High-Nonlinearity in Glass Fibers and Cross-Phase Modulation

Abstract

In this chapter, the effects of nonlinearity in optical fiber communication link have been discussed and highlighted. Desirable effects of nonlinearity in general and undesirable effects, in particular, in an optical fiber are enumerated with examples. Cross-phase modulation (XPM) and high-nonlinearity (HNL) glasses along with their advantages and disadvantages are spelled out with the help of their theories and applications in practical systems. Keywords Nonlinear • Pulse broadening • Polarization fluctuation • Pulse walk-off Introduction to Linearity and NonlinearityNonlinearity is very interesting and important phenomena particularly in the field of engineering and its applied areas. Usually, a misconception prevails about nonlinearity and its subsequent applications in engineering systems, which in fact, is incorrect. On the contrary, nonlinear behavior can effectively be exploited for many useful applications in engineering design and analysis. In order to understand nonlinearity in true prospective, the under-mentioned examples from daily life could be helpful for the purpose.While driving a vehicle, when a driver presses accelerator, the car speeds up proportionally to the acceleration, if the car gains 100 km/h speed in 6 s, this is a total linear behavior.On the other hand, if a person visits a departmental store where a single bar of chocolate costs $5; however, in case a deal is offered, that is, if a person buys more than one bar of chocolate, 20 % discount is offered. This exhibits a nonlinear behavior as the purchased items (chocolates) is not proportional to the money paid. Both of the above-mentioned examples complement the fact that nonlinearity can be at times useful as well.