| dc.description.abstract | In this thesis, we propose a coupling-weighted and velocity-tapered 3-dB splitter with a symmetric structure weighted by the Blackman function for C+L-band passive optical network (PON) applications. The broadband splitter is analyzed by the coupled-mode theory and simulated by the use of three-dimensional finite-difference beam propagation method (BPM). It is found that the power uniformity, wavelength dependent loss, excess loss and polarization dependent loss of the proposed 3-dB splitter in the whole C+L-band are better than 2.49E-3 dB, 0.018 dB, 0.14 dB, and 0.004 dB, respectively. It is evident that the 3-dB splitter can achieve the good performances for C+L-band passive optical network applications.
Furthermore, we extend the approach of the above 3-dB splitter to obtain variable splitting ratios by simply breaking the symmetry of the original design. A numerical solution for the broadband splitter with a variable splitting ratio is designed with wavelengths between 1.53 and 1.57 µm. The performance of the proposed splitter is also verified by using the BPM. It was found that a polynomial function of the splitting ratios accompanying a geometrical shift can be derived from the proposed splitter. The splitting ratio can be changed from 50:50 to 90:10 with this geometrical shift. The excess loss, crosstalk, polarization dependent loss, and splitting ratio variations against wavelength of the proposed splitter with wavelengths between 1.53 and 1.57 µm are better than 0.139 dB, −22.75 dB, 0.006 dB, and 0.335%, respectively. Obviously, the proposed splitter with variable splitting ratio retains the advantages of the symmetric design, such as low excess loss, low crosstalk, polarization insensitivity, and wavelength insensitivity.
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