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A method for the construction of a tiny in-line coupler tip is presented. An in-line coupler tip was manufactured by tapering a dual-core PCF and cleaving half of the waist region. Even and odd supermodes with different propagation constants are produced in the tapered region, which results in the inter-mode interference. The interferometric spectrum depends on both the length of the tapered region and the refractive index. Due to the thermo-optics coefficient and thermal expansion coefficient of the pure silica, the temperature of the external environment can be measured by interrogating the optical reflection spectrum. Therefore, the in-line coupler can be constructed for the measurement of temperature. The experimental results show that the temperature sensitivity of 0.024nm/°C and operation range of 1425°C are achieved. Compared with other expensive methods, the proposed method possesses wide operation range and tiny size. Thus the microstructured fibre sensor technique appears to have potential applications in industry, medicine, biology, and chemistry. [ABSTRACT FROM AUTHOR]

The multi-parameter measurement has significant meaning for biosensor to enhance their practical sensing performance. For the biological detection, simultaneous measurement of biological molecule and flow rate could improve the accuracy and sensitivity of sensors significantly. In this paper, an integrated biological analysis and flow rate sensing based on Co2+ doped tilted fiber Bragg gratings has been proposed and experimentally demonstrated for real-time the detection of the Benzo[a]pyrene molecules. A tilted fiber Bragg grating with a tilted angle of 8° was inscribed into a Co2+ doped fiber. The flow rate and Benzo[a]pyrene molecules can be measured simultaneously by interrogating the resonance wavelength of core mode and wavelength interval between the core mode and cladding mode according to the heat exchange and evanescent field of the cladding mode, respectively. Experimental results show that the real-time measurement sensitivities of 12 pm/pM and −0.13 nm/($\mu \text{L}$ /s) for the Benzo[a]pyrene detection and flow rate were achieved, respectively. Thus the technique appears to have potential applications in chemistry, medicine, and biology. [ABSTRACT FROM AUTHOR]

Edge diffraction of a beam combiner will adversely affect the field uniformity in the observation plane. In order to suppress the edge diffraction, the serrated edge design method is proposed. According to the equivalence principle, a field uniformity analysis method was proposed to compute the spatial field distribution radiated from the aperture of a beam combiner. In order to separate the direct wave from diffracted wave, the spatial field is transformed into the time- and angular-domain spectrum by inverse Fourier transform. First, the height of serrations is designed by analog of the equivalent trapezoidal amplitude taper. Then, the number of serrations was designed by the assumption of isosceles and right triangles. Finally, the shape of serrations was designed by changing the interior angle of serrations. A serrated edge design example is also proposed and analyzed. By comparing the field uniformity in spatial, time, and angular domains before and after serrating the edges, the amplitude and phase ripples decrease from 1.85 dB and 12.16° to 0.53 dB and 3.98°, respectively. The results show that the field uniformity is significantly improved. [ABSTRACT FROM PUBLISHER]