Clock extraction using saturable absorption in a semiconductor nonlinear optical amplifier

A novel approach to clock extraction for non-return-to-zero (NRZ) formatted data is demonstrated using two contact semiconductor nonlinear optical amplifiers (NLOAs). The NLOA amplifies the transmitted data (fiber-fiber approximately 5 dB) and due to the absorptive nonlinearity, induced by bleaching a region of saturable absorption within the NLOA, an electrical clock component is generated at the absorber electrical contact. Narrow bandpass electrical filtering of the absorber contact electrical RF spectrum is all that is required in order to extract a stable clock signal. Bit-error-rate measurements at 155.6 Mb/s showed no receiver sensitivity penalty when using the NLOA extracted clock compared to the transmitter clock. Using quantum well material strong clock component generation has been achieved at modulation rates from < 100 Mb/s up to 5 Gb/s.<>