Systems design concepts for optical synchronization in accelerators

Development of accelerator-based light sources is expanding the size of femtosecond laser systems from tabletop devices up to kilometer-scale facilities. New optical techniques are needed to maintain temporal stability in these large systems. We present methods for distributing timing information over optical fiber using continuous optical waves, and how these can be employed in advanced accelerators requiring less than 100 fs timing stability. Different techniques combine to form a tool set that can provide for synchronization down to a few femtoseconds. Practical examples are given for timing systems applicable to FELs now under construction, with experimental results to show these systems can be built with required performance.