Publisher Summary Polarization mode dispersion (PMD) is a linear effect that can be compensated in principle. In an ideal circularly symmetric fiber, the two orthogonally polarized modes have the same group delay. However, in reality, fibers exhibit a certain amount of birefringence because of imperfections in the manufacturing process or mechanical stress on the fiber after manufacture. It is noted that fluctuations in the polarization mode and fiber birefringence produced by the environment lead to dispersion that varies statistically with time and frequency. PMD causes different delays for different polarizations and when the difference in the delays approaches a significant fraction of the bit period, it leads to pulse distortion and system penalties. Environmental changes— including temperature and stress—cause the fiber PMD to vary stochastically in time. PMD, illustrating the basic concepts, the measurement techniques, the PMD measurement, the PMD statistics for first- and higher orders, the PMD simulation and emulation, the system impairments, and the mitigation methods has been summarized in the chapter. Both the optical and the electrical PMD compensations are considered.

Polarization-Mode Dispersion

PMD is an issue for transmission at 10 Gb/s in a certain percentage of installed fibers. At 40 Gb/s and beyond the number of useful uncompensated fibers is dramatically reduced. We review the present solutions for active and adaptive PMD compensation

https://ieeexplore.ieee.org/iel5/10668/33654/01601295.pdf

PMD Compensation

Publisher Summary Photonic networks are beginning to take on an important role as a global information infrastructure for supporting economic activities, education, and mutual understanding of people. An important issue regarding hierarchical hybrid optical time-division multiplexing (TDM)/wavelength-division multiplexing (WDM) network nodes is how to realize ultrafast photonic processing, aiming for efficient and economical node realization. Photonic processing using optical fiber nonlinearity can be categorized into three functions. One is optical multiplexing, which is used in optical switches, multiplexers, and demultiplexers. The second is wavelength conversion, which is used in a variety of WDM systems. The third is phase-conjugation generation, which is used in midway optical phase conjugation (OPC) systems. In hybrid hierarchical optical time-division multiplexing wavelength-division multiplexing (OTDMWDM) networks—after grouping WDM channels as wavelength-band—the high-level traffic should be converted to terabit/s OTDM, which is cut through the low-level nodes with a guarantee of error-free transmission using single optical-carrier signal monitoring. Moreover, for the ultrahigh-speed OTDM scheme, all-optical polarization mode-dispersion (PMD) monitoring is needed to control the programmable optical circuit for PMD equalization.

OTDM and WDM for Large-Scale Photonic Networks

This paper reviews the principle of optical polarisation mode dispersion (PMD) compensation (OPMDC) It lays the emphasis on the challenges that OPMDC faces in order to improve its implementation in a DWDM system

Challenges for optical PMD compensation

We demonstrate the combined effects of SPM, GVD, and PMD-induced eye-diagram penalties by means of numerical simulations for 40Gbit/s NRZ and RZ modulation formats. Considering all orders of PMD, we choose a fixed state of input polarization (SOIP) and do the simulation 1000 times for each input average power, and then get the Q-penalty of eye-diagram by exponential extrapolation method for cumulative probability 10-5. When input average power is less than 0dBm, SPM effect is very weak and GVD is compensated completely, only PMD takes effect in this power area. The Q-penalties are constants for NRZ and RZ with different PMD values. As input average power increasing, SPM takes effect gradually. First order PMID can suspend the SPM affection, and the higher PMD value, the more postponement is observed. The Q-penalty contributed by higher order PMID has close relation with spectrum width of signal. For NRZ signal with chirp=-0.7, the interactions between SPM and chirp can decrease spectrum width of signal; the Q-penalty contributed by higher order PMD will decrease correspondingly. For RZ with duty 0.3, the changing of the root mean square (RMS) spectrum width induced by the interactions of SPM and chirp is not obviously in this case, the Q-penalties of SPM+GVD+PMD increase consistently. When SPM effect is too strong (For example: for NRZ, average power larger than 10dBm; for RZ with duty 0.3, average power larger than 6dBm.), the interactions of SPM+GVD+PMD will cause the seriously degradation of system performance for any duty cycle and PMID value. Under our simulation conditions, the narrower pulse-width, the less Q-penalty until duty cycle decreases to 0. 1.

Combined effects of SPM, GVD, and PMD on 40-Gbit/s NRZ and RZ modulation formats

Summary form only given. We confirmed a simultaneous multi-channel PMD equalization scheme for WDM channels by simulation, which consists of a variable lattice optical circuit, WDM-DMUX, channel PMD monitors. The steepest-descent method shows successful multi-channel PMD equalization.

Simultaneous multi-channel PMD equalization for WDM systems

We have experimentally investigated the nonlinear evolution of the basic polarization parameters. The nonlinear suppression of PMD (polarization mode dispersion) induced pulse broadening by reducing the coupling of the polarization modes is experimentally demonstrated in 10 Gbit/s RZ signal transmission.

K.I. Yamada

Papers

Simultaneous multi-channel PMD equalization for WDM systems

Suppression of PMD induced pulse broadening by using nonlinear evolution of polarization mode-coupling