Optical OFDM Research Articles

Bidirectional intensity modulated/direct detection optical OFDM WDM-PON system

Bidirectional intensity modulated/direct detection optical OFDM WDM-PON system

Maximizing wireless power transmission for electric vehicles with high-intensity laser power beaming and optical orthogonal frequency division multiplexing

This paper presents a method for determining the optimal power transmission path for wirelessly charging electric vehicles using high-intensity laser power beaming in environments with multiple power transmitters and receivers. The proposed method uses an optical orthogonal frequency division multiplexing system. The power receiver selects the optimal power transmitter and wireless power channel based on the maximum power requirement. The paper also validates the proposed method through simulation and experimentation.

Peak-to-Average Ratio Suppression Algorithm for Non-Hermitian Symmetric Optical OFDM System Based on GA-PTS

Peak-to-Average Ratio Suppression Algorithm for Non-Hermitian Symmetric Optical OFDM System Based on GA-PTS

Differential Index Shift Keying DC Bias Optical OFDM in Turbulent Channels

Differential Index Shift Keying DC Bias Optical OFDM in Turbulent Channels

Design of IM-DD Optical Communication using Matlab

A modulation scheme where the intensity of an optical source is modulated by the RF or mm-wave signal. Demodulation is achieved through direct detection of the optical carrier and conversion using a photo detector is called IM-DD Systems. In these systems the multi-layer modulation (MLM) is used to design both asymmetric clipped optical OFDM (ACO-OFDM) and dc-biased optical OFDM (DCO-OFDM) as a function. In this systems the DCO OFDM is more spectrally efficient than non-DC biased systems because this have better tradeoff between spectral and power efficiency. In the direct detection system, the detection process is non-linear due to the photo current proportional to absolute square of electric field intensity due to this the signal is slow. The equalizer is comprised of one hidden layer which leads to super-fast of the signal .The channel capacity for this systems can be measured by the transmitting of the signals. This IM/DD is a cost-effective optical communication which finds wide applications in fiber communication, free-space optical communication, and indoor visible light communication. In these systems when the bandwidth of signal exceeds the modulation bandwidth of LED, multi path effect occurs. Therefore, we use ACO-OFDM to avoid this multi path distortions. OFDM is a suitable efficient cost-effective solution for GPON deployment with benefit of use of low-cost laser bandwidth in comparison with DCO-OFDM. At the same BER performance, in comparison with D-C ACO-OFDM at high bit rates transmission, DCO-OFDM promises to deliver higher throughput.

Transformer-Based Long Distance Fiber Channel Modeling for Optical OFDM Systems

The fiber channel model plays an essential role in the simulation and design of optical fiber communication systems. However, it is difficult for conventional model-driven modeling to balance accuracy and efficiency, especially in optical orthogonal frequency division multiplexing (OFDM) systems with complex and long-haul transmission. We introduce the simplified Transformer into optical OFDM systems and combine it with the feature decoupled distributed (FDD) scheme for fast and accurate fiber channel modeling. Unlike the popular Transformer architectures, we remove the Decoder part and cancel the self-attention with quadratic complexity, significantly reducing the computational cost. The modeling performance is investigated from the nonlinear fitting capability, accuracy, and generalization ability. The transmission distance ranges from 80 km to 1600 km. The highly matched four-wave mixing (FWM) power, low error vector magnitudes (EVMs), and similar signal-noise ratios (SNRs) demonstrate the high precision and robustness of the model. Furthermore, the modeling is studied under different transmission rates and is proved to be reliable over a wide transmission bandwidth. Compared to the bidirectional long short-term memory (Bi-LSTM), the Transformer performs better in accuracy and has lower computational and memory costs. For modeling under the same conditions, the required running time of the Transformer is about 60% of Bi-LSTM, less than 1% of the split-step Fourier method (SSFM). The Transformer-based method achieves high precision modeling of the fiber channel in the long-distance and high-rate optical OFDM system and makes a significant breakthrough in complexity.

Deep learning based channel estimation optimization in VLC systems

This paper aims to improve the channel estimation (CE) in the indoor visible light communication system. The proposal of this paper deals with a system that depends on a comparison between Deep Neural Network (DNN), Yolo v3, and Kalman filter (KF) algorithm, for two optical modulation techniques; asymmetrically clipped optical-orthogonal frequency-division multiplexing (ACO-OFDM) and direct current optical-orthogonal frequency division multiplexing (DCO-OFDM). The CE can be evaluated by the error rates in the received bits, where increased error means a performance decrease of the system and vice versa. Receiving less errors at the receiver indicates improved CE and system performance. Hence, the main aim of our work is to decrease the error rate by using different estimators. Furthermore, we apply automatic hyper-parameter approach and Bayesian optimization, to Yolo v3 model to improve the system performance and reduce the positioning error. The metric parameter of bit error rate (BER) aims to determine the improvement ratio in different systems. The model in this paper is based on training with OFDM samples of signal with labels which are received and are corresponding to the signals of OFDM. At a BER = 10−3 with DCO-OFDM, the DNN outperforms KF with 1.7 dB (8.09%) at the bit energy per noise (E_{b} {/}N_{o} ) axis. Also, for ACO-OFDM at BER = 10−3, the DNN achieves better results than KF by about 1.9 dB (11.8%) at the (E_{b} {/}N_{o} ){ } axis. For different values of M in QAM, the DNN outperforms KF for ACO-OFDM by average improvement of ~ 1.2 dB (~ 13%).

Design and development of coherent-OOFDM techniques in wavelength division multiplexing optical network for long-haul communication

Abstract Today, communication is a crucial factor and requires a high data rate for transmission with in an error-free environment, so optical communication has emerged as a best solution to high-speed transmission systems due to its higher bandwidth and higher data rates. Fiber optic transmission integrating with some modern processing and modulator techniques are applied in various areas that need transfer of data from one point to another through reducing an optical affect. Coherent optical orthogonal frequency division multiplexing is a popular technique in optical communication today because of the excessive spectral efficiency, immune to interference, tolerance of the fiber dispersion and it is long-haul application. It employs the OFDM modulation method, which is a type of multicarrier modulation in which data statistics are distributed over a large number of low-cost subcarriers and is a solution to inter-symbol interference. Inter-symbol interference is generated by chromatic dispersion in high-speed optical transmission systems, and it is a severe issue in long-haul systems in the case of higher data rates transmission. The use of standard dispersion compensating devices, such as dispersion compensating fiber, does not completely compensate for high order dispersion, which includes third-order and high dispersion effects and also increase the loses of the system because it is a fiber in itself. This study proposes introducing the concept of coherent optical orthogonal frequency division multiplexing techniques in to the wave division optical network in the case of multiple users, high data rate transmission and long-haul and ultra-long-haul optical link to reduce the optical transmission on related issues and to improve the performance of optical network. The performance of the proposed network can be evaluated by using different parameters such as signal to noise ratio, bit error rate, optical signal to noise ratio, Quality factor and eye-diagram at different distance transmission up to 8000 km by using Optisystem software.

Low complexity partition-recombined SLM scheme for reducing PAPR in coherent optical OFDM systems

High peak-to-average power ratio (PAPR) remains the main challenge of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. Selective mapping (SLM) is a well-known effective PAPR reduction technique, but it suffers from high computational complexity. To reduce the PAPR of OFDM signals, a low-complexity, partition-recombined SLM (PRSLM) scheme is proposed. The PRSLM scheme can generate more candidate signals than that of the conventional-original SLM (COSLM) scheme. The real and imaginary components of time-domain symbols are first partitioned, and then recombined to generate new candidate signals, which reduces computational complexity significantly. A 40-GBaud single-polarization CO-OFDM transmission system is set up to evaluate the performance of the PRSLM scheme. Simulation results show that the proposed scheme achieves 61.9% reduction in complex multiplication complexity, and 60.3% reduction in addition complexity compared with the COSLM scheme when the FFT size is 128. Furthermore, the proposed scheme achieves a similar PAPR reduction performance to the COSLM scheme without bit error rate degradation. In a nutshell, the PRSLM scheme improves noise tolerance and implementation efficiency of high-speed optical communication as well as alleviates nonlinear impairments.

An Optimal SNR Symbol Decomposition With Serial Transmission Scheme for O-OFDM-Based VLC System

This letter introduces an optimal signal-to-noise ratio symbol decomposition with serial transmission (OSNR-SDST) scheme for optical orthogonal frequency division multiplexing (O-OFDM)-based visible light communication systems with the capability against non-linear clipping distortion. The time-domain O-OFDM symbol is repeatedly clipped based on the optimal times of symbol decomposition determined by the optimal SNR judgment. Optimal SNR judgment is the process of comparing the SNR values of multiple successive symbol decomposition times and choosing the preferred times with the highest SNR as the optimal times of symbol decomposition. The decomposed symbols are sequentially serialized to form a frame for individual LED transmit. Simulations show that the proposed OSNR-SDST exhibits superior transmission performance, especially in bit error rate performance, optical transmit power, and communication rate, over the conventional iterative signal clipping (ISC) and adaptive symbol decomposition with serial transmission (ASDST) schemes. Moreover, the proposed OSNR-SDST is also superior in reducing the complexity of frame synchronization and hardware implementation.

Performance of RoF-MMW-WDM Backhaul System based on Hybrid Optical OFDM Transportation Enabling 128-QAM Format for B5G Communication Networks

For growing transmitting capability over fixed bandwidth, there are many potential techniques that had been developed in the recent years. There are several possible methods for increasing transmission capacity over fixed bandwidth. One of the most effective methods that can offer achieving more information is orthogonal frequency division multiplexing (OFDM). We designed a powerful simulation framework for a backhaul RoF-MMW optical transmission system between main base station and remote antenna unit based on multi-carrier OFDM modulation. The powerful simulation of next generation optical MC-OFDM transportation along RoF-MMW long transmission system had been successfully implemented. By using 50 Gb/s default bit rate and 128 QAM modulation format for OFDM-RoF-MMW system along 50 km, the best achievement of overall bit rate obtained (11.2 Tb/s) with accepted BER to get ultra-high-capacity transmission system. Thanks to the python DSP and the losses compensators used in the simulation framework, the PAPR losses and drift in the receiver section had been compensated and many values of OFDM sub-carriers (16 and 32 OFDM sub-carriers) achieved for ultra-high-capacity transmission system.

QCOB: a novel QPSK coherent optical OFDM modulation technique for mitigation of fiber impairments

Abstract Modern optical communication heavily relies on coherent optical orthogonal frequency division multiplexing (CO-OFDM) modulation. But the usage of optical OFDM for fiber optic communication is still constrained in comparison to other modes of communication like visible light communication (VLC) and wireless communication due to a number of issues such as various sorts of fiber impairments including dispersion and attenuation. In this research paper, a novel optical OFDM modulation technique has been proposed. It is quadrature phase shift keying (QPSK) CO-OFDM modulation with Bessel optical filter in fiber optical link and is named as QCOB. This modulation technique works for optical fiber transmission. Its testing has been carried out for parameters like bit error rate (BER) and quality-factor (Q-factor) over a range of fiber length, fiber dispersion coefficient and input power. This modulation employs coherent optical OFDM with QPSK for subcarrier modulation. The optical link utilizes a Bessel optical filter. Improved results have been achieved over conventional QPSK CO-OFDM (QCO). The obtained results demonstrate the superiority of the QCOB technique in terms of performance enhancement and fiber impairment reduction. In comparison to the QCO technique, the BER performance (reduction in BER) of the QCOB technique shows an improvement of around 7.4, 100, 14.4, 46.4 and 3.4% for dispersion coefficient values of 10, 20, 30, 50 and 100 (in ps/nm-km), respectively.

Reducing peak to average power ratio (PAPR) for visible light communications (VLC) system using Walsh–Hadamard precoded discrete Hartley transforms

Abstract In visible light communication (VLC), intensity modulation with direct detection (IM/DD) based on DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) is used to transfer data at a high rate. Because OFDM signals are modulated using IM/DD, the peak of the transmitted signals is scaled up, resulting in a high peak-to-average power ratio (PAPR). In this article, the Walsh–Hadamard transform (WHT) is used as a precoder for discrete Hartley transform (DHT) to decrease the PAPR and the DC bias and achieve a good bit error rate (BER) performance in such a system. PAPR reduction results from the decrease of superposition of the transmitted signals owing to the use of WHT as a precoder. The proposed scheme and conventional DCO-OFDM indoor VLC system based on discrete Hartley transform (DHT) are compared to assure the new system’s benefits and efficiency.

Mitigation of fiber impairments by developing a novel coherent optical 16-QAM OFDM modulation technique

Mitigation of fiber impairments by developing a novel coherent optical 16-QAM OFDM modulation technique

Blind channel estimation for DCO-OFDM based vehicular visible light communication

Blind channel estimation (CE) methods for OFDM based RF communication provide high-rate transmission by eliminating pilot overhead in conventional pilot-based methods, at the cost of lower accuracy. However, there is no work on the blind CE for OFDM based visible light communication (VLC) systems. In this paper, we propose a novel blind CE method for vehicular VLC with the goal of improving CE accuracy based on the exploitation of the channel statistics derived, by utilizing extensive amount of data collected for different communication angles, distances, and ambient light conditions. First, the normalized channel frequency response (CFR) of the V2LC channel is demonstrated to be invariant of inter-vehicular distance, relative transmitter/receiver zenith angle and ambient light. Then, this channel characteristic is exploited in the blind CE to improve its accuracy with two-step estimation of normalization factor. Extensive simulations at different vehicle speeds show that the proposed method outperforms the pilot-based and superimposed training-based CE methods in terms of spectral efficiency both for all modulation schemes and at all relative speeds. The proposed blind channel estimation (CE) method provides 9.77% increase in the spectral efficiency, compared to the second best method, superimposed training-based CE, at 20 dB signal-to-noise ratio (SNR) and 160 km/h relative speed, for 64-Quadrature Amplitude Modulation (QAM) Direct Current-Biased Optical Orthogonal Frequency Division Multiplexing (DCO-OFDM). Moreover, the real-time performance of the proposed blind CE is demonstrated for a realistic vehicle mobility scenario extracted from SUMO.

Symbol-interleaved precoding technique for DDO-OFDM systems with the KK receiver.

Receiver sensitivity of direct-detection optical orthogonal frequency-division multiplexing (DDO-OFDM) systems can be significantly improved by using the Kramers-Kronig (KK) receiver. However, the KK algorithm is sensitive to the high signal-to-average power ratio (PAPR) of the OFDM signal, which may violate the minimum phase condition (MPC) and lead to severe signal distortions during the optical field reconstruction. Channel-independent discrete Fourier transform (DFT) precoding technique can efficiently reduce the PAPR and realize subcarrier signal-to-noise ratio (SNR) equalization, but the PAPR of the precoded signal will increase due to chromatic dispersion. Besides, the relevant researches exhibit that it is hard to accurately reconstruct the complex field from the sampled signals based on KK relation at the low carrier-to-signal power ratio (CSPR) even if the MPC is satisfied. To combat the signal distortions induced by the KK algorithm and improve the bit error rate (BER) performance, we propose and verify DFT/Walsh-Hadamard transform (WHT)-based precoding with a simple symbol-interleaving technique for DDO-OFDM transmission systems. In addition to PAPR reduction, the proposed technique can equalize both subcarrier and inter-symbol SNRs efficiently. The simulated results show that the BER performance can be improved by up to one order of magnitude at a CSPR of 6 dB after up to 1000km single-mode fiber transmission, compared to the conventional DFT precoding technique. It is expected that the proposed technique can be employed to improve the receiver sensitivity of medium-reach DDO-OFDM transmission systems with the KK receiver.

Reconstructed Hybrid Optical OFDM-NOMA for Multiuser VLC Systems

Non-orthogonal multiple access (NOMA) is deemed to be a prospective multiple access technology of the next generation. However, in visible light communication (VLC), when advanced hybrid optical orthogonal frequency division multiplexing (O-OFDM), such as hybrid asymmetrically clipped O-OFDM (HACO-OFDM), is combined with NOMA, error propagation is induced, which degrades the system performance. Therefore, a novel reconstructed hybrid O-OFDM-NOMA (RHO-OFDM-NOMA) scheme is conceived in this paper. In order to eliminate the error propagation, the users in RHO-OFDM-NOMA opt for the ACO-OFDM or clipping-free O-OFDM signals according to their channel qualities, which are subsequently superimposed on pulse-amplitude-modulated discrete multitone (PAM-DMT) to yield the spectrum-efficient hybrid O-OFDM signal. Furthermore, a reconstruction process is designed to ensure the non-negativity. Compared with HACO-OFDM, the proposed RHO-OFDM can retain the error propagation in NOMA-VLC, whilst maintaining the superiorities of high spectral and power efficiency. It is demonstrated by simulation results that RHO-OFDM-NOMA can support a notably higher data rate than the NOMA schemes using conventional O-OFDM.

Performance Evaluation of Dispersion Compensation Fiber-based Coherent Optical OFDM-WDM for Long Haul RoF

Demanding extra Bandwidth and high data rates has been meet by the integration both of wired and wireless communication systems. For that the Radio over Fiber (RoF) technology has gained a traction. In this article a Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) is proposed as the main wired system for transmitting data at high rates suffers from the polarization mode dispersion and chromatic dispersion of the optical channel which mitigates the data rates. Thus, to combat these limitations a Desperation Compensation Fiber (DCF) which adds negative attenuation to the optical signals transmitted in optical fiber is suggested. Moreover, the addition of Wavelength- Division- Multiplexing (WDM) to the system of transmission provides better bandwidth saving, high data rates, and better spectral efficiency, and power utilization. The efficiency of high data rate CO-OFDM integrated with RoF for long haul transmission between 100km and 450km with data rates up to 10 Gbps have been investigated in this article with SMF-DCF with 16 DPSK and 16-QAM modulations schemes respectively. The simulation results showed that the proposed system can achieve a high data rate up to 55 Gbps but when integrated with WDM, with a fiber link length can be increased to up to 6600 kilometers, with highest data rate up to 1.65 Tbps.

Performance investigation of various modulation techniques in coherent optical orthogonal frequency division multiplexing (CO-OFDM) system

Abstract One of the essential aspects of life is communication and in all communication systems, modulation and demodulation perform a crucial role in the transmission of transmitter-to-receiver data. Using various multiplexing techniques such as FDMA, CDMA and TDMA to work with the communication system, faced various problems such as low bit rate, multi-path fading, ISI and time dispersion. The incorporation of the OFDM approach gives an attractive solution to the aforementioned issues. OFDM transmitters and OFDM receivers with different modulation techniques are included in the OFDM-based different communication system. CO-OFDM was recently suggested and its extreme robustness against polarisation mode dispersion and chromatic dispersion was demonstrated in proof-of-concept transmission experiments. Optical fiber-based wired networks and also free space wireless networks require a premier technique for multiplexing i.e. CO-OFDM. In this paper, we investigated the performance of various modulation techniques which highlights several benefits such as channel robustness and greater efficiency of the available spectrum where multicarrier is used as high data rate bit streams from a single source are divided into the number of small subcarriers. OFDM is commonly regarded as discrete multitone (DMT) in this case. So in this review article, OFDM systems are also incorporated with their advantages and applications.

A hybrid encryption scheme of DNA and chaotic precoding for IMDD-FBMC systems

A new scheme that combines deoxyribonucleic acid (DNA) encryption algorithm and chaotic Walsh–Hadamard transform (WHT)/discrete Fourier transform (DFT) precoding to improve security performance is proposed for the first time in the filter bank multicarrier (FBMC) systems with intensity modulation and direct detection (IMDD). In our proposed scheme, we employed DNA and chaotic WHT/DFT precoding to achieve bit-level and symbol-level encryptions, respectively. With this hybrid encryption scheme, it is expected not only to enhance data transmission security but also to improve the bit error rate (BER) performance. We conducted experiments in the 16/32 quadrature amplitude modulation (QAM)-FBMC systems with IMDD. The relevant results show that our proposed scheme can improve receiver sensitivity by around 1 dB at the BER of 3.8e−3 compared with the scheme using only DNA encryption or without encryption. And a huge key space of 101806/101024 by DNA-chaotic WHT/DFT encryption is achieved. In addition, the net bit rate of transmission systems can be enhanced with a similar BER performance, compared to the optical orthogonal frequency division multiplexing (OFDM) systems.