Effect of near-field distribution on transmission characteristics of fiber-fed Fabry-Perot etalons

TL;DR

This paper investigates how the near-field distribution of the feeding fiber affects the spectral precision of fiber-fed Fabry-Perot etalons, emphasizing the importance of using an octagonal fiber with a double scrambler for high-precision applications.

Contribution

It demonstrates that near-field distribution variations impact spectral accuracy and proposes using octagonal fibers with double scramblers to improve stability in high-precision instruments.

Findings

Near-field distribution variation degrades spectral precision.

Octagonal fiber with double scrambler improves near-field stability.

Recommendations for fiber selection in high-precision spectrographs.

Abstract

Fiber-fed etalons are widely employed in advanced interferometric instruments such as gravitational-wave detectors, ultrastable lasers and calibration reference for high-precision spectrographs. We demonstrate that variation in near-field distribution of the feeding fiber would deteriorate the spectrum precision of the fiber-fed Fabry-Perot etalon, especially when precision at the order of 3 * 10-10 or higher is required. The octagonal fiber reinforced with double scrambler could greatly improve the steadiness and uniformness of the near-field distribution. When building wavelength calibrators for sub-m s-1 precision radial-velocity instruments, the double scrambler should be considered meticulously.