JPS63128225A - Modulating fiber optic gyro - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a modulating fiber optic gyro with a fault detector.

[Conventional technology]

Regarding the conventional modulating optical fiber gyro, see Ektronics Letters Vol. 19, No. 23 (1983) No. 99.
From page 7 to page 999 (ELECTRONIC3LETT
ER3VoQ, 19 N (L23 (1983) P
997-P999).

[Problem that the invention seeks to solve]

The modulation type optical fiber gyro described above has a problem in that no consideration is taken in the event of a failure, and that it continues to output an incorrect output in the event of a failure.

An object of the present invention is to provide a modulating optical fiber gyro having a function of self-diagnosing the presence or absence of a failure.

[Means for solving problems]

In order to achieve the above object, the present invention adds to the basic configuration of a conventional modulating optical fiber gyro, an AC detection means for detecting an AC component related to the drive frequency of the optical modulator of the output of the optical system; The present invention is characterized in that a failure detector is provided, which includes a failure determination section that determines the presence or absence of a failure based on the magnitude of the detected value of the AC detection means, and a display section that displays the determination result of the failure determination section.

[Effect]

Since the modulating optical fiber gyro of the present invention is configured as described above, when a failure occurs in the modulating optical fiber gyro, the detected value by the AC detecting means fluctuates, and this is determined by the failure determination section and the result is determined. This can prevent erroneous outputs from continuing to be output due to failures.

〔Example〕

Embodiments of the present invention will be described below with reference to block diagrams shown in the drawings.

First, to explain the basic configuration of a modulating optical fiber gyro, a beam emitted from a coherent light source 1 such as a laser diode or a superluminescent diode, such as a laser, is passed through an optical fiber, and two optical fibers are connected to each other. An optical fiber loop made of several hundred meters of optical fiber wound into a coil, for example, is put into an optical coupler 2 that is placed close to each other and split by the evanescent effect, and is split into two, and one of the two light beams is passed through an optical modulator 4. Put it in 3.

The light flux exiting the optical fiber loop 3 is input into the optical coupler 2 again and is split into two parts, one of which is returned to the coherent light source 1 side, and the other is sent to a photoelectric conversion section 5 that is a combination of a photodiode and a current-voltage conversion amplifier, for example. I'm putting it in.

On the other hand, among the light beams that are first split into two by the optical coupler 2, the other enters the optical modulator 4 through the optical fiber loop 3, and the light beam that comes out from there is split into two by the optical coupler 2, one of which is made into a coherent beam. One light source is inserted into the light source 1, and the other is inserted into the photoelectric conversion section 5.

This optical modulator 4 is a device in which an optical fiber of several meters is coiled around a cylindrical electrostrictive element to increase or decrease the optical path length at a high frequency. Here, for ease of explanation, the photoelectric conversion section 5 passes through the coherent light source 1, the optical coupler 2, the optical modulator 4, the optical fiber loop 3, and the optical coupler 2 in this order.
The light flux that reaches the point is called a counterclockwise light flux, and the light flux that travels in the opposite direction is called a clockwise light flux. The above parts except for the photoelectric conversion section 5 are the basic configuration of the optical system of a modulating optical fiber gyro. Generally, each component is mainly composed of an optical fiber, for example, a single mode polarization maintaining optical fiber, and there is a gap between the components. They are also connected by optical fibers, and the connecting portions are connected by fusion splicing.

Components other than these are electrical components, and each component is electrically connected. The output signal of the oscillator 6, which consists of a crystal oscillator, frequency divider, filter, etc., is applied to the optical modulator 4, frequency converter 7, and synchronous detector 8, and the frequency converter 7 uses, for example, the square characteristic of the multiplier. The double frequency generator converts the signal into a double frequency signal and applies it to the synchronous detector 9. On the other hand, it is processed by a processing unit 10 such as a microcomputer, and an analog quantity or numerical value is output as output A in proportion to the input angular velocity, that is, the speed at which these parts rotate together.

The above portion is the basic configuration of a phase modulation type optical fiber gyro, which is typical among conventional modulation type optical fiber gyros. On the other hand, the part described next is a newly added configuration. That is, for example, it consists of a combination of a multiplier and a low-pass filter, selects and rectifies only the alternating current component of a specific frequency from the output of the photoelectric conversion unit 5, and further smoothes it to produce a direct current proportional to the amplitude of the alternating current component of the specific frequency. Synchronous detector 8 converts into
The respective outputs of ゜9 are added to an adder 11 mainly composed of, for example, an operational amplifier, the adder 11 adds the absolute values of the respective signals, and the output is added to a failure determination section 12 which is a voltage comparator. If the output of the adder 11 exceeds either the upper limit value or the lower limit value in this failure determination section 12,
The presence or absence of a failure is determined by determining a failure and outputting i', -' 1.The result is displayed on the display unit 13, for example, by blinking a lamp, and at the same time an electric signal B is output.
Output. Here, a portion consisting of the synchronous detector 8.9 and the adder 11 is referred to as AC detection means 14.

In this configuration, first, a case where there is no failure and no input angular velocity will be described.

When an alternating current voltage with constant frequency and voltage is applied to the optical modulator 4 so as to achieve a predetermined degree of modulation, the phase difference between the clockwise light flux and the counterclockwise light flux entering the photoelectric converter 5 is input. It changes in proportion to the magnitude of acceleration, and due to the unique characteristics of the phase modulation type optical fiber gyro, the output of the gap detector 8, that is, the AC component of the output of the photoelectric converter 5 that is equal to the driving frequency of the optical modulator 4. The value is proportional to the sin of the input angular velocity, while the output of the synchronous detector 8, that is, the AC component with a frequency twice the driving frequency, is proportional to the sin of the input angular velocity.
It is proportional to os. Therefore, to make the explanation easier to understand, the output of the synchronous detector 8 is 0%, and the output of the synchronous detector 9 is 100%.

When the angular velocity is 100%, that is, the phase difference of the light waves is 90'', the output of the synchronous detector 8 is 100%, and the output of the synchronous detector 9 is 0%.Therefore, the output of the synchronous detector 8 is 100%.

The output of the processing section 10 becomes 100%, and the output of the adder 11 also becomes 10%. Now, looking at the relationship between the input angular velocity and the output of the adder 11, when the input angular velocity is 50%, that is, the angular velocity at which the phase difference is 45°, the output of the adder 11 is at its maximum, about 140%. Become. It can be seen that if there is no failure as described above, the output of the adder 11 will be in the range of 100% to 140% no matter what the input angular velocity is. Therefore, by setting the lower limit value of the determination level of the failure determination unit 12 to, for example, 90% and the upper limit value to, for example, 150%, it can be seen that when there is no failure, the failure determination unit 12 will not output any output at all, indicating that there is no failure. .

However, a failure occurs, and the output of the adder 11 is incorrect, or a part of the optical system is broken, or other electric circuits other than the processing section 10, adder 11, failure determination section 12, and display section 13 If a part of the adder 11 fails and no longer outputs output, or furthermore, if the optical modulator 4 does not operate, the output of the adder 11 will be close to 0% except under special conditions, and the failure determination unit 12 becomes below the lower limit value, it is determined that there is a failure and output B is output, and at the same time the failure is displayed on the display unit 13. Here, the special condition is a case where the input angular velocity is 0% and the synchronous detector 8 has failed, or a case where the input angular velocity is 100% and the synchronous detector 9 has failed. In such a case, the output of the adder 11 will be 100% even though there is a failure, and it cannot be determined that there is a failure. Next, to explain a case where the output of the coherent light source 1 increases significantly, the output of the adder 11 increases and exceeds the upper limit of the failure determiner 12, and it is determined that there is a failure and outputs B. At the same time, a failure message is displayed on the display section 13.

That is, since the synchronous detectors 8 and 9 can be shared as part of the basic configuration of the modulating optical fiber gyro, the configuration is simplified.

The present invention can be applied not only to the illustrated phase modulation type optical fiber gyro but also to almost any type of gyro that performs some kind of modulation using an alternating current signal. For example, in a frequency modulation type optical fiber gyro, it is sufficient to add an AC detection means consisting of a bypass filter and an aftereffect rectifier, a failure determination section, and a display section, and almost the same effect can be obtained. In addition, in the illustrated embodiment, when the processing unit 10 has surplus capacity, the signal processing operation is performed in the adder 11 that converts into an absolute value and adds it, and the failure determination unit 12 that determines the presence or absence of a failure based on the magnitude of the input level. If the processing section 10 performs this, the configuration becomes even simpler.

〔Effect of the invention〕

As described above, the present invention provides a modulation type optical fiber gyro that self-diagnoses the presence or absence of a failure and prevents continued erroneous output since it is provided with a failure detector.

[Brief explanation of the drawing]

The drawing is a block diagram of a modulating optical fiber gyro according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Coherence light source, 2... Optical coupler, 3... Optical fiber loop, 4... Optical modulator, 5... Photoelectric conversion part, 8, 9... Synchronous detector, 11 ... Adder, 12.
. . . Failure determination section, 13 . . . Display section, 14 . . . AC detection stage.

Claims (1)

[Claims] 1. In a modulation type optical fiber gyro having at least one optical modulator, AC detection means for detecting an AC component related to the driving frequency of the optical modulator in the optical output of the optical system. A modulation method characterized in that a failure detector is constituted of: a failure determination section that determines the presence or absence of a failure from a value detected by the AC detection means; and a display section that displays the determination result of the failure determination section. fiber optic gyro. 2. The modulated light according to claim 1, wherein the alternating current detection means comprises a plurality of synchronous detectors and an adder that adds the outputs of the synchronous detectors. fiber gyro.