Generation of a multi-wavelength Brillouin erbium fiber laser with frequency spacing versatility

Abstract

This dissertation proposes the production of a multi-wavelength laser, all in fiber, with different frequency spacings, using a non-linear effect, stimulated Brillouin scattering (SBS), combined with the use of a erbium doped fiber amplifier (EDFA). In a dual loop cavity configuration and 25km Non-Zero Dispersion-Shifted Fiber (NZDSF) fibers as the gain medium. Lasers were first observed in the 1960s and are considered one of the significant technological advances of the 20th century. Many different laser systems have been developed and tested and have been used in a variety of applications. Optical fiber lasers and amplifiers have been attached much attention from the scientific community. But it was only in 1980, after a significant reduction in propagation losses and with the development of EDFA’s, which made it possible to transport light over tens of kilometers of distance, that this technology has grown exponentially. In fact, despite the advances made, there is still a margin for this technology to progress, the biggest challenge being to improve performance, and overcoming some limiting factors, highlighting, the early appearance of non-linear effects, such as Raman scattering and Brillouin scattering, which cause the loss of incident power and cause the fading of the transmitted information. During the studies of these non-linear effects, several advantages and ways were found to combine them with the gain of the light beam and use them as amplifiers and generators, using different arrangements and techniques. Multi-wavelength lasers (MWL) came to the fore after the development of wave division multiplexing (WDM) technology, which allows more channels to be carried on a single medium. The nonlinear Brillouin effect has a small frequency shift, about 10 GHz in silica, and a relatively low threshold power for generating the effect, in addition to being stable at room temperatures and tunable narrow linewidth frequency scheme, all of which make the multi-wavelength Brillouin laser (MWBL) hot spot on research, as it is easy to cascade and transmit all waves within the same communication band. It can also be produced entirely in optical fiber, which confers reliability, efficiency, excellent quality of the modal beam, low maintenance and they are compact structures. Combining these qualities, multi-wavelength Brillouin fiber lasers (MWBFL) can be used in various applications, such as sensing and dense wave division multiplexing (DWDM). To implement this dissertation, a pump source with a narrow linewidth, about 1 kHz, was used, which allowed reached a low power threshold, approximately 1 mW, necessary to stimulate the non-linear effect in the fiber. For the choice of the Brillouin gain medium, three fibers with different characteristics were tested and the one that presented the best performance in terms of power threshold, frequency shift, and amplification was chosen, NZDSF of 25 km. For linear gain medium, an erbium-doped fiber (EDF), 10 m long, pumped with a light source at 1474 nm was chosen. Finally, for laser cascading generating multiple wavelengths, three configurations were used that made it possible to increase the frequency spacing by up to three times the silica standard, approximately 9.08 GHz for the single array, 19.56 GHz for the double array, and 29.12 GHz for the triple frequency spacing.