Martin Witte

Coarse WDM/CDM/TDM concept for optical packet transmission in metropolitan and access networks supporting 400 channels at 2.5 Gb/s peak rate

To improve the networking flexibility in the metropolitan and access area, the granularity in the optical domain has to be increased above that in the core network requiring more channels at lower bit rates. Pure dense wavelength division multiplexing (DWDM) as it is applied in the core does not seem to meet this requirement at affordable cost. We propose and analyze a network based on hybrid optical multiplexing techniques including wavelength, code, and time division multiplexing. Applied to optical packet transmission this approach enables several 100 all-optical channel between end users and headend with average bit rates up to 100 Mb/s per channel while keeping the installation and maintenance cost at a minimum.

Operational stability of a spectrally encoded optical CDMA system using inexpensive transmitters without spectral control

We show that an 8/spl times/155.52 Mb/s optical code-division multiple-access system applying periodic spectral encoding can be operated with poor quality optical filters and only loosely specified optical sources while still achieving bit-error rates (BER)=10/sup -10/ for each transmitter in asynchronous operation. It is experimentally found that BER<10/sup -9/ is maintained, if the optical receiver filter periodicity is changed by up to /spl plusmn/0.27%. From this finding we deduce that the optical transmitter filters do not need to be actively temperature controlled within the range -40/spl deg/C to +85/spl deg/C. This robustness is qualitatively understood from a simple crosstalk model depicted in the letter.

High-speed transmission of broad-band thermal light pulses over dispersive fibers

The maximum link length in high-speed transmission of thermal light pulses over fibers is mainly limited by chromatic dispersion. We have experimentally investigated the modulation transfer function (MTF) of standard single-mode fibers (SMF) for intensity modulated light-emitting-diode (LED) signals around 1550 nm. Using a fourth-order high-pass filter, we could fully open the closed eye pattern of 64-nm-wide LED pulses transmitted at 155.52 Mb/s over 9.4-km SMF and achieved BER<10/sup -9/ with a power penalty of 10.7 dB. We attribute the penalty to enhanced receiver noise and propose means to reduce it.

Adaptive PMD compensation for 170 Gbit/s RZ transmission systems with alternating polarisation

We report on adaptive PMD (polarisation mode dispersion) compensation in a 170 Gbit/s RZ transmission system with alternating polarisation. The PMD tolerance is significantly improved using an asymmetric rather than symmetric setup of the two-stage PMD compensator.

Optical CDMA transmission for robust realization of complex and flexible multiple access networks

We have implemented an optical 8/spl times/155.52 Mbit/s CDMA system with up to 40-km standard fiber, cascaded optical amplifiers, and optical dispersion compensation. The network performance is analyzed for different bit rates and the filter stability requirements are evaluated.

Bidirectional optical code division multiplexed field trial system for the metro and access area

A fully operational bidirectional optical code division multiplexed system has been successfully implemented within the KomNet field trial. 4/spl times/155.52 Mbit/s signals each in up- and downlink are transmitted over a 20 km two fibre feeder. Transmission of the signals over DWDM metro rings is discussed.

Field trials with channel bit rates of 160 Gbit/s

We present two 8/spl times/170 Gbit/s DWDM/OTDM (1.28 Tbit/s) field transmission experiment both over more than 400 km in commercially operated legacy networks of France Telecom (FT) and Deutsche Telekom (DT), respectively. Conventional EDFA based amplification schemes as well as distributed Raman amplified systems are tested. For different levels of polarization mode dispersion due to different quality of the installed fibre infrastructure adaptive PMD compensation and polarization de-multiplexing is tested.

PMD tolerance of 8/spl times/170 Gbit/s field transmission experiment over 430 km SSMF with and without PMDC

We report on the impact of PMD in a 8/spl times/170 Gbit/s DWDM transmission experiment over 430 km field installed SSMF with and without PMD compensation. Stable performance is only achieved when using PMDC.

An optical access system with 8 asynchronous transmitters and >1 Gbit/s network capacity

An experimental optical access network with 8 asynchronous transmitters and a total capacity of 1.244 Gbit/s is demonstrated the impact of the optical spectrum and of the network configuration on the maximum network capacity is evaluated.