Ronald T. Logan

Stabilization of oscillator phase using a fiber-optic delay-line

The authors describe an electronic oscillator phase stabilizer based on a fiber-optic delay-line. Excellent agreement between calculated and first experimental results was obtained for this fiber-optic stabilized electronic oscillator (FOSO) at 100 MHz and 7.8 GHz. Expressions are derived for the FOSO phase noise performance and optimum fiber length, based on the noise contributions of the various components. The predicted performance of the FOSO expected with improved system components is also calculated. The FOSO is tunable over an extremely wide frequency range, with phase noise performance rivaling that of good resonant-cavity stabilized oscillators, which are constrained to narrowband operation.<<ETX>>

Applications of ultra-stable fiber optic distribution systems

Present and future applications of fiber-optic frequency distribution systems are discussed and it is noted that for applications requiring distribution stability greater than one part in 10/sup 15/ at 1000 s averaging times, a stabilized fiber optic link is the only choice presently available. A stabilized fiber optic system that can improve distribution stability by more than 100 times is also described. It uses a cable delay compensator.<<ETX>>

High stability microwave fiber optic systems: demonstrations and applications

Measurements are presented for microwave fiber optic transmission systems that have much lower phase noise than high quality oscillator signals which have been multiplied to microwave frequencies. Progress in the development of wideband microwave fiber optic links for direct transmissions of the S- and X-band low-noise amplifier outputs in JPL/NASA deep space station antennas is discussed. A testbed microwave fiber optic system using a semiconductor-diode-laser pumped neodymium-yttrium-aluminum-garnet (Nd:YAG) laser and a lithium niobate electrooptic modulator is described. This system is used to demonstrate transmission of signals from 2.5 GHz to 12 GHz over 29 km between two deep space stations. Phase noise performance measured at X-band on this system is presented, and factors affecting phase noise performance are discussed.<<ETX>>

Status of frequency and timing reference signal transmission by fiber optics

The authors report recent progress in high-stability fiber-optic distribution of frequency and timing reference signals. They outline state-of-the-art performance at 100 MHz, 1 GHz, and 8.4 GHz for these systems. A lower cost, lower performance distribution system for the user who does not need full H-maser stability is described. Future fiber-optic system developments and their potential impact on systems which use high stability frequency reference distribution are discussed. System hardware and cost-performance tradeoffs are considered. A cost-performance tradeoff is presented, along with a cost savings suggestion to use a single fiber-optic transmitter to transmit a signal to several users simultaneously.<<ETX>>

Distribution of ultra-stable reference frequency signals over fiber optic cable (for radiotelescopes)

Radiotelescope systems, which operate primarily at microwave frequencies, are used for radio and radar astronomy, very large baseline interferometry (VLBI), geodynamic measurements, and spacecraft navigation. Experimenters have struggled for years to overcome the deficiencies of metallic coaxial cables and waveguides which have limited the stability and accuracy of measurements made with radiotelescope systems. Advances in fiber optic technology are on the verge of eliminating transmission lines as the major source of error in these systems. A description is given of high-stability fiber optic links which are used to distribute reference frequencies over distances as far as 29 km. Reference signals generated by hydrogen masers are distributed over these links and maintain a stability of 1 part in 10/sup 15/ for 1000-s averaging times.<<ETX>>

Ultrastable microwave and millimeter wave photonic oscillators

Novel photonic realizations of ultrastable microwave and millimeter-wave sources are discussed. The phase noise performance of an all-photonic microwave and millimeter-wave oscillator based on a mode-locked semiconductor laser stabilized by a fiber-optic delay-time is investigated. The phase noise performance is calculated using previously derived theory, and it is shown to compare favorably with the performance of state-of-the-art microwave oscillators.<<ETX>>

Impact of semiconductor laser frequency deviations on fiber optic frequency reference distribution systems

An analysis is presented of the effect of the linewidth of a single-longitudinal-mode semiconductor laser on the frequency stability of a frequency reference transmitted over single-mode optical fiber. The interaction of the random laser frequency deviations with the dispersion of the optical fiber is considered to determine theoretically the effect on the Allan deviation of the transmitted frequency reference. It is shown that the magnitude of this effect may determine the limit on the ultimate stability possible for frequency reference transmission on optical fiber, although it is not a serious limitation to present system performance.<<ETX>>

A new test of relativity using hydrogen maser standards

A novel test of relativity that was performed using advanced time and frequency technology of the Deep Space Network is discussed. The instrumentation, procedure. and data analyses are described. By directly measuring the propagation-delay variation between two masers, limits on a possible anisotropy in the one-way velocity of light have been obtained.<<ETX>>