Full-duplex hybrid FTTH and RoF transport system based on polarization modulators

In the paper, we proposed a simple method to generate two millimeter-wave (MMW) signals for radio-over-fiber (RoF) systems. Firstly, we utilized two cascaded dual-drive Mach-Zehnder modulators (DD-MZMs), both biased at the maximum transmission bias point (MATBP), to implement frequency octupling. And then, a wavelength division multiplexing demultiplexer (WDM Demux) is followed to filter out the −4 order optical carriers of the second DD-MZM's output to enable an optical single side-band (OSSB) modulation by only modulating the baseband data onto the −4 order optical carrier. On the other hand, the +2 order optical carrier of the first DD-MZM's output is filtered out based on an optical splitter (OS) and an optical rectangle band-pass filter (ORBPF). After that, the +2 and the −4 order optical carriers are combined to be transmitted in an identical fiber path. Finally, a 45 GHz and a 60 GHz MMWs were generated simultaneously with a 7.5 GHz local oscillator (LO), by self-heterodyning these optical carriers in a photonic detector (PD). After 50 km single-mode fiber (SMF) transmission distances, the 45 GHz and the 60 GHz MMWs were maintaining good performance with clearly open eye diagrams and power penalties of 0.6 dB and 1.1 dB, respectively, at a bit-error-rate (BER) of 1×10−9.

Radio over fiber (RoF) system is the most appropriate combination of fiber optic link and radio waves. Orthogonal frequency division multiplexing (OFDM)-RoF system can increase the capacity of modulation radio frequency (RF) access with high speed data transmission. The purpose of this paper is modeling and simulation an OFDM-RoF system for fiber length up to 100 km by using 16-quadrature amplitude modulation (16-QAM). OptiSystem 13 software is used for simulation. The proposed model of OFDM-RoF system uses two low pass cosine roll off filter (LP-CROF) as filter at the OFDM stage output and two LiNb-Mach Zehnder modulator (LiNb-MZM) as optical modulator. The results of simulation include the spectrum signal visualizers at the OFDM output, RF to optical upconventer (RTO) output as well as 16-QAM received constellation. The results of simulation have shown that increasing of roll off factor value, it will be broadening in filter band transition. The proposed of RoF-OFDM system is able to achieve fiber length up to 100 km uses 16 QAM sequence bit, the received power is 71.617 dBm with electrical and optical amplifications by using 10 Gbps data signal.

A simple bidirectional radio over fiber (RoF) design based on orthogonal frequency division multiplexing (OFDM)-based millimeter wave (mm-wave) signal generation and transmission with compensation of linear and non-linear impairment with the aid of sparse second-order Volterra non-linear equalizer (S2-VNLE) is proposed. At the central station (CS), an optical 60 GHz OFDM-based mm-wave downlink signal is generated by a 16-QAM downlink radio frequency (RF) signal. The generated OFDM-based downlink mm-wave signal is transmitted to the base station (BS) via bidirectional single-mode fiber (SMF) of length 75 km. At BS, the downlink signal is photo detected and transmitted via an antenna to the user end. The 16-QAM uplink RF signal, obtained via a receiving antenna from the user end, is modulated on the unused carrier of the downlink mm-wave signal. The modulated uplink signal is transmitted to the CS through the same bidirectional fiber. The carrier reuse and fiber reuse reduce the system complexity. However, the simultaneous signal co-propagation may induce linear and non-linear impairment, further degrading the system performance and has to be compensated. The compensation of linear and non-linear impairment is done by full Volterra non-linear equalization (FVNLE). However, pruning the insignificant Volterra filter coefficient enables a reduction in computational complexity. The sparse second-order Volterra non-linear equalization (S2-VNLE) is obtained by l1-regularization to cut off the kernels with a moderate contribution. The weights of the tap coefficient are updated by the RLS algorithm. The transmission performance of compensated bidirectional RoF system is investigated. The performance analysis of the bidirectional RoF system shows improved efficiency, having performance closer to FVNLE with reduced system and computational complexity.

In this paper, the performance of a 60 GHz radio over fiber (RoF) system with 4/16/64 quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) downstream signals is studied. Delivery of 10 Gbit/s M-ary QAM (MQAM) OFDM signals through the 20-km-long single-mode fiber (SMF) is complicated in terms of intensity modulation and direct detection (IM/DD). Using self-homodyne method, the beating of two independent light waves generating the millimeter-wave at the photodetector can be down-converted to baseband in the electrical domain. Meanwhile, three kinds of sub-carrier arrangement schemes are compared and discussed, and the simulation results show that lower peak-to-average power ratio (PAPR) can be obtained adopting the adjacent scheme. At bit error rate (BER) of 10-3, the receiver sensitivity using 4QAM-OFDM sub-carrier signal is almost enhanced by 4 dB and 9 dB compared with those of 16QAM-OFDM signal and 64QAM-OFDM signal.

We propose an analytic technique, based on the Volterra series, to assess the impact of nonlinearities on the error probability of orthogonal frequency division multiplexing (OFDM) signals in radio over fibre (RoF) based wireless networks. We consider OFDM/BPSK signals and we determine the error probability of these signals in an illustrative RoF system, where either a semiconductor laser diode (SLD) or a Mach-Zehnder modulator (MZM) are used to generate these signals, with good agreement between analysis and simulation.

In this article, we review our recent research progresses on the field programmable gate array (FPGA)-based real-time generation and reception of orthogonal frequency-division multiplexing (OFDM) signals for the short-reach direct-detection system and radio-over-fiber (RoF) system. With the low-complexity real-time digital signal processing (DSP) algorithms, a high-definition video signal with a data rate of 2.97 Gb/s transmission over 20 km single-mode fiber (SMF) without using forward error correction (FEC) technique is experimentally demonstrated in an intensity-modulated direct-detection optical OFDM system in the presence of sampling frequency offset (SFO). In addition, a real-time X-band OFDM-RoF system with heterodyne detection was also realized. With the help of Reed-Solomon coding with a multiplesymbol interleaving/de-interleaving scheme, the 16-ary quadrature amplitude modulation (16-QAM) OFDM-RoF signals over 10-m wireless and 2.26-km SMF-28 link was successfully achieved with a post-FEC bit error rate less than 1×10-9.

We propose a novel all-optical frequency upconversion technique for radio-over-fiber (RoF) systems based on cross-gain modulation (XGM) and cross-polarization modulation (XPolM) in a semiconductor optical amplifier (SOA). A local oscillator signal is carried onto a continuous wave probe beam with orthogonally polarized single-sideband (SSB) modulation using a polarization modulator and a tunable optical filter. The intermediate frequency signal carried by a pump beam is only intensity modulated onto the sideband of the probe beam while the carrier of the probe beam is unmodulated thanks to the joint use of the XGM and XPolM effects in the SOA. This SSB upconversion scheme is inherently free from the chromatic-dispersion-induced power fading after transmission over single-mode fiber. The proposed scheme is theoretically analyzed and experimentally verified.

Wavelength reuse in a bidirectional UWB over fiber system using a polarization modulator (PolM) and an electro-absorption modulator (EAM) is proposed and experimentally demonstrated. Since the PolM functions as a special phase modulator that supports phase modulation along the two principal axes with opposite modulation indices and the EAM is a polarization-independent component, the signals due to the phase-modulation to intensity-modulation (PM-IM) conversion along the two orthogonal directions in the upstream link will be complementary and cancelled out, thus the impact of the downstream signal to the upstream transmission due to the PM-IM conversion is fully eliminated. Error-free bidirectional transmission of a 1.25-Gbps UWB signal over 17 km single-mode fiber (SMF) is demonstrated. A power penalty due to the wavelength reuse for upstream transmission is measured to be as low as 0.2 dB.

Radio-over-fiber (RoF) technology has several benefits such as larger bandwidth, reduced power consumption etc. that has made it an attractive implementation option for various communication systems including wireless LANs. This paper investigates the feasibility of orthogonal frequency division multiplexing (OFDM) as a modulation technique for a RoF based WLAN system in consistency with IEEE 802.11a. Results from a Matlab system model, which is consistent with the specifications of IEEE 802.11a, have been included to show the BER performance of the OFDM modulation technique. Next, the paper presents the results obtained from measuring several of the main factors affecting the performance of an OFDM system, including channel noise, multipath delay spread, power clipping, and synchronization requirements.

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique to transmit wired and wireless media. Radio over Fibre (RoF) system consists of both wireless and optical links. It is proved technology for the wireless access technique, and the OFDM has core technology for major part of the wireless network. The OFDM-RoF system is the subject of much research of various topics at the moment. OFDM-RoF system provides high speed, large capacity and high spectral efficiency in the recent 4G and upcoming 5G mobile technology with fast data transmission. OFDM has specific modulation methods such as PSK, BPSK, QPSK, and QAM techniques. The aim of this paper is to perform and simulate BER and Q-Factor of OFDM-RoF system at different parameters, including 16-QAM modulation technique using OptiSystem13.0 simulation software.

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique to transmit wired and wireless media. Radio over Fibre (RoF) system consists of both wireless and optical links. It is proved technology for the wireless access technique, and the OFDM has core technology for major part of the wireless network. The OFDM-RoF system is the subject of much research of various topics at the moment. OFDM-RoF system provides high speed, large capacity and high spectral efficiency in the recent 4G and upcoming 5G mobile technology with fast data transmission. OFDM has specific modulation methods such as PSK, BPSK, QPSK, and QAM techniques. The aim of this paper is to perform and simulate BER and Q-Factor of OFDM-RoF system at different parameters, including 16-QAM modulation technique using OptiSystem13.0 simulation software.

This paper proposes a novel none pilot-assisted orthogonal frequency division multiplexing (OFDM) technology based on multi-differential amplitude phase shift keying (mDAPSK) for optical OFDM system. It doesn't require any bandwidth-consuming pilot tones or training sequence for channel estimation due to the differential detection during demodulation. In the experiment, a 41.31 Gb/s 64DAPSK-OFDM signal without pilot tones is successfully transmitted over 160-km single mode fiber (SMF). The performance comparison between multi-quadrature amplitude modulation (mQAM) and mDAPSK is also given in the experiment, and the results indicate a prospect of this technology in optical OFDM system.

A novel method to generate ultra-wideband (UWB) signals based on two differential group delay modules and one Mach-Zehnder Modulator is proposed. Both simulation and experiments verified that the method could generate two kinds of UWB monocycles using low bit-rate non-return-to-zero data source (1Gbps). The monocycles have a fractional bandwidth of 127% at centre frequency 5.5GHz. Keywords: Ultra wideband (UWB), radio-over-fiber (RoF), differential group delay (DGD) 1. INTRODUCTION Ultra-wideband (UWB) is a fast emerging technology for short-range broadband wireless communication such as wireless personal area network and sensor network, etc. The UWB signal occupies wide bandwidth and has low power density, and it has immunity to multi-path fading [1]. As a carrier-free modulation scheme, direct-sequence impulse radio is more cost-effective and simpler compared with multi-band orthogonal frequency scheme. Since UWB is a room-scaled short range wireless communication technique, the wireless networks can operate mainly in indoor environment in standa lone mode. Considering the integration of UWB access networks and fixed wired networks, the combination of UWB-over-fiber technology and fiber-to-the-home (FTTH) technology is a competitive candidate for future wideband access networks [2]. So many all-optical schemes that fit for UWB-over-fiber technology to generate and distribute UWB impulses have been reported recently. Zeng et al. proposed two approaches to generate UWB impulses using one phase modulator (PM), and 25-km single mode fiber (SMF) or FBG to convert phase-modulated light to UWB pulses [3, 4]. Wang and Dong proposed UWB signal generation using cross-gain modulation or cross-phase modulation in semiconductor optical amplifier [5, 6], which requires two laser sources and may increase the system complexity. Chen proposed a scheme based on optical polarization time delay [7]. It is a simple method, but the elect rical signal source needs at least twice bit-rate compared to the carried data. Most of the schemes n eed an electrical Gaussian pulse source, which is comm only composed of a high-speed pulse pattern generator (PPG). This is an expensive construction, for which the PPG should work at least 10 Gbps. Furthermore, if data are carried on the UWB pulses, another modulator should be added to the systems, which increase the system cost and complexity. In this paper, we proposed and experimentally demonstrated a simple method to generate data-carried UWB monocycle pulses based on two differential group delay (DGD) modules and one Mach-Zehnder modulator (MZM). Instead of the data pattern “1000 0000 ”, which has one “1” followed by several “0”s to form the UWB signal, we use electrical non-return-to-zero (NRZ) data. The NRZ data modulate the optical signal in MZM to get an optical binary phase shift keying (BPSK) signal, which is then fed into two cascade DGD module s while the polarization of the light is carefully adjusted

In order to serve the explosive demands of triple play services or multimedia services with high quality of data transmission in Fifth Generation (5G) communication systems which has availability of large spectrum unlike Fourth Generation (4G), low latency, improved transmission, and increased reliability, an access networks with optical fiber distribution network and wireless enabled technology is urgently needed and therefore, a prominent technology known as Radio over Fiber (RoF) is suggested by researcher/Scientists due to a perfect blend of flexible fiber technology and wireless mobility. RoF technology is helping the data transmission systems from last thirty years with great success and has numerous advantages such as scalability, transparency, antenna site complexity reduction, low installation cost, accessibility of radio carrier by diverse antenna sites dynamically. Millimeter waves (Mm waves) integration in 5G wireless RoF systems comes out to be an encouraging candidate to cater the bandwidth hungry current as well as future generation internet application such as high definition TV (HDTV), online games, video conferencing, and voice over IP (VoIP) etc. For the prolonged reach, economical installations, and improved performance, optimal Mm wave generation methods should be incorporated in 5G such as employing multi carrier generation technique (MCG). Deployment of single mode fiber (SMF) in 5G offers high speed, large capacity, improved security, etc., but also has a prominent limitation of nonlinear effects and it is unwanted phenomenon which degrade the system performance by introducing intermodulation distortion, distortion of signal phase, harmonic distortion, and interference in the neighbouring channels. Minimum modifications of architecture and minimum cost should be spent on the compensation of nonlinear effects or Kerr’s effects in RoF systems and recently mode division multiplexing has emerged as an ultimate solution. In this review article, detailed discussion of an evolutionary technology, i.e., RoF is presented with a literature review, present evaluations, and future challenges. Our utmost goal is to enrich the young researchers with precious aspects for RoF technology on single platform and also encourage them to conduct the technology advancement research works in various fields such as nonlinear compensation, Mm wave generation, dispersion compensation, cost reduction, complexity reduction, and security enhancements for 5G RoF systems.

Improving the performance of a bidirectional radio over fiber (RoF) link by the use of fiber Bragg grating(FBG) in a carrier suppressed double sideband(CS-DSB)modulation based wavelength reuse incorporating coherent detection and signal processing unit like DSP is proposed. A comparison study is used to evaluate the performance improvement by the use of FBG. At the transmitter, a downstream optical signal containing optical single sideband+carrier(OSSB+C)is generated and transmitted to base station via a single mode fiber(SMF). The signal received is reused at the base station, in two ways in order to study the performance improvement of RoF by the use of FBG. The optical single side band and carrier is separated by the help of a FBG. The carrier is further reused for the upstream signal transmission and the downstream signal can be recovered. The upstream signal is recovered using coherent detection along with DSP unit to avoid the noise due to the phase difference from the transmitter laser source and to eliminate the cross talk effects.