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Expansion of multi-rate capabilities for agile DPSK lasercom transceivers (Conference Presentation)
Author(s): David O. Caplan; P. Stephan Bedrosian; Jade P. Wang
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Paper Abstract

Flexible multi-rate capabilities are attractive for communications over the dynamic free-space optical (FSO) channel since it enables links to be efficiently established over a variety of distances, channel conditions, aperture sizes, and transmitter power levels. Recently, multi-rate differential phase shift keying (DPSK) modulation has been shown to provide good performance with modest complexity over a wide range of data rates. For these reasons, multi-rate DPSK has become the high-rate baseline format for NASA’s Laser Communication Relay Demonstration (LCRD) and other space-based FSO systems currently in development, operating at channel rates from 72 Mbit/s to 2.88 Gbit/s. Here, we report WDM-scalable power-efficient optical-transceiver advances that can extend single-channel rates by a factor of four to 11.52 Gbit/s using LCRD-compatible waveforms. Transmitter waveforms are implemented using time-frequency-windowed directly modulated lasers (DMLs) that can generate burstmode 2-DPSK and 4-DPSK waveforms at the standard LCRD 2.88 GHz symbol rate and twice the rate at 5.76 GHz. At the receiver, standard 2.88 GHz delay-line-interferometer (DLI) based demodulation is implemented for 2-DPSK. For 4-DPSK, a second 2.88 GHz DLI is required to demodulate the 2-bit-persymbol format, with the pair of DLIs biased at ±/4. With proper precoding of the transmitter waveforms, the double-rate 5.76 GHz symbols may be demodulated using the same 2.88 GHz DLIs using non-adjacent DPSK demodulation. In this manner, a common DPSK receiver platform may be used to demodulate standard multi-rate LCRD waveforms as well as 4-DSPK waveforms at 1x and 2x the standard symbol rate.

Paper Details

Date Published: 4 March 2019
Proc. SPIE 10910, Free-Space Laser Communications XXXI, 1091010 (4 March 2019); doi: 10.1117/12.2510630
Show Author Affiliations
David O. Caplan, MIT Lincoln Lab. (United States)
P. Stephan Bedrosian, MIT Lincoln Lab. (United States)
Jade P. Wang, MIT Lincoln Lab. (United States)

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

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