Lothar Möller

Comparison of system tolerance to polarization-mode dispersion between different modulation formats

The polarization-mode dispersion (PMD) tolerance of different modulation formats is studied, including ON-OFF keyed (OOK), differential phase-shift keyed (DPSK), and carrier-suppressed return-to-zero (CSRZ) formats. It is shown that, generally, for PMD uncompensated systems, the modulation formats with larger pulsewidth have larger penalty, while the modulation formats with smaller bandwidth perform better in PMD compensated systems. It is also shown that DPSK can tolerate more PMD than OOK for both PMD uncompensated and compensated systems, and that CSRZ, because of its specific spectrum characteristics, has a different feature from return-to-zero formats.

Wavelength blocking filter with flexible data rates and channel spacing

This work presents a high-resolution (13.2 GHz) channel-blocking optical filter, suitable for use as a reconfigurable optical add/drop multiplexer (ROADM), which seamlessly supports data rates from 2.5 to 160 Gb/s. The filter consists of a linear array of 64 MEMS micromirrors and a high-dispersion echelle grating. The demonstrated device had an insertion loss of 9 dB, a loss ripple of 1.2 dB, and a group delay ripple of 15 ps. Data transmission through the device with various mixed data rate scenarios ranging from 2.5 to 160 Gb/s showed negligible penalty, except at 40 Gb/s where a maximum penalty of 1.5 dB was observed due to a phase coherence with the blocker filter ripple.

Suppression of intrachannel nonlinear effects with alternate-polarization formats

We investigate using alternate-polarization (APol) on-off keying formats, in which adjacent bits have orthogonal states of polarization, to suppress intrachannel nonlinear impairments in dispersion-managed (DM) optical fiber transmission systems. Simple methods to generate the APol formats are discussed, and the transmission performance of the APol formats for both 40-Gb/s DM systems and 10-Gb/s DM-soliton systems is experimentally studied. We show that the APol formats can significantly improve the performance of 40-Gb/s DM transmission systems, while the improvement of 10-Gb/s systems is smaller.

Data encoding on terahertz signals for communication and sensing.

We demonstrate and analyze data modulation of terahertz (THz) signals in the 1 Mbit/s range. THz pulse trains are phase and amplitude encoded with pseudorandom binary data, transmitted over a short distance, and detected. Different modulation formats are generated. Bit error measurements characterize the communication channel. We estimate from experimental results the maximum data rates for an optimized system.

Method for PMD vector monitoring in picosecond pulse transmission systems

A method and a device are proposed that allow measurement of the polarization mode dispersion (PMD) in a transmission line without data traffic interruption. The PMD vector information is extracted from the optical data signal spectrum. The method is experimentally verified by measuring of first-order PMD.

Mode stabilization technique for the multifrequency laser

A mode stabilization technique for waveguide grating router lasers which allows suppression of multi-longitudinal mode operation while simultaneously decreasing the laser chip size and increasing the maximum modulation speed is described.

Improvement of optical NRZ- and RZ-duobinary transmission systems with narrow bandwidth optical filters

We show that a narrow bandwidth optical filter at the receiver side can greatly improve the receiver sensitivity of a nonreturn-to-zero (NRZ)-duobinary system. We propose to use the narrow bandwidth filtering at the receiver side of a return-to-zero (RZ)-duobinary system to convert RZ-duobinary to NRZ-duobinary, so that the system tolerance to residual chromatic dispersion can be increased while its resistance to nonlinearity in transmission is still maintained. The idea is demonstrated with experiments.

Orthogonal-Polarization Heterodyne OSNR Monitoring Insensitive to Polarization-Mode Dispersion and Nonlinear Polarization Scattering

An in-band optical signal-to-noise-ratio (OSNR) monitoring technique that utilizes the polarization orthogonality and heterodyne mixing is proposed. The technique is not only insensitive to polarization-mode dispersion but also robust to nonlinear polarization scattering induced by interchannel cross-phase modulation. Moreover, the technique places no special requirements on the signal properties, such as modulation format and bit rate. The monitoring technique is demonstrated experimentally in both linear and nonlinear systems

Effect of cross-phase-modulation-induced polarization scattering on optical polarization mode dispersion compensation in wavelength-division-multiplexed systems

Interchannel cross-phase-modulation-induced polarization scattering (XPMIPS) and its effect on the performance of optical polarization mode dispersion (PMD) compensation in wavelength-division-multiplexed (WDM) systems are studied. The level of XPMIPS in long-haul WDM transmission systems is theoretically quantified, and its effect on optical PMD compensation is evaluated with numerical simulations. We show that in 10-Gbit/s ultra-long-haul dense WDM systems XPMIPS could reduce the PMD compensation efficiency by 50%, whereas for 40-Gbit/s systems the effect of XPMIPS is smaller.

Filter synthesis for broad-band PMD compensation in WDM systems

We present a means of synthesizing an arbitrary 2/spl times/2 Jones matrix filter, e.g., the inverse of a PMD fiber characteristic. The described algorithm allows arbitrarily accurate reduction of PMD in a frequency band. A PMD equalization technique for WDM systems is proposed.