It is shown experimentally that impairments induced by dispersion and Kerr nonlinearity can be compensated digitally for polarization-division multiplexed wavelength division multiplexing (WDM) transmission. The method of digital backward propagation based on solving the Manakov equation can be used to efficiently compensate for the nonlinear interactions between orthogonally polarized channels.

The phenomenon of fast-light pulse propagation has seen renewed interest in recent years, but its relationship to the speed of information transfer is still being debated. In this paper, we define the speed of information transfer as the propagation speed of a point of constant signal-to-noise ratio (SNR) on the leading edge of a signal pulse. We use standard telecommunication analysis to include the effects of noise so that the bit-error rate (BER) can be calculated as a function of a variable decision time. We introduce the concept of a time-dependent Q-factor so that pulse arrival times can be compared at equivalent BERs. We show that when receiver noise is included in a gain-assisted fast-light system, the measured speed of information transfer can exceed the speed of light for an equivalent pulse travelling through a vacuum.

We report the design and fabrication of high-performance 650-nm lasers using a novel wafer structure that offers substantially independent control of the vertical far field and of the optical confinement factor. By incorporating a graded V-shaped layer into the epitaxial structure, a low divergence can be realized while retaining high optical overlap with the quantum wells and, therefore, a low threshold current. Broad-area lasers (BALs) were fabricated for a range of designs, and close agreement was obtained between the modeling and the experiment.

Optical parametric oscillators (OPOs) have now been realized in a CMOS-style process by exploiting nonlinear four-wave mixing. Such multiwavelength sources bring the prospect of ultrafast chip-to-chip optical data communications a step closer.