All-Optical Photonic Microwave Phase Shifter Based on an Optical Filter With a Nonlinear Phase Response

A new photonic microwave phase shifting structure that can realize a continuous 0° to 360° phase shift with only little frequency dependent amplitude and phase variation over a wide frequency range is presented. It is based on controlling the amplitude and phase of the optical carrier and two antiphase RF modulation sidebands of two phase modulated optical signals by adjusting the wavelength of the optical carriers that fall on the rising and falling edges of an optical bandpass filter with a nonlinear phase response. The new photonic microwave phase shifter has a simple structure. It only requires one normal electro-optic phase modulator and one low-cost commercially available optical filter. It does not involve any electrical component, and has the advantages of small size, lightweight, and robust performance. Experimental results are presented which demonstrate the realization of a continuous 0° to 360° phase shift, with close to flat phase and amplitude response performance over a wideband microwave range.