Two-core transversally chirped microstructured optical fiber refractive index sensor

Abstract

We present a sensing architecture consisting of a two-core chirped microstructured optical fiber (MOF) for refractive index sensing of fluids. We show that by introducing a chirp in the hole size, the MOF can be a structure with decoupled cores, forming a Mach-Zehnder interferometer in which the analyte directly modulates the device transmittance by its differential influence on the effective refractive index of each core mode. We show that by filling all fiber holes with analyte, the sensing structure achieves high sensitivity (transmittance changes of 300 per RIU at 1.42) and has the potential for use over a wide range of analyte refractive index.

Some refractometric features of dual-core chirped microstructured optical fibers

“…For a small d max , the effective RI difference increases exponentially with n a as observed in Ref. 8. However, if d max is increased, it is observed that the effective RI difference has a completely different behavior and now decreases with n a (under current conditions we found that depends quadratically).…”

“…8 By using this novel concept, we designed a label-free biosensor by immobilization of an antigen sensor layer onto the walls of the air holes of rings surrounding one core of the fiber. 9 In this work, some refractometric features of dual-core chirped MOFs are evaluated.…”

Label-free biosensor based on a dual-core transversally chirped microstructured optical fiber

“…Now, the refractive index of the layer of biomolecules directly modulates the device transmittance by its differential influence on the effective refractive index of each core mode, resulting in a variable phase difference between the optical path lengths of the interferometer arms. 9 Figure 2(a) shows the effective refractive index difference between the two fundamental modes that propagate through the fiber cores, Δn eff , as a function of wavelength. Although the difference between the two orthogonal polarizations is very small, the polarization state of the input beam may yields differences in the transmittance of the MOF, thus only the horizontal polarization is shown here.…”

“…The phase difference in Fig. 2(b) was approximated analytically by an exponential function, 9 which was then be used to derive the transmittance of the biosensor using the following expression:…”

Hybrid Fibre Grating Structure of an Optical Fibre Refractive Index Sensor

“…Experiment result proved that the resolution of the proposed method is higher than that of the improved way, and the CLBG device keeps higher sensitivity with this method. [9]optimized parameters of concatenated structure in the method of simulated and discussed the influence that the lengths, periods and dc induced index changes of FBG and LPG and length of optical fiber between LPG and FBG has to influence reflection spectrum. Secondly, based on the optimized parameters for concatenated structure, such structures are fabricated and used to monitor concentration and temperature simultaneously.…”