  Optical orthogonal frequency division multiplexing (O-OFDM) schemes are
variations of OFDM schemes which produce non-negative signals.
Asymmetrically-clipped O-OFDM (ACO-OFDM) is a single-layer O-OFDM scheme, whose
spectral efficiency can be enhanced by adopting multiple ACO-OFDM layers or a
combination of ACO-OFDM and other O-OFDM schemes. However, since symbol
detection in such enhanced ACO-OFDM (eACO-OFDM) is done iteratively, erroneous
detection leads to residual clipping noise (RCN) which can degrade performance
in practice. Thus, it is important to develop an accurate model for RCN which
can be used to design RCN-aware eACO-OFDM schemes. To this end, this paper
provides a mathematical analysis of RCN leading to an accurate model of RCN
power. The obtained model is used to analyze the performance of various
eACO-OFDM schemes. It is shown that the model provides an accurate evaluation
of symbol error rate (SER), which would be underestimated if RCN is ignored.
Moreover, the model is shown to be useful for designing an RCN-aware resource
allocation that increases the robustness of the system in terms of meeting a
target SER, compared to an RCN-unaware design.
