Polarization Maintaining Fiber Coil Research Articles

Highly Stable Gyroscope Composed of Panda-Type Polarization-Maintaining Fiber Coil With Strong Resistance to Thermal Stress

Highly Stable Gyroscope Composed of Panda-Type Polarization-Maintaining Fiber Coil With Strong Resistance to Thermal Stress

Temperature and vibration insensitive fiber optic vector magnetic field sensor

We propose and demonstrate a fiber optic vector magnetic field sensor based on the magneto-optical Faraday effect. The sensor has excellent environmental adaptability. Due to the polarization dependence of Faraday effect in polarization-maintaining fiber coil, the sensor uses two orthogonal polarization states to detect the direction and intensity of magnetic field. By establishing the magnetic sensitivity model of the sensor through the Jones matrix, we analyze the magnetic field-induced phase difference in the two orthogonal polarization states theoretically. Then the influence of environmental temperature and vibration on the output of the two polarization states of the sensor is analyzed, and the sensor can theoretically achieve complete suppression of environmental temperature and vibration errors. The experimental results show that the sensor sensitivity is 0.507 mV/mT. The directivity of the vector magnetic field sensor reaches 21 dB with the orientation error of ±0.4°. The sensor also has excellent robustness. It is insensitive to environmental temperature changes between 30 °C and 50 °C and environmental vibrations within 1 g. The suppression effect of environmental errors can reach 9.8 times with high anti-interference capability in experiments. The proposed sensor has potential applications in navigation, vehicle detection, and current sensing.

Distributed Polarization Characteristic Testing for Optical Closed Loop of Sagnac Interferometer

Distributed polarization characteristic of Sagnac optical closed loop that composed of two polarizing devices– polarization maintaining fiber coil and Y-waveguide, can directly affect the performance of fiber optic sensors. Several existing methods are applicable for only one device testing at a time, the efficiency is therefore relatively low and the connection quality between devices is unavailable. In this paper, the Sagnac optical closed loop is split into semi-closed loop (SCL) and full-closed loop (FCL) structures. The transmission behavior of polarized optical signal is fully analyzed, and the information of polarization mode crosstalk is positioned and extracted accurately. By conducting one test of SCL and FCL respectively utilizing white light interferometry, the distributed polarization characteristic of both optical devices and connection points can be entirely obtained. The testing results of optical closed loop are highly consistent with single device test and the difference is less than 0.2dB. A good testing stability is demonstrated through ten repeat measurements and the fluctuation is almost around 0.1dB. We believe that the proposed testing method is capable of promoting the assembly of high-performance Sagnac interferometer and the development of fiber optic sensors.

High extinction ratio elliptical core Panda-type polarization-maintaining fiber coil.

The polarization-maintaining performance of the traditional Panda-type polarization-maintaining fiber (PMF) coil is significantly affected by winding stress and temperature. Here, we present an elliptical core Panda-type PMF coil based on a fiber that employs both geometric and stress birefringence. The extinction ratio of the elliptical core PMF coil was found to be 20.13 dB at a temperature of 20°C, corresponding to an increase of 3.71 dB compared to the traditional Panda-type PMF coil. In addition, results from distributed polarization cross talk and gyroscope output tests also revealed a low sensitivity of the fiber to stress caused by the winding process and temperature. In summary, the proposed fiber coil has better polarization-maintaining ability compared to conventional coil and is promising for applications in high-precision optical fiber sensors.

High Accuracy Distributed Polarization Extinction Ratio Measurement For a Polarization-Maintaining Device With Strong Polarization Crosstalk

Polarization extinction ratio (PER) is a quantitative indicator of the polarization-maintaining (PM) ability of a device. In this work, we present a distributed PER measurement method based on white-light interferometry. It can accurately measure the PER distribution of a PM device even in the presence of strong polarization crosstalk. We show that the distributed PER can be expressed as the reciprocal of the accumulated polarization crosstalk along the device. Thus, the PER distribution of a PM device can be calculated from the distributed polarization crosstalk. In the presence of strong polarization crosstalk, we introduced a concept of polarization crosstalk induced loss to prove that there is a significant error of the measured distributed polarization crosstalk. The error can be accurately estimated and be calibrated out from the measurement result. To verify the measurement method and the calibration accuracy, we used a commercial PER meter that can only measure the total PER of a device as the reference. We simulated a quasi-distributed PER device under test (DUT) by successively splicing 15 pieces of PM fibers and measured its total PER after splicing each piece of fiber. The calculated distributed PER of the DUT after error calibration matches well with the quasi-distributed result at the corresponding locations. Finally, we applied the method to measure the distributed PER and total PER of a PM fiber coil. After error calibration, the residual error (i.e., the difference with the commercial PER meter) in the total PER, thus of the distributed PER, is less than 0.1 dB.

Estimation of gyro bias drift due to distributed polarization cross coupling in the fiber coil.

Distributed polarization cross coupling (PCC) along the polarization-maintaining fiber (PMF), obtained from an optical coherence domain polarimetry (OCDP) system, is analyzed. It is found that the measured PCC data at each measurement location is the sum of the OCDP source coherence function centered at a series of discrete PCC points, which do not represent the true PCC information. An algorithm is developed to extract the "true" location and strength of the PCC and the extracted PCC data are no longer source dependent. A model is developed to relate the extracted PCC data in the PMF coil to the fiber optic gyro (FOG) bias drift due to coherent PCC. Experimental results obtained with a FOG with a ~3 km PMF coil and light sources of different bandwidths agree with the theoretically estimated bias drifts.

Opto-Electron Eng, 2018, 45(9)] Recent progress of accurate measurement for distributed polarization crosstalk of fiber optic polarization component and device

The polarization crosstalk of a fiber optic polarization component and device refers to the optical power coupling that occurs at a disturbance point between the two orthogonal polarized modes propagating in it. The distributed polarization crosstalk along with the light propagation direction is directly responsible for the optical polarization properties, for example, the polarization, elliptical polarization, and depolarization properties. It also indirectly reflects the manufacturing technique and the state of the ambient environment, for example, the stress and strain at the joint and fixed position, as well as the temperature. Thus, it is the comprehensive embodiment of the intrinsic performance of the fiber optic polarization component and device and the influence of environment. It is expected to be a general characteristic parameter for online testing, diagnosis, and evaluation of the performance of the fiber optic polarization component and device. The best measurement method for distributed polarization crosstalk till now is the optical coherence domain polarimetry (OCDP). It is based on the white light interferometry and accurately measures the position and amplitude of the distributed polarization crosstalk using a scanning white light interferometer to realize interference between different polarized modes. It has the merits of ultrahigh sensitivity, ultra-wide dynamic range, and ultra-long measurable length. This review paper takes the polarization maintaining fiber coil and multifunctional integrated optical modulator as examples of distributed polarization crosstalk measurement and application. Firstly, the measurement principle of distributed polarization crosstalk based on the OCDP is introduced. Secondly, the measurement error sources and corresponding suppression methods are reviewed. Thirdly, the accurate measurement results of the fiber optic polarization component and device at different temperature are demonstrated. In the end, it outlooks the development of distributed polarization crosstalk measurement considering the complicated and changeable operation environment of the fiber optic polarization component and device.

High-resolution distributed polarization crosstalk measurement for polarization maintaining fiber with considerable dispersion.

We present a high-resolution polarization crosstalk measurement method for polarization maintaining fiber (PMF) with considerable dispersion. The birefringence dispersion of the PMF severely degrades the spatial resolution of the distributed polarization crosstalk measurement. Conventional dispersion compensation methods are effective for modest birefringence dispersion coefficients (for instance, of 0.0014 ps/nm/km). We present an iterative matched filter (IMF) method to cope with the case of considerable birefringence dispersion. We measured the distributed polarization crosstalk of a PMF coil with a birefringence dispersion coefficient of 0.235 ps/nm/km. By applying the IMF method, we obtained a spatial resolution of 0.09 m at any position of the PMF (a maximum of 12.36 m without dispersion compensation).

Temperature Dependence of Faraday Effect-Induced Bias Error in a Fiber Optic Gyroscope.

Improving the performance of interferometric fiber optic gyroscope (IFOG) in harsh environments, such as magnetic field and temperature field variation, is necessary for its practical applications. This paper presents an investigation of Faraday effect-induced bias error of IFOG under varying temperature. Jones matrix method is utilized to formulize the temperature dependence of Faraday effect-induced bias error. Theoretical results show that the Faraday effect-induced bias error changes with the temperature in the non-skeleton polarization maintaining (PM) fiber coil. This phenomenon is caused by the temperature dependence of linear birefringence and Verdet constant of PM fiber. Particularly, Faraday effect-induced bias errors of two polarizations always have opposite signs that can be compensated optically regardless of the changes of the temperature. Two experiments with a 1000 m non-skeleton PM fiber coil are performed, and the experimental results support these theoretical predictions. This study is promising for improving the bias stability of IFOG.

光纤环和Y 波导调制器直接耦合偏振轴测量

光纤环和Y 波导调制器直接耦合偏振轴测量

Heterodyne fiber-optic gyroscope using orthogonally polarized two-frequency beams

A new type of heterodyne fiber-optic gyroscope using orthogonally polarized light components with different frequencies is described. Each counterpropagating beam consists of the orthogonal components transmitted in the principal axes of a polarization-maintaining fiber coil. A pair of beat signals containing Sagnac phase shifts with opposite signs can be produced by selectively superimposing the counterpropagating components. Detection of the difference between the two beat signals allows a doubling of the Sagnac phase shift free from noise sources raised from differences in frequency and path. In a preliminary experiment, a long-term stability of 5 degrees /h was attained.

Drift of an optical fiber gyroscope caused by the Faraday effect: Experiment

Mechanism of the drift generation by the Faraday effect in the optical fiber gyroscope with polarization maintaining fiber coil is studied in the experiments. The results are in good agreement with the theory which we presented previously. The presence of the fiber twist component whose period is just equal to one turn of the polarization-maintaining fiber coil is shown experimentally to cause the drift. The reduction of such a special twin component is essential to reduce the drift caused by the Faraday effect.