Microfiber interferometer with surface plasmon-polariton involvement.

We fabricated a microfiber interferometer with surface plasmon-polaritons (SPPs) involvement. Commonly, the SPPs are not involved in interference due to the mismatch momentum and ultrashort propagation distance. In this Letter, an absorber-doped microfiber is utilized for increasing the matched momentum (i.e., their modal projection), and as a result, an SPP is coherent with an end-fire method-stimulated hybrid SPP. A mathematical model is proposed for investigating the modal-projection-caused interference, and its results show that the proposed interferometer is very dependent on the polarization. Confirmation experiments were carried out, and a good agreement between theoretical predictions and experimental results was found. The proposed interferometer will potentially facilitate many SPP studies in directly related fields.

Fiber refractive index sensor based on dual polarized Mach-Zehnder interference caused by a single-mode fiber loop.

A novel refractive index (RI) sensor head is proposed and experimentally demonstrated in this paper. The proposed sensor head is composed of a segment of bared single-mode fiber and a fiber holder that is fabricated by a 3D printer. The mechanism of the sensor head is based on dual polarized Mach-Zehnder interference. According to the aforementioned mechanism, we derived that the RI responses of the resonance dips possess an exponential functional manner when the E field is along the fast or slow axes. In addition, based on the finite element method, we found that the resonance dips wavelength responses are more sensitive when the input E field is along the fast axis. A confirmation experiment was performed, and the results confirmed our hypothesis. The maximum arithmetic mean value of RI response is about 657.895 nm/RIU for the proposed sensor head when the ambient RI changes from 1.3350 to 1.4110. Moreover, in the case of the proposed liquid RI sensor head, aligning the E field along the fast axis is the potentially needed condition for polarization.

Photonic crystal fiber polarization rotator based on the topological Zeeman effect.

A photonic crystal fiber polarization rotator (PR) is proposed based on the topological Zeeman effect. The proposed PR is achieved by permanently twisting a segment of sixfold symmetric photonic crystal fiber with a matched length, and under the optimized parameters, the PR can offer an almost 100% polarization conversion ratio in the wavelength of 1.55-µm band (∼200 nm bandwidth) and a compact length of about 157 µm based on the numerical simulation result of the full-vector finite-element method. The proposed in-line PCF PR can be easily fabricated based on state-of-art PCF manufacturing, and it is a potential inexpensive candidate in the application of modern communication systems.

In-fiber torsion sensor based on dual polarized Mach-Zehnder interference.

This paper presents a novel optical fiber torsion sensor based on dual polarized Mach-Zehnder interference (DPMZI). Unlike the conventional fiber sensor, the proposed sensor is composed of a sensor part and a demodulator. The demodulator is made by a bared single mode fiber (SMF) loop, and the sensor part is a segment of a coated SMF placed before the loop. A mathematical model is proposed based on DPMZI mechanism and from the model when the sensor part is twisted, the E-field rotational angle will bring a quasi-linear impact on the resonance dip wavelength in their matched detecting range. A proof-of-concept experiment was performed to verify the theoretical prediction. From the experimental data, a sensitivity of -0.3703, -1.00962, and -0.59881 nm•m/rad is achieved with the determining range of 12.0936, 7.6959, and 10.4444 rad/m respectively. The sensor which is composed only of the SMF has the advantages of low insertion loss (~-2dB), healthy structure, low manufacture cost, and easy assembly and application.

Real time and simultaneous measurement of displacement and temperature using fiber loop with polymer coating and fiber Bragg grating.

An all-fiber sensor scheme for real time and simultaneous displacement and temperature measurement is presented and demonstrated. The sensor head is formed by cascading a fiber loop with polymer coating with a fiber Bragg grating. The compatibility of the two components is fully utilized. A sensor resolution of 0.14314 V/µm in displacement and 0.00795 nm/°C in temperature are experimentally achieved within a displacement range of 0-50 µm and a temperature range of 20 °C-75 °C, respectively. The fiber loop with the protection of polymer coating is mechanically reliable, which means the sensor head also suits measuring dynamic displacement. A 500 Hz mechanical micro-vibration is successfully measured by the proposed sensor experimentally. In the last part, we perform a test making the sensor reach its maximum deformation and find the surviving sensor still possesses the same responsiveness as before.