ABSTRACT
Fiber optical parametric amplifiers (FOPAs) operating based on four-wave mixing (FWM) are versatile devices with increasing applications in optical communication systems. In this paper, the effects of dispersion fluctuations on the performance of bandwidth, ripple, parametric gain, and saturation power of a two-pump FOPA based on four-wave and six-wave models are studied and compared. Coupled-amplitude equations representing the non-degenerate FWM process in optical fiber are solved numerically to compute the parametric gain over the communication wavelengths. The behaviors of the performance parameters are critically analyzed and compared with different types of fluctuation strengths (or amplitudes) specified by the combinations of correlation length (Lc) and fluctuation amplitude (σ). Based on the results, it was found that the flat gain bandwidth for the four-wave model remains unchanged and is insensitive to the strengths of fluctuations. The gain ripples, however, get higher as the fluctuation strengths increase. On the other hand, the flat gain bandwidths of the six-wave model are hardly identified due to the tremendous and continuous ripples within the pump wavelengths. In addition, the minimum parametric gain values for both four-wave and six-wave models reduce as the fluctuation strengths increase. Also, the lowest value of parametric gain leads to the highest saturation power and vice versa. The dispersion fluctuations affect the FWM process's efficiency and deteriorate the overall amplifier performance, particularly for the six-wave model. The numerical analysis obtained via the six-wave model is especially useful since this model closely matches with practical circumstances.
ABSTRACT
The impact of random dispersion fluctuations on the gain and saturation behavior of a one-pump fiber optical parametric amplifier (1-P FOPA) in the presence of fourth-order dispersion coefficient (ß4) is investigated. Three coupled amplitude equations with fiber losses are solved numerically for the calculation of the pump, signal, and idler. The performances of 1-P FOPA are also analyzed with variation of dispersion fluctuation amplitude (σ) and correlation length (Lc). Based on the numerical results, it is found that the gain spectra and saturation curves exhibit some differences when ß4 is considered. In comparison with the case where ß4 is ignored, the peak gain remains the same, but the 3 dB bandwidth increases when ß4 exists. Another notable difference is that the saturation power is shifted to lower or higher values, depending on the σ and Lc parameters. In general, the peak gain reduces as σ increases, and the peak gain reduction is greater for the case of shorter Lc. The numerical analysis is probably useful, especially for the case where the signal wavelength is detuned far from the pump wavelength.
ABSTRACT
In this paper, we investigate the impact of longitudinal dispersion fluctuations of the optical fiber on the gain spectrum and the saturation behavior of one-pump fiber-optical parametric amplifiers (1-P FOPAs). The gain spectra and the saturation curves of 1-P FOPAs are simulated by solving the coupled amplitude equations numerically and taking into account the dispersion fluctuations as a stochastic process with a given standard deviation and correlation length. Results show that the shape and the level of the gain spectrum and also the saturation power of 1-P FOPAs are considerably changed in the presence of dispersion fluctuations in comparison with the case when dispersion fluctuations are ignored. This feature is also totally different compared with the small-signal gain spectrum of the FOPA in the presence of dispersion fluctuations. Moreover, the value of the change in the gain and the saturation power depends strongly on the fluctuation parameters, i.e., the standard deviation and the correlation length.