ABSTRACT
This chapter focuses on long-haul radio-over-fiber employing digital quadrature amplitude modulation on radio frequency (RF) subcarriers. It provides an overview of long-haul analog link design, as it can be applied to the RF subcarrier regardless of the modulation. The chapter discusses additional high-dynamic-range and low-noise-figure photonic links. External electro-optic modulation provides larger bandwidth than direct modulation of lasers. The most common wideband analog modulation format is intensity modulation with direct detection employing an external Mach–Zehnder modulator. The performance of a long-haul analog photonic link will typically improve with increased output optical power. A process that limits the power handling of an optical fiber, and hence the performance of a long-haul analog link, is stimulated Brillouin scattering. Double Rayleigh scattering is particularly important in long-haul analog links and delay lines operating at low electronic frequencies and/or employing broad-linewidth lasers. Double Rayleigh scattering can also be detrimental in optoelectronic oscillators with long cavities.
