Complete characterization of ultrashort pulse sources at 1550 nm

Abstract

Abstract-This paper reviews the use of frequency-resolved optical gating (FROG) to characterize mode-locked lasers producing ultrashort pulses suitable for high-capacity optical communications systems at wavelengths around 1550 nm. Secondharmonic generation (SHG) FROG is used to characterize pulses from a passively mode-locked erbium-doped fiber laser, and both single-mode and dual-mode gain-switched semiconductor lasers. The compression of gain-switched pulses in dispersion compensating fiber is also studied using SHG-FROG, allowing optimal compression conditions to be determined without a priori assumptions about pulse characteristics. We also describe a fiberbased FROG geometry exploiting cross-phase modulation and show that it is ideally suited to pulse characterization at optical communications wavelengths. This technique has been used to characterize picosecond pulses with energy as low as 24 pJ, giving results in excellent agreement with SHG-FROG characterization, and without any temporal ambiguity in the retrieved pulse.

Universality of the Peregrine Soliton in the Focusing Dynamics of the Cubic Nonlinear Schrödinger Equation

“…4 where we show the input pulse (green sampled points), the compressed pulse at These experiments provide clear confirmation that nonlinear pulse compression in optical fiber yields intensity characteristics in good agreement with the Peregrine soliton. To examine the pulse properties in more detail, however, requires complete characterisation of the compressed pulse in both amplitude and phase, and to this end we developed a second experimental setup using second harmonic generation FROG to characterise the nonlinear pulse evolution [27,28].…”

Optimization of optical data transmitters for 40-Gb/s lightwave systems using frequency resolved optical gating

“…For all the experimental results reported below, the standard checks on the quality of the data were made, including inspection of the FROG frequency and delay marginals and comparing the spectrum and autocorrelation derived from the retrieved field with those directly measured. Pulse retrieval for the characterization carried out in this work, routinely gave low retrieval errors of [7] with a 64 64 grid (i.e., 64 spectral and temporal points). In addition, the minimum average power for Fig.…”

“…The SHG signal was spectrally resolved using a spectrometer with a CCD array mounted on the output. The resulting spectrogram, which is obtained from the experimental FROG setup, can then be used to retrieve the pulse intensity and phase using the FROG phase retrieval algorithm of generalized projections (GP) [7]. For all the experimental results reported below, the standard checks on the quality of the data were made, including inspection of the FROG frequency and delay marginals and comparing the spectrum and autocorrelation derived from the retrieved field with those directly measured.…”

“…The optical pulses were then optically amplified to an average power of 10 mW (typical input power required for an optical communication system). The resulting pulses were characterized using the standard second harmonic generation (SHG) FROG technique as fully explained in [7], based on the spectral resolution of the output from a noncollinear autocorrelator. In addition, the generated pulses were measured using an optical spectrum analyzer and a 50-GHz oscilloscope in conjunction with a 50-GHz detector.…”

“…The usefulness of these pulses in high-speed systems is highly dependent on the frequency chirp acquired in the modulator, and it is thus vital to accurately characterize this chirp. In this letter, we demonstrate the characterization and optimization of optical pulses (suitable for use in 40-Gb/s systems) generated using a CW laser followed by a sinusoidally driven external modulator, using the technique of frequency resolved optical gating (FROG) [6], [7].…”