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Proceedings Paper

Simultaneous quadrature detection of suppressed-carrier weak-coherent-states using a homodyne optical Costas loop receiver
Author(s): J. A. López; E. García; F. J. Mendieta; A. Arvizu; Phillipe Gallion
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Paper Abstract

Weak coherent states (WCS) are being extensively employed in quantum communications and cryptography at telecommunications wavelengths. For these low-photon-number applications, simultaneous field quadrature measurements are frequently required, such as in the detection of multilevel modulations in the communications scenario or in cryptographic applications employing continuous variables. For this task multiport balanced homodyne detection (BHD) structures are employed, based on the splitting of the received field into its (non-commutating) in-phase (I) and quadrature (Q) components and their separate beating with a local oscillator (LO) in two BHD. This allows the simultaneous measurements of the 2 quadratures at the price of an additional noise due to the vacuum fields that leak via the unused ports. These schemes require the proper optical phase synchronization between the LO and the incoming field, which constitutes a challenge for WCS reception, especially for suppressed carrier modulations that are required for power economy. For this task, a Costas loop is implemented for low photon number WCS, with the design of an optimum feedback scheme considering the phase diffusion of WCS generated by semiconductor lasers. We implemented an optical Costas loop at 1550 nm based on polarization splitting of the laser field to detect I and Q quadratures simultaneously. We present results on the performance in phase error and bit error rate and compare with corresponding quantum limit.

Paper Details

Date Published: 6 September 2011
PDF: 9 pages
Proc. SPIE 8163, Quantum Communications and Quantum Imaging IX, 81630E (6 September 2011);
Show Author Affiliations
J. A. López, Ctr. de Investigación Científica y de Educación Superior de Ensenada (Mexico)
E. García, Univ. Autónoma de Baja California (Mexico)
F. J. Mendieta, Ctr. de Investigación Científica y de Educación Superior de Ensenada (Mexico)
A. Arvizu, Ctr. de Investigación Científica y de Educación Superior de Ensenada (Mexico)
Phillipe Gallion, Telecom ParisTech (France)

Published in SPIE Proceedings Vol. 8163:
Quantum Communications and Quantum Imaging IX
Ronald E. Meyers; Yanhua Shih; Keith S. Deacon, Editor(s)

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