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Optical generation of low-phase noise microwave signals using nonlinear MZM and ultra-long SOA

We propose and demonstrate a tunable 50 GHz photonic synthesizer using nonlinearities in a Mach-Zehnder modulator (MZM) in conjunction with the four-wave mixing (FWM) effect in an ultra-long semiconductor optical amplifier (UL-SOA). The operation principle is based on an external modulation scheme using a low phase noise local oscillator (LO) source to multiply the LO frequency in the optical domain. We experimentally demonstrate tunable and low phase noise millimeter-wave (mm-wave) signal generation up to 50 GHz using a low frequency reference LO source. A multiplication of eight-times the LO frequency has been achieved resulting from the nonlinear behavior of the MZM in conjunction with the UL-SOA. Phase noise measurements of the fundamental LO frequency as well as of the generated mm-wave signal with a multiplication factor of N=8 have shown phase noise levels of −96 dBc/Hz and −78 dBc/Hz at 10 kHz offset from the carrier, respectively.