Optical fibre coupler

Interference Filters Optical Fibre Optical Coupler... 

The set-up used consists of a tungsten light source (20 W, 12 V), optical Y-fibre couplers (PMAA, 1 mm core diameter, microparts, Dortmund, Germany) and a diode array spectrometer (MMS, Zeiss, Jena, Germany). Interference spectra were recorded from 450-700 nm. 

Figure 9.14. Brillouin spectrometer using fibre optics to increase the signal-to-noise ratio. (1) Light source consisting of a master laser (1a) a slave with matched frequency (1b) and control unit (1c) for sensitive stabilization of the difference frequency Sv. (2) Signal splitter. (3) Fibre coupler. (4) Polarizer. (5) Chopper. (6) Lens. (7) Cuvette placed on a goniometer. (8) Termination. (9) Slit. (10) Broad-band (10 GHz) APD. (11) Photodiode with a smaller bandwidth (1 GHz). (12) Spectrum analyser (10 GHz) for controlling the intermediate frequency Sv. (13) Spectrum analyser (1 GHz) for the measurement of the half-power bandwidth, Av, of the Brillouin peak. (14) Amplifier system. (15) Process control computer. (Reproduced with permission of Elsevier, Ref [96].)...

Spectroscopic techniques are popular as a means of detection on chips. Examples include the determination of flavins and DNA by fluorescence. Spectrophotometric techniques are often used for biological samples . Mass spectrometry has also been used. Benetton et al. coupled electrospray ionisation MS to a chip while Sillon et al. developed a low cost mass spectrometer which incorporated the ionisation chamber, filter and detector on the chip. A fibre optic coupler has been developed as a detector. The dual optical fibre configuration (one transmitting, one receiving, (Eigure 10.5)) in the chip forms the microchannel as well as the detector itself and measures refractive index changes but can also be used to measure absorbance . 

The benefits of optical fibres include their inmiunity to EMI. Optical sensors and couplers are often encapsulated in PC housings. Electronic controllers and their associated sensors are to be found in areas where electromechanical controllers formerly held sway as in white goods, for example, washing machines. 

We now describe an instrument using monomode fibre and an integrated fibre coupler, that therefore has no breaks in the transmission path due to the insertion of bulk optical components. Back reflection of a portion of the incident beam from the output port means that we detect a mixture of scattered light and a "reference beam", the so-called heterodyne detection scheme in which the first order correlation coefficient g( )(T) is measured directly. The signal is detected by a photomultiplier and processed by a multibit correlator. The fibre end is available to use directly as a probe into a dispersion or may be,mounted in a thermostatted flow cell. Results will be presented showing the performance on model systems as a function of concentration. The use of such an instrument for remote sensing in a variety of applications will be discussed. 

Optical couplers are used to split, combine or distribute light beams to and from optical fibres. The material of the coupler must have a coefficient of thermal expansion close to that of the optical fibres, excellent dimensional stability at elevated temperatures, high modulus, and extremely low mould shrinkage to allow very narrow tolerances. A special grade of glass-fibre-filled LCP has been developed for this application. " ... 

Stadnik, D. and Dybko, A. (2003) Fibre optic coupler as a detector for microfluidic applications. Analyst, 128, 523-526. 

The CTE is unique in being extremely low, and can be tailored to meet specific component requirements by careful selection of fillers and additives, and through part design, mould design and gate location. This characteristic has already been exploited commercially in couplers and connectors for fibre optics. 

Fibre-optics Strength members, couplers, connectors... 

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