NASA Technical Reports Server (NTRS) 20110024108: Stabilized Fiber-Optic Distribution of Reference Frequency

1 Pages·0.06 MB·English

by  NASA Technical Reports Server (NTRS)

Stabilized Fiber-Optic Distribution of Reference Frequency
This system includes subsystems that provide NASA’s Jet Propulsion Laboratory,
short- and long-term stabilization. Pasadena, California
An optoelectronic system distributes a
reference signal of low noise and highly sta- Environmentally Controlled Room in SPC
bilized phase and frequency (100 MHz) from
an atomic frequency standard to a remote 100 MHz From SFODA SFODA
facility at a distance up to tens of kilometers. Frequency Master Compensator
The reference signal is transmitted to the Standard Controller Reel
remote station as amplitude modulation of
an optical carrier signal propagating in an
Power Supply for
optical fiber. The stabilization scheme imple- Controlling Temperature
mented in this system is intended particular- Phase of Compensator Reel
Compensation
ly to suppress phase and frequency
fluctuations caused by vibrations and by
expansion and contraction of the optical 16-km Optical Fiber
fiber and other components in diurnal and
seasonal heating and cooling cycles.
The system (see figure) comprises sever- SFODA 1 GHz
al subsystems, the main one being (1) a Remote CSO
Distribution Unit
hydrogen-maser or linear-ion-trap frequen-
100 MHz
cy standard in an environmentally controlled 100 MHz
room in a signal-processing center (SPC),
(2) a stabilized fiber-optic distribution Distribution
assembly (SFODA), (3) a compensated Amplifiers
sapphire oscillator (CSO) in an environmen-
tally controlled room in the remote facility, (4)
thermally stabilized distribution amplifiers To End Users
and cabling from the environmentally con-
Environmentally Controlled Room in Remote Facility
trolled room to end users, and (5) perfor-
mance-measuring equipment. Two of these A Frequency-Standard Signal is transmitted over a long fiber-optic link augmented with
subsystems, considered as separate enti- equipment at both ends that stabilizes the output frequency and phase to a high degree.
ties, were the subjects of prior NASA Tech long-distance optical fiber), signal retransmis- helps to ensure short-term stability. In this
Briefs articles: The SFODA was described sion optics in the remote facility, and equip- system, the 100-MHz signal is first multiplied
in “Improved Stabilization of Delay in an ment in the SPC that measures the overall to 1 GHz before applying it as modulation to
Optical Fiber” (NPO-19353), Vol, 21, No. 2 round-trip propagation delay of the reference the optical carrier. At the remote site, a low-
(February 1997), page 4a; and “Alternative signal and adjusts the temperature of the noise 100-MHz voltage-controlled oscillator
for Stabilization of Delay in an Optical Fiber” compensator-reel to maintain the overall (VCO) that is part of the SFODA is phase-
(NPO-19075), Vol. 21, No. 2 (February propagation delay as nearly constant as locked to the 1-GHz signal to preserve
1997), page 6a. The CSO was described possible. The CSO is a sapphire-dielectric- coherence with the frequency standard. In
in “Temperature-Compensated Sapphire ring microwave resonator that operates in a turn, the CSO is phase-locked to the output
Microwave Resonator” (NPO-19414), “whispering-gallery” electromagnetic mode of the VCO. The cleaned-up signal is then
Vol. 20, No. 3 (March 1996), page 14a. and features a paramagnetic-spin-tuned measured and distributed to end users.
To recapitulate: The SFODA includes the design that provides temperature compen- This work was done by Malcolm
transmitter in which the output of the fre- sation for ultrahigh frequency stability. Calhoun, Robert Tjoelker, William Diener, G.
quency standard is used to modulate the The SFODA and the CSO work in unison John Dick, Rabi Wang, and Albert Kirk of
optical distribution signal, the optical fiber in their environmentally controlled rooms to Caltech for NASA’s Jet Propulsion Lab-
used for long-distance transmission, a com- satisfy stringent requirements for stability of oratory. For further information, access the
pensator reel (a wound, electrically control- frequency and phase: While the SFODA Technical Support Package (TSP) free on-
lable fiber-optic delay line in series with the helps to ensure long-term stability, the CSO line at www.nasatech.comNPO-30490
Delay/Doppler-Mapping GPS-Reflection Remote-Sensing System
This system offers capabilities beyond those of prior NASA’s Jet Propulsion Laboratory,
GPS-reflection remote-sensing systems. Pasadena, California
A radio receiver system that features oped. This system was designed pri- Moreover, it could readily be adapted to
enhanced capabilities for remote sens- marily for ocean altimetry, but can also utilize navigation-satellite systems other
ing by use of reflected Global Positioning be used for scatterometry and bistatic than the GPS, including the Russian
System (GPS) signals has been devel- synthetic-aperture radar imaging. Global Navigation Satellite System
NASA Tech Briefs, January 2003 15