We propose an orbital angular momentum (OAM) photonic crystal fiber (PCF) that can control the dispersion of OAM
mode by using a ring-core to which a graded-index profile is applied. Using the full-vectorial finite element method
(FEM), the properties of the proposed OAM PCF were analyzed. We found that when the thickness of the ring-core to
which the graded-index profile was applied is reduced, the dispersions of the modes guided to the core decrease overall.
We investigate visible light car-to-car (C2C) communications by considering multiple reflections from the floor in underground and covered parking environments as well as interferences from the ambient lighting (i.e., fluorescent lamps) via experimental measurements. A set of messages are transmitted and we experimentally confirm that the transmitted message set is successfully recovered. The average signal distribution patterns are measured and analyzed at a transmission distance, considering the installed heights of the transmitter and receiver. In general, the light components from fluorescent lamps in indoor environments affect the average voltage level of the received signal, which is more significant at higher receiver positions. The measurements show that the indoor visible light communication performance is varied depending on floor reflections as well. We have experimentally shown that the BER less than 1.0 × 10 − 6 could be achieved over the measurement plane by varying the height of the transmitter, consequently, varying the contribution of floor reflections.
The orbital angular momentum (OAM) mode is considered as a new degree of freedom for mode division multiplexing (MDM) to overcome the increasing data capacity because of its orthogonality and theoretically unlimited number of OAM mode. Although OAM modes have been successfully demonstrated in free-space-based and conventional fibers, these have limited applications because of the gradual enlargement of these modes with propagation and small number of modes. In this paper, we propose a photonic quasi-crystal fiber (PQF) for supporting up to 38 orbital OAM mode with a flat dispersion characteristic over the C+L bands. We numerically investigated the eigenmodes in the proposed PQF and these effective indices, electric field intensity distributions, dispersion, and confinement loss. The designed PQF which consists of a large hollow center and quasi structural small air holes in the clad region exhibits low confinement losses and many number of OAM modes, and satisfies a radially single mode condition and a large effective index separation (>10-4) between the same order of the OAM modes. This proposed fiber could potentially be exploited for mode division multiplexing and other OAM mode applications in fibers.
We report the effect of interferences on visible light car-to-car communication system. The interferences from floor reflections and fluorescent lamps are taken into account for indoor car-to-car visible light communication (VLC) systems. The system is composed of a white LED lamp as a VLC transmitter and a photo-receiver with an appropriate optical filter as a VLC receiver. The signal power distribution patterns are measured and analyzed at a transmission distance, considering the positions of the transmitter and receiver. Generally, the light from fluorescent lamps in indoor environment affects the DC level of the received signal power, which is more significant at higher receiver positions. The measurements show that the indoor VLC communication performance can be varied depending on floor reflections. Also, the fluorescent ceiling illuminations affect the DC level change of the received VLC signal waveforms.
We propose a dispersion flattened and high birefringence terahertz photonic crystal fiber using roll up method with
PTFE. The PCF made of this method shows dispersion flatness by the air region between PTFE tubes around core and
high birefringence by asymmetric mode distributions. When using rod with Dout = 1mm, dispersion of the proposed THz PCF has a slope of 0.4ⅹ10-2 near 0.848 THz and the value of the then is about 0.21 ps/THz.cm. In this structure, the order of birefringence is 10-3 and the order of confinement loss is about 10-11 dB/m.
We have proposed a hybrid square-lattice PCF using two different sized air holes and conventional square lattice
cladding structure. Based on the plane wave expansion method and finite element method, we numerically investigated it
polarization and dispersion properties compared to the conventional square lattice photonic crystal fiber. From the
numerical results, it is shown that the proposed structure provides high birefringence and still maintains negative
dispersion property. Numerical results show that the birefringence of the hybrid square-lattice PCF reaches 10-2. The
value and slope of the chromatic dispersion are also negative over the C band.
Photonic quasicrystals are unique structures having long-range order but no periodicity. It has been found that
quasiperiodic structures give rise to unusual phenomena and properties that have not been observed in periodic
structures. Recently, it has been reported that introducing quasi-periodic structures of microscopic air holes in optical
fibers can give rise to a unique dispersion property such as almost zero ultra-flattened chromatic dispersion and large
mode area dispersion compensating fiber.
In this paper, we introduce a ring core photonic quasicrystal fiber (PQF) and its optical properties are theoretically
analyzed. The chromatic dispersion properties of doped ring core PQF, are investigated along with their dependence on
the proposed defect parameters using 3D full-vectorial Beam Propagation Method (BPM) and plane wave expansion
method.
We propose an index-guiding supersqure lattice PCF with two missing air holes as a defect core and analyze the
polarization properties using a plane wave expansion method. From the numerical results, the proposed fiber is an
absolutely single polarization single mode over the wide wavelength range from 1 to 2μm where only the slow axis
mode is guided and the fast axis mode becomes a radiative mode.
We propose a dual-core photonic quasicrystal fiber with six-fold symmetry that may be useful in compensating
chromatic dispersion of a single-mode fiber. The geometry of the proposed photonic quasicrystal fiber is described and
then the behaviors of effective index and chromatic dispersion are calculated according to the structural parameters. The
dual-core fiber is composed of a pure silica inner core and an outer core that is formed by reducing the diameter of air
holes in the third cladding layer. We investigate the dependence of the effective indices of inner core and outer core, the
fundamental super mode, and the effect of chromatic dispersion on the structural parameters by using plane wave
expansion method.
The dual-core photonic quasicrystal fiber has a large negative chromatic dispersion value of approximately -2000 ps
nm-1 km-1 over optical communication band around 1.5μm. Introducing quasicrystal structures in the dual-core optical
fibers can improve the capability of dispersion compensation of the fibers significantly.
We propose new design parameters for few mode index-guiding holey-fiber (IGHF) that can provide ultra-flattened dispersion properties as well as adiabatic mode transformation capability. A novel silica index guiding holey fiber (IGHF) design is proposed utilizing a new hollow ring structure that is composed of germanosilicate high index ring and hollow air hole imbedded in a triangular lattice structure. The proposed IGHF showed unique modal properties such as nearly zero flattened dispersion over a wide spectral range with low dispersion slope by flexible defect parameter control. It is predicted that ultra-flattened dispersion of 0±0.5ps/(km.nm) from wavelength 1360nm to 1740nm could be achieved with a slope less than 1•10-3ps/km.nm2, along with fine tuning ability of dispersion value. In contrast to prior IGHF, the proposed fibers can be achieved adiabatic mode transformation from annulus mode to a mode generated from solid multi-core fiber due to germanosilicate rings that is highly compatible to LP01 mode in conventional step index fiber. This adiabatic mode conversion of optimized IGHF for ultra-flattened dispersion contributed to low splicing loss, 0.01dB at 1550nm to dispersion compensation fiber.
We propose new design parameters for index-guiding holey-fiber (IGHF) that can provide flexibility in defect and lattice design as well as adiabatic mode transformation capability. The new defect consists of the central air hole and germanosilicate-ring surrounding it.
In this paper, utilizing layers of hollow structure as a defect, we introduce a new IGHFstructure and its optical properties are theoretically analyzed and experimentally demonstrated. The annulus mode intensity profile, effective mode area, chromatic dispersion properties and splicing loss for the single-layered and two-layered defect structure are investigated along with their dependence on the proposed defect parameters using plane wave expansion method and 3D full-vectorial Beam Propagation Method (BPM).
Unlike conventional silica defect IGHF, the proposed structure showed an annulus mode profile in the fundamental mode, which can benefit from larger effective area to separate the fiber non-linearity from other unique optical properties of IGHFs. The proposed IGHF also showed low splice loss unlike previous conventional IGHFs with collapsed hole by arc since the newly introduced defect structure, germanosilicate-rings are remained as solid core with high index contrast D. With the new defect parameters we could achieve a large area annulus mode profile, low splice losses to standard fiber, 0.7dB at 1.55 m, and chromatic dispersion with low slope, 0.002ps/km.nm2
We have experimentally demonstrated a new compact surrounding refractive-index sensor using MMF-CSF-MMF structure. For refractive index range of 1.30 to 1.42, resolution of 9.68×10-3 /nm and linear dynamic range of 20.5dB were obtained at λ=1310nm.
A new index-guiding-holey-fiber is proposed for flexible modal birefringence control by introducing a fourlayered defect with central air hole, silica pedestal, germanosilicate ring, and silica clad. Effects of these parameters over birefringence are reported.
We have designed channel-drop filters with two line defects and a resonance system based on the two-dimensional triangular-lattice-hole photonic-crystal structure by two-dimensional and three-dimensional finite-difference time-domain simulations. The quality factors have been calculated to be around 3,500 of a two-dimensional channel-drop filter and to be around 300 of a resonance system based on the triangular-lattice hole-based photonic-crystal slab structure.
We have developed an finite-difference time-domain program that can analyze photonic devices with gain and/or dispersion. As an example, a two-dimensional photonic-crystal laser is simulated. The simulation can show the relaxation oscillation behavior at extremely high current injection.
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