Jochen Leibrich

High spectral efficiency 1.6-b/s/Hz transmission (8 x 40 Gb/s with a 25-GHz grid) over 200-km SSMF using RZ-DQPSK and polarization multiplexing

With relatively simple standard transmission equipment, we achieved a wavelength-division-multiplexing transmission with a record-high spectral efficiency of 1.6 b/s/Hz using return-to-zero differential quadrature phase-shift keying and polarization multiplexing over 200-km standard single-mode fiber with a 40-Gb/s capacity per wavelength but 10-GSymbol/s rate.

CF-RZ-DPSK for suppression of XPM on dispersion-managed long-haul optical WDM transmission on standard single-mode fiber

We present a new optical modulation format chirp-free return-to-zero differential phase shift keying (CF-RZ-DPSK), which enables wavelength-division-multiplexing (WDM) transmission at 10 Gb/s/ch at a channel spacing of 100 GHz over 3000 km without significant impairments due to cross-phase modulation (XPM). A transmitter setup is presented, which allows a simple implementation of CF-RZ-DPSK with two Mach-Zehnder modulators in push-pull operation. The robustness toward XPM is shown theoretically with the help of a simple analytical model for the XPM-induced phase modulation. The superior performance of CF-RZ-DPSK over other modulation formats [RZ-ampfitude shift keying (ASK), nonreturn-to-zero (NRZ)-DPSK, and NRZ-ASK, respectively] is clarified. Finally, simulation results for CF-RZ-DPSK in comparison to RZ-ASK show the superior performance of the newly proposed modulation format in a dense WDM setup.

Efficient numerical simulation of multichannel WDM transmission systems limited by XPM

For numerical simulation of wavelength-division-multiplexed transmission lines including group-velocity dispersion, self-phase modulation, and cross-phase modulation, the computation time is reduced by almost one order of magnitude. This is done by taking into account the channel walkoff within one split step.

Spectral Efficiency and Receiver Sensitivity in Direct Detection Optical-OFDM

We show by analysis and simulation that by proper biasing of the optical modulator, the intermodulation distortion is minimized. Thus the spectral efficiency can be improved and receiver sensitivity can be exchanged against spectral width.

Impact of Modulator Bias on the OSNR Requirement of Direct-Detection Optical OFDM

In optical orthogonal frequency-division multiplexing (OFDM) with direct detection, modulator bias voltage has a significant impact on receiver sensitivity. It is a compromise between control of carrier power and nonlinear distortion of the OFDM signal. In this letter, sensitivity improvement due to reduction of carrier power is treated analytically. Its range of validity is examined by simulation. The impact of nonlinearity is identified as the difference in sensitivity between a linear and a nonlinear model.

Constant envelope optical OFDM for improved nonlinear and phase noise tolerance

We introduce a new concept of OFDM transmission with constant envelope and coherent detection to reduce the sensitivity of OFDM signals to nonlinear effects and phase noise.

Frequency domain equalization with minimum complexity in coherent optical transmission systems

For chip-design of a frequency-domain equalizer, a simple procedure to minimize the number of multiplications is shown. Considerations include recent improvements of FFT-algorithms.

Receiver Sensitivity of Advanced Modulation Formats for 40 Gb/s DWDM Transmission with and without FEC

Receiver sensitivity of a wide range of current modulation formats including multi-level formats and coherent detection is studied by extensive Monte-Carlo simulations and by experiment. Required OSNR for BER of 10-9 with and without FEC is determined.

OFDM transceiver design for optimizing sensitivity and long-haul performance

Design parameters for optical OFDM transceivers based on intensity modulation and direct detection are considered. Proper selection of modulator bias improves sensitivity by several dB. The length of the guard interval is adapted for uncompensated long-haul transmission.

Orthogonal Frequency Division Multiplexing (OFDM) and other Advanced Options to achieve 100Gb/s Ethernet Transmission

Based on the demand for transmission technologies offering high ratio of bits per symbol, two promising candidates to achieve a data rate of 100 Gb/s per optical carrier are discussed, namely optical orthogonal frequency division multiplexing and 16-ary multilevel modulation.