We study the communication capabilities of a bi-directional real-time communication system that employs superconducting nanowire single-photon detectors (SNSPDs) under ultra low received optical power conditions. Furthermore, we analyze the influence of received optical power jitter on the system’s communication performance. To accomplish this, we construct a bi-directional real-time fiber optic communication system based on SNSPDs using the pulse position modulation. We successfully achieve bi-directional real-time video communication even under very low received optical power conditions, maintaining an average received optical power level of −75 dBm. The bit error rates for the uplink and downlink are measured at 2.56×10−5 and 3.08×10−5, respectively. Additionally, our investigation reveals that the SNSPD can tolerate a jitter range of up to 5 dB in received optical power while ensuring uninterrupted communication. This paper delves into the practical engineering application of a high-sensitivity optical communication system based on SNSPDs, offering novel insights for optimizing their future use in free space optical communication systems.
We propose and experimentally demonstrate an in-line microfluidic sensor based on a dual S-taper multimode fiber interferometer (MFI) for glucose sensing. The dual S-taper MFI was fabricated by splicing two S-shaped fiber tapers with a commercially available fusion splicer. To realize in-line microfluidic sensing, the sensor was encapsulated into a capillary with the inlet and outlet to pump in and out the glucose sample solution using a syringe. Fourier frequency spectra of the transmission spectra under air and deionized water environments showed that multiple high-order modes simultaneously participated in the modal interference process. Experimental results indicated that the interference dip wavelength sensitivity reached 0.276 nm / ( g / dL ) for the glucose concentration ranging from 0 to 25.0 g / dL. Our proposed glucose sensor has several advantages such as a compact structure, ease of fabrication, and low cost, which make it a promising candidate for in-line glucose sensing and other microfluidic sensing applications.
In this letter, we proposed a self-temperature-compensation approach for fiber specklegram sensor (FSS) based on polarization specklegram analysis. The temperature compensation is achieved by comparing the variation difference of the two specklegrams with vertical linear polarization state. We designed a fiber specklegram magnetic field sensor employing this method and the magneto-birefringence effect of magnetic fluid. The measurement of magnetic field with high stability and good repeatability has been successfully achieved, which demonstrated the effectiveness of the proposed method. Due to the merits of low cost, ease of implement and system simplicity, the proposed method can promote the practical use of the FSS in long term monitoring.
We propose and numerically design a magnetically tuned orbital angular momentum (OAM) generator operating in the terahertz (THz) regime based on air-clad microstructured optical fibers (ACMOFs) infiltrated with functionalized liquid crystals (LCs). The ACMOFs consist of a ring-like air hole layer uniformly arranged the outer surface, serving as both the whispering gallery mode (WGM) microcavity and angular grating. Numerical simulations indicate that due to the periodic refractive index modulation in azimuthal direction through filling LCs by every other air hole, WGMs would be coupled into specific OAMs, whose operation frequency and topological charges could be tuned by adjusting the refractive index of LCs that through applying external magnetic field. The proposed magnetically tunable ACMOF-based THz OAM generator possesses several desirable merits such as compatibility with functional materials, ease of integration, and flexible structure, which is anticipated to find potential applications in future OAM-based THz communication systems.
We propose an all-fiber electric field sensor using a U-bent single-mode fiber integrated with liquid crystal. The sensing mechanism is based on the interference between whispering-gallery modes and core mode in U-shaped bent fibers. We have experimentally investigated the influences of applied electric voltage as well as polarization state of the incident light on the transmission spectral characteristics of the proposed electric field sensor. The experimental results indicate that the transmission spectra are highly sensitive to the applied voltage and the highest sensitivity reaches 20.4221 nm/kV. The dip wavelengths and transmission loss at transmission dip exhibit a periodic variation behavior in response to the light polarization state rotation by 360 deg, which is in agreement with our theoretical analysis.
In this paper, we have demonstrated a magnetic field sensor based on the fiber taper coupler coated with Magnetic fluid. The proposed sensor is fabricated by immersing a fiber taper coupler into the Magnetic fluid and then sealing it with the paraffin. The sensor exhibits high response as a function of the magnetic field with sensitivities of 0.154 nm/Oe with measurement range from 50 Oe to 200 Oe and -0.06301 dB/ Oe from 75 Oe to 200 Oe. Owing to the advantages of high sensitivity, small footprint, and ease of fabrication, the proposed sensor would find potential applications in magnetic field sensing field.
A compact fiber-optic magnetic-field sensor based on tapered all-solid waveguide-array fiber (WAF) and magnetic fluid (MF) has been proposed and experimentally demonstrated. The transmission spectra of the fiber-optic magnetic field sensor have been measured and analyzed under different magnetic field intensities. Experimental results show that the acquired magnetic field sensitivity is 44.57 pm/Oe for a linear magnetic field intensity range from 50 Oe to 200 Oe. It also indicates that the magnetic field sensor based on tapered all-solid WAF and MF is helpful to reduce temperature cross-sensitivity for the measurement of magnetic field.
An ultrasensitive optical fiber twist sensor is proposed by employing a Sagnac interferometer based on polarization-maintaining elliptical core fibers (PM-ECFs). The twist effects are theoretically analyzed and experimentally demonstrated. Based on the photoelastic effect, the wavelength shift in response to twist rate turns out linear tendency and is torsion-direction-dependent. The maximum torsion sensitivity reaches 18.59593nm/(rad/m) (or 0.67582nm/°) for clockwise (CW) torsion direction and 15.83073nm/(rad/m) for anticlockwise (ACW) torsion direction, respectively. Furthermore, it is further improved up to 1.675 nm/° by rotating two ends of PM-ECF simultaneously. The prominent advantage of ultrasensitivity keep it meritorious in the applications of spaceflight and constructional engineering.
A magnetic-field-tuned photonics device based on magnetic fluid (MF) and a square tapered no-core fiber (NCF) sandwiched between two single-mode fibers (SMFs) has been proposed. The enhanced evanescent field effect in the NCF is achieved by tapering the square NCF utilizing a fusion splicer. The spectral dependence of the proposed device on the applied magnetic-field intensity has been investigated. The results indicate that a maximal sensitivity of -18.7pm/Oe is obtained for a magnetic field strength ranging from 25Oe to 450Oe. The proposed tunable device has several advantages, including low cost, ease of fabrication, compact structure, and high sensitivity.
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