Performance Analysis on Using Period-One Oscillation of Optically Injected Semiconductor Lasers for Radio-Over-Fiber Uplinks

Nonlinear period-one (P1) dynamics of a semiconductor laser are investigated for radio-over-fiber uplink transmission. By optical injection locking, the laser in a base station is driven into the P1 oscillation state, which is further locked by the uplink microwave signal through modulation on the bias current. Due to double locking by both the optical injection and current modulation, the uplink microwave signal is converted into an optical signal for transmission to the central office. Comprehensive numerical simulations reveal that the proposed uplink transmission based on the P1 state provides wide, continuous, and optically-controlled tunability for the uplink subcarrier frequency, which exceeds the laser modulation bandwidth. The laser with a relaxation resonance frequency of only 10.25 GHz is shown to support subcarrier frequencies reaching 60 GHz. Compared to the commonly used stable injection locking state and the free-running state, the proposed P1 state generates the microwave oscillation by the inherent nonlinear dynamics and thus reduces the requirement on the uplink signal strength for low-error transmission. Both electrical demodulation and all-optical demodulation are investigated, where the latter is found to be better in terms of the immunity to dispersion and the speed requirement on optoelectronic conversion. The results illustrate the capability of using the P1 oscillation state for optically controlled uplink transmissions.