Polarization data of a SM gyroscope coil may correlate to drift that provides a method to statically predict a
performance range of a coil during manufacturing or at a minimum before integration into a FOG assembly. The
Crossover Free (CF) coils described here are thermally symmetric and lack fiber crossovers. This design allows
possible expansion of depolarized FOGs beyond the research environment. To that end a series of double sided
CF gyroscope coils were manufactured and analyzed using a 4 channel fiber coupled polarimeter. In addition the
coils were tested on a single axis rate table in a FOG testbed. A polarimeter was used to measure the output
polarization state of the stand-alone coils and when integrated into an experimental FOG testbed. In addition
Shupe data of the CF coils was taken to determine the thermal sensitivity of the coils. Coil geometry and
construction, polarimetric and traditional drift data, and Shupe performance will be presented.
The DoD goals for inertial sensors have included achieving high accuracy performance and small size at a low cost. This goal has always been a challenging endeavor, since small size and high accuracy have often been costly and technically difficult to achieve. In 1998, the Army patented a fiber sensor coil winding concept that would facilitate the opportunity to make the Fiber Optic Gyroscope (FOG) more competitive in cost with relation to the commonly-used Ring Laser Gyro (RLG). Recent advances in FOG sensor coil winding techniques appear to show great promise in the improved performance. The novel Crossover-Free (CF) winding technique eliminates fiber crossovers and allows the use of inexpensive single-mode fiber (SMF). Experiments were conducted with the use of an analog, open-loop testbed, which was characterized with a 1 km quadrupolar SM sensor coil. Various sensor coil configurations were spliced into the FOG testbed and bias drift tests were conducted. Different fiber lengths, coil diameters, and fiber wind configurations were evaluated. The Crossover-Free sensor coils were precision wound by a semi-automated Fiber Placement Machine (FPM) developed by Stanley Associates. The Crossover-Free sensor coils test results are compared to standard precision wound coils. The bias errors caused by the fiber crossovers in standard SM sensor coils are also discussed and compared to the near elimination of the crossovers in the CF design.
A fiber optic system intended to perform Structural Health Monitoring (SHM) of composite motor cases has been investigated. The method described here allows for commercial-of-the-shelf (COTS) optical fiber to be integrated into a cylindrical composite motor case prior to cure. The fiber requires no pre-processing before it can be placed inside the composite material. This allows the fiber to act as a distributed sensor not a point sensor as is the case with Bragg gratings and etalons. The distributed nature of the sensor also allows the output data to be naturally multiplexed without the need for complex software or hardware interfaces. After cure the optical fiber can be interrogated to determine a base-line scan of the motor. Subsequent scans can be taken of the motor to determine if damage of a sufficient nature has occurred that would require further investigation or retiring of the motor. In this study optimum wind patterns and proper placement of the optical fiber was investigated. In addition cost reductions of the instrumentation and the practicality of optical fiber egress options were undertaken.