Directly modulated semiconductor-laser-fed photonic delay line with ferroelectric liquid crystals

A 3-bit binary photonic delay line is demonstrated at 1 GHz by use of a directly modulated semiconductor laser and remote interconnection fiber optics. Three types of free-space delay-bit geometries are tested for 5.69-ns, 1.67-ns, and 8.8-ps designed delay bits. This is the first time, to our knowledge, that a photonic delay line is demonstrated with ferroelectric liquid-crystal optical on-off devices for optical path switching and active polarization noise filtering. Three-dimensional imaging optics and antireflection-coated optics (for all but five components) are used successfully to minimize photonic delay-line insertion losses and interchannel cross talk. The 3-bit system is fully characterized for measured and designed performance.