Bi-directional coupling in nonlinear waveguides for absolute timing determination

Summary form only given. Future broadband optical networks will work at bit rates exceeding 100 GHz through time-division multiplexing and wavelength-division multiplexing. For signal recovery a high-speed clock recovery or, sub-clock recovery scheme is required. For 3R signal regeneration the recovered clock is needed for retiming of the optical signal. It is conventional to use a nonlinearity with a fast recovery time to determine temporal coincidence such as four wave mixing in a semiconductor optical, amplifier, or saturable absorption in an injection locked laser. Schemes based on devices with slow nonlinear recovery times, such as an electroabsorption modulator, have been realized by applying an external electrical modulation. The optical arrangement presented monitors the difference between the nonlinear transmission of two pulses counter-propagating through a slow nonlinear medium, thus rapidly providing sufficient information to immediately determine the absolute timing error.