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Proceedings Paper

Operational performance of the EVLA optical systems LO and IF
Author(s): Steven J. Durand; Roshene McCool
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Paper Abstract

The Expanded Very Large Array (EVLA) uses fiber optic technologies for intermediate frequency (IF) digital data transmission, and local oscillator and reference distribution (LO). These signals are sent on separate fibers to each of the 27 EVLA antennas. The data transmission system transmits the four digitized IF signals from the antennas to the central electronics building. A sustained data rate of 10.24 Gbits/s per channel and 122.88 Gbits formatted per antenna is achieved. Each IF signal uses a set of three channels, twelve channels in total, and is wavelength division multiplexed onto a single fiber. The IF system configuration includes an EML CW laser, an erbium doped fiber amplifier (EDFA), passive optical multiplexers, up to 22 km of standard single mode fiber, and an APD optical receiver. The LO system uses two fibers to provide a round trip phase measurement at 1310 nm. The phase requirement for the LO system requires that a phase stability of less than 2.8 picoseconds per hour at 40 GHz be maintained across the entire array. To accomplish this, a near real-time continuous measurement is made of the phase delay of the amplitude modulated 512 MHz signals that are distributed to each antenna. This information is used by the correlator to set the delay on each of the baselines in the array. This paper presents a complete description of the two EVLA fiber systems, LO and IF, including specific component specifications.

Paper Details

Date Published: 15 September 2004
PDF: 12 pages
Proc. SPIE 5496, Advanced Software, Control, and Communication Systems for Astronomy, (15 September 2004); doi: 10.1117/12.551974
Show Author Affiliations
Steven J. Durand, National Radio Astronomy Observatory (United States)
Roshene McCool, Jodrell Bank Radio Observatory (United Kingdom)

Published in SPIE Proceedings Vol. 5496:
Advanced Software, Control, and Communication Systems for Astronomy
Hilton Lewis; Gianni Raffi, Editor(s)

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