Rocco Siano

All-Optical Wavelength Conversion of a 100-Gb/s Polarization-Multiplexed Signal

We present the results of an in-depth experimental investigation about all-optical wavelength conversion of a 100-Gb/s polarization-multiplexed (POLMUX) signal. Each polarization channel is modulated at 25 Gbaud by differential quadrature phase-shift keying (DQPSK). The conversion is realized exploiting the high nonlinear chi((2)) coefficient of a periodically poled lithium niobate waveguide, in a polarization-independent configuration. We find that slight non-idealities in the polarization independent setup of the wavelength converter can significantly impair the performance of POLMUX systems. We show that high-quality wavelength conversion can be nevertheless achieved for both the polarization channels, provided that an accurate optimization of the setup is performed. This is the first demonstration, to the best of our knowledge, of the possibility to obtain penalty-free all-optical wavelength conversion in a 100-Gb/s POLMUX transmission system using direct-detection.

Measurement of PMD tolerance in 40-Gb/s polarization-multiplexed RZ-DQPSK

We experimentally investigate the first-order polarization-mode dispersion (PMD) tolerance of two polarization-multiplexed (POLMUX) RZ-DQPSK signals at overall 40 Gb/s. The polarization demultiplexing is enabled by an automatic endless polarization stabilizer. Time-interleaving the two orthogonally polarized RZ-DQPSK signals minimizes the crosstalk due to the non-ideal polarization stabilization, while it represents the worstcase for the PMD-induced crosstalk. Bit-error rate measurements are performed both in back-to-back and after 25-km standard single-mode fiber. The PMD tolerance is evaluated as a function of the instantaneous differential group delay, introduced by a first-order PMD emulator. 40-Gb/s POLMUX RZ-DQPSK is more sensitive to PMD than single-polarization 20-Gb/s DQPSK, while it is more PMD-tolerant than 40-Gb/s NRZ-OOK. Besides, its chromatic dispersion robustness is similar to the single-polarization 20-Gb/s DQPSK. The combination of POLMUX and DQPSK is therefore very promising in view of transmission systems at high bit-rate.

Stable 100-Gb/s POLMUX-DQPSK Transmission With Automatic Polarization Stabilization

The reliability of 100-Gb/s polarization-multiplexed return-to-zero differential quadrature phase-shift keying transmission is demonstrated exploiting direct detection and automatic polarization stabilization. We experimentally verified a 2-dB chromatic dispersion tolerance of 100 ps/nm. Long-term stability has also been assessed by sampling the bit-error rate every 3 min over a continuous period of 8 h. Measurements are performed both in back-to-back and after 8.8 km uncompensated standard single-mode fiber, in the presence of a polarization scrambler.

Impact of time-interleaving on directly-detected 100-Gb/s POLMUX RZ-DQPSK robustness to PDL-induced crosstalk

The impact of PDL-induced crosstalk on 100-Gb/s POLMUX RZ-DQPSK performance is investigated both experimentally and through numerical simulations in direct detection systems. We found that RZ time-interleaving, contrary to what happens with PMD, features a strong robustness to PDL. The detrimental effect of optical narrow filtering on PDL-induced penalty is also analyzed; RZ time-interleaving still proves the best solution to deal with the PDL issue.

Real-time 100-Gb/s POLMUX RZ-DQPSK transmission over uncompensated 500 km of SSMF by optical phase conjugation

We present an effective solution for the upgrade of a highly dispersive link to POLMUX RZ-DQPSK 100-Gb/s transmission. Dispersion compensation is obtained by properly inserting a single polarization-insensitive phase-conjugation device along the link.

Endless Polarization Stabilizer for High Bit-rate Polarization-Division Multiplexed Optical Systems

An endless polarization stabilization method is applied to a 40-Gbit/s RZ-DQPSK polarization-division multiplexed optical system. The effectivness of the polarization stabilizer in allowing the polarization demultiplexing of the two orthogonally polarized channels is experimentally verified.

Microwave-Domain Analog Predistortion Based on Chirped Delay Lines for Dispersion Compensation of 10-Gb/s Optical Communication Signals

Optical chromatic dispersion compensation is achieved by analog predistortion of the signal in the microwave domain exploiting a chirped delay line at the transmitter. We designed a microwave device that guarantees high compactness of the solution and increased performance in terms of uncompensated propagation reach. Error-free, 10-Gb/s transmission over 225 km of uncompensated fiber is experimentally demonstrated without the use of coherent detection, digital equalizers, or optical dispersion compensators.

20-Gb/s PolDM Duobinary Transmission Over 350-km SSMF Supported by a Polarization Stabilizer and an Optical Dispersion Compensator

A 20-Gb/s transmission over 350-km standard single-mode fiber exploiting duobinary dispersion robustness and polarization-division multiplexing has been demonstrated. The system performance is evaluated employing an automatic endless polarization stabilizer and a suitably designed transmitter-side optical dispersion compensator.

Transmitter-Side Microwave Domain Dispersion Compensation Using Direct Detection for 10-Gb/s Signals

A simple chromatic-dispersion compensation scheme operating in the microwave domain at the transmitter is shown. The proposed scheme avoids coherent detection by making use of a dual nested Mach-Zehnder modulator. Simulated and experimental performance results on 10-Gb/s nonreturn-to-zero signals are described.

Uncompensated 20 Gb/s duobinary polarization division multiplexing transmission over 200 km

Transmission of 20 Gb/s optical signal over 200 km of uncompensated SMF fiber is achieved. The duobinary format dispersion robustness has been exploited together with polarization division multiplexing to significantly increase the maximum uncompensated reach.