Analisi e sperimentazione del tempo di build-up di un trasmettitore autosintonizzante

Recently a self-seeding modulatable cavity based on reflective semiconductor optical amplifier (RSOA) has been proposed as a possible solution for low cost transmitter in a Wavelength Division Multiplexed Passive Optical Network (WDM-PON). In this architecture a resonant cavity is established between the RSOA mirror at the Optical Network Unit (ONU) and the mirror at the Remote Node (RN). The AWG present at the RN acts as a wavelength-selective element. The cavity length is defined by the drop fiber which connect the ONU and the RN. This thesis focuses on the analysis and the experimental evaluation of the build-up time of the cavity, i.e., the time necessary to reach steady state condition, both in terms of optical power and spectral linewidth, with an approach that differs from literature as it takes into account also the spectral behavior of the source. This goal is accomplished by exploiting an electrically-controllable Variable Optical Attenuator (VOA) with low response time to drive the time in which the cavity remains in ON state, thus allowing to control the duration of both switch on and switch off time. Measurements with different kind of fibers and AWG shapes and bandwidth have been done in laboratory and widely commented in this work. The same approach is used to evaluate the first cavity roundtrips, clearly evidencing that the optical spectrum is progressively narrowed by subsequent passages through the AWG and by the nonlinear RSOA injection, thus validating the theoretical model proposed to describe the self-seeding transmitter. With the same setup also Relative Intensity Noise (RIN) measurements in the time domain have been performed by gating the different roundtrips of the building optical power in the cavity. It is surprisingly discovered that while power and RIN reach quite quickly their steady state value, the optical spectrum needs more than 100 roundtrips. This value varies according to the filter shapes and bandwidth and gain condition of the cavity.