The channel estimation result of non-pilot subcarriers mainly depends on adjacent pilot subcarriers. A linear
interpolation algorithm has been applied to the channel estimation of non-pilot subcarriers. The performance of
interpolation algorithm has been simulated in a 10Gb/s direct-detection optical orthogonal frequency division
multiplexing (DDO-OFDM) communication system. Constellation convergence is greatly improved.
To achieve adaptive modulation technology in Optical Orthogonal Frequency Division Multiplexing
(OOFDM) system, the channel estimation has to be made first and foremost. By imposing a symbol of
pilot signals after a certain amount symbols, the frequency response of a given transmission link can be
given out. The modulation format can be determined according to the frequency response. A high (low)
modulation format is used on a sub-carrier suffering a low (high) transmission loss. The modulation
format can be adjusted adaptively.
Within the realm of OFDM research, (peak-to-average power ratio)PAPR is an important object to be considered.
Overlarge PAPR can deteriorate the linearity of the wireless systems. In this paper, we interpret the concept of PAPR in
optical OFDM system and testify that the modulation method in sub-carriers and nonlinear effects can affect PAPR in
the optical OFDM system. Through simulation, PAPR problem stand out while considering OFDM in optical
transmission technology, so reducing it has become an important subject in optical OFDM system.