Simultaneous QPSK-to- \(2\times \) BPSK Wavelength and Modulation Format Conversion in PPLN

Phase-sensitive cascaded second-harmonic generation and difference-frequency generation in a periodically poled lithium niobate waveguide allow converting two orthogonal quadratures of an optical field to different wavelengths, thus enabling simultaneous quadrature phase-shift keying-to-2× binary phase-shift keying modulation format and wavelength conversions. Static phase-sensitive extinction ratios above 20 dB are obtained for both quadratures, resulting in error-free dynamic operation with low penalty (BER 10
^-9
) at 10 Gbaud.