Fiber Optic Reference Frequency Distribution to Remote Beam Waveguide Antennas
CALIFORNIA INST OF TECHNOLOGY PASADENA JET PROPULSION LAB
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In the NASAJPL Deep Space Network DSN, radio science experiments probing outer planet atmospheres, rings, gravitational waves, etc. and very long-base interferometry VLBI require ultra-stable, low phrase noise reference frequency signals at the user locations. Typical locations for radio scienceVLBI exciters and down-converters are the cone areas of the 34 m high efficiency antennas or the 70 m antennas, located several hundred meters from the reference frequency standards. Over the past three years, fiber optic distribution links have replaced coaxial cable distribution for reference frequencies to these antenna sites. Optical fibers are the preferred medium for distribution because of their low attenuation, immunity to EMIRFI, and temperature stability. A new network of Beam Waveguide BWG antennas presently under construction in the DSN requires hydrogen maser stability at tens of kilometers distance from the frequency standards central location. The topic of this paper is the design and implementation of an optical fiber distribution link which provides ultra-stable reference frequencies to users at a remote BWG antenna. The temperature profile from the earths surface to a depth of six feet over a time period of six months was used to optimize the placement of the fiber optic cables. In-situ evaluation of the fiber optic link performance indicates Allan deviation on the order of parts in 10-15 at 1000 and 10,000 seconds averaging time thus, the link stability degratlation due to environmental conditions still preserves hydrogen maser stability at the user locations. This paper reports on the implementation of optical fibers and electro-optic devices for distributing very stable, low phase noise reference signals to remote BWG antenna locations. Allan deviation and phase noise test results for a 16 km fiber optic distribution link are presented in the paper.
- Fiber Optics and Integrated Optics