KR101355534B1 - System and method for improving dead-zone in the interferometric fiber-optic gyroscope due to the imperfect characteristics of the optical components - Google Patents

Abstract

The present invention relates to a system and a method for enhancing a dead zone in a fiber-optic gyroscope caused by the limited performance characteristics of optical elements composing a fiber-optic gyroscope and, more particularly, to a system and a method for enhancing a dead zone in a fiber-optic gyroscope by identifying direct optical elements with distorted optical phase modulation characteristics, selecting eligible direct optical elements through the identification, and controlling the output intensity of interference signals through an optical attenuator. The present invention can enhance a dead zone in a fiber-optic gyroscope caused by the limited performance characteristics of the optical elements composing the fiber-optic gyroscope by identifying the direct optical elements with the distorted optical phase modulation characteristics, selecting the eligible direct optical elements through the identification, and controlling the output of the interference signals through pump LD driving current and the optical attenuator. Thus, the present invention can control the characteristics of an optical part for removing the dead zone. [Reference numerals] (11) Optical fiber light source; (12) Light coupler; (13) Direct optical element; (14) Optical fiber ring; (15) Detector; (16) Closed circuit controller

Description

System and method for improving dead-zone in the interferometric fiber-optic gyroscope due to the imperfect characteristics of the optical components}

The present invention relates to a system and method for improving the characteristics of an optical fiber gyro insensitive region that may occur due to limited performance characteristics of an optical fiber gyro constituting optical device, and more particularly, a coherence call of an optical fiber light source pump LD (Laser Diode). Coherence Collapse Mode A system for optimizing the electrical state of a closed loop controller for removing an insensitive region regardless of the current conditions and / or the magnitude of various optical losses occurring in the interferometer.

In addition, the present invention is to identify whether or not having a dangerous level of optical phase modulation distortion characteristics causing a dead zone in a wide temperature range, by selecting a qualified integrated optical device through this applied to a closed-loop optical fiber gyro, integrated optical device The present invention relates to a method for removing in advance an insensitive region caused by the optical phase modulation distortion characteristic of the circuit.

Dead zone is a zone that shows zero output without detecting rotation at low input angular velocity. In general, the main cause of insensitive region in closed-loop fiber optic gyro using the Serrodyne modulation and modulation technique is known as electrical cross-coupling between the vertical dyne modulation signal and the photo detector signal. GA Pavlath, "Clsoed-loop fiber optic Gyros," 20 ^th Anniversary Conference, SPIE, Vol. 2837, 46-60 (1996).

When such electrical cross-coupling occurs, this causes a bias error in the gyro output, and for a value lower than the bias error caused by the input angular velocity magnitude, the gyro output value does not give a correct value and converges to zero.

In addition, when distortion occurs in the modulation characteristics of the optical phase modulator for modulating the phase of the light according to the applied electrical modulation signal, it may cause an effect similar to the above electrical cross-linking, thereby resulting in a gyro insensitive region.

Therefore, in order to fundamentally solve the insensitive region, it is necessary to prevent the electrical cross-linking occurring between the modulation signal and the photo detector signal and to remove the distortion of the modulation characteristic of the optical phase modulator.

However, insensitive areas can also be caused by very small electrical cross-coupling, usually a few tens of ppm or less of the modulation signal size, so that no matter how well designed the electronic circuit is, it completely blocks the various electrical cross-link paths of the closed-loop controller formed through ground. There is a very difficult aspect to do this in reality.

In addition, the problem of distortion of the modulation characteristics of the optical phase modulator also has a lot of difficulties to solve the fundamental problem in terms of device. Modulation characteristics of the optical phase modulator are difficult to evaluate at the device level, and even if evaluation is difficult, it is difficult to clarify how the distortion characteristics of the modulation characteristics can affect the generation of the insensitive region. .

In order to solve the problems caused by the electrical cross-coupling, a method of minimizing the insensitive region by using a pulse dithering technique has been conventionally used. (GA Pavlath, "Clsoed-loop fiber optic Gyros," 20 ^th Anniversary Conference, SPIE, Vol. 2837, 46-60 (1996).

However, even if the pulse dithering technique is applied, it is difficult to improve the dead zone when the closed loop controller forms an electrical path that causes a certain level of electrical crosslinking. This is because in the above environment, another secondary electrical crosslinking effect may be generated by the pulse dithering technique.

Therefore, in order to achieve the improvement effect by the pulse dithering technique, it is necessary to first optimize the electrical state such as the frequency characteristic and the control characteristic of the signal inside the closed loop controller.

The most common and powerful means of optimizing the electrical state of a closed circuit controller is to vary the circuit gain and adjust it to maximize the improvement effect of the pulse dithering technique.

However, such a method can be applied when the light intensity of the optical fiber gyro interference signal identified in the photo detector can be controlled within a specific range. When a light output over a certain range is applied to the closed-loop controller input, the space for adjusting the circuit gain value is reduced, which directly leads to a problem of difficulty in optimizing the electrical state of the closed-loop controller.

Also, aside from the secondary electrical cross-coupling effect caused by the pulse dithering technique, controlling the light intensity of the interference signal within a certain range is still an important part to improve the occurrence of insensitive region caused by the electrical cross-coupling. Works. This is because when a large intensity light output of a certain level or more is applied to the closed-loop controller input, relatively larger electrical crosslinks can be caused in terms of processing a large magnitude of an electrical signal.

As a result, in order to optimize the electrical state of the closed-loop controller to remove the insensitive region, regardless of whether the pulse dithering technique is applied, the optical intensity of the optical fiber gyro interference signal identified by the optical detector must be controlled within a specific range. But this too is not easy.

This is because in many cases, the optical loss generated inside the interferometer of the optical fiber gyro is not constant and shows different characteristics depending on the characteristics of the constituent optical elements and the manufacturing state of the interferometer.

Although the light intensity of the interference signal can be adjusted by controlling the current value of the pump LD driving the optical fiber light source, this is also not practically easy. To realize the stable light source required for the fiber optic gyro, the pump LD must be operated in coherence collapsing mode, because the pump LD must be operated only above a certain current to satisfy this coherence collapsing mode. 2.T. Heil, I. Fischer, and W. Elsasser, "Influence of amplitude-phase coupling on the dynamics of semiconductor lasers subject to optical feedback", Phys. Rev. A, Gen. Phys., Vol. 60, pp 634-641 (1999).

The current conditions satisfying the Coherence Collapse mode may be different for each pump LD manufactured, which affects the control of the light intensity of the optical fiber gyro interference signal within a specific range.

In addition to the coherence collapse mode problem, when implementing a gyro with one rotation sensing axis, it is possible to apply a method of adjusting the light intensity of the interference signal by simply controlling the current value of the pump LD. At the time, it is difficult to control the light intensity of all interfering signals within a certain range because of the light loss inside the interferometer, which may be different for each axis.

Moreover, the light intensity of different interference signals, although small in size, can cause electrical cross-coupling between axes due to unbalance of signal size in electronic signal processing in closed-loop controllers.

On the other hand, the problem caused by the modulation characteristic distortion of the optical phase modulator is a problem that cannot be solved even by using a pulse dithering technique and a method of controlling the interference signal light intensity within a specific range.

In order to solve such a problem, it is necessary to identify the distortion characteristic of the optical phase modulator at the device level and to fundamentally eliminate the influence thereof. In the past, the optical fiber gyro was fabricated using the optical phase modulator as an evaluation target, and the optical fiber gyro was used to determine the presence of insensitive areas at the level of the optical fiber gyro using a rate table. .

However, this method is meaningful when one of the causes of the distortion of the modulation characteristics of the optical phase modulator is required and many tests are not required for the evaluation. In general, when an integrated optical device using the excellent electro-optic effect of LiNbO ₃ is used as an optical phase modulator, the optical phase modulation characteristic distortion phenomenon is a local charge or mobile type that can be formed near the electrodes and optical waveguides of the integrated optical device. These charges are generated by mobile charges. These charges can be caused by various causes such as organic and inorganic pollutants or the synthesis of unwanted chemicals generated in the manufacturing process. Wang and J. Wang, "Study of modulation phase drift in an interferometric fiber optic gyroscope", Opt. Eng., Vol. 49 (11), 114401 (2010). And 4. DS Kim, WS Yang, WK Kim, HY Lee, H. Kim, and DH Yoon, "DC-drift suppression of Ti: LiNbO ₃ waveguide chip by minimizing the contamination in oxide buffer layer", J. Crystal Growth vol. 288, pp. 188-191 (2006). Reference)

However, in order to grasp the characteristics of the components, the conventional method has a disadvantage in that it takes a lot of time and money in terms of development because of the fact that a fiber optic gyro system is evaluated at a rate that can be specially evaluated.

In addition, when the closed-loop controller is not electrically optimized, it may be determined whether the optical fiber gyro-sensitive region is caused by distortion of the modulation characteristics of the optical phase modulator or by electrical cross-coupling between the modulation signal and the photo detector. There was no problem.

1. Korean Patent Publication No. 10-2012-0010055 2. Korean Patent Publication No. 10-2010-0118872

G. A. Pavlath, "Clsoed-loop fiber optic Gyros," 20th Anniversary Conference, SPIE, Vol. 2837, 46-60 (1996). 2. T. Heil, I. Fischer, and W. Elsasser, "Influence of amplitude-phase coupling on the dynamics of semiconductor lasers subject to optical feedback", Phys. Rev. A, Gen. Phys., Vol. 60, pp. 634-641 (1999). 3. W. Wang and J. Wang, "Study of modulation phase drift in an interferometric fiber optic gyroscope", Opt. Eng., Vol. 49 (11), 114401 (2010). 4. D. S. Kim, W. S. Yang, W. K. Kim, H. Y. Lee, H. Kim, and D. H. Yoon, "DC-drift suppression of Ti: LiNbO3 waveguide chip by minimizing the contamination in oxide buffer layer", J. Crystal Growth vol. 288, pp. 188-191 (2006).

As described above, the generation of the optical fiber gyro insensitive region is due to the electrical crosslinking caused by the modulation signal and the photodetector, but the effect of the electrical crosslinking is because optical elements constituting the optical fiber gyro have limited performance characteristics. There is an aspect that prevents the effective removal of.

The present invention has been proposed to solve the problems according to the prior art, which is due to the limitations of optical fiber gyro constituting optical elements such as distortion of modulation characteristics of optical phase modulator and difficulty of control within a certain range of interference signal light intensity. The purpose is to improve the characteristics of insensitive areas that may occur.

The present invention provides a system for improving the insensitive region generation characteristic by the optical element limiting element of the optical fiber gyro in order to achieve the object raised above.

The insensitive region generation characteristic improvement system includes an optical fiber light source; A first optical attenuator for fixing or varying light output from the optical fiber light source; An integrated optical device for separating and outputting fixed or variable light into two; An optical fiber ring made of polarization-maintaining optical fiber, one of the separated output light waveguides in a clockwise direction and the other waveguide in a counterclockwise direction; An optical combiner for optically coupling the interfering signal, wherein the two guided lights are interfered by the integrated optical element; A second optical attenuator for fixing or varying the optically coupled interference signal; And a photo detector for detecting the fixed or variable interference signal by the amount of current.

The apparatus may further include a closed circuit controller configured to output the interference signal detected by the photo detector as a rotation signal by using a Serrodyne modulation and demodulation scheme.

In addition, the closed-loop controller may be applied to the integrated optical device a controlled longitudinal dyne modulated signal to reduce the interference signal changed by the optical phase difference generated in the interferometer to the initial state to which the optical phase difference is not applied. Can be.

Further, the optical fiber light source sets the pump LD driving current value to a specific level or more, and adjusts the pump LD driving current, the first optical attenuator, and the second optical attenuator to coherence colleps (Coherence). Collapse) may be driven in the mode.

The optical fiber light source may further include an optical fiber Bragg grating for driving the pump LD in the coherence collapse mode.

In addition, the first optical attenuator or the second optical attenuator may be selectively applied according to the number of rotation sensing shafts.

In addition, the integrated optical device may be a multifunctional optical device that simultaneously performs the role of a light splitter and a polarizer.

On the other hand, another embodiment of the present invention includes a reset output signal applying step in which the longitudinal dyne signal generator applies a reset output signal for resetting to the integrated optical device; A reset step of resetting the integrated optical device according to an applied reset output signal; Detecting a maximum value of the first interference signal at the last time point at which the first modulation period ends by resetting; A second interference signal maximum value detection step of detecting a second interference signal maximum value at a time point when the second modulation period starts; A ratio value calculating step of calculating a ratio value with respect to the detected first and second interference signal maximum values; And displaying the degree of optical phase modulation distortion of the integrated optical device by using the calculated ratio value.

The first modulation period may be a 0.5A modulation period, and the second modulation period may be a 1.5A modulation period.

Here, the reset output signal may be characterized by having a 2A reset range and a constant slope.

According to the present invention constituted as described above, by identifying the integrated optical device having the distorted optical phase modulation characteristics, the selection of qualified integrated optical device and the control of the interference signal output through the pump LD drive current and the optical attenuator, It is possible to improve the characteristics of the optical fiber gyro insensitive region that may occur due to the limited performance characteristics of the constituent optical elements. Therefore, the optical part characteristic control for removing the insensitive region can be realized through the present invention.

In particular, the optical phase modulation characteristic of the integrated optical device may be gradually distorted as the temperature changes even though the ideal level is maintained at room temperature. This immediately leads to a temperature-dependent optical fiber gyro insensitive region generation characteristic, according to the present invention, by solving the optical phase modulation distortion characteristic evaluation technique can be solved such problems in the presence of a wide temperature range.

In addition, the optical loss occurring inside the interferometer tends to be changed within a certain level according to the fabrication state of the constituent optical device. Can be removed effectively.

1 is a configuration diagram of a closed circuit optical fiber gyro 10 to which an optical attenuator is applied according to an embodiment of the present invention.
2 is a block diagram of an integrated optical device optical phase modulation characteristic test according to an embodiment of the present invention.
3 is a graph showing a Sagnac Intererometer output signal according to the optical phase modulation characteristic described in an embodiment of the present invention.
4 is a flowchart illustrating a process of quantitatively evaluating optical phase modulation distortion characteristics of an integrated optical device according to an exemplary embodiment of the present disclosure.
FIG. 5 is a graph showing a correlation of occurrence of an insensitive region according to optical phase modulation characteristics that vary depending on a temperature described in an embodiment of the present invention. FIG.
Figure 6 is a graph showing the insensitive region characteristics according to whether the optical attenuator described in an embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for similar elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The term "and / or" includes any combination of a plurality of related listed items or any of a plurality of related listed items.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Should not.

Hereinafter, with reference to the accompanying drawings will be described in detail a system and method for improving the insensitive region generation characteristics due to the optical element limiting element of the optical fiber gyro according to an embodiment of the present invention.

Means for implementing one embodiment of the present invention can be summarized in two broad. First of all, the intensity of the interference signal obtained by the optical detector by applying a fixed or variable optical attenuator to the optical fiber optical output terminal or the optical detector input terminal in an environment in which an insensitive region is not generated by the optical phase modulation characteristic of the integrated optical device. This enables the control to be performed, thereby optimizing the electrical state of the closed-loop controller for eliminating dead zones regardless of the coherence collapse mode current condition of the fiber optic light source pump LD and the amount of light loss generated inside the interferometer. It is. A diagram showing this is shown in Fig.

Second, it is necessary to distinguish whether the cause of the insensitive region is caused by electrical crosslinking or by distortion of optical phase modulation. Therefore, there is a need for a technique capable of evaluating optical phase modulation distortion without using a closed circuit controller.

Such an evaluation technique should be able to quantitatively evaluate the optical phase modulation distortion characteristics and to relatively predict the degree to which the optical phase modulation distortion characteristics contribute to the generation of an insensitive region through the evaluated results.

Whether or not the evaluated integrated optical device has an optical phase modulation distortion characteristic of a dangerous level causing an insensitive region is identified at a wide temperature range, and thus, a qualified integrated optical device is selected. Finally, by applying the selected integrated optical device to the closed-loop optical fiber gyro, the generation of insensitive region due to the optical phase modulation distortion characteristics of the integrated optical device is eliminated in advance. Figures showing this are shown in Figures 2-4.

First, FIG. 1 is a schematic diagram of a closed circuit optical fiber gyro 10 to which an optical attenuator according to an embodiment of the present invention is applied. Before describing FIG. 1, as mentioned above, an embodiment of the present invention relates to a technique for improving an optical fiber gyro insensitive region characteristic that may occur due to limited performance characteristics of an optical fiber gyro constituting optical device. The integrated optical device having the optical phase modulation characteristic is identified at a wide temperature range, and the integrated optical device is selected through this, and the output of the interference signal is controlled through the pump LD driving current and the optical attenuator.

Dead zone is a zone that shows zero output without detecting rotation at low input angular velocity. In general, the main cause of the insensitive region in the closed-loop optical fiber gyro using the Serrodyne modulation and demodulation technique is known as electrical cross-coupling between the vertical dyne modulation signal and the photo detector signal.

With reference to FIG. 1, in accordance with an aspect in accordance with one embodiment of the present invention, FIG. 1 shows a schematic diagram of a closed-loop optical fiber gyro 10 to which optical attenuators 17 and 18 are applied. The closed-loop optical fiber gyro 10 is configured as follows: an optical fiber light source 11, an optical coupler 12, an integrated optical element 13, an optical fiber ring 14, an optical detector 15, and a Serrodyne Generator. ) A second optical light positioned at an input of a closed circuit controller 16 to which a modulation / modulation technique is applied, a first optical attenuator 17 located at an output end of an optical fiber light source 11 for controlling interference signal strength, and an optical detector 15 for controlling interference signal strength. Attenuator 18. The first and second optical attenuators 17 and 18 may be fixed or variable optical attenuators, and the optical coupler may be used as the optical attenuator.

The optical fiber light source 11 receives the output of a laser diode (LD) as pump light and generates C-band band light through an Erbium Doped Fiber (EDF) and a Wavelength Division Multiplexer (WDM). Let's do it.

A fiber Bragg grating (FBG) is applied to the pump LD output stage in order to drive the pump LD in the Coherence Collapse mode of operation, which generates stable light at temperature changes.

The light generated from the optical fiber light source 11 and having a very stable output in frequency and light intensity sequentially reaches the integrated optical element 13 through the first optical attenuator 17 and the optical coupler 12.

Since the light is divided into two branches through the integrated optical element 13, one wave guides in the clockwise direction to the optical fiber ring 14 made of polarization maintaining optical fiber and the other wave guides in the counterclockwise direction.

The integrated optical element 13 is formed to apply a phase modulated signal to the light so that the phase of the light is modulated, and at the same time, the waveguide is formed in a Y-shape by a quantum exchange technique, thereby simultaneously serving as an optical splitter and a polarizer. to be.

The two lights that guided the optical fiber ring 14 are again interfered through the integrated optical element 13 and the interference signal is passed through the optical coupler 12 and the second optical attenuator 18 to the amount of current in the photo detector 15. Is detected.

The interference signal detected by the photo detector 15 is output as a rotation signal through the closed circuit controller 16 which performs the longitudinal dyne modulation and demodulation technique. At the same time, the closed circuit controller 16 applies a controlled longitudinal dyne modulation signal to reduce the interference changed by the optical phase difference generated inside the interferometer to the initial state where the optical phase difference is not applied.

By properly adjusting the pump LD driving current and / or the optical attenuators 17 and 18 of the optical fiber light source 11, the optical fiber light source 11 is driven in the coherence collapse mode while at the same time the desired level of interference signal light intensity is detected by the optical detector 15. Can be identified at

The fixed or variable optical attenuators 17 and 18 may be selectively applied according to the number of rotation sensing axes. When there is only one rotation sensing shaft, the first and second optical attenuators 17 and 18 may be applied to only one of the output terminal of the optical fiber light source 11 and the input terminal of the photo detector 15.

When there are a plurality of rotation sensing axes, the first and second optical attenuators 17 and 18 may be selectively applied depending on whether there is a difference in the amount of light loss occurring inside all interferometers to be handled.

When there is no significant difference in the amount of light loss occurring inside all the interferometers handled, only one first optical attenuator 17 located at the output end of the optical fiber light source 11 is used, and the output is sensed by a plurality of rotation sensors through the optical splitter. It is efficient to use a distribution method on the shaft.

If there is a large difference in the amount of light loss occurring inside all interferometers handled, the photodetector 15 for each rotation sensing axis without using the first optical attenuator 17 located at the output of the optical fiber light source 11. By applying a second optical attenuator 18 located at the input terminal of the) to equalize the magnitude of the interference signal light intensity identified in each axis.

The optical coupler 12 distributes light propagated along an optical fiber (or optical waveguide) to two or more optical fibers, or conversely, light having a function of combining light propagated through two or more optical fibers into one optical fiber. Passive device. 2x2, 4x4, 8x8, etc. are used as the form of the optical coupler 12, but one embodiment of the present invention uses a 2x2 optical coupler.

On the other hand, as a second means for implementing an embodiment of the present invention Figure 2 corresponds to the integrated optical device optical phase modulation characteristics test configuration diagram according to an embodiment of the present invention. Referring to FIG. 2, FIG. 2 is a diagram illustrating an optical phase modulation characteristic test configuration of an integrated optical device 13, and includes a fiber optic gyro optical unit 21 and a vertical dyne signal generator having a 2A reset range and a constant slope. The concept of evaluation using 22) is shown.

The optical fiber gyro optical unit 21 is the same as the configuration using 11 to 15 shown in Fig. 1, the integrated optical element 13 as a component is the evaluation target. An output from the vertical dyne signal generator 22 having a 2 A reset range is applied to the electrodes of the integrated optical element 13 and the oscilloscope 23 confirms the resulting interferometer output signal shape.

3 is a Sagnac Intererometer output signal according to the optical phase modulation characteristic described in an embodiment of the present invention. Referring to FIG. 3, the test results of FIG. 2 according to the optical phase modulation characteristics of the integrated optical device (13 of FIG. 2) are shown.

When the integrated optical device optical phase modulation characteristic is good, the Shagnac interferometer output signal takes the form of FIG. 3A. On the contrary, when the integrated optical device optical phase modulation characteristic is distorted to cause an insensitive region when applied to the closed-loop optical fiber gyro (10 in FIG. 1), the chagnac interferometer output signal has a shape as shown in FIG. 3B.

In the case of having the ideal optical phase modulation characteristic, when the vertical dyne signal 31 having the 2A reset is applied to the integrated optical device electrode, the interferometer output form identified by the oscilloscope (23 in FIG. 2) is 0.5A modulated signal section 33 and 1.5. There is no difference in the A modulation signal section 34.

In this respect, the interferometer output form 32 shown in FIG. 3A is also hardly considered to have ideal optical phase modulation characteristics. However, in this case, since there is no significant difference in the output form in the two modulation signal intervals, it is possible to effectively remove the influence of the optical phase modulation characteristic that is not ideal when the insensitive region improvement techniques such as the pulse dithering technique are applied.

On the other hand, the interferometer output form 35 of FIG. 3B not only shows a remarkable difference between the two modulated signal sections, but also has a form in which the interfering signal output changes over time even within the same section. This shows a serious problem with the output of the interference signal.

In the presence of such a large error component, no matter how well the inductive region improvement techniques such as the pulse dithering technique are applied, the occurrence of the insensitive region cannot be avoided.

A flow chart showing a method of quantitatively evaluating optical phase modulation distortion characteristics of an integrated optical device from the test results of FIGS. 3A and 3B is shown in FIG. 4. FIG. 4 is a flowchart illustrating a process of quantitatively evaluating optical phase modulation distortion characteristics of an integrated optical device (13 of FIG. 2) according to an exemplary embodiment.

Referring to FIG. 4, when the vertical dyne signal generator 22 of FIG. 2 applies a reset output signal for reset to the integrated optical element 13 of FIG. 2, the reset is performed (step S400).

This reset detects the maximum value of the first interference signal at the end of the first modulation period (for example, 0.5 A modulation period), and immediately follows the second modulation period (for example, The second interference signal maximum value at the time when the 1.5A modulation period is started is detected (steps S410 and S420).

If the maximum values of the first and second interference signals are detected, a ratio value for them is calculated (step S430).

The calculated ratio value is used as a measure of the degree of optical phase modulation distortion of the integrated optical element 13 (step S440).

The integrated optical device optical phase modulation distortion characteristic is most noticeable when the electrical perturbation of the 0.5 A modulation section is encountered and suddenly encounters the 1.5 A modulation section which is relatively high.

It is for this reason that a vertical dyne signal having a reset (i.e., a reset output signal) is used to evaluate the optical phase modulation distortion characteristics of the integrated optical element. In an embodiment of the present invention, a vertical dyne signal having a 2A reset range is used, but it is also possible to set a reset range of 2A or more and evaluate an integrated optical device to clearly understand the degree of response to large perturbations.

FIG. 5 is a graph showing a correlation of occurrence of an insensitive region according to optical phase modulation characteristics that change depending on a temperature described in an embodiment of the present invention. Referring to FIG. 5, a closed circuit optical fiber gyro is formed by using an integrated optical device whose characteristics as shown in FIG. 3b are identified from a high temperature of 40 ^° C. or higher. .

Referring to Figure 5, at room temperature (25 ^° C) is shown the result of detecting the Earth's rotational angular velocity of about 10 deg / hr normally. On the other hand, when the temperature rises from 30 ^o C or higher to a high temperature, the gyro output gradually decreases, and from 40 ^o C or higher, only a zero output value occurs.

That is, it is expected that the non-sensitive region is at least 10 deg / hr at a high temperature higher than 40 ^° C. The result of FIG. 5 shows the correlation of the insensitive region generation according to the integrated optical device optical phase modulation characteristics, and the evaluation of the integrated optical device optical phase modulation distortion characteristics according to an embodiment of the present invention is performed over the entire optical fiber gyro operating temperature range. It can be said that the exemplary embodiment suggests that it needs to be considered.

6 is a graph showing insensitive region characteristics depending on whether an optical attenuator described in an embodiment of the present invention is applied. That is, FIG. 6 compares the results of the optical fiber gyro insensitive region generation according to the presence or absence of an optical attenuator in an environment in which the insensitive region generation due to the optical phase modulation characteristic of the integrated optical device can be excluded.

In other words, Figure 6a is a result in a situation that the optical attenuator (17, 18 of Figure 1) presented in one embodiment of the present invention is not applied, Figure 6b is a situation in which the optical attenuator proposed in the present invention is applied The result is.

In the situation where the optical attenuator is not applied, the electrical state of the closed circuit controller cannot be optimized, resulting in the generation of an insensitive area, while in the situation where the optical attenuator is applied, the interference can be optimized to optimize the electrical state of the closed circuit controller (16 in FIG. 1). By controlling the signal light output to the desired state through the optical attenuators 17 and 18, it is shown that the insensitive region can be effectively removed.

As described above, an embodiment of the present invention provides a method of identifying an integrated optical device having a distorted optical phase modulation characteristic (13 in FIG. 1), selecting a suitable integrated optical device through the optical attenuator, and controlling an interference signal output strength through an optical attenuator. It is characterized in that to improve the characteristics of the optical fiber gyro insensitive region that may occur due to the limited performance characteristics of the optical device gyro constituting the optical element.

11.Fiber Optic Light Source
12 ... optical coupler
13. Integrated optical element
14 ... fiber optic loop
15 ... light detector
16 ... Closed Circuit Controller
17.First optical attenuator
18 ... second optical attenuator
21.Fiber Optic Gyro Optics
22.Vertical Dine Signal Generator
23.Oscilloscope
31.Vertical Dine Signal
32.Shagnac interferometer output form
33 first modulation signal interval
34 second modulation signal interval
35.Shagnac interferometer output form

Claims (10)

Optical fiber light source;
A first optical attenuator for fixing or varying light output from the optical fiber light source;
An integrated optical device for separating and outputting fixed or variable light into two;
An optical fiber ring made of polarization-maintaining optical fiber, one of the separated output light waveguides in a clockwise direction and the other waveguide in a counterclockwise direction;
An optical combiner for optically coupling the interfering signal, wherein the two guided lights are interfered by the integrated optical element;
A second optical attenuator for fixing or varying the optically coupled interference signal; And
Including a photo detector for detecting a fixed or variable interference signal in an amount of current,
The optical fiber light source sets the pump LD driving current value to a specific level or higher, and adjusts the pump LD driving current, the first optical attenuator, and the second optical attenuator to coherence collapse. The system for improving the insensitive region generation characteristic by the optical element limiting element of the optical fiber gyro, characterized in that driven in the mode.
The method of claim 1,
Characterized in that the non-sensitive region generated by the optical element limiting element of the optical fiber gyro further comprises a closed circuit controller for outputting the interference signal detected by the optical detector as a rotation signal by using the Serrodyne modulation and demodulation method Improvement system. 3. The method of claim 2,
The closed-loop controller applies a controlled longitudinal dyne modulation signal to the integrated optical device to reduce the interference signal changed by the optical phase difference inside the interferometer to the initial state where the optical phase difference is not applied. Improvement system of insensitive region generation characteristic by optical element limiting element.
delete The method of claim 1,
The optical fiber light source further comprises an optical fiber Bragg grating for driving the pump LD in the Coherence Collapse mode (Coherence Collapse), characterized in that the system for improving the insensitive region generation characteristics by the optical element limiting element of the optical fiber gyro.
The method of claim 1,
The first optical attenuator or the second optical attenuator is selectively applied according to the number of the rotation sensing axis, characterized in that the system for improving the insensitivity region generation characteristic by the optical element limiting element of the optical fiber gyro.
The method of claim 1,
The integrated optical device is a multifunction optical device that performs both the optical splitter and the polarizer at the same time, characterized in that the system for improving the insensitive region generation characteristics by the optical element limiting element of the optical fiber gyro.
A reset output signal applying step in which the vertical dyne signal generator applies a reset output signal for resetting to the integrated optical device;
A reset step of resetting the integrated optical device according to an applied reset output signal;
Detecting a maximum value of the first interference signal at the last time point at which the first modulation period ends by resetting;
A second interference signal maximum value detection step of detecting a second interference signal maximum value at a time point when the second modulation period starts;
A ratio value calculating step of calculating a ratio value with respect to the detected first and second interference signal maximum values; And
Displaying the degree of optical phase modulation distortion of the integrated optical device using the calculated ratio value
Method for improving the generation of insensitive region by the optical element limiting element of the optical fiber gyro characterized in that it comprises a.
The method of claim 8,
When the reset range is 2A, the first modulation section becomes the 0.5A modulation section, and the second modulation section becomes the 1.5A modulation section. Way.
The method of claim 8,
And the reset output signal has a reset range and a constant slope of 2A or more.

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