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In this paper, a section of tellurite no-core optical fiber (NCF) is compactly sandwiched between two segments of tellurite single-mode optical fibers (SMF) to form multimode interference (MMI) sensor for refractive index (RI) measurement. Theoretical investigation reveals that the sensitivity of this MMI-based RI sensor can be enhanced by reducing the diameter of the NCF. As the NCF diameter is lowered to 20 µm, the sensor presents good RI sensing performance in the mid-infrared range of 2–5 µm and the sensitivity rises with the increase of the wavelength. At 4–5 µm and within the detectable RI range of 1.36–1.63, the maximum sensitivity is 3069.1 nm/RIU. The proposed sensor combines the material superiority of tellurite glass and the structural advantage of the SMF-NCF-SMF sensing unit, exhibiting high sensitivity and wide detection range in terms of RI sensing. It provides a new method for detecting the concentration of toxic organic compounds with high RI.

In this paper, multi-pair cross-phase modulation instability (XPMI) induced by multiple modes was experimentally observed in the deep normal dispersion regime of a tellurite high birefringence microstructured optical fiber (HBMOF) fabricated based on 76.5TeO2-6Bi2O3-11.5Li2O-6ZnO (TBLZ) glass. At the pump wavelength of 1062.7 nm three modes were emitted, whose modal birefringence was on the order of >10-5, providing a good platform for the multi-pair XPMI generation. During the experimental investigation, a picosecond laser was adopted as the pump source, and a three-pair XPMI induced by the three modes was observed in the deep normal dispersion regime of the tellurite HBMOF. This work May provide reference for the development of multi-wavelength fiber amplifiers and all-optical modulators.

An ultra-high sensitivity refractive index sensor is proposed and designed by integrating plasmonic Mach-Zehnder interferometer and the optical fiber structure together. The configuration, the numerical simulations and the performance of the proposed structure have been analyzed and discussed by the finite element method. At the working wavelength of 1.55 μm, the designed sensor is optimized to obtain the sensing sensitivity 20141.7 nm/RIU. Furthermore, it is found that with the increase of the working wavelength, the sensitivity will also increase, thus the proposed sensor has the potential to work in the near-infrared band. This sensor not only shows a high sensitivity to refractive index detection, but also is highly applicable in the detection of liquid concentration, gas concentration or temperature.

A Fabry-Perot interferometer (FPI) temperature sensor was proposed by splicing a self-made hollow core anti-resonance fiber (HC-ARF) between two single mode fibers (SMFs). The HC-ARF was 2 mm long and one SMF was 20 mm in length. The SMF end face was coated with an Au film. When temperature varied from 45 °C to 85 °C, a sensitivity of 81.1 pm/°C was obtained at the waveband of 1550 nm∼1555 nm. When temperature varied from 35 °C to 95 °C, a sensitivity of 138.8 pm/°C was obtained at the waveband of 1571 nm∼1581 nm. Theoretical analysis suggested that the sensitivity of this proposed sensor can be easily adjusted by varying the length of the Au-coated SMF via the Vernier effect, which was confirmed by a subsequent experiment where the SMF length was varied from 20 mm to 170 mm. This work offers a simple sensitivity control method, and the proposed sensor is easy to manufacture, compact in structure, and convenient in performance control, which can be applied for a wide range of biological and chemical applications.

Cascaded cross-phase modulation instability (XPMI) is experimentally observed in the normal dispersion regime of a birefringent tellurite microstructured optical fiber (BTMOF). At the average pump power of ~33 mW, cascaded XPMI with nine stokes sidebands and six antistokes sidebands is observed in a 3-m BTMOF. To the best of our knowledge, this is the first demonstration of cascaded XPMI in nonsilica optical fibers. The influence of fiber length variation on the evolution of cascaded XPMI is investigated by using a 0.3-m BTMOF. At the same pump power, cascaded XPMI with only eight stokes sidebands and five antistokes sidebands is observed. This is because shorter fiber length leads to lower nonlinear effect, which in turn induces less obvious XPMI effect.

According to the beam propagation method, a fiber refractive index-sensitive multimode interference (MMI) structure fabricated by splicing a self-made silica glass rod between two single mode fibers (SMF–NCF (no core fiber)–SMF structure) is proposed for liquid level monitoring. Theoretical and experimental investigation was carried out meticulously using a 4.5 cm and a 9.5 cm long silica glass rod. It is proved that the simple and economical sensor with the shorter length has high sensitivity, satisfactory repeatability, and favorable stability. The sensitivity climbs with the increase in refractive index of the measured liquid, which is 204 pm/mm for pure water, 265.8 pm/mm for 10% glycerin solution, and 352.5 pm/mm for 25% glycerin solution. The proposed sensor can be standardized in certain application circumstances to achieve accurate liquid level monitoring.

For this study, a temperature sensor utilizing a novel tellurite photonic crystal fiber (PCF) is designed. In order to improve the sensor sensitivity, alcohol is filled in the air holes of the tellurite PCF. Based on the degenerate four-wave mixing theory, temperature sensing in the mid-infrared region (MIR) can be achieved by detecting the wavelength shift of signal waves and idler waves during variations in temperature. Simulation results show that at a pump wavelength of 3550 nm, the temperature sensitivity of this proposed sensor can be as high as 0.70 nm/°C. To the best of our knowledge, this is the first study to propose temperature sensing in the MIR by drawing on four-wave mixing (FWM) in a non-silica PCF.

We demonstrate a highly efficient, stable, and tunable dispersive wave (DW) emitted by the soliton in a tellurite microstructured optical fiber. The dependence of the generated DW properties on the average pump power is experimentally investigated. By using the 80-MHz pulse emitted from an optical parametric oscillator as the pump source, the DW from ~1626 to 1685 nm is obtained with the average pump power changing from ~250 to 440 mW at the pump wavelength of ~1760 nm. The conversion efficiency is over ~65%. The full width at half maximum (FWHM) of DW pulse at the center wavelength of 1626 nm is ~90 fs, which was measured by an intensity autocorrelator. The stable DW pulse can be used as a near-infrared femtosecond source.

Ultrafast all-optical signal modulation induced by optical Kerr effect (OKE) was demonstrated in an all-solid tellurite photonic bandgap fiber (PBGF) which was designed and fabricated based on TeO2-Li2O-WO3-MoO3-Nb2O5 (TLWMN, high-index rods), TeO2-ZnO-Na2O-La2O3 (TZNL, background), and TeO2-ZnO-Li2O-K2O-Al2O3-P2O5 (TZLKAP, cladding) glasses. At the input of a control pulse with high intensity, OKE occurred in the tellurite PBGF and the transmission bands of the tellurite PBGF shifted. The signal at 1.57 μm transmitting in the fiber core can be ultrafast all-optically modulated by the ultrafast single pulse (200 kW, 200 fs) under OKE, where the modulation speed can reach 50 GHz, faster than some commercial LiNbO3 modulators. The results in this paper can be applied to multi-monitors, local area network, detectors, multi-sources, etc.

Mid-infrared supercontinuum generation from 1.5 to 4.5 µm with sub-nanojoule femtosecond pump pulses is demonstrated by using a short segment of dispersion-engineered step-index tellurite fiber with very low OH content. Distinct group-velocity dispersion regimes in a simple design of step-index tellurite fiber are also reported, which allows to choose the nonlinear pulse propagation regime according to the required tailoring of the supercontinuum source. Numerical simulations based on the generalized nonlinear Schrödinger equation are used to determine optimized fiber parameters before experimental demonstrations. We also analyse the coherence properties of the resulting supercontinuum sources.

Dynamic bandgap control in all-solid chalcogenide-tellurite photonic bandgap fiber (PBGF) by the refractive index changes due to the optical Kerr effect is numerically simulated in this paper. The core and the cladding with low index are designed by the tellurite glass TeO2-ZnO-Li2O-Bi2O3, whereas the high-index rods are designed by the chalcogenide glass GeGaSbS. Because all-solid chalcogenide-tellurite PBGF has higher nonlinear refractive index than the conventional silica PBGF, when the high peak power transmits in this fiber, the refractive index will change due to the optical Kerr effect, and so will the bandgap.