<title>Proton-induced degradation in interferometric fiber optic gyroscopes</title>

Abstract

Recent advances in Interferometric Fiber Optic Gyroscope (IFOG) technology have enabled these devices to equal, and in some respects exceed, the performance of the floated, spinning wheel rate integrating gyroscope. However, their ability to perform in a space radiation environment has been a significant concern. Test results are presented addressing the effects of space radiation on the performance of a high precision pointing grade IFOG. Proton induced degradation of the optical components of an IFOG is evaluated based on testing performed at the Harvard Cyclotron Laboratory (HCL). Rationale is provided for using the HCL proton accelerator as a reasonable simulation of the space environment. An analysis is presented which prioritizes the component-level dose tests based on expected radiation sensitivities. The evaluation addresses both total dose (to about 12 had) and dose rate effects. Testing was performed at the component level as well as the system level with an expanded version of a closed-loop operational IFOG. Primary concerns include permanent attenuation and spectral transmission (wavelength) sensitivity to total dose, and angle random walk and bias stability degradation as a function of dose rate. Component level results are presented for a superfluorescent light source, integrated optics chip (bC), coupler and polarization maintaining fiber coils. Closed-loop transient noise results are evaluated based on dose rate testing of the IOC, coupler, and fiber coil. Keywords: Fiber-optic gyroscope, protons, radiation effects, superfiourescent source, photonic components, space systems 120/SPIE Vol. 2482 O-8194-1835-8/95/$6.OO Downloaded From: http://proceedings.spiedigitallibrary.org/ on 07/13/2015 Terms of Use: http://spiedl.org/termsapplications it is necessary to understand the limitations of IFOG performance under typical space radiation environments. In this paper we attempt to gain such an understanding empirically. We report the results of proton-induced degradation studies performed on a variety of key IFOG components. In addition, an expanded version of a closed-loop operational IFOG was characterized while being irradiated by protons.These characterizations were carried-out at the Harvard Cyclotron Laboratory (HCL) in Cambridge, Massachusetts, using a proton accelerator to simulate the space radiation environment.Section 2 provides a brief overview of important aspects of the space radiation environment and its attenuation based on plausible spacecraft shielding. The rationale for choosing proton-irradiation as a means of emulating the space environment is discussed. Section 3 provides an analysis of the sensitivities of overall IFOG performance to expected proton-induced degradation of IFOG components, which is used to select and prioritize the specific test cases. Section 4 discusses the methodology of the component-level proton dose and dose-rate dependent testing based on the priorities established in section 3 and includes a description of the methodology for measuring the proton sensitivity ...

Effect of radiation-induced mean wavelength shift in optical fibers on the scale factor of an interferometric fiber optic gyroscope at a wavelength of 1300 nm

“…[8] Boucher et al tested the change of wavelength centroid with time for a fiber coil during proton irradiation and showed a steady shift in wavelength. [6] However, as the authors themselves pointed out, the influence of temperature on the light source wavelength shift is not eliminated in this study, which made it ambiguous whether the observed optical wavelength shift resulted from the imposed radiation or just from light source drift. In addition, the effect of dose rate on the MWS is not studied, which precludes the prediction of wavelength shift in a space environment.…”

Influence of Self‐Trapped Holes on the Responses of Fluorine‐Doped Multimode Optical Fibers Exposed to Low Fluences of Protons

“…For space applications, γ‐rays are commonly used for qualification due to their low‐cost and availability compared to proton facilities. However, for earth‐bound applications, Boucher et al showed that the environment seen by photonic components, such as fiber‐optic gyros or data links, will be dominated by energetic protons . If most of the fiber‐related applications for space deal with systems operating at the infrared 1310 nm and 1550 nm telecom wavelengths, an increasing variety of applications necessitate optical fibers operating in the visible and near‐infrared range domains.…”