Year-end Sale % OFF 
Abstract
We measured the transmission of tapered and untapered optical fibres as a function of input beam numerical aperture at 635nm. The tapered fibres were fabricated with an adiabatic tapering process from graded and step-index fibres with 50μm core diameters to form a 100mm long taper with 5:1 taper ratio. We tested tapered graded-index and step-index fibres fabricated from commercial Thorlabs products and a custom graded-index taper. The 5:1 tapered graded-index fibre can give a transmission greater than 0.4 for Thorlabs and 0.6 for the custom taper. We simulated the transmission of the tapered fibres and found reasonable agreement with the measured graded-index tapered fibre results across the numerical aperture range of interest. Experimentally, step-index tapered fibres performed relative poorly and considerably below modelling expectations. Based on our examinations this arises because the properties of step-index fibre were not robust to the tapering process. Suitably tapered graded-index fibres may offer a new route for efficient focal ratio reduction of fibre optic signals, e.g., in fibre-fed spectrographs, though we stress that our measurements have been limited to monochromatic light in this work.
Highlights
Optical fibre is renowned for signal transfer with small losses.The versatility of fibre and its relatively low material cost leads to wide usage in astronomical instrumentation for light gathering [1]
Our investigation of fibre transmission versus numerical aperture is principally aimed at quantifying the expected transmission of tapers to be used for optical reformatting for a high resolution fibre-coupled spectrograph
The 5:1 step-index tapered fibre should have transmission greater than 50% for the 0.05 NAeff or at the drop-off numerical aperture according to ouPleaser COMSOL simulations
Summary
Optical fibre is renowned for signal transfer with small losses.The versatility of fibre and its relatively low material cost leads to wide usage in astronomical instrumentation for light gathering [1]. It is possible to fabricate custom fibre tapers, with different taper ratios and transition lengths, from all manner of fibre types, depending on the application. We are developing a prototype high-resolution fibre fed spectrograph named EXOplanet high resolution SPECtrograph (EXOhSPEC) for smaller tele scopes (1–3 m) which is designed for 0.10 Numerical Aperture (0.10 NA) light acceptance and a 10 μm core input fibre. Tapered fibres were formed from the standard bare fibre [7] and custom fibre and include taper ratios of 1.2:1, 2.5:1, 3:1, 4:1 and 5:1. The experi mental details are presented in Section 4 including an explanation of the fibre test setup, the numerical aperture matching technique, trans mission measurement, and experimental error.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
