Active Delay Stabilization of a 440-km Fiber Link in a Wideband Microwave Delay System

In this paper, a wideband microwave delay system with an equivalent 440-km fiber link is presented. The fiber link propagation delay fluctuation, suffering from temperature variation, is detected incorporating with a reference RF signal. With the help of a variable optical delay line, the wideband microwave frequency output is phase-stabilized. A system figure of merit is investigated in detail. The results show that, with dispersion compensation, the fiber-optic delay system can operate for the frequencies up to 38 GHz. Moreover, the fiber-optic system can provide a noise figure of below 40 dB, a signal-to-noise ratio of above 51 dB and a spur level of less than -56 dB for the delayed wideband microwave frequency signal. An additive phase noise of -116 dBc/Hz at the 10 kHz offset frequency can be guaranteed for a 1 GHz frequency. With active delay stabilization, the 38 GHz frequency delayed achieves an Allan deviation of 5.8 × 10
^-13
/s and 5.4 × 10
^-16
/10
³
s, respectively.