Novel architectural schemes for wavelength conversions in optical cross connect systems

This paper proposes simple, cost-effective schemes for wavelength conversions in optical cross-connect (OXC) systems using wavelength-fixed light sources and an optical space switch, and provides improved performance in stability and conversion range of wavelengths and channel spacing. In addition, the schemes avoid the need for the wavelength locking control that is generally needed after changing the probe beam wavelength from one wavelength to another. The technical feasibility of the proposed pre-fix scheme is investigated in terms of probe beam power through experiment of wavelength conversions based on the cross-gain modulation. The results show that the proposed wavelength conversion scheme in OXC allows a ±4 dB deviation in the probe beam power to afford a 2 dB power penalty deviation from the minimum power penalty. As long as the insertion loss deviation of an optical space switches are within ±4 dB, the proposed pre-fix scheme can be used for wavelength conversions in OXC systems for a 2 dB power penalty deviation, whereas the proposed post-fix scheme does not require an optical space switch.     

Improvement of the input power dynamic range for wavelengthconverters based on cross-gain modulation employing a probe powercontrol loop

A technique for improving the input power dynamic range of wavelength converters based on cross-gain modulation in a semiconductor optical amplifier is presented. By experimentally investigating the effect of pump and probe powers on the operating performance in terms of power penalty for a conventional wavelength converter, we show that the optimal performance depends on the ratio of pump and probe powers coupled into the semiconductor optical amplifier in a certain input power range. Based upon the experimental result, a wavelength converter with a wide dynamic range has been proposed, in which the probe power is automatically adjusted to have the power proportional to the pump power. We show that a dynamic range of >20 dB is achievable for a 2.5 Gbit/s signal at a 2-dB penalty     

Assessing Pilot-Scale Treatment Facilities with Steel Slag-Limestone Reactors to Remove Mn from Mine Drainage

Pilot-scale mine water treatment facilities were operated for over four years at the Ilwol mine, South Korea. A steel slag-limestone reactor (referred to as the slag reactor) was tested and a successive alkalinity producing system (SAPS) and a SAPS incorporating slag from a basic oxygen steelmaking furnace were compared. The SAPS decreased Mn from 23.3 to 7.4 mg L^?1 on average because the alkalinity generated led to saturation with rhodochrosite. Adding a slag reactor removed Mn down to levels of 0.002–1.8 mg L^?1 from influent Mn as high as 17.1 mg L^?1 with a residence time of 5–25 h. Mn-containing carbonates and oxides were precipitated, which was supported by the geochemical modelling and observed with scanning electron microscopy with energy dispersive spectroscopy. The increased alkalinity in the SAPS before the slag reactor helped remove Mn at a pH range of 8.0–8.3. Mn removal rates and Mn-standardized Mn removal rates in the slag reactor were 0.76 mg L^?1 h^?1 and 0.105 h^?1 in average, respectively. The passive treatment of Mn using an Fe-pretreatment and alkalinity-generation system, a slag-limestone reactor, and a wetland rather than a SAPS including slag, an oxidation-settling pond, and a wetland is suggested to consistently meet the effluent standards for Mn and pH.