Phase-sensitive Optical Amplifier Research Articles

Amplifying to perfection

The demonstration of a phase-sensitive optical amplifier with a noise figure of just 1.1 dB — three times lower than that of a conventional amplifier — could help significantly extend the reach of optical communications systems.

Towards ultrasensitive optical links enabled by low-noise phase-sensitive amplifiers

Optical phase-sensitive amplifiers (PSAs) are known to be capable, in principle, of realizing noiseless amplification and improving the signal-to-noise-ratio of optical links by 3 dB compared to conventional, phase-insensitively amplified links. However, current state-of-the-art PSAs are still far from being practical, lacking e.g. significant noise performance improvement, broadband gain and modulation-format transparency. Here we demonstrate experimentally, for the first time, an optical-fiber-based non-degenerate PSA link consisting of a phase-insensitive parametric copier followed by a PSA that provides broadband amplification, signal modulation-format independence, and nearly 6-dB link noise-figure (NF) improvement over conventional, erbium-doped fiber amplifier based links. The PSA has a record-low 1.1-dB NF, and can be extended to work with multiple wavelength channels with modest system complexity. This concept can also be realized in other materials with third-order nonlinearities, and is useful in any attenuation-limited optical link.

Continuous variable (2, 3) threshold quantumsecret sharing schemes

We present two schemes to perform continuous variable (2, 3)threshold quantum secret sharing (QSS) on the quadrature amplitudesof bright light beams. Both schemes require a pair of entangledlight beams. The first scheme utilizes two phase sensitiveoptical amplifiers, whilst the second uses an electro-opticfeedforward loop for the reconstruction of the secret. Weexamine the efficacy of QSS in terms offidelity, as well as the signal transfer coefficients and theconditional variances of the reconstructed output state. Weshow that both schemes in the ideal case yield perfect secretreconstruction.

In-line optical phase-sensitive amplifier with pump light source controlled by optical phase-lock loop

This paper describes an in-line optical phase-sensitive amplifier (PSA) with a pump laser whose optical phase is locked to that of a randomly modulated signal by using an optical phase-lock loop (OPLL). The OPLL is designed with the capability of optical phase locking at an arbitrary relative phase. Experimental evaluation is presented of the OPLL employing a newly developed external cavity semiconductor ring laser with a spectrum linewidth of less than 20 kHz. Employing this pump laser with the OPLL in conjunction with a 4.4-km long nonlinear fiber Sagnac interferometer (NFSI) yields optical phase-sensitive gain of up to 11 dB. A randomly modulated signal is successfully amplified and confirmed offering a clear eye-opening.

Error-free operation of in-line phase-sensitiveamplifier

Optical phase-sensitive amplifiers (PSAs) are promising circuit elements for expanding the regenerative repeater spacing of optical transmission systems. The authors first demonstrate error-free operation of in-line PSAs with a 10 dB net gain by using an injection-locked pump with a compensation phase-locked loop.

Theoretical analysis of system limitation for AM-DD/NRZ optical transmission systems using in-line phase-sensitive amplifiers

This paper shows the theoretically derived performance of single channel, amplitude modulation/direct detection optical transmission systems using in-line optical phase-sensitive amplifiers (PSA's). The calculations take into account the degradation of the signal-to-noise power ratio (SNR) and intersymbol interference (ISI) due to the distortion of transmitted signal pulses. The SNR is analyzed by considering not only amplifier noise and fiber loss but also noise enhancement by four-wave mixing in the transmission fiber. The ISI is estimated by eye-pattern degradation of the transmitted signal numerically calculated using the nonlinear Schrodinger equation. The regenerative repeater spacing of in-line PSA systems limited by SNR and ISI can be expanded by approximately 3 to 10 times that of in-line EDFA systems, in the case of |D|/spl les/0.1 ps/mn/km dispersion fiber systems transmitting a 40-Gb/s signal.

In-line optical phase-sensitive amplifier employingpump laser injection-locked to input signal light

An in-line optical phase-sensitive amplifier with a phase-locked pump source is demonstrated. The pump source, which consists of a modelocked semiconductor ring laser, is phase-locked to the input signal light by optical injection of the signal. The randomly modulated signal pulses are successfully amplified in a Sagnac interferometer-type parametric amplifier pumped by the injection-locked laser.

Dispersion compensation with phase-sensitive optical amplifiers

Recently, we proposed a novel approach to combating the pulse-broadening effect of group-velocity dispersion (GVD) in a fiber-optic communication link (IEEE Photon. Technol. Lett., vol. 5, pp. 669-672, 1993). In our scheme, linear loss in the fiber is balanced by a chain of periodically spaced, phase-sensitive optical amplifiers. In this paper, we present a detailed analysis of pulse propagation in such a fiber line showing that, due to attenuation in the quadrature orthogonal to the amplified quadrature, it is possible for a pulse to propagate without significant broadening over lengths many times longer than the usual dispersion length of the fiber. An averaged equation for pulse evolution over distances longer than the amplifier spacing is derived. The effect of optical-phase fluctuations between the propagating pulse and the amplifiers is also considered. Since our proposed scheme does not rely on the formation of solitons in the fiber, it can be implemented in both the positive and negative GVD regions, and it does not require a minimum peak power for the pulses.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>