Optical Signal-to-noise Ratio Level Research Articles

Design and performance evaluation of a hybrid FSO-FTTx communication link utilizing UD-WDMA 1.28 Tbps data rates transmission under various weather conditions

Abstract The rapid growth of high-data-rate applications necessitates the development of new communication frameworks since bandwidth constraints for data-intensive applications hinder traditional networks and conventional microwave/radio frequency (RF) communications. This study explores a hybrid communication link that combines fiber-to-the-x (FTTx) and free-space optical (FSO) technologies, utilizing ultra-dense wavelength-division multiple access (UD-WDMA) with a channel spacing of 0.2 nm/25 GHz, under various weather conditions. Based on bit error rate (BER), optical signal-to-noise ratio (OSNR), and quality factor (QF), the performance of the suggested FSO-FTTx system was examined. The system performed well in diverse weather conditions, achieving a minimum BER of ≤10−5, QF values of 4 or higher, and OSNR levels between 10 and 20 dB. The proposed system successfully transmitted a data rate of 1.28 Tbps over 35 km in single-mode fiber (SMF), accommodating different FSO link ranges despite varying weather conditions. However, performance fluctuations were observed under adverse conditions, with attenuation ranging from 0.91 dB/km in extremely light mist to 273.39 dB/km in dense fog, impacting the FSO link range. The findings underscore the proposed hybrid system’s potential to enhance optical wireless communication for high data rates, making it promising for beyond 5G and early 6G applications.

Strain FBG-Based Sensor for Detecting Fence Intruders Using Machine Learning and Adaptive Thresholding.

This paper demonstrates an intruder detection system using a strain-based optical fiber Bragg grating (FBG), machine learning (ML), and adaptive thresholding to classify the intruder as no intruder, intruder, or wind at low levels of signal-to-noise ratio. We demonstrate the intruder detection system using a portion of a real fence manufactured and installed around one of the engineering college's gardens at King Saud University. The experimental results show that adaptive thresholding can help improve the performance of machine learning classifiers, such as linear discriminant analysis (LDA) or logistic regression algorithms in identifying an intruder's existence at low optical signal-to-noise ratio (OSNR) scenarios. The proposed method can achieve an average accuracy of 99.17% when the OSNR level is <0.5 dB.

Entirely passive remote node design and system architecture for bus topology based 80Gbps symmetrical NG-PON2

The next generation passive optical network stage 2 (NG-PON2) is a broadcast network in which a large number of optical network units (ONUs) can be served using various network topologies. In this paper, a purely passive remote node (RN) design based on fiber bragg grating (FBG) is presented for the bus topology of a high split NG-PON2 system. The performance of the proposed node has been analysed for a symmetric 80 Gbps NG-PON2 system serving 1024 ONUs in terms of bit error rate (BER) and optical signal to noise ratio (OSNR). The working of the proposed node has been explained with the optical frequency spectrums for downstream and upstream signals. The observed OSNR levels for the ONUs operating at the 1st RN is 84.8743 dB which decreases to 75.7973 dB for the ONUs connected to the 8th RN. The BER level < 10–9 for both upstream and downstream confirms the correct working of the proposed node in the NG-PON2 system.

Coherent optical WDM systems for 1.6 Tb/s Ethernet over 40 km of single-mode fiber

Abstract Two 1.6 Tb/s coherent optical wavelength division multiplexed (WDM) systems targeting inter-data center links of up to 40-km reach over conventional single-mode fiber (CSMF) on C-band are proposed and numerically analyzed: a DP-QPSK-based 16 × 112 Gb/s system and a DP-16-QAM-based 8 × 224 Gb/s system. To satisfy the metro access space, noise and power transceiver characteristics are optimized, avoiding the use of any type of optical amplification or forward-error correction (FEC) scheme. Accordingly to the current Ethernet standard, feasibility of both 28 GBd architectures is hence numerically demonstrated at a very low bit-error-ratio (BER) threshold of 1 × 10−13, uncovering power sensitivities of −26.0 and −13.5 dBm and optical signal-to-noise ratio (OSNR) sensitivities of 35 and 40 dB for the first and second architectures, respectively. Negligible transmission OSNR and power penalties with respect to the back-to-back (BtB) case are calculated, thus demonstrating the effectiveness of the utilized DSP algorithms. Our simulation work also confirms that the 16-QAM-based scheme is more demanding in terms of OSNR and transmission power specifications than the 16-channel one, requiring approximately 12 dB more power and 5 dB more OSNR level at the transmitter laser outputs, with similar requirements at the receiver end. It is also demonstrated that laser linewidths of at most 1 MHz should be specified in both architectures, that the transmitter laser characteristics play a more appreciable role than those of the receiver laser, and that the frequency offset between these two lasers should be kept below 3 GHz. Our research work leverages the use of optical coherent technology at metro network level and claims for a necessary technological upgrade to such schemes for a forthcoming 1.6 Tb/s Ethernet standard to be feasible.

Impact of in-band crosstalk and amplified spontaneous emission noise in differentially phase-shift keying signal

The relative impact of in-band crosstalk and amplified spontaneous emission (ASE) noise on a system’s performance has been investigated with a differentially phase-shift keying signal. I have first measured an ASE noise-induced penalty without any in-band crosstalk and then estimated the system’s penalty with a simple addition of the measured ASE noise-induced penalty and the calculated in-band crosstalk-induced penalty. Using this approach, the estimated penalty agreed well with a measured system penalty when the Q value was 3 or an optical signal-to-noise ratio (OSNR) of the signal was higher than 30 dB at Q=6. To estimate the system penalty with a low OSNR level at Q=6, an addition of signal-ASE and signal-in-band crosstalk beat noises were added with a weighting factor. Based on this approach, a discrepancy between the estimated and the measured penalties was reduced drastically with an OSNR of 20 dB at Q=6. However, a small discrepancy was still observed even with the weighted addition of two beat noises. Thus, I have confirmed that the effect of in-band crosstalk–in-band crosstalk beat noise should be taken into account for the proper estimation of a system penalty with an OSNR of <30 dB at Q=6.

High Granularity Multiband OFDM Virtual Carrier-Assisted Direct-Detection Metro Networks

A direct-detection metropolitan (metro) network employing multiband orthogonal frequency division multiplexing (MB-OFDM) signals (MORFEUS network) is proposed. The MORFEUS network employs virtual carriers to assist the detection of each OFDM band. It represents a cost-effective network enabling high granularity and flexibility, while requiring a reduced receiver bandwidth. The MB-OFDM signal structure and their main constraints are presented. Each MB-OFDM metro node is described and discussed, with particular attention dedicated to the blocks required to insert and extract a given OFDM band of the MB-OFDM signal. Conceptual solutions for the MORFEUS insertion and extraction blocks are also proposed and discussed. The performance of a 42.8-Gb/s MORFEUS network is evaluated through numerical simulation, and the network operation design is optimized. The impact of the optical filtering effect due to band add/drop operations is assessed as well. These studies are accomplished for systems employing band selectors (BS) with different selectivity to assess the performance tolerance to interband crosstalk and in-band amplitude distortion. The studies are performed for three MORFEUS networks, with granularity of 2-, 3-, and 4-bands. A required optical signal-to-noise ratio (OSNR) of 24 dB is demonstrated in a 240-km-long MORFEUS network without optical filtering cascade effect for a bit error ratio of $10^{-3}$. This required OSNR level is achieved for the three networks with different granularity and for the two BS analyzed after suitable optimization of the MB-OFDM system parameters. Compared with an ideal MORFEUS network employing ideal rectangular BS, the analyzed networks present an OSNR penalty not exceeding 2.5 dB. A required OSNR penalty of 1 dB due to optical filtering cascade is obtained after six nodes with band filtering, for BS with a second order super-Gaussian shape.

Enhancing the Sensitivity of Interferometer Based In-Band OSNR Monitoring by Narrow Band Filtering

We present a method to enhance the sensitivity of interferometer based techniques employed for the in-band measurement of optical signal-to-noise ratio (OSNR) in wavelength division multiplexed (WDM) optical transmission systems. With respect to conventional schemes, a narrow band filter (NBF) is added before the variable delay interferometer performing the autocorrelation measurement. The NBF is used to select within the signal spectrum only those frequencies where the signal power spectral density (PSD) is locally lower and more sensitive to noise effects. Performance monitoring of a 10 Gb/s on-off keying (OOK) non-return to zero (NRZ) signal is numerically and experimentally investigated for an OSNR level ranging from 5 dB to 25 dB. Design criteria are pointed out for the bandwidth and the detuning of the NBF with respect to the signal carrier wavelength, as well as for the delay of the interferometer, in order to maximize the system sensitivity to OSNR variations. Experimental results, achieved by using an integrated ring-resonator NBF, demonstrate that presented technique enables to effectively detect small noise variations at high OSNR levels (> 15 dB), where conventional interferometer based techniques exhibit a poor sensitivity. Moreover we demonstrate that the NBF can operate directly on the transmitted optical signal without introducing any significant perturbation, this making the presented technique suitable for in-line OSNR measurements.

Transmission of OFDM-UWB Radio Signals in IM–DD Optical Fiber Communication Systems Employing Optimized Dual Parallel Mach–Zehnder Modulators

A dual parallel Mach&#x2013;Zehnder modulator (DPMZM) used for electro-optic conversion of multi-band orthogonal frequency-division multiplexing (OFDM) ultra-wideband (UWB) radio signals in intensity modulated direct detection optical communication systems is optimized theoretically and through numerical simulation. The optimum DPMZM parameters that allow simultaneous mitigation of the second and third order distortion components created by the joint electro-optic converter and photodiode nonlinearities are identified. The corresponding minimum optical signal-to-noise ratio (OSNR) required to achieve a bit error ratio of 10&#x2212;9 is also evaluated. An analytical expression showing the relation between the optimum DPMZM parameters under extended voltage levels of the OFDM-UWB signals applied to the DPMZM is proposed and validated. It is shown that the DPMZM performance presents high robustness to deviations from the optimum DPMZM parameters identified. Additionally, it is shown that similar minimum required OSNR levels are obtained with the optimized DPMZM and when the electro-optic conversion is realized by a single MZM.

640-Gb/s Transmitter and Self-Tracked Demultiplexing Receiver Using Single Parametric Gate

We report the highest performance 640-Gb/s transmitter and receiver, based on cavity-less pulse generation and a novel sampling receiver constructed using a single fiber parametric gate capable of self-tracked 40-Gb/s tributary extraction. The performance of the transmitter and sampling receiver was measured with a 640-Gb/s return-to-zero on-off keying (RZ-OOK) signal. Error-free operation was achieved for all 16 tributaries of the 640-Gb/s input stream using the optical signal-to-noise ratio (OSNR) noise loading method. The error-free (bit-error rate (BER) =10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> ) sensitivity of the sampling receiver was measured at an OSNR level of 33.5 dB, which is only 0.5 dB away from the practically achievable detection limit.

Investigation of Some Issues of Full Optical Multimedia Networks

Deployment of optical communication technologies into the core networks has allowed improvements in the transmission characteristics. Further penetration towards the end-user customers has brought online multimedia services. Increasing demand for a quality of service and new types of multimedia services challenges current state of the art technologies and drives not only coming technological trends. Recently emerging DPSK (Differential Phase Shift Keying) format is described and impact of OSNR (Optical Signal to Noise Ratio) level and laser linewidth on its performance is investigated in the environment of Virtual Photonics simulation software. Behavior of used modulation format within WDM (Wavelength-Division Multiplexing) system is examined at four channel's WDM system.

A Distributed Optimization Approach to Constrained OSNR Problem

This paper studies constrained optical signal-to-noise ratio (OSNR) problem via a distributed optimization approach. In multi-channel optical systems, the signal over an optical link can be regarded as an interfering noise for others, which leads to OSNR degradation. Regulating the input optical power at the Source (transmitter) aims to achieve satisfactory OSNR level at the Destination (receiver) for each channel. Moreover, because all wavelength-multiplexed channels in a link share the same optical fiber, the total input power in a link has to be below the nonlinearity threshold, which corresponds to a link capacity constraint. We formulate the OSNR optimization problem as one of utility maximization with the objectives of achieving an OSNR target level for each channel while minimizing the interference and also satisfying the link capacity constraint. We derive conditions for the existence of a unique optimal solution, leading to a basis for an admission control scheme. By using a Lagrangian relaxation approach we propose two distributed update algorithms: a primal algorithm and a dual algorithm, and study their convergence properties both theoretically and numerically.

All-optical in-band OSNR monitoring at 40 Gb/s using a nonlinear optical loop mirror

We present an all-optical in-band optical signal-to-noise ratio (OSNR) monitor using a nonlinear optical loop mirror. Monitoring is enabled from the nonlinear power transfer function of the loop mirror. Experimental results are provided at 40 Gb/s for three modulation formats: nonreturn-to-zero, carrier-suppressed return-to-zero, and return-to-zero. The monitor discriminates the various OSNR levels over a dynamic range of more than 25 dB with every modulation format.

OSNR optimization in optical networks: modeling and distributed algorithms via a central cost approach

This paper addresses the problem of optical signal-to-noise ratio (OSNR) optimization in optical networks. An analytical OSNR network model is developed for a general multilink configuration, that includes the contribution of amplified spontaneous emission and crosstalk accumulation. The network OSNR optimization problem is formulated such that all channels maintain a desired individual OSNR level, while input optical power is minimized. Conditions for existence and uniqueness of the optimal solution are given. An iterative, distributed algorithm for channel power control is proposed, which is shown to converge geometrically to the optimal solution. The algorithm is valid for general network configurations, and uses only local measurements or decentralized feedback. Convergence is proved for both synchronous and asynchronous operation, which is particularly important for adaptation in a dynamic environment

Monitoring optical network performance degradation due to amplifier noise

The relationship between optical performance as monitored within a network and the end terminal optical signal-to-noise ratio (OSNR) and bit error ratio (BER) is measured for the case of performance degradation due to amplified spontaneous emission noise. Measurements on 10-Gb/s signals reveal that performance monitoring sensitivity to OSNR levels of 26 dB is sufficient for identifying degradations that impact the end terminal BER.