Alamouti Coded Asymmetrically Clipped Optical OFDM for Improved Performance of Multi-Mode Fiber

We report here on generic space-division multiplexing and demultiplexing units for high-throughput transmission in multimode fibers, with the aid of computer generated hologram spatial filters.

Employing the optical frequency multiplication method, we present an experimental performance analysis of the generation of microwave carriers up to 40GHz and their transmission over a 4.4km multimode fiber link. Also, 16QAM and 64QAM radio signals up to 20MS/s symbol rate are recovered successfully in the 24-30GHz band after 4.4km multimode fiber transmission, complying with the transmitter constellation error requirements of wireless standard IEEE 802.11a.

We propose a point-to-point optical power allocation for the pulse amplitude modulated discrete multitone (PAM-DMT)-based hybrid optical orthogonal frequency division multiplexing (PHO-OFDM) system to enhance its bit error rate (BER) performance. As the power allocated to each branch of PHO-OFDM would lead to different BER performance, a joint derivation of the constellation combination and power spectral density of the noise is introduced and realized by the iterative approximation algorithm. Although the peak-to-averagepower ratio of PHO-OFDM increases slightly after the power allocation processing, the BER improvement can still be obtained on both the ideal and nonlinear transfer model of LED compared with the conventional PHO-OFDM under the same constellation combination.

Because of high spectral efficiency and anti-dispersion capability, optical orthogonal frequency division multiplexing (OFDM) can greatly improve the transmission performance of the optical communication systems. In particular, adaptively modulated optical OFDM (AMOOFDM) can manipulate signal modulation format on each subcarrier. For upgrading the existing multimode fiber (MMF)-based networks, AMOOFDM has become a promising solution. To enable a cost-effective MMF networks, subcarrier modulation (SCM) can be used to relax the requirements on the sampling rate of the digital-to-analog converter (DAC) and analog-to-digital converter (ADC). In this paper, AMOOFDM using triple-band SCM is proposed and investigated. The results show that with 6GS/s DAC and ADC, 46.SGb/s signal line rate is achieved at 400m. Even when the transmission distance is increased to 1200m, it is still possible to achieve a transmission rate of 30.22SGb/s.

Objectives: Novel channel estimation technique of MIMO-OFDM system based on Modified Kalman Filter (MKF).The performance metrics are bit error rate, types of modulation method, size of the antenna, types of the Kalman filter. Methods: The performance methods considered are MKF, Single Kalman Filter (SKF), Double Kalman Filter (DKF).We have evaluated channel effect with respect to QPSK modulation technique and Rayleigh channel. Using MATLAB simulation tool, we have plot the bit error rate versus signal to noise ratio graph for MKF, SKF and DKF method. Results: The proposed channel estimation method improves the bit error rate performance compare to conventional channel estimation method. We have compared the proposed MKF method with the SKF and DKF method. Theoretical analysis and simulation results shows that the proposed channel estimation and tracking method based on MKF offer the excellent improvement in bit error rate compare to conventional channel estimation method. Improvements: We have achieved lowest bit error rate in the proposed MKF method compare to SKF and DKF method. As we increase the number of antenna at transmitter and receiver side we have also achieved the lowest bit error rate in the proposed MKF method.

High speed transmission systems (> 10 Gb/s) for cost-sensitive applications such as metropolitan network have attracted extensive interest due to the explosive data traffic growth in such applications. Optical orthogonal frequency division multiplexing (OFDM) based on direct modulation and direct detection for single-mode fiber (SMF) and multi-mode fiber (MMF) without optical amplification and chromatic dispersion (CD) compensation was proposed. Recent research has also shown that optical OFDM can be used with electronic dispersion compensation using direct detection in SMF. However, laser frequency chirp has been identified as a key limiting factor of capacity-versus-reach performance. In this paper, we present a novel concept of low cost optical OFDM with direct modulation of distributed feedback (DFB) lasers and coherent detection at 51.4 Gb/s and 64 QAM. A comprehensive theoretical model of the proposed system is developed. The proposed optical OFDM system concept and performance is based upon using electronic precompensation of laser frequency response, and electronic post compensation of DFB laser frequency chirp and CD. A numerical simulation of the transmission performance of the aforementioned system is conducted using different fiber lengths (40 km, 60 km, 120 km) and chirp parameters, which shows its attractiveness for access and metro applications.

Summary form only given. We have proposed a novel optical orthogonal frequency division multiplexing technique that can overcome the spectral efficiency limitation of the conventional WDM system. This scheme permits substantial overlapping of the spectrum and can achieve the spectral efficiency up to 1 bit/s/Hz in principle. For demultiplexing, we used a newly developed optical discrete Fourier transformer (DFT) instead of electrical digital processing, which is impossible to apply in the optical frequency range. The optical DFT was realized by using a set of delay lines, a phase shifter and a coupler in the frequency domain and bit synchronization and an optical gate in the time domain. In experimental demonstration of this scheme, error-free operation was obtained with a 0.8 bit/s/Hz of spectral efficiency.

Various optical communication technologies use Optical-Code Division Multiple Access (Optical-CDMA) as a channel access technique, which allows transmission of different users simultaneously over the optical communication channel. Therefore, Optical-CDMA permits free undue interference transmission of several users. Whereas Wavelength-division multiple access (WDMA) is a technique that can be implemented on how the optical channel can be divided into subchannels. This paper proposes a Hybrid WDMA-Optical-CDMA over multi-mode fiber (MMF) transmission system for short haul-local area network. The WDMA system is carried out by using four Laguerre-Gaussian (LG) modes that operate over four main wavelengths (1551 nm, 1550 nm, 1549 nm and 1548 nm). Additionally, the Optical-CDMA system is carried out by using one dimension Zero Cross-Correlation (ZCC) code to overcome multiple access interference (MAI) between the four ZCC codes. The performance of our system is evaluated based on eye diagrams, Q-Factor and bit-error rates (BER) measurements.

A data clipping and normalization technique is employed to improve the performance of the overall direct detection optical orthogonal frequency division multiplexing (DCO-OFDM) system. A detailed analysis of clipping distortion introduced by digital clipping and normalization is provided. The normalization operation amplifies the clipped data signal to the maximum input amplitude of a digital-to-analog converter (DAC). Based on the analysis, a BER formula of the proposed scheme is derived over the AWGN channel and single fiber channel. Performance of an optical clipped OFDM with normalization is assessed through numerical simulations and Monte Claro simulation over the AWGN channel. Theoretical analysis and simulation results both show that the clipping and normalization scheme can greatly improve the BER of an optical OFDM. In particular, BER performance of the proposed transmission scheme was measured in a practical OFDM transmission platform. The measured experimental results show that the clipped and amplified OFDM signal exhibits superior performance in comparison with the conventional OFDM signal. The received sensitivity at a BER of 10−3 for a 4 Gsamples/s (2.6667 Gbits/s) clipped and normalized OFDM signal with clipping ratio of 4 after 100 km standard single-mode fiber (SMF) transmission was improved by 4.3 dB when compared with the conventional OFDM system. The measured results also showed that the clipped OFDM signal exhibits superior performance in comparison with the conventional OFDM signal. Therefore, a clipping and normalization at the transmitter is most effective, and a substantial performance improvement can be obtained by a simple normalization after clipping.

We proposed and demonstrated an all-optical triode based on a tandem wavelength converter using cross-gain modulation (XGM) in semiconductor optical amplifiers (SOAs). Negative feedback optical amplification scheme, which has the key advantages of reducing bit error rate and waveform reshaping at the output, was employed in this optical triode. This scheme utilizes an input signal and a negative feedback signal (a signal with reverse intensity to the input) and they were fed together into the optical amplifier. Manipulating the intensity of negative feedback signal enabled the noise suppression effect to be optimized and the outputs recorded improvements in bit error rate (BER) and also undergone waveform reshaping shown by the eye-pattern. In negative feedback optical amplifier, the negative feedback signal and input signal were fed into the SOA. However, due to XGM mechanism, there is a setback in which both signals could not be simultaneously fed. Therefore, by using an optical delay, negative feedback timing was manipulated and we investigate timing characteristics of negative feedback optical amplifier with BER and eye-pattern waveforms at 10 Gb/s.

The Fifth Generation (5G) cell systems are imminent. The 5G grant higher information exchange limit constrain than the fourth period supporting broadband. The 5G will support ultra-strong device to-device and gigantic machine form correspondence. For laying out the 5G organizes new coding designs are displayed. The coding plans are Low Density Parity Check (LDPC), Low Density Symbol Check (LDSC). The coding plan, LDPC is utilized for information and polar codes for control data. What’s more, another coding plan LDSC is used to check a tiny bit at a time investigation. These coding plans are utilized for blunder adjustment and enhanced information rates. Inside the paper, proposes an estimation technique for a low Bit Error Rate (BER) of LDSC codes. The execution of Sum Product Algorithm (SPA) inside LDSC decoder is portrayed in this paper. The redress term is utilized to enhance the deciphering execution of min whole calculation. For LDSC decoder, BER diminishes with increment in the Signal to Noise Ratio (SNR).

For a multi mode fiber optical link, a high speed silicon photonics receiver based on a highly alignment tolerant vertically illuminated germanium photodiode was developed. The germanium photodiode has 20 GHz bandwidth and responsivity of 0.5 A/W with highly alignment tolerance for passive optical assembly. The receiver achieves 25 Gbps error free operation after 100 m multi mode fiber transmission.

In this paper, we propose a low-complexity peak-to-average power ratio (PAPR) reduction scheme that combines both multi-band (MB)-Hadamard precoding and clipping for the optical orthogonal frequency division multiplexing (OFDM) systems. Approximations of PAPR distribution for baseband OFDM signals are analyzed and the effective signal-to-noise ratio (SNR) of the whole transmission link considering both the clipping and quantization noise are presented. After that, the MB-Hadamard precoding is adopted to compresses the peak signals, minimizing the contaminating influence of signal distortions in subsequent clipping operations. In addition, the received SNRs and bit error rate (BER) are calculated theoretically for each split sub-band. The 50-m step-index polymer optical fiber (POF) transmission is adopted as a special case to both evaluate the system performance and then compare the proposed scheme with other well-known PAPR reduction techniques. With this scheme, the PAPR is reduced effectively and the system’s BER performance is improved significantly. The results show that the proposed scheme with appropriate number of sub-bands precoding provides favorable trade-offs among PAPR reduction, power spectral density, transmission rate, BER, and computational complexity, which demonstrates its feasibility and validity.

In this work, resource allocation of Cooperative Power Domain Non-Orthogonal Multiple Access (PD-NOMA) with energy harvesting technique using Multiple Input Single Output (MISO) is examined. This paper focuses on improvement of bit error rate (BER), spectral efficiency and capacity compared to conventional Non-Orthogonal Multiple Access (NOMA). Two users scenario is considered, where an user is near to the base station (BS) while the other one is far away from the base station. As both users with different power levels exist in the same spectrum, co-channel interference is inevitable. To alleviate this, an interference cancellation technique known as Successive Interference Cancellation (SIC) is used. The simulation results of cooperative NOMA with energy harvesting are compared with conventional NOMA and it can be inferred that cooperative NOMA performance is better than NOMA.

Capacity and signal quality can be improved in mobile radio systems by designing digital receivers with interference mitigation capability. In this paper, coherent MLSE receivers based on successive cancellation of adjacent channel interference in FDMA/TDMA mobile radio systems are developed. The proposed technique requires estimation of impulse response of the desired and adjacent channels, these are obtained via a novel approach employing pulse shaping information and band extrapolation. The receiver is simulated for the GSM digital cellular system under Rayleigh and Rician fading. The results show substantial improvements in bit error rate in interference limited environments.