We demonstrate wavelength-division multiplexed (WDM) and mode-division multiplexed (MDM) transmission over a
fiber recirculating loop comprising of a 25-km span of low differential mode group dispersion (DMGD) few-mode fiber
carrying the LP01 and LP11 mode groups, and an inline few-mode erbium-doped fiber amplifier (FM-EDFA) providing
low mode-dependent gain (MDG) per span. We successfully transmitted a 10λ × 6 × 28-Gbaud QPSK signal over a
distance of 700 km.
In response to ever growing data traffic, significant efforts are being made to increase optical network capacity.
One promising candidate is mode-division multiplexing (MDM) in few-mode fibers, which uses space as a new
information-bearing dimension. A fundamental element for MDM is a modal transformer. Modal transformation
can be implemented in a free-space basis by using multi-region phase plates. In this work we present the design,
fabrication and characterization of monolithic binary phase plates by highly-uniform Ag<sup>+</sup>/Na<sup>+</sup> ion-exchange in
glass. Diffracted optical field intensities have been measured and high quality mode transformation has been
Interchannel nonlinear impairments are one of the major limitations to the channel capacity and transmission distance in
WDM systems. It is shown that nonlinear impairments arising from cross-phase modulation between two independent
WDM channels can be compensated. Advanced digital back propagation algorithms based on advanced split step method
allow for compensating inter-channel nonlinear impairments with low complexity. With the new algorithm, the complexity
of compensating inter-channel impairments is comparable to the complexity required for intra-channel impairments.
A nonlinear integrated optical device, presenting an intrinsic bistable behaviour by means of the Kerr effect produced by counterpropagating beams, is presented. The proposed feedback mechanism, which preserves the spatial shape of the beams, is based on the transverse modal coupling of the beams to optical fibers through integrated multilenses. An optimum waveguiding design is presented to allow both the fabrication of this device by hybrid
integration on glass and show the results of bistability.