Microwave frequency doubling by synchronising and polarisation multiplexing the optical signals from a dual‐output Mach–Zehnder modulator

Abstract

A technique is experimentally demonstrated to double the frequency of a microwave signal by synchronising and polarisation multiplexing the optical signals from a dual-output Mach-Zehnder modulator. The frequency-doubled tone at 4 GHz is 41.2 dB stronger than the residual fundamental-frequency tone. The strongest side tone is found at 12 GHz (sixth order) and is suppressed by 32.7 dB. The phase noise of the frequency-doubled signal is −104.1 dBc/Hz at an offset of 10 kHz, an increase of 6.7 dB over that of the initial signal. This technique does not rely on electronic or optical filters or amplifiers and is demonstrated using commercial off-the-shelf components.

Selectable microwave‐frequency doubling and quadrupling via optical path‐length tuning

“…The optical signal exiting this PBC is thus comprised of two orthogonally polarised light waves whose optical powers sum together with negligible interference; this polarisation multiplexing allows for the incoherent addition of the two intermediate signals. Note that polarisation multiplexing was employed by the authors in a different method for microwave frequency doubling [11]; however, that method made use of inversely shaped signals from a dual ‐output MZM, and such a method does not support frequency selectability by means of a VODL.…”

“…Introduction: Multiplication of microwave signals to higher frequencies has leveraged the optical domain [1][2][3][4][5][6][7][8][9][10][11], where optical signals benefit from the relatively low loss and high bandwidth of optical waveguides and components [1][2][3]. Such multiplication techniques have been applied, for example, to generate local-oscillator signals for upconversion [4][5][6].…”

“…Note that polarisation multiplexing was employed by the authors in a different method for microwave frequency doubling [11]; however, that method made use of inversely shaped signals from a dual-output MZM, and such a method does not support frequency selectability by means of a VODL.…”