57 research outputs found
High-Speed Bi-directional Optical Wireless System in Non-Directed Line-of-Sight Configuration
We propose and experimentally demonstrate the first bi-directional optical wireless link operating in non-direct line-of-sight (Nd-LOS). The system is based on visible light emitting diode (LED) for downlink and infrared LED for uplink. We achieve around 250 Mbit/s for both downstream and upstream transmission, with the ambient light noise of usual indoor illumination level (500 lx), produced by warm-white LED. 100 Mbit/s are guaranteed inside 12 m of a common room scenario, without LOS tracking. An optimized discrete multi-tone modulation gives bit-error-ratios always below of the common forward-error-correction threshold of 1.5 ×10. These results indicate that this scheme has great potential for practical VLC system implementation
Time-domain Fourier optics for polarization-modedispersion compensation
We report on a novel technique to compensate for all-order polarization-mode dispersion. By means of this
technique, based on a suitable combination of phase modulation and group-velocity dispersion, we compensated
for as much as 60 ps of differential group delay that affected a 10-Gbit/s return-to-zero data stream
DEVICE AND METHOD FOR COMPENSATING POLARIZATION MODE DISPERSION IN AN OPTICAL COMMUNICATION SYSTEM
Simple and effective solutions for low-cost coherent WDM-PON
This paper presents the most significant results achieved in the last two years by our group in coherent ultra-dense-WDM PON for λ-to-the-user access. Here we mostly focus on the architectures based on simple OOK-NRZ modulation format. We demonstrated the real-time implementation of our coherent receiver and we proved its compatibility with direct modulated laser (DML). Receiver sensitivities as low as -48 dBm at BER=1·10-3 for 1.25 Gb/s has been observed, showing the feasibility of a coherent ONU receiver based on devices commonly available and with limited cost. The system support quite high ODN losses and allows the λ-to-the-user approach
3.4 Gbit/s Visible Optical Wireless Transmission Based on RGB LED
In this paper, we experimentally realized a gigabit-class indoor visible light communication system using commercially available RGB White LED and exploiting an optimized DMT modulation. We achieved data rate of 1.5 Gbit/s with single channel and 3.4 Gbit/s by implementing WDM transmission at standard illumination levels. In both experiments, the resulting bit error ratios were below the FEC limit. To the best of our knowledge, these values are the highest ever achieved in VLC systems
A Visible Light Localization Aided OpticalWireless System
We report about a Line of Sight Optical Wireless Communication (LoS OWC) system aided by a simplified Visible Light localization algorithm for tracking purposes. We show experimentally that by combining the LoS OWC system with the localization algorithm it is possible to provide a gross datarate exceeding 300 Mb/s over a 90 degrees illumination angle by using a RGB visible-light LED at 90 cm distance
Harmonically mode-locked Ti:Er:LiNbO3 waveguide laser
Active mode locking of an Er-diffusion-doped Ti:LiNbO3 waveguide laser by intracavity phase modulation to as
high as the fourth harmonic (5.12 GHz) of the axial-mode frequency spacing is reported. The diode-pumped,
pigtailed, and fully packaged laser with a monolithically integrated intracavity phase modulator has a threshold
of 9 mW (incident pump power Ep jj c) and emits transform-limited pulses of >3.8-ps width and <5.6-pJ pulse
energy (gain-switched mode locking) at 1602-nm wavelength (Es jj c). The relative change of the mode-locking
frequency with the temperature is 3.65 3 1025y±C. The mode-locking acceptance bandwidth is 675 kHz near the
axial-mode frequency spacing at approximately five times the threshold pump power
Enhanced 10 Gb/s operations of directly modulated reflective semiconductor optical amplifiers without electronic equalization
We report enhanced 10 Gb/s operation of directly modulated
bandwidth-limited reflective semiconductor optical amplifiers. By using a single suitable arrayed waveguide grating we achieve simultaneously WDM demultiplexing and optical equalization. Compared to previous approaches, the proposed system results significantly more tolerant to seeding wavelength drifts. This removes the need for wavelength lockers, additional electronic equalization or complex digital signal processing. Uniform C-band operations are obtained experimentally with < 2 dB power penalty within a wavelength drift of 10 GHz (which doubles the ITU-T standard recommendations)
Monolithically integrated DBR waveguidelaser and intensity modulator in erbiumdoped LiNbO3
For the first time, a DBR laser has been integrated with a Mach
Zehnder intensity modulator in Er diffusion doped, Z cut
LiNbO,, with Ti indiffused waveguides and dry etched Bragg
gratings. The monolithically integrated device has a threshold of
54.8mW incident pump power (hp = 1480nm) and emits, in a
single longitudinal mode, up to 0.65 mW CW output power at hs
= 1561nm. The Mach-Zehnder type intensity modulator has an
optical bandwidth > 3GHz
Blind Adaptive Chromatic Dispersion Compensation and Estimation for DSP-Based Coherent Optical Systems
We propose an accurate and low-complexity blind adaptive algorithm for chromatic dispersion (CD) compensation and estimation in coherent optical systems. The method is based on a Frequency Domain Equalizer (FDE), a low complexity Time Domain Equalizer arranged in a butterfly structure (B-TDE) and an Optical Performance Monitoring (OPM) block in a loop configuration. The loop is such that, at each iteration, the CD value compensated by the B-TDE and estimated by the OPM is given to the FDE; according to this estimation, in the subsequent iteration, the FDE compensates also this quantity. The procedure is repeated until the majority of CD is compensated by the FDE and a small residual quantity is compensated by a low complexity B-TDE with a small number of taps. The method is extended to long haul uncompensated links exploiting the information on the mean square error (MSE) provided by the B-TDE. The proposed algorithm is then experimentally validated for a polarization multiplexed quadrature phase shift keying (PM-QPSK) signal at 112 Gbit/s propagating along 1000 km of uncompensated Z PLUS® optical fiber. A statistical analysis of the performance of the proposed solution, in terms of mean value and standard deviation of the CD estimation error, is carried out, running a set of simulations including different impairments, such as noise, polarization dependent loss, polarization mode dispersion and self-phase modulation in a line of 1000 km of uncompensated G.652 optical fiber. Our method could be used to compensate and estimate any CD quantity without increasing the number of taps in the B-TDE and exploiting devices already included in the system (TDE, FDE and OPM) arranged in a loop
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