We have proposed and experimentally demonstrated a novel optical fiber sensor for simultaneous measurement of high temperature and gas pressure based on a Regenerated Fiber Bragg grating (RFBG) cascaded with a homemade hollow core Bragg fiber (HCBF). The HCBF functions as an anti-resonant reflecting waveguide and acts as a pressure and temperature sensing unit. The sample was fabricated and tested in our lab, exhibiting a high linear pressure and temperature sensitivity of −3.747 nm/MPa and 25.925 pm/°C in a large-dynamic range of 2 MPa and 600 °C, respectively. The RFBG, as a temperature monitor, was integrated to compensate the temperature cross-correspondence of the HCBF. By utilizing a 2 × 2 matrix obtained with the experimental results, simultaneous measurement of temperature and gas pressure can be achieved. Besides, compact size, low cost and high sensitivity make the sensor more competitive in harsh environment application.

In the article, a novel reflective all-fiber integrated sensor for simultaneous gas pressure and temperature sensing has been proposed and demonstrated in experiment. The proposed sensor is fabricated by combining seven core fibers (SCFs), a twin-hole and dual-core fiber (THDCF), a single-mode fiber (SMF) extrinsic Fabry-Perot interferometer (FPI) and a fiber Bragg grating (FBG). The FPI section and FBG section act as a pressure and temperature sensing unit. Especially, the MZI has the effect of filtering the FPI spectrum and is more conducive to the demodulation of the FPI reflected signal. In FPI section, the two SMFs connects with a hollow core capillary (HCC) by the ultraviolet (UV) curing glue. The sensor exhibits a high pressure and temperature sensitivity of 13.10 nm/MPa and 0.20 nm/°C in the range of 0.1-1.2 MPa and 30-90 °C, respectively. The FBG works as a temperature sensor without pressure responding, is fabricated by using the UV laser-based phase mask technology in our lab. By utilizing the dual-wavelength matrix method, both gas pressure and temperature can be measured simultaneously. In sum, with the advantage of compact size, easy fabricated, low cost, high sensitivity, reflection-type and the ability of multi-parameter measurement, our sensor is more competitive in harsh environments.

A novel hollow-core anti-resonant fiber (HC-ARF) with glass-sheet conjoined nested tubes that supports five core modes of LP01-LP31 with low mode couplings, large differential group delays (DGDs), and low bending losses (BLs) is proposed. A novel cladding structure with glass-sheet conjoined nested tubes (CNT) is induced for the proposed HC-ARF which can suppress mode couplings between the LP01-LP31 modes and the cladding modes. The higher-order modes (HOMs) which are LP11-LP31 modes also have very low loss by optimizing the radius of the nested tube and the core radius. Moreover, the large effective refractive index differences Δn_eff between HOMs are all larger than 1 × 10⁻⁴ which contributes to a large DGD in the wavelength range from 1.3 to 1.7 µm. The bending loss of the HC-ARF is analyzed and optimized emphatically. Our calculation results show that bending losses of LP01-LP31 modes are all lower than 3.0 × 10⁻⁴ dB/m in the wavelength range from 1.4 to 1.61 µm even when the fiber bending radius of the HC-ARF is 6 cm.

Respiratory rate (RR) monitoring has received widespread attention in medical field. Complex, expensive, and bulky commercial equipment limits the monitoring cost. To take full advantage of lab-on-fiber technologies, we present a novel, compact size lab-on-fiber breathing monitoring sensor based on a tapered no-core fiber (NCF) structure. The sensor is composed of humidity-sensitive polymer materials, single-mode fiber (SMF)–NCF-SMF structure, and monitors human RR by measuring exhaled humidity. The theoretical results prove that the self-imaging phenomenon can be induced by the changing of NCF diameter. The static relative humidity test results show a maximum relative humidity sensitivity of 0.0438 nm/%RH in the range of 35%RH–58%RH. Through the single-wavelength intensity fluctuation experiment, human respiratory information is collected. In the breathing process, a response time of 0.67 s can be achieved. The RR monitoring under different heart rates, breathing patterns, and human postures displays real-time tracking and high repeatability. Moreover, the compact size, low cost, and high sensitivity make our lab-on-fiber sensor more competitive in the field of medical treatment and our daily life.