System, method, and apparatus for high-sensitivity optical detection

摘要

An apparatus transmits data using a format where information bits intended for transmission are mapped into symbols each carrying a plurality of bits, some of which are encoded through pulse position modulation (PPM) format and the rest of which are encoded through an additional modulation format on each PPM pulse. The additional modulation format for the PPM pulse may be at least one of a polarization-division-multiplexed (PDM) modulation, phase-shift keying (PSK) modulation, polarization shift keying (PolSK) modulation, amplitude modulation (AM), quadrature-amplitude modulation (QAM) modulation, or a combination thereof. In one embodiment, the additional modulation of the PPM pulses is through polarization-division-multiplexed quadrature-phase-shift keying (PDM-QPSK). The unique combined use of PDM-QPSK and PPM produces much higher receiver sensitivity than either PPM or PDM-QPSK alone.

主权项

1. A method comprising:
encoding by a processor a first non-zero portion of a plurality of bits for a symbol through at least one slot position corresponding to a pulse position modulation (PPM) format; encoding by the processor a second different non-zero portion of the plurality of bits for the symbol on the at least one slot position through an additional modulation format; and modulating a signal including the symbol onto an optical carrier by an optical modulator.