Reconfigurable Optical Recognition of Independent Data Patterns in a QPSK Data Stream Using Nonlinear Wave Mixing and Time or Wavelength Multiplexing

Optical signal processing (OSP) has the potential to enable line-rate processing functionalities in optical communication networks through direct operation on optical data and avoidance of optical-to-electrical-to-optical (OEO) conversion. One such functionality is optical pattern recognition, in which the location of target patterns in the transmitted optical data stream is identified; common optical data formats include quadrature-phase-shift-keying (QPSK) data. Whereas prior approaches have performed optical pattern recognition to locate a single pattern in a QPSK optical data stream, it might be advantageous to optically recognize multiple patterns simultaneously. In this paper, we experimentally demonstrate optical recognition of multiple QPSK patterns using two approaches based on nonlinear wave mixing, one using time multiplexing and one using wavelength multiplexing. In the intra-symbol time multiplexing (IS-TM) approach: (i) the multiple target patterns are encoded on the phases of auxiliary patterns at different time instances, and (ii) the nonlinear wave mixing generates a single output representing the multiple pattern occurrences at different instances. Using IS-TM, we recognize (i) 2 patterns with 2 or 3 symbols for 2- and 3-Gbaud rates; and (ii) 3 patterns with 2 or 3 symbols for 1-Gbaud input QPSK signals. In the wavelength multiplexing approach: (i) the multiple target patterns are encoded on the phases of separate continuous wave (CW) pumps at different wavelengths, and (ii) the nonlinear wave mixing generates multiple outputs at different wavelengths corresponding to different pattern recognitions. Using wavelength multiplexing, we recognize (i) 1 pattern with 2 or 3 symbols at a 15-Gbaud rate and (ii) 2 patterns with 2 or 3 symbols at 15-Gbaud and 20-Gbaud input QPSK data. Both approaches have error-free correlation results across 1536 transmitted QPSK symbols.