Optical control of a digital phase shifter

A method for the optical control of digital phase shifters which significantly reduces the number of control lines required is described. The technique uses a simple cost-effective light-emitting diode (LED) source along with a MESFET detector and an A/D converter to generate the digital phase shifter command. The approach is independent of the phase shifter operating frequency and is compatible with monolithic microwave integrated circuit (MMIC) technology and parallel optical signal processing. Experimental results are presented for the optical control of a 6-b digital phase shifter. To provide 360 degrees of phase shift, 310 mu W of optical power are required.<>