scholarly journals Starlight coupling through atmospheric turbulence into few-mode fibres and photonic lanterns in the presence of partial adaptive optics correction

2020 ◽  
Vol 501 (2) ◽  
pp. 1557-1567
Author(s):  
Momen Diab ◽  
Aline N Dinkelaker ◽  
John Davenport ◽  
Kalaga Madhav ◽  
Martin M Roth
Keyword(s):  
Atmospheric Turbulence ◽  
Adaptive Optics ◽  
Degrees Of Freedom ◽  
Signal To Noise Ratio ◽  
Spatial Coherence ◽  
Single Mode ◽  
Cost Effective ◽  
Single Mode Fibre ◽  
Astronomical Instruments ◽  
Efficient Coupling

ABSTRACT Starlight corrupted by atmospheric turbulence cannot couple efficiently into astronomical instruments based on integrated optics as they require light of high spatial coherence to couple into their single-mode waveguides. Low-order adaptive optics in combination with photonic lanterns offer a practical approach to achieve efficient coupling into multiplexed astrophotonic devices. We investigate, aided by simulations and an experimental testbed, the trade-off between the degrees of freedom of the adaptive optics system and those of the input waveguide of an integrated optic component leading to a cost-effective hybrid system that achieves a signal-to-noise ratio higher than a standalone device fed by a single-mode fibre.

scholarly journals Final design and on-sky testing of the iLocater SX acquisition camera: broad-band single-mode fibre coupling

2020 ◽  
Vol 501 (2) ◽  
pp. 2250-2267
Author(s):  
J Crass ◽  
A Bechter ◽  
B Sands ◽  
D King ◽  
R Ketterer ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Broad Band ◽  
Single Mode ◽  
Injection System ◽  
Single Mode Fibre ◽  
Astronomical Instruments ◽  
Final Design ◽  
Camera Design ◽  
And Performance

ABSTRACT Enabling efficient injection of light into single-mode fibres (SMFs) is a key requirement in realizing diffraction-limited astronomical spectroscopy on ground-based telescopes. SMF-fed spectrographs, facilitated by the use of adaptive optics (AO), offer distinct advantages over comparable seeing-limited designs, including higher spectral resolution within a compact and stable instrument volume, and a telescope independent spectrograph design. iLocater is an extremely precise radial velocity (EPRV) spectrograph being built for the Large Binocular Telescope (LBT). We have designed and built the front-end fibre injection system, or acquisition camera, for the SX (left) primary mirror of the LBT. The instrument was installed in 2019 and underwent on-sky commissioning and performance assessment. In this paper, we present the instrument requirements, acquisition camera design, as well as results from first-light measurements. Broad-band SMF coupling in excess of 35 per cent (absolute) in the near-infrared (0.97–1.31 ${\mu {\rm m}}$) was achieved across a range of target magnitudes, spectral types, and observing conditions. Successful demonstration of on-sky performance represents both a major milestone in the development of iLocater and in making efficient ground-based SMF-fed astronomical instruments a reality.

scholarly journals New optical fibres for high-capacity optical communications

2016 ◽  
Vol 374 (2062) ◽  
pp. 20140441 ◽  
Author(s):  
D. J. Richardson
Keyword(s):  
High Capacity ◽  
Single Mode ◽  
Cost Effective ◽  
Network Capacity ◽  
Optical Fibres ◽  
Single Mode Fibre ◽  
Fibre Transmission ◽  
Fibre Amplifiers ◽  
Fibre Loss ◽  
Mode Fibre

Researchers are within a factor of 2 or so from realizing the maximum practical transmission capacity of conventional single-mode fibre transmission technology. It is therefore timely to consider new technological approaches offering the potential for more cost-effective scaling of network capacity than simply installing more and more conventional single-mode systems in parallel. In this paper, I review physical layer options that can be considered to address this requirement including the potential for reduction in both fibre loss and nonlinearity for single-mode fibres, the development of ultra-broadband fibre amplifiers and finally the use of space division multiplexing.

scholarly journals Replicated spectrographs in astronomy

2014 ◽  
Vol 3 (3) ◽  
Author(s):  
Gary J. Hill
Keyword(s):  
Adaptive Optics ◽  
Large Scale ◽  
Mechanical Stability ◽  
Cost Effective ◽  
Lessons Learned ◽  
Full Potential ◽  
Astronomical Instruments ◽  
Very Large Telescope ◽  
Small Fields ◽  
Future Technologies

AbstractAs telescope apertures increase, the challenge of scaling spectrographic astronomical instruments becomes acute. The next generation of extremely large telescopes (ELTs) strain the availability of glass blanks for optics and engineering to provide sufficient mechanical stability. While breaking the relationship between telescope diameter and instrument pupil size by adaptive optics is a clear path for small fields of view, survey instruments exploiting multiplex advantages will be pressed to find cost-effective solutions. In this review we argue that exploiting the full potential of ELTs will require the barrier of the cost and engineering difficulty of monolithic instruments to be broken by the use of large-scale replication of spectrographs. The first steps in this direction have already been taken with the soon to be commissioned MUSE and VIRUS instruments for the Very Large Telescope and the Hobby-Eberly Telescope, respectively. MUSE employs 24 spectrograph channels, while VIRUS has 150 channels. We compare the information gathering power of these replicated instruments with the present state of the art in more traditional spectrographs, and with instruments under development for ELTs. Design principles for replication are explored along with lessons learned, and we look forward to future technologies that could make massively-replicated instruments even more compelling.

scholarly journals An all-photonic focal-plane wavefront sensor

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Barnaby R. M. Norris ◽  
Jin Wei ◽  
Christopher H. Betters ◽  
Alison Wong ◽  
Sergio G. Leon-Saval
Keyword(s):  
Adaptive Optics ◽  
Focal Plane ◽  
Mean Squared Error ◽  
Single Mode ◽  
Wavefront Sensor ◽  
Wavefront Sensors ◽  
Single Mode Fibre ◽  
Squared Error ◽  
Wavefront Error ◽  
Plane Wavefront

Abstract Adaptive optics (AO) is critical in astronomy, optical communications and remote sensing to deal with the rapid blurring caused by the Earth’s turbulent atmosphere. But current AO systems are limited by their wavefront sensors, which need to be in an optical plane non-common to the science image and are insensitive to certain wavefront-error modes. Here we present a wavefront sensor based on a photonic lantern fibre-mode-converter and deep learning, which can be placed at the same focal plane as the science image, and is optimal for single-mode fibre injection. By measuring the intensities of an array of single-mode outputs, both phase and amplitude information on the incident wavefront can be reconstructed. We demonstrate the concept with simulations and an experimental realisation wherein Zernike wavefront errors are recovered from focal-plane measurements to a precision of 5.1 × 10−3 π radians root-mean-squared-error.

scholarly journals Fibered visible interferometry and adaptive optics: FRIEND at CHARA

2018 ◽  
Vol 618 ◽  
pp. A153 ◽  
Author(s):  
M. A. Martinod ◽  
D. Mourard ◽  
P. Bério ◽  
K. Perraut ◽  
A. Meilland ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Signal To Noise Ratio ◽  
Binary Star ◽  
Coupling Efficiency ◽  
Stable Solution ◽  
Angular Separation ◽  
Single Mode ◽  
Excess Noise ◽  
High Angular Resolution ◽  
Visible Wavelengths

Aims. In the context of the future developments of long baseline interferometry at visible wavelengths, we have built a prototype instrument called Fibered spectrally Resolved Interferometer – New Design (FRIEND) based on single mode fibers and a new generation detector called Electron Multiplying Charge-Coupled Device (EMCCD). Installed on the Center for High Angular Resolution Astronomy (CHARA) array, it aims to estimate the performance of a fibered instrument in the visible when coupled with telescopes equipped with adaptive optics (AO) in partial correction. Methods. We observed different sequences of targets and reference stars to study the compensation of the birefringence of the fibers, the coupling efficiency in various conditions of correction, and to calibrate our numerical model of signal-to-noise ratio (S/N). We also used a known binary star to demonstrate the reliability and the precision of our squared visibility and closure phase measurements. Results. We firstly present a reliable and stable solution for compensating the birefringence of the fibers with an improvement of a factor of 1.5 of the instrumental visibility. We then demonstrate an improvement by a factor of between 2.5 and 3 of the coupling efficiency when using the LABAO systems in closed loop. The third results of our paper is the demonstration of the correct calibration of the parameters of our S/N estimator provided the correct excess noise factor of EMCCD is correctly taken into account. Finally with the measurements of the angular separation, difference of magnitude and individual diameters of the two components of ζ Ori A, we demonstrate the reliability and precision of our interferometric estimators, and in particular a median residual on the closure phase of 1.2°.

Line-plant considerations for the optical local network

1989 ◽  
Vol 329 (1603) ◽  
pp. 61-70 ◽  
Keyword(s):  
Low Cost ◽  
Single Mode ◽  
Cost Effective ◽  
Single Fibre ◽  
Local Network ◽  
Local Networks ◽  
Single Mode Fibre ◽  
All Optical ◽  
Line Plant ◽  
Technical Solutions

Recent proposals for future local networks have focused on all-optical solutions that use single-mode fibre. Increasingly, these networks attempt to become cost-effective against copper-based solutions by sharing a single fibre among several subscribers, using either electronic or optical multiplexing. The line plant for such systems must be able to carry wide-bandwidth transmission over a large range of wavelengths. Attempts to keep all of the line plant passive (for example, splitter-based networks) typically result in a need for low-loss components, and bidirectional working and coherent transmission place constraints on reflection levels from line-plant components. Throughout all this, component solutions must remain low cost and be easily installed, maintained and tested by personnel currently installing copper pairs. In addition, the fibre-sharing aspect typically means that line-plant systems must be tested while ‘live’, without disturbing the transmission links on them. This paper discusses the line plant for future local networks within these constraints, and presents various technical solutions to the challenge ahead. 12

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