A Novel Heterodyne Optical PLL for Phased Arrays

Abstract

A new coherent optical beamforming network principle that utilises a heterodyne optical phase locked loop (OPLL) incorporating a phase modulator, has been proposed and detailed theoritical studies have been made. A typical system with 200 MHz as the bandwidth for 0 dB open loop gain of the transmitter OPLL, a loop delay of 0.5 ns, a data rate of 131 Mb/s, and a receiver requiring a bit error rate of the order of 10⁻⁹' and a phase error of 1° is considered. It is shown that the proposed system can be easily hooked up using commercially available DFB lasers whereas stringent laser linewidth requirement for the existing system does not allow this.

Indexing terms:

• OPLL
• Laser line width
• Phase noise
• Shot noise
• OBFN
• Loop delay
• Phase error variance