Today, commercial fiber optical transmission systems are operated at a data rate of 10 or 40 Gbit/s per wavelength channel. The optical time division multiplexing (OTDM) technique allows for the investigation of the next generation TDM data rate of 160 Gbit/s while electrical signal processing at 160 Gbit/s is not yet available. In an OTDM transmission system, the key functions of the transmission system are realized using ultrafast all-optical or electro-optical network elements. In this paper, the recent progress in ultrafast technologies for 160 Gbit/s OTDM transmission systems is reviewed. The focus will be on techniques to realize optical pulse sources and ultrafast optical gates which operate on a time scale of a few picoseconds to a few hundred femtoseconds. They are the key elements of a 160 Gbit/s OTDM transmission system and are applied for various functions in the system. The paper focuses in particular on the application of ultrafast optical technologies for measurement purposes. In an optical communication system the quality of the data signal can be inferred from the optical eye diagram of the data signal. Presently, the measurement of optical eye diagrams at a data rate of 160 Gbit/s is inhibited by the limited bandwidth of photodetectors and electrical sampling oscilloscopes. By realizing an all-optical sampling system using the ultrafast technologies discussed before, the bandwidth of such an optical sampling system exceeds 400 GHz and allows for eye diagram measurements up to 320 Gbit/s.

The configuration and operation of an all-optical 3R-regenerator for high-speed data transmission are described. An all-optical 3R-regenerator using a fiber-based optical switch is proposed and successfully demonstrated in a 160Gbit/s 3R-regenerating transmission experiment.

Error-free all-optical demultiplexing is demonstrated with a monolithically integrated switch for 160 Gbit/s data stream. The switch comprises 'band gap shifted' semiconductor optical amplifiers, monolithically integrated within a symmetric Mach-Zehnder interferometer.

Single-polarisation 160 Gbit/s OTDM transmission over 3 x 80 km dispersion-managed SLA fibre using DPSK and OOK modulation is reported. The influence of the fibre input power is experimentally and theoretically investigated. A significant advantage for DPSK is revealed.

The design and fabrication of a monolithically integrated balanced photodetector module is reported and its application in a single polarisation 160 Gbit/s OTDM transmission experiment with RZ-DPSK modulation format. The 2.5 dB improvement in receiver sensitivity enabled transmission over a record fibre link of 410 km using exclusively EDFAs.

General guidelines for high-speed time-division multiplexing (TDM) data-rate transmission are essential for the increase of the overall transmission capacity. In this paper, general theoretical investigations concerning fiber chromatic dispersion in optical TDM systems are performed. Recent experiments that confirm the theoretical predictions are presented. Nonzero dispersion-shifted fiber and standard single-mode fiber are recommended for 40 and 160 Gb/s, respectively, independent of the chromatic dispersion compensation scheme.

A 160 Gbit/s all-optical wavelength converter with 3R-regenerating capability is demonstrated. The 3R-wavelength converter uses an optical decision gate based on ultrafast fibre nonlinearity to switch a 160 GHz pulse train by the incoming 160 Gbit/s data signal. A pulse shaper is implemented to reduce the detrimental effect of phase jitter in the decision gate and a fibre-based wavelength shifter for free allocation of the wavelength at the output.

We have investigated three interferometric all-opticaI switches based on cross-phase modulation (XPM) in semiconductor optical amplifiers (SOAs), the semiconductor laser amplifier in a loop mirror (SLALOM) switch, the Mach-Zehnder interferometer (MZI) switch, and the ultrafast nonlinear interferometer (UNI) switch. Switching windows with different widths are measured under similar conditions for all three switching configurations. We introduce the integrated contrast ratio (ICR) as a measure to evaluate the performance of a switch from switching windows. Using the ICR, the switches are compared and their application is discussed as demultiplexer in optical time division multiplexing (OTDM) systems for data rates of 40, 80, and 160 Gb/s.

Theoretical and experimental switching windows for all-optical demultiplexing from 160 to 10 Gb/s and 40 Gb/s, using a gain-transparent ultrafast nonlinear interferometer are presented. Based on these results we determined the maximum transmittance and the integrated contrast ratio, measures for switching losses and crosstalk from neighboring channels, respectively. Demultiplexing to 40 Gb/s (as compared to 10 Gb/s) leads to 6 dB lower maximum transmittance and 3 dB higher integrated contrast ratio (lower crosstalk).

Clock recovery from optical time division multiplexed data signals up to 160 Gbit/s is experimentally demonstrated using a phase-locked loop with a semiconductor optical amplifier in a loop mirror as a fast optical phase comparator. The timing jitter of the optical clock pulse extracted from a 160 Gbit/s data signal was < 0.3 ps.

The all-optical 80 and 160 to 10 Gbit/s demultiplexing performance of this new switching concept have been demonstrated. The key components of this interferometric switch are the band gap shifted semiconductor optical amplifiers monolithically integrated in a symmetric Mach-Zehnder interferometer.

We report on an all-optical demultiplexer based on gain-transparent operation of a semiconductor optical amplifier (SOA) in an ultrafast-nonlinear interferometer (GT-UNI). The GT-UNI comprises a robust fiber-chip setup in a folded geometry. For switching window widths of 5.2 ps and 6.0 ps, error-free demultiplexing of 160-10 Gb/s is demonstrated.

T. Systems Nova, Technologiezentrum, the first 160 Gbit/s RZ transmission experiment over field-installed standard fibre G.652 is reported. The transmitter rests upon the OTDM technique. At the receiver, a 160 Gbit/s to 40 Gbit/s OTDM demultiplexer followed by 40 Gbit/s electrical signal processing (ETDM) is used. The results are compared with 160 Gbit/s to 10 Gbit/s OTDM demultiplexing experiments. The OTDM demultiplexer is based on cross phase modulation in a semiconductor optical amplifier.

We report on all-optical demultiplexing performance of the packaged monolithically integrated 'band gap shifted' Mach-Zehnder interferometer for 80 Gbit/s and 160 Gbit/s data streams. Details on design and fabrication of multi- fiber modules for arrayed waveguide-fed InP PICs are provided.

We report on all-optical switches for high speed optical communication systems based on semiconductor optical amplifiers in an interferometric configuration, whereby the photon energy of the switched data signal is below the band gap energy.

The cascaded amplifier and saturable absorber is presented as a new all-optical switching scheme for optical signal processing applications. First demultiplexing experiments demonstrate the principle of operation of this scheme.

We report on 40 Gb/s RZ-transmission over the record length of 252 km standard single-mode fiber using distributed Raman amplification. Effects of pulse width and dispersion compensation were investigated both, theoretically and experimentally.