Abstract
A phase-sensitive four-wave mixing (FWM) scheme enabling the simultaneous conversion of the two orthogonal quadratures of an optical signal to different wavelengths is demonstrated for the first time under dynamic operation using a highly nonlinear optical fiber (HNLF) as the nonlinear medium. The scheme is first optimized with respect to the power levels and phases of the four phase-coherent pumps. The successful modulation and wavelength conversion of the two complex quadratures of a quadrature phase-shift keying (QPSK) signal to two binary phase-shift keying (BPSK) signals is then demonstrated experimentally with no power penalty at a bit-error-ratio (BER) of 10(-9) compared to direct interferometric demodulation of the QPSK signal.
Highlights
Phase-sensitive all-optical signal processing has received a significant interest in recent years, leading to several breakthroughs being reported spanning from binary phase-shift keying (BPSK) regeneration [1] to low noise amplification [2]
In order to verify the successful conversion of the two quadratures of the quadrature phase-shift keying (QPSK) signal to different wavelengths, two different sequences have been applied to the inputs of the IQ modulator, i.e. a pseudorandom binary sequences (PRBSs) of length 27 − 1 for data patterns for the in-phase (DATAI) and a PRBS of length 29 − 1 for DATAQ
A digital sampling oscilloscope was used at the receiver to save 50 bits demodulated from each idler, proving that I was carrying DATAI while DATAQ could be retrieved from Q
Summary
Phase-sensitive all-optical signal processing has received a significant interest in recent years, leading to several breakthroughs being reported spanning from binary phase-shift keying (BPSK) regeneration [1] to low noise amplification [2]. An important requirement for all-optical phase-sensitive processing is the scalability towards such modulation formats Along this direction, various schemes have been proposed and experimentally demonstrated to enable the phase regeneration of QPSK [3] and of 8-QAM [4] signals. P. Webb et al have proposed to use phase-sensitive four-wave mixing (FWM) between a signal and four phase-coherent pumps to all-optically separate the two complex quadratures of the signal by converting them to different wavelengths [5]. Webb et al have proposed to use phase-sensitive four-wave mixing (FWM) between a signal and four phase-coherent pumps to all-optically separate the two complex quadratures of the signal by converting them to different wavelengths [5] They have demonstrated experimentally such a scheme under static (i.e. employing continuous wave (CW) pumps and signal) operation using semiconductor optical amplifiers (SOAs) as nonlinear media. Our experimental demonstration was so far limited to a static characterization
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