Coupling starlight into single-mode fiber optics

Abstract

We have calculated the efficiency with which starlight can be coupled into a single-mode fiber optic that is placed in the focal plane of a telescope. The calculations are performed for a wide range of seeing conditions, with and without rapid image stabilization, and for a wide range of wavelengths. The dependence of coupling efficiency on the f-ratio of the incident beam is explored. Also, we calculate the coupling efficiency as a function of displacement for a perfect Airy pattern. We have also used a computer program which simulates atmospheric wavefronts to determine the variance of instantaneous coupling efficiency as a function of seeing. In perfect conditions, the maximum efficiency at the LP(11) mode cutoff is 78% due to the mismatch of the Airy pattern and the nearly Gaussian mode of the fiber. Maximum total coupled power is attained at d/r(0) = 4 with rapid image stabilization.

Photonic lanterns

“…Mainstream astronomy has generally avoided single-mode fibers because of the difficulty of coupling light into these efficiently. Even the best performing adaptive optics systems, which attempt to deliver a diffraction-limited beam, are unable to couple light efficiently into the Gaussian-like mode of single-mode fibers below 2500 nm [3,28,29]. Consequently, astronomers have been unable to exploit numerous technological advances in photonics over the past three decades, as these have almost entirely been based on single-mode telecommunications fiber.…”

“…Large-core multimode fibers were used in order to maximize the light captured at the telescope focal plane while matching the field of view of the investigated objects. Subsequently, in the 1990s, single-mode fibers found important uses in astronomical interferometers as a way of filtering the noisy input signal and combining the signal of multiple telescopes or apertures [3][4][5]. However, for multimode fibers, more complex forms of light manipulation were not considered until only a decade ago in the context of complex filters that were being developed to suppress noise in the form of hundreds of narrow-frequency emission lines from the Earth's atmosphere.…”

FIRST, a fibered aperture masking instrument

“…The total efficiency is deduced from data taken on Vega by comparing the number of photons expected from the stellar spectrum in the 600−760 nm range to the number of counts measured on the detector in 200 ms. Telescope, AO transmission and FIRST optics transmission have been estimated with the theoretical transmission and reflection coefficients. An upper value of the fiber injection efficiency has been obtained by assuming that injection losses are due to residual tip-tilt, mode mismatch (a 22% loss according to Shaklan & Roddier 1988), and high order phase perturbations.…”

Estimating the phase in groundbased interferometry: performance comparison between singlemode and multimode schemes

“…and where ρ 0 is the maximum achievable coupling efficiency, shown to be ∼80% (Shaklan & Roddier 1988), because of the geometrical mismatch between the telescope Airy disk profile and the Gaussian profile of the propagated mode. Equation (8) has to be compared with Eq.…”

“…The coupling coefficients, for the photometric (ρ 1 (V), ρ 2 (V)), and interferometric (ρ 12 (V)) channels respectively write (Mège et al 2003;Tatulli et al 2004) .36) where S 0 1 ( f ), S 0 2 ( f ) are the photometric transfer functions of a perfect (atmosphere-free) interferometer, and ρ 0 the maximum coupling efficiency, shown to be ∼80% (Shaklan & Roddier 1988). And the singlemode interferometric equation writes: A.37) where H 1 ( f ), H 2 ( f ) and H 12 ( f ) are the normalized (i.e.…”