Fiber Ring Interferometer Research Articles

Correction to: Polarisation non-reciprocity cancelling in Sagnac fibre ring interferometer: an attempt of realistic study

Correction to: Polarisation non-reciprocity cancelling in Sagnac fibre ring interferometer: an attempt of realistic study

Theoretical analysis of the non-reciprocal phase shifts due to birefringence and topology in fiber ring interferometers

The non-reciprocal phase shifts in fiber ring interferometers due to the fiber birefringence and the path topology are investigated for the first time. It is shown that the resultant birefringence of the fiber, which is the combination of the linear birefringence intrinsic to the fiber and the circular birefringence induced by the twisting in the fiber coiling, is not reciprocal for both rays in the bidirectional propagation due to the path topology confined by the coiled fiber. Our model indicates that the performance of fiber ring interferometers periodically depends on both the linear and the circular birefringence of the coiled fiber, and the bias error can be reduced by the typical fabrication process of the fiber ring interferometers.

Polarisation non-reciprocity cancelling in Sagnac fibre ring interferometer: an attempt of realistic study

Polarisation non-reciprocity (PNR) of Sagnac fibre ring interferometer (FRI) is one the fundamental limits of its long term bias stability. PNR value, being huge initially, then was reduced strongly, but after that PNR problem was left far from PNR cancelling. The latter may be defined as PNR reducing up to 10−10 deg/h when it does not prevent detecting the general relativistic Lense–Thirring effect. Clearly, such PNR cancelling may be treated only theoretically at this point. In this case, one has to model all practical defects of FRI. Present paper describes such kind of study for FRI of commercial fibre optic gyro implementing medium quality components. It is shown that for PNR cancelling, several meters fibre polariser is enough, despite of the stringent limitations of its standard polarisation extinction ratio. Also, a complete FRI configuration is treated for the first time in available literature, including an imperfect fibre coupler. This yields one more PNR component which is non-zero even for completely unpolarised light and which can be effectively suppressed by the fibre polariser too.

Low insertion loss optical pulse interleaving for ultra-low phase noise photonic microwave generation.

We report a 32-times multiplication of optical pulse rate based on a cascaded optical fiber ring interferometer for generating ultra-low noise photonic microwaves. The optical power loss of the interleaver is approximately 0.5 dB, which is the lowest insertion loss for optical pulse interleaving to date. The time delay in each interleaver stage is precisely controlled by measuring the power ratio between the harmonics of the generated microwaves. In addition, the relationship between the phase noise reduction from the continuous-wave shot noise limit and interleaver delay errors is verified experimentally for the first time. Finally, a phase noise level of -173 dBc/Hz for a single multiplication channel at an offset frequency of 2 MHz was measured.

A fiber ring interferometer for measuring spectral widths of emission lines of single-frequency lasers

A fiber ring multipass scanning interferometer has been designed for measuring spectral widths of emission lines of single-frequency fiber lasers at a wavelength of 1.55 μm in a range of 5 kHz to 1 MHz with a signal level of 0.5 mW and higher.

Geometric phase of a classical Aharonov–Bohm Hamiltonian

Abstract We present a gauge-invariant approach for associating a geometric phase with the phase space trajectory of a classical dynamical system. As an application, we consider the classical analog of the quantum Aharonov–Bohm (AB) Hamiltonian for a charged particle orbiting around a current carrying long thin solenoid. We compute the classical geometric phase of a closed phase space trajectory, and also determine its dependence on the magnetic flux enclosed by the orbit. We study the similarities and differences between this classical geometric phase and the AB phase acquired by the wave function of the quantum AB Hamiltonian. We suggest an experiment to measure the geometric phase for the classical AB system, by using an appropriate optical fiber ring interferometer.

Suppression of polarization errors in fiber-ring interferometer by polarizing fibers

Polarization errors in a Sagnac fiber-ring interferometer are considered. It is shown that the joint application of polarizing fibers at the input of the interferometer and the sensing coil is able to radically suppress these errors.

Methods for calculating the temperature zero drift initiated in fiber ring interferometers by random inhomogeneities in single-mode optical fibers

The specific features of the existing methods used for calculating the temperature zero drift initiated in fiber ring interferometers (FRIs) by linear coupling between polarization eigenmodes at random inhomogeneities in single-mode optical fibers are analyzed. The ranges of applicability of each method are determined. It is demonstrated that numerical simulation with a variation in the temperature of the single-mode optical fiber of the FRI loop is the most complex and, at the same time, the most universal method.

Spectral analysis of the temperature dependence of the nonreciprocal phase difference of counterpropagating waves in a fiber ring interferometer

Using the method of the Fourier analysis, we obtain spectral-density distributions of the dependence of the nonreciprocal phase difference of counterpropagating waves at the output of a fiber ring interferometer on the temperature of a single-mode fiber lightguide of the interferometer circuit. It is shown that the main role in measuring the nonreciprocal phase difference is played by the temperature variation in the difference of the optical-path in slow and fast birefringence axes of the single-mode fiber lightguide between the circuit ends and random irregularities.

Double-polarization fiber ring interferometer based on a single-mode isotropic fiber for gyroscopy

We propose and implement the scheme of a whole-fiber double-polarization ring interferometer based on an isotropic fiber for gyroscopy purposes. The results of an experimental study of the output signal of the interferometer based on the proposed scheme are presented. The shift of the zero point of the interferometer signal (at a level of 3°/h) and the drift of the zero point (at a level of 1°/h) are determined. The rotation sensitivity of the interferometer is measured. It amounts to 0.1°/h, which agrees well with the calculation allowing for the shot noise of the photoelectric current at the output of the scheme.

Mathematical modeling of random coupling between polarization modes in single-mode optical fibers: XV. Dependence of integral statistical parameters of polarization modes in single-mode optical fibers with random inhomogeneities on the wavelength of light

Spectral dependences of integral statistical elements of the Jones matrix of an extended segment of a single-mode optical fiber (SMOF) with random inhomogeneities, whose length considerably exceeds the correlation length of random inhomogeneities, are found by the method of mathematical modeling. The boundaries of the ranges of optical wavelengths are determined, within the limits of which the parameters under consideration remain quasi-constant. This allows the derivation of analytical expressions for the degree of polarization of nonmonochromatic radiation in an SMOF and for the zero drift in fiber ring interferometers with the help of the approximate method of small perturbations. It is shown that the small-perturbation method leads to adequate results for SMOFs with strong and intermediate linear birefringence.

Frequency response measurement of high-speed photodetectors using the spectrum power method in a delay self-heterodyne system

An improved delay self-heterodyne system consisting of a distributed Bragg reflector (DBR) tunable laser and an optical fiber ring interferometer is used to measure the frequency responses of high-speed photodetectors. By adjusting the amplitude of the phase-tuning-voltage which is applied across the phase section of the DBR laser, the beat signals with frequencies from zero to several tens of gigahertz will be generated at the photodetectors. The peak power method (PPM) and spectrum power method (SPM) were used to measure the frequency response of photodetectors. The effects of the phase-tuning-voltage over different ranges on the measurement accuracy were experimentally investigated. Theoretical analysis indicates that the variations of optical linewidth and lineshape are the main reasons for producing a large error in the measurement by PPM, and that the fluctuation of optical power did not generate errors in the frequency response measurements by both PPM and SPM. The experimental results show that when a low phase-tuning-voltage range is used in measurement by SPM, the error of the measuring frequency response of the photodetector can be sharply reduced.

Mathematical modeling of random coupling between polarization modes in single-mode optical fibers: XIV. Spectral characteristics of nonreciprocal phase difference of counterpropagating waves at the output of a fiber ring interferometer at a change in the fiber temperature

Distributions of the spectral density of the dependence of the phase difference of counterpropagating waves in a fiber ring interferometer (FRI) on the temperature of the single-mode optical fiber (SMOF) in the FRI loop (temperature spectra of the FRI zero drift) due to polarization nonreciprocity have been obtained by Fourier analysis for different spectral linewidths of the FRI radiation source and different linear birefringences of the SMOF in the FRI loop. It is shown that a change in the temperature of the SMOF in the FRI loop changes mainly the SMOF linear birefringence. This effect leads to a change in the phases of the radiation that is transferred from one polarization mode to another at those points in the SMOF where the random twisting of the axes of unperturbed linear birefringence of the SMOF changes. The effect of the magnitude of the jump under consideration, its location with respect to the nearest FRI loop end, and the magnitude of the cross-correlation (visibility) function of the radiation transmitted along the slow and fast SMOF axes from the loop end to the point where a jump in twisting of the SMOF axes occurs on the character of the temperature spectra of the FRI zero drift is determined. It is shown that in the case where the depolarization length of nonmonochromatic radiation in an SMOF is smaller than the average length of the SMOF segment on which random twisting is constant, the qualitative and quantitative characteristics of the temperature spectra of the FRI zero drift depend strongly on the polarization state of the radiation at the input of the FRI loop. The reason for this difference is explained.

Mathematical modeling of random coupling between polarization modes in single-mode optical fibers: XIII. Conditions of applicability of the ergodic hypothesis for fiber ring interferometers

Some additional conditions of applicability of the ergodic hypothesis to fiber ring interferometers (FRIs) with a loop consisting of a single-mode optical fiber (SMOF) with random inhomogeneities are considered. It is shown by mathematical modeling that the change in the phase difference of counterpropagating waves at the FRI output with the SMOF temperature is not a stationary random process. However, in a fairly narrow temperature range, this dependence can be assumed to be locally stationary. The conditions determining this temperature range are formulated. It is shown for a fairly large ensemble of independent realizations of random inhomogeneities in an SMOF that, even when all conditions of ergodicity are satisfied with a large margin, there will always be at least one realization violating strict ergodicity. Thus, only conditional (approximate) ergodicity occurs in this case. Nevertheless, in calculation of the FRI zero drift in this situation, averaging over an ensemble of independent realizations of random inhomogeneities in the SMOF of an FRI loop can be performed with sufficient accuracy. As a result, calculations are simplified significantly. In the general case, when at least one of the conditions of ergodicity is not satisfied, averaging over temperature for each realization with subsequent averaging over the entire ensemble should be performed. It is shown also that, within this problem, we can speak only about quasi-ergodicity or emulation of ergodicity, since a change in the temperature of the SMOF of an FRI loop and successive enumeration of independent realizations of random inhomogeneities in the SMOF loop are radically different random processes. The parameters characterizing quasiperiodic temperature changes in the phase difference of counterpropagating waves at the FRI output are refined.

Improved Optical Heterodyne Methods for Measuring Frequency Responses of Photodetectors

An improved optical self-heterodyne method utilizing a distributed Bragg reflector (DBR) tunable laser and an optical fiber ring interferometer is presented in this paper. The interference efficiency can be increased by 7 dB compared with the scheme using the conventional Mach-Zehnder interferometer. The unsteady process that the beating frequency experiences in each tuning period is investigated. According to the measurement results, the wavelength and optical power of the tunable laser will be steady when the square-wave frequency is lower than 300 kHz. It has been shown that when a square-wave voltage is applied to the phase section of the tunable laser, the laser linewidths vary in a wide range, and are much larger than that under dc voltage tuning. The errors caused by the variations in the linewidth of the beat signal and optical power can be eliminated using the proposed calibration procedures, and the measurement accuracy can, therefore, be significantly improved. Experiments show that the frequency responses obtained using our method agree well with the data provided by the manufacturer, and the improved optical self-heterodyne method is as accurate as the intensity noise technique.

To the paper “Influence of radiation coherence on the effects of polarization nonreciprocity of fiber ring interferometers” by I. A. Andronova, Radiophys. Quantum Electron., 47, Nos. 10–11, 882 (2004)

To the paper “Influence of radiation coherence on the effects of polarization nonreciprocity of fiber ring interferometers” by I. A. Andronova, Radiophys. Quantum Electron., 47, Nos. 10–11, 882 (2004)

Influence of a Regenerative Amplifier on the Sensitivity of a Resonant Fiber Ring Interferometer to Rotation

We consider the possibility of using a regenerative amplifier based on an intracavity active fiber to enhance the rotation sensitivity of the resonant fiber ring interferometer (RFRI) with an external reflector and a low-coherence source. The influence of amplifier noise on the RFRI sensitivity to rotation is discussed. It is shown that the use of a regenerative amplifier makes it possible to obtain the maximum sensitivity with a lower-power source due to compensation for cavity losses. Comparison with the sensitivity of the conventional nonresonant fiber ring interferometer (NFRI) is done.

Mathematical Modeling of Random Coupling between Polarization Modes in Single-Mode Optical Fibers: XII. Dependence of the Zero Drift in Fiber Ring Interferometers in Orthogonal Polarization Modes on the Range of Temperature Variation in an Optical Fiber

Temperature dependences of the zero drift in a fiber ring interferometer (FRI) without a polarizer in the presence of random inhomogeneities in a single-mode optical fiber in the FRI loop are obtained by numerical simulation. The results are compared with known experimental data. It is shown that FRIs using a superluminescent diode as a source of nonmonochromatic radiation and a loop made of a single-mode optical fiber with weak linear birefringence can find application as low-accuracy fiber-optic gyroscopes and FRIs with a loop made of a single-mode optical fiber with strong linear birefringence can be used as medium-accuracy fiber-optic gyroscopes.

Mathematical modeling of random coupling between polarization modes in single-mode optical fibers: XI. Dependence of the zero drift of fiber ring interferometers on the interval of temperature variation of the fiber

The dependence of the value of the zero drift of a fiber ring interferometer (FRI), which is caused by a change in polarization nonreciprocity as a consequence of a change in the random coupling of polarization modes at inhomogeneities of the FRI loop, on the value of the interval of possible temperature variation of the single-mode optical fiber (SMF) of the FRI loop is considered. It is shown that the value of the zero drift of an FRI with a nonmonochromatic radiation source—a superluminescent diode—in a rather broad interval of temperature variations (about 100 K) is proportional to the value of the interval itself and inversely proportional to the linewidth of the radiation source. Numerical estimations are made, and they show that, for practical values of the interval of temperature variation in a room, the value of the zero drift may be much smaller than the values calculated according to the method of averaging over independent realizations of random inhomogeneities in the SMF of an FRI loop. When temperature stabilization is used, the value of the zero drift of an FRI can be additionally reduced by one to two orders of magnitude.

Influence of the irregularity of twisting of the birefringence axes of single-mode optical fibers on the polarization nonreciprocity of fiber ring interferometers

A particular example of the so-called minimum-configuration fiber ring interferometer whose loop comprises two different-length segments of a single-mode optical fiber with the same linear birefringence but different twisting is used to show that even in the case where the birefringence axes at the loop input coincide with the polarizer transmission direction, the phenomenon of polarization nonreciprocity of the fiber ring interferometer can emerge. It is shown that polarization nonreciprocity can be eliminated by the proper adjustment of the axes of a single-mode optical fiber, but the above adjustment should be changed if the waveguide temperature is changed. It is also shown that polarization nonreciprocity is a function of the light wavelength and the polarization nonreciprocity value in a fiber ring interferometer varies quasiperiodically in response to the temperature change in an optical fiber with random irregularities.