0000000000013022
AUTHOR
A. Rodriguez-cobos
High Sensitivity Refractive Index Sensor Based on Highly Overcoupled Tapered Fiber Optic Couplers
In this paper, a simple and compact fiber-optic sensor based on an overcoupled tapered fiber coupler is studied. The coupler is fabricated to be operated well beyond the initial coupling cycles, where the rapid exchange of energy between outputs ports enable the fabrication of a highly sensitive device. The suitability and sensitivity of the proposed scheme is demonstrated by measuring refractive index (RI) variations of sugar concentrations in water. The device presents a linear response in terms of power transmission or wavelength shift versus RI changes. The best achieved sensitivity is 0.442 units of normalized transmission per unit of sugar concentration, with a noise detection limit o…
Design of double-tapered fibers for tailoring the acousto-optic spectral response
A model to shape the spectral response of acousto-optic devices based on tapered fibers is reported. A double-tapered structure was designed in order to obtain a flat attenuation response with 34 nm bandwidth.
Acousto-optic interaction in biconical tapered fibers: shaping of the stopbands
The effect of a gradual reduction of the fiber diameter on the acousto-optic (AO) interaction is reported. The experimental and theoretical study of the intermodal coupling induced by a flexural acoustic wave in a biconical tapered fiber shows that it is possible to shape the transmission spectrum, for example, substantially broadening the bandwidth of the resonant couplings. The geometry of the taper transitions can be regarded as an extra degree of freedom to design the AO devices. Optical bandwidths above 45 nm are reported in a tapered fiber with a gradual reduction of the fiber down to 70 μm diameter. The effect of including long taper transition is also reported in a double-tapered st…
Tunable narrowband fiber laser with feedback based on whispering gallery mode resonances of a cylindrical microresonator.
Narrowband filtering based on whispering gallery modes of a slightly tapered cylindrical optical microresonator was used to implement a tunable narrowband erbium-doped fiber laser. The laser can be set to emit a single longitudinal cavity mode (single frequency), although the laser cavity is a few meters long. In the single-frequency regime the laser can emit a maximum power of 0.380 mW with a linewidth <35 kHz and a signal-to-noise ratio exceeding 50 dB. Tunability is achieved by sliding the excitation point along the microcylinder. A tuning range of 1.16 nm is demonstrated.
Experimental Investigation of Fused Biconical Fiber Couplers for Measuring Refractive Index Changes in Aqueous Solutions
A detailed experimental study of a simple and compact fiber optic sensor based on a fused biconical fiber coupler is presented, in which the sensitivity is improved by operating the coupler beyond the first coupling cycle. The sensor is demonstrated to perform high sensitivity measurements of refractive index changes by means of variation of sugar concentration in water. The device is operated to achieve a linear transmission response, allowing a linear relation between the sugar concentration and the output signal. The initial sensitivity was measured as 0.03 units of normalized transmission per unit of sugar concentration (g/100 mL), with a noise detection limit of a sugar concentration o…