Microwave photonics has advanced greatly as a result of breakthroughs on many fronts. Breakthroughs in fiber amplifiers, sources and receivers have all resulted in greatly increased system performance, and significant evolution of microwave photonic networks has occurred. The author discusses these elements in turn. There are many applications of microwave photonics, including fiber optic distribution of signals for cellular networks, phase array radars, and cable TV. Bandwidth requirements in these applications keep increasing, driving up the center frequency and increasing the need for microwave photonics to reduce the loss, dispersion, crosstalk and cost. This is also causing an evolution in these networks from smaller, lower frequency networks at 0.88 /spl mu/m to larger, higher frequency networks at 1.3 and 1.5 /spl mu/m.