This paper reviews the basics of the interferometric fiber- optic gyroscope: fundamental principle based on Sagnac effect, importance of reciprocity and single-mode propagation, analysis of coherence and polarization problems, signal processing techniques. It also describes the technological progress of guided-wave components. Finally, recent trends like multi-axis configurations and rare-earth doped fiber source are presented.

The open-loop I-FOG has been applied to a number of industrial and consumer applications such as vehicle navigation systems, attitude control systems of unmanned agricultural helicopter, pipe-mapping systems, north-finding systems, etc. Its mass production technology is also described.

Recent researches for future evolution of fiber optic gyros are discussed. Research items to improve the I-FOG functions, concerning light-source stability, temperature change induced drift, and cost reduction, are reviewed at first. R-FOG and B-FOG researches are also discussed.

Research and development of fiber optic gyros began in the mid 1 970s and focused on improving the gyro's sensitivity to rotation and reducing noise. Next, bias performance was addressed. By the early 1980s, fiber gyros were achieving bias errors of 0.01 O/ in a laboratory environment. Scale factor performance was initially addressed at McDonnell Douglasi in the late 1 970s by the use of a closed-loop fiber gyro which employed acousto-optic frequency shifters. Good performance was achieved but this approach was not productionized. In the mid 1980s, Thomson CSF developed a fiber gyro which used a double closed-loop technique employing a digital phase ramp and an electro-optic phase modulator2. Derivatives of this approach have been adopted by most gyro producers in the world. This technique has enabled fiber gyros to have high scale factor linearity and has significantly improved scale factor stability and repeatability. Today closed-loop fiber optic gyros using derivatives of this technique are in production for many tactical applications3 . These include tactical missiles, smart bombs, and attitude and heading reference systems (AHRS) and require gyro bias performance of 1 to 1 0 O/ and gyro scale factor performance of 1 00 to 1 000 ppm. Closed-loop fiber gyros using derivatives of this technique are presently in development for future inertial navigation systems4 (INS) which require bias performance in the 0.00 1 to 0.01 0/hr and scale factor performance in the 5 to 50 ppm range. This paper will examine how this double closed-loop, digital phase ramp technique functions. An error source unique to this type of closed-loop gyro, the deadband error, will be examined along with a technique for eliminating it.

Fiber-optic gyroscopes (FOGs) are under development at Honeywell as the primary next generation inertial sensor. The open-loop FOG technology has been successfully transitioned to production for attitude heading reference systems and the results of this effort are reported. New developments in closed-loop FOG technology aimed at high performance space applications and at navigation grade aviation applications, are underway. In the former case, results on a high precision FOG are reported. In the latter case, special emphasis is placed on improvements of depolarized FOG technology, which promises to produce a low cost navigation grade sensor.

IFOG has entered into the practical application phase for widely inertial equipments of aerospace market to industrial equipments of commercial market. This paper describes the examples of IFOG products and its applications at Japan Aviation Electronics.

Honeywell, under contract to the US Air Force, has developed a 25 cubic-inch IFOG IMU brassboard which demonstrated performance of < deg/hr bias stability, < 0.05 deg/(root) hr random noise and < 250 ppm scale factor accuracy over the full military temperature range. To overcome the size constraint of 25 cubic-inch, the three-axis IFOG optical cluster was configured with the minimum IMU configuration having only eight optical components. Special loop-closure signal processing was developed to accommodate all three- axis sensor electronics within a single 3.4-inch electronic board. To achieve the IMU cost target of < 6000 dollars, the design utilizes a very lowest cost optical components such as an 830nm light source along with a 1300 nm single- mode fiber sensing coil. Further cost reduction was realized through the robust design which provides very relaxed gyro assembly tolerances. The 25 cubic-inch IFOG IMU will have sufficient performance, small size, ruggedness for high-g launch, and low unit production cost to be suitable for use in a wide variety of tactical weapon systems.

We present the design of a commercial available single axis gyro, which has an accuracy of better than 36 degrees/hr. The key features are small size, single 5 volt power, low power consumption and low cost. The gyro has versatile output interfaces including analog output. The product name of the gyro is (mu) FORS 36.

In the past, a common way to develop systems was to build prototypes and test these in the laboratory until all bugs were fixed. The final system was developed and released for production in at least another one additional design iteration. This way is no longer feasible in modern systems. It is too time consuming and for some systems not possible at all. The complex behavior of these systems must be simulated and alternatives must be proved to find the best solution to comply with the need of the market. This paper is showing, how LITEF was designing as ASIC for an (mu) FORS system. Simulation proved the correctness of the specification for this ASIC and the functionality of the complete system. The simulation of different design tools had to be interfaced to achieve the result. No prototype was built to prove correctness of the system idea.

Further cost reduction of the fiber optic gyroscope is necessary to meet the economic requirements of land navigation systems. We have previously concentrated on the reduction of the number of splices and component improvements in the open-loop, minimum configuration. Now we eliminate non-essential components and splices. The source- detector coupler is not part of the Sagnac interferometer, and serves solely to provide isolation between the broadband optical source and the photodetector. Many commercial laser diodes incorporate a back-facet photodetector to monitor laser intensity. The signal returned from the Sagnac interferometer traverses the laser, is received at this photodetector, and can be distinguished from the laser signal by the bias modulation. Configuring a gyro in this manner eliminates a directional coupler and the separate photodetector, as well as up to three fiber splices in an all-fiber gyroscope. A production, open-loop fiber optic gyroscope has been modified to demonstrate this principal. The gyroscope can be constructed with only two fiber splices and exhibits performance comparable to the conventional minimum configuration.

A spherical error probable of 4.0 meters was demonstrated with an IFOG-based, integrated inertial measurement/global positioning system under dynamic field conditions. Less than 1.0 nautical mile per hour free inertial mode drift was also achieved with this system under laboratory-simulated test conditions. To achieve these levels of performance, IFOGs with bias uncertainties less than 0.015 deg/hr, scale factor errors less than 50 ppm and angle random walks less than 0.005 deg/(root) hr wee required. The performance of a series of six IFOGs is reported. For comparison, the performance of the same instruments measured in two demonstration GGP units is also presented. Both laboratory and field test results of the systems are discussed. The focus of the data presented is the instrument noise and the long term bias thermal model stability. The instruments and systems were developed as part of the first phase of a two phase program to create a 100 in 3 integrated GPS/INS systems with a target cost of 15K dollars (US). With the implementation of interferometric fiber optic gyro technology, integrated guidance and navigation systems are potentially very low cost with high reliability and suitability for a wide range of military and commercial applications.

An inertial measurement unit (IMU) with angular rate, angular increment and linear acceleration measurement systems for short range missile application is described. It consists of a three axis fiber optic gyroscope (FOG) cluster, three linear vibrating beam accelerometers and an electronics device for signal evaluation and data transmission via a serial transputer link. The FOG cluster is realized by means of a passive all-fiber open loop configuration. Due to the inherent optical phase shift of 3 by 3 couplers, completely passive operation near the quadrature point is achieved without the need for a non- reciprocal optical phase modulation in the fiber loop. Basing on that concept more than 50 rugged IMUs have been built for implementation into a short range air to air missile. Verification tests for flight clearance with stresses simulating air carriage and missile free flight environments have been computed. The operation under extreme vibration and shock environments without the use of vibration isolator fixings due to very tight requirements on data time delay has been demonstrated. The first telemetered missile firings have been performed successfully. The line- setup for large quantity series production is progressing. The implementation of the workstations for the integration of the IMU is finished. The production equipment for calibration and acceptance testing of IMUs in parallel allowing for a rate of more than 150 unit per month has been installed and will be operational in autumn this year.

We present a new method to multiplex multi-axis FOGs. A 2 X N coupler is used to share a light source between N Sagnac interferometers. They are all modulated with usual square wave phase modulations, but these modulations are shifted in time by (tau) /N where (tau) is the mean transit time into a coil. The total optical signal coming back from the interferometer is detected with a single photodiode and then demultiplexed. This multiplexing technique has the important advantage to yield a constant bias power even when the powers returning from the various interferometers are not balanced. The closed-loop configuration allows no crosstalk between the N axes far from the cut-off frequency.

We discuss the unique characteristics of interferometric fiber optic gyroscopes (IFOGs) and report several possible schemes for multiplexing of IFOGs. Comparison of different schemes in terms of component number, power budget, possible crosstalk sources will be presented.

Progress on the development of an ultra miniature fiber optic rate gyro is reported. A unique IFOG design implementing low cost components is presented where package volume is less than two cubic inches including electronics. This design is capable of meeting operational performance requirements over the temperature range of -57 to +71 C with electronic power limited to 3 watts. The IFOG circuit consists of an ELED source at 1.3 micrometers , a non-PM source/receiver multiplex circuit using a standard fused biconic tapered coupler, an annealed proton exchange integrated optic 'gyro chip', and a volume efficient 'racetrack' PM sensing coil configuration. Gyro electronics have been reduced to a single MCM board. A discussion of the design parameters, component requirements, and test data are presented.

The PM fiber Sagnac interferometer operated a current sensor is described. Its most serious difficulty is its high sensitivity to mechanical and thermal perturbations. An 'in- line' derivative optical circuit which solves this 'Shupe effect' error is then described.

The Sagnac interferometer may be used to support high speed secure fiber optic data links over distances of more than 10 km. This paper provides a description of the basic system and describes how it may be applied to campus and local area network applications.

This paper discusses different configurations of polarization maintaining fiber Sagnac ring strain sensors based on FMCW technology. Each sensor consists of a frequency-modulated single mode laser, a 100 meter length of single mode birefringent fiber ring and PIN photodiode detector. In each case, two opposite propagating beams in the fiber are employed to sense the variations in length due to strain, although the generation of the beat signal is different in each case. The final sensor specifications are very similar as both exhibit high resolution, large dynamic measurement range, large signal intensity, good signal contrast and long sensing fiber.

The theoretical explanation of the Sagnac effect form the point of view of special relativity states that the effect is the combined result of the Fresnel drag effect of the rotating loop medium and the movement of the loop coupler with respect to the light wave initial input position. We assembled a set-up to test the validity of this superposition model and discuss the results.

We have assembled closed loop IFOGs utilizing integrated optics. And those IFOGs wee evaluated. As a result, it was confirmed that a bias temperature compensation residual of 0.016 and a scale factor linearity of 7.1 were achieved.

This paper describes a 0.1 deg/hr fiber optic gyroscope (FOG) controlled exclusively by a high-speed digital signal processor (DSP). The sampling time of all control loops equals the transition time of the light through the sensor coil. The device uses a 500 m fiber sensor coil and operates in closed-loop mode. The control and compensation algorithms where implemented in software and are carried out by a single high-speed DSP. The processor also takes care of the communication protocol via a high-speed synchronous serial bus. This single-axis FOG was designed in a modular structure and is the basic building block for the LFK95 system; a low-cost maritime gyrocompass for commercial applications. The system also fulfills serial bus, maritime gyroscompass, modular structure.

We previously reported achievement of 0.0027 deg/rt-hr angle random walk, as well as attainment of 0.0092 deg/hr bias uncertainty, 9.2 ppm scale factor error and 0.38 arc-seconds input axis alignment error over the temperature range -55 to 71 degC under dynamic thermal environments. The gyro coil in these instruments has less than 3 inches outer diameter and less than one inch height. In this paper we report on further advances in navigation-grade IFOG technology achieved at Litton. The angle random walk has been reduced by a factor of three to 0.0009 deg/rt-hr. Bias uncertainty of 0.0081 deg/hr has been attained over the -55 to 71 degC temperature range having more stringent temperature ramps than previously reported. The gyro bias magnetic sensitivity has been reduced to 0.0002 deg/hr/gauss. This paper describes the IFOG optical architecture that utilizes a low-birefringence network and a polarization maintaining network, discusses the dominant sources of thermal and magnetically-induced bias error in the IFOG and presents the latest data from the navigation- grade IFOG.

Fiber optic gyroscopes (FOGs) are preferably driven as closed-loop controlled systems, if linearity and dynamic range are of major concern. Proper modulation of the Sagnac interferometer (SIF) feedback signal is necessary to minimize low frequency signal perturbation and to reliably detect luminance intensity in the linear regions of the sinusoidal Sagnac phase to intensity mapping. Deterministic modulation however, is accompanied by well known 'dead zones' and bias errors due to unavoidable crosstalk between the modulator and the optical detector. In the paper we propose a high precision closed-loop FOG system with deadbeat control and pseudorandom modulation of the SIF feedback signal. The random modulation principle completely eliminates 'dead zones' in the detection of small rotation rates, and bears an inherent potential for compensation and control of several error sources encountered in non-ideal systems by means of signal correlation. The principle of correlation based control is introduced in a general context and applied to a set of dedicated control loops within the proposed closed-loop FOG. Results obtained form several prototype realizations of the correlation controlled high precision FOG indicate a potential for bias error reduction by two orders of magnitude and considerable decrease in random walk.

In this paper we investigate the dependence of the bias in the interferometric fiber optic gyro versus the temperature gradient applied on the case of the sensor. Our main interest is in the coil winding pattern and in the design of the case. We describe here a method to calculate the influence of these two parameters on the temperature gradient performance. Our approach is to use a finite element model of the case and the coil. We describe then the winding pattern including the location and the length of each turn of the coil. With those data, we are able to compute the bias induced by the thermal transient effect.

Most sources of optical loss in a fiber optic gyro (FOG) depend on wavelength. Because of the broadband sources used in interferometric FOGs, these losses result in an effective shift of mean wavelength of the light producing the interference signal. For some signal processing methods, these wavelength variations produce proportional changes in the IFOG scale factor. Using well documented approximations, losses are calculated and plotted versus wavelength. A discussion of the qualitative effects on scale factor is presented and expected mean wavelength variations are computed using a representative approximation of the spectrum of a FOG source. The types of losses considered include: fiber-fiber or fiber-wave guide misalignments; microbend losses, bending losses and mode diameter mismatches. Preliminary results indicate that scale factor variations caused by such losses will contribute significantly to the total scale factor thermal sensitivity for some FOG designs. While closed loop operation results in a scale factor with fundamentally low sensitivity to variations in optical losses, most implementations are sensitive to changes in mean wavelength, thus the effects discussed here should be considered when designing high performance IFOGs and their electronics.

Laser diodes in sub-threshold regime are used as low- coherent broadband light sources in low-cost interferometric fiber-optic gyroscopes with better than 2 degrees/h bias repeatability over -30 degrees...+70 degrees C temperature range. The optical reflectivity of the laser diode causes nonlinear contributions to the interferometer output signal. Corresponding to theoretical calculations, the scale factor error varies in dependence on the actual rotation rate. This error for the present has been reduced to about 30 percent applying an active compensation of the light reflected in the laser diode.

To operate the R-FOG with a good linearity in a wide dynamic range, a closed-loop operation is required, in which the phase difference generated by the Sagnac effect between the counter propagating lights in the resonator is compensated by some method. So far, the phase compensation is done by making frequency difference between the two lights using frequency shifters, such as acousto-optic modulators. For a middle grade and low cost R-FOG, however, the removal of expensive devices and simpler configuration are preferable, and the complicated mechanism for the closed-loop operation should be removed. In this paper, we propose a novel method for the closed-loop operation using Faraday effect as an unreciprocal physical effect to the counter-propagating lights in the resonator. This method has a simple configuration and never needs expensive devices.

We report a new type of gyroscope using a fiber laser with a simple configuration. It consists of a Fabry-Perot type fiber laser and an interferometer which is used to combine tow output beams from both mirrors of the laser. The rotation rate is obtained from the change of the phase difference between the two output beams. The experimental results are in good agreements with theoretical predictions.

We describe the results of experimental investigations of a bidirectional Er-doped fiber ring laser for its output power and the rotation rate dependent beat signal. Enhanced gyroscope beat signal is demonstrated by using an AM mode- locked Er-doped fiber ring laser.

An anti-reflection coated GaAlAs laser diode was used as a gain medium in a mode-locked fiber laser gyroscope to obtain stable mode-locked optical pulses without gain competition. The time intervals between the pulses could be measured with much improved accuracy using an electronic counter. The rms noise equivalent rotation rate was 3.4 deg/hr/(root)Hz and the long-term drift was less than 200 deg/hr.

In this paper we present a method for characterizing the depolarizing effects of single mode fiber coils using the mathematics of impulse response functions. Some applications of the results to depolarized fiber gyro performance are described.

A light output characteristic simulation was attempted in order to find the optimal structure for 850 nm band superluminescent diodes (SLDs). The simulation results for light output-injection current characteristics, spectral modulation and the relationship between length of excitation region and light output, agreed well with actual SLD characteristics. Using the simulation method, the relationships between SLD light output and cladding layer band gap and impurity concentration were calculated to give guidelines for the design of higher-performance SLDs. The light output characteristics for SLDs with bulk and MQW structure active layers were then compared to give guidelines for the selection of type of SLD by application.

The prototype light source module with integrated-optic-chip and photo-detectors, which is applicable to a small-size and low-cost fiber optic gyro has been investigated. The module is designed so that al optical parts which are necessary to form the reciprocal configuration of the interferometric fiber optic gyroscope (I-FOG) are built in a single package except a sensing coil by using free-space optical coupling method. Reducing the number of optical components makes size smaller and assembling-cost lower. The module with an amplifier for the signal-photo-detector is contained in a single cylindrical-case. The cylindrical figure is chosen by considering the benefit that the module can be located inside any sensing coil. In order to confirm the performance of the low-cost I-FOG, a gyro test was carried out by the module connected to the single-mode fiber coil of 300 m in length. We obtained bias stability less than 0.5 deg/hr rms from this test.

A family of 1 by 2, 1 by 3, and PM miniature optic fiber couplers are developed to meet fiber optic gyroscope applications. The package size are 25 by 2.5mm for 1 by 2, 27 by 2.5mm for 1 by 3, and 35 by 2.5mm for PM coupler. THe insertion loss and other optical characteristics meet design goals and the reliability test results show that the couplers can meet the military specification.

This paper describes to the best of our knowledge the first implementation of a Lithium Niobate based 8 bit electroded integrated optic waveguide fiber optic gyro chip referred here to as 'Digi-MIOC', which has been used in a Sagnac effect exploiting micro fiber optic rate sensor ((mu) -FORS) developed by LITEF. The paper highlights various features of a Digi-MIOC, such as design philosophy, fabrication aspects, and test procedures to evaluate static and dynamic characteristics of the electro-optic parameters. As a consequence of this work, it has been possible for LITEF to cost effectively mass produce Digi-MIOCs. When used in closed loop operation, the Digi-MIOC forms the key optical component of a (mu) -FORS to aid the required optical-to- electrical signal processing to give linear output for input rates of rotation. Various test results and features of LITEF's (mu) -FORS, such as small size, large rotation rate measurement potential, low drive power and high reliability are also highlighted.

The US Army Missile Command, Research, Development and Engineering Center has been conducting research and development activities on solid-state inertial components for next generation weapon systems for the past decade. The fiber optic gyroscope (FOG), which is on an upward trend as evidenced by the increase in patents and users, warrants a closer examination to address the technology limitations associated with ultra-miniature FOG components that are designed to operate in adverse environments. Several FOG testbeds are constructed for the characterization and evaluation of the optical components operating under a series of test conditions. Analytical models are developed to aid in explaining the experimental results. The data are used in assessing the size limitations for the optical components and design approaches that tend to degrade gyroscope performance. Some remarks are mad on the effects of bending-induced birefringence in single mode fiber on the performance of depolarized FOGs. It is found that reducing the inner diameter of the sensor coil below one inch has a detrimental effect on the gyroscope performance. Furthermore, the inherent fiber crossovers in the conventional precision wound coils tend to degrade the performance of the performance of the depolarized gyroscope. The findings of our investigation will aid FOG designers in optimizing FOG optical components for applications requiring small or restricted volume for various performance regimes.

Many different types of polarization maintaining (PM) fibers and polarizing (PZ) fibers are playing important roles in most of fiber optical gyros and high speed communication networks. A new method for passively aligning and fusion- splicing those fiber types are developed with the help of the lens-effect tracing technique. Instead of calculating the correlation directly between the two POL profiles measured from the two sides of fibers, two simulated POL profiles are generated with a truncated trigonometric Fourier series expansion. The azimuthal position of each fiber and the angular offset between the fibers are then obtained by either an analytic method or an indirect correlation method. With the methods, different types of PM and PZ fibers, such as bow-tie, PANDA, elliptical core and elliptical jacket, can be automatically aligned and spliced to each other with a mean extinction ratio higher than 30 dB, and mean difference between the actively measured and passively estimated extinction ratio about 1.0 dB.

A theory describing the light propagation in biconical PM- fiber with a birefringent crystal grown all-around the fiber waist is developed.One of the crystal refractive indexes is more than the fiber cladding one, therefore the fiber inside crystal does not guide the light with corresponding state of polarization. The efficiency of such a polarization filter is conditioned by the intensity of HE₁₂ mode that is exited inside the taper with the polarization state slightly different from that of HE₁₁ mode. This anisotropy results from HE₁₁-HE₁₂ coupling resonance splitting for alternative polarization states. Corresponding values of minimum HE₁₁-HE₁₂ propagation constants differences for two polarization states are not equal to each other as well. The theory is based on the second order perturbation method for coupled waves equations solution. The common relationship for polarizer Jones matrix is obtained and associated eigenvalues are studied. The polarizer extinction ratio as calculated depends on PM-fiber anisotropy axes orientation towards crystal axes, fiber polarization beat length and other fiber parameters. The extinction ratio for standard PM-fiber is shown to be in the range of 50-70 dB and can be improved by appropriate fiber anisotropy axes orientation.

We present a method of stabilization of the mean wavelength of a superluminescent erbium-doped-fiber source which is obtained with a fiber Bragg grating acting as a broad spectral filter. This allows one to get 10 ppm stability over temperature. Excess intensity noise is reduced with a biasing phase modulation of the FOG about +/- (pi) radian instead of the usual +/- (pi) /2 radian.

Noise in a n open-loop, high sensitivity fiber optic gyro, including shot, thermal, electronic, and source (RIN) contributions, is investigated experimentally. The gyro is an al-fiber, dynamically biased, open-loop gyro operating at 1.06 micrometers . Fiber lengths of 1.0 and 2.86 km were used, both wound on 16cm radius forms. A noise subtraction technique was used to reduce RIN noise. Fits to the total noise spectrum implied approximately 40 percent residual RIN remained after subtraction. With this assumption contributions to the random walk coefficient (RWC) are calculated and shown to be in agreement with experiment. A RWC of 0.67 10^-4 deg/(root)hr was obtained.

The experiment conducted between Beijing and Taiyuan City, Shanxi province has ben done to verify the feasibility of utilizing the fiber gyro in railway system in order to enhance the transportation capacity, and safety. This report presents the experimental results of two inertial systems with one using ring laser gyros, and the other using fiber optical gyro. The former is going to be intended for track inspection, and the later for train positioning application.

In this paper, a new type of depolarized fiber optic gyroscope is described. Sensing coil is constructed by single-mode optical fiber with 200 meters length and 70 mm wounding diameter. A superluminescent diode source is used to reduce both the coherent scattering effect and Kerr effect. Two depolarizers with 1.0 percent degree of polarization and one polarizer with 40dB extinction ratio were used to reduce the output bias drift and improve the scale factor stability. A specially designed PZT phase modulator is used to suppress the AM noise. Under laboratory environment, the zero point error of 1.5 degrees/hr over seven hours with one second time constant and 700 ppm scale factor with +/- 100 degrees/sec maximum rotating rate were achieved for this depolarized I-FOG.

The formulas concerning degree of the polarization for a Lyot optical fiber depolarizer with respect to the corresponding parameters have been derived by considering splice misalignment for the first time. Experimental results verify the theoretical predictions.

Basing on the loop characteristic of closed-loop I-FOG, we propose a novel fail self-diagnosing technique and get a self-diagnosable closed-loop I-FOG. Using this kind of Gyro in redundant Strapdown inertial measure unit (RSDIMU), we design a simple and effective fault detection. isolation and system reconfiguration(FDIR) algorithm and calculate its reliability using Markov reliability evaluation mode. Compared with the old system, the reliability and the fault tolerant capability are all improved greatly.

The study on optical waveguide geodesic lenses that have no aberration and no singularity in curvature was reported. In theoretical design, the general analytical method for designing a perfect geodesic lens, which was first presented by Sottini et al., was improved. In this paper, a suitable function of meridian in transitional zone was chosen deliberately to make sure that the meridian has a continuous second order derivative. A particular solution of nonsingular in curvature, aberrationless, and non-spherical optical waveguide geodesic lens was presented. This kind of geodesic lenses was designed and fabricated with single point diamond machining and high temperature Ti-diffusing in LiNbO₃. Through experimental measurement, it was shown that the spherical aberration was eliminated in 8mm effective aperture and that the focal spot size was 3.3 micrometers for 4.78mm stop size.

This report describes closed-loop fiber optic gyroscope and related components for aircraft strap-down inertial navigation system. The closed-loop fiber optic gyroscope consists of super luminescent diode with working wavelength 1.3micrometers , fiber coupler, polarizing optical fiber coil which was fabricated by similar rectangle polarizing optical fiber with length of 500m by applying four grades symmetry twining round technology, photoelectric detector, and an integrated optical circuit (IOC) phase modulator fabricated with annealed proton and signal processing circuit technology.