Regeneration of Differential Phase-Shift-Key Optical Modulated Signals

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Schematic of the differential phase-shift eration of optical differential phase-shift keying signals is keying regenerator of the present inventionSchematic of the cascaded phase-amplitude differential phase-shift keying regenerator
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Researchers
Guifang Li, Ph.D.
Kevin Croussore
Cheolhwan Kim, Ph.D.
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John Miner
Assistant Director 407.882.1136
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Regeneration of optical phase modulated signals

US Patent 7,369,779 B1

Systems, methods, apparatus and devices for all-optical regeneration of degraded optical signals in differential phase-shift-key systems

UCF scientists have developed an all-optical regenerator. It is capable of simultaneously restoring the optical phase of a Differential Phase-Shift-Key (DPSK) signal, providing signal amplification and reducing noise. This system uses phase sensitive amplifiers (PSA), for simultaneous regeneration of both amplitude and phase. The technology also has the added advantage of being able to operate in one of three modes: restoring only the original phase shift, restoring phase shift while at the same time limiting amplitude, or performing simultaneous phase and amplitude regeneration.

Technical Details

Differential Phase-Shift-Key (DPSK) is the favored format for long-haul optical transmission systems. This is because DPSK systems have high tolerance to amplitude noise when compared to on-off key systems. Transmitters of DPSK modulated signals have just two phases 0 and 180 but when transmitted through optical fibers, the phase shifts change, introducing phase noise. DPSK systems can suffer from both linear and non-linear noise. Several techniques have been proposed for non-linear noise management. Some are only effective if the noise is not allowed to accumulate. Other strategies include post transmission Non-Linear Phase Shift Compensation (NLPSC). While these work to eliminate the non-linear noise, they fail to address the linear. All of these techniques are applicable for optical regeneration of amplitude-modulated signals, not for DPSK signals. A DPSK regenerator is thus needed to restore the original pulse-pulse phase change to its original value by reducing noise.

Benefits

  • Reduces both linear and non-linear noise
  • Regenerates both phase and amplitude of degraded differential phase-shift-key optical signals

Applications

  • Long-haul transmission of optical phase modulator signals
  • Optical communication systems