On Bit and Power Loading for OFDM Over SI-POF

A new methodology is proposed for the modeling of practical uncoded bit and power loading schemes for OFDM, based on the assumption of a uniform transmit power spectrum. The accuracy of this technique, both in terms of predicted maximum data rate and occupied bandwidth, is demonstrated analytically for an Intensity Modulated/Direct Detected (IM/DD) system over Step Index Plastic Optical Fibers (SI-POF). It is shown that both this new methodology and the well known water pouring theorem accurately predict the maximum achievable data rate in practical uncoded systems; however, it is also demonstrated that the new methodology is a better predictor of the bandwidth occupied by the transmit signal, thus providing an important analytical tool for system designers. The analysis presented is also experimentally verified using an IM/DD optical system employing a directly modulated Resonant Cavity Light Emitting Diode (RCLED) light source and several lengths of 1 mm SI-POF.