Developing a flexible network to fully utilize the existing spectral resource is a hot topic in the novel paradigm of optical transmission systems. In this thesis, I analysed hybrid modulation formats as an effective technique for the implementation of flexible transponders that are capable of trading-off the delivered data rate by the light path quality of transmission with a finer granularity. The flexible transponder is an enabling technology to introduce the elastic paradigm in the state-of-the-art networks, while maintaining compatibility with the installed equipment, including fibers, mux-demux and ROADMs, as required by telecommunication operators willing to exploit fixed grid WDM transmission. Time division hybrid modulation format (TDHMF) is presented as the first solution. Through combining two modulation formats in the time division, TDHMF can achieve arbitrary bit-per-symbol, and provide a huge amount of flexibilities to the network. A comprehensive theoretical assessment of the back-to-back performances is also introduced. In particular, four different transmitter operation strategies are proposed and evaluated. They are the constant power strategy, the same Euclidean distance strategy, the same BER strategy and the minimum BER strategy. Through the back-to-back performance comparison, the same BER strategy is chosen as the most promising strategy, mainly due to its comparable sensitivity performance and the potential of transponder simplification. This thesis also prepared another solution, which is Flexible M-PAM modulation format (FlexPAM). It is a hybrid of different M-PAMs in all four quadrature of the optical field. Although it providing less flexibility compared to TDHMF, FlexPAM has its unique advantage in two main aspect. Firstly, the inherently time consistent frame structure feature of FlexPAM may require an identical and simple transponder, which is very crucial from the operators point of view. Secondly, from the network perspective, the operators can assign each quadrature of FlexPAM to a specific network tributary and select an M-PAM according to the actual network conditions. Similar to TDHMF, both general characterization and theoretical formulation are discussed in detail. Then, the back-to-back performance of FlexPAM, including the comparison of different transmitter strategies that similar to the one of TDHMF, has been fully studied. The same BER strategy again provided a negligible SNR penalty in contrast to the optimal strategy. At the same time, by using the same FEC code for both M-PAM, the same BER strategy may require a simpler signal processing procedure and reduce the complexity. A subsequent work after the back-to-back analysis is the signal non-linear propagation evaluation of these two novel modulation formats. This thesis provide an extensive simulation analysis on the propagation of a Nyquist-WDM channel comb over an uncompensated and amplified fiber link. Due to the power unbalance in the time division (TDHMF) or in the polarization/quadrature (FlexPAM), the mixed modulation formats normally have some penalty against to the GN-model predictions. To improve their propagation performance, a simple polarization interleaving countermeasure is presented. It works well on TDHMF and has a significant impact on certain case of FlexPAM. Furthermore, the power ratio tuning is also proposed as an easy implemented and effective tool to improve the propagation performance. In the end, the propagation performance of both TDHMF and FlexPAM are compared in terms of the maximum reach versus system net bit rate, in addition, both with and without countermeasures conditions were considered. The results of this investigation showed that TDHMF has almost the same performance as the GN model predictions after the countermeasures employed. FlexPAM can provide a comparable propagation performance in contrast to the GN model predictions. Considering the advantages that mentioned before, the propagation performance of FlexPAM is acceptable.

mixed modulation format for future optical transmission systems / Li, Rixin. - (2016). [10.6092/polito/porto/2641453]

mixed modulation format for future optical transmission systems

LI, RIXIN
2016

Abstract

Developing a flexible network to fully utilize the existing spectral resource is a hot topic in the novel paradigm of optical transmission systems. In this thesis, I analysed hybrid modulation formats as an effective technique for the implementation of flexible transponders that are capable of trading-off the delivered data rate by the light path quality of transmission with a finer granularity. The flexible transponder is an enabling technology to introduce the elastic paradigm in the state-of-the-art networks, while maintaining compatibility with the installed equipment, including fibers, mux-demux and ROADMs, as required by telecommunication operators willing to exploit fixed grid WDM transmission. Time division hybrid modulation format (TDHMF) is presented as the first solution. Through combining two modulation formats in the time division, TDHMF can achieve arbitrary bit-per-symbol, and provide a huge amount of flexibilities to the network. A comprehensive theoretical assessment of the back-to-back performances is also introduced. In particular, four different transmitter operation strategies are proposed and evaluated. They are the constant power strategy, the same Euclidean distance strategy, the same BER strategy and the minimum BER strategy. Through the back-to-back performance comparison, the same BER strategy is chosen as the most promising strategy, mainly due to its comparable sensitivity performance and the potential of transponder simplification. This thesis also prepared another solution, which is Flexible M-PAM modulation format (FlexPAM). It is a hybrid of different M-PAMs in all four quadrature of the optical field. Although it providing less flexibility compared to TDHMF, FlexPAM has its unique advantage in two main aspect. Firstly, the inherently time consistent frame structure feature of FlexPAM may require an identical and simple transponder, which is very crucial from the operators point of view. Secondly, from the network perspective, the operators can assign each quadrature of FlexPAM to a specific network tributary and select an M-PAM according to the actual network conditions. Similar to TDHMF, both general characterization and theoretical formulation are discussed in detail. Then, the back-to-back performance of FlexPAM, including the comparison of different transmitter strategies that similar to the one of TDHMF, has been fully studied. The same BER strategy again provided a negligible SNR penalty in contrast to the optimal strategy. At the same time, by using the same FEC code for both M-PAM, the same BER strategy may require a simpler signal processing procedure and reduce the complexity. A subsequent work after the back-to-back analysis is the signal non-linear propagation evaluation of these two novel modulation formats. This thesis provide an extensive simulation analysis on the propagation of a Nyquist-WDM channel comb over an uncompensated and amplified fiber link. Due to the power unbalance in the time division (TDHMF) or in the polarization/quadrature (FlexPAM), the mixed modulation formats normally have some penalty against to the GN-model predictions. To improve their propagation performance, a simple polarization interleaving countermeasure is presented. It works well on TDHMF and has a significant impact on certain case of FlexPAM. Furthermore, the power ratio tuning is also proposed as an easy implemented and effective tool to improve the propagation performance. In the end, the propagation performance of both TDHMF and FlexPAM are compared in terms of the maximum reach versus system net bit rate, in addition, both with and without countermeasures conditions were considered. The results of this investigation showed that TDHMF has almost the same performance as the GN model predictions after the countermeasures employed. FlexPAM can provide a comparable propagation performance in contrast to the GN model predictions. Considering the advantages that mentioned before, the propagation performance of FlexPAM is acceptable.
2016
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2641453
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