Plastic optical fiber refractometer for continuous refractive index measurement

This paper investigated the continuous measurement of a refractive index(RI)sensor based on macrobending microoptical plastic fiber(m-POF).The sensing properties of the RI sensor depend on the structure parameter,which is the ratio of macrobending radius of m-POF to the radius of fiber itself.The ratio changes with the measurement time increasing because of the water absorption,which introduces an maximum measurement deviation of 7.3×10^(-5) RIU when the immersion time exceeds 40 h.This work indicates that for the sensors based on POF,the measurement time must be taken into consideration for continuous measurement.

Research on Radiation Characteristics of Polymeric Plastic Fiber

The anti-radiation mechanism of polymeric plastic fiber is analyzed. The radiation characteristic of this type fiber is studied. Our experimental results indicate that under the low radiation dosage (below 1 kGy) the plastic optical fiber’s transmission rate rises instead of descends while this type of fiber is radiated by γ ray, electron beam and proton beam respectively. After a period of time, it gradually reaches a constant value. But under the high radiation dosage (above 1 kGy) the fiber’s transmission rate descends after radiation. Later, it gradually goes up to a constant value.

Long Period Grating Imprinted on a Flat-Shaped Plastic Optical Fiber for Refractive Index Sensing

A corrugated surface long period grating(LPG)was fabricated on a flat-shaped plastic optical fiber(POF)as a refractive index(RI)sensor by a simple pressing with the heat pressure and mechanical die press print method.The light propagation characteristics of an LPG imprinted on a multi-mode POF were analyzed by the method of geometrical optics.Theoretical and experimental results showed that the structural parameters of the sensor affected the RI sensing performance,and the sensor with a thinner flat thickness,a deeper groove depth of the corrugated surface LPG,and a longer LPG exhibited better RI sensing performance.When the POF with a diameter of 1 mm was pressed with the heat pressure to a flat shape with a thickness of 600μm,an LPG with a period of 300μm,a groove depth of 200μm,and a length of 6 cm was fabricated on it,and the RI sensitivity of 1447%/RIU was obtained with a resolution of 5.494×10^(−6) RIU.In addition,the influences of the POF cladding,tilting of LPG,and bending of the sensing structure were investigated.The results demonstrated that after removing the cladding and tilting or bending the LPG,the RI sensing performance was improved.When the LPG imprinted on the flat-shaped POF was bent with a curvature radius of 6/πcm,the highest sensitivity of 6563%/RIU was achieved with a resolution of 2.487×10^(−9) RIU in the RI range of 1.3330–1.4230.The proposed sensor is a low-cost solution for RI measurement with the features of easy fabrication,high sensitivity,and intensity modulation at the visible wavelengths.

Evanescent Wave Absorption Sensor Based Tapered Plastic Optical Fiber Coated with Monolayer Graphene for Ethanol Molecules Detection

An evanescent wave absorption （EWA） sensor based tapered plastic optical fiber （TPOF） coated with monolayer graphene film for ethanol molecules detection is demonstrated in this study. The continuous and monolayer graphene films were grown on a Cu foil by using chemical vapor deposition （CVD） technology. Polymethyl methacrylate （PMMA） was used as the carrier to support the transfer of graphene from Cu foil to the skinless tapered optical fiber core. The accuracy of the TPOF sensor with graphene （G-TPOF sensor） is much higher than that without gra- phene （TPOF sensor）, which can be attributed to the molecules enriched on the surface of graphene. The absorbance （A） and the concentrations of ethanol solution show an excellent proportional relationship in a range of 0--100%. The dynamic response of the G-TPOF sensor has shown strong reversibility, repeatability and stability at room temperature. The response time and recovery time of the G-TPOF sensor for different concentrations are all less than 30 s. Beyond that, we selected the Chinese liquor as the analyte, and the results are consistent with the concen- tration-list obtained in the experiment.

Side-polished SMS based RI sensor employing macro-bending perfluorinated POF

A refractive index(RI)sensor based on perfluorinated plastic optical fiber(PF-POF)is introduced in this paper.The PF-POF as multi-mode fiber was side-polished(SP)to form a macro-bending single-mode-multimode-single-mode(SMS)structure.Both ends of the sensor were closely connected to single-mode quartz optical fiber(SMF).The spectral char-acteristics of the sensor are measured,analyzed and discussed.The results show that when the length of PF-POF is 8 cm,the macro-bending radius is 3 cm,and the SP-depth is 20μm.The intensity sensitivity reaches−219.504 dBm/RIU in the range of RI=1.330~1.356.A reference is provided for the application of PF-POF in RI sensor in the future.The sensor is featured with low-cost,good flexibility and high efficiency.

Refractive index sensor based on a step index multimode polymer optical fiber with a micro-hole created by a miniature numerical control machine

A compact in-fiber refractive index （RI） sensor based on a step index multimode polymer optical fiber with a micro-hole drilled by a miniature numerical control machine is presented. A good linear relationship between the transmission and RI over a large operating range from 1.335 to 1.475 and a sensitivity of 36 071.43 mV/RIU （RI unit） are found. The relationship between the transmission and the RI of the hole depends on the micro-hole＇s diameter and depth. The RI sensor developed in this letter is low-cost, easily fabricated, and capable of continuous measurement.

Liquid refractive index sensor based on polymer fiber with micro-holes created by femtosecond laser

We present a liquid refractive index （RI） sensor based on step-index multimode polymer optical fiber with a micro-hole drilled by the femtosecond laser. The experimental results show that in the RI operation range of 1.333-1.473, the sensor has a good linear loss （dB） response to the liquid RI in the micro-holes and a high sensitivity of 18 dB/RIU approximately. The experimental results are explained with the mode of the refrac- tion loss caused by the hole core interface and connection loss caused by the gap of the holes. The sensor has many advantages including high sensitivity and low cost.