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Zusammenfasung: Bei der infektiösen Spondylitis handelt es sich in der Regel um eine Osteomyelitis von 2 benachbarten Wirbelkörpern unter Beteiligung der Zwischenwirbelscheibe (Spondylodiszitis). Am häufigsten ist die Lendenwirbelsäule betroffen, gefolgt von der Brustwirbelsäule. Die Symptome der infektiösen Spondylitis sind unspezifisch, was nicht selten zu einer Verzögerung von einigen Wochen bis zur Diagnosestellung führt. Die infektiöse Spondylitis kann durch eine Vielzahl von Erregern bedingt sein, die überwiegend auf hämatogenem Weg die Wirbelsäule erreichen. Der häufigste Erreger ist Staphyloccocus aureus. Die Spondylitis ist zudem die häufigste skelettale Manifestation der Tuberkulose. Wie bei anderen Formen der Osteomyelitis ist die Kenntnis des Erregers für die Wahl einer adäquaten Therapie entscheidend, weshalb eine mikrobiologische Diagnose auf jeden Fall angestrebt werden sollte. Die Mehrheit der Fälle kann konservativ mit antibiotischer Therapie geheilt werden.

We have measured the nonlinear refractive index near half-bandgap (Eg2) in ZnS and ZnSe by self-phase modulation experiments. The ratio of the nonlinear phase shift and the total optical absorption losses is critically dependent on the detuning from Eg2. Efficient quadrature squeezing was obtained at a centre wavelength of 780 nm in ZnS and at 960 nm in ZnSe. The scheme we employed can generally be applied to semiconductors, and opens the way for squeezed light generation over a wide range of wavelengths.

We present the principle of optical frequency modulation via the Doppler effect obtained by rapidly stretching an optical fiber and thus modifying the optical path of the light propagating in the fiber. This procedure creates a pure frequency shift, with no degradation of the spectrum. Moreover, the effect is wavelength independent and can therefore be applied to any type of light source. We show an experimental realization in which a frequency excursion of ?100 MHz was obtained with a bobbin vibrating at 180??Hz.

The polarization properties of concatenations of trunks of birefringent fibers and elements with polarization-dependent losses are analyzed. We show both theoretically and experimentally that the concatenation can have zero differential group delay over a whole range of wavelengths but that a pulse propagating down the concatenation can still experience significant pulse spreading. In this example the two main methods used for characterizing polarization mode dispersion in optical fiber systems, i.e., Jones matrix eigenanalysis and the interferometric method, give different results. This counterintuitive example underlines the need for a careful assessment of the basic concepts related to polarization effects in the presence of polarization-dependent losses.

Quantum cryptography over 23 km of installed telecommunications fibre using a novel interferometer with Faraday mirrors is presented. The interferometer needs no alignment nor polarisation control and features 99.8% fringe visibility. A secret key of 20 kbit length with an error rate of 1.35% for 0.1 photon per pulse was produced.

A combination of polarization-mode dispersion and polarization-dependent losses in optical fibers may lead to anomalous pulse spreading. We both calculate this effect and confirm its existence by an experimental demonstration.