Three-core Photonic Crystal Fiber Research Articles

Research on the preparation of multi-core photonic crystal fiber and the curvature sensing performance of three-core photonic crystal fiber

Two- and three-core photonic crystal fibers are prepared by using the same photonic crystal fiber preform structure. Not only the fiber diameter is reduced to standard size of 125μm, but also the core diameter is reduced to below 4μm. A curvature and temperature sensing system is built, and the curvature and temperature sensing performance of the three-core optical fiber is tested. When the length of three-core optical fiber is 150 mm, the measured curvature sensitivity is −7.27069 nm/m−1 in the range of 0 to 0.990 m−1, and the temperature sensitivity is −34 pm/°C during the temperature reduction from 75 to 45 °C. When the length of three-core photonic crystal fiber is 68 mm, the curvature sensitivity and temperature sensitivity are 2.42419 nm/m−1 and −7 pm/°C, respectively. In a small range of temperature, the sensor is insensitive to temperature, and the cross interference of temperature to curvature is very small.

Three-core photonic crystal fiber for the in-line measurement of full-polarization states by multi-core polarization interference theory.

In this Letter, we demonstrate and experimentally verify the application of three-core photonic crystal fiber (3C-PCF) for the in-line detection of fully polarized states. We prove the response of 3C-PCF to full-polarization states under multi-core polarization interference through experiments. The sensitivity at 1472 nm is 0.0273 nm/rad, and the linear response is better than 98.9% (the optimal operating wavelength can be designed in the range of 1470 to 1570 nm). With the advantages of an all-fiber integrated system, robustness, and wide wavelength coverage, our design holds great promise for facilitating fiber-optic-integrated polarization meters for optical fiber communication and biomedical diagnostic applications.

Erratum to “Bragg Reflection and Conversion Between Helical Bloch Modes in Chiral Three-Core Photonic Crystal Fiber”

The dispersion relation for the helical Bloch modes in this paper contains an error, which affects Equation (3) in the original manuscript, as well as Fig. 2. Otherwise the conclusions of the paper are unaffected.

Vector bending sensor for measuring spine curvature

A three-core photonic crystal fiber (TCPCF) vector bending sensor for measuring spine curvature is proposed. Refractive index variations of the TCPCF due to the wavelength differences in the range of 1.25 to 1.85 μm are studied. We show a linear relation between refractive index and operating wavelength. The wavelength of 1.55 μm is chosen for simulation with high energy modules to compensate for bending loss. An asymmetrical fiber is designed to sense both the direction and magnitude of the curve. The asymmetrical geometry of fiber creates an asymmetrical refractive index profile that leads to shifts in light speed in different fiber sections. This geometry asymmetry, in turn, provides the information needed to calculate both variables. Bending effects on the TCPCF has been numerically studied by the finite element method. Data analysis shows that the proposed sensor is sensitive to bending with a sensitivity of 1.2199 pm.m. It also reveals high directional sensing.

Design and analysis of surface plasmon resonance sensor based on multi-core photonic crystal fiber

A three-core photonic crystal fiber refractive index sensor based on the surface plasmon resonance effect is proposed. The three cores of this sensor are symmetrical about the center. The gold film deposited outside the fiber structure makes this sensor contact with the analyte directly, which not only reduces the complexity of the fabrication but also makes the limiting loss very low. The sensing performance of the proposed sensor is investigated by using the finite element method. Numerical results show that the loss spectra of the x-polarized core mode are consistent with the y-polarized core mode. The sensor realizes the sensing detection of the analyte refractive index ranging from 1.37 to 1.42. When the analyte’s refractive index is 1.42, the maximum wavelength sensitivity of 2427 nm/RIU for x and y polarization, the corresponding maximum resolution can reach 4.12 × 10−5 RIU.

Research on three-core photonic crystal fiber plasmonic sensor based on surface plasmon resonance with three V-groove microfluidic channel

Research on three-core photonic crystal fiber plasmonic sensor based on surface plasmon resonance with three V-groove microfluidic channel

Design and research of a broadband mode-division multiplexer based on three-core photonic crystal fiber

A broadband mode-division multiplexer based on asymmetric three-core photonic crystal fiber is proposed in this paper. The device is mainly composed of a central core, which can provide the transmission of fundamental mode and higher-order mode, and two side cores providing fundamental mode transmission. According to the theory of optical coupling, the LP<sub>01</sub> mode light is input to the three fiber cores at the initial port separately, and in the transmission process the LP<sub>01</sub> mode on the left side core will be coupled and converted into the LP<sub>21</sub> mode light in the central core gradually. Similarly, the LP<sub>01</sub> mode of the right side core is transformed into the LP<sub>31</sub> mode of the center core. By optimizing the structural design and selecting the length of optical fiber, the best conversion from side core into central core can be completed at the output end simultaneously, thereby realizing the multiplexing of LP<sub>01</sub>, LP<sub>21</sub> and LP<sub>31</sub> modes in the central core. In the opposite direction, if the output end of the device is used as the initial port, the demultiplexing of three modes of light from the central core to the three cores can be realized. In thiswork, the finite element method and beam propagation method are used to optimize the simulation, and the optical coupling theory and supermode theory are combined to conduct analysis and calculation. The results show that at wavelength band from 1.49 μm to 1.63 μm, the maximum insertion loss of the device is 0.72 dB, and the lowest insertion loss is 0.543 dB at 1.55 μm, which is far lower than the general evaluation standard of 1 dB insertion loss. The low insertion loss also makes it possible to design cascaded multi-core photonic-crystal-fiber mode-division multiplexer. Compared with the existing mode-division multiplexing scheme, the device is more integrated and less affected by the external environment. When it is used with multi-core space division multiplexing fiber, it can better improve the mode-conversion efficiency and mode purity, reduce the coupling complexity and expand the communication capacity.

High-sensitivity three-core photonic crystal fiber sensor based on surface plasmon resonance with gold film coatings

A high-sensitivity three-core photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) is proposed in this paper. The gold film is selected as the plasmonic metal and coated on the outside surface of the PCF to excite the SPR phenomenon. There are three different diameter air holes of d1, d2, and d3 distributed on the cross-section of the sensor. Among them, sensor performance can be affected by changing the diameter of the central hole and the thickness of the gold film. The sensor shows the maximum confinement loss value and spectral sensitivity of 50 dB cm−1 and 30600 nm RIU−1, respectively, at analyte RI (na = 1.41), and the corresponding maximum resolution is 3.27 × 10–6. The above simulation result shows that the sensor has excellent performance, thus laying the foundation for future research.

Linear multi-functional logic gate in a three-core photonic crystal fiber

The growth of transmission rates in optical fibers can increase the demand for devices that perform network node processing. Usually, such devices achieve complex optical signal processing through high non-linearity effects and optoelectronic devices. In this work, we present the numerical acquisition of a configurable multi-function logic gate in which the OR and AND gates can be enabled based on the logic values entered in a selector. Our device consists of a single piece of three-core PCF, with linear pulse propagation, and without the need for any other mechanisms. This result presents evidence that information processing within functional fibers is possible and might be achieved using only fiber design.

Cross-phase modulational instability of circularly polarized helical Bloch modes carrying optical vortices in a chiral three-core photonic crystal fiber.

We report the first, to the best of our knowledge, observation of cross-phase modulational instability (XPMI) of circularly polarized helical Bloch modes carrying optical vortices in a twisted photonic crystal fiber with a three-fold symmetric core, formed by spinning the fiber preform during the draw. When the fiber is pumped by a superposition of left-circular polarization (LCP) and right-circular polarization (RCP) modes, a pair of orthogonal circularly polarized sidebands of opposite topological charge is generated. When, on the other hand, a pure LCP (or RCP) mode is launched, the XPMI gain is zero, and no sidebands are seen. This observation has not been seen before in any system and is unique to chiral structures with N-fold rotational symmetry. The polarization state and topological charge of the generated sidebands are measured. By decomposing the helical Bloch modes into their azimuthal harmonics, we are able to deduce the selection rules for the appearance of modulational instability sidebands. We showed that the four waves in the nonlinear mixing process must exhibit the same set of azimuthal harmonic orders.

Radio-over-free space optical space division multiplexing system using 3-core photonic crystal fiber mode group multiplexers

Radio over free space optics (Ro-FSO) systems have previously relied on the signal intensity, wavelength and polarization for multiplexing data streams in order to increase to the signal quality and achievable link range. This work leverages on optical space division multiplexing by using novel three-core photonic crystal fiber (PCF) mode group multiplexers and hexagonal mid-gapped tiered PCF mode group equalizers for improving the signal quality and increasing the achievable link range in a rural environment. At the transmitter, a three-core PCF mode group demultiplexer converts the fundamental mode into three distinct mode groups used as carriers for independent transmission of three radio frequency signals. At the receiver, the three PCF successfully equalizes the power from the received signal, with the channel impulse responses showing an improvement in the signal quality. An increment between 13.6% and 31.1% in the achievable link range for all channels is evident under medium and heavy fog conditions at the same bit error rate level, using the designed PCF mode group multiplexers and equalizers.

Numerical Simulation of Three-Core Photonic Crystal Fiber With Large Group-Velocity Dispersion

The three-core photonic crystal fiber (TC-PCF) is proposed to obtain large group-velocity dispersion (GVD) because of the coupling effects between the fundamental modes (FMs) of the central core and higher-order modes (HOMs) of the two side cores. The supermodes of the TC-PCF can provide concave anomalous- and normal-GVD profiles with large peak values at the maximum dispersion wavelengths (MDWs), which can be shifted in three wavelength windows of 1030 nm, 1550 nm and 1900 nm by properly tuning the refractive indexes of the cores or the air-hole diameters. Furthermore, the numerical results show that two segments of the TC-PCFs with large anomalous GVDs and opposite values of the third-order dispersion (TOD) can provide much higher efficiency of pulse compression than one segment of the TC-PCF. Additionally, the TC-PCFs with large normal GVDs can be used to stretch pulses due to their low nonlinearities and short fiber lengths.

Bragg reflection and conversion between helical Bloch modes in chiral three-core photonic crystal fiber

Optical fiber modes carrying orbital angular momentum (OAM) have many applications, for example in mode-division-multiplexing for optical communications. The natural guided modes of N -fold rotationally symmetric optical fibers, such as most photonic crystal fibers, are helical Bloch modes (HBMs). HBMs consist of a superposition of azimuthal harmonics (order m ) of order $\ell _{\rm{A}}^{(m)} = \ell _{\rm{A}}^{(0)} + mN$ . When such fibers are twisted, these modes become circularly and azimuthally birefringent, that is to say HBMs with equal and opposite values of $\ell _{\rm{A}}^{(0)}$ and spin s are non-degenerate. In this article we report the use of Bragg mirrors to reflect and convert HBMs in a twisted three-core photonic crystal fiber, and show that by writing a tilted fiber Bragg grating (FBG), reflection between HBMs of different orders becomes possible, with high wavelength-selectivity. We measure the near-field phase and amplitude distribution of the reflected HBMs interferometrically, and demonstrate good agreement with theory. This new type of FBG has potential applications in fiber lasers, sensing, quantum optics, and in any situation where creation, conversion, and reflection of OAM-carrying modes is required.

Three-core photonic crystal fiber surface plasmon resonance sensor

Abstract A three-core photonic crystal fiber (PCF) surface plasmon resonance (SPR) biosensor with high performance is presented. The structure of the biosensor is easy to implement and has good repetition. The outer layer of the fiber structure is gold film. The analyte is placed on the surface of the gold film. The Full vector finite element method is used to numerical simulation and analysis the transmission mode and characteristics of the three-core PCF-SPR biosensor. The influence of sensor structure parameters on sensing performance is investigated. The structure parameters are optimized. The optimum structure parameters are given. The refractive index (RI) sensitivity of the sensor is discussed there. The results show that the average refractive index sensitivity of the sensor is 3435 nm/RIU in the sensing range of 1.33–1.40, and the resolution is 2.91 × 10−6 RIU. The sensor has the advantages of high sensitivity and high resolution. And it can be applied to real-time detection of the biomolecules and small drug-molecules.

Critical Power in Three-Core Photonic Crystal Fibers

When a photonic crystal fiber has more than one core, the switching capacity loss among the cores as of a given power, called critical power, becomes a relevant effect for switching applications. In this paper, we study the critical power obtained when ultrashort pulses are propagated in a nonlinear directional coupler. Here, we consider the specific example of a three-core photonic crystal fiber in two possible arrangements: one-dimensional and triangular array. In each core, the pulses propagate in the anomalous dispersion regime, in which an input pulse in the form of a hyperbolic secant is injected into one of the cores, considering different input peak powers. By relating the group velocity dispersion and the coupling coefficient with the temporal width of the input pulse, we can observe some relations between the fiber parameters and the critical power. In addition, we show that when self-phase modulation is combined with other effects, the critical power can be increased or decreased depending on the combination of these effects.

Two and three-input all-optical logic gates on a planar three-core photonic crystal fiber

In this paper, we numerically demonstrate the acquisition of two all-optical devices that perform the OR and AND logic operations using a solid core Photonic Crystal Fiber (PCF) with three symmetrical cores in planar array using solitonic pulses modulated in PAM-ASK. We numerically simulated the propagation of 100 femto-second (fs) solitonic pulses through the PCF and solved the coupled-mode equations using the 4th order Runge-Kutta method. For the first device, we obtained the passive three-input OR and AND all-optical logic gates, which operated with high performance, so they could be used to replace more complex optical circuits (in which the occurrence of Boolean expressions like the three-input OR and three-input AND are very common) without the need for concatenation therefore saving space and eliminating problems regarding the cascading of logic gates. For the second device, we obtained the active two-input OR and AND all-optical logic gates, which operated with exceptionally high contrast ratios and could therefore be used in optical signals processing.

Ultrabroadband polarization splitter based on three-core photonic crystal fiber with a modulation core.

We design an ultrabroadband polarization splitter based on three-core photonic crystal fiber (PCF). A modulation core and two fluorine-doped cores are introduced to achieve an ultrawide bandwidth. The properties of three-core PCF are modeled by using the full-vector finite element method along with the full-vector beam propagation method. Numerical results demonstrate that an ultrabroadband splitter with 320 nm bandwidth with an extinction ratio as low as -20 dB can be achieved by using 52.8 mm long three-core PCF. This splitter also has high compatibility with standard single-mode fibers as the input and output ports due to low splicing loss of 0.02 dB. All the air holes in the proposed structure are circular holes and arranged in a triangular lattice that makes it easy to fabricate.

全固三芯光子晶体光纤偏振分束器

全固三芯光子晶体光纤偏振分束器

Polarization splitter based on three-core photonic crystal fiber with rectangle lattice

A polarization splitter in three-core photonic crystal fiber with rectangle lattice based on resonant tunneling effect is studied by the finite element method. The transverse-electric (TE) mode polarized light is limited to the launched port and the transverse-magnetic (TM) mode polarized light can directionally couple to the other port due to the large birefringence. A polarization splitter with a coupling length of 2.592 mm, extinction ratios of ERA = –151 dB and ERC = –22 dB, insertion losses of ILTE = 0.027 dB, ILTM = 2.89E–15, and 15 dB, and a bandwidth of 29 nm at the communication wavelength of 1550 nm is obtained. The designed polarization splitter exhibits nice performance characteristics under reasonable fabrication tolerance. The characteristics of the polarization splitter are influenced by the effect of surface plasmon resonance. The golden wires infilling into the air holes reduce the coupling length to 1.695 mm.

Ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber

An ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber is proposed. Two fluorine-doped cores and a central microstructured modulation core are introduced to achieve an excellent performance and an ultrawide bandwidth. Numerical simulation demonstrates that the splitter has a bandwidth as wide as 300nm, with an extinction ratio (ER) as low as -20 dB. At the wavelength of 1.55μm, the ER reaches -30 dB. All the air holes in our design are circular holes and are arranged in a triangular lattice that is easy to fabricate with the method of stack and draw. A suitable mode field area and a Gaussian-like mode field distribution lead to a low splicing loss that is as low as 0.04dB when splicing with standard single-mode fibers as the lead-in and lead-out ports.