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The wavelength of a narrow-band optical signal can be accurately tracked by means of an interferometer having a fixed path length difference. For example, a low-cost Fiber Bragg Grating (FBG) interrogation system which tracks the FBG reflection wavelength over time can be based on such an interferometer. Alternatively, an interferometer is operated at fixed wavelength to monitor displacement, as applied in metrology. © 2011 IEEE.

This paper deals with the intelligibility of speech coded by the STANAG 4591 standard codec, including packet loss, using synthesized speech input. Both subjective and objective assessments are used. It is shown that this codec significantly degrades intelligibility when compared to a standard narrowband filtered version of the synthesized speech. Packet loss impact is strongly dependent on the exact timing location. Furthermore it is shown that POLQA Intelligibility, a speech intelligibility prediction model, is capable of providing good intelligibility predictions for all investigated conditions. © 2017 The Author(s). Published by S. Hirzel Verlag · EAA.

Semitransparent organic solar cells employing solution-processable organic wavelength dependent reflectors of chiral nematic (cholesteric) liquid crystals are demonstrated. The cholesteric liquid crystal (CLC) reflects only in a narrow band of the solar spectrum and remains transparent for the remaining wavelengths. The reflective band is matched to the absorption spectrum of the organic solar cell such that only unabsorbed photons that can contribute to the photocurrent are reflected to pass through the active layer a second time. In this way, the efficiency of semitransparent organic solar cells can be enhanced without significant transparency losses. An efficiency increase of 6% was observed when a CLC reflector with a reflection band of 540-620 nm was used, whereas the transparency of the organic solar cells is only suppressed in the 80 nm narrow bandwidth. © 2011 American Institute of Physics.

The Atmospheric-Space Interactions Monitor (ASIM) consists of a suite of instruments to make observations of Transient Luminous Events (TLEs) and Terrestrial Gamma-ray Flashes (TGFs). The optical part of the payload is called the Multi-Spectral Modular Imaging Array (MMIA) and consists of a combination of a camera units and photometers. The Modular X- and Gamma-ray Sensor (MXGS) is a coded aperture based gamma ray imaging system. The payload is to be own on the ISS to measure the TLE's which are associated with electrical discharges in the atmosphere above 10km and commonly associated with lightning events on the Earth. Three primary types of TLE's will be studied: SPRITES, ELVES and HALOES. There will be six photometers measuring photon fluxes in specific narrow band and broad band channels between 145nm and 740nm. The six photometers will be mounted into three MMIA units each containing two photometers. Two MMIA modules will be pointed towards the Earth Limb and on MMIA to the Nadir. This paper describes the preliminary design of the photometers based on the current measurements and models of TLE characteristics.