More channels mean better lasers with higher power. The applications also have changed. Many CATV companies are entering in the competitive access arena. In short, fiber installations are larger and more complex, systems are faster and the requirements are more diverse. What is needed is flexibility and that is precisely what connectors do.
Back reflection affects the laser by enhancing power fluctuation, pulse distortion and phase noise.
Backreflection also affects the laser by a phenomenon called mode hopping. This causes the center wavelength to fluctuate. None of this is good. It is best seen as the slope of an OTDR trace. PC means physical or positive contact, where the fiber and faces of the two mating connectors actually touch.