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The focus of this work is to consolidate a review of accomplished research in the field of optical code division multiple accesses (OCDMA), to outline the state-of-the-art comparison, and to recognize the prominent trends as well as limitations. Code division multiple access (CDMA) has prospered as a vital solution for numerous applications such as cellular mobile communication-based wireless network technology and wired/wireless local area networks that include areas of unlicensed industry, medicine, and science. Due to the commercial utilization of the various advantages of CDMA, it has raised the matter of whether optical technology reliant communications provide the noteworthy advantages to optical networks as well as what are the technologies that facilitate optical chip-based (code division) networks. Aforementioned matter has been addressed in the context of the incorporation of OCDMA in the systems through several experiments of laboratory-based test-bed investigations, field trials, and simulation analysis of multiple users in the recent research works. The performance of OCDMA has an edge over wavelength division multiplexing and offers an unmatched capacity that is seen through simulations. To cater the explosive expansions in internet application, different spectral amplitude codes have been proposed till now. We present a review of the different spectral amplitude codes based on the reported works in spectral amplitude code OCDMA systems. For the purpose of state-of-the-art comparison, parameters considered are data speeds, advanced modulation formats, bit error rate, extinction ratio, decision algorithms, photonic efficiencies of photodetectors, frequency bands, signal-to-noise ratio, forward error correction, photodetector noises, etc., and simulations are carried out in similar input environments. We explore the advantages/limitations of the spectral amplitude codes, recent progress in the technology, practical works on spectral amplitude coding (SAC) throughout the world, encryption–decryption techniques, all-optical methods, literature comparison, future scope, and applications of the SAC-OCDMA codes. [ABSTRACT FROM AUTHOR]

Hybrid optical amplifiers (HOAs) are crucially important for broadband band amplification, and are widely deployed in high-capacity dense wavelength division multiplexed systems. We summarize the present state-of-the-art in this rapidly growing field. In addition, theoretical background and various inline configurations of optical amplifiers have been presented. Various issues such as gain flatness, gain bandwidth, transient effect, and crosstalk were presented in HOAs. Results show that the HOAs provide better gain flatness without using any expensive gain flattening techniques, and an acceptable range of gain, noise figure, bit error rate, and transience. [ABSTRACT FROM AUTHOR]

A module of an all-optical 2-bit comparator is analyzed and implemented using semiconductor optical amplifiers (SOAs). By employing SOA-based cross phase modulation, the optical XNOR logic is used to get an A = B output signal, where as AB and AB; logics operations are used to realize A > B and A < B output signals, respectively. All input output bit operations results along with the wide open eye diagrams are obtained. It is suggested that the proposed system would be promising in all-optical high speed networks and computing systems. [ABSTRACT FROM AUTHOR]

We propose a new optical data format based on simultaneously modulating nonreturn-to-zero and polarization-shift-keying for high-speed applications by means of efficient utilization of bandwidth. To the best of our knowledge, this article reports on the first investigation of a Raman erbium-doped fiber amplifier hybrid optical amplifier using a hybrid/orthogonal modulation technique in the scenario of 8- and 20-channel dense wavelength division multiplexed systems with high-data rates at 0.2 and 0.8 nm channel spacing, respectively. The results show that the proposed modulation format offers significant advantages in offering high-spectral efficiency values with acceptable quality factors and bit error rates. [ABSTRACT FROM AUTHOR]

We present a simple genetic algorithm implemented to perform multiparameter optimization of a Raman fiber amplifier for a 100-channel L-band dense wavelength division multiplexed system at a 25-GHz interval. The system is investigated for various cases with fixed pump frequency leading to 202.2-THz pump as the best choice with average gain above 19.5 dB. There is evidence to show that a single counterpropagating pump optimized to 588.2-mW power level and optimum Raman fiber length of 38.8 km presents a small gain variation (<2 dB) over an effective bandwidth covering 187 to 189.475 THz. The optimized configuration enabled an adequate system performance in terms of acceptable Q-factor (17 dB) and bit error rate (5.60 x 10-13). [ABSTRACT FROM AUTHOR]

Passive optical network broadcasts extensive data to subscribers. However, they are vulnerable to various security attacks. The main objective of our work is to assess the information security aspects at the physical layer of next-generation passive optical network stage 2 (NG-PON2). Our paper focuses on the security issues faced by NG-PON2, and we propose an encryption method using the all-optical exclusive-OR gate. The proposed simulation architecture of symmetric 80-Gbps NG-PON2 is based on array waveguide grating. Further, we verified the inherent security of the NG-PON2 system through an eavesdropping attempt at an optical network unit (ONU). For this, we used a key exchange mechanism using the Diffie–Hellman algorithm for sharing individual unique keys between every ONU and the optical line terminal. The simulation results show that the presented technique provides secure broadband services in the access network. The transmitted data are encrypted to ensure confidentiality on the multipoint fiber connection. We have evaluated the transmission performance of the proposed set up and achieved acceptable results in terms of Q-factor (7.12 dB) and bit error rate of (5.26 × 10 − 13). The bits in the optical domain, which are sent to the first ONU, are also compared with the received optical bits at the receiving ONU. The correct reception of the bits at the intended ONU and the inability of malicious ONUs to eavesdrop the data of other ONUs validates the scheme. [ABSTRACT FROM AUTHOR]