Group velocity manipulation in active fibers using mutually modulated cross-gain modulation: from ultraslow to superluminal propagation

We propose and experimentally demonstrate the propagation of slow/fast light in an erbium-doped fiber (EDF) using mutually modulated cross-gain modulation. The group velocity of the light signal can be manipulated by the effect of gain cross-saturation modulation by a saturating light at an arbitrary wavelength in the gain bandwidth of the EDF. The ultraslow propagation with a small group velocity of 5.6 × 10⁻³c (c is the light speed in free space) and superluminal propagation with a negative group velocity of -1.1 × 10⁻³c has been observed under different modulation phases.

Amplitude-equalized high-order arbitrary numerator rational harmonic mode-locked pulse generation in fiber-ring lasers using nonlinear polarization rotation

We report the amplitude-equalized high order arbitrary numerator rational harmonic mode-locked (RHMLed) pulse generations based on the technique of nonlinear polarization rotation in the fiber-ring laser. The numerator effect on the amplitude uniformity of RHMLed pulse train is first investigated. It is demonstrated that the high order RHMLed pulse train with uniform amplitude can be achieved by choosing a proper numerator. The pulse amplitude equalization in up to the 10th order RHMLed pulse train is observed when the numerator is equal to 3 instead of 1. It is important that the technique may be useful to generate the high-speed pulse trains with uniform amplitude by using the high order RHMLing technique.

[The role of Anopheles anthropophagus in malaria transmission in in Xinyang City of Henan Province]

OBJECTIVE

To study the role of Anopheles anthropophagus in malaria transmission and transmission threshold so as to provide basis for vector surveillance and malaria control strategy.

METHODS

Parasitological and entomological methods were used in the investigation at 5 villages of Xinyang City, Henan Province.

RESULTS

From July to August, 1999, 74 febrile cases (10.9% of the total population) were examined. Among them 50 were infected, the incidence in the population of surveyed spots was 7.4%. Active detection was made in another randomly selected two villages and found that the parasite rate in the inhabitants was 2.0%, and the positive rate of IFA was 8.4%. Only vivax malaria was detected. An. anthropophagus and An. sinensis were collected, with An. anthropophagus as the predominant one in human dwellings. The estimated man-biting rate and the human blood index were 4.9388 and 0.7858 respectively. The vectorial capacity of An. anthropophagus was 5.5296. The critical man-biting rate of An. anthropophagus was 0.2407 as calculated by the formula (ma = -rlnP/abPh) according to Macdonald's model. The local man-biting rate was 20 times higher than that of the critical man-biting rate.

CONCLUSION

The results demonstrated that An. anthropophagus is the principal vector in malaria transmission in the area. The findings imply that the critical man-biting rate is of practicable importance in vector surveillance.