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Proceedings Paper

Receiver front end for optical free space communications
Author(s): Ulrich Hildebrand
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Paper Abstract

The Receiver Front End (RFE) is the optical receiver of ESA's Semiconductor Laser Intersatellite Link Experiment (SILEX). Optical free space communication between satellites is characterized by narrow beams and therefore by demanding requirements for pointing accuracy. This applies for the steering of the laser beam in transmission, for the pointing of the receiver's field of view (FOV), and for the alignment between transmitted and received beams. The RFE housing, the optical system, the lens and detector's mounting have to be designed to meet the stringent requirements for angular stability. This paper concentrates on the mechanical and thermal aspects which strongly influence the performance. Thermal expansion effects are of major concern when keeping the optical axis stable. All materials have been matched to the thermal expansion characteristics of the hybrid circuit which contains the detector. Assuming only homogeneous temperature changes during life, no stress or angular deviations have to be expected. The relative changes of dimensions in any direction stays equal at different temperatures. The verification of opto-mechanical performance requires sophisticated measurement tools. Measurements have to be performed in order to determine the lateral stability of lens and detector. A dedicated autocollimator was developed which measures the angular stability of the optical axis after vibration, thermo-vacuum test and under temperature changes. It also serves as a test transmitter. Measurement accuracies of 5 (mu) rad have been achieved. For the measurements the RFE is mounted onto a test fixture. A reference mirror on the fixture is the stable reference which has to be more stable than the equipment itself.

Paper Details

Date Published: 30 September 1994
PDF: 7 pages
Proc. SPIE 2210, Space Optics 1994: Space Instrumentation and Spacecraft Optics, (30 September 1994); doi: 10.1117/12.188138
Show Author Affiliations
Ulrich Hildebrand, ANT Nachrichtentechnik GmbH (Germany)

Published in SPIE Proceedings Vol. 2210:
Space Optics 1994: Space Instrumentation and Spacecraft Optics
Thierry M. Dewandre; Joachim J. Schulte-in-den-Baeumen; Emmanuel Sein, Editor(s)

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