The realization of an integrated delay line using tapered Bragg gratings in a drop-filter configuration is presented. The device is fabricated on silicon-on-insulator (SOI) rib waveguides using a Deep-UV 248 nm lithography. The continuous delay tunability is achieved using the thermo-optical effect, showing experimentally that a tuning range of 450 ps can be obtained with a tuning coefficient of -51 ps/°C. Furthermore the system performance is considered, showing that an operation at a bit rate of 25 Gbit/s can be achieved, and could be extended to 80 Gbit/s with the addition of a proper dispersion compensation.

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We show that Kerr nonlinearity induced intermodal power transfer in a particular mode group of a multimode fiber can be formulated by the same type of equation used to describe the effect of cross polarization modulation in single-mode fibers.

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We show how cross-polarization modulation and its associated signal depolarization can cause significant penalties in polarization-division multiplexed systems. We then explore the concept of degrees of freedom of a system to analyze the statistics of this impairment. IntroductionAs polarization-division multiplexing (PolDM) is becoming more and more common in long-haul transmission systems in order to achieve higher data rates, a nonlinear effect becomes significant that has long been ignored: cross-polarization modulation (XPolM) is closely related to cross-phase modulation, except that it randomly and adversely affects the polarization state of a transmitted signal instead of its phase. As we will show, this causes additional penalties during demultiplexing in PolDM systems. Since the penalty experienced by a particular system depends on the relative polarization states of all WDM channels and their evolution throughout the fiber, it will fluctuate with changes of these polarization states which are mainly caused by PMD. Thus the concept of outages can be borrowed from PMD theory and applied to XPolM also. We will present important steps on the way to define and determine such outages and their probabilities, starting with a brief review of XPolM and how it affects PolDM systems and subsequently introducing the concept of nonlinear degrees of freedom of a system to characterize its statistical properties.