Wide multiwavelength Brillouin-Raman fiber laser assisted by an arc-shaped fiber attenuator.

A wide bandwidth, single-spacing half-open-cavity multiwavelength Brillouin-Raman fiber laser (MWBRFL) is demonstrated. The laser cavity contains a fiber loop mirror (FLM) with an arc-shaped optical fiber attenuator that is used to control the mirror reflectivity, thereby suppressing gain competition from longitudinal cavity modes. A tuning range of 45 nm with 632 lines at Raman and 1525 nm Brillouin pump powers of 1.

Wide-uniform triple Brillouin frequency spacing multi-wavelength fiber laser assisted by a distributed Raman amplifier.

In this paper, we demonstrate a wide-uniform and hybrid multi-wavelength fiber laser source with triple Brillouin-shift wavelength spacing. The hybrid gains include the combination of erbium-ytterbium-doped fiber and distributed Raman amplifiers. For optimum performances, the Brillouin pump wavelength is set at 1532 nm with power at -20 dBm, erbium-ytterbium-doped fiber amplifier at 950 mW and Raman pump power at 900 mW.

Enhanced flatness of 20 GHz channel spacing multiwavelength Brillouin-Raman fiber laser with sub-millimeter air gap.

We discover the technique of controlling the flatness in signal amplitude of a multiwavelength Brillouin-Raman fiber laser by employing an air-gap outside of the cavity. The structure that is adjustable within sub-millimeter length behaves as flexible optical feedback that provides modifiable portions of multiple Fresnel reflectivities. This is the main benchmark that allows the efficient management of gain competition between self-lasing modes and Brillouin Stokes waves that is vital for self-flattening initiation.

Independent determinants of periodontitis in Yemeni adults: A case-control study.

Objectives: The relative importance of risk factors of periodontitis varies from one population to another. In this study, we sought to identify independent risk factors of periodontitis in a Yemeni population.

Methods: One hundred and fifty periodontitis cases and 150 healthy controls, all Yemeni adults 30-60 years old, were recruited.

Prevalence of Iron Deficiency Anemia among University Students in Hodeida Province, Yemen.

Background: Iron deficiency anemia (IDA) is one of the most common types of nutritional anemia in the worldwide and considered a major public health problem in developing countries especially in Yemen. Therefore, this cross-sectional study was conducted to determine the prevalence and risk factors of IDA among apparently healthy Yemeni students at Hodeida University.

Method: Five hundred blood samples (326 males and 174 females) were collected randomly from medical students at Hodeida University.