JPS6221015A - Optical fiber gyroscope apparatus - Google Patents

Abstract

PURPOSE:To obtain an apparatus free from the effect of noise due to a self- coupling effect with limited loss, by changing over an optical switch to apply all of laser outputs or outputs of a fiber coupler to a fiber coil or a light receiving element separately. CONSTITUTION:With an optical switch 8 in b-a connection, the outputs of a laser 1 are applied to a fiber coil 5 through a polarizer 3 and a photocoupler 4 as double, turn light. The optical pulse propagated through the coil 5 after the time ' and is incident on a photodiode 7 through the coupler 4, the polarizer 3 and the optical switch 8 set to c-a connection to be detected. The intensity of the interference light being detected corresponds to the phase difference of the double-turn light thus returned and in that the phase difference corresponds to the angular velocity of turn, the detection output corresponds to the angular velocity of turn. Moreover, most of the return light incident on the terminal (a) is emitted at the terminal (c), minimizing the loss. Even when a part of the return light is given to the element 1 owing to the leakage through the switch 8, there is no noise otherwise generated by self-coupling effect as the laser is in the state of producing no output.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvement of loss characteristics in an optical fiber gyro.

(Prior Art) An optical fiber gyro device measures angular velocity by utilizing the fact that the phases of light propagated in opposite directions in an optical fiber ring shift due to rotation of the ring (3agnac effect). be. That is, the rotational angular velocity is measured by interfering the clockwise light and the counterclockwise light and detecting a change in the intensity of the interference light corresponding to the phase difference.

FIG. 4 is a configuration explanatory diagram showing an example of a conventional optical fiber gyro device. The output light from the laser light source 1 is transmitted to the fiber coupler 2. The light is applied to the fiber coil 5 via the polarizer 3 and the fiber coupler 4 as bidirectional light. The light propagated through the fiber coil 5 is coupled again by the fiber coupler 4, and is incident on the light receiving element 7, which is a photodiode, via the polarizer 3 and the fiber coupler 2, and detects the interference light intensity corresponding to the phase difference. Phase modulator 6 improves the sensitivity of phase detection. By polarizing the light from the light source 1 and the light returning from the fiber coil 5 using the polarizer 3, noise contained in the phase difference signal is reduced.

FIG. 5 is a block diagram for explaining the operation of the fiber couplers 2 and 4 shown in FIG. Input light C0 applied to one input at one end of the fiber coupler is branched into 50% output light CI+02 from both outputs at the other end. In this case, the phase shift that occurs when the fiber coupler goes in parallel (co-4C1) is θ7, and when the fiber coupler goes crosswise (Co-0
Assuming that the phase shift occurring in 2) is θ2, when the fiber coil is not rotating, the polarizer 3
The phase shifts that occur in the two directions of light while the light enters the fiber coil 5, propagates through the fiber coil 5, and returns to the polarizer 3 are both equal to θ1+θ2, so they are canceled out and no phase difference occurs.

(Problem to be solved by the invention) However, in the apparatus shown in FIG.
Since the emitted light from the laser light source 1 is not used, there is a large loss (in the case of the device shown in Fig. 4, 1/1/2 of the light emitted from the laser light source 1
8 enters the photodiode 7). Therefore, since the output light power is small, the S/N ratio of photodetection decreases,
As a result, the detection sensitivity of rotational angular velocity decreases.

There is also the problem that the resonance of the laser is disturbed when the light returns to the laser element, increasing the noise of the laser light (self-coupling effect).

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to realize an optical fiber gyro Mat that has low loss and is free from the influence of noise due to the self-coupling effect.

(Means for Solving the Problems) The optical fiber gyro device of the present invention separates the light from the light source into two, causes the fiber coils to propagate in opposite directions, and then makes them interfere again, so that the light beams in both left and right directions are separated. This device relates to an optical fiber gyro device that measures angular velocity from the phase difference that occurs.Its features include a fiber coupler in which both ends of a fiber coil are connected to one end of the fiber coil, and the other end of the fiber coupler is connected to one end of the fiber coupler. A light source and a light receiving element are respectively connected to the other ends of the optical switch, and when the optical switch is switched, light from the light source propagates through the fiber coil and then enters the light receiving element. The point is that it is structured as follows.

(Function) According to the device configured as described above, by switching the optical switch, all of the laser output can be applied to the fiber coil, and all of the output from one end of the fiber coupler can be applied to the light receiving element.

(Example) The present invention will be explained in detail below using the drawings.

FIG. 1 is a configuration explanatory diagram showing an embodiment of an optical fiber gyro device according to the present invention. The same parts as in FIG. 4 are given the same symbols and their explanations will be omitted.

8 is a 1×2 type optical switch in which one end of a fiber coupler 4 is connected to one terminal a via a polarizer 3, and a laser light source 1 and a light receiving element 7 are connected to the other two terminals a and c, respectively. It is.

The operation of the apparatus shown in FIG. 1 will be explained below using the time chart shown in FIG. The connection of the optical switch 8 is switched at the timing shown in FIG. 2<A), and the laser output is intermittently emitted at the timing shown in FIG. 2(B). That is, with the optical switch 8 in the b-a connection state, the output of the laser 1 is applied to the fiber coil 5 via the polarizer 3 and the photocoupler 4 in both directions. The optical pulse propagated through the fiber coil 5 returns after a time τ (normally the length of the fiber coil 5 is 500 m to 2 km, so = 2.5 to 10
μs), again fiber coil 4. Mitsuko Sono 3 and C-a
The photodiode 7 is connected to the photodiode 7 via the optical switch 8.
and is detected as shown in FIG. 2(C). The interference light intensity detected by the photodiode 7 corresponds to the phase difference of the returned biconcave light, and this phase difference corresponds to the rotational angular velocity, hs +3, and the detection output from the photodiode 7 corresponds to the rotational angular velocity.

According to the optical fiber gyro device having such a configuration, since an optical switch is used, most of the light incident on the b terminal of the optical switch 8 is emitted from the a terminal, propagates through the fiber coil 5, and returns. Regarding light, since most of the light incident on the C terminal of the optical switch 8 is emitted from the C terminal, the loss is extremely small compared to the conventional example.

Furthermore, since most of the light that propagates through the fiber coil 5 and returns to the photodiode 7 side, no return light is given to the laser element 1. Even if some of the returned light is given to the laser element 1 due to leakage from the optical switch 8, since the radar is not in an output state at that time, noise due to the self-coupling effect will not be generated.

FIG. 3 is a time chart showing a modification of the above embodiment. In the device shown in Fig. 1, the laser output is continuously operated (Fig. 3 (B)) and the optical switch 8 is turned on and off (3rd
(Δ)) is made to enter the fiber coil 5, and the light returning from the fiber coil 5 is all directed to the photodiode 7, as in the case of Fig. 2. Figure 3 (C)).

According to the optical fiber gyro device having such a configuration, there is no need to turn on and off the laser output, so the configuration of the laser drive circuit becomes simple.

Furthermore, even if some of the returned light is applied to the laser element 1 due to leakage of the optical switch 8, the timing at which the returned light is applied to the laser element 1 and the timing at which the optical switch 8 becomes connected to b-a are different. Even if a self-coupling effect occurs due to the returned light, the Ray If output at that time is not sent to the fiber coil 5, and therefore does not adversely affect the detection output.

(Effects of the Invention) As described above, according to the present invention, it is possible to realize an optical fiber gyro device with a simple configuration that has little loss and is not affected by noise due to the self-coupling effect.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an embodiment of the optical fiber gyro device according to the present invention, FIG. 2 is a time chart for explaining the operation of the device in FIG. 1, and FIG. 3 is a modification of the device in FIG. 1. A time chart for explaining an example, FIG. 4 is a configuration explanatory diagram without showing a conventional optical fiber gyro device, and FIG.
FIG. 3 is a configuration diagram for explaining the operation of fiber couplers 2 and 4 shown in the figure. DESCRIPTION OF SYMBOLS 1... Light source, 4... Fiber coupler, 5... Fiber coil, 7... Light receiving element, 8... Optical switch. Figure 4 Figure 5

Claims (1)

[Claims] An optical fiber gyro device that separates light from a light source into two, propagates the light in opposite directions through a fiber coil, and then makes them interfere again to measure angular velocity from the phase difference generated between the left and right lights. a fiber coupler to which both ends of the fiber coil are respectively connected to one end of the fiber coil; an optical switch to which the other end of the fiber coupler is connected in relation to one end of the fiber coil; 1. An optical fiber gyro device comprising a light source and a light receiving element to be connected, and configured such that light from the light source is applied to the light receiving element after propagating through a fiber coil by switching an optical switch.