Channelized amplification of RF signal based on actively mode locked fiber laser

Abstract

A new approach for implementing channelized radio frequency (RF) signals amplification based on actively mode locked laser (MLL) is proposed and demonstrated. The channelized amplification (CA) is based on the mode-locking gain of the fiber ring laser while the frequency of RF signal applied to Mach–Zehnder modulator (MZM) in the fiber laser matching the fundamental or harmonic of the laser cavity mode. The experimental results show that high RF regenerative gain with a maximum 44 dB and high Q factor normally greater than 105 can be achieved with this approach of CA. By electrically tuning the fiber delay line incorporated in the ring laser so as to scan the center frequency of the channelized amplifier, spectrum recognition of quadrature phase shift keying (QPSK) modulated electro-magnetic signal with low power density is successfully implemented. The limit of input power and linear operating dynamic range is also measured and discussed.