An optimized multi-step index (MSI) 2-LP-mode fiber is proposed and fabricated with low propagation loss of 0.179 dB/km, low intermodal crosstalk and excellent bend resistance. We experimentally clarified the characteristics of backward Brillouin scattering (BBS) and forward Brillouin scattering (FBS) induced by radial acoustic modes (R_0,m) in the fabricated MSI 2-LP-mode fiber, respectively. Via the use of this two-mode fiber, we demonstrated a novel discriminative measurement method of temperature and acoustic impedance based on BBS and FBS, achieving improved experimental measurement uncertainties of 0.2 °C and 0.019 kg/(s·mm²) for optoacoustic chemical sensing. The low propagation loss of the sensing fiber and the new measurement method based on both BBS and FBS may pave the way for long-distance and high spatial resolution distributed fiber sensors.

Surface plasmon resonance (SPR) optical fiber methane sensors provide promising routes for gas monitoring, yet most existing anti‐resonant hollow‐core fiber (ARHCF) SPR schemes lack multi‐parameter collaborative analysis and detailed polarization‐dependent mechanism interpretation. In this paper, we computationally investigate an SPR methane sensor based on inner‐gold‐coated ARHCF using the finite‐element method. Three critical structural parameters, including gold‐film thickness, methane‐sensitive cryptophane‐A film thickness, and anti‐resonant tube wall thickness, are comprehensively studied. The Y‐polarized FM exhibits higher confinement loss and stronger SPR coupling, while the X‐polarized mode delivers more stable sensing response against structural variation. As the gold‐film thickness increases from 30 nm to 37 nm, the SPR resonance wavelength shows a stable linear blue‐shift. A distinctive non‐monotonic spectral response accompanied by an abrupt wavelength jump is observed when adjusting sensitive‐film thickness within 2.5–3.5  μ m, and optimal sensing performance is obtained at 3.0 μ m sensitive‐film thickness. Tuning anti‐resonant tube thickness can effectively shift the SPR resonance wavelength, achieving maximum coupling strength at 0.30 μ m. Benefiting from the open hollow‐core architecture, the proposed sensor enables sufficient gas‐light interaction. This work clarifies parameter‐modulation mechanisms and offers feasible design references for ARHCF‐based SPR methane gas sensors.

We optimized and fabricated an ultra-bend-resistant 4-core simplex cable (SXC) employing 4-core multicore fiber (MCF) suitable for short-reach dense spatial division multiplexing (DSDM) optical transmission in the O-band. The characteristics of transmission loss, macro-bending and cross-talk (XT) between adjacent cores after cabling were firstly clarified. By introducing the trapezoid index and optimizing the cabling process, the maximum values of added XT of 1.17 dB/km due to 10 loops with a bending radius of 6 mm imposed over the 4-core SXC and a macro-bending loss of 0.37 dB/10 turns were, respectively, achieved.P Then, the optical transmission with low bit error rate (BER) was presented using a 100GBASE-LR4 transceiver over the 1.2 km long 4-core SXC. The excellent bending resistance of the 4-core SXC may pave the way for a reduction in space pressure and increase in access density on short-reach optical interconnect (OI) based on DSDM.