P. Ebrahimi

Time and frequency domain characteristics of polarization-mode dispersion emulators

We investigate both experimentally and theoretically a new technique to realistically emulate polarization-mode dispersion (PMD). We propose and demonstrate a PMD emulator using rotatable connectors between sections of polarization-maintaining fibers that generates an ensemble of high PMD fiber realizations by randomly rotating the connectors. It is shown that: (1) the DGD of this emulator is Maxwellian-distributed over an ensemble of fiber realizations at any fixed optical frequency; and (2) the frequency autocorrelation function of the PMD emulator resembles that in a real fiber when averaged over an ensemble of fiber realizations. A realistic autocorrelation function is required for proper emulation of higher order PMD and indicates the feasibility of using this emulator for wavelength-division-multiplexing (WDM) systems.

Polarization mode dispersion emulator

We investigate a new technique to realistically emulate polarization mode dispersion. We demonstrate that 15 sections of polarization-maintaining fiber with randomly rotatable connections emulates an almost ideal Maxwellian differential group delay (DGD) distribution, whereas fixed connections is inadequate.

Polarization-mode dispersion compensation in WDM systems

We demonstrate, both experimentally and numerically, polarization-mode dispersion (PMD) compensation in wavelength-division-multiplexing (WDM) systems without wavelength demultiplexing. Our technique improves the overall system performance by reducing the fading probability for the worst-performing channel at any given time. The effectiveness of our approach is based on the fact that, for moderate PMD, the probability that all channels are severely degraded at the same time is extremely small. A single-section PMD compensator reduces the 2% worst-case power penalty for a four-channel 10-Gb/s WDM system with /spl sim/42 ps average differential group delay from 9.6 to 5.3 dB.

Polarization-mode-dispersion emulator using variable differential-Group-delay (DGD) elements and its use for experimental importance sampling

We demonstrate a practical polarization-mode-dispersion (PMD) emulator using programmable differential-group-delay (DGD) elements. The output PMD statistics of the emulator can be chosen by varying the average of the Maxwellian DGD distribution applied to each element. The emulator exhibits good stability and repeatability in a laboratory environment. In addition, we demonstrate how this emulator may be used to experimentally employ the powerful technique of importance sampling to quickly generate extremely low probability events. This technique is used to measure the Q-factor degradation due to both average and rare PMD values in a 10-Gb/s transmission system.

Statistics of polarization dependant gain in Raman fiber amplifiers due to PMD

Summary form only given. With the recent availability of high power pump lasers, Raman amplification has become feasible for commercial DWDM fiber-optic communication systems. Raman fiber amplifiers are highly attractive for their low equivalent noise figure and wideband gain. However, the Raman gain coefficient is polarization sensitive and can be up to 10 times higher when the signal and pump polarization states are parallel rather than perpendicular. Previous studies of this polarization dependent gain (PDG) investigate its relationship with the polarization mode dispersion (PMD) of the fiber, and the degree of the polarization (DOP) of the pump laser. These studies show that when the average PMD of the fiber becomes high enough, or if the pump DOP is very low, then the PDG becomes negligible. But these studies do not investigate the statistical behavior of the polarization dependant gain. There are two ways of characterizing polarization sensitivity in Raman amplifiers. One is to measure the PDG at a given point in time, which is determined by varying either the pump or signal polarization and recording the difference between the maximum and minimum gains. Alternatively, one can monitor how the instantaneous gain varies over time due to both PMD induced variations and changes to the signals input state of polarization (SOP). In the paper we investigate the statistical characteristics of both of these parameters theoretically and experimentally.