High Dispersion Tolerance Research Articles

Improvement of SPM tolerance for phase-modulated duobinary transmissions using phase modulator with postfiltering technique

We theoretically investigate self-phase modulation (SPM) tolerance of a new duobinary signals employed a phase modulator and optical filter, referred to as phase-modulated (PM) duobinary signals. For the conventional duobinary transmission (DBT) with electrical low-pass filters, fiber input power is strongly limited due to SPM. However, our results suggest that SPM tolerance can be improved while maintaining high dispersion tolerance using PM-DBT, since the signals with a constant power are transmitted over fibers. Adjusting the phase difference between mark and space levels of phase modulators, we can further improve SPM tolerance, compared with the conventional DBT.

Demonstration of optical duobinary transmission system using phase modulator and optical filter

We experimentally demonstrate an optical duobinary transmission system employing a phase modulator and a narrow-bandwidth optical filter. Compared to the conventional duobinary signal generated by using an electrical low-pass filter, the demonstrated duobinary signal 1) provides improved receiver sensitivity; 2) overcomes the problem associated with word lengths; and 3) substantially relaxes the performance sensitivity to the driver and modulator response, while maintaining narrow spectral bandwidth and high dispersion tolerance.

10-Gb/s transmission of 1.55-μm directly modulated signal over 100 km of negative dispersion fiber

In this letter, the largest transmission distance (100 km) ever reported for a commercially available 10-Gb/s 1.55-/spl mu/m directly modulated signal over a single fiber link without using any dispersion compensation is demonstrated. The achieved dispersion-length product for a Q-factor greater than 9.4 dB (bit-error rate less than 10/sup -15/) was about 750 ps/nm. The fiber that enabled such long transmission distance with high dispersion tolerance is a nonzero dispersion-shifted fiber that has negative dispersion in the entire usable bandwidth (1280-1620 nm) and is optimized for operation with directly modulated lasers. The excellent single-channel transmission performance that we achieved can be expected also from wavelength-division-multiplexed systems with channels across the erbium-doped fiber amplifier bands.

Receiver optimization for 40-Gb/s optical duobinary signal

The optimized optical receiver for a 40-Gb/s optical duobinary signal is investigated by simulation. It is found, that by optimizing the optical filter and the electrical filter in the receiver, the sensitivity of the optical duobinary can be improved greatly; meanwhile, the high dispersion tolerance nature of the optical duobinary signal will not be degraded.

160 Gbit/s WDM transmission experimentusing four 40 Gbit/s optical duobinary channels

Four-channel multiplexed 40 Gbit/s optical duobinary signals are successfully transmitted over a 100 km dispersion-shifted fibre for the first time. 40 Gbit/s based four-channel WDM transmission without individual channel dispersion compensation was achieved by virtue of the high dispersion tolerance of the optical duobinary signal.

Expansion of tolerable dispersion rangein a 40 Gbit/s optical transmission systemusing an optical duobinary signal

The authors demonstrate the high dispersion tolerance of a 40 Gbit/s optical duobinary signal. The tolerable dispersion range of the signal was 175 ps/nm. This dispersion range is more than twice that obtained using a binary non-return-to-zero intensity modulated signal.