Technique for stabilizing the phase of the reference signals in analog fiber-optic links

Abstract

The effects of temperature and longitudinal stress on the phase delay of reference signals in a fiber-optic link are discussed. A feedback system that uses a fiber-optic phase modulator is used to compensate for the phase fluctuations of a reference signal in the link. The phase deviations of a 50-MHz reference frequency that are caused by temperature variations of the link is reduced by more than 95% on optimization of the correction system. The advantages of this technique are that the fiber-optic phase modulator has a greater stability compared with the electronic phase modulators, and signal conversions from electric to optic and optic to electric are avoided.

Performance of QAM fiber optic links under the influence of rf phase noise

“…(1), when the signal to noise ratio (y) is 0 and infinity have also been determined. They can be expressed as follows [5]: lim10 P(Eyi)=1-1 (6) 528/SPIE Vol. 3491 […”

“…However, external variable factors like temperature, longitudinal stress, fiber dispersion, laser bias level fluctuations, and receiver noise cause a variable phase delay of the microwave signals transmitted through the optical fibers [6]. Also, in a low signal to noise environment, (e. g. less than 20 dB for 64-QAM), in-phase and quadrature components of the additive noise affect the phase estimate of the carrier signal [7].…”

Effects of EDFA Gain on WDM Fiber Optic Standard Frequency Distribution Link

“…These systems typically employ fiber optic links to distribute precise reference signals from a standard frequency source to remote sights. There are several components, such as the laser source, photo-detector, and optical amplifier, which degrade the phase stability of the reference signals [1][2][3]. Shot noise and thermal noise are contributed to the link by the photo-detector.…”