In the case of a flexible network implemented with a cross-connect, a mesh with its multiple routes offers survivability options. In a bus structure, resilience is achieved by adding an extra link to the network to make a ring, offering simple alternative routes for the connections should they be needed. Another network element not yet mentioned is the regenerator. It does not add functionality in terms of traffic handling but is present for transmission purposes. With distance, pulses get smaller, as a result of attenuation.
Pulses also get fatter or more spread out, as a result of chromatic dispersion.
The game is to keep the pulses tall and thin so that the receiver at the end can recognize and separate them. Small and fat pulses would indeed blur together after some distance, making the receiver unable to recognize the original signal. Attenuation and Dispersion Pulses of light must go as far as possible along a fiber to minimize the cost of the link. Light can typically travel 40 or 80 km before it gets too attenuated or dispersed. The farther it can travel without needing a site with equipment to boost the signal, the cheaper the resulting network will be.