Simulative analysis of carrier suppressed return to zero based symmetrical compensated optical link

This paper has deeply simulated the different configurations of pre, post, and symmetric dispersion compensation-based dispersion compensated fiber (DCF), Gaussian optic filter (GOF), and fiber Bragg grating. Output power, signal quality factor, and signal gain are the performance parameters in this study for the complete comparison for the proposed techniques for dispersion compensation. It is observed that FBG has presented the best performance parameters optimization in compared to other compensation techniques for different configurations of compensation. The FBG dispersion compensation technique is the key solution for dispersion compensation in compared with other compensation techniques that are comparatively as in previous section. It is observed that the FBG is the best dispersion compensation technique and change its location, and length, apodization, and chirp functions, to obtain the best performance of FBG and give the best quality factor, output power, and gain, FBG can be employed in different categories such as post compensation, pre compensation, and symmetric compensation with different FBG lengths, apodization, and chirp functions.

Design and comparative performance evaluation of chirped FBG dispersion compensation with DCF technique for DWDM optical transmission systems

This study discusses dispersion as a key issue influencing the performance of optical fiber communication technology. Poor bit rate, pulse broadening, and transmission distance restrictions are the outcomes. The dispersion correction method frequently employs fiber with dispersion compensation (DCF) and fiber Bragg grating (FBG). A model transmission system has been analyzed in light of numerous parameters using the Opti System 20.0 simulator. The DCF and FBG dispersion compensation methods are two that have been proposed. The Q-factor, BER, and eye height measured at the receiver end will be utilized as three metrics to describe the results of the two dispersion-correcting strategies. Additionally, the system's transmission performance will vary as a result of varied compensatory approaches. The DCF approach does not significantly increase system performance compared to the compensation technique. In addition, the properties of the optical fiber used for transmission in the system affect the characteristics of the FBG and the fiber used for the compensating process. It has been demonstrated that post-compensation, followed by symmetrical compensation, produces the best result. In addition, the transmission performance of the system with different compensation methods will be different, and the compensation technique will improve the system performance much better than the DCF technique. Moreover, the characteristics of the FBG and the fiber that is used for the compensation process depend on the characteristics of the optical fiber that is used for the transmission in system. It is shown that the symmetrical compensation performance is the best. Due to the nonlinear nature of propagation, system performance depends on power levels, followed by post-compensation.

A novel technique for dispersion compensation is presented. Based on the theoretical analysis, an ideal instance of characteristics of linear chirped fiber Bragg grating (CFBG) with 11 thermal heads and a laboratory instance of characteristics of the CFBG with 5 thermal heads varies with different temperature is shown. They are analyzed at room temperature with variation of the decrease from 3°C to -3°C and the increase from -2°C to 2°C. According to the results of the simulations based on theoretical analysis, the change of micro-heaters temperature will induce the change of grating temperature, and then change the Bragg wavelength, delay and delay slope of the CFBG. Further more, a material experiment is presented. These results show that if the temperature controller is good enough, we will be able to limit the temperature from 0°C to 4°C and we will receive some random dispersion values from -2608.2ps/nm to - 2835.6ps/nm. Therefore, this dispersion compensator can compensate the survival dispersion completely and can be applied to the long-distance transmission and the optical communication system.

The efficient and accurate evaluation of the transmission performance of high-capacity optical communication systems has always attracted significant research attentions. The enhanced Gaussian noise (EGN) model is considered as an excellent solution to predict the system performance taking into account linear and nonlinear transmission impairments. Since the conventional form of the EGN model is complicated and intractable for a fast computation, the closed-form simplification has been regarded as a direction to significantly reduce the computational complexity. However, the accuracy of such a closed-form EGN model becomes a main concern in the application of ultra-wideband optical communication systems. In this work, we have investigated the accuracy of the closed-form EGN model for ultra-wideband optical fiber communication systems, where the performance of the system using electronic dispersion compensation, multi-channel nonlinearity compensation and full-field nonlinearity compensation has been evaluated in terms of symbol rate, number of channels and signal power. Our work will provide an insight on the application of the EGN model in next-generation ultra-wideband long-haul optical fiber communication networks.

Fiber optic communication systems (FOCSs) have attained a lot of attention by revolutionizing the telecommunication industry and offering new possibilities with the technical advancements in state-of-the-art high speed digital electronics. Advanced modulation formats make use of the phase, amplitude, and polarization of the optical signals at the same time to provide high spectral efficiency as compared with 1 bit/s/Hz for the intensity modulation direct detection system (IMDD), but are highly prone to transmission impairments. Thus, the effects that add up to the optical fiber impairments such as optical fiber chromatic dispersion (OFCD), polarization model dispersion (PMD), and phase offset and noise (POaN) need to be addressed at the receiver side. The development of components and algorithms to minimize these effects in next generation FOCSs with 100 Gbps data rate and beyond with long-haul transmission is still a challenging issue. In this paper, digital signal processing- (DSP-) assisted dispersion and nonlinear compensation techniques are presented to compensate for physical layer impairments including OFCD, PMD, and POaN. The simulations are performed considering Dual Polarization- (DP-) QPSK modulation format to achieve two-fold data rate to achieve spectral efficiency of 3.28 bits/s/Hz by making use of the polarization diversity and system performance is investigated in terms of bit error rate (BER), constellation diagrams, and quality factor (Q-factor) for different values of optical signal-to-noise ratio (OSNR), launch power (PL), and fiber length.

Bit error rate (BER) performances of DPSK are researched for space uplink optical communication system. Considering further phase fluctuation effect based on the traditional atmospheric turbulence model, BER performance versus transmission power, zenith angle, frequency deviation, divergence angle and transmission diameter are discussed for different wavelengths. Simulations, especially, indicate that considering the phase fluctuation effect, BER performance is sensitive for low frequency deviation. It also confirms that wavelength of 1550nm on communication system is still a good choice for the better BER performance. This work is helpful for enhancing transmission quality and the design of space optical communication system.

Residual IQ skew in a coherent transmitter severely degrades the performance of long-haul coherent optical communication systems. The impairment is particularly detrimental for a high baud-rate system using quadrature amplitude modulation (QAM). Furthermore, Nyquist pulse shaping increases the spectral efficiency for WDM systems. However, sharp roll-off of Nyquist pulse shaping further reduces the tolerance to residual IQ skew. Thus, certain trade-offs between spectral efficiency and roll-off factor should be made to improve the tolerance of residual IQ skew. We experimentally studied this trade-off and determined the optimal roll-off factor, channel spacing, receiver bandwidth, and equalizer length. The results serve as a guideline for high baud-rate coherent WDM systems.

Clouds are key driver in the performance of free space optical communication (FSOC) systems. Clouds are composed of liquid water and/or ice crystals and depending on the physical thickness can produce atmospheric fades easily exceeding 10 dB. In these more common cases, impacts on FSOC systems may be severe. On the other hand, there are times when cloud fades may be as low as 1 or 2 dB as a result of thin, ice crystal based cirrus clouds. In these cases, the impacts on FSOC communication collectors may be limited. The ability to characterize the distribution and frequency of clouds are critical in order to understand and predict atmospheric impacts. A cloud detection system has been developed and applied to produce high resolution climatologies in order to investigate these impacts. The cloud detection system uses geostationary, multi-spectral satellite imagery at horizontal resolutions up to one kilometer and temporal resolutions up to fifteen minutes. Multispectral imagery from the visible wavelengths through the longwave infrared is used to produce individual cloud tests which are combined to produce a composite cloud analysis. The result represents a high spatial and temporal resolution climatology that can be used to derive accurate Cloud Free Line of Sight (CFLOS) statistics in order to quantify atmospheric effects on optical communication systems. The Lasercom Network Optimization Tool (LNOT) is used along with a mission CONOPS and the cloud database to find configuration of geographically diverse ground sites which provide a high availability system.

Elastic optical networks (EONs) have provision long transmission reach (TR) and high spectral-efficiency (SE). Hence, compared to fixed-grid optical networks, in EONs, managing resources and addressing network design poses complex challenges. In this work, we formulate a link-based mixed integer linear program (MILP) model which considers quality of transmission (QoT) while determining the route, modulation format/level (MF/ML) and spectrum allocation (SA) for every request. To improve SE, model chooses the highest ML; however, when QoT is considered, TR of path with highest ML is very limited. Hence, model finds trade-off between ML, number of required frequency slots (FSs), and TR, with the objective of minimising required amount of network FSs so as to admit all requests. Finally, we evaluate and analyse model's performance and show that for simplicity, existing schemes impractically assume single MF (i.e., higher SE and ML) compared to fixed-grid networks, thereby ignoring the flexible nature of EONs.

This study investigates the effects of polarization mode dispersion (PMD) on high-speed multimode fiber (MMF) optical communication systems, focusing on how differential group delay (DGD) and environmental conditions such as temperature and humidity influence signal quality. The research was conducted in Abuja, Nigeria, using two modulation formats—non-return-to-zero (NRZ) and quadrature amplitude modulation (QAM). Experimental measurements were carried out over fiber lengths ranging from 1 km to 38 km, and data rates from 15 Gbps to 240 Gbps. Key performance metrics such as bit error rate (BER), jitter, and signal-to-noise ratio (SNR) were analyzed in relation to DGD under varying environmental conditions. Results showed that DGD increased from 0.136 ps to 2.78 ps for NRZ and from 0.058 ps to 2.24 ps for QAM across the tested fiber lengths. Corresponding BER values for NRZ ranged from 1.18 × 10-7 to 1.35 × 10-7, while QAM showed slightly better performance with BER values between 1.18 × 10-7 and 1.29 × 10-7. Jitter rose from 4.26 ps to 31.20 ps in NRZ and from 4 ps to 33.54 ps in QAM. SNR values declined as DGD increased, with NRZ dropping from 34.59 dB to 54.56 dB and QAM from 34.83 dB to 52.90 dB. Environmental factors also played a role; temperature increases from 28.34°C to 29.90°C and humidity from 53.1% to 59.5% led to significant increases in DGD. The findings confirm that PMD, though less dominant in MMF than modal dispersion, still significantly affects signal quality in long-distance and high-speed MMF systems. QAM demonstrated greater resilience to PMD compared to NRZ. This study highlights the need for effective dispersion management and modulation format optimization in designing robust optical networks for environmentally dynamic regions like Abuja.

Timing jitter dependence on data format for ideal dispersion compensated 10 Gbps optical communication systems

For this research article, we have completed the comparative performance analysis of 128 × 40 Gbps DWDM long-haul system for the ultra-transmission capacity of 5.12 Tbps using CSRZ modulation format under the impact of Kerr’s nonlinearities with symmetrical, post and pre dispersion compensation techniques. The BER, Q-factor values and eye-diagrams are considered as performance metrics for the different power levels ranging from −4 to 8 dBm and various transmission distances with the increment of 2400 km. We have used Gaussian filters (GFs) before multiplexing and after de-multiplexing for ensuring channel separation to evade the inter-symbol interference and cross-talk. The graphical performance analysis of the proposed system has also been made with the above mentioned compensation techniques at 4, 6 and 8 dBm input powers using DCF at 50 GHz frequency spacing for the optimization of the used format. It is observed that overall, symmetrical compensation gave better-quality performance at all the power levels in comparison to pre and post schemes. Due to narrow optical spectrum of CSRZ format, the proposed system has shown consistency, resilience and toughness against the bottlenecks appeared as dispersion and nonlinearities. It has supported the transmission distance of 19,200 km at 6 dBm optimum power for symmetrical compensation with BER of 8.65E-13 against Q-factor value of 7.00 as compared to pre compensation for 14,400 km at BER of 2.28E-13 with Q-factor of 7.18 whereas post compensation technique have shown a transmission distance of 16,800 km at 8 dBm optimum launched power with BER of 1.63E-12 and Q-factor value of 6.92.

Nowadays, the coherent optical communication system plays an important role in communication field because of large capability and bandwidth. A coherent optical communication, based on high-order modulation and digital signal processing technologies, consists of optical transmitters, optical fiber lines, optical amplifiers and optical receivers. In the high-speed coherent optical communication system, the phase noise from the transmitter laser and the local oscillator laser can significantly degrade the performance of the signal transmission and detection, especially for the systems using high-order modulation format, such as m-ary phase shift keying (mPSK) and m-ary quadrature amplitude modulation (m-QAM). Therefore, investigations on laser phase noise compensation algorithm based on digital signal processing technologies has become more and more significant. In this work, a multi-ring carrier phase recovery algorithm is developed for compensating the laser phase noise in optical fiber communication systems using high-order modulation formats. Degradations on the performance of communication systems due to the laser phase noise have been investigated. The system performance using the proposed algorithm and the conventional Viterbi-Viterbi algorithm were also evaluated in 9-channel and 15- channel, 32-Gbaud, Nyquist-spaced QPSK, 16-QAM, 64-QAM and 256-QAM coherent transmission systems with considering the impact of the laser phase noise. It is found that the phase noise leads to stricter constraints on the linewidths of transmitter-side and receiver-side lasers, and it can greatly degrade the achievable information rates in communication systems. Besides, compared to the conventional Viterbi-Viterbi algorithm, which is usually applied in the QPSK system, our proposed algorithm can also well mitigate the laser phase noise in 16-QAM, 64-QAM and 256-QAM optical communication systems.
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Optical networks form an integral part of the world-wide communication infrastructure and nowadays over 95% of data traffic is carried over fibres. Erbium-doped fibre amplifiers (EDFAs) and Raman amplifiers have made it possible to extend the usable fibre bandwidth to increase the achievable capacity of optical communications in past decades to meet the ever-growing information rate demands. However, these amplification technologies are now viewed as limiting the accessible optical spectrum to ~5 THz and ~10 - 15 THz, respectively. Currently, the presence of Kerr effects in fibre channels has been largely regarded as the major bottleneck for enhancing achievable information rates of optical communications. Signal performance degradations due to fibre nonlinearities are more severe in the systems utilising larger transmission bandwidths, closer channel spacing and higher-order modulation formats. In this work, we will study the impact and compensation of Kerr effects to analyse the performance of long-haul optical fibre communication systems using EDFAs and Raman amplifiers. Achievable information rates of such ultra-wideband optical transmission systems will be discussed considering nonlinearity compensation and probabilistic shaping techniques.