Showing papers on "Single-mode optical fiber published in 2019"

Relative humidity sensor based on hollow core fiber filled with GQDs-PVA

Abstract: A novel optic fiber Fabry-Perot interferometer (FPI) based on graphene quantum dots (GQDs) and Polyvinyl Alcohol (PVA) is first proposed for relative humidity (RH) sensing and experimentally demonstrated. The GQDs-PVA compounds are filled into the hollow core fiber (HCF), which is spliced at the end of a single mode fiber (SMF). The refractive index of GQDs-PVA compounds reduces and the length of the FP cavity elongates with the increase of RH, which will lead the reflective spectrum shift to length wavelength, and the variation can characterize the change of RH values. The humidity environment is generated by different saturated saline solution, and the RH values are calibrated by a moisture meter. Experiment results reveal that the wavelength shift shows good linearity with the RH changing from 13.47%RH to 81.34%RH, and the sensitivity is 117.25 pm/%RH with the linearity relevancy of 0.9983. In addition, reversibility and repeatability experiments are carried out and the mean square deviation of six sets of data is 1.425 × 10−3, which indicates good practical development prospects. Taking the practical application into account, the influence of hydrogen and nitrogen in the air on the sensor is studied before humidity experiment, and the experiment results shows that hydrogen and nitrogen in the air have a negligible effect on the humidity sensor proposed in this paper.

Single-mode, low loss hollow-core anti-resonant fiber designs.

Abstract: In this paper, we numerically investigate various hollow-core anti-resonant (HC-AR) fibers towards low propagation and bend loss with effectively single-mode operation in the telecommunications window. We demonstrate how the propagation loss and higher-order mode modal contents are strongly influenced by the geometrical structure and the number of the anti-resonant cladding tubes. We found that 5-tube nested HC-AR fiber has a wider anti-resonant band, lower loss, and larger higher-order mode extinction ratio than designs with 6 or more anti-resonant tubes. A loss ratio between the higher-order modes and fundamental mode, as high as 12,000, is obtained in a 5-tube nested HC-AR fiber. To the best of our knowledge, this is the largest higher-order mode extinction ratio demonstrated in a hollow-core fiber at 1.55 μm. In addition, we propose a modified 5-tube nested HC-AR fiber, with propagation loss below 1 dB/km from 1330 to 1660 nm. This fiber also has a small bend loss of ~15 dB/km for a bend radius of 1 cm.

The Engagement of Hybrid Ultra High Space Division Multiplexing with Maximum Time Division Multiplexing Techniques for High-Speed Single-Mode Fiber Cable Systems

Abstract: High-speed single-mode fiber-optic communication systems have been presented based on various hybrid multiplexing schemes. Refractive index step and silica-doped germanium percentage parameters are also preserved during their technological boundaries of attention. It is noticed that the connect design parameters suffer more nonlinearity with the number of connects. Two different propagation techniques have been used to investigate the transmitted data rates as a criterion to enhance system performance. The first technique is soliton propagation, where the control parameters lead to equilibrium between the pulse spreading due to dispersion and the pulse shrinking because of nonlinearity. The second technique is the MTDM technique where the parameters are adjusted to lead to minimum dispersion. Two cases are investigated: no dispersion cancellation and dispersion cancellation. The investigations are conducted over an enormous range of the set of control parameters. Thermal effects are considered through three basic quantities, namely the transmission data rates, the dispersion characteristics, and the spectral losses.

Tapered Fiber-Optic Mach-Zehnder Interferometer for Ultra-High Sensitivity Measurement of Refractive Index.

Abstract: A Mach-Zehnder interferometer (MZI) based fiberoptic refractive index (RI) sensor is constructed by uniformly tapering standard single mode fiber (SMF) for RI measurement. A custom flame-based tapering machine is used to fabricate microfiber MZI sensors directly from SMFs. The fabricated MZI device does not require any splicing of fibers and shows excellent RI sensitivity. The sensor with a cladding diameter of 35.5 µm and length of 20 mm exhibits RI sensitivity of 415 nm/RIU for RI range of 1.332 to 1.384, 1103 nm/RIU for RI range of 1.384 to 1.4204 and 4234 nm/RIU for RI range of 1.4204 to 1.4408, respectively. The sensor reveals a temperature sensitivity of 0.0097 nm/°C, which is relatively low in comparison to its ultra-high RI sensitivity. The proposed inexpensive and highly sensitive optical fiber RI sensors have numerous applications in chemical and biochemical sensing fields.

Controllable Growth of Aligned Monocrystalline CsPbBr3 Microwire Arrays for Piezoelectric-Induced Dynamic Modulation of Single-Mode Lasing.

Abstract: CsPbBr3 shows great potential in laser applications due to its superior optoelectronic characteristics. The growth of CsPbBr3 wire arrays with well-controlled sizes and locations is beneficial for cost-effective and largely scalable integration into on-chip devices. Besides, dynamic modulation of perovskite lasers is vital for practical applications. Here, monocrystalline CsPbBr3 microwire (MW) arrays with tunable widths, lengths, and locations are successfully synthesized. These MWs could serve as high-quality whispering-gallery-mode lasers with high quality factors (>1500), low thresholds ( 2 h). An increase of the width results in an increase of the laser quality and the resonant mode number. The dynamic modulation of lasing modes is achieved by a piezoelectric polarization-induced refractive index change. Single-mode lasing can be obtained by applying strain to CsPbBr3 MWs with widths between 2.3 and 3.5 µm, and the mode positions can be modulated dynamically up to ≈9 nm by changing the applied strain. Piezoelectric-induced dynamic modulation of single-mode lasing is convenient and repeatable. This method opens new horizons in understanding and utilizing the piezoelectric properties of lead halide perovskites in lasing applications and shows potential in other applications, such as on-chip strain sensing.

All-optical graphene-oxide humidity sensor based on a side-polished symmetrical twin-core fiber Michelson interferometer

Abstract: A high-sensitive graphene-oxide (GO) humidity sensor based on a side-polished twin-core fiber (SPTCF) Michelson interferometer (MI) has been demonstrated. The MI was fabricated by splicing a section of TCF to a standard single mode fiber (SMF) and tapering the splicing point. The exposed polished core has a stronger evanescent field and enhances the interaction between light and external environment. The GO-SPTCFMI can operate in the wavelength- and intensity- modulated sensor. The super-high humidity sensitivities of ˜2.72 nm/RH% in the RH range of 40–75% and ˜3.76 dB/RH% in the RH range of 60–62.1% are obtained experimentally. The high-performance GO-SPTCFMI is a promising candidate for potential applications, such as gas sensing and biochemical detection.

3.7 kW monolithic narrow linewidth single mode fiber laser through simultaneously suppressing nonlinear effects and mode instability

Abstract: In this paper, we report a 3.7 kW all fiber narrow linewidth single mode fiber laser. The full width at half-maximum is about 0.30 nm, and the beam quality is Mx2=1.358, My2=1.202 at maximum output power. The laser is achieved by simultaneously suppressing nonlinear effects and mode instability (MI). Different seeds are injected into the main amplifier to study stimulated Raman scattering (SRS) effect. The results show that the phase modulated single frequency seed is benefit to suppress the SRS effect. For the phase modulated single frequency seed, inserting a filter in preamplifier will suppress amplified spontaneous emission (ASE) and decrease the backward power. By optimizing the coiling of active fiber, the MI effect is suppressed.

Broadband continuous single-mode tuning of a short-cavity quantum-cascade VECSEL

Abstract: Changing the length of a laser cavity is a simple technique for continuously tuning the wavelength of a laser but is rarely used for broad fractional tuning, with a notable exception of the vertical-cavity surface-emitting laser (VCSEL)1,2. This is because, to avoid mode hopping, the cavity must be kept optically short to ensure a large free spectral range compared to the gain bandwidth of the amplifying material. Terahertz quantum-cascade lasers are ideal candidates for such a short cavity scheme as they demonstrate exceptional gain bandwidths (up to octave spanning)3 and can be integrated with broadband amplifying metasurfaces4. We present such a quantum-cascade metasurface-based vertical-external-cavity surface-emitting laser (VECSEL) that exhibits over 20% continuous fractional tuning of a single laser mode. Such tuning is possible because the metasurface has subwavelength thickness, which allows lasing on low-order Fabry–Perot cavity modes. Good beam quality and high output power are simultaneously obtained. Terahertz quantum-cascade lasers with over 20% continuous fractional tuning of a single laser mode are now possible thanks to metasurfaces.

Tunable single-mode bandpass filter based on metal–insulator–metal plasmonic coupled U-shaped cavities

Abstract: A compact plasmonic bandpass filter based on metal-insulator-metal plasmonic waveguides and a coupled U-shaped cavity is proposed in this study. Air and silver are used as insulator and metal materials and silver is characterised by the Drude model in the simulations. By tuning the height of the designed cavity, it is found that the resonance wavelength can be easily adjusted. Furthermore, the quality factor of the designed filter can be increased by increasing the cavity numbers. One, two or three cavities can be used to generate single-mode filters. Finally, by sweeping different structural parameters, the effect of them on transmittance spectrum is investigated. All results are obtained by the finite-difference time domain method. The proposed structure due to its remarkable properties such as being a single-mode filter, having a compact size, tunablity of the resonance frequency and its variable quality factor can be used in complex integrated optical structures such as demultiplexers and so on.

Silica optical fiber drawn from 3D printed preforms.

Abstract: Silica optical fiber was drawn from a three-dimensional printed preform. Both single mode and multimode fibers are reported. The results demonstrate additive manufacturing of glass optical fibers and its potential to disrupt traditional optical fiber fabrication. It opens up fiber designs for novel applications hitherto not possible.

Relative humidity sensor based on Vernier effect with GQDs-PVA un-fully filled in hollow core fiber

Abstract: A new relative humidity (RH) sensor based on two cascaded Fabry-Perot interferometers (FPIs) and Vernier effect is proposed and developed. The two cascade FPIs are constructed by splicing a section of photonic crystal fiber (PCF) between a section of single mode fiber and a section of hollow core fiber (HCF), where the length of PCF is 281.43μm and the length of HCF is 490.83μm. The hollow core fiber is un-fully filled with Graphene quantum dots and polyvinyl alcohol. By adjusting the filling time, FPIs with different free spectral ranges are got. We study the three sensors whose filling time are 5 min, 10 min and 15 min, respectively. Among them, the FPI with 15mins’ filling has the highest sensitivity, which is 0.456 nm/%RH with RH changing from 19.63%RH to 78.86%RH. In addition, the experimental results indicate it has good reversibility and stability. What’s more, the sensitivity is about 4.8 times higher than that of our previous work. In brief, the compact configuration, easy fabrication, high sensitivity and good RH resolution imply the proposed sensor has good potential for RH measurement application.

High-sensitivity strain sensor implemented by hybrid cascaded interferometers and the Vernier-effect

Abstract: A strain sensor implemented by cascading a Sagnac interferometer (SI) and a fiber modal interferometer (FMI) was proposed and experimentally demonstrated. The SI serving as the fixed part comprises a length of polarization maintaining fiber (PMF), and the FMI serving as the sliding part comprises single mode fiber (SMF) and a length of few mode fiber (FMF) with core-offset structure. By closing the free spectral ranges (FSRs) of the SI and FMI, Vernier-effect exists and makes contribution to magnify the sensitivity. Through monitoring the FSR of the spectral envelope, the strain sensing is realized. A high sensitivity of 65.71 pm/μe which is more than 20 times higher than that of the single FMI is obtained experimentally. Moreover, thanks to the polarization insensitivity of FMF, the proposed sensor is immune to environmental disturbance and suitable for physical sensing applications.

Design and Performance Analysis of the WDM Schemes for Radio over Fiber System With Different Fiber Propagation Losses

Abstract: The integration of optical and wireless networks increases mobility and capacity and decreases costs in access networks. Fibre optic communication can be considered optical communication that combines the methodologies of two communications, and it may be utilised in systems of wired and wireless communication. The solution for many problems is radio over fibre (RoF) because it can control many base stations (BS) that are connected to a central station (CS) with an optical fibre. The received RoF signal head for in a low quality; thus, many factors will result in some problems such as a high bit error rate (BER) and low Q-factor values, and the receiver might not be operating in a high data rate network. Wavelength division multiplexing (WDM) network can offer a solution to these problems where the transmission of different signals can be done with a single-mode fibre. BER should be reduced to assured values, and the Q-factor must be increased. The investigation of WDM-RoF with different lengths of fibre at various channel spacing will be simulated using Optisystem software, and the RoF’s receiver performance is measured and analyzed depending on the acquired BER, the value of the Q-factor, and the height of the opening of the eye diagram. The degradation factors effect such as attenuation and dispersion are significantly limited with the addition of an EDFA amplifier to a Single Mode Fibre (SMF).

Optical Fiber Humidity Sensor Based on Polyvinylidene Fluoride Fabry–Perot

Abstract: An optical fiber Fabry–Perot (FP) for relative humidity (RH) sensing is proposed. The FP cavity is fabricated by splicing a short length of hollow silica tube in a single mode fiber. The fiber is then coated with a polyvinylidene fluoride (PVDF) thin film to work as a mirror. The fabrication process of the FP interferometer with a dip coating process in a PVDF/dimethyl formamide solution is presented. The pattern fringes of the FP suffer a wavelength shift due to the change in the PVDF’s refractive index with the ambient RH variation. A short overview of the cavity’s formation and stability is presented. The RH response of the FPI cavity is tested. The sensor presented a sensitivity of 32.54 pm/%RH at constant temperature and −15.2 pm/°C for temperature variation.

Design of Multicore Fiber Having Upgradability From Standard Single-Mode Fibers and Its Application

Abstract: In this paper, multicore fiber (MCF), which is compatible with standard conventional single-mode fibers (SMFs), is summarized. Conventional SMF systems can be upgraded to space-division multiplexing systems by this MCF with migration scenario. As applications of this, connectivity of this MCF and MCF cable with ultra-high-capacity is described. Transmission experiment using 400 Gb/s signals are confirmed with this MCF.

Investigation of cladding thicknesses on silver SPR based side-polished optical fiber refractive-index sensor

Abstract: A single mode optical fiber modified using side-polishing method is applied as a sensor based on surface plasmon resonance (SPR) principles. The SPR sensor was designed using side-polished optical fiber of which the cladding was symmetrically removed and coated with different thicknesses of embedded silver film. The amount of cladding removed was based on the insertion power loss during the polishing process, where losses were recorded at 0.65 dB corresponding to 20 μm thickness of remaining cladding and 1.8 dB refers to no cladding respectively. Finite Difference Time Domain (FDTD) simulation was used to investigate the effects of this configuration. The system has been constructed using different refractive indices of liquid. Silver thin layer thickness of 40 nm found to be the most desirable after it display better sensitivity in sensing mechanism. The application of 40 nm-thick Ag has been also coated on the fiber with no cladding, which shows higher sensitivity of ∼2166 nm/refractive index unit (RIU) and 208.333 nm/refractive index unit (RIU) using distilled water (n = 1.333) and alcohol (n = 1.345), respectively. The SPR dip transmission wavelength was recorded as ∼460 nm and ∼530 nm for both fiber conditions at active sensing area as 3 mm length operating at wavelength range of 300–1100 nm. The system has the advantages of being low-cost and applicable in bio-sensors.

Fabry–Perot Curvature Sensor With Cavities Based on UV-Curable Resins: Design, Analysis, and Data Integration Approach

Abstract: This paper presents the development of a Fabry–Perot interferometer (FPI) for curvature sensing Ultraviolet (UV)-curable resins are used in the FPI cavity In this case, two configurations for the FPI curvature sensor are tested, one with the UV-curable resin in between two standard single mode fibers (SMFs), namely SMF-FPI configuration and the other using a SMF and a perfluorinated polymer optical fiber (POF) with the resin between them, referred as the POF-FPI configuration Analytical simulations were performed for both configurations in order to evaluate FPIs’ wavelength shift and power variation as function of the bending angle, where such analyses are, then, confirmed by the experimental results with higher sensitivity as function of the wavelength shift for the POF-FPI and, higher sensitivity of SMF-FPI for the optical power variation Thereafter, a data fusion for the FPI’s wavelength shift and optical power variation was proposed using the Kalman filter, where the angle response after the data fusion is compared with the ones using only wavelength shift or optical power variation for both FPI configurations The results show error decrease in all analyzed cases with up to sixfold reduction of the root mean squared error (RMSE)

A High Sensitivity Temperature Sensing Probe Based on Microfiber Fabry-Perot Interference

Abstract: In this paper, a miniature Fabry-Perot temperature probe was designed by using polydimethylsiloxane (PDMS) to encapsulate a microfiber in one cut of hollow core fiber (HCF). The microfiber tip and a common single mode fiber (SMF) end were used as the two reflectors of the Fabry-Perot interferometer. The temperature sensing performance was experimentally demonstrated with a sensitivity of 11.86 nm/°C and an excellent linear fitting in the range of 43-50 °C. This high sensitivity depends on the large thermal-expansion coefficient of PDMS. This temperature sensor can operate no higher than 200 °C limiting by the physicochemical properties of PDMS. The low cost, fast fabrication process, compact structure and outstanding resolution of less than 10-4 °C enable it being as a promising candidate for exploring the temperature monitor or controller with ultra-high sensitivity and precision.

Versatile and precise quantum state engineering by using nonlinear interferometers.

Abstract: The availability of photon states with well-defined temporal modes is crucial for photonic quantum technologies. Ever since the inception of generating photonic quantum states through pulse pumped spontaneous parametric processes, many exquisite efforts have been put on improving the modal purity of the photon states to achieve single-mode operation. However, because the nonlinear interaction and linear dispersion are often mixed in parametric processes, limited successes have been achieved so far only at some specific wavelengths with sophisticated design. In this paper, we resort to a different approach by exploiting an active filtering mechanism originated from interference fringe of nonlinear interferometer. The nonlinear interferometer is realized in a sequential array of nonlinear medium, with a gap in between made of a linear dispersive medium, in which the precise modal control is realized without influencing the phase matching of the parametric process. As a proof-of-principle demonstration of the capability, we present a photon pairs source using a two-stage nonlinear interferometer formed by two identical nonlinear fibers with a standard single mode fiber in between. The results show that spectrally correlated two-photon state via four wave mixing in a single piece nonlinear fiber is modified into factorable state and heralded single-photons with high modal purity and high heralding efficiency are achievable. This novel quantum interferometric method, which can improve the quality of the photon states in almost all the aspects such as modal purity, heralding efficiency, and flexibility in wavelength selection, is proved to be effective and easy to realize.

Space division multiplexing in standard multi-mode optical fibers based on speckle pattern classification

Abstract: In optical communications the transmission bandwidth of single mode optical fibers is almost fully exploited. To further increase the capacity of a telecommunication link, multiplexing techniques can be applied across 5 physical dimensions: amplitude, quadrature, polarization, frequency and space, with all but the latter being nearly exhausted. We experimentally demonstrate the feasibility of an original space division multiplexing technique based on the classification of speckle patterns measured at the fiber’s output. By coupling multiple optical signals into a standard multimode optical fiber, speckle patterns arise at the fiber’s end facet. This is due to quasi-random interference between the excited modes of propagation. We show how these patterns depend on the parameters of the optical signal beams and the fiber length. Classification of the speckle patterns allows the detection of the independent signals: we can detect the state (i.e. on or off ) of different beams that are multiplexed in the fiber. Our results show that the proposed space division multiplexing on standard multimode fibers is robust to mode-mixing and polarization scrambling effects.

Speckle-based strain sensing in multimode fiber.

Abstract: The diversity of spatial modes present within a multimode fiber has been exploited for a wide variety of imaging and sensing applications. Here, we show that this diversity of modes can also be used to perform quantitative strain sensing by measuring the amplitude of the Rayleigh backscattered speckle pattern in a multimode fiber. While most Rayleigh based fiber sensors use single mode fiber, multimode fiber has the potential to provide lower noise due to the higher capture fraction of Rayleigh scattered light, higher non-linear thresholds, and the ability to avoid signal fading by measuring many spatial modes simultaneously. Moreover, while amplitude measuring single mode fiber based Rayleigh sensors cannot provide quantitative strain information, the backscattered speckle pattern formed in a multimode fiber contains enough information to extract a linear strain response. Here, we show that by tracking the evolution of the backscattered speckle pattern, the sensor provides a linear strain response and is immune to signal fading. The sensor has a noise floor of 2.9 pɛ/√Hz, a dynamic range of 74 dB at 1 kHz, and bandwidth of 20 kHz. This work paves the way for a new class of fiber optic sensors with a simplified design and enhanced performance.

Four-wavelength-switchable SLM fiber laser with sub-kHz linewidth using superimposed high-birefringence FBG and dual-coupler ring based compound-cavity filter

Abstract: We propose and demonstrate a four-wavelength-switchable erbium-doped fiber laser (4WS-EDFL) with a four-channel superimposed high-birefringence fiber Bragg grating (SI-HBFBG) and a dual-coupler ring based compound-cavity (DCR-CC) filter. Both for the first time, a SI-HBFBG as a four-channel reflective filter is used in a multi-wavelength switchable fiber laser to define wavelength channels and a DCR-CC filter is used to select a single mode from dense longitudinal-modes in a fiber laser. We present in detail how to design, fabricate, and characterize the DCR-CC filter with both theoretical analysis and experimental results, which we believe is the first systematic approach for making a compound-cavity based filter used for selecting single-longitudinal mode (SLM) in a fiber laser. The enhanced polarization hole burning effect in a 2.9 m long erbium-doped fiber, coiled inside a three-loop polarization controller, and the polarization-mismatch-induced losses are introduced into the laser cavity to achieve wavelength-switching operations. We show that the 4WS-EDFL can be switched among fifteen lasing states, including four single-wavelength operations, six dual-wavelength operations, four three-wavelength operations and one four-wavelength operation, all with high stability. For demonstration, in switchable single-wavelength operations, the four SLM lasing outputs measured are all with an optical signal to noise ratio of >80 dB, a linewidth of <700 Hz, a relative intensity noise of ≤−156.7 dB/Hz at frequencies over 3 MHz, an output power fluctuation of ≤0.555 dB and excellent polarization characteristics.

Gelatin-Coated Michelson Interferometric Humidity Sensor Based on a Multicore Fiber With Helical Structure

Abstract: A Michelson interferometer with gelatin coated for relative humidity (RH) measurement is proposed and demonstrated. It is fabricated by connecting the lead in/out single mode fiber, multimode fiber, triangular four core fiber (FCF) in a certain order. A gold film is deposited on the end face of the FCF as a reflector. A helical structure is fabricated by twisting the FCF under continuous arc discharging. Gelatin is coated onto the whole sensor to sense RH changes. When the RH of the external environment changes, both the refractive index (RI) and the size of the gelatin film changes, so the effective RI of the FCF cladding and the strain of the sensor changes accordingly, resulting in the resonance dip wavelength change in the interference signal. Such a probe is applied for RH measurement with a sensitivity of about –0.185 nm/%RH in the range from 45.0%RH to 81.7%RH with the response/recovery time of approximately 5.24/7.14 s, respectively.