Abstract
Phase modulated sub-picosecond pulses are converted by a time-to-space processor to quasi-monochromatic spatial beams that are spatially demultiplexed and coherently detected in real-time. The time-to-space processor, based on sum-frequency generation (SFG), serves as a serial-to-parallel converter, reducing the temporal bandwidth of the ultrashort pulse to match the bandwidth of optoelectronic receivers. As the SFG process is phase preserving, we demonstrate homodyne coherent detection of phase modulated temporal pulses by mixing the demultiplexed SFG beam with a narrow linewidth local oscillator (LO) resulting in single-shot phase detection of the converted pulses at a balanced detector. Positively and negatively phase-modulated signal pulses are individually detected and LO shot noise limited operation is achieved. This demonstration of real-time demultiplexing followed by single-shot full-field detection of individual pulses, highlights the potential of time-to-space conversion for ultrahigh bit rate optical communications and data processing applications.
Highlights
The growth trend in global communications traffic shows no sign of slowing, whereas current optical communications networks based on wavelength division multiplexing (WDM) are nearing their available bandwidth limit [1]
We propose and demonstrate the time-to-space conversion technique for serial-to-parallel demultiplexing of a high bit rate OTDM channel, including recovery of phase information by coherent detection of the demultiplexed narrowband pulses with a single local oscillator (LO) source
In conclusion we have demonstrated real-time demultiplexing to the spatial domain and single-shot coherent detection of a phase modulated ultrashort pulse train by time-tospace conversion
Summary
The growth trend in global communications traffic shows no sign of slowing, whereas current optical communications networks based on wavelength division multiplexing (WDM) are nearing their available bandwidth limit [1]. Recently deployed optical networks utilize polarization multiplexing and 2 bits-per-symbol modulation of an electronically generated 25 Gbaud/s serial channel to reach singlewavelength channel data rates of100 Gb/s Another advantage of coherent detection is apparent when it is combined with digital signal processing (DSP). OTDM demultiplexing is more challenging and several demultiplexing techniques have been investigated These include the nonlinear optical loop mirror [4, 5], XPM-based Mach-Zehnder switch [6, 7], FWM-based spectral filtering extraction [8, 9] and coherent detection by parallel optical sampling with a pulsed local oscillator [10]. We propose and demonstrate the time-to-space conversion technique for serial-to-parallel demultiplexing of a high bit rate OTDM channel, including recovery of phase information by coherent detection of the demultiplexed narrowband pulses with a single LO source. This result supports the potential of time-to-space conversion for high bit rate OTDM demultiplexing applications
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