Time-to-space conversion of sub-picosecond waveforms at 1.55 µm in bulk and slab waveguide nonlinear media

Ever growing demand for internet data transmission capacity drives the search for innovative optical communications transmission and signal processing techniques. Optical time division multiplexing (OTDM) enables high baud rate data transmission on a single wavelength channel which, combined with advanced modulation formats, can maximize spectral efficiency. Time-to-space conversion is a complementary signal processing technique for all-optical serial-to-parallel demultiplexing of a Terabit/s OTDM channel. It is based on sum-frequency generation (SFG) between signal and reference pulses in a spectral processor and converts a time domain (serial) ultrashort signal waveform to a space domain (parallel) output image. We present two generations of time-to-space conversion, first in a bulk nonlinear crystal and then in a slab nonlinear waveguide. A ~40ps time window of operation and sub-picosecond output image resolution were achieved, showing the potential of this technique for Terabit/s OTDM demultiplexing. In addition, the quasi-monochromatic SFG signal generated implies the possibility for coherent detection of the demultiplexed output tributaries, enabling compatibility with advanced modulation formats.