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• Easily handling C-band passively Q-switched erbium doped fiber laser nm has been demonstrated. • Easily spliced large core diameter coreless fiber is served as a saturable absorber for Q-switching ignition. • High pulse repetition rate of 73.3–92 KHz without any intra-cavity tuning element has been obtained. • Stable output pulses of SNR of 50 dB is generated. We demonstrated a Q-switched erbium-doped fiber laser (EDFL) based on large diameter coreless fiber without intra-cavity tuning element for the first time. A single mode fiber –coreless fiber –single mode fiber (SNCFS) structure was employed as a passive Q-switcher relies on Kerr nonlinearity associated with multi-mode interference (MMI) effect. By splicing 10 cm of 125 µm in diameter coreless fiber (NCF) between two single mode fibers (SMFs), C-band Q-switched EDFL with 3-dB bandwidth of 0.138 nm was successfully obtained, making it a simple, compact and easily handling modulation device. A stable Q-switched pulses were achieved with a pump threshold of 188 mW. Pulse repetition rate ranges from 73.3 to 92.0 kHz, minimum pulse width of 3.5 µs and maximum energy of 50.9 nJ were recorded. [ABSTRACT FROM AUTHOR]

• Wearable Optical Fiber Sensor based macro-bending loss for Biomechanical Motion Evaluation. • A U-shaped fiber sensor has been integrated into elbow and knee joint phantoms and measuring its response to various elbow and knee joint movements in the range of 0°-90°. • The recorded sensing data revealed an extra sensitivity of −0.457 nm/° with linear regression coefficients of more than 98.7 % for elbow flexion angle and a 0.506 nm/° sensitivity with a high linear regression coefficient of ∼ 99.6 % for knee flexion angle. • The proposed sensor exhibits a high sensitivity which it significantly improves the optical sensing signal to more than 5.5 times in correspondence with many previous published works. The biocompatibility and other unique physical properties of optical fibers reflect their potential for use in biomechanical motion sensing. In this paper, a wearable macro-bending structure fiber sensor has been fabricated and its potential is demonstrated for observing key motions during physical therapy for patients with joint stiffness. The sensor's performance has been evaluated by integrating it into elbow and knee joint phantoms and measuring its response to various elbow and knee joint movements in the range of 0°-90°. The recorded sensing data revealed the extra sensitivity of −0.457 nm/° with linear regression coefficients (R2) of more than 98.7 % for elbow flexion angle and a 0.506 nm/° sensitivity with a high linear regression coefficient (R2) of ∼ 99.6 % for knee flexion angle. Additionally, good reproducibility and swift response facility were demonstrated during the experiment, indicating that the designed sensor possesses enormous potential in terms of different body motion monitoring applications, even subtle ones. The results show that the sensor's high sensitivity leads to a very good correlation between the sensor's output and the actual elbow joint movement. [ABSTRACT FROM AUTHOR]

• The utilization of PbS solution as saturable absorber without polymer host material. • Highly stable Q-switched pulses of ~63 dB. • Low threshold pump power of 73 mW. • Broad spectral bandwidth with 4.23 nm at FWHM. We report on Lead Sulfide (PbS) dispersed in sodium dodecyl sulfate (SDS) used as a saturable absorber (SA) in erbium-doped fiber laser (EDFL) ring cavity configuration. It has been fabricated in a suspension form by simple method for flexible usage with high stability. Then, the prepared SA was integrated in the EDFL cavity producing passively Q-switched pulses at wavelength of 1566.3 nm with 3 dB bandwidth of 4.23 nm. Stable short pulses of 8.55–3.43 µs were generated as the corresponding pump power increased from 73 to 300 mW while the repetition rate tuned from 14.86 to 38.71 kHz accordingly. The maximum pulse energy obtained by the present setup was 10.6 nJ at maximum input pump power. The high signal-to-noise ratio (SNR) of proposed PbS-SDS based SA of ~63 dB represents a considerable stable Q-switched EDFL and proves a high prospect to be used in practical photonic applications. [ABSTRACT FROM AUTHOR]