Outage Capacity for the Optical MIMO Channel

MIMO processing techniques in fiber optical communications have been proposed as a promising approach to meet increasing demand for information throughput. In this context, the multiple channels correspond to the multiple modes and/or multiple cores in the fiber. In this paper we characterize the distribution of the mutual information with Gaussian input in a simple channel model for this system. Assuming significant cross talk between cores, negligible backscattering and near-lossless propagation in the fiber, we model the transmission channel as a random complex unitary matrix. The loss in the transmission may be parameterized by a number of unutilized channels in the fiber. We analyze the system in a dual fashion. First, we evaluate a closed-form expression for the outage probability, which is handy for small matrices. We also apply the asymptotic approach, in particular the Coulomb gas method from statistical mechanics, to obtain closed-form results for the ergodic mutual information, its variance as well as the outage probability for Gaussian input in the limit of large number of cores/modes. By comparing our analytic results to simulations, we see that, despite the fact that this method is nominally valid for large number of modes, our method is quite accurate even for small to modest number of channels.Comment: Revised version includes more details, proofs and a closed-form expression for the outage probabilit

Transmitting audio via fiber optics under nonlinear effects and optimized tuning parameters based on Co-simulation of matlab and optisystemTM

Limitations of conventional wires such as copper wires are causing dispersion and distortion of the message signal for long distances communication especially for the wide bandwidths. The ability of fiber optic to overcome this problem is making it a dominant transmission medium. Despite of this major positive attribute of optic fibers, there is still a downside for using the fiber optic communication; that is the nonlinearity problem especially at the very high frequency bandwidth. For the first time, a desigen of an audio signal is suggested and executed in MatLab with an integration with OptiSystemTM software to discuss and solve this issu. The audio signal is then transmitted in different shapes of modulation signals (NRZ, RZ & RC) for different distances (100 km & 75 km) via a fiber optic media to be received in a receiving part of the simulated system. Three tests are used to do so. The first is the Quality-factor (Q-Factor) against the received power, second test is eye diagram performance and finally is the measuring of the amplitude of output (received) signal for each modulation signal shape using the Oscilloscope Visualizer. The NZR modulation signal was found to be the best one of the three used signals’ types in all three tests. The Q-factor for NRZ pulse shape (=12) was higher than that for RZ (=10) and RC (=8) for a 100 km distance at the same received power level

Mode division multiplexing zero forcing equalisation scheme using LU factorization

Optical networks is considered as the main backbone networks that handled the Internet traffic worldwide. Currently, the Internet traffic has had huge annual growth due to the increment in connected devices. At this rate, it is believed that the current technology in optical network will not able to handle this growth in the near future. Till recently, multiplexing techniques in the optical communication rely on modulation techniques where polarization, amplitude and frequency of the signal are used as the main data carrier. In these techniques, light modes are considered as an undesired effect causing modal dispersion. In contrast, mode division multiplexing (MDM) was introduced as a multiplexing approach which relies on the utilization of the light modes for the benefit of increasing the capacity-distance product of the optical network. As per any new technology, it is still facing a lot of problems preventing it from being commercially standardized and used. One of the main MDM issues is the mode coupling, which is an inventible phenomena occurs when the energy of one mode transfers to another mode during their propagation throughout the optical fibre causes inter-symbol interference (ISI), increasing the bit error rate (BER) and reducing the overall system performance. Different equalization schemes have been proposed so far attempting to mitigate the effect of mode coupling on the MDM optical signal. However, they suffer from high computational complexity and rely on training signals in estimating the optical channel which increases the overhead payload. These technique mainly rely on Least Mean Squared (LMS) and Recursive Least Squared (RLS) algorithms. The purpose of this study is to introduce a Zero Forcing LU-based equalization scheme for MDM. Previous research in the radio domain on multiple-input multiple output (MIMO) and orthogonal frequency division multiplexing (OFDM) demonstrated that zero forcing schemes have low computational complexity compared to current schemes as they equalize the signal without training signals, thus reducing the overhead payload. All of the previous points motivate the work of this study to adapt this approach in optical communications. The study adopts the four stages of the Design Research Methodology (DRM). The initial data was collected from the optical simulator, processed and used to derive the transfer function (H) of the system. Then it was used to develop the equalization scheme in MATLAB. The experimentation on Zero Forcing LU based equalization scheme shows O(N) complexity which is lower than RLS which has O(N2) and faster than LMS, in fact, LMS needs an average of 0.0126 seconds to process the signal while ZF LU-based needs 0.0029 seconds only. On the other hand, the proposed equalization reduces the time delay spread of the channel, resulting three times increment in the capacity of the MDM channel and even lower computational complexity. The main contribution of this study is the reduction of the computational complexity of the previous equalization schemes in MDM. Applying this scheme in real MDM systems can produce more cost effective and smaller digital signal processing (DSP) parts for MDM equipment and can accelerate the work on the standardization of MDM for being commercially used as a multiplexing technique for optical communication networks

Robustness of Modulation Formats Technique to Four Wave Mixing Crosstalk Under 80 Gbps Data Rate.

يعد الاختلاط بأربع موجات في الألياف الضوئية تأثيرًا غير مرغوب فيه لنظام إرسال بصري يمكن أن يتسبب في وجود قيود شديدة في مضاعفة تقسيم الطول الموجي ويقلل من أداء النظام. في هذا البحث، تم التحقيق في الكثافة الطبيعية لتعديل متانة RZ ومساواة التعديل الثنائي-العودة-صفر. بالإضافة إلى ذلك، تم تقييم أداء النظام تحت تأثير تباين طول الألياف تحت تأثير معدل بيانات 80 جيجابت في الثانية لكلا النوعين من تنسيق التشكيل. أظهرت النتائج أن التشكيل RZ يقدم الحد الأدنى من القدرة (-54) ديسيبل عند طول الألياف (70) كم، في حين يوفر قدرة (-44) ديسيبل في نفس طول الألياف بالضبط ، على المدى الزمني لأداء النظام عند القناة 4، لوحظ أدنى معدل BER في التشكيل RZ العادي الذي يساوي 2.27-10 - 43 عند (35.31) dBm القدرة المستقبلة. ومع ذلك، كان معدل الخطأ في البتات من 4.98 إلى 10-15 في نفس القدرة والقناة المستقبلة، بوجود نسق التشكيل ويكشف هذا البحث عن زيادة التقليل RZFour wave mixing (FWM) in optical fibers is an undesirable effect to an optical transmission system that can cause a severe limitation in the wavelength division multiplexing (WDM) and reduces the system performance. Within this paper, the normal intensity of RZ robustness modulation and the Modified-Duobinary-Return–Zero modulation (MDRZ) on FWM was investigated. In addition, the performance of the system under the fiber length variation effect was evaluated under the impact of (80) Gbps data rate for both types of modulation format. The results showed that the RZ modulation introduces a minimum (FWM) power of (-54) dBm at (70) kms fiber length, while MDRZ offers FWM power of (-44) dBm at the exactly same fiber length, In-term of the performance of the system at channel 4, a minimum BER was noticed in normal RZ modulation which equals to   2.27´10 - 43 at (-35.31) dBm received power. However, the BER was 4.98´10-15 at the same received power and channel, in the existence of MDRZ modulation format. The finding reveals the progress of RZ modulation in reducing the FWM crosstalk and enhances the WDM system performance even with the impact of high data rates

Extreme short wavelength operation (1.65 - 1.7 µm) of silica-based thulium-doped fiber amplifier

We report the first demonstration of silica-based thulium-doped fiber amplifier (TDFA) working in the 1.65 - 1.7 µm waveband. Up to 29 dB small signal gain and noise figure as low as 6.5 dB are achieved

Fiber optics communication failure modes

This report examines fiber optic cables and their ability to transmit data when exposed to fire conditions. By performing various experiments the study aims to widen the knowledge base in an area that at the moment is scarce in information. Literary studies of standards connected to fiber optic cables and their application in nuclear power plants are studied as well as previous work done in the field. By compering experimental results, previous work and standards conclusions are drawn about the use of fiber optic cables in facilities dealing with nuclear radiation