This PDF file contains the front matter associated with SPIE Proceedings Volume 11405, including the Title Page, Copyright information, and Table of Contents.

Mechanical gyro limitations and reliability issues drove the development of the ring laser gyro in the 1960s. Just as production prototypes began to emerge in the mid-1970s the first fiber gyro breadboard emerged. This paper provides an overview of factors that have driven the development of the fiber optic gyro, its applications, and recommendations for further information.

Based on the experience acquired early from pioneering work at Stanford University and Thomson-CSF starting in the mid 70s, fiber optic gyro (FOG) R&D began at Photonetics in the late 80s to yield OCTANS, a FOG-based inertial strapdown system providing attitude and gyro compassing, at the end of the 90s. This FOG activity was spun out from Photonetics in October 2000 to create iXsea with only 16 people. The product line was rapidly expanded with PHINS, an inertial-grade INS (Inertial Navigation System) and later with MARINS, a strategic-grade INS, as well as with ASTRIX systems developed for satellites in cooperation with EADS-Astrium (today Airbus Defence & Space). In 2010, iXsea merged with several subsidiaries of its parent company, iXcore, to create iXblue. Among these subsidiaries were iXfiber, a maker of specialty fibers, and Photline, producing lithium-niobate integrated optics, hence allowing iXblue to fully master the key FOG components supply chain. Ten years later, the ‘adventure' is continuing and the former start-up is now quite a significant player in the inertial world, especially for high-grade applications. The cumulated number of high-performance 3-axis systems in service has grown to over 8,000, i.e. more than 25,000 FOG axes, with a bias stability ranging from 30 mdeg/h down to 15 μdeg/h, and an angular random walk (ARW) performance ranging from 8 mdeg/√h down to 40 μdeg/√h depending on the size of their sensing coils (3 m² to 1000 m²) and on the application!

Fiber optic gyros are a mature product and have been in production for nearly three decades. Over 200,000 have been delivered to customers. This paper will review the recent improvements that have been made to fiber optic gyros and the systems that use them at Northrop Grumman Corporation. These improvements reduce gyro noise, improve bias and scale factor errors, reduce cost, and improve reliability in inertial measurement units (IMUs), inertial navigation systems (INS), and marine navigation systems.

A new mechanism for extracting rotation rate information by analyzing the polarization of light exiting from a Sagnac loop is reported. Unlike in an interferometric fiber optic gyroscope (I-FOG), here the counter-propagating waves in the Sagnac loop are orthogonally polarized at the loop exit and cannot directly interfere with each other. We show the phase difference between the counter propagation waves can be obtained by the Stokes parameters s2 and s3 of the combined waves. We build such a proof-of-concept polarimetry FOG and achieved key performance parameters comparable to those of a high-end tactical-grade gyroscope. In particular, the device shows a bias instability of 0.09°/h and an angular random walk of 0.0015°/√h, with an unlimited dynamic range. This new approach eliminates the need for phase modulation required in I-FOGs, enabling the development of low-cost FOGs for price-sensitive applications, such as autonomous and robotic vehicles.

Interferometric fiber optic gyroscopes (IFOGs) have been in production for many years and for a given size, weight and power it has demonstrated higher performance than other sensors technologies. This is due to the use of relatively long fiber optic coils with small diameter, providing high performance and small size. Several IFOG developers, including Honeywell, are using new error-reduction techniques and improved component technologies to advance the technology. A review of the reported performance advancements will be presented, as well as a discussion of IFOG long life reliability. With new component technologies that are stable performance over life, compensation techniques can be used to further improve gyro performance capability.

The presence of water can provide aqueous electrolytes for corrosion to occur inside the pipelines. The capability of monitoring water vapor condensation enables in-situ monitoring of internal corrosion in natural gas transmission pipelines. Previously, a fully distributed optical fiber sensor for water and humidity monitoring has been demonstrated, consisting of an unmodified off-the-shelf single mode (SM) optical fiber connected to an optical backscatter reflectometer. The intrinsic polymer jacket of the SM fiber is hygroscopic and can serve as a water sensing layer due to expansion/swelling from water absorption. In this work, strain changes were measured and calibrated in jacketed and unjacketed sections at different relative humidity levels (RH, 0% to 100%) and different temperatures (T, 21 to 50°C). In the jacketed section, the sensitivity to humidity decreased from 1.2 to 0.6 με/%RH and then diminished as T increased from 21 to 50 °C, which could be due to the intrinsic absorption property of polymer at higher T or the wet gas flow at room temperature being absorbed in the polymer jacket. The unjacketed section demonstrated a minimal sensitivity to humidity (<0.2 με/%RH) at 21-50 °C and a relatively consistent sensitivity to temperature.

Condition monitoring of power transformers is of great importance for the timely detection of incipient faults to avoid potential malfunctioning. Transformer insulating oil contains about 70% of diagnostic information, and a dramatic rise in oil temperature may drastically reduce the lifetime of power transformers, and thus the temperature of the oil is considered the most crucial parameter that has to be monitored continuously in real-time. Compared to traditional temperature measurement methods used in transformer condition monitoring, distributed optical fiber sensors have inherent advantages of immunity to electromagnetic interference and insulation at high-voltage levels, and they offer spatially resolved temperature monitoring with high accuracy and sensitivity. In this study, optical fiber-based distributed temperature measurement of a fully energized 100 kVA distribution transformer is demonstrated by using two different techniques: Optical Frequency Domain Reflectometry (OFDR) and Fiber Bragg Grating (FBG) sensor array. The fiber sensors are robust for a safe long-term installation into oil-filled distribution transformers during manufacturing, and they can withstand heat runs, long-term hot oil immersion, and transformer vibration. The internal transformer temperature is monitored during standard thermal tests prior to installation on the distribution system. The test results show very good agreement between the standard thermocouple and proposed distributed fiber temperature sensors, providing transformer manufacturers with new insights into the distribution of temperatures internal to their commercial products.

Swept Wavelength Interferometry (SWI) based on Tunable Laser Source (TLS) has various applications in optical measurement and imaging. Nonlinear tuning of the TLS is always a problem in SWI and require proper correction to enhance the spatial resolution and SNR of the signal. Typically, nonlinear tuning correction requires an extra (auxiliary) interferometer. A new type of Optical Frequency Domain Reflectometry (OFDR) arrangement was proposed in which auxiliary interferometer was integrated with the main interferometer and only a single detection channel was used instead of two. This new hardware design eliminated the need for an extra photodetector and an acquisition channel for the auxiliary interferometer. Single trace having beating signal from auxiliary and Rayleigh backscattering from the main interferometer was acquired in a single detection channel. Then the beating signal of the auxiliary interferometer was used to correct nonlinear tuning effects from Rayleigh backscattered signal of the main interferometer. The feasibility of new hardware design is demonstrated by correcting nonlinear tuning effects in a 50 meters long optical fiber and performing distributed strain and temperature sensing in the OFDR technique. Furthermore, an extension of the proposed new design is also described in this paper in which the auxiliary interferometer is replaced by a high reflection event inside the Fiber Under Test (FUT) created by femtosecond laser which makes the overall system design more compact and simpler.

2 μm high power and high performance amplifiers are needed for applications such as LIDAR, remote sensing, and WDM transmission systems. In this paper we report the experimental evaluation of the performance of multistage multiwatt optical amplifiers using a high performance PM single clad Tm-doped fiber. Our amplifier exhibits a large dynamic range ( > 25 dB), a saturated output power > 2 W at 1909 nm, an optical bandwidth from 1875 to 2000 nm, a low noise figure (< 6 dB), a large OSNR (> 50 dB), and a PER > 20 dB.

Fiber laser sources with narrow linewidths in the short-wave infrared and mid-infrared spectral regions have many defense, commercial, and sensing related applications. To generate wavelengths not produced by commercially available lasers, we introduce a compact design of a hollow core fiber-based optical parametric amplifier (OPA) with flexible phase-matching schemes. An electric field applied to fiber core liquids or gases can induce the required effective second-order nonlinearity. Quasi-phase-matching for efficient frequency conversion can be realized by applying spatially periodic electric fields along the length of the fiber. We investigate fiber-based OPA designs with xenon gas and liquids such as carbon disulfide to determine the viability of these architectures for efficient wavelength conversion and flexibility.

Laser spectroscopy outperforms electrochemical and semiconductor gas sensors in selectivity. This talk reports recently development in laser spectroscopic sensors with micro/nano-structured optical fibers, including photothermal, phtotacoustic and Raman gas sensors with outstanding sensitivity and dynamic range.