We show that the impact of PMD on the gain spectrum of fiber OPAs can be reduced by imposing twists along the fiber axis. Alternating twists are used in order to cancel the induced circular birefringence.

The amplification of wavelength division multiplexed (WDM) data in fiber-optical parametric amplifiers give rise to cross-gain saturation and four-wave mixing crosstalk. This crosstalk affects the data quality, especially at higher input powers. The statistics in this regime are nontrivial to obtain and we present, for the first time, a model based on a combination of theory and numerics that gives accurate statistics at a highly reduced computational cost. This model is obtained from an exact solution of WDM data being amplified in the strictly nonlinear regime which is derived in this paper. Using this model, predictions of the bit-error rate (BER) can be obtained even at very low rates impossible to reach by numerical methods alone. We show that there exists no trivial relationship between the BER and the commonly used quality measure, the Q-value. We also study how different amplifier parameters affect the statistics and suggest design rules to reduce channel crosstalk.

Amplification of wavelength-division multiplexed data in parametric devices introduces channel cross-talk. We develop a model to obtain correct statistics and predict different properties such as how bit-errors are introduced and their dependence on fiber properties.

The noise figure of a fiber optical parametric amplifier is measured at 300 and 77 K. Record low-noise, quantum-limited amplification is achieved at the Stokes frequencies.

The noise figure (NF) of a fiber-optical parametric amplifier, driven by pumps with orthogonal polarizations, is quantified experimentally. It is shown that this amplifier has a signal-polarization-dependent gain, with a corresponding polarization-dependent NF. The polarization dependence of the NF is particularly large when higher input-signal powers are amplified, in which case pump-induced noise dominates. At lower input-signal powers, the NF is less dependent on the input polarization, but increases closer to the lower-frequency pump

The noise figure (NF) of a dual-pumped parametric amplifier with copolarized pumps is quantified for the first time to our knowledge. It is shown that the NF is increased by the noise on the pump sources, in agreement with theory, and that it gives a uniform NF degradation due to a uniform gain spectrum. The magnitude of the NF degradation increases with increasing input-signal power. Various aspects of the NF are studied, such as the effects of three idlers generated by the four-sideband interaction, and Raman-induced losses and excess noise caused by the population of thermal phonons. It is shown that the use of unequal pump powers only affects the low-power NF to a minimal degree. Also, the gain dependence of the NF is studied, as are the wavelength and signal power dependences of the NF. It is shown that at high gain, the NF saturates even when pump noise is an issue. Also, unequal pump powers with fixed gain have a minor impact on the noise performance of the amplifier. Theory and experiments agree well with each other.

In this paper, we show both theoretically and experimentally that the probability density function of the intensity of an amplified signal by parametric amplifiers subject to a pump with excess noise is highly asymmetric. This is due to the nonlinear relationship between the optical pump power and the parametric gain. Because of this, the relationship between the noise figure (NF) and the bit error rate (BER) is modified, compared with that predicted by the chi 2 theory, which is an effect that is notable at large NFs and low BERs. The difference in predicted BER can be of several orders of magnitudes between the correct theory and the chi 2 approximation in single-stage parametric amplifiers. We also show that in the limit of many cascaded parametric amplifiers, the statistics of the noise of an amplified optical signal approaches chi 2 . Furthermore, the BER of a parametric amplifier is generally lower compared with erbium-doped fiber amplifiers for the same NF values if we assume quantum-limited amplification

Pump phase-modulation is often needed to suppress stimulated Brillouin scattering in fiber-optical parametric amplifiers. We show that while this causes a gain variation with a corresponding Q-value penalty, the actual bit-error-rate degradation is not always significant. The findings are supported by experimental studies

We measure, for the first time, the wavelength resolved electrical noise figure (NF) of a fiber-optical parametric amplifier and find excellent agreement with theoretical predictions. We furthermore measure the NF in the exponential gain regime at high gain and quantify the gain dependence of the NF as well as its spectral dependence

We have derived theory predicting the impact phase modulation has on dual-pumped parametric amplifiers which includes also the effect of pump power fluctuations. The theory shows that gain perturbations due to perturbations in the pump frequencies can be significantly reduced by operating the two pumps out of phase. Furthermore, filtering the phase-modulated pumps can introduce detrimental gain variations and we propose the use of "flat-top" filter characteristics in order to reduce the filter bandwidths around the pump without causing too much gain-variations on the amplified signal. We also investigate the effect of detuned optical filters.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text P. Kylemark, M. Karlsson, and P. A. Andrekson, "Properties of pump-induced noise in fiber optic parametric amplifiers," in Optical Amplifiers and Their Applications/Coherent Optical Technologies and Applications, OSA Technical Digest Series(CD) (Optica Publishing Group, 2006), paper OWA3. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

A semi-analytical theory for the gain saturation of parametric amplifiers is presented. The theory is both simple and intuitive, it is compared with experiments on a parametric amplifier, and a very good agreement is found. Furthermore, using theoretical results, a method to obtain saturation characteristics for parametric amplifiers that have features not easily reproduced by theory is presented. The obtained method finds saturation characteristics in a few steps, providing that the gain studied is above 15 dB, where the approximations upon which our simple expression is based are strictly valid. An exact solution of the gain saturation when the pump power is totally converted is also presented and compared with the simplified expression using previously obtained theoretical results

We derive equations for penalties introduced by the combined effects of timing-jitter and amplitude noise in a transmission link. We then apply the results on a DM-soliton system operating at 40 Gbit/s, where Gordon–Haus-jitter is important at large distances. We predict, using the theory, the maximum transmission distance for various systems. Finally, we compare the theory with numerical simulations and find a good agreement between them.

The noise figure (NF) properties of an undepleted and lossless dual-pump fiber-optic parametric amplifier (FOPA) are theoretically and numerically investigated. The theoretical study takes into account the noise characteristics of the two pump waves that are considered to have parallel polarization states for gain maximization. It is shown that noisy pump waves degrade the amplifier's NF, especially when the amplifier is operating at high gain values and when the input signal is high. The theoretical observations are validated by Monte Carlo numerical simulations, And the agreement between them is excellent. Finally, a comparative study concerning the. noise characteristics of dual-pump and single-pump FOPAs is performed.

A comparison between the noise characteristics of single-pump and dual-pump fiber optical parametric amplifiers is theoretically carried out in terms of the noise figure, accounting for the amplified quantum noise and the excess pump noise. (2 pages)