Stabilization of a Fiber-Optic Link Using a Temperature Controlled Fiber Segment

Richard L. Sydnor, Malcolm Calhoun, Jerry Lopez, William Diener

Abstract:	The Deep Space Network (DSN) of the National Aeronautics and Space Administration (NASA) is operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology. The DSN uses fiber optics to distribute frequency and time to remote sites that may be as far as 32 kilometers from the Signal Processing Center (SPC) which contains the frequency standards and master clock. The fiber-optic cables are buried 1.5 meters underground. At this depth, the only apparent temperature variations are those due to the annual cycle having a pseudo-sinusoidal behavior with a 1-year period and a diurnal cycle that is greatly reduced due to the insulation of the earth. Some variation is also caused by the air-conditioning cycling of the fiber-optic cable temperature in the plena of the buildings and the lengths of cable that are in the manhole vaults along the run. The resulting stability of the references at the remote site is well within the requirements of the DSN. However, the radio science requirements for the Cassini mission are much more stringent than the DSN requirements and the existing performance does not meet these requirements. The particular antenna (DSS-25) to be used for the 32 GHz portion of the Mini radio science mission is 17 kilometers from the main control center and the apparent temperature variation (as measured by the delay variation) is 11°C peak to peak over the annual cycle. By inserting a temperature-controlled section of fiber-optic cable whose temperature is controlled in such a manner as to force the total delay to be constant, the annual variation (and small variations due to storm fronts passing through the arm) can be reduced to a negligible amount. The length of this inserted fiber-optic section is > 3.74 kilometers and the temperature variation of this section over the year is 50'C. Details of the the sign and preliminary results are given.
Published in:	Proceedings of the 28th Annual Precise Time and Time Interval Systems and Applications Meeting December 3 - 5, 1996 Hyatt Regency Reston Town Center Reston, Virginia
Pages:	163 - 168
Cite this article:	Sydnor, Richard L., Calhoun, Malcolm, Lopez, Jerry, Diener, William, "Stabilization of a Fiber-Optic Link Using a Temperature Controlled Fiber Segment," Proceedings of the 28th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, December 1996, pp. 163-168.
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