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

We show, using simulations, that a combination of orthogonal frequency division multiplexing (OFDM) and optical single sideband modulation can be used to compensate for chromatic dispersion in ultralong-haul wavelength-division multiplexed (WDM) systems. OFDM provides a high spectral efficiency, does not require a reverse feedback path for compensation, and has a better sensitivity than nonreturn to zero. This paper provides design rules for 800-4000-km optical-OFDM systems. The effects of WDM channel number and spacing, fiber dispersion, and input power per channel on the received Q are studied using extensive numerical simulations. These effects are summarized as a set of design rules

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Performance of Optical OFDM in Ultralong-Haul WDM Lightwave Systems

This paper presents a new method for the measurement of distributed polarization mode dispersion (PMD) in optical fibers. This method uses a polarization optical time-domain reflectometer (P-OTDR), and is based on a measurement of the degree of polarization of the backscattered light as a function of distance in the fiber. Both the average and the statistics of the degree of polarization are used to estimate the two relevant parameters for measuring PMD, namely, the beat length and the coupling length. At present, our P-OTDR gives qualitative results only. However, it enables to distinguish between high and low PMD sections in a long fiber link. This should already have practical applications, in particular for the characterization of installed fibers.

Distributed PMD measurement with a polarization-OTDR in optical fibers

We introduce digital precompensation for optical nonlinearities. A 10-Gb/s transmitter subsystem is described. Experimental results, across 320 and 1280 km of standard single-mode fiber (G.652) without any optical compensators, show substantial elimination of self-phase modulation. Some of the limits of this method are explored.

Electronic precompensation of optical nonlinearity

We present a simple, silica waveguide optical equalizer that significantly mitigates intersymbol interference (ISI) impairments for many wavelength-division multiplexed (WDM) channels simultaneously. We study the mitigation of ISI arising from band-limited transmitters, narrow-band optical filtering, chromatic dispersion, and polarization-mode dispersion (PMD). We demonstrate significant improvements, both single- and multichannel, at 40 Gb/s with a single, potentially set-and-forget device.

Simple multichannel optical equalizer mitigating intersymbol interference for 40-Gb/s nonreturn-to-zero signals

A reduced model to describe self-phase modulation (SPM)-limited fiber transmission in dispersion-managed lightwave systems is presented. By introducing a new figure of merit, the maximum transmission distance versus optical power can be determined without any numerical simulation. Together with simplified models for other nonlinear fiber effects, a useful set of design rules for a first-order performance estimation of wavelength-division multiplexed (WDM) systems is established.

Reduced model to describe SPM-limited fiber transmission in dispersion-managed lightwave systems

We experimentally demonstrate a significant improvement in the dispersion tolerance of optical duobinary modulation when employing an MLSE instead of a standard receiver. We show that the improvement critically depends on the MLSE design.

Measurement of the dispersion tolerance of optical duobinary with an MLSE-receiver at 10.7 Gb/s

We present a new adaptive optical equalizer concept for single-channel distortion compensation and analyze the performance of an adaptive optical FIR-filter in lattice structure (cascaded MZI) with respect to equalization of residual dispersion, self-phase modulation and polarization-mode dispersion.

http://ieeexplore.ieee.org/iel5/7749/21311/00989405.pdf

An adaptive optical equalizer concept for single channel distortion compensation

Using the distributed under-compensation scheme (DUCS) in every fibre span, the overall transmission distance of 10 Gbit/s NRZ and RZ multiple span systems is doubled The benefits of such a dispersion management scheme are clarified by defining a new figure of merit

http://ieeexplore.ieee.org/iel5/2220/17582/00810028.pdf

Optimised dispersion management scheme for long-haul optical communication systems

We determine system limitations due to cross-phase modulation (XPM) for non-zero dispersion shifted fiber by experiments and simulations. For the worst case of full dispersion compensation in each span we find a maximum power law whereas for appropriate undercompensation XPM can be efficiently suppressed.

C. Glingener

Papers

Reduced model to describe SPM-limited fiber transmission in dispersion-managed lightwave systems

Measurement of the dispersion tolerance of optical duobinary with an MLSE-receiver at 10.7 Gb/s

An adaptive optical equalizer concept for single channel distortion compensation

Optimised dispersion management scheme for long-haul optical communication systems

Influence of the dispersion map on limitations due to cross-phase modulation in WDM multispan transmission systems