Generation of quaternary‐amplitude microwave signals by using a new optical heterodyne technique

We propose and experimentally investigate a new technique, based on optical heterodyne generation, which converts two optical binary amplitude‐shift keyed (2‐ASK) into a single microwave quaternary ASK (4‐ASK) one. Results show that 4‐ASK signals are properly generated even when the 2‐ASK signals are propagated through 40 km optical links from a geographically distributed optical network under real conditions of temperature, pressure, humidity, and wind.