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Vehicle-to-Vehicle (V2V) Communication is one of the most promising application opportunities of Visible Light Communication (VLC). This paper suggests a novel transmission technique for VLC-V2V applications, called 2x2 Differential Transmission (2x2 DT). This transmission method exhibits excellent common-mode optical noise rejection performance. This beneficiary property is presented first with simulation results and later with real-life urban traffic measurement as well. After the promising simulation results, a demonstrational automotive-grade VLC-V2V link is presented and investigated for evaluation purposes. The link does not contain electrical filters, optical filters nor optical lenses, hence link costs are kept low and versatility is preserved. With our proposed 2x2 differential solution, both the transmission quality and common-mode optical noise rejection performance is outstanding. Due to the increased sensitivity of the differential VLC transmission regarding crosstalk between channels, a method is suggested for crosstalk reduction for high-quality differential transmission.

Polarization effects of channels such as turbulent free space and optical fibers can deteriorate the quality of polarization-sensitive communication schemes, for example, quantum key distribution. The exact nature of the channel is problematic to determine, and most theoretical results are based on approximations. We introduce a general model with probabilistic polarization angle rotation and analyze the average error it causes in terms of the moments of the probability distribution. For a small rotation angle variance, an inequality between distributions’ errors is considered based on their kurtosis values and potentially higher-order central moments. An upper bound is determined for the error probability, holding for all practically interesting scenarios.

Future passive optical network (PON) designs with 5G have been expected to provide simultaneous multiple wireless signals to the end-users. In this regard, this paper for the first time proposes and experimentally demonstrates the simultaneous transmission of baseband 4-pulse amplitude modulation (4-PAM), and radiofrequency (RF) filter bank multicarrier (FBMC), and universal filter orthogonal frequency division multiplexing (UF-OFDM) signals in a PON. A single optical wavelength from a laser source is used to demonstrate the signal transmission over a PON. The proposed system applies in one wavelength using one laser source for the PON. In contrast with conventional on-off keying (OOK) modulation format, 4-PAM modulation format can provide double bandwidth efficiency. Due to the property of high suppression for out of band emission, UF-OFDM and FBMC are considered as potential 5G modulation formats. In the optical line terminal (OLT), the composite signal consisting of 4-PAM, FBMC, and UF-OFDM is designed, generated, and transmitted using optical intensity modulation. The received signal is extracted in the optical network unit (ONU) and demodulated using digital signal processing techniques. Each of the above-mentioned modulation formats mentioned above is designed with a 2 Gbps data rate constituting a total of 6 Gbps aggregate data rate. The bit error rate (BER) and error vector magnitude (EVM) values have been measured after 25 km fiber length. Measurement results show EVM values below 12.5 % as a figure of merit as proposed by 3GPP LTE for 16 QAM modulation.

Communication applying visible light technology is a novel approach. Visible Light Communication (VLC) development is motivated by the increasing demand for wireless communication technologies. It has the potential to provide highspeed data communication with good security and improved energy efficiency. The rapid evolution of VLC was sustained by the LEDs performances. The Light-Emitting-Diode (LED) luminaires are capable of switching to the different light intensity at a fast rate. This function can be used for data transmission. This article focuses on the physical layer of the VLC links. It reviews the technology, the topology of the proposed connection, and the benefits of this approach. The main research trends are identified emphasizing state of the art in this area. It shows how VLC technology evolved and what are the performances achieved at this time. Various structures of the transmitter and receiver are studied, and different modulation schemes are investigated. Finally, numerous applications of VLC technology are presented.

Future 5G based passive optical networks (PON) are expected as capable of the simultaneous provision of wired and wireless services for multi-users. In this paper, for the first time, we propose and demonstrate the simultaneous delivery of wired 4-pulse amplitude modulation (4-PAM) and wireless multi-sub-bands filter bank multicarrier (FBMC) signals in one wavelength using one laser source for the future 5G PON. The 4-PAM can be used in cost-efficient intensity modulation direct detection (IM/DD) systems and it provides the double bandwidth efficiency compared to conventional on-off keying (OOK). FBMC is considered as a potential candidate for future wireless 5G due to its high suppression for out of band emissions, which allows combining multiple sub-bands with very narrow band-gaps. Using multi-sub-bands with a narrow band gap, the overall transmission capacity can be increased. In the designed system, the composite wired 4-PAM and wireless multi-sub-bands FBMC signal is generated and transmitted with intensity modulation in optical line terminal (OLT). In the optical network unit (ONU) the wired and wireless signals from the received composite signal are extracted using an electrical square band-pass filter and separately demodulated using digital signal processing techniques. The designed 4-PAM has baseband bandwidth of 4.8 GHz and multi-subbands FBMC consists of 4 sub-bands of 500 MHz each, having very narrow inter-sub-bands gap of 488.28 kHz and the aggregate bandwidth of 2.0015 GHz. The bit error rate (BER) has been evaluated for the performance analysis of the 4-PAM and multi-sub-bands FBMC for two cases (a) separate transmission and (b) composite transmission.

Expanding the functionality of LED indoor lighting with visible light communication (VLC) allows an additional communication channel beside wireless radio in buildings. This service may be based on various channel access methods and modulation types. Code division multiplexing (CDM) is a suitable method to such an application, but it is complicated to measure the signal quality which is essential to compare different codes and settings, and necessary for some applications like position-dependent information services. Computing crest factor is a suitable method to estimate quality, but it may be inaccurate in some cases. This paper presents novel methods to approximate the quality of received CDM signals along with the crest factor, aiding the more accurate investigation of the VLC CDM technique.

This paper demonstrates a hybrid radio over multimode fibre and free space optics (RoMMF-FSO) system that can be used to extend the transmission range of the fourth generation long-term evolution (4G-LTE) signal in access networks. A single mode filtering technique (SMFT) is used to enhance 4G-LTE performance. The proposed scheme is evaluated in terms of the system transfer function, laser beam profile, and error vector magnitude (EVM). We show that using SMFT increases the RoMMF-FSO system bandwidth by 2 GHz and improves the received optical power by 13.6 dB. Moreover, the proposed system enhances the EVM by 4%. The measured results show that by using a 1 km MMF instead of a 1 km SMF will marginally increase the measured EVM from ~6.6% to ~7% with a 0.2 dB power penalty with respect to the LTE EVM limit of 12.5% as is specified for 16-quadrature amplitude modulation. The proposed system is validated practically under atmospheric turbulence conditions to mimic the outdoor environment. Measured EVM results are verified theoretically through transmitting LTE signals with turbulent using log-normal model. We also show that for a FSO link span of 500 m to meet the EVM target of 12.5% the SNR power penalties are ~2 dB and ~11 dB for Rytov variance of 1.2 × 10-4 and 0.1, respectively, compared with no turbulence.

This paper addresses the needs of mobile access network and presents the benefits of integrated microwave photonics for 5th-generation (5G) mobile networks. Full convergence of the optical fiber and the wireless segments in the form of microwave photonics is described. The usage of integrated microwave photonics in optically supported wireless networks can provide a high-capacity mobile system based on the micro-wave and millimeter-wave frequency bands.

In-line and reflective semiconductor optical amplifiers (SOA and RSOA) can be effectively utilized as external optical intensity modulators. However the limited modulation bandwidth affects the application possibilities, because next generation access networks desire high trans- mission speed. Bandwidth enhancement can be achieved by means of optical equalization thanks to the chirping char- acteristics of semiconductor optical amplifier. The limited modulation transfer function can be combined with the converted phase modulation transfer function. Investiga- tion of optical filter with optimal slope is a crucial chal- lenge in this approach. The presented simulations describe the slope dependence of the modulation band. The model can take into account the different type of realizable opti- cal filters. However there is a trade-off between modula- tion efficiency and modulation bandwidth due to the extra insertion loss of the set-off optical filter. In the paper theo- retical and simulation investigations are presented with the result of improved modulation bandwidth.

Vertical-cavity surface-emitting lasers (VCSELs) have multiple beneficial properties in quantum key distribution (QKD). However, polarization switching (PS), which happens between two orthogonally polarized eigenmodes, is characteristic of these lasers. PS is extremely problematic if it is unwanted in all polarization-sensitive applications. The origin and properties of PS is discussed, along with potential error scenarios introduced to QKD protocols BB84 and B92. We propose a new transmitter design for the BB84 protocol using only two VCSELs—both corresponding to one of the two bases in which polarized photons are sent—, which are modulated in polarization, purposely generating switches between two orthogonally polarized modes. The methods of polarization modulation are described, along with advantages and design difficulties of the new design. We also consider the possibility of a spectral attack performed by an eavesdropper, originating from the frequency splitting between the polarization eigenmodes of a single VCSEL, and offer a theoretical solution that can protect the key from eavesdroppers utilizing this kind of attack.

A quantum random number generation method based on measuring the time differences between photon detections is analyzed mathematically in terms of bit generation efficiency and bit generation rate. It was found that these two values cannot be maximized simultaneously by altering the incident photon rate of a light source with Poisson statistics, but the generation rate can be increased at the expense of efficiency. Analytical results are presented for both an idealized and a practical case. The detector’s dead time has been taken into consideration in the latter case, implying that, for certain combinations of the dead time and the measurement clock period, the generation rate becomes a two-peaked function of the incident photon rate. The theoretical results are confirmed by simulations, showing excellent agreement between the two.

In this paper we study the radio frequency (RF) signal properties generated by direct mixing two laser beams, which can be used in very high frequency (e.g. terahertz) communications. We show the supply source stability has a critical effect in this procedure. It can broaden the RF signal spectrum up to 1 GHz. Although the linewidth of the lasers is the main factor determining the spectral width of the generated RF signal, the supply source instability also has a very significant contribution. In this paper we show the effect of these parameters by simulations and measurements.

The paper experimentally investigates indoor visible light communication (VLC) channels. The disturbances come from the light bulbs and other VLC systems. The paper demonstrates that the noisiest light bulbs are the fluorescent lamps which emit high frequency disturbances. Different light bulbs are examined to make an optimal carrier choice for the transmitted signal. In the next part of the paper several modulation schemes and two kinds of detector systems are compared. The paper represents also the advantages and disadvantages of receiver constructions with and without a lens. The optimum modulation for different application is investigated.

Several system applications require optical transmission of very high bit-rate digital as well as microwave and millimeter-wave carrier signals. Without completeness, a few recent applications are mentioned such as: 5G and Radio-over-Fiber (RoF) systems, Gigabit Passive Optical Networks (GPON), optical interconnection within Cloud for telecommunication Network Elements (NE), upgrade of mobile access, backhaul and core networks (NW) or phased array and antenna beamforming applications. Both chromatic dispersion and harmonic distortion result in unwanted limitations in the maximum distance and bandwidth. Dispersion penalty has been widely investigated in fiber-optical links transmitting microwave or millimeter-wave signals. However, less attention is addressed to the effect of the harmonics of the modulating fundamental electrical signal. This paper presents some theoretical and experimental results estimating the level of harmonics during the optical transmission.

In this paper, we focus on the study of large bandwidth wireless signal transmission following a 60 GHz standard over a multimode fiber link used to cover optical distribution for the last mile. To reduce the multimode effects within the fiber, a single mode fiber is first added to play a role of mode filter, and then replaced by a Mandrel as a filter. Error vector magnitude (EVM) is used as a metrics to analyze the signal degradation. Simulation results are confirmed by measurements. The EVM of the RoF links on single mode fiber, multimode fiber with and without filtering are compared.

In this paper, the method of generating optical single sideband (OSSB) scheme for radio over fiber (RoF) system using concatenated electro-optic amplitude modulator (AM) and phase modulator (PM) is presented. We provide the theoretical analysis of this configuration. With the proper control of parameters of the modulators, optical carrier to sideband ratio (OCSR) equal to 0 dB for OSSB scheme can be achieved in AM-PM configuration without the need of tunable optical filter. We illustrate through the numerical simulation the optimum values of AM dc bias and PM modulation index required to verify the proposed method.