What is the maximum RF frequency that can be transmitted over a standard single mode fiber link?

The maximum RF frequency that can be transmitted over a standard single-mode fiber (SMF-28) link is limited primarily by the modulation bandwidth of the electro-optic converter (laser or modulator) and the chromatic dispersion of the fiber, not by the fiber itself. The fiber's intrinsic bandwidth is enormous (theoretically hundreds of THz), but practical limits are: modulator bandwidth (a directly modulated DFB laser has a modulation bandwidth of 10-25 GHz, limited by the laser's relaxation oscillation frequency; a Mach-Zehnder modulator (MZM) has a bandwidth of 20-40 GHz (standard) or up to 100+ GHz (specialized mm-wave modulators); a traveling-wave MZM can achieve 3-dB bandwidth of 40-70 GHz at 1550 nm; for frequencies above 100 GHz: use optical heterodyne techniques (mixing two laser signals separated by the desired RF frequency) to generate the RF signal at the photodetector), photodetector bandwidth (a standard InGaAs PIN photodetector has a bandwidth of 10-40 GHz; a high-speed photodetector (uni-traveling carrier, UTC) achieves 100+ GHz bandwidth; the photodetector is matched to the modulator bandwidth), and chromatic dispersion (the RF signal is carried as an amplitude modulation on the optical carrier; chromatic dispersion causes the upper and lower optical sidebands to propagate at different velocities through the fiber; when they arrive at the photodetector with a specific phase shift, the RF power is reduced (dispersion-induced power fading); the first null occurs at: f_null = 1 / (2 x D x lambda^2 x L), where D is the fiber's chromatic dispersion parameter, lambda is the wavelength, and L is the fiber length; at 1550 nm (D = 17 ps/nm-km) over 10 km: f_null approximately 35 GHz; at 1310 nm (D approximately 0): f_null is effectively infinite (no dispersion fading)).