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A low-noise Brillouin random fiber laser (BRFL) based on dynamic fiber grating (DFG)-assisted self-injection locking (SIL) as a laser carrier for coherent communication is proposed and experimentally demonstrated. The utilization of the DFG-based SIL basically guarantees an innovative purification of ultra-narrow-linewidth laser radiation after the removal of residual random modes from the gain competition, enabling unprecedented long-term frequency-stabilized coherent lasing resonance over a record of 30 s. Consequently, the relative intensity noise of the generated Stokes random laser is significantly suppressed by ∼20 dB, and the frequency/phase noise imposed by random mode hopping is additionally mitigated. Meanwhile, stimulated Brillouin scattering and randomly distributed Rayleigh scattering along the kilometer-long single-mode fiber further suppress laser frequency/phase noise, benefiting the ultra-narrow laser linewidth of 450 Hz. As a proof-of-concept, an 8-Gbaud (32 Gb/s) 16-quadrature amplitude modulation transmission based on the proposed self-injection locked low-noise BRFL as the laser carrier is demonstrated, achieving a low bit error rate of 3.02 × 10 − 5 . The impact of the laser noise on coherent communication is systematically investigated, highlighting the potential in high-capacity coherent communication. [ABSTRACT FROM AUTHOR]

Whispering gallery mode resonators provide an intriguing platform for precision measurement due to their high responsivity and low detection limit. Here, we propose and demonstrate an optofluidic microbottle resonator (OFMBR) that is utilized to measure droplet gravity-induced mechanical force, realized by establishing a lever model between tapered fiber and OFMBR. The mechanical force can be amplified by adjusting the ratio of the load arm to the effort arm of the lever, which is validated by theoretical simulation. The evolved mechanical force deforms OFMBR morphology and enhances light scattering, resulting in mixed variations in the transmission spectrum, including resonance wavelength, mode linewidth, and signal intensity. Experimentally, the mechanical force is first measured by monitoring resonance wavelength shift, and a responsivity of −56 pm/mN is obtained within the range of 0–0.2 mN. Furthermore, to monitor the mixed variations in the transmission spectrum and obtain the actual mechanical force directly, the optical barcode method is utilized to simultaneously monitor the variations of multimode features. The arbitrary unknown mechanical force is determined by the cross correlation function, and the measurement resolution is about 5 µN. Our scheme provides a thread for characterizing the liquid properties and investigating the dynamics at solid–liquid interfaces. [ABSTRACT FROM AUTHOR]

We have proposed and demonstrated a cylindrical vector mode (CVMs) based Mach–Zehnder interferometer (MZI) in a vortex fiber (VF) for strain sensing. The VF has a coaxial structure supporting the fundamental mode of the HE11 mode in the center core and the first-order CVMs of TE01, HE21, and TM01 modes in the ring core, respectively. By applying a pair of separated microbend long period gratings (MLPGs), the HE11 mode is partially coupled to the CVMs and then combined for constructing an in-fiber MZI. Three separated interference spectra are observed distinctly corresponding to TE01, HE21, and TM01 modes, which exhibit a good linear response to the strain change. Among these three CVMs, the TE01 mode demonstrates the highest sensitivity of −2.41 nm/mε and temperature insensitivity feature. The low cross-sensitivity from temperature benefits the CVMs based MZI to be an ideal strain sensor without compensation, having potential applications of next-generation sensors in smart engineering structures. [ABSTRACT FROM AUTHOR]

The fabrication and characterization of Si1-xGex core fiber have attracted much attention because of its great application potential in new optoelectronic devices. In this work, by assembling two semi-cylindrical monocrystalline Si and Ge rods into a silica tube, we present a fabrication method to draw Si1-xGex core silica clad fiber with graphite furnace. Raman spectra analysis reveals that in all regions of the core formed the Si1-xGex alloy. The optical microscopic photograph shows that in the core of a diameter of 36 μm distributed the bright and dark regions, where it was further proved by Raman spectroscopy that the bright regions are Ge-rich areas and the dark regions are rich in silicon. By recording the Raman spectra of consecutive regions, it was found that with the increase of Ge content (x<0.5) the peak intensity of Si-Ge mode obviously increases, similar to the intensity of Ge-Ge mode, while the peak intensity of Si-Si mode decreases. Then we made a quantitative analysis of the components and strain by mapping the Raman spectra of the fiber core. The experimental results show that the Ge content mainly distributes between 0.1 and 0.8, concentrating between 0.2 and 0.3, and the strain distribution on the surface is obtained at the same time. [ABSTRACT FROM AUTHOR]