Amplification of broadband noise pumped by two lasers in optical fibers

A theoretical and experimental investigation of catastrophic amplification of broadband noise in optical fibers near the zero-dispersion frequency (v(0)) pumped by two lasers with frequencies that are symmetrically tuned relative to v(0) is presented. The effect is due to a four-wave mixing (FWM) process, phase matched up to third-order dispersion, between the spectral components of noise and the lasers. We observed a FWM gain of 16 dB (10-dB net gain) over a 22-nm bandwidth (limited by fourth-order dispersion) for 18-dBm power lasers at +/-1 THz (8 nm) from v(0) in a 25-km-long dispersion-shifted fiber. A simple analytical model is proposed that will permit us to investigate this effect numerically in amplified links with concatenated amplifiers and consider random fluctuations of v(0) along the fiber. (C) 2001 Optical Society of America.18101428143

Highly efficient generation of broadband cascaded four-wave mixing products

We report and investigate on a highly efficient technique to generate broadband cascaded four-wave mixing (FWM) products. It consists of launching two strong pump waves near the zero-dispersion wavelength of very short (of order of few meters) optical fibers. Simulations based on split step fourier method (SSFM) and experimental data demonstrate the efficiency of this approach. Multiple FWM products have been investigated by using conventional fibers and ultra-flattened dispersion photonic crystal fibers. Measured results present bandwidths of 300 nm with up to 118 FWM products. We have also demonstrated a flat bandwidth of 110 nm covering the C and L bands, with a small variation of only 1.2 dB between the powers of FWM products, achieved by using highly nonlinear fibers (HNLFs). The use of dispersion tailored photonic crystal fibers has been shown interesting for improving the multiple FWM efficiency and reducing the separation between the pump wavelengths. (c) 2008 Optical Society of America.1642816282

Solutions for first- and second-order four-wave mixing cross talk in one-pump fiber optical parametric amplifiers

We show that the set of two coupled differential equations governing a four-wave mixing (FWM) component and its associated idler in a one-pump fiber optical parametric amplifier are the same as for standard parametric amplification, but with additional source terms arising from FWM between already-calculated waves. We show how to solve this new set of equations in general: this involves multiplication by an exponential matrix and its inverse, and integration. Hence it is in principle possible to write the exact expressions for the cross-talk fields, in terms of a large number of exponentials. The results show that the power of the first- and second-order cross-talk terms scales, respectively, like the first and second power of the signal power. In the case of two input signals, the powers of the cross-talk terms are independent of the phases of the signals, hence phase control cannot be used for reducing cross talk. In a particular case, cross talk scales like the inverse of pump power, which confirms a general trend noted in numerical simulations, and experiments. (c) 2008 Optical Society of America

Modulation instability effects on three-channel optically multiplexed communication systems

Four-wave mixing dynamics an analyzed on a three-channel optically multiplexed communication system. In the anomalous propagation regime, where modulation instability effects are much stronger, energy interchange among signal channels tends to favor the central channel as opposed to the normal propagation regime where the central channel is depleted. These results are explained both in terms of the phase-matched growth of generated spectral sidebands and the three-channel modulation instability gain spectrum. (C) 1999 Published by Elsevier Science B.V. All rights reserved.17141699536

Crosstalk in double-pumped fiber optic parametric amplifiers for wavelength division multiplexing systems

We study experimentally inter-channel crosstalk in double-pumped fiber optic parametric amplifiers constructed with conventional dispersion shifted fibers (DSFs) having different lengths (L-A = 13.8, L-B = 6.8, L-C = 4.3, and L-D = 0.8 km). For long fibers (L-A and L-B), eye diagram measurements in a 5-channel (100 GHz spacing) system show that in order to have negligible crosstalk, the output signal power per channel, P-s, should be limited to P-s < 0 dBm. By decreasing the fiber length (to L-C) it is possible to increase the output signal power and/or the number of signals while keeping the crosstalk on negligible levels. This trend was further confirmed by using a very short DSF (L-D = 0.8 km). Finally, we experimentally demonstrate that a general trend in 2P-FOPAs is that spurious FWM increases with the number of signal channels up to a given number of channels when a saturation regime is reached. This saturation of the generation of spurious tones occurs when the bandwidth occupied by the signals exceeds similar to 4-5 nm. (c) 2005 Elsevier B.V. All rights reserved.25919410

Double-pumped fiber optical parametric amplifier with flat gain over 47-nm bandwidth using a conventional dispersion-shifted fiber

We investigate the performance of conventional. dispersion-shifted fibers (DSFs). as nonlinear medium in double-pumped fiber, optical parametric amplifiers (2P-FOPAs). We report on high gain (37 dB) with low ripple (+/- 1.5 dB) over a 47-mn bandwidth using these fibers. We show that the 2P-FOPA average gain, and the gain. uniformity are limited. by longitudinal variations of the zero dispersion wavelength and by polarization-Mode dispersion. We demonstrate that 2P-FOPAs constructed with DSFs exhibit negligible crosstalk even for high gains (40 dB) and-large output signal powers (12.5 dBm) in a ten-channel system.1791842184

Experimental and numerical investigation of the SBS-threshold increase in an optical fiber by applying strain distributions

We study, experimentally and numerically, the increase of the stimulated Brillouin scattering (SBS) threshold in dispersion-shifted fibers (DSFs) by applying three different tensile-strain distributions. The best results are obtained with a 40-step stair-ramp distribution, for which we demonstrate a 8-dB SBS threshold increase in a 580-m DSF. The Brillouin frequency is observed to shift as a function of the strain at a rate of 0.464 GHz/%. We discuss the potentials and drawbacks of this technique for application in nonlinear devices.23113808381

Spurious four-wave mixing in two-pump fiber-optic parametric amplifiers

We present an experimental study on four-wave mixing (FWM) between two signals within a two-pump fiber-optical parametric amplifier (2P-FOPA). We demonstrate that the intensity of FWM spurious tones depend strongly on the signal power and length of the nonlinear medium and present two regimes as a function of the pumps' power. We also compare the amounts of FWM as a function of channel spacing in the 2P-FOPA with or without pumps and show that the presence of parametric gain enhances FWM over a broad spectral range.16243443

Narrow linewidth fibre-optical wavelength converter with strain suppression of SBS

A broadband and efficient fibre-optical wavelength converter pumped by a narrow linewidth laser is presented. The stimulated Brillouin scattering is suppressed by applying strain distributions along the fibre, thus eliminating unnecessary broadening of the converted signal.40191213121

Performance of a two-pump fiber optical parametric amplifier in a 10 Gb/s x 64 channel dense wavelength division multiplexing system

We analyze the performance of two-pump fiber optical parametric amplifiers (2P-FOPA) as preamplifiers for wavelength division multiplexing transmission systems. We simulate the propagation of 10 Gb/s x 64 channels over 120 km of non-zero dispersion shifted fiber and amplify them by a 2P-FOPA before detection. We demonstrate that a careful design-of the FOPA parameters leads to high system performance, comparable than those obtained with erbium and Raman amplifiers. For signal powers of -32.5 dBm at the FOPA input we observe clear eye openings for all the amplified signal lasers, with an average gain of 22 dB and low ripple (6 dB) over 25 nm bandwidth. We study the influence of fluctuations of the zero dispersion wavelength of the FOPA fiber. These fluctuations in realistic fibers tend to reduce the average gain and degrade the noise figure and spectral gain ripple. (C) 2003 Elsevier Science B.V. All rights reserved.2184179430331