LTE Signal Transmission Over a Linearized Analog Photonic Link With High Fidelity

This paper presents a concept and an implementation of a linearized analog photonic link for wideband wireless communication that yields improved adjacent channel leakage ratio (ACLR). The link consists of two parallel Mach-Zehnder modulators (MZMs) driven by two lasers, and a modified uni-traveling-carrier photodetector capable of outputting high RF power when assisted by an erbium-doped fiber amplifier. The third-order intermodulation (IMD3) attributed to the MZM transfer function is suppressed by asymmetric RF and optical feeding that impose a π-phase difference between the signals in the two MZM channels. Long-Term Evolution (LTE) signals of various bandwidths are used to validate this broadband linearization approach experimentally. It is demonstrated that with this approach the first ACLR (ACLR1) can be improved by 19.2 dB for a 10-MHz LTE signal and 18.1 dB for a 20-MHz LTE signal at the cost of approximately 2-dB link gain penalty.