In the first part of the talk, nonlinear effects in optical fibers such as self-phase modulation and four wave mixing will be reviewed. To mitigate fiber nonlinear impairments, digital/optical techniques will be discussed. A digital technique based on multi-stage perturbation theory is used to compensate for fiber nonlinearities at the DSP unit of the coherent receiver. It is found that performance can be significantly improved by increasing the number stages and surprisingly, computational cost decreases with the number of stages. Digital techniques can not compensate for inter-channel nonlinear impairments in optical networks since the receiver does not have information on the other channels that are dropped elsewhere. However, optical back propagation modules used at every node of an optical network can compensate for both intra- and inter- channel nonlinear impairments. An OBP module consisting of optical phase conjugator (OPC), dispersion-decreasing fibers (DDF) and amplifiers can compensate for the fiber nonlinearity exactly. An analytical expression for the dispersion profile of DDF for the exact nonlinear compensation is developed. The results show that the performance can be significantly improved using the OBP module at the receiver. In the second part of the talk, nonlinear effects in optical microcavity  such as  such as microsphere and toroid will be discussed. For example, in silica microsphere, light undergoes multiple total internal reflections along the silica-air boundary and hence, it is confined within the microsphere for a long time.  Only certain discrete frequency components can be confined for a long time and they are known as whispering gallery modes. The impact of Kerr nonlinearity on the resonant modes of a microcavity will be discussed.

Speaker(s): Shiva Kumar,

Location:
Room: room 603
Bldg: McConnell Eng. Building
McGill University
3480 rue University
Montreal, Quebec
H3A0E9