Results for a high efficiency fibre double-scrambler are reported. The scrambler is based on the concept first presented by Casse and Vieira (1997) but with a substantial improvement in performance. The design uses a simple finite conjugate relay with large magnification followed by a combined scrambler/focal reducer singlet. This approach allows flexibility in the coupling of fibres with various focal ratios and diameters, and can be used to minimize loss of throughput due to focal ratio degradation. A prototype has been constructed using simple off-the-shelf optics which is shown to be capable of coupling a 15m long 300 μm fibre to a 5m long 320 μm fibre with an absolute efficiency of 75%. The focal ratio degradation (FRD) of the prototype is 7% when operated at f/3.65. A fully optimized version with both improved efficiency (>85%) and FRD is intended to be deployed as part of the Hobby Eberly Telescope HRS upgrade.

Date Published: 20 July 2010
PDF: 10 pages
Proc. SPIE 7735, Ground-based and Airborne Instrumentation for Astronomy III, 773567 (20 July 2010); doi: 10.1117/12.857945

Published in SPIE Proceedings Vol. 7735:
Ground-based and Airborne Instrumentation for Astronomy III
Ian S. McLean; Suzanne K. Ramsay; Hideki Takami, Editor(s)