Erbium divisions

Fig. 15. Erbium-doped fiber amplifier where x represents spHces and WDM is a wavelength division multiplexer combining the signal and pump...

Thus, Mosander s activities led to the originally two-element division into a six-element division. The cerium compounds are yellow at the higher oxidation level and colourless at the lower oxidation level, lanthanum compounds are white, didymium compounds are red, yttrium and erbium compounds are white, terbium compounds are pink. Chemists existed, of course, who disputed the existence of these elements. Unequivocal identification of elements was, however, possible in later times only. In the period in question, the main characteristics on the basis of which a substance could be qualified as a new element were separability, colour, crystal shape and reactivity. Even atomic mass determinations were largely uncertain, particularly in the group of the rare earth elements, it will be seen in the... 

Let us now leap forward in time to be able to close the matter of the division of erbium. Lecoq de Boisbaudran developed a fantastically intricate and wearisome method for the separation of gadolinite rare earth elements, consisting of 32 precipitations with ammonia and 26 subsequent precipitations with oxalate, separation of the fractions and their spectroscopic and fluorescence studies. In 1886, he came to the conclusion that holmium is not homogeneous either, it contains another element which he named dysprosium. This element was apparently accepted by the chemists of the world without the usual unbelief and debate (Lecoq de Boisbaudran 1886). 

SEMICONDUCTOR OPTICAL AMPLIFIERS have received less attention in the literature than amplifiers using optical fibers as the gain medium. Fiber amplifiers, including Erbium-doped fiber amplifiers and Raman amplifiers are currently transforming the world of optical fiber telecommunications as they become incorporated as line amplifiers in high-capacity wavelength-division multiplexed (WDM) transmission systems. However, despite the dominance of fiber amplifiers in the telecommunications marketplace, semiconductor optical amplifiers continue to show potential for application in a range of... 

Figure 17-11. Setup used to measure the net opticalgain of an erbium-doped waveguide amplifier (EDWA). Signal and pump beams are mixed in a wavelength-division-multiplexing (WDM) component and, after the amplifier, separated by another WDM component. An optical spectrum analyzer is used to detect the amplification bandwidth.

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