Optical sampling of narrowband microwave signals using pulses generated by electroabsorption modulators

We demonstrate an optical system for sampling narrowband microwave signals with a very high carrier frequency, based on optical pulses generated by two electroabsorption modulators. A theoretical model, based on sampling theory, gives the necessary conditions to accurately reconstruct the sampled signal. The theory indicates that relatively long pulses can be used to sample narrowband electrical signals with a very high carrier frequency. Such pulses can be generated using an optical source based on electroabsorption modulators. The use of such a source instead of a fiber laser enables to reduce the size, the cost, and the power consumption of the optical sampler as well as to significantly improve its reliability. When the optical pulses and the carrier frequency of the sampled signal are synchronized, the sampling rate of the electronic analog to digital converter in the system can be reduced by a factor of two. Synchronous and asynchronous sampling of electrical signals with a carrier frequency of up to 20 GHz were demonstrated experimentally. The experimental results are compared to the results of the theoretical analysis.