Abstract: An optical fiber ring network carries data in frames of bit intervals that define a number of independent communication bands each represented by a series of spaced apart bit intervals no more than one of which falls within any given frame. The network serves a collision detection protocol by nodes that communicate with the user devices in accordance with the collision detection protocol but communicates with the ring in accordance with a non-collision type protocol. The network uses light that is amplitude modulated at more than two levels. The data frame boundaries are defined by violations of an alternate mark inversion data encoding technique. Phase synchronization of two streams of frames is accomplished by sampling frames at times governed by a selected one of two frame boundary clocks derived respectively from the two frames.