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Strong magnetic fields have the ability to cause apparent drift in the gyro bias. This is due to the Faraday effect on the laser light in the sensing coil resulting in non-reciprocal light paths. While this effect can be observed in gyros designed for precision inertial navigation systems (drift rates of less than 1 degree per hour), and can be mitigated by the use of mu-metal shielding, there have been no reported problems with KVH FOGs. If your application results in mounting a FOG near a very strong magnetic field (>50 gauss), a practical test to determine sensitivity is suggested.

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A rate gyro does not output accumulated angle. Instead, it outputs rate of change of angle. In most KVH FOGs, the users can change the output format as desired; rate integrated angle, or incremental angle.

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All KVH FOG products meet the European Community Electromagnetic Compatibility Directive and are approved to display the CE mark. They have been tested for conformance to electromagnetic emissions and susceptibility requirements. The units also meet FCC Part 15.

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The geometrical birefringence created by the elliptical core is the key to the E-Core fiber's outstanding polarization-maintaining abilities. Because of its design, it is able to maintain its polarization and low-loss characteristics when exposed to physical stresses and temperature-induced changes far better than PM fiber created using stress-induced birefringence. It is the E-Core fiber's stability that makes it an excellent choice for pigtailing optical components.
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Please see the installation and technical manual for your KVH FOG-based product for complete details of any specific power requirements.
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KVH's E-Core fiber offers a number of advantages, including high polarization maintaining ability (greater than 40 dB-m) and low sensitivity to stress and temperature. These features make E-Core fiber ideal for fiber splicing and pigtailing to other optical components in applications where preserving the state of light polarization is critical to the operation of the device.

The geometrical birefringence created by the elliptical core is the key to the E-Core fiber's outstanding polarization-maintaining abilities. Because of its design, it is able to maintain its polarization and low-loss characteristics when exposed to physical stresses and temperature-induced changes far better than PM fiber created using stress-induced birefringence. It is the E-Core fiber's stability that makes it an excellent choice for pigtailing optical components.

The elliptically shaped core region within an E-Core fiber has a significantly higher index than the surrounding cladding, creating the geometrical birefringence necessary to maintain the polarization of the light within the fiber. The E-Core fibers are manufactured using high-grade silica materials and various high-purity dopants. A dual UV-cured acrylate coating is applied to standard fibers, thereby preventing moisture from penetrating the fiber, preserving its strength, and improving its handling characteristics.
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The output of a fiber optic gyro contains a broadband random noise component (sometimes called "white noise") which may result either from "shot noise" or thermal noise in the photodetector. Within the gyro output bandwidth, the noise power spectral density is flat. Two equivalent units of measurement are used to describe this performance: "deg/sq.rt.-hr" or "deg/hr/sq.rt.-Hz." The conversion factor between the two is a factor of 60, and we prefer the latter unit since it directly relates the noise power to the processing bandwidth.

The output bandwidth of our gyro is set in the signal processing electronics to 100 Hz; the random noise decreases as the bandwidth is narrowed in any subsequent signal processing, with the noise decreasing as the inverse of the square root of the integration time (Alternately, the noise is proportional to the square root of the effective bandwidth). The digital output version integrates the gyro signal for 0.1 second before analog-to-digital conversion, improving the noise performance by 3.33 with respect to the analog version, without reducing the instantaneous bandwidth. A user can accomplish the same thing by integrating the analog version output for 0.1 second. The full analog gyro output bandwidth may be necessary for dynamic applications where the angular rate change is rapid or the phase response is critical, as in servo control applications.

The ARW can be measured simply by determining the root-mean-square (RMS) signal output value in the 100 Hz bandwidth, dividing by 10 (sq. root of 100) and interpreting it as an angular rate by applying the scale factor (deg/sec/mv). A more sophisticated method of determining the ARW is the Allan variance method described in IEEE Std. 647-1995.
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Bias instability is the fluctuation in indicated angle rate at a constant temperature when the gyro is not rotating. This term is sometimes called bias drift, but sometimes what is meant is the Bias Offset described later. For short data samples, it is not usually possible to determine the Bias Instability as it is masked by the Angle Random Walk. For a fiber optic gyro, bias instability is a zero mean process, and the value quoted in the specification is the RMS. Along with ARW, this fluctuation in bias places a lower limit on the accuracy to which the Bias Offset can be measured, since the bias will wander during the integration time necessary to estimate the Bias Offset accurately. Measurement of this parameter is done at room temperature with a long time series of data subjected to Allan variance.
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The Bias Offset is the apparent rotation rate when the gyro is not rotating about its sensitive axis (In precision applications, the user should note that the gyro does measure rotation in inertial space, and the gyro may be measuring a component of the Earth's rotation, of up to 15 deg/hr). The E-Core 1000 is a low-cost product, and uses analog components in the signal processing electronics. There are temperature-dependent offsets in some of the circuits, and this results in a deterministic relationship between bias offset and temperature for each gyro. Bias Offset is the long-term mean indicated rate at a constant temperature when the gyro is not rotating.

The gyro has a temperature sensor whose output is available in both the analog and digital versions. In a land navigation application, the bias offset can be estimated by measuring the apparent rotation rate when the vehicle is stationary. This can be subtracted from the gyro output to yield the true rotation rate. The accuracy of the estimate is dependent on the ARW, since the measurement will have a noise component for short times.
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The deviation from the best fit straight line through the input rate-indicated rate data. We describe this in percentage of full-scale reading. The attached figure shows the input-output relationship of the gyro, which is desired to be a straight line, and the percentage error as a function of input rate.
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