Peter Kraemmer

Highly sensitive micro-mechanical fiber Bragg grating acceleration sensor combined with a new multiplexable interrogation principle

The paper describes a micro mechanical Bragg grating acceleration sensor with enhanced sensitivity by force amplification. A new multiplexable and affordable interrogation scheme that uses two overlapping Bragg gratings within the sensor will be demonstrated.

Low-cost optical temperature and strain sensing networks using in-line fiber gratings

A cost-effectively designed polychromator using holographic grating as spectral dispersive element and CCD line array as detector is applied to the multiplexing of a many-element fiber grating sensor network for measuring temperature and stationary strain. The influence of intensity and polarization fluctuations in the superluminescent diode as a broadband light source, and in the fiber transmission lines as well have been minimized by reducing parasitic reflections and introducing depolarizing elements. Other error sources of the sensor read-out stability have been reduced by appropriate peak fitting procedures of the CCD pixel intensity distribution and by the consumption of mechanically stable sensor heads for temperature and strain sensing with low cross sensitivity. A special mounting technique allowing compensation of thermally induced Bragg wavelength shifts is used for obtaining a wavelength reference in the polychromator. Thus, stability of wavelength readout is only noise-limited with a rms value of about 0.2 pm and yields a resolution and stability for measurement of temperature

Biosensors for unattended, cost-effective and continuous monitoring of environmental pollution: Automated Water Analyser Computer Supported System (AWACSS) and River Analyser (RIANA)

This work describes our recent progress and achievements in the field of fully automated biosensors (Automated Water Analyser Computer Supported System (AWACSS) and River Analyser (RIANA)) for unattended, cost-effective and continuous monitoring of environmental pollution. We report on ultra-sensitive immunoassays for the hormones progesterone, testosterone and estrone and the pesticides propanil and isoproturon as examples of the outstanding progress made on biosensors in the field of environmental monitoring and water analysis. Most of the bio-active organic pollutants (estrone, progesterone, propanil and isoproturon) were detected at levels as low as 1.0 pg mL−1 or even below. In fact, the reported limits of detection (LOD) were between 0.2 and 6.0 pg mL−1. For the first time, commercially available derivatives and antibodies were incorporated into immunoassays (progesterone and testosterone) for fully automated biosensors. To verify the assay performance for quantifying testosterone, progesterone, and isoproturon in real-world samples using our immunosensors, we spiked river and drinking water at six different levels from 0.9 pg mL−1 to 90 ng mL−1. Nearly all recovery rates could be obtained between 70 and 120% as the AOAC International recommends it chiefly for water analysis.

Imaging in scattering media using the phase of modulated light sources

Intensity transmission measurements of biological tissue with light in the wavelength range from 600 nm to 1000 nm yields limited resolution due to strong scattering. The resolution can be improved using time gated methods. These measurements are technically complicated and require a long detection time. A different approach is the measurement of the phase shift of transmitted light using a radio frequency modulated light source. We have investigated the influence of the modulation frequency on the intensity distribution and on the phase shift both theoretically and experimentally. Further the dependence on the scattering and absorption coefficients of the illuminated medium has been examined. The theoretical calculations have been carried out using analytical and numerical solutions of the diffusion equation. Results are given for the modulation frequency range from 60 MHz to 500 MHz. They show that the modulation frequency has an effect mainly on the phase shift and only to a small degree on the intensity distribution.

Distributed Optical Flow Sensing Using a Novel Fiber Bragg Grating Sensor

Conventional heated wire anemometry in combination with distributed fiber optical temperature sensors based on fiber Bragg gratings offer the possibility of distributed flow measurements.

Integrated optical immunofluorescence multisensor for river pollution

A 32-analyte integrated optical immunofluorescence multisensor system has been realized and tested for the first time. The sensor system is based upon bio/immuno-chemistry at the waveguide surface and fluoroimmunoassay in the evanescent fields of the optcal waeguides, to enable rapid, simultaneous and high-sensitivity fluorescence detection of up to 32 pollutants in water, and automatic regeneration for immediate reuse. The system has been demonstrated for estrone and a detection limit of 13 ng/L has been achieved.

Multiplexed temperature measurement for power generators

This paper reports on the first realization of embedding fiber optical Bragg grating temperature sensors inside the stator bars of a 120 MVA air cooled power generator. Furthermore first measurements of the conductor temperature inside the bushings have been carried out during a generator prototype test run.