A Reconfigurable Photonic Microwave Mixer Using a 90° Optical Hybrid

A reconfigurable photonic microwave mixer is proposed using a 90° optical hybrid. To perform the reconfigurable mixing, an optical carrier is split into two branches. One portion is intensity-modulated by an RF or intermediate frequency signal, and the other is driven by a local oscillator (LO). Each generates an optical sideband. The two sidebands from the two branches are introduced to the signal port and the LO port of an optical hybrid which typically has four output ports, namely, I
₁
, I
₂
, Q
₁
, and Q
₂
. When any one of the outputs is detected by a photodetector (PD), a single-ended mixer is obtained. If one of the combinations (I
₁
, I
₂
) and (Q
₁
, Q
₂
) is sent to a balanced PD, a balanced mixer is realized. When I
₁
(or I
₂
) and Q
₁
(or Q
₂
) are detected by two PDs, an I/Q mixer with quadrature outputs is achieved. When an electrical 90° hybrid is used to combine the two outputs of the I/Q mixer, image-reject mixing is implemented. A theoretical model is established to analyze the proposed mixer, and an experiment is also carried out. The results demonstrate that the proposed mixer can achieve reconfigurable mixing functions by simply changing the photodetection method.