Single-mode Photonic Crystal Fiber Research Articles

Simultaneous Measurement of Electric Field and Strain With a Tandem-Interferometric Device

A novel, highly sensitive dual-parameter sensor based on tandem-interferometric arrangement of Fabry–Perot interferometer and Mach–Zehnder interferometer (MZI) has been designed and implemented in this paper. The sensor is composed of a single-mode fiber (SMF), hollow-core fiber, no-core fiber (NCF), and photonic crystal fiber (PCF). Those can simultaneously form a Fabry–Perot interferometer and a MZI. The both interferometers are able to measure strain. Meanwhile, the PCF was filled with liquid crystal to measure electric field intensity. Hence, simultaneous measurement of electric field and strain can be achieved. The sensitivities of electric field and strain can reach up to 10.5 nm/(kV/mm) and 1.25 pm/ $\mu \varepsilon $ , respectively.

Design of a single‐mode photonic crystal fibre with ultra‐low material loss and large effective mode area in THz regime

A novel low-loss photonic crystal fibre (PCF) has been suggested for THz spectral applications. The proposed PCF contains five layers cladding with three layers core. The cladding and core region of the fibre are arranged in the octagonal and porous manner, respectively, where both the core and cladding vicinity are constituted by circular air cavities. The optical properties of the PCF are investigated by utilising the full vectorial finite-element method along with the perfect match layers boundary condition. All numerical outcomes show the ultra-low effective material loss of 0.049 cm−1 and large effective area of 3 × 10−7 m2 at 1 THz operating frequency. The power fraction is also considered as another significant parameter to design a low loss fibre. The almost more than half of the useful power (about 53.78% at f = 1 THz) goes through the core over the wider operating frequency. In addition this, the proposed single-mode PCF can be fabricated using the sol–gel method and is useful not only for high data traffic transmission applications but also for THz waveguide applications.

Dispersion Engineering in Single-Polarization Single-Mode Photonic Crystal Fibers for a Nearly Zero Flattened Profile

We propose a systematic solution to the problem on dispersion engineering in single-polarization single-mode (SPSM) photonic crystal fibers (PCFs) for a nearly zero flattened profile. Based on dispersion-approximating and -normalizing methods as well as a clever engineering strategy, we have succeeded in a design of SPSM PCF with nearly zero flattened dispersion ${\text{0.82}}\pm {\text{0.30}}\,\text{ps}/\text{nm}/\text{km}$ over a broad band of ${\text{1.12}}\sim {\text{1.51}}\,\mu{\text{m}}$ . Moreover, such a fiber presents a very low confinement-loss level, which is less than 0.001 dB/km over the operation band.

An investigative study of efficient coupling mechanism of a hemispherical microlens tipped single mode photonic crystal fiber to a laser diode by ABCD matrix formulation and determination of the optimal separation distance

Photonic crystal fibers capable to operate endlessly in single moded regime offer varied and novel applications of practical interests. Hence, appropriate coupling with an optical source, working at wavelengths of well known significance is required for the effective functioning of these fibers. We present here an optical coupling scheme of such a single mode photonic crystal fiber with a laser diode through easily fabricable hemispherical microlens using ABCD matrix formulation. We, also, report the best distance of separation of the laser diode from photonic crystal fiber producing the maximum coupling. Our result should find wide use by system designers and engineers to appropriately calibrate photonic crystal fibers based on our formulation devoid of complexity of the deeply involved numerical method.

Surface plasmon resonance biosensor based on gold-coated side-polished hexagonal structure photonic crystal fiber.

The refractive index sensing characteristics of the side-polished photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor are detailed investigated in this paper. We used the finite element method (FEM) to study the influences of the side-polished depth, air hole size, lattice constant, and the refractive index (RI) of the PCF material on sensing performance. The simulation results show that the side-polished depth, air hole size, lattice pitch have significant influence on the coupling strength between core mode and surface plasmon polaritons (SPPs), but have little influence on sensitivity; the coupling strength and sensitivity will significant increase with the decrease of RI of the PCF material. The sensitivity of the D-shaped PCF sensor is obtained to be as high as 21700 nm/RIU in the refractive index environment of 1.33-1.34, when the RI of the PCF material is controlled at 1.36. It revealed a new method of making ultra-high sensitivity SPR fiber sensor. Then we experimental demonstrated a SPR refractive sensor based on the side-polished single mode PCF and investigated the sensing performance. The experimental results of the plasmon resonance wavelength sensitivity agree well with the theoretical results. The presented gold-coated D-shaped PCF SPR sensor could be used as a simple, cost-effective, high sensitivity device in bio-chemical detection.

Ultrahigh birefringence, ultralow material loss porous core single-mode fiber for terahertz wave guidance.

In this paper, a novel polarization-maintaining single-mode photonic crystal fiber (PCF) has been suggested for terahertz (THz) transmission applications. The reported PCF has five layers of hexagonal cladding with two layers of porous core. The cladding and core territory of the PCF are constituted by circular and elliptical air cavities, accordingly acting as a dielectric medium. Different geometrical parameters of the proposed PCF including pitches and diameters of circular air holes with the major and minor axes of elliptical air cavities being varied with the optimized structure. Various effects on the proposed PCF such as eccentricity and porosity effects are also carefully investigated. The numerical process is investigated by one of the most popular methods, the finite element method (FEM). All numerical computational results have revealed the ultrahigh birefringence in the order of 1.19×10-02 as well as the ultralow bulk absorption material loss of 0.0689 cm-1 at the 1 THz activation frequency. Besides, the V-parameter is also investigated for checking the proposed fiber modality. The proposed single-mode porous core hexagonal PCF is expected to be useful for convenient broadband transmission and numerous applications in the areas of THz technology.

Design and analysis of broadband single-mode photonic crystal fiber for transmission windows of the telecom wavelengths

To analyse the convenient use of photonic crystal fiber in the communication windows, a broadband single-mode photonic crystal fiber is proposed based on index-matching resonant coupling by using the full vector finite-element method. The novel microstructured design has been achieved for a wavelength range of 1.3μm–1.6μm. Thus it provides a wide operational bandwidth of 300nm. This bandwidth covers all the transmission windows of fiber-optic communication except that of ‘first window’. The higher order mode resonant coupling losses of the proposed fiber are good enough within this wavelength range to maintain the single mode operation. The mode field area for the proposed fiber in straight and as well as bent state is enough such that the fiber can reduce the optical intensities, which makes the fiber to be useful in high power fiber lasers and the amplifier applications. The proposed fiber exhibits a very small fundamental mode loss below 10−3dB/m both in the straight and bent state. Moreover, the broadband design which covers the most widely used second and third communication windows of wavelengths around 1310nm and 1550nm respectively, will draw the attention of the manufacturer in the fiber optic communication.

A novel ultra-broadband single polarization single mode photonic crystal fiber

The concept of employing a central hole infiltrated with nematic liquid crystal (NLC) and two additional air holes in the core region is exploited to obtain an ultra-broadband single polarization single mode photonic crystal fiber (SPSM-PCF). The effects of structural parameters on the SPSM operation are studied using the full-vectorial finite element method. Numerical results show that the proposed structure can attain the SPSM operation bandwidth of 1610nm (from 1.51 to 3.12µm) with confinement loss lower than 0.01dB/km. The SPSM operation range can also be widely tuned to shorter wavelengths by adjusting the structure parameters. And meanwhile, a broad dispersion-flattened SPSM PCF is also obtained around the communication wavelength. Moreover, the dual-core SPSM PCF has also been investigated, enabling potential applications in the wavelength splitter of 1.31 and 1.55µm bands at a short fiber length of 1.629mm with SPSM operation.

Ultra-high negative dispersion compensating square lattice based single mode photonic crystal fiber with high nonlinearity

This paper presents dispersion tailoring of photonic crystal fibers creating artificial defect along one of the regular square axes. A finite element method (FEM) has been enforced for numerical investigation of several guiding properties of the PCF covering a broad wavelength range about 1340–1640 nm over the telecommunication windows. According to simulation, the proposed PCF has obtained a strictly single-mode fiber, which has an ultra-high negative dispersion of about −584.60 to −2337.60 ps/(nm-km) and also possible to cover the highest nonlinearity order of 131.91 W−1 km−1 under the operating wavelength. Moreover, the proposed PCF structure experimentally focuses on higher nonlinear coefficient, which successfully compensates the chromatic dispersion of standard single mode in entire band of interest and greatly applicable to the optical transmission system. Additionally, the single mode behavior of S-PCF is explicated by employing V parameter. In our dispersion sensitive analysis, this fiber is significantly more robust due to successfully achieve ultra-high negative dispersion, which gains more promiscuous compared to the prior best results.

Determination of magnetic field using a Fabry–Perot cavity containing novel nanoparticles

ABSTRACTMn0.75Zn0.25Fe2O4 nanoparticles were used to characterize magnetic fields using an all-fiber Fabry–Perot interferometer. The 20-nm nanoparticles were fabricated with citrate and displayed a coercive field of approximately 10 mT. The nanoparticles were dispersed in oleic acid to prepare a magnetic fluid to fill a Fabry–Perot structure fabricated by arc splicing with conventional single-mode and hollow core photonic crystal fibers. This device provided sensitivity and resolution of 0.11 dB/mT and 0.09 mT, respectively. Thermal analysis indicated that the magnetic measurements are weakly depending on temperature (0.7 pm/°C and 7 × 10−3 dB/°C). This device offers low-cost fabrication, simple implementation and may be used in several industrial applications.

Experimental realization of D-shaped photonic crystal fiber SPR sensor

A novel surface plasmon resonance sensor based on a D-shaped, all-glass, endless single-mode photonic crystal fiber is experimentally demonstrated in this paper, which provides a new approach to realizing a high-performance photonic crystal fiber surface plasmon resonance sensor. In order to achieve the best performance, the side-polished position of the D-shaped photonic crystal fiber is theoretically and experimentally obtained. The proposed sensor can be used in wavelength and intensity interrogations simultaneously, and the experimental results of wavelength interrogation agree well with theoretical results. By combining the two interrogation methods, we present a two-feature interrogation method to improve the resolution. As a new interrogation method, the two-feature resolution is determined to be 6.53 × 10−5 RIU, which is higher than those of the wavelength and intensity interrogations.

Coupling Characteristics of Fused Optical Fiber Coupler Formed with Single-Mode Fiber and Photonic Crystal Fiber Having Air Hole Collapsed Taper

Fused coupler forming with a single-mode fiber (SMF) and a photonic crystal fiber (PCF) is one of the solutions for optical coupling from a light source to a PCF. In this paper, we presented coupling characteristics of a fused fiber coupler formed with an ordinary SMF and a PCF having air hole collapsed taper. A prototype of SMF-PCF coupler with air hole collapsed taper was fabricated using CO2 laser irradiation. The coupling efficiency from SMF to PCF was −6.2 dB at 1554 nm wavelength in the fabricated coupler. The structure of the SMF-PCF coupler to obtain high coupling efficiency was theoretically clarified by beam propagation analysis using an equivalent model of the coupler with simplification. It was clarified that appropriately choosing the prestretched or etched SMF diameter and the length of air hole collapsed region was effective to obtain high coupling efficiency that was a result of high extinction ratio at cross port and low excess loss. We also demonstrated that the diameter of prestretched SMF to obtain high coupling efficiency was insensitive to the air hole diameter ratio to pitch of the PCF in the air hole collapsed SMF-PCF coupler.

Endlessly single-mode photonic crystal fiber as a high resolution probe.

We sample ultra-broadband light, focused onto a diffraction-limited spot, to an endlessly single-mode photonic crystal fiber (ESM) and detect both the field amplitude and phase using a SEA TADPOLE interferometer. We resolve spatial features up to 2.5 times finer than the fiber mode size while sampling the periodic features of the bipolar oscillating field in the transverse section. The resolution enhancement is expected also in other types of single-mode fibers in intensity measurements and leads to an inexpensive method for characterizing the point-spread function of such optical fields, e.g., diffraction-limited spots from microscope objectives. In addition, we demonstrate the guidance of a high-NA light field in the fine structure of an ESM fiber mode. The results are especially valuable for devices where a fiber tip acts as an input slit and defines the spatial resolution, e.g., fiber-based interferometers, spectrometers, and sensors.

Design of a Single-Polarization Single-Mode Photonic Crystal Fiber Filter Based on Surface Plasmon Resonance

We design a single-polarization single-mode photonic crystal fiber filter based on surface plasmon resonance. The finite element method is employed to evaluate the characteristics of the filter. The proposed fiber is devised such that there is a great discrepant confinement loss between two polarizations of x and y by varying two air holes in the cladding region, which is composed of hexagonal structural air holes in pure silica selectively filling with gold wires. Numerical simulations show that single-polarization single-mode operation waveband can be tuned by adjusting the parameters of the photonic crystal fiber. The confinement losses of the unwanted polarization can reach to 126.10 and 326.30 dB/cm in the wavelengths of 1.31 and 1.55 μm, while the corresponding confinement losses of the wanted polarized mode are only 0.08 and 1.20 dB/cm, respectively. Furthermore, the crosstalk can come to a maximum of 120.34 and 310.41 dB in the two communication bands. The bandwidths of the fiber designed for 1.31 and 1.55 μm are, respectively, 20 and 60 nm, which may be found useful applications for fiber polarizer.

Advanced Spatial-Division Multiplexed Measurement Systems Propositions-From Telecommunication to Sensing Applications: A Review.

The concepts of spatial-division multiplexing (SDM) technology were first proposed in the telecommunications industry as an indispensable solution to reduce the cost-per-bit of optical fiber transmission. Recently, such spatial channels and modes have been applied in optical sensing applications where the returned echo is analyzed for the collection of essential environmental information. The key advantages of implementing SDM techniques in optical measurement systems include the multi-parameter discriminative capability and accuracy improvement. In this paper, to help readers without a telecommunication background better understand how the SDM-based sensing systems can be incorporated, the crucial components of SDM techniques, such as laser beam shaping, mode generation and conversion, multimode or multicore elements using special fibers and multiplexers are introduced, along with the recent developments in SDM amplifiers, opto-electronic sources and detection units of sensing systems. The examples of SDM-based sensing systems not only include Brillouin optical time-domain reflectometry or Brillouin optical time-domain analysis (BOTDR/BOTDA) using few-mode fibers (FMF) and the multicore fiber (MCF) based integrated fiber Bragg grating (FBG) sensors, but also involve the widely used components with their whole information used in the full multimode constructions, such as the whispering gallery modes for fiber profiling and chemical species measurements, the screw/twisted modes for examining water quality, as well as the optical beam shaping to improve cantilever deflection measurements. Besides, the various applications of SDM sensors, the cost efficiency issue, as well as how these complex mode multiplexing techniques might improve the standard fiber-optic sensor approaches using single-mode fibers (SMF) and photonic crystal fibers (PCF) have also been summarized. Finally, we conclude with a prospective outlook for the opportunities and challenges of SDM technologies in optical sensing industry.

A single-mode highly birefringent dispersion-compensating photonic crystal fiber using hybrid cladding

Based on the hybrid cladding design, a single-mode photonic crystal fibre (PCF) is proposed to achieve an ultra-high birefringence and large negative dispersion coefficient using finite-element method. Simulation results reveal that with optimal design parameters, it is possible to achieve an ultra-high birefringence of 2.64 × 10−2 at the excitation wavelength of 1.55 μm. The designed structure also shows large dispersion coefficient about −242.22 to −762.6 ps/nm/km over the wavelength ranging from 1.30 to 1.65 μm. Moreover, residual dispersion, effective dispersion, effective area, confinement loss and nonlinear coefficient of the proposed PCF are discussed thoroughly.

Design and analysis of single-mode tellurite photonic crystal fibers for stimulated Brillouin scattering based slow-light generation.

We theoretically examine two designs of single-mode (i) Er-doped tellurite and (ii) undoped tellurite photonic crystal fiber (PCF) for generation of slow light with tunable features based on stimulated Brillouin scattering. We obtained (i) Brillouin gain up to 91 dB and time delay of ∼145 ns at maximum allowable pump power of ∼775 mW in a 2 m Er-doped tellurite PCF and (ii) Brillouin gain up to ∼88 dB and time delay of ∼154 ns at maximum allowable pump power ∼21 mW in a 100 m undoped tellurite photonic crystal fiber. Simulated results clearly indicate that the doped tellurite PCF with Er enhances the maximum allowable pump power and comparable time delay can be obtained even with reduced photonic crystal fiber length. We believe that the carried out examination and simulation have potential impact on design and development of slow-light-based photonic devices applicable in telecommunication systems, enhancement of optical forces, and quantum computing.

A Polarization Maintaining Single-Mode Photonic Crystal Fiber for Residual Dispersion Compensation

A single-mode octagonal photonic crystal fiber (OPCF) is proposed to simultaneously achieve high birefringence and ultra-flattened ultra-high negative dispersion. Simulation results demonstrate that by introducing an elliptical air hole in the center of the core, it is possible to obtain a large average dispersion of −608.93 ps/nm/km with an absolute dispersion variation of −12.7 ps/nm/km over 1.46–1.625 $\mu \text{m}$ wavelength bands for fundamental slow-axis mode. Besides, with optimal design parameters, a high birefringence of $1.81\times 10^{\mathrm {-2}}$ and a very low confinement loss of 0.04 dB/km are achieved at 1.55 $\mu \text{m}$ . The proposed OPCF can be used in cost-effective residual dispersion compensation and optical sensors.

Automatic arc discharge technology for inscribing long period fiber gratings.

We experimentally demonstrate an automatic arc discharge technology for inscribing high-quality long period fiber gratings (LPFGs) with greatly improved inscription efficiency for single mode fiber (SMF) and photonic crystal fiber (PCF). The proposed technology was developed by implementing an embedded program in a commercial fusion splicer. In addition, the improved technology employs an ultraprecision motorized translation stage, and the tensioning mass required by conventional technology was eliminated. While hundreds of arc discharges are generally required by conventional technology, only 30 and 60 arc discharges were required to inscribe LPFGs with dip attenuations of 30 and 20 dB for SMF and PCF, respectively.

Design of Single Mode Photonic Crystal Fiber with Outstanding Characteristics of Confinement Loss and Chromatic Dispersion over S to L Communication Band

In this article, a novel structure of photonic crystal fiber with nearly zero ultra- flattened chromatic dispersion and ultra-low confinement loss is presented. By replacing the circular air-holes of two first rings with the elliptical air-holes, a fiber with outstanding features of chromatic dispersion and confinement loss is designed. The proposed structure is optimized for operating in a wide wavelength range covering S, C, and L communications bands. Finite Difference Frequency Domain (FDFD) solver is applied to analyze the proposed fiber components. The designed fiber exhibits a chromatic dispersion of -0.12 ps/nm/km at 1.55 µm along with a slope of 0.002 ps/nm 2 /km. Also, the other remarkable feature of this fiber is ultra-low confinement loss in order of 10 -5 dB/km around λ = 1.55 µm.