical fibers 2 and 4 constitute a “waveguide”, and the semiconductor waveguides 113 and 114 constitute a “waveguide”.

  The wireless device 60 constitutes a “transmitting device”.

  Further, the remote controller 70 constitutes a “receiving device”.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to an optical gyro capable of detecting a rotational speed without superimposing a laser beam propagating clockwise and a laser beam propagating counterclockwise. The present invention is also applied to a gyro system including an optical gyro capable of detecting a rotational speed without superimposing a laser beam propagating clockwise and a laser beam propagating counterclockwise.

It is the schematic which shows the structure of the optical gyro according to Embodiment 1 of this invention. It is a top view of the semiconductor optical amplifier shown in FIG. It is the schematic which shows the structure of the coupler shown in FIG. It is a figure which shows the relationship between the power and frequency of a beat signal. It is a figure which shows the relationship between the frequency of a beat signal, and a rotation angular velocity. It is the schematic which shows the structure of the other optical gyroscope by Embodiment 1. FIG. It is the schematic which shows the structure of the coupler shown in FIG. It is the schematic which shows the structure of the gyro system using the optical gyro shown in FIG. FIG. 5 is a schematic diagram illustrating a configuration of an optical gyro according to a second embodiment. FIG. 10 is a perspective view of the semiconductor element shown in FIG. 9. It is sectional drawing of the semiconductor optical amplifier shown in FIG. FIG. 11 is a cross-sectional view of part of the semiconductor optical amplifier and the semiconductor waveguide shown in FIG. 10. FIG. 10 is a plan view of the semiconductor element shown in FIG. 9. FIG. 10 is a first process diagram showing a method of manufacturing the semiconductor element shown in FIG. 9. FIG. 10 is a second process diagram illustrating the method of manufacturing the semiconductor element illustrated in FIG. 9. FIG. 10 is a third process diagram illustrating the method of manufacturing the semiconductor element illustrated in FIG. 9. It is a top view of the semiconductor element in the process (c) shown in FIG. 14, and the process (i) shown in FIG.

Explanation of symbols

  1,112 semiconductor optical amplifier, 1A, 1B, 112A, 112B end face, 2,4 optical fiber, 3,116 coupler, 5,115 photodetector, 6 spectrum analyzer, 7 detector, 10, 10A, 10B optical gyro , 11, 1122 Active layer, 12, 13 Optical confinement layer, 14, 15 Antireflection film, 20 table, 21, 41 core, 30 Servo mechanism, 31, 32 guide, 40, 62 controller, 42, 92, 1141 Terminator , 60 wireless device, 61 digitizer, 63, 72 antenna, 70 remote controller, 100 gyro system, 110 semiconductor element, 111 substrate, 113, 114 semiconductor waveguide, 121-124, 130, 150, 1131-1133 semiconductor layer, 120 , 140, 160 resist pattern, 20 well layers, 221 barrier layer, 1121 and 1123 cladding layer, 1124 a contact layer, 1125 a positive electrode, 1126 a negative electrode.

Claims (8)

The first and second laser beams are oscillated, the oscillated first and second laser beams are amplified, the first laser beam is rotated clockwise, and the second laser beam is counterclockwise. A ring laser that rotates around,
The ring laser based on the frequency of change of the light intensity of one of the first and second laser beams propagating through the ring laser when the ring laser rotates in a predetermined plane An optical gyro comprising detection means for detecting the rotation angular velocity of the optical gyro. The ring laser is
A first end face and a second end face opposite to the first end face, and oscillates the first and second laser beams to cause the first and second end faces to oscillate the first and second end faces, respectively. A semiconductor optical amplifier that emits a second laser beam;
A waveguide for propagating the first and second laser beams emitted from the semiconductor optical amplifier,
The waveguide guides the first laser light emitted from the first end face to the semiconductor optical amplifier from the second end face by rotating the first laser light in the clockwise direction, and emits the first laser light from the second end face. 2. The optical gyro according to claim 1, wherein the second laser light is rotated counterclockwise and guided from the first end face to the semiconductor optical amplifier.   The optical gyro according to claim 1, wherein the waveguide is made of an optical fiber. The waveguide is
A first optical fiber that rotates the first laser light in the clockwise direction and rotates the second laser light in the counterclockwise direction;
A second optical fiber;
A coupler for guiding a part of one of the first and second laser lights in the first optical fiber to the second optical fiber;
4. The optical gyro according to claim 3, wherein the detection unit detects a rotational angular velocity of the ring laser based on a change frequency of a light intensity of one of the laser beams in the second optical fiber. An activation region for oscillating the first and second laser beams and amplifying the oscillated first and second laser beams;
A passive region for rotating the first laser beam clockwise and rotating the second laser beam counterclockwise;
One of the first and second laser beams emitted from the activation region into the passive region when the activation region and the passive region rotate within a predetermined plane. An optical gyro comprising detection means for detecting rotational angular velocities of the activation region and the passive region based on a change frequency of light intensity. The activation region comprises a semiconductor optical amplifier,
The optical gyro according to claim 5, wherein the passive region includes semiconductor waveguides connected to both ends of the semiconductor optical amplifier.   The optical gyro according to claim 5 or 6, wherein the activation region and the passive region are formed on the same semiconductor substrate. The optical gyro according to any one of claims 1 to 7,
A transmission device that converts the rotational angular velocity detected by the detection means into a radio signal and transmits the radio signal;
A gyro system comprising: a receiving device that receives a radio signal transmitted from the transmitting device, decodes the received radio signal, and acquires the rotational angular velocity.

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