Rogério Dionísio

By Rogerio Pais Dionisio

Throughout the years, the expanded search and flow of information led to an expansion of traffic intensity in today’s optical communication systems. Coherent communications, using the amplitude and phase of the optical wave, resurface as one of the transmission methods to increase the effective bandwidth of optical channels. In this framework, this chapter presents a study on all-optical format conversion of modulated signals, using exclusively interferometric techniques through wavelength conversion, based on Mach-Zehnder interferometers with semiconductor optical amplifiers (MZI-SOA). This technique, when applied in interconnection nodes between optical networks with different bit rates and modulation formats, allows a better efficiency and scalability of the network. The chapter presents an experimental characterization of the static and dynamic properties of the MZI-SOA and explores all-optical techniques for the conversion from amplitude modulation to phase modulation. Finally, it briefly presents the potential of MZI-SOAs for the conversion of amplitude signals to more advanced modulation formats, such as quadrature phase shift keying (QPSK) and quadrature amplitude modulation (QAM) signals.

Part of the book: Optical Interferometry

By Rogério Dionísio

Fiber Bragg grating is widely used in optical fiber applications as a filter or a sensor due to its compact size and high sensitivity to physical conditions, such as temperature and strain. The purpose of this chapter is to describe the implementation and characterization of two tuning methods for optical fiber Bragg gratings, varying the temperature or the length of the fiber. Among the methods using mechanical deformation, compression of the fiber by bending a flexible sheet aggregated with the Bragg grating has shown very interesting tuning results, reaching 19.0 nm with minimum reflection bandwidth variation over the entire tuning range. Stretching the fiber has presented several drawbacks, including breaking of the fiber and a lower tuning range of 4.9 nm. Temperature tuning technique presents good linearity between tuning range and temperature variation but at the cost of a low tuning range (0.4 nm) and a permanent high current electrical source.

Part of the book: Optical Interferometry