Single sideband techniques for next generation low-cost UD-WDM coherent PONs

In this thesis, two applications for splitter-based, coherent passive optical networks (PONs) are investigated. Coherent technologies enable ultra-dense wavelength division multiplexing (UD-WDM), increasing the dedicated data rates per application, the power budget and the spectral efficiency of the network, all within a single fiber for bidirectional transmission. In these works, single sideband (SSB) technologies, along with RF modulations, are used to decrease complexity in the proposed networks. The first technique aims at using a single laser per transceiver along homodyne detection. It is accomplished by splitting the laser source for transmission and reception and wavelength-shifting (λshifting) the transmission branch, by using a dual-parallel Mach-Zehnder modulator (DP-MZM) operating in carrier-suppressed SSB modulation (CS-SSB). Thus, a single laser feeds both the transmitter and the receiver without spectral overlapping of the upstream (US) and downstream (DS) signals and their respective Rayleigh backscattering (RB) reflections. This also simplifies the wavelength management in the PON. The DP-MZM provides both λ-shifting and data modulation in the same operation, reducing insertion losses, optical complexity and costs. In the presented study, a bit rate of 4 Gbit/s in a quadrature-phase shift keying (QPSK) configuration is used to test the effect of channel spacing and roll-off factors of the pulse shaping filters. The results show power budget gains of 18 dB with a channel spacing as low as the symbol rate of the modulation. The second technique proposes and tests a simplified coherent architecture for the uplink transmission of mobile Fronthaul in a UD-WDM scheme. An analog implementation is proposed with phase-noise cancellation based on the SSB modulation of a dual-electroabsorption modulated laser (D-EML). Results show optical channel spacings of only 1.5 GHz and error-free signal recovery with a linewidth (Δߥ (per bit period product of Δߥ= ௕ܶ 1.2%, 3% with a reaching power as low as -40 dBm for 100 Mbit/s and - 37 dBm for 1 Gbit/s using a QPSK modulation