title: Power margin improvement for OFDMA-PON using hierarchical modulation.
abstract: We propose and experimentally demonstrate a hierarchical modulation scheme to improve power margin for orthogonal frequency division multiple access-passive optical networks (OFDMA-PONs). In a PON system, under the same launched optical power, optical network units (ONUs) have different power margins due to unequal distribution fiber lengths. The power margin of the PON system is determined by the ONU with the lowest power margin. In our proposed scheme, ONUs with long and short distribution fibers are grouped together, and downstream signals for the paired ONUs are mapped onto the same OFDM subcarriers using hierarchical modulation. In a pair of ONUs, part of the power margin of the ONU with short distribution fiber is re-allocated to the ONU with long distribution fiber. Therefore, the power margin of the ONU with the longest distribution fiber can be increased, leading to the power margin improvement of the PON system. Experimental results show that the hierarchical modulation scheme improves the power margin by 2.7 dB for an OFDMA-PON system, which can be used to support more users or extend transmission distance.
authors.affiliation: State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Pan
authors.initials: P
authors.lastname: Cao
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Hu
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Zhuang
authors.forename: Liang
authors.initials: L
authors.lastname: Zhang
authors.forename: Qingjiang
authors.initials: Q
authors.lastname: Chang
authors.forename: Qi
authors.initials: Q
authors.lastname: Yang
authors.forename: Rong
authors.initials: R
authors.lastname: Hu
authors.forename: Yikai
authors.initials: Y
authors.lastname: Su
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D017076:Computer-Aided Design; D004735:Energy Transfer; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D008962:Models, Theoretical; D013685:Telecommunications / Q000295:instrumentation*