E. Hilliger

Time-domain modeling of semiconductor optical amplifiers for OTDM applications

An advanced time-domain dynamical model for the investigation of semiconductor optical amplifiers (SOA) is presented. The model accounts for the ultrafast gain dynamics, the gain saturation and the gain spectral profile. It is also suitable for analyzing the amplifier in a system environment. As an example the model is used to investigate the gain dynamics of an SOA as well as the characteristics of an interferometer switch semiconductor laser amplifier in a loop mirror (SLALOM). Good agreement between modeling and experiment is shown. The model can be applied to the investigation of other optically time-division multiplexed (OTDM) applications, too.

160 Gbit/s clock recovery with electro-optical PLL using a bidirectionally operated electroabsorption modulator as phase comparator

A 40 GHz clock signal is recovered from a single-polarisation 320 Gbit/s data signal using a bidirectionally operated electroabsorption modulator (EAM) as phase comparator. The clock recovery was operated in a single-polarisation 320 Gbit/s, 160 km transmission experiment.

Enabling transmission at 160 Gbit/s

We discussed optical signal processing for the next generation time division multiplexed (TDM) bit rate of 160 Gbit/s. First field trials show that this technique has a promising potential for practical applications.

Analysis of switching windows in a gain-transparent-SLALOM configuration

Experimental and theoretical switching windows in an interferometric configuration with a gain-transparent semiconductor optical amplifier in a loop mirror (GT-SLALOM) are investigated. The amplifier gain and phase dynamics are analyzed in detail. For the gain dynamics, experimental and theoretical pump-probe results are presented. The phase dynamics is investigated theoretically. It is shown that the insertion of an optimized nonreciprocal phase shift in the GT-SLALOM configuration increases the contrast of the switching windows and, thus, improves the performance of the switch for demultiplexing applications. The influence of an asymmetric coupling ratio of the 3-dB input/output coupler on the switching contrast is also discussed.

All-optical demultiplexing and wavelength conversion in an electroabsorption modulator

Cross-absorption modulation in an all electroabsorption modulator is utilised to perform 80/10 Gb/s all-optical demultiplexing. An improvement in receiver sensitivity at 10 Gb/s is demonstrated when wavelength converting.

Sampling pulses with semiconductor optical amplifiers

We demonstrate three techniques to measure the instantaneous frequency and intensity of optical pulses using semiconductor optical amplifiers (SOAs). Four-wave mixing, gain-saturation, and interferometric switching through a nonlinear optical loop mirror are three mechanisms by which sampling is done. We have experimentally measured the intensity and chirp profiles of pulses with energies as low as 10 fJ. Since the nonlinearity in the SOA is relatively slow, these measurement techniques are most appropriate for picosecond pulses often found in telecommunication applications. The temporal resolution of these methods are limited by timing jitter, which was /spl ap/0.5 ps for the mode-locked laser diodes we used in our experiments, and by the width of the switching window.

EAM with improved switching performance by self cascading

The self cascading of an electroabsorption modulator (EAM) with commercially available components improves the switching performance of a single electroabsorption modulator. The improved performance is demonstrated in 160 to 40 Gbit/s demultiplexing experiments and 40 GHz pulse generation.

Evaluation of switching windows for fast optically-controlled SOA switches

We present a novel algorithm to evaluate the performance of optical demultiplexers from standard switching-window measurements. Investigations of a SLALOM/TOAD demultiplexer for 80 Gb/s and 160 Gb/s show that biasing one arm of the interferometer by a constant phase offset significantly improves its performance.

Optical clock recovery employing an optical PLL using cross-phase modulation in a Sagnac-interferometer

Summary form only given. Clock recovery (CR) is an essential part of any transmission system. In this paper, we propose a new type of optical clock recovery based on an optical PLL, where a SLALOM (Eiselt et al., 1995) acts as an ultrafast phase comparator. The scheme has been demonstrated successfully at bit rates up to 160 Gb/s.

Wavelength and intensity sampling of optical signals using semiconductor optical amplifiers

Summary form only given. All-optical sampling of pulses is important for characterizing high-speed TDM systems. Many all-optical sampling techniques have been developed, but often measure only the intensity profile and not the wavelength profile. We demonstrate and compare three measurement techniques using semiconductor optical amplifiers to directly obtain the intensity and wavelength profiles (chirp) of an unknown optical pulse with resolution of about 1 ps and without extensive computation. The presented techniques have in common that a synchronized short probe pulse is used to sample a broader signal pulse. The interaction between these pulses is, however, mediated through different mechanisms, namely four-wave-mixing, gain saturation, and interferometric switching.