Complete characterization of ultrashort pulse sources at 1550 nm

This paper reviews the use of frequency-resolved optical gating (FROG) to c haracterize mode-locked lasers producing ultrashort pulses suitable for hig h-capacity optical communications systems at wavelengths around 1550 nm, Se cond-harmonic generation (SHG) FROG is used to characterize pulses from a p assively mode-locked erbium-doped fiber laser, and both single-mode and dua l-mode gain-switched semiconductor lasers, The compression of gain-switched pulses in dispersion compensating fiber is also studied using SHG-FROG, al lowing optimal compression conditions to be determined without a priori ass umptions about pulse characteristics. We also describe a fiber-based FROG g eometry exploiting cross-phase modulation and show that it is ideally suite d to pulse characterization at optical communications wavelengths. This tec hnique has been used to characterize picosecond pulses with energy as low a s 24 pJ, giving results in excellent agreement with SHG-FROG characterizati on, and without any temporal ambiguity in the retrieved pulse.