Patent ID: 9641374
Date: 2017-05-02
CPC Classifications: H04B,H04L

Claim:
1. A direct-detected orthogonal frequency-division multiplexing (DD-OFDM) optical signal transmitter, comprising: an electrical-to-optical (E/O) converter; a first transmit chain operable for: performing operations to convert an input data stream into signals to be transmitted, the operations comprising: dividing the input data stream into symbols; modulating the symbols onto subcarriers; adjusting at least one of the subcarriers according to a signal-to-noise ratio of a respective subcarrier by at least one of amplifying a signal power of the respective subcarrier or increasing a number of bits of the respective subcarrier; and inverse fast Fourier transformations of the symbols; and selectively performing dispersion pre-compensation digital signal processing to generate in-phase and quadrature phase (I/Q) signals that are output to the E/O converter, the I/Q signals including a first I/Q signal generated from the at least one of the subcarriers adjusted according to the signal-to-noise ratio; a first digital-to-analog converter (DAC) operable for receiving in-phase components of the I/Q signals and for outputting analog versions of the in-phase components to the E/O converter; a second DAC operable for receiving quadrature phase components of the I/Q signals and for outputting analog versions of the quadrature phase components to the E/O converter; and a second transmit chain, wherein, if the dispersion pre-compensation is bypassed, the first DAC receives first signals from the first transmit chain and outputs analog versions of the first signals to the E/O converter, and the second DAC receives second signals from the second transmit chain and outputs analog versions of the second signals to a second E/O converter, and wherein the first signals and the second signals have in-phase components but not quadrature phase components.