Improvement and Mitigation of Kerr Effects on Multichannel ‎Communication Systems Using Efficient Optical Method

في هذا البحث، تم دراسة توليد طريقة التخفيف البصري لتعويض التشوهات في نقل الألياف البصرية لمسافات طويلة الناتجة عن التشتت اللوني وعدم خطية كير في الأنظمة متعددة القنوات. يتم استخدام طريقة هجينة جديدة تُعرف باسم اقتران الطور البصري (OPC) باستخدام الألياف غير الخطية مع مضخم رامان كجزء من عملية تحسين أداء أنظمة الاتصالات باستخدام إشارة أحادية النمط القياسي لوصلة الألياف أحادية الوضع بطول 800 كيلومتر. في هذا العمل، نقدم طريقتين يتم فيهما استخدام تضخيم رامان الخلفي بالتزامن مع اقتران الطور البصري لتحسين أداء ارتباط بصري يبلغ 1.728 تيرابايت / ثانية عبر ستة عشر قناة مع تباعد قناة قدره 50 جيجا هرتز. من خلال استخدام اقتران الطور البصري المتعدد، فأن أداء أنظمة نقل مضاعف تقسيم الطول الموجي الكثيف (DWDM) مع قنوات 16 × 108 جيجا بت في الثانية 8-QAM يمكن تحسينه بشكل كبير مقارنة بالأنظمة التي تحتوي إما على اقتران طور بصري واحد متوسط المدى أو بدون اقتران طور بصري. استراتيجية استخدام OPCs متعدد فعال عبر مجموعة متنوعة من وصلات الإرسال. تم تحسين العتبة غير الخطية (إشارة الطاقة المثالية) في نظام الإرسال المقترح بمقدار 4 ديسيبل عند استخدام OPCs متعدد، مقارنة بالحالة التي لا تحتوي على OPC، وبنسبة 2 ديسيبل عند استخدام OPC متوسط المدى. تظهر نتائج المحاكاة أنه بالمقارنة مع السيناريو دون استخدام نهج التعويض، تم تحسين عامل جودة الإشارة (Q)، وأداء معدل الخطأ في البت (BER)، والطول الإجمالي لوصلة النقل من خلال استخدام هذه الطريقة البصرية للتعويض غير الخطي.This paper studies the generation of an optical mitigation method for compensation of distortions in long distance fiber optic transmission caused by chromatic dispersion and the nonlinear Kerr effect in multi-channel systems. A hybrid new method known as Optical Phase Conjugation (OPC) based highly nonlinear fiber with Raman amplifier is used as part of the process of improving the performance of communication systems with an 800 km standard single mode fiber link Single Polarization Quadrature Amplitude Modulation (SP-QAM) signaling. This work presents two scenarios in which backward Raman amplification is employed in conjunction with OPC to improve the performance of an optical link of 1.728 Tb/s over sixteen channels with a channel spacing of 50 GHz. In this study, through the use of multiple OPC, the performance of dense wavelength division multiplexing (DWDM) transmission systems with 16 ×108 Gbps 8-QAM channels can be significantly improved over that of systems with either a mid-span optical phase conjugation or no optical phase conjugation. The strategy of using multiple OPCs is effective over a variety of transmission links. The nonlinear threshold in the proposed transmission system was enhanced by 4 dB when employing multiple OPCs, compared to the case with no OPC, and by 2 dB when using a mid-span OPC. The simulation results show that compared to the scenario without employing the compensation approach, the Q-factor, Bit Error Rate (BER) performance, and total length of the transmission link are all improved by utilizing this optical method of nonlinearity compensation

Performance limits in optical communications due to fiber nonlinearity

In this paper, we review the historical evolution of predictions of the performance of optical communication systems. We will describe how such predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems

Enabling Technology in Optical Fiber Communications: From Device, System to Networking

This book explores the enabling technology in optical fiber communications. It focuses on the state-of-the-art advances from fundamental theories, devices, and subsystems to networking applications as well as future perspectives of optical fiber communications. The topics cover include integrated photonics, fiber optics, fiber and free-space optical communications, and optical networking

Digital signal processing for fiber-optic communication systems

As the available bandwidth of optical fibers has been almost fully exploited, Digital Signal Processing (DSP) comes to rescue and is a critical technology underpinning the next generation advanced fiber-optic systems. Literally, it contributes two principal enforcements with respect to information communication. One is the implementation of spectrally-efficient modulation schemes, and the other is the guarantee of the recovery of information from the spectrally-efficient optical signals after channel transmission. The dissertation is dedicated to DSP techniques for the advanced fiber-optic systems. It consists of two main research topics. The first topic is about Fast-orthogonal frequency-division multiplexing (OFDM) — a variant OFDM scheme whose subcarrier spacing is half of that of conventional OFDM. The second one is about Fresnel transform with the derivation of an interesting discrete Fresnel transform (DFnT), and the proposal of orthogonal chirp-division multiplexing (OCDM), which is fundamentally underlain by the Fresnel transform. In the first part, equalization and signal recovery problems result from the halved subcarrier spacing in both double-sideband (DSB) and single-sideband (SSB) modulated Fast-OFDM systems are studied, respectively. By exploiting the relation between the multiplexing kernels of Fast-OFDM systems and Fourier transform, equalization algorithms are proposed for respective Fast-OFDM systems for information recovery. Detailed analysis is also provided. With the proposed algorithms, the DSB Fast-OFDM was experimentally implemented by intensity-modulation and direct detection in the conventional 1.55-μm and the emerging 2-μm fiber-optic systems, and the SSB Fast-OFDM was first implemented in coherent fiber-optic system with a spectral efficiency of 6 bit/s/Hz at 36 Gbps, for the first time. In the second part, Fresnel transform from optical Fresnel diffraction is studied. The discrete Fresnel transform (DFnT) is derived, as an interesting transformation that would be potentially useful for DSP. Its properties are proved. One of the attractive properties, the convolution-preservation property states that the DFnT of a circular convolution of two sequences is equal to the DFnT of either one convolving with the other. One application of DFnT is practically utilized in the proposal of OCDM. In the OCDM system, a large number of orthogonal chirped waveforms are multiplexed for high-speed communication, achieving the maximum spectral efficiency of chirp spread spectrum systems, in the same way as OFDM attains the maximum spectral efficiency of frequency-division multiplexing. Owing to the unique time-frequency properties of chirped waveforms, OCDM outperforms OFDM and single-carrier systems, and is more resilient against the noise effect, especially, when time-domain and frequency-domain distortions are severe. Experiments were carried out to validate the feasibility and advantages of the proposed OCDM systems