Abstract: Methods and apparatus, including computer program products, implementing and using techniques for controlling three or more nested modulators in an optical signal application. A single bias controller circuit is coupled to the respective DC biases for each of the nested modulators. The bias controller circuit sends a separate bias control signal to each of the nested modulators to set a working point for each of the nested modulators. An optical filter located at the output of the nested modulators in the path of a tapped signal and coupled to the bias controller circuit passes a carrier wavelength of the optical signal and blocks wavelengths other than the carrier wavelength. At least one photo detector is coupled to the bias controller circuit and senses an error signal associated with a pilot tone.

Abstract: Methods, apparatus, and systems, including computer program products, implementing and using techniques for measuring multi-channel single-shot transient signals. A signal acquisition unit receives one or more single-shot pulses from a multi-channel source. An optical-fiber recirculating loop reproduces the one or more received single-shot optical pulses to form a first multi-channel pulse train for circulation in the recirculating loop, and a second multi-channel pulse train for display on a display device. The optical-fiber recirculating loop also optically amplifies the first circulating pulse train to compensate for signal losses and performs optical multi-channel noise filtration.