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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.

Due to the unique optical properties and good thermal stability, GeAsSeTe microstructured optical fiber (MOF) offers tremendous opportunity for applications in mid-infrared range (MIR). In this article, we design a CS2-filled GeAsSeTe MOF whose core, inner and outer cladding adopt Ge15As25Se15Te45, Ge20As20Se17Te43 and Ge20As20Se15Te45 glass, respectively. Highly efficient four-wave mixing (FWM) is realized and ultrabroadband optical parametric gain is obtained. By analyzing the central parametric gain bandwidth change with the temperature variation, this CS2-filled GeAsSeTe MOF is proved to be highly sensitive concerning temperature sensing, the sensitivity being as high as 2.32nm/°C from −80°C to 45°C. Such high temperature sensing property have key prominence for developing optical fiber temperature sensor in MIR region based on FWM. To the best of our knowledge, this is the first study to propose temperature sensing in the MIR by drawing on central parametric gain bandwidth of FWM change in a GeAsSeTe MOF.

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.

This article presented an investigation of nonlinear temperature sensing based on soliton self-frequency shift (SSFS) in an in-house fabricated microstructured optical fiber (MOF), and the sensing performance was evaluated by detecting the peak wavelength shift of soliton with the variation of temperature. Both theoretical simulation and experimental research were carried out and there was a good correspondence between the two results. The experimental sensitivity was as high as 0.451 nm/°C at 400 mW with a resolution of 0.2653 °C. Our work is a proof of concept of the optical fiber nonlinear phenomenon of SSFS to sensing technology. This temperature sensor does not involve additional fiber modification, and it has potential applications in biomedical, security, and harsh industrial environment.

An ultracompact optical fiber temperature sensor with a fiber-tip structure is proposed and demonstrated based on the Fabry–Perot (FP) interference principle. Composing a tellurite glass microcavity and a commercial multimode fiber, the proposed sensor is fabricated using a simple method of dipping. The theoretical analysis and experimental observation demonstrate that the ambient temperature can be detected by monitoring the wavelength shift of the reflection spectrum. The obtained sensitivity is about 62 pm/°C with linearity of 0.99982 in the range of 20 °C–170 °C. This sensor has great fringe contrast, high linearity, good stability, a wide detection range, and a short response time. It avoids the fusion difficulty between tellurite fiber and silica fiber, and provides a possibility for real-time temperature detection in the biological field and harsh industrial environment.

Fiber optical parametric amplifiers (FOPAs) have attracted much attention than conventional optical amplifiers due to their wider operating wavelength ranges. By expanding the FOPA gain bandwidth towards the mid-infrared region, which can only be obtained by using highly nonlinear chalcogenide fibers, more interesting applications in spectroscopy, sensing, biology and metrology can be realized. Chalcogenide hybrid microstructured optical fibers (chalco HMOFs) with buffer layer demonstrated by our group showed good FOPA performance from 3 to 10 μm. However, their tiny and symmetric structures of air holes are difficult to fabricate. To overcome, chalcogenide all solid HMOFs (chalco ASHMOFs) with 6 low-index rods in the cladding were studied in this work using As2Se3, AsSe2 and As2S5 glasses. Moreover, to obtain high birefringence which is necessary to minimize detrimental effects such as, polarization mode dispersion, polarization noise and instability and polarization-maintaining, the symmetry of the fiber was broken by enlarging a pair of solid rods. Numerical analyses show that chalco ASHMOFs can provide near-zero and flattened chromatic dispersion (

We demonstrate ultra-flattened (less than 1ps/km.nm) and near-zero chromatic dispersions profiles which can be tailored with high freedom by using our proposed chalcogenide all-solid hybrid microstructure optical fibers.

A double-clad single-mode tellurite optical fiber (DC-SMTOF) with a loss of 0.5 dB/m @1545.1 nm was fabricated based on the TeO2–ZnO–Li2O–Bi2O3 (TZLB) material. During the fiber drawing process, a low level of residual birefringence was produced, which gave a chance for the investigation of the polarization modulation instability (PMI). With a nanosecond laser operated at 1545.1 nm as the pump source, the PMI effect in the DC-SMTOF was investigated using different fiber length and different average pump power. This investigation of the PMI generation in non-silica optical fibers may provide guidance for the generation of the highly repetitive optical pulse train.

Due to the air-guiding characteristics of the air-core, hollow-core optical fibers (HCOFs) can give rise to many potential applications including optical data transmission, terahertz propagation, power beam delivery for industrial applications such as cutting, welding, and engraving, medical applications and chemical sensing. In this work, tellurite HCOFs which have 6 air holes in the cladding and a large hollow core in the center are studied. By numerical analysis, it was realized that the confinement loss in the core will be high when the gap between two nearby cladding air -holes is large or when they connect to each other. The light propagation and transmission properties were demonstrated experimentally from 0.4 to 4.0 μm. By carefully controlling the coupling conditions, lights were coupled successfully into the air core by the fundamental mode. The transmission spectrum included high transmission bands and low transmission bands alternately due to the effect of resonant reflection and anti-resonant reflection. Due to the current operating range of the laser source, the transmission spectrum was measured up to 3.9 μm. But, it is expected to extend to the mid-IR range around 6 μm as shown in the calculation. When the input light at 2.1 μm was linearly polarized, the polarization was maintained in the fiber because the fundamental mode was dominant and the coupling efficiency of the 1st order mode was very weak.

Supercontinuum (SC) has been applied in many applications such as optical coherence tomography, high-precision spectroscopy and frequency metrology [1]. SC can be generated in highly nonlinear fibers by launching high intensity laser pulses into these fibers. The dynamics of SC generation (SCG) closely relates to the chromatic dispersion of the fibers [2]. In the normal dispersion regime, the spectrum broadening dynamics is mainly based on self phase modulation and optical wave breaking which are self-seeded processes. Thus, the output SC preserves its high coherence. Highly coherent and broadband mid-infrared SCG in the all-normal dispersion regime was demonstrated by pumping at 8, 10, and 12 μm [3]. However, only few laser sources are able to provide such long wavelengths. Moving the pumping laser wavelengths to around 1.5 or 2 μm will be more attractive because many commercial fiber lasers are available. In this report, we propose a novel tellurite fiber for supercontinuum generation with a pumping laser at 2 μm. The fiber is obtained by adding six solid rods around the core of a step-index fiber. Such fiber is called all-solid hybrid microstructured optical fiber (ASHMOF). The fiber possesses flattened chromatic dispersion from 2 to 4 μm. Successful fabrication of the ASHMOF was done with an in-house drawing tower. Using a laser pumping at 2 μm into the ASHMOF, highly coherent and high spectral flatness supercontinuum spanning a range from 1.4 to 3.0 μm at - 20 dB level was experimentally generated. Such broad and highly coherent SC will be valuable for applications as optical coherence tomography, ultrafast transient absorption spectroscopy, etc.

The mid-IR supercontinuum generation has attracted much attention during the recent years because many unique molecular absorption bands of most of the molecules exist in this domain. Additionally, mid-IR supercontinuum light sources are expected to have potential applications including astro-photonics, bio-photonic diagnostics, nonlinear spectroscopy, infrared imaging and sensing. For high spatial resolution imaging a spatially coherent supercontinuum light source is desirable. The soft-glass optical fiber is the promising medium for the design and development of a high spatially coherent mid-IR light source with the high brightness. Earlier, the broadband mid-IR supercontinuum generation has been reported using the optical fibers in different materials including tellurite, and chalcogenide, but, its coherence property has not been demonstrated extensively. In this work, we experimentally demonstrate the mid-IR supercontinuum spectrum spanning ⁓1.6 μm to 3.7 μm using a 3 cm long tapered chalcogenide step-index optical fiber pumped with femtosecond laser pulses at 2.6 μm. To justify the experimentally obtained results, a numerical simulation also carried out for the same fiber and pulse parameters. The measured supercontinuum spectrum matches well with the simulated spectrum and generated supercontinuum spectrum is highly coherent within the whole spectral range of the supercontinuum generation.

High peak power mode locked fiber lasers are effective tools for many applications like optical metrology, biomedical imaging, micromachining and so on. All-fiber architecture and high pulse energy mode locked fiber lasers are very attractive to these applications due to their compactness and robustness. In recent years, an attractive mode-locking scheme based on Mamyshev regenerator was demonstrated to realize high pulse energy mode locked pulse output leading to breakthroughs in the mode locked fiber laser performance. We experimentally demonstrate an all-fiber linear Mamyshev regenerator operating at 1550 nm. Self-phase modulation and off-set spectral filtering provide high peak power pulse pick-up effect in the laser cavity and impel the laser to operate in the mode locking regime. With properly setting of the parameters, the all-fiber Mamyshev regenerator can achieve self-starting of the mode locking easily. No external pulse seeds or auxiliary starting arms are needed for the self-starting of the mode locking, which makes the laser very convenient to operate. Pulses with maximum energy of ~18 nJ and pulse width of 230 fs were achieved. The pulse width almost keeps unchanged with increasing in the pump power and the output power increases almost linearly with the pump power. The spectra from the two outputs with different pump powers were experimentally investigated as well. This high pulse energy Mamyshev regenerator can be used as a high quality and cost-effective laser source for many applications.

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/&deg, 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 proposed new chalcogenide all-solid hybrid microstructured optical fibers which provide flattened normal chromatic dispersion over a wide range from 4.5 to 13 pm and high phase birefringence up to 2.5x10-3 at 12 pm.

Spontaneous four-wave mixing in a novel tellurite fiber is demonstrated. Using a pumping laser at 1.9 um, a signal and an idler at 1.25 and 4.1 um are generated. This corresponds to a frequency shift of 85 THz which is the largest frequency shift in soft-glass fiber ever reported.

In order to take advantage of the 1.3- μ m emission of neodymium (Nd 3 + ) ions for many practical applications, we propose a tellurite all-solid photonic bandgap fiber (ASPBGF) to filter out the competing emission at 1.06 μ m which is most prominent in the emission spectrum of Nd 3 + ion. A novel Nd 3 + -doped tellurite ASPBGF is fabricated by using our developed tellurite glasses which have high compatibility of thermal properties and their refractive index difference is 0.096 at 1320 nm. The fiber is designed with 4 layers of high-index rods to have low confinement loss. The measured transmission spectrum of a 2.2-cm-long section of the fabricated fiber exhibits high transmission bands near 0.75 and 1.33 μ m (about −20 dB and −19 dB) and a low transmission band in the vicinity of 1.06 μ m which is about −27 dB. By using our fabricated Nd 3 + -doped tellurite ASPBGF, it is demonstrated for the first time that the 1.06- μ m emission peak due to the 4 F 3∕2 → 4 I 11∕2 transition of Nd 3 + ions is greatly suppressed about 12 times as compared to that obtained by using a bulk samples with the same doping concentration.

We investigate fourth-order cascaded Raman shift in a birefringence ZrF 4 –BaF 2 –LaF 3 –AlF 3 –NaF (ZBLAN) fluoride fiber, which is the first demonstration of cascaded Raman shift in fluoride fibers. The pump source is a commercially available 1064 nm picosecond fiber laser. At the average pump power of ∼7 W, fourth-order cascaded Raman shift is observed if the pump pulse is polarized to the slow axis, and third-order cascaded Raman shift is obtained if the pump pulse is polarized to the fast axis. The Raman shift generation is simulated by the generalized nonlinear Schrodinger equation (GNLSE), and the results are in good agreement with the experiments.

We demonstrated in this work the wavelength conversion performance based on the four-wave mixing process in a new tellurite step-index fiber as short as 1 m. The fiber was pumped by a femtosecond pulsed laser near the zero dispersion wavelength of the fundamental mode which was close to that of the material dispersion in the near-infrared region. When the pump and signal wavelengths were at 1795 and 1434 nm, respectively, the generated idler was obtained at 2400 nm and the conversion wavelength spacing could be as broad as 966 nm. In addition, a 17.5-dB signal gain at 1550 nm and 1.1-dB idler at 1757 nm were obtained when the pump was tuned to 1647 nm.

We systematically investigate the effect of chromatic dispersion on supercontinuum generation in tellurite all-solid hybrid microstructured optical fibers. Highly coherent and broad supercontinuum from the near to mid-infrared region can be generated in the designed fibers.

We report an all-fiber dual-wavelength dual-comb mode locked fiber laser based on a Sagnac fiber loop mirror. Two asynchronous mode locked pulse trains with repetition rate difference of 218 Hz was realized.

Stimulated Raman scattering (SRS) is a nonlinear effect in the media which can transfer a fraction of power from one optical field to another and whose frequency is downshifted by an amount determined by the vibrational modes of the medium [1, 2]. When Raman gain of the optical fiber is high and pump power into it is sufficient, cascaded SRS effect can be achieved [3, 4]. In this paper, a low-loss chalcogenide optical fiber was designed and fabricated based on A S -S glass, and a 16 m long fiber was experimentally used to enhance Raman gain for boosting cascaded SRS generation. A nanosecond laser at ∼1545 nm was used as the pump source and mid-infrared cascaded SRS up to eight orders was observed.

We report a tellurite all-solid hybrid microstructured fiber with ultra-small chromatic dispersion fluctuation which has the potential as mid-infrared fiber optical parametric amplifier medium.

Mid-IR supercontinuum generation has attracted lot of attention in recent years because many unique molecular absorption bands exist in this region [1], Additionally, mid-IR supercontinuum light sources are expected to have potential applications including bio-photonic diagnostics, nonlinear spectroscopy, and infrared imaging [2–4], For high-spatial-resolution imaging a spatially coherent supercontinuum light source is desirable. The optical fiber is the promising medium for the design and development of a highly spatially coherent mid-IR light source with the high brightness. Earlier, the broadband mid-IR supercontinuum generation has been reported using the optical fibers in different materials including tellurite, and chalcogenide, but, its coherence property has not demonstrated extensively. Recently, our group has demonstrated coherent mid-IR supercontinuum generation in step-index tellurite, tapered tellurite, and chalcogenide double clad fibers pumped with femtosecond laser [5–7].

Chromatic dispersion controlling is crucial in designing practical optical communication systems, and nonlinear systems. Ultra-flattened chromatic dispersion has been numerically performed in silica photonic crystal fibers (PCFs) whose chromatic dispersion variation can be as small as ±0.5 ps/km/nm. However, keeping arrays of air holes at precise sizes and shapes is highly required to realize the targeted dispersion. Consequently, this requires much effort in controlling air pressure during fiber fabrication and is considered as a disadvantage of PCFs. In this report, we propose a novel fiber structure for flexible controlling of chromatic dispersion. The fiber structure is obtained by adding six solid rods around the core of a step-index fiber. Ultra-flattened and close-to-zero chromatic dispersion can be realized by using this fiber structure. The variation of chromatic dispersion from 2.5 to 3.7 μm is as small as 0 ± 0.2 ps/km/nm. Using a laser pumping at 2 μm into a 5-cm-long fiber, highly coherent supercontinuum (1.2 – 3.3 μm at -20 dB level) is experimentally generated.

After publication of the paper, the authors realized that the signal gain in Fig. 6b, d, f was calculated using Gs = 10ln[Ps(L)/Ps(0)].

Neodymium (Nd)-doped fibers are potential candidates for optical fiber amplifiers operating near the 1.3-μm spectral region due to the 4F3/2→4I13/2 transition of Nd3+ ions. But, there is an amplified spontaneous emission at 1.06 μm due to the 4F3/2→4I11/2 transition whose branching ratio is about 5 times larger than that at 1.3 μm. In order to suppress the transmission of the 1.06-μm emission, we propose a new tellurite all-solid photonic bandgap fiber (ASPBF) with a single line of high index rods and double cladding layers. Tellurite glasses of TeO2-Li2O-WO3-MoO3-Nb2O5 (TLWMN), TeO2- ZnO-Na2O-La2O3 (TZNL) and TeO2-ZnO-Li2O-K2O-Al2O3-P2O5 (TZLKAP) are developed. High-index rods of TLWMN and an Nd-doped TZNL rod are arranged symmetrically and horizontally in the x-axis of a hexagonal TZNL cladding. The outer cladding is made of the TZLKAP glass. The finite element method is used to calculate the mode distribution and the bandgap properties. The fiber transmission spectra are numerically investigated with the effects of rod diameter and filling factor variation. When the core diameter is 3.0 μm, rod diameter is 2.3 μm and filling factor is from 0.7 to 0.8, the 1.06-μm emission which is caused by the 4F3/2→4I11/2 transition can be suppressed as compared with the 1.33-μm emission which is caused by the 4F3/2→4I13/2 transition.

We propose chalcogenide all-solid hybrid microstructured optical fibers for mid-infrared supercontinuum generation pumped with lasers at short wavelengths. The supercontinuum spectra are from 1.3 to 7 µm and highly coherent.

An Nd3+-doped tellurite all-solid photonic bandgap fiber with one-dimensional asymmetric periodic structure of high-index rods is demonstrated as a promising solution to suppress the emission at 1.06 µm of Nd3+ ions.

The accuracy of the surface plasmon resonance (SPR) optical fiber sensor is affected by the change of ambient temperature. Therefore, we propose a simple dual channel SPR optical fiber sensor, which can measure both glucose concentration and ambient temperature. The proposed sensor is a two-channel structure based on a no-core optical fiber (NCF): one channel is coated with gold film and polydimethylsiloxane (PDMS) to sense the ambient temperature, and the other is coated with silver film to sense glucose concentration. The experimental results show that the sensor’s sensitivity for sensing glucose concentration is 2.882 nm / %, and for sensing temperature is -2.904 nm / °C. By monitoring the real-time temperature, the accuracy of glucose concentration detection was improved. The proposed sensor has a simple and compact structure, and it is suitable for sensing glucose solution or other analyte solutions that need temperature compensation.

In this work, the temperature (strain) properties of As2Se3 π-phase-shift fiber Bragg gratings (π-PSFBGs) are numerically investigated. The sensing sensitivities are 0.0665 nm °C−1 (0.8598 pm μϵ −1) at 1.55 μm, 0.1546 nm °C−1 (1.9968 pm μϵ −1) at 3.6 μm, 0.2717 nm °C−1 (3.51 pm μϵ −1) at 6.328 μm, and 0.4551 nm °C−1 (5.8796 pm μϵ −1) at 10.6 μm, and the sensitivities are improved with the increasing Bragg wavelength. Based on them, a high-performance narrow band fiber laser is theoretically proposed. The proposed tunable laser has a wider wavelength adjustment range in mid-infrared region, which can reach 27.306 nm at around 10.6 μm. Moreover, the obvious Bragg wavelength shift induced by stretching the As2Se3 π-PSFBG helps widen the tunable range of the laser, making possible a fine tuning. Being simple in structure and high in sensitivity, the proposed laser can be applied in mid-infrared region, which is the fingerprint region of numerous molecules and which closely relates to military aviation, environmental conservation, biology and health care regions.

Passively mode-locked pulses generated in a thulium-doped fiber laser was demonstrated by the ReS2 nanoparticles. The ReS2 nanoparticles are introduced into the laser cavity on a side polished fiber through optical deposition method, which works as a saturable absorber. Self-starting mode-locking can be established quickly when the pump power is higher than 700 mW. The central wavelength and the 3 dB bandwidth of single pulse operation are 1970.65 and 5.05 nm, respectively. The pulse repetition is 26.1 MHz and the full width at half maximum is 893 fs with the time-bandwidth product of 0.348.

We demonstrate soliton self-frequency shift (SSFS), multiple optical solitons and supercontinuum (SC) generation in a tellurite microstructured optical fiber (TMOF). By using an optical parametric oscillator (OPO) with the pulse of ∼80 MHz and ∼200 fs as the pump source, the evolution of SSFS is investigated at the pump wavelengths of ∼1730, 1750, 1810 and 1900 nm with the fiber length of ∼20 cm. At the pump wavelength of ∼1730 nm, SSFS with the soliton center wavelength from ∼1850 to 1995 nm is observed. Increasing the pump wavelength to ∼1920 nm and the fiber length to ∼100 cm, stable multiple optical solitons and dispersive waves (DWs) are obtained. Changing the pump source to a SC source which is generated in a single mode fiber (SMF) pumped by a nanosecond laser with the wavelength of ∼1550 nm, a broadband SC spectrum from ∼580 to 2796 nm is obtained at the pump power of ∼202 mW. To the best of our knowledge, this is the first demonstration of SC generation in the TMOF by using SC light generated by a nanosecond laser.

We design and fabricate a silica optical fiber doped with yttrium aluminosilicate (YAS, Y 2 O 3 –Al 2 O 3 –SiO 2 ) nanoparticles in the core. The optical fiber is drawn directly from a silica tube with YAG (Y 3 Al 5 O 12 ) ceramics and silica powders (the molar ratio 1:18) in the core at the temperature of ∼1950 °C. The YAS nanoparticles are formed during the optical fiber drawing process. Supercontinuum (SC) generation in the optical fiber is investigated at different pump wavelength. At the pump wavelength of ∼1750 nm which is in the deep anomalous dispersion region, SC spectrum evolution is mainly due to multiple solitons and dispersive waves (DWs), and three pairs of multiple optical solitons and DWs are observed. When the pump wavelength shifts to ∼1500 nm which is close to the zero-dispersion wavelength (ZDW), flattened SC spectrum with ±7 dB uniformity is obtained at the wavelength region of ∼990–1980 nm, and only one obvious soliton and DW are observed. At the pump wavelength of ∼1100 nm, a narrow SC spectrum from ∼1020 to 1180 nm is obtained in the normal dispersion region due to self-phase modulation (SPM) effect.

In this work, a low-loss As2S5 optical fiber with 0.1 dB/m at 1545 nm was designed and fabricated, whose residual birefringence provided an opportunity for investigating the polarization modulation instability (PMI). Using a nanosecond laser operated at ∼1545 nm as the pump source, PMI and the stimulated Raman scattering (SRS) were experimentally investigated in a 3 m As2S5 optical fiber. During the SRS process, the amplified CW signal at 1632 nm and 1633 nm induced the PMI. To the best of our knowledge, this is the first report on the PMI effect induced by the amplified signal in the first-order SRS. The PMI gain was measured to be 24.4 dB at the signal of 1551 nm with the pump power of 20 mW, and the Raman gain was measured to be 31.2 dB at the signal of 1632 nm with the pump power of 41 mW. This investigation on the PMI gain and Raman gain in the As2S5 optical fiber may provide a reference for the development of fiber amplifiers, fiber lasers, and optical communication.

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.

Mid-infrared supercontinuum generation from 1.5 to 4.5 &micro, m 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 Schr&ouml, dinger equation are used to determine optimized fiber parameters before experimental demonstrations. We also analyse the coherence properties of the resulting supercontinuum sources.

Mid-infrared cascaded Stimulated Raman scattering (SRS) is experimentally investigated in an AsS optical fiber which fabricated based on As38S62 and As36S64 glasses and whose fiber loss was ∼0.09 dB/m at ∼2000 nm. Using a nanosecond laser operated at ∼1545 nm as the pump source, mid-infrared cascaded SRS up to eight orders is obtained in a 16 m AsS fiber. To the best of our knowledge, this is the first demonstration of eighth-order cascaded SRS in non-silica optical fibers, and it may contribute to developing tunable Raman fiber lasers in the mid-infrared region based on the C-band pump sources. When the pump wavelength switches to ∼2000 nm, only mid-infrared cascaded SRS up to five orders is obtained.

A tellurite all-solid photonic bandgap fiber (ASPBF) whose cladding consists of 60 high-index rods arranged periodically around a central core was successfully fabricated. The diameter of high-index rod was about 5.0 μm and the distance between the center of two adjacent high-index rods was approximately 8.0 μm. The high-index rod was made of the TeO2-Li2O-WO3-MoO3-Nb2O5 (TLWMN) glass, the cladding was made of the TeO2-ZnO-Na2O-La2O3 (TZNL) glass as the background glass material and the central core was made of TZNL glass doped with 0.5 wtp of Nd2O3. A supercontinuum light from 0.6 to 2.4 μm was coupled into the core of fiber which is 2.2 cm long to measure its transmission spectrum. High transmission bands were obtained in the vicinity of 0.75 and 1.3 μm but the transmission was suppressed in the wavelength range from 1.0 to 1.06 μm. When a titaniumrSapphire laser source at 0.75 μm was used, the emission spectrum was obtained with two peaks at 1.06 and 1.33 μm which are attributed to the 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions of Nd3p ion, respectively. The intensities of those emission peaks were compared with those obtained from a bulk glass having the same doping concentration of Nd3p. The results showed that by using tellurite ASPBF, the intensity of the 1.06-μm emission was suppressed by one-twelfth but the intensity of the 1.33-μm emission was maintained. This feature is very advantageous to filter out the 1.06-μm emission of Nd3p ion in order to realize practical amplifier devices at 1.3 μm.

The mid-infrared (MIR) range is of great interest because fundamental molecular vibrational absorption bands exist in the MIR range. In the MIR range, typically, lasing can be generated using quantum cascade lasers, cascaded Raman lasers, and optical parametric oscillators (OPOs). Recently, fiber OPOs (FOPOs) in the MIR range have received attention because of their flexibility of the parametric gain curve designing the chromatic dispersion. Chalcogenide glass is the promising candidate for MIR FOPO because of their wide transmission window and high nonlinear coefficient. In the present paper, we design the chromatic dispersion of four-hole As2S5 chalcogenide suspended core fiber (SCF), and demonstrate a far-detuned four-wave mixing (FWM) for MIR FOPO. We design the four-hole As2S5 chalcogenide SCF for far-detuned FWM using a ∼2 μm pump source. A four-hole As2S5 chalcogenide SCF which has a core diameter of 3.25 μm is fabricated using a homemade draw tower. We experimentally observed far-detuned FWM in the four-hole As2S5 chalcogenide SCF. A detuning frequency of over 80 THz is measured in 21 cm long fiber using a 2.7 ps pulse laser at 1.96 μm. The experimental observation was confirmed by numerical demonstration.

We experimentally demonstrated mid-infrared wavelength conversion using a chalcogenide suspended-core fiber pumped with a pico-second pulse.

Brillouin comb generation in a ring cavity composed of a piece of tellurite single mode fiber was demonstrated. Cascaded stimulated Brillouin Stokes and anti-Stokes lines resulted in multi-wavelength Brillouin comb generation bi-directionally.