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.
The feasibility of optical wireless communication links using high-brightness illumination light-emitting diodes (LEDs) is experimentally verified. We measure the modulation bandwidths of red-, green-, and blue-colored LEDs and the eye patterns for optical wireless links incorporating single- and multi-LED transmitters. The eye patterns of single-color red, green, and blue LEDs are compared. An optical communication link consists of an optical transmitter module with seven LEDs, and a packaged silicon photodiode as a receiver. The bit error rate (BER) curves are measured by varying the link distance and the horizontal offset to check their dependencies on the BER. The optical wireless communication link incorporating the transmitter with seven high-brightness illumination LEDs can support 10-Mb/s data transmission without any optimized optical filter to enhance optical gain. Based on the experimental results, it is demonstrated that a communication link with illumination LEDs could be used for short-reach optical wireless communication systems.
The study of an optical wireless communication link using illumination light-emitting diodes (LEDs) has been performed. The eye patterns and bit error ratio of LED transmitter are measured and compared according to the modulation frequency and the distance between optical source and receiver. From the experimental demonstration, it is shown that the optical wireless communication link using illumination LEDs can perform 20 Mb/s data transmission.
The feasibility of optical wireless communication link using high-brightness illumination light-emitting diodes (LEDs) is reported. The eye patterns of single-color red, green, and blue LEDs are measured and compared. For the blue LED, the 3 dB bandwidth is measured. An optical transmitter module incorporates seven LEDs as a basic
building block for planar light and a packaged silicon photodiode is used as a receiver. From the experimental demonstration with the 7-LED transmitter and a receiver, it is shown that the optical wireless communication link using high-brightness illumination LEDs can perform 10 Mb/s data transmission without any optimized optical filter to enhance optical gain.
A clock and data recovery circuit using the clock jitter reduction technique is proposed for a 622-Mbit/s burst-mode data stream. The clock jitter reduction is achieved by controlling the clock duty cycle with the phase information of the recovered clock. The proposed clock recovery circuit, based on the gated oscillator, recovers a low-jitter output clock with up to 4090 consecutive zeros.
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