Semi-automated single-mode fiber coupling for AO-fed spectrographs
Abstract
Conventional astronomical spectrographs are seeing-limited and commonly use multimode fibers to inject starlight into downstream optics. Forthcoming Doppler radial-velocity (RV) instruments are expected to make increasing use of adaptive optics and smaller single-mode fibers (SMF), enabling higher spectral resolution and improved stabilization of the spectrograph point-spread function. However, coupling starlight into SMFs with characteristic diameters of only 5-10 microns at near-infrared wavelengths is technically demanding, requiring alignment procedures that are both efficient and stable throughout the duration of an observation. In this paper, we describe a semi-automated SMF coupling control program being developed for diffraction-limited RV spectrographs. Representative simulations demonstrate that the controller reduces the star-fiber separation from approximately 3.9 mode field diameters (MFD) to 0.11 MFD while increasing a normalized coupling metric from zero to values near 0.6-0.8 after acquisition. Application to closely-separated binary stars is also studied.
Related
- Automated multi-stressor optical fiber focal ratio degradation and throughput characterization system for future massive multiplex spectroscopic survey
- Coupling loss and transmission in a multimode fiber-fed virtually imaged phased array (VIPA)
- Design of an atmospheric dispersion corrector and double scrambler for improved fiber coupling and illumination uniformity for the HET HRS
- Community Lessons from builders of infrared multi-object spectrographs
- Characterization and on-sky testing of photonic, AWG-based astronomical spectrographs
BibTeX
@misc{crepp2026semiautomated,
title = {{Semi-automated single-mode fiber coupling for AO-fed spectrographs}},
author = {Aaron J. Crepp and Brian L. Sands and Justin R. Crepp},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.19978},
eprint = {2609.19978},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.19978},
}
RIS
TY - UNPB
TI - Semi-automated single-mode fiber coupling for AO-fed spectrographs
AU - Aaron J. Crepp
AU - Brian L. Sands
AU - Justin R. Crepp
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.19978
UR - https://arxiv.org/abs/2609.19978
AB - Conventional astronomical spectrographs are seeing-limited and commonly use multimode fibers to inject starlight into downstream optics. Forthcoming Doppler radial-velocity (RV) instruments are expected to make increasing use of adaptive optics and smaller single-mode fibers (SMF), enabling higher spectral resolution and improved stabilization of the spectrograph point-spread function. However, coupling starlight into SMFs with characteristic diameters of only 5-10 microns at near-infrared wavelengths is technically demanding, requiring alignment procedures that are both efficient and stable throughout the duration of an observation. In this paper, we describe a semi-automated SMF coupling control program being developed for diffraction-limited RV spectrographs. Representative simulations demonstrate that the controller reduces the star-fiber separation from approximately 3.9 mode field diameters (MFD) to 0.11 MFD while increasing a normalized coupling metric from zero to values near 0.6-0.8 after acquisition. Application to closely-separated binary stars is also studied.
ER -