Multi-channel mm-wave generation by frequency quadrupling using an optical modulator and a cascaded silicon microring filter

In this paper we propose and demonstrate a technique for multi-channel optical mm-wave signal generation by frequency quadrupling. By setting the DC bias of a Mach-Zehnder electro-optic modulator (MZM) to its transmission maximum, second order sidebands are generated while the first order sidebands can be suppressed. In addition to the two peaks of the second order sidebands, the output of the MZM also contains the input carrier frequency component. A high performance optical filter (a microring notch filter) is used to remove the optical carrier, and the remaining two second order sidebands can beat together in a photodetector at the antenna site in the radio-over-fiber (ROF) system, thus generating a mm-wave which has a frequency equal to four times the local oscillator frequency.