S. Lanne

Fast eye monitor for 10 Gbit/s and its application for optical PMD compensation

The excellent correlation between high speed eye monitor signal and BER shows the potential for fast tracking of eye fluctuations and performance monitoring. PMD compensation experiments at 10 Gbit/s demonstrate the performance of a fast eye monitor used as feedback signal.

Transmission of 256 wavelength-division and polarization-division-multiplexed channels at 42.7Gb/s (10.2Tb/s capacity) over 3/spl times/100km of TeraLight/spl trade/ fiber

10.2Tb/s capacity is demonstrated over 3/spl times/100km in C and L bands, using 42.7Gb/s channels. The wavelength allocation was chosen while taking into account narrow optical filtering at the transmitter and receiver ends and second-order Raman pumping is used to improve the signal-to-noise ratio.

Cost-optimized 6.3 Tbit/s-capacity terrestrial link over 17 /spl times/ 100 km using phase-shaped binary transmission in a conventional all-EDFA SMF-based system

We demonstrate the feasibility of 6.3 Tbit/s capacity over 17 /spl times/ 100 km using well-proven all-erbium-doped fiber amplifier technology over a typical ultra-long haul link based on standard fiber. This experiment emphasizes the advantages of our modulation format, namely phase-shaped binary transmission.

Practical considerations for optical polarization-mode dispersion compensators

For transmission systems at 10 Gb/s and beyond, polarization-mode dispersion (PMD) is one of the limiting factors. Optical PMD compensators aim at increasing the PMD value tolerated by the system; however, they do not cancel out its effects. Therefore, the performance of a PMD compensator is assessed statistically. Requirements for optical PMD compensators include a response time in the range of 1 ms in order to follow polarization fluctuations over the line. The system design should account for the interaction of other transmission impairments with the PMD compensator operation. For instance, transmitter chirp and residual chromatic dispersion have a deleterious impact on the compensator performance. While self-phase modulation is harmless, cross-phase modulation greatly reduces the compensator efficiency. System design rules have been applied to a one-year field trial, showing the compensators efficiency and reliability. However, reducing their cost is the next challenge that will bring optical PMD compensators to be used in installed systems.

Demonstration of adaptive PMD compensation at 40 Gb/s

We report for the first time the full experimental assessment of an adaptive PMD compensator at 40 Gb/s over realistic PMD statistics. Results, consolidated by numerical simulations, show that the PMD limit is raised from 4 to 8 ps with the compensator.

From 2,100 km to 2,700 km distance using phase-shaped binary transmission at 6.3 Tbit/s capacity

The distance of our recent 6 Tb/s transmission experiment was increased by fine adjustment of dispersion management and by decreasing the signal power by 1 dB, yielding a record 17 Pbit/s.km capacity/spl times/distance product for terrestrial systems.

Extension of polarization-mode dispersion limit using optical mitigation and phase-shaped binary transmission

The admitted polarization-mode dispersion (PMD) limit is around 15% of the bit-time. With our first-order PMD mitigator, this limit is multiplied by 2 for a non-return to zero signal, and by 3 for a phase-shaped binary transmission signal.

Experimental statistical assessment of XPM impact on optical PMD compensator efficiency

In this paper, we report experiments on the statistical assessment of the reduction of PMD mitigator efficiency in presence of XPM effects. The XPM-induced depolarization limits compensation in polarization dispersive ultra-long haul system at 10 Gb/s.

Higher order PMD canceller

We studied a higher order PMD mitigation scheme, aiming at suppressing depolarized components of a compensated signal, the higher order canceller. It is composed of a simple compensator followed by a polarization controller and a polarizer. We experimentally verified that it performs better than its first stage alone. Using simulation, we addressed its impact on system to more relevant outage probability and better feedback signals. We prove, that, for a cumulative probability of CP=10/sup -5/ at (PMD)=30 ps, it can reduce by nearly 1 dB the power penalty of a simple compensator, reaching then the 2 dB outage margin. Finally, it should be emphasized that this mitigation technique is already implemented in polarization dependent receiver and has been so far overseen as an advantage of such a structure.

PMD compensation techniques

Mitigating PMD is still a challenge in today’s optical communications. After giving the key performance indicators dictated by the statistical nature of PMD, we introduce the classification of PMD compensation schemes into 2 categories: optical and electrical PMD compensators. In a first part, we explain the operation principle of a PMD compensator by taking a detailed look at the basic optical PMD compensator and appropriate feedback signals. More complex multistage structures and a feed-forward adaptation approach are also discussed. This first part is closed by results from a one-year field trial confirming the behavior and performance of a prototype compensator. In the second part of this article, electronic equalization for PMD mitigation is explained. Starting with a discussion on performance and adaptation of linear equalizers suitable for analog electronic signal processing, finally also the Viterbi equalizer basing on digital signal processing is analyzed. A comparative review of mitigation by optical or electronic means concludes the discussion.