Method to determine the optimal layer number for the quadrupolar fiber coil

Research on the performance of polarization-maintaining fiber (PMF) for fiber coils is significant for the precision improvement of an interferometric fiber optic gyroscope (IFOG) working in harsh environments. In this paper, we firstly report analytical models of the fiber polarization theory and present two types of hybrid PMF structures by a collaboration of geometry and stress effects: a Panda-type horizontal-elliptical core PMF (Panda-type HE-PMF) based on a superposition of geometry and stress, and a Panda-type longitudinal-elliptical core PMF (Panda-type LE-PMF) with geometry offset stress effect, achieving enhanced and suppressed modal performance by adjusting geometric anisotropy of elliptical-core in different directions. Then, the influence mechanisms of the geometric birefringence on the modal performance of both PMFs as the variation of fiber structural parameters are investigated via numerical simulations to determine the target fiber designs. The other significant attribute, including effective mode area (Aeff), nonlinear coefficient (γ), and chromatic dispersion (D), and their tolerance to PMF parameter fluctuations are also evaluated. Finally, both target PMFs with structural optimization are practically fabricated and wound into four fiber coils with quadrupolar (QAD) and 16-polar symmetrical winding patterns, respectively. The polarization ability and thermal performance are further demonstrated by experiments conducted on both PMFs, wound fiber coils, and built IFOGs under static and dynamic environments (over a wide temperature range of -40 °C to 70 °C), and compared with a conventional PMF. The testing results suggest that designed HE-PMF coils both achieve high birefringence, static extinction ratio (ER) values of up to 30.80 dB and 31.93 dB, respectively, corresponding to an almost one-fold increase over conventional coils. Remarkably, the ER property of the HE-PMF coil by combining this HE-PMF design and a 16-polar winding pattern consistently remains above 29.5 dB with a minimal fluctuation in ER of only 3.0 dB across the entire variable temperature conditions. The bias stability of the IFOG assembled with this coil is strongly enhanced to 0.0019 °/h and 0.082 °/h under static and dynamic conditions, respectively, which is a significant improvement over conventional coils of 0.136 °/h. Also, the static angle random walk performance of the improved IFOG is reduced to 0.000624 °/√h. In contrast, the LE-PMF as a comparison is shown to limited polarization characteristics with a low birefringence and ER due to the suppression effect of the geometric birefringence, and the applied IFOG output also exhibits larger drift, indicating a poor thermal ability. Experimental results show great agreement with theoretical analysis and numerical simulations, confirming the validity of design principles. The advances in both designs are instructive for the engineering applications of PMFs for IFOGs and for improving the accuracy of fiber sensors.

Parameters optimization of interferometric fiber optic gyroscope for improvement of random walk coefficient degradation in space radiation environment

Draper Laboratory's experience with Interferometer Fiber Optic Gyro (IFOG) technology started via an Internal Research and Development effort in 1978. This work led to developing fiber optic gyros in which significant advances in IFOG component technologies, assembly, integration, and test were achieved. In excess of 30 patents have been issued to Draper as a result of this pioneering effort. More recently, Draper collaborated with JPL to transition their fiber optic breadboard gyro to a space qualifiable instrument for interplanetary long duration missions. During the initial phase, brassboard gyros were designed and fabricated that demonstrated performance that bettered NASA's CRAF-Cassini spacecraft objectives. In the second phase, the Engineering Model gyro was developed to meet mission qualification tests. Concurrent with this later phase, analysis, tests and qualification activities were performed to validate that gyro components would realize the required 16 year life. Two major inventions (patent pending) were conceived; one provides for continuous adaptive scale factor stability and the other integrates the optical source and photodetector into a single component [Source Integrated Detector (SID)], thereby eliminating a coupler and several splices thus reducing loss by 6 db. Using the above technologies and the implementation of common mode rejection of laser noise, Draper has defined a low noise high performance gyro in which rate power spectral density (PSD) is projected to be < 7 X 10-7 (deg/hr)2/Hz. In those applications, where the PSD < 4 X 10-5 (deg/hr)2/Hz is sought, a small size three component (SID, integrated optics circuit and fiber coil) gyro is easily implemented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have proposed an interferometric fiber optic gyro (I-FOG) with a novel sensing fiber coil consisting of multi-core fiber (MCF) spliced with fan-in/fan-out (FIFO) devices. This sensing coil can improve the sensitivity of I-FOG without escalating the hardship of winding process of fiber to form coils. We have fabricated a seven-core MCF coil with FIFO devices and demonstrated the proper operation of the proposed I-FOG for the first time. The angular random walk performance of 0.002 deg/√h was achieved, thereby confirming that the seven-core waveguide loop works successfully as a Sagnac interferometer as expected. In addition, we evaluated the effect of temperature changes ofMCF and FIFO devices that cause fluctuations in the measured rotation rate. We confirmed that this effect shows essentially the same features as Shupe effect (non-reciprocal phase shift error due to changing environmental temperature) which is a well-known feature of conventional I-FOGs.

In this paper, a full parameter mathematical model of temperature error of optical fiber coil is established. The new model can be used to optimize the physical and chemical properties of different winding schemes (quadrupole, multipole), fiber, colloid and other components in the coil, as well as the assembly structure, and to study the influence of the technological parameters such as the number of winding layers and winding schemes on the temperature performance of the optical fiber coil under different winding conditions. An on-line measurement and compensation system for core parameters of high-precision optical fiber coil is designed and built. In view of the characteristics of long length, large size and high winding difficulty in the actual winding process of high-precision optical fiber coil, based on the self-developed high-precision coil winding machine, the mechanism of errors such as stress, polarization crosstalk and symmetry introduced in the winding process is studied, and the real-time online detection system of core parameters is designed and built, which is used for realtime online detection and online compensation, so as to further develop Step by step to improve the winding success rate of high-precision optical fiber coil. A complete set of high- precision fiber coil forming technology is studied. In this paper, every link of the high-precision fiber coil forming process is studied. From the selection of optical fiber and colloid materials, automatic winding, debonding and coil forming to the detection technology of optical fiber coil, the integrated design is carried out, and the high-precision optical fiber coil meeting the application of high-precision optical fiber gyroscope is finally prepared by using the whole set of technology.

A plate-fin-type methanol reformer was made by preparing Cu-Zn/Al2O3/Al-plate and Pt/Al2O3/Al-plate catalysts on an aluminum plate with aluminum fins on the surfaces of both sides. Feed gas composed of methanol and steam was supplied to the Cu-Zn/Al2O3/Al-plate-catalyst side and combustion gas composed of hydrogen and air was supplied to the Pt/Al2O3/Al-plate-catalyst side. The methanol steam-reforming reaction, which is endothermic, was carried out on the Cu-Zn/Al2O3/Al-plate catalyst and the hydrogen-oxygen combustion reaction, which is exothermic, was carried out on the Pt/Al2O3/Al-plate catalyst to supply the heat needed for the methanol steam-reforming reaction to the other side. This reformer’s steam-reforming characteristics are superior to those of a fixed-bed-type methanol reformer with commercial CuO-ZnO-particle and Pt/Al2O3-particle catalysts. The gas temperature of its catalytic combustion part was similar to that of the methanol steam-reforming part at each point in the gas-flow direction. In the fixed-bed-type methanol reformer, on the other hand, it was about twenty degrees higher. The start-up time of the plate-fin-type methanol reformer was 28% of that of the fixed-bed-type methanol reformer. And its overall heat transfer coefficient was 16 times larger. Therefore, we conclude that this large overall heat transfer coefficient contributes to its higher performance and shorter start-up time as well as its large apparent heat transfer surface area. The catalyst volume in the plate-fin-type methanol reformer was only 11% of that in the fixed-bed-type one even though its methanol steam-reforming characteristics were superior. Thus, the plate-fin-type methanol reformer is an effective way to reduce the reformer size and start-up time.

The degradation of optical symmetry caused by the thermal strain of the fiber coil results in the thermal bias drift of fiber optic gyro (FOG). This paper presents a method for quantitative analysis of the optical symmetry of the fiber coil and accurate prediction of thermal bias drift in FOG. Firstly, a thermal strain model is established to illustrate the strain characteristics of the layer structure in the fiber coil under temperature fields, emphasizing the importance of thermal strain on optical symmetry. Then, an equivalent asymmetric index (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α_Tk</i>) is introduced to quantitatively evaluate the optical symmetry of the fiber coil. By deriving equations for optical symmetry and thermal bias drift caused by thermal strain, a novel method is proposed to predict and optimize the thermal bias drift. This method utilizes high-performance OFDR to measure temperature and strain in a 3 km fiber coil to predict thermal bias drift. It also discusses the relationship between the length of the tail fiber and optical symmetry, predicting the precise length required to optimize thermal bias drift. Subsequently, the same fiber coil is placed in the FOG to verify the accuracy of the thermal bias drift prediction. Adjusting the length of the tail fiber reduces the thermal bias drift from 0.33 °/h to 0.13 °/h.

In this paper, a novel optical approach to double the sensitivity to angular rate of interferometric fiber optic gyroscope (IFOG) is proposed. Two fiber polarization combiner/splitters (FPCSs), as the key components, are added in the traditional IFOG light path. The FPCSs are able to either combine two orthogonal polarizations transmitting at two different polarization-maintaining fibers (PMFs) into the two orthogonal axes of one PMF, respectively, or split two polarizations transmitting at the two orthogonal axes of one PMF into two polarizations to transmit at two different PMFs, respectively. Through the specific placement and coupling of these two FPCSs, the incident light can transmit twice along the polarization-maintaining fiber coil (PMFC). The novel approach is verified experimentally and the experimental results show consistency with the theoretical analysis. The proposed approach is able to double the sensitivity of IFOGs and can increase the signal-to-noise ratio (SNR) without increasing the length of PMFC, which is very susceptible to environmental influences and is of great significance in the technical improvement of IFOGs, as well as the miniaturization of IFOGs.

Interferometric fiber optic gyroscope (IFOG) is advantageous for inertial navigation due to its high reliability as a solid-state technology with no moving parts. The size, weight, power, and cost of IFOG can be improved by employing photonic integration technology. Here, by leveraging the foundry-enabled silicon photonics platform, we demonstrate a silicon multi-function integrated optical circuit (Si-MIOC) with a fingertip size that can easily interfaces with light source and fiber coil to perform a tactical-grade gyroscope (0.1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> /hr bias instability). This achievement comes from the pros of high-index-contrast silicon waveguide that enables high polarization extinction ratio of > 60 dB and high electro-optic efficiency in silicon phase modulator, while the cons of the signature lead to non-negligible optical back-reflection at silicon/fiber interfaces and generate spurious bias voltage offset at the gyroscope outputs. Nevertheless, the results of earth rotation measurement and Allan deviation analysis confirmed that Si-MIOC based IFOG is a promising angular sensor and can be utilized to construct a compact and low-cost inertial measurement unit.

Dual-polarization interferometric fiber optic gyroscope (IFOG) is a novel scheme in which the polarization nonreciprocal (PN) phase error of the two orthogonal polarizations can be optically compensated. In this work, we investigate the effective of PN phase error compensation under varying temperature. It is proved that, the thermally induced strain deforms the fiber, and results in perturbations on the birefringence and polarization cross coupling which degrades the IFOG's stability. A wave propagation model and analytical expressions of PN phase error are derived by using coupled-wave equation and Jones matrix. We theoretically and experimentally verify that, although the single-mode (SM) and polarization-maintaining (PM) fiber coils behave different owing to their intrinsic properties of wave propagation, the thermal strain induced PN phase error can still be compensated under slow and adiabatic temperature variations. This could be a promising feature to overcome the temperature fragility of IFOG.

In this work, the fiber optic gyroscope (FOG) with an elliptic fiber coil (EFC) is applied to the inertial measurement of petroleum well trajectory for the special condition of the borehole diameter limitation in the inclinometer while drilling (IWD). The three-dimensional (3D) Shupe error mathematical model and finite element model of the EFC are established by the quadrupole symmetrical technique, which is based on the Shupe effect of fiber coil. Then, the simulation experiments and the temperature experiments of the EFC are carried out to verify the correctness of the mathematical model. Under this prerequisite, the influence of the structure parameters of the EFC on the Shupe error is analyzed. In order to compare the rotation rate error between the EFC and the circular fiber coil (CFC), the temperature experiments of the EFC and the CFC are carried out with the same temperature excitation when the fiber length, the layers of fiber coil, and the radius of fiber coil of the EFC are the same as those of the CFC. The results show that the bias stability of the EFC is 35% to 39% smaller than that of the CFC before the temperature compensation, and after the temperature compensation, the bias stability of the EFC is 49% to 70% smaller than that of the CFC.

Microservice architectures have become one of the main approaches to developing complex distributed software systems. Microservices allow for greater flexibility and simplify the maintenance of parts: each microservice can be updated, installed or improved independently. Microservices are used to develop service management platforms (ITSM/ESM) – software systems used to automate business processes. Managing IT assets, infrastructure configuration elements and handling incidents make these platforms critical for a corporation. They must meet strict requirements for response time, security, etc. Another important characteristic is scalability: the ability of the system to cope with an increasing volume of work (for large companies, the number of incidents grows like an avalanche). It is ensured by a rapid increase in the number of system instances by a cloud provider or container orchestration systems such as Kubernetes or OpenShift. Software frameworks must support containerization and have a short startup time. This paper proposes a methodology for evaluating Java frameworks for developing ITSM/ESM process automation systems in order to ensure the required level of application scalability. A set of frameworks such as Spring Boot, Micronaut are examined from the point of view of different aspects: prevalence, availability of the required functionality, as well as functioning in conditions as close to production as possible – inside a container placed in a Kubernetes environment. Several examples of atomic, single-class applications written in these frameworks were launched in containers. The startup time, CPU and RAM usage were measured. According to the results of the study, Quarkus showed the best overall result and can be recommended for developing mission-critical distributed applications. The work will be useful for software architects, developers and technical directors as a methodology for choosing a technology stack for cloud native applications.

Performance comparison regarding loop heat pipes with different evaporator structures

Layup optimization of ramie fabric reinforced composite: Woven fabric and lamination parameters

In this paper, the composite loss factor, vibration acceleration level and displacement of a multi-layer flat-shaped constrained damping structure are studied by means of the single-point hammer excitation method and the modal strain energy method. The influence of the number of damping layers on the damping performance of the constrained damping structure is discussed, and the optimal number of layers is determined. The experimental results show that with the increase of the number of damping layers, the loss factor gradually increases, but the increasing range decreases gradually. The loss factor obtained in this study is 0.049, 0.028, and 0.022 respectively. The maximum vibration acceleration level is 15dB, 3dB and 4dB respectively. In addition, the maximum displacement of the structure calculated by the modal strain energy method shows a decreasing trend, which is 0.542, 0.546, 0.383, and 0.264, respectively. The composite loss factor has the same trend as that obtained from the experimental results, with an error very close to 20%. The higher level error is slightly larger, but still less than 25% with good consistency. The results show that the damping effect of the multi-layer plate type confinement damping structure is better than that of the single-layer damping structure. The optimal number of layers is 3.