Broadband transmission over injection-locked optical OFDM systems: Theory and design

In this paper an injection-locked optical orthogonal frequency-division multiplexing (ILO-OFDM) method is presented using an optically injection-locked laser. In an ILO-OFDM system, an optically injected semiconductor laser operating in stable locking is utilized to directly modulate the OFDM signal on the optical carrier intensity. To design this system, we first compute the optimal operating condition for the directly modulated injection-locked laser by numerically solving the rate equations. The goal is to achieve the maximum enhanced modulation bandwidth with desirable flatness and simultaneously reduce signal distortions due to the effects of laser nonlinearity. These properties of the injection-locked laser suggest an appealing solution for high-data-rate transmission using OFDM. Next, we design the ILO-OFDM system by directly modulating the RF OFDM signal on the injection-locked laser with the enhanced features. The performance of the proposed method is assessed by numerical simulations, and the advantages of this method over existing optical OFDM systems are explained.