BOC is used for sub-femtosecond fiber link stabilization over kilometer distances. Due to a balanced optical detection scheme, the BOC provides exceptionally high timing sensitivity, attosecond timing resolution, amplitude invariance and robustness against environmental fluctuations. The output of the BOC is a baseband voltage signal that is proportional to the relative time delay between the two sources. This output can in turn be used in a phase-locked loop to synchronize the two optical sources. Standard wavelengths are 800 nm, 1030 nm and/or 1550 nm.
