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Short pulse generation with a large tunable range from a very small quantum defect ytterbium-doped fiber (YDF) material is of much interest. A 3.06 µs and maximum repetition rate of 50.47 kHz Q-switched Yb doped fiber laser has been demonstrated by applying a passive technique based on a novel vanadium aluminum carbide (V2AlC) saturable absorber for the first time to the best of the authors' knowledge. The generated pulses showed high stability, with an obtained of 60 dB. The output of the laser can be tuned over a widely tunable range of wavelengths of about 17.3 nm from 1046.038 to 1063.39 nm. Q-switched YDF lasers would find use in many applications such as medicine, manufacturing, etc. [ABSTRACT FROM AUTHOR]

A simple and compact temperature sensor based on a Mach–Zehnder modal interferometer has been fabricated by bending a single-mode fiber into a balloon-like configuration. Three different fiber sections, fiber without stripping, fiber with a stripped-off protective coating and fiber with a polyvinyl alcohol (PVA) coating have been utilized, each with a small bending diameter of 1 cm that mimics a balloon-like shape. The PVA-coated segment sensor structure showed the highest sensitivity of ∼−1.492 nm °C−1, a fast response time of ∼2.78 ms and a good resolution of ∼3 × 10−4 °C, for the temperature range 30 °C–55°C, benefiting from the good thermo-optical properties of PVA. This sensor can potentially be used in various temperature monitoring processes such as food industries, chemical analysis, detection of molecular analysis and label-free biomedicine. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a compact pulsed dual‐wavelength Ytterbium‐doped fiber laser (YDF) based on Nickel nanoparticles (Ni‐NPs) as a Q‐switcher and optical stabilizer. By integrating the Ni‐NPs saturable absorber (SA) in the cavity, and adjust the 975 nm diode pump power to 185 mW, a self‐starting passively Q‐switched was generated at a central wavelength of 1038.5 nm. By exploiting the extra high nonlinearity of Ni‐NPs, the homogenous gain broadening of the YDF oscillator can be suppressed. Consequently, at a pump power of 195 mW, a stable dual‐wavelength passively Q‐switching laser has been generated at room temperature without any intracavity spectral filters or modulation elements. As increases the pump power up to the maximum value of 288 mW, the Ytterbium‐doped fiber laser observed that the smallest pulse width, the maximum repetition rate, and the maximum pulse energy of 1.44 μs, 100.1 kHz, and 4.45 nJ, respectively. The Ni‐NPs SA proof its potential in generating multiwavelength pulsed laser in the 1 μm region for different photonic applications. [ABSTRACT FROM AUTHOR]

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We propose and demonstrate the implementation and application of a new configuration of an all-fiber comb filter based on the Vernier effect produced by parallel-connected two in-line Mach–Zehnder interferometers (MZIs). Each in-line MZI was fabricated by fusion splicing a section of panda-type polarization maintaining fiber (PMF) with peanut-shaped tapers between two single-mode fibers. These two in-line MZIs, respectively, form reference and sensing interferometers, which are parallel-connected by two 3-dB optical fiber couplers to realize the Vernier effect. By incorporating the proposed comb-filter into the erbium-doped fiber laser cavity, two output channels at 1533.2 and 1558.2 nm have been achieved. Further, the combination of the parallel-connected two in-line MZIs and polarization controllers (PC1 and PC2) promotes the lasing in a switchable and selective way. To the best of the authors' knowledge, this is the first demonstration of a comb filter that employs paralleled two peanut-shaped MZIs in PMF. The experimental results indicate that the proposed filter has the potential to be used in communication systems. [ABSTRACT FROM AUTHOR]

In this paper, we describe the first demonstration of an optical fiber sensor based on two cascaded architectures of the Mach-Zehnder interferometer (MZI) with an up-down-tapered (UDT) hetero-core fiber structure for simultaneous pH measurement at two different spatial locations. The two fiber structures, namely structures I and II, were fabricated by sandwiching a 45 mm and 60 mm long piece of no-core fiber (NCF) between two single-mode fibers (SMFs), respectively. By inserting a down-taper between two adjacent up-tapers in the NCF section using the over-fusion splicing technique, the UDT hetero-core fiber structure was achieved. The down-taper works as an optical attenuator, while the two up-tapers each function as a fiber splitter/combiner. By cascading the two sensor structures I and II, two distinct interference dips were obtained, resulting in dual sensing points (so-called sensing points I and II). According to experimental results, it was shown that the proposed sensing points I and II are pH-sensitive, and exhibit sensitivities of 1.0428 nm/pH and -1.7857 n m / p H for simultaneous measurement for each point as the pH ranged from 8 to 14 and from 1 to 7 pH, respectively. The obtained results show that the proposed dual point pH sensor has the potential to be used for the simultaneous detection of pH parameters in any environment and at various places.

A simply designed, highly sensitive, stretchable, compact wearable, and skin-like optical fiber sensing instrument is designed and demonstrated for joint motion monitoring. The fiber sensing scheme comprises only a section of single-mode fiber (SMF) deformed in the knot-like configuration, which performs as a Mach-Zehnder interferometer (MZI) based on a modal coupling mechanism between the core and cladding modes of the deformed SMF section. This proposed optical fiber sensor based on a knot-like configuration is mounted onto wearable woven fabric and then garments on the limbs of a healthy human's body. As the flexion angle of the human limb is varied, the interference fringe coding based on the spectral shift difference of the periodical transmission spectra is perceived. The proposed wearable optical fiber sensor exhibits excellent sensitivities from around -0.431 to -0.614 n m / ∘ realized for elbow and knee joint flexion between a range of motion around 0°-90°. Additionally, this sensor also displays high repeatability and stability and a fast response time of 1.4 ms, combined with a small standard deviation of about 2.585%. The proposed sensor device possesses manufacturing simplicity, high processing accuracy, lightness, and elasticity, as well as certain improvements over other goniometers and optical fiber sensors. These attributes of the proposed sensor prove its applicability for human joint angle monitoring.