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Optical software defined radio transmitter extinction ratio enhancement with differential pulse carving
Author(s): Nicholas C. Lantz; Jennifer M. Nappier; Brian E. Vyhnalek; Sarah A. Tedder
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Paper Abstract

The purpose of this study is to investigate a new approach to the modulation of an optical signal which requires high extinction ratio (ER). A deep space, optical, pulse position modulated (PPM) link, may require an extinction ratio approaching 33 dB1 which is not easily achieved through the use of a single optical modulator. In a system where the slot clock is equal to the slot width, it is often not possible to meet ER requirements due to Inter Slot Interference (ISI). Furthermore, the high frequency ER of state of the art optical amplitude modulators is not large enough to allow for implementation losses. By using a second optical modulator in series with the first, it is possible to address both issues. A phase delay placed between each modulator allows for precision control of the pulse width, reducing ISI. While the attenuation in the off slots combines linearly, increasing attenuation in the off slots. Using this approach a series of 1 ns pulses was measured at a series of phase delays to approximate PPM pulses. These measurements were used to extrapolate the ER of a PPM signal at various PPM orders. An ER above 33 dB was observed for all PPM orders of 16 and above. At PPM 256 an ER of 48.2 dB was achieved.

Paper Details

Date Published: 21 March 2019
PDF: 9 pages
Proc. SPIE 10910, Free-Space Laser Communications XXXI, 109101Q (21 March 2019); doi: 10.1117/12.2509874
Show Author Affiliations
Nicholas C. Lantz, NASA Glenn Research Ctr. (United States)
Jennifer M. Nappier, NASA Glenn Research Ctr. (United States)
Brian E. Vyhnalek, NASA Glenn Research Ctr. (United States)
Sarah A. Tedder, NASA Glenn Research Ctr. (United States)

Published in SPIE Proceedings Vol. 10910:
Free-Space Laser Communications XXXI
Hamid Hemmati; Don M. Boroson, Editor(s)

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