Dmitry Levandovsky

Amplitude squeezing of light by means of a phase-sensitive fiber parametric amplifier.

We experimentally demonstrate generation of bright sub-Poissonian light by means of parametric deamplification in a phase-sensitive fiber amplifier that is based on a balanced nonlinear Sagnac interferometer. On direct detection, the photocurrent noise falls below the shot-noise limit by (0.6 +/- 0.2) dB (1.4 dB when corrected for detection losses). To observe the noise reduction we employed a scheme that used two orthogonally polarized pulses to cancel the noise that arises from the predominantly polarized guided-acoustic-wave Brillouin scattering in the fiber. We also present a simplified semiclassical theory of quantum-noise suppression by this amplifier, which is found to be in good agreement with the experimental results.

Wavelength routing based on physical impairments

A set of guidelines for routing wavelengths in switched optical networks that is based on physical constraints is presented. Impact on signaling protocols is also discussed. One may still choose to break down the automatically switched optical network (ASON) into multiple sub-networks, but the choice will now be based on administrative or business considerations rather than physical constraints. Hence, we shall concentrate on the methods that may be employed in estimating the quality of service for a transparent wavelength connection through such an ASON.

Perturbation theory of quantum solitons:?continuum evolution and optimum squeezing by spectral filtering

We study the quantum-noise properties of spectrally filtered solitons in optical fibers. Perturbation theory, including a quantum description of the continuum, is used to derive a complete analytical expression for the second-order correlator of the amplitude quadrature. This correlator is subsequently used to optimize the frequency response of the filter numerically in order to achieve the minimum photon-number noise. For propagation distances up to three soliton periods, the length at which the best noise reduction occurs, a square filter is found to be approximately optimum. For longer distances, more-complicated filter shapes are predicted for the best noise reduction.

Soliton squeezing in a Mach-Zehnder fiber interferometer

A scheme for generating amplitude squeezed light by means of soliton self-phase modulation is experimentally demonstrated. By injecting 180-fs pulses into an equivalent Mach-Zehnder fiber interferometer, a maximum noise reduction of

Soliton squeezing in a highly transmissive nonlinear optical loop mirror

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Photon statistics of single-mode zeros and ones from an erbium-doped fiber amplifier measured by means of homodyne tomography

dB is obtained

Photon statistics of a single mode of amplified spontaneous emission noise in an erbium-doped fiber amplifier

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Optimum noise filtering of quantum solitons

dB when corrected for losses). The dependence of noise reduction on the interferometer splitting ratio and fiber length is studied in detail.

Near-noiseless amplification of light by a phase-sensitive fibre amplifier

A perturbation approach is used to study the quantum noise of optical solitons in an asymmetric fiber Sagnac interferometer (a highly transmissive nonlinear optical loop mirror). Analytical expressions for the three second-order quadrature correlators are derived and used to predict the amount of detectable amplitude squeezing along with the optimum power-splitting ratio of the Sagnac interferometer. We find that it is the number-phase correlation owing to the Kerr nonlinearity that is primarily responsible for the observable noise reduction. The group-velocity dispersion affecting the field in the nonsoliton arm of the fiber interferometer is shown to limit the minimum achievable Fano factor.A perturbation approach is used to study the quantum noise of optical solitons in an asymmetric fiber Sagnac interferometer (a highly transmissive nonlinear optical loop mirror). Analytical expressions for the three second-order quadrature correlators are derived and used to predict the amount of detectable amplitude squeezing along with the optimum power-splitting ratio of the Sagnac interferometer. We find that it is the number-phase correlation owing to the Kerr nonlinearity that is primarily responsible for the observable noise reduction. The group-velocity dispersion affecting the field in the nonsoliton arm of the fiber interferometer is shown to limit the minimum achievable Fano factor.

Soliton squeezing in asymmetric and symmetric fiber Mach-Zehnder nonlinear interferometers

We report measurement of the photon-number distributions of zeros and ones that emerge from an erbium-doped fiber amplifier (EDFA) in an on-off modulated communication system. Single-mode single-photon resolution was achieved by employing the method of optical homodyne tomography. The measured distributions agree with the quantum predictions of a Bose-Einstein distribution for the zeros and a Laguerre (noncentral negative binomial) distribution for the ones over a dynamic range up to 40 dB. The resulting noise figure of the amplifier compares well to that measured by an optical spectrum analyzer.