We report the first measurement of the joint photon-number probability distribution for a two-mode quantum state created by a nondegenerate optical parametric amplifier. The measured distributions exhibit up to 1.9 dB of quantum correlation between the signal and idler photon numbers, whereas the marginal distributions are thermal as expected for parametric fluorescence.
We propose a phase-sensitive amplifier scheme that balances fiber loss and parametric gain everywhere in a fiber span. We show that, for long links, such a distributed phase-sensitive amplifier has a 3-dB lower noise figure than an ideal distributed phase-insensitive amplifier (e.g. Raman), even if simple direct detection is employed. This sets the ultimate limit for the optimum noise-nonlinearity trade-off in transmission systems.
We propose the design of an all-optical 2R regenerator capable of handling multiple wavelength-division-multiplexed channels simultaneously. It extends the known concept of off-center filtering of self-phase-modulation-broadened signal spectra. The novel feature of the proposed device is a dispersion map that strongly suppresses interchannel impairments. The map employs several sections of nonlinear fiber with high normal dispersion, separated by dispersion compensators with spectrally periodic group delay. The results of our numerical simulations indicate the feasibility of such a multichannel regenerator.
We experimentally demonstrate, for the first time to our knowledge, a phase-sensitive amplifier based on frequency nondegenerate parametric amplification in optical fiber, where the input signal-idler pair is prepared all-optically. Using two fiber-optic parametric amplifier sections separated by a fiber-based wavelength-dependent phase shifter, we observe and investigate phase-sensitive gain profile in the 1550 nm region both experimentally and theoretically. The realized scheme automatically generates gain-defining phase that is environmentally stable, making it advantageous for building phase-sensitive transmission links.
We used a spatially broadband optical parametric amplifier for image amplification. In the phasesensitive configuration of the amplifier, we observed noiseless amplification of input images. For a gain of Ӎ2.5, we measured noise-figure values of (0.2 6 0.6) and (0.4 6 0.5) dB, respectively, for two amplifiers of different lengths. These experimental values agree with theory (for an ideal noiseless amplifier the noise figure is 0 dB) and are almost 2 dB lower than the quantum limit of an ideal phaseinsensitive amplifier.
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