RESUMO
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.
RESUMO
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.
RESUMO
The objective of this study was to evaluate the effect of implanting an Antigen Release Devices (ARD) into dairy cows during the lactation cycle to induce an immune response. Subsequently, the concentrations of lactoferrin in serum and milk were measured. Forty healthy adult Chinese Holstein cows were divided into two equal groups: a test group and a control group. Animals in the test group received ARD implants, whereas the control group animals were not treated. An even spread across the two groups was maintained with animal selection based on parity, the lactation days and milk yields. The concentrations of lactoferrin in the serum and milk of all forty animals were measured using an Enzyme-Linked Immunosorbent Assay (ELISA). The results show that the implantation of an ARD did not significantly increase the concentration of lactoferrin in the serum and milk throughout the whole experiment period except on two occasions. The levels of lactoferrin in the milk and serum significantly increased on day 7 and on day 11 after implantation (p<0.05). There was a strong correlation between milk lactoferrin and serum lactoferrin (r=0.564, P<0.01). Three separate ARDs were used releasing its antigen load on day 0, 14 and 28 to induce a primary, secondary and tertiary response respectively. As the significant increases in the lactoferrin levels were only observed after the first ARD release, the effects of lactoferrin appears to be associated with the early phase of the immune response, consistent with its role in the host's innate defense system.