Poh-Boon Phua

All-frequency PMD compensator in feedforward scheme

We present the architecture of a broad-band polarization mode dispersion (PMD) compensator in a feedforward PMD compensation scheme. It is comprised of four stages. The net effect of the first two stages is equivalent to a frequency dependent polarization rotation that aligns all PMD vectors into a common direction. The third stage compensates the frequency dependent variable differential group delay (DGD) and the last stage compensates for the isotropic dispersion created by the first three stages. In Stokes space formulation, we describe the algorithm to find the required rotation angles of each stage using the PMD concatenation rule, and show that these rotation angles can be synthesized using all-pass filters (APF) in a compact integrated optics circuit. Through numerical simulations, we show significant improvement of the signal quality as a result of the compensation.

Real-time first- and second-order PMD characterization using averaged state-of-polarization of filtered signal and polarization scrambling

A real-time estimation technique for first- and second-order polarization-mode dispersion (PMD) is presented. It makes use of the spectrum of telecommunication signals. At the output of the transmission fiber, the signal is tapped and filtered. Three filters are used: a high-pass filter, a low-pass filter, and a narrow-band filter. The averaged states of polarization (SOPs) of the filtered signals are then measured using a polarimeter. We repeat the measurement for several different input SOPs using a polarization scrambler at the input of the fiber. From these measurements, we deduce the first-order PMD and, subsequently, the second-order PMD.

Deterministic approach to first- and second-order PMD compensation

The authors show that three concatenated first-order polarization mode dispersion (PMD) segments are sufficient to compensate any first- and second-order PMD present in a transmission fiber. They determine analytically the required individual rotation matrix of the polarization rotators and the required differential group delay for the variable delay line in the compensator.

Variable differential-group-delay module without second-order PMD

We propose a design for a variable differential-group-delay (DGD), formed by concatenation of four identical fixed DGD segments. Due to the symmetry involved, it produces zero second-order polarization mode dispersion (PMD). The generated third-order PMD is half the value of the conventional two-segment concatenation for variable DGD.

A deterministically controlled four-segment polarization-mode dispersion emulator

In this paper, we propose a novel design of a first- and second-order polarization-mode dispersion (PMD) emulator based on four concatenated first-order PMD segments. Instead of polarization scrambling at each junction, we set these polarization rotators according to a statistical schedule, so as to produce a realistic probability density function of the first- and second-order PMD presented in long-haul transmission fiber.

A deterministic broad-band polarization-dependent loss compensator

Polar decomposition of the transmission matrix allows lumped polarization-dependent loss (PDL) followed by lumped polarization mode dispersion (PMD) compensation at the receivers end. Thus, we propose in this paper, the architecture of a broad-band PDL compensator in a feed-forward compensation scheme. This module consists of three stages. Stage 1 and 2 are the frequency-dependent polarization rotators that align all the different PDL vectors into the {1,0,0} direction in Stokes space. Stage 3 eliminates both the PDL magnitude and the frequency dependence in the isotropic attenuation by introducing different frequency-dependent variable attenuation to the linear horizontal and vertical polarizations. By applying the known Mueller transformations of the PDL compensator to the monitored polarimetric data, we show that the composite PMD spectrum can be deduced for subsequent broad-band PMD compensation.

Combinatorial polarization scramblers for many-segment PMD emulator

In this letter, we present a combinatorial approach to build polarization scramblers in a many-segment polarization-mode dispersion (PMD) emulator. This approach significantly reduces the required number of phase plates and their corresponding controls. It exploits the fact that rotation matrices are noncommutative which gives many different ways of building polarization scramblers out of just a few phase plates. Although these polarization scramblers are correlated, we show, numerically and experimentally, that there is sufficient polarization scrambling between segments to achieve the important key properties of a PMD emulator.

Variable second-order PMD module without first-order PMD

We propose a module that generates variable second-order polarization mode dispersion (PMD) without producing any first-order PMD. It is based on four identical fixed differential group delay segments arranged in a symmetrical manner. Only one control parameter varies the magnitude of second-order PMD.

Deterministic broad-band PMD emulator

We present the architecture for a deterministic broad-band polarization-mode dispersion (DBPMD) emulator based on four stages. The first three stages of flexible frequency-dependent rotation provide the three degrees of freedom for emulating PMD at each frequency, while the fourth stage compensates for the isotropic dispersion created by the first three stages. We describe the algorithm to synthesize the required rotation angle of each stage using the PMD concatenation rules. Using numerical simulations, we demonstrate good fidelity of the DBPMD emulator in approximating randomly selected spectra of PMD vectors.