Attenuation measurements on deformed optical fibers

Engelsrath, Amos; Danielson, B. L.; Franzen, Douglas L.

doi:10.6028/nbs.ir.86-3052

Cited by 2 publications

(1 citation statement)

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“…These bends can couple light into previously unrealized modes thus causing dispersion in the fiber's far field. Powell (1984), Engelsrath et al (1986), and Ramsey (1988) find that macrobending on its own has little effect on FRD. The fear is rather that violently macrobending the fiber (such as through agitation) may stress the fiber and cause microbending, a more severe detriment to FRD.…”

Section: Agitation and Frdmentioning

confidence: 99%

Modal Noise Mitigation through Fiber Agitation for Fiber-fed Radial Velocity Spectrographs

Petersburg

McCracken

Eggerman

et al. 2018

ApJ

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Optical fiber modal noise is a limiting factor for high precision spectroscopy signal-to-noise in the near-infrared and visible. Unabated, especially when using highly coherent light sources for wavelength calibration, modal noise can induce radial velocity (RV) errors that hinder the discovery of low-mass (and potentially Earth-like) planets. Previous research in this field has found sufficient modal noise mitigation through the use of an integrating sphere, but this requires extremely bright light sources, a luxury not necessarily afforded by the next generation of high-resolution optical spectrographs. Otherwise, mechanical agitation, which "mixes" the fiber's modal patterns and allows the noise to be averaged over minutes-long exposures, provides some noise reduction but the exact mechanism behind improvement in signal-to-noise and RV drift has not been fully explored or optimized by the community. Therefore, we have filled out the parameter space of modal noise agitation techniques in order to better understand agitation's contribution to mitigating modal noise and to discover a better method for agitating fibers. We find that modal noise is best suppressed by the quasi-chaotic motion of two high-amplitude agitators oscillating with varying phase for fibers with large core diameters and low azimuthal symmetry. This work has subsequently influenced the design of a fiber agitator, to be installed with the EXtreme PREcision Spectrograph, that we estimate will reduce modal-noise-induced RV error to less than 3.2 cm s −1 . arXiv:1802.01642v1 [astro-ph.IM] 5 Feb 2018 Systematic variationsSince the resultant speckle pattern is dependent on dynamic optical properties of the fiber, modal noise can induce false RV's on the spectrograph (Mahadevan et al.

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Section: Agitation and Frdmentioning

confidence: 99%