Photonic Crystal Fiber Sagnac Interferometer Research Articles

High sensitivity trace carbon monoxide gas sensor based on endlessly single-mode photonic crystal fiber Sagnac interferometer

Abstract In this paper, a novel carbon monoxide (CO) gas sensor based on α-Fe2O3/MgO is presented and constructed. The endlessly single-mode photonic-crystal fibers (ESPCF) was sandwiched between the four-core fibers (FCF) to form the ESPCF-FCF-ESPCF structure, which was embedded it in the Sagnac loop to construct the Sagnac interferometer. The crystal structure, composition and morphology of α-Fe2O3/MgO sensing film were characterized by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM), respectively. The results indicated that the α-Fe2O3/MgO sensing film was uniformly coated on the outside surface of two ESPCFs, with a thickness of about 1 μm. When these sensing films adsorbed CO, the monitoring wavelength showed blueshift and the maximum sensitivity was 99.42 pm/ppm. The response time and recovery time were respectively 90 s and 100 s respectively. The Sagnac fiber-optic sensor exhibt high sensitivity, good selectivity and strong stability, and it can effectively realize the monitoring of carbon monoxide.

Sensing characteristics of photonic crystal fiber Sagnac interferometer based on novel birefringence and Vernier effect

In this paper, the sensing characteristics of a photonic crystal fiber (PCF) Sagnac interferometer based on flat-phase birefringence, zero-group birefringence and the Vernier effect have been studied. The temperature-sensitive liquid is filled into the air holes of the PCF. We realize flat-phase birefringence, by which the sensitivity can reach 4.9 nm/°C and 3.5 nm/°C. We find a new phenomenon in that there are more interference fringes appearing near the zero-group-birefringence wavelength with the environment changing. Highly sensitive sensors with −19.9 nm/°C and 28.6 nm/°C are obtained. We also demonstrate that two cascaded Sagnac interferometers based on PCF can realize the Vernier effect. The sensitivities are 1 nm/°C (single Sagnac interferometer) and 10.4 nm/°C (cascaded Sagnac interferometers), and the sensitivity is improved by more than 10 times. The sensitivity is inversely proportional to the difference between free spectral range (FSR)1 and FSR2, and the highest sensitivity reaches 23.2 nm/°C (−58 500 nm/RIU, resolution: 3.419× 10−7 RIU) by optimizing the PCF length in Sagnac interferometer 2. The average sensitivity based on two cascaded PCF Sagnac interferometers is up to −309 957 nm/RIU and the resolution is 6.453× 10−8 RIU as the refractive index of the analyte varies from 1.33 to 1.331, which is very competitive in the field of chemical sensing.

Refractive index sensor of a photonic crystal fiber Sagnac interferometer based on variable polarization states

Micron-sized holes distributed in the cross section of photonic crystal fibers allow the integration of the microfluidic analyte and fiber which makes it possible for rapid and effective chemical analysis. The innovation of this paper is that the polarization states of the fiber modes vary with the wavelength. The polarization directions of the two polarized modes are nearly 45 degrees with the horizontal direction at a certain wavelength, then the resonance wavelength will appear by a fiber Sagnac interferometer. The average sensitivity is up to −19040 nm/RIU as the refractive index of the microfluidic analyte varies from 1.33 to 1.37.

Selectively toluene-filled photonic crystal fiber Sagnac interferometer with high sensitivity for temperature sensing applications

Abstract In this paper, we theoretically and numerically investigate toluene-filled polarization maintaining photonic crystal fibers (PMPCFs) for temperature sensing application via Sagnac interferometer. We designed a PMPCF with a birefringence of 8.68 × 10−5, a relative birefringence sensitivity of 26% for 5 °C variation and sensitivity of −11 nm/°C around 25 °C. We study the effects of hole dimensions and fabrication imperfections on the performance of the proposed PMPCF and demonstrate that the PMPCF has a good toleration to any geometrical induced imperfections in the fabrication process of the fiber. Furthermore, we show that the spectral range of the sensor can be easily improved (to values larger than 137 nm) by decreasing the infiltration length of the PMPCF.

A high-sensitivity temperature sensor based on Sagnac interferometer employing photonic crystal fiber fully filled with ethanol

A high-sensitivity temperature sensor based on photonic crystal fiber Sagnac interferometer is proposed and studied. All holes of the PCF are filled with ethanol with capillarity. The cladding air holes are uniform arrangements. The two air holes around the core are removed to form new core modes with high birefringence. The sensitivities of the temperature can be up to −8.7657 and 16.8142 nm/ $$^{\circ }$$ C when temperature rises from 45 to 75 $$^{\circ }$$ C and the fiber length is 5.05 cm. And when temperature rises from 10 to 45 $$^{\circ }$$ C, the sensitivity can reach −7.848 and 16.655 nm/ $$^{\circ }$$ C with fiber length 2.11 cm. The performance of the selective-filled and the fully-filled PCF with temperature from 45 to 75 $$^{\circ }$$ C and fiber length 5.05 cm are analyzed and compared. The fully filling can better achieve PCF’s sensing performance. The simple structure and high sensitivities make the temperature sensor easy to achieve. The temperature sensor with high sensitivities and good linearity has great application value for environmental temperature detecting.

Sensing characteristics of a MF-filled photonic crystal fiber Sagnac interferometer for magnetic field detecting

A highly sensitive magnetic field sensor based on Sagnac interferometer consisted of a polarization maintaining photonic crystal fiber (PCF) filled with magnetic fluid (MF) is proposed and demonstrated. The refractive index of MF is sensitive to magnetic field H and the fiber Sagnac interferometer is sensitive to refractive index, so the sensing structure of our magnetic field sensor is designed. The water-based nanoparticles Fe3O4 is used which possesses low refractive index. The refractive index of MF follows the Langevin function and changes linearly with magnetic field H in our considerable magnetic field region. The parameters of λ, B(λ, H) on the influences of sensitivity are analyzed. We find a new phenomenon the two dip wavelengths shift in the opposite direction as magnetic field increases. The phenomenon is explained by group birefringence Bg which decreases and its sign changes as magnetic field increases. The sensitivity increases infinitely near the special wavelength related with zero-point Bg. The average sensitivities are 384pm/Oe (51,569nm/RIU), −430pm/Oe (−57,747nm/RIU) which turn out pretty well and the R-squares are 0.98113, 0.98415 respectively for the detected range 410–600Oe.

In-line microfluidic refractometer based on C-shaped fiber assisted photonic crystal fiber Sagnac interferometer

We propose and demonstrate a highly sensitive in-line photonic crystal fiber (PCF) microfluidic refractometer. Ultrathin C-shaped fibers are spliced in-between the PCF and standard single-mode fibers. The C-shaped fibers provide openings for liquid to flow in and out of the PCF. Based on a Sagnac interferometer, the refractive index (RI) response of the device is investigated theoretically and experimentally. A high sensitivity of 6621 nm/RIU for liquid RI from 1.330 to 1.333 is achieved in the experiment, which agrees well with the theoretical analysis.

Unique characteristics of a selective-filling photonic crystal fiber Sagnac interferometer and its application as high sensitivity sensor

We demonstrate a Sagnac interferometer (SI) based on a selective-filling photonic crystal fiber (SF-PCF), which is achieved by infiltrating a liquid with higher refractive index than background silica into two adjacent air holes of the innermost layer. The SF-PCF guides light by both index-guiding and bandgap-guiding. The modal birefringence of the SF-PCF is decidedly dependent on wavelength, and the modal group birefringence has zero value at a certain wavelength. We also theoretically and experimentally investigate in detail the transmission and temperature characteristics of the SI. Results reveal that the temperature sensitivity of the interference spectrum is also acutely dependent on wavelength and temperature, and an ultrahigh even theoretically infinite sensitivity can be achieved at a certain temperature by choosing proper fiber length. An ultrahigh sensitivity with -26.0 nm/°C (63,882 nm/RIU) at 50.0 °C is experimentally achieved.

Multiwavelength fiber ring laser based on optical add-drop multiplexers and a photonic crystal fiber Sagnac interferometer

In this paper, a configuration for a tunable multiwavelength erbium doped fiber ring laser based on optical add-drop multiplexers and a highly birefringent photonic crystal fiber Sagnac interferometer is proposed. Four different laser lines were obtained simultaneously all with an optical signal to noise ratio higher than 65dB, the best to our knowledge when using photonic crystal fibers. This proposed configuration is based on commercial devices and is adapted to the ITU channel's normative.

Temperature Sensor by Using Selectively Filled Photonic Crystal Fiber Sagnac Interferometer

In this paper, we report an optical fiber Sagnac interferometer (OFSI)-based temperature sensor constructed by a selectively filled polarization-maintaining photonic crystal fiber (PM-PCF). The transmission spectrum of the OFSI is in sinusoidal form and is sensitive to temperature. Simulation results predicted a higher sensitivity by selective filling than nonselective filling. In experiments, we used an extremely low-cost process to realize the selective filling. A sensitivity of 2.58 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{nm}/^{\circ}\hbox{C}$</tex> </formula> was achieved with an 11.7-cm-long PM-PCF. The sensitivity dependence on the infiltration length ratio was also investigated.