'The fabrication and characterization of a Rhodamine 6G-doped polymer optical fiber amplifier have befII carried out. Two different schemes were employed to characterize the optical fiber: the stripe illuminatioII technique to study the fiber as a gain medium and another technique to study its performance as III amplifier. We observed a spectral narrowing from 42 to 7 nm when the pump energy was increased ID 6 mJ in the stripe illumination geometry. A gain of 18 dB was obtained in the amplifier configuration. The effects of pump power and dye concentration on the performance of the fiber as an amplifier were alIu studied.
The design and development of a fibre optic evanescent wave refractometer for the detection of trace amounts of paraffin oil and palm oil in coconut oil is presented. This sensor is based on a side-polished plastic optical fibre. At the sensing region, the cladding and a small portion of the core are removed and the fibre nicely polished. The sensing region is fabricated in such a manner that it sits perfectly within a bent mould. This bending of the sensing region enhances its sensitivity. The oil mixture of different mix ratios is introduced into the sensing region and we observed a sharp decrease in the output intensity. The observed variation in the intensity is found to be linear and the detection limit is 2% (by volume) paraffin oil/palm oil in coconut oil. The resolution of this refractometric sensor is of the order of 10 −3. Since coconut oil is consumed in large volumes as edible oil in south India, this fibre optic sensor finds great relevance for the detection of adulterants such as paraffin oil or palm oil which are readily miscible in coconut oil. The advantage of this type of sensor is that it is inexpensive and easy to set up. Another attraction of the side-polished fibre is that only a very small amount of analyte is needed and its response time is only 7 s.
Abstract:Optical fiber based laser induced fluorescence (LIF) measurements were carried out using Rhodamine B to analyze two different species of bacteria, a Gram-positive bacteria namely Bacillus smithii, and Vibrio alginolyticus, a Gramnegative bacteria. The fiber sensor was clearly able to distinguish between the two species of bacteria. Quenching effect of the dye Rhodamine B by Bacillus smithii was observed. The effect of dye on the samples was also studied in detail.Phase contrast image of Bacillus smithii
Multimode laser emission is observed in a polymer optical fiber doped with a mixtnre of Rhodamine 60 (Rh 60) and Uhodamine B (Rh B) dyes. Tuning oflaser emission is achieved by using the mixture of dyes due to the energy transfer occurring from donor molecule (Rh 6G) to acceptor molecule (Rh B). The dye doped poly(methyl methacrylate}based polymer optical flber is pumped axially at one end of the fiber using a 532 nrn pulsed laser beam from a Nd:YAG laser and the fluorescence emission is collected from the other end. At low pump energy levels, fluorescence emission is observed. When the energy is increased beyond a threshold value, laser emission occurs with a multimode structnre. The optical feedback for the gain medium is provided by the cylindrical surface of the optical tiber, which acts as a cavity. This fact is confirmed by the mode spacing dependence on the diameter oC the tiller.
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