Optical Code Division Multiple Access Passive Optical Network Research Articles

An optimized architecture to reduce the impact of fiber strands in spectral/spatial optical code division multiple access passive optical networks (OCDMA-PON)

Abstract Exploitation of the spectral/spatial two dimensional optical code division multiple access (2D-OCDMA) systems in passive optical networks (PONs) is not explored extensively due to the fact spatial encoding requires deployment of multiple star couplers in the topology where each coupler is connected to different ends of either transmitter or receiver nodes. As a result, this scheme is not suitable for PON applications because it requires a significant increase in the amount of fiber deployment within the network along with the complexity of implementation to deploy the required star couplers. To deploy spectral/spatial OCDMA systems at PON and reduce the impact of fiber strands, this work proposes and investigates an optimized architecture of 2D-OCDMA for PONs based on enhanced multi-diagonal (EMD) code. Spectral/spatial encoding technique is used to develop 2D-EMD coding algorithm from the existing 1D-EMD scheme. This operation elevates orthogonality between the adjacent codes and supports high capacity through superior noise mitigation at the receiving end. A complete system architecture is developed and implemented in an excessively used software for optical networks implementation and analysis called Optisystem, for analysis under different performance parameters of PON. It is observed that the proposed system provides better performance in terms of transmission capacity, and cardinality, in comparison with existing 1D-EMD code and other 2D-OCDMA counterparts. Analysis shows that for an agreeable BER of 10 - 9 the proposed system can support 192 subscribers each communicating at 2 Gbps of data over 25 km single mode fiber. In terms of capital expenditure (CAPEX), four times cost saving per user is achieved for proposed architecture (PA) over conventional architecture (CA) for nearly similar performance.

Design and Implementation of Two-Dimensional Enhanced Multi-diagonal Code for High Cardinality OCDMA-PON

This paper proposes the design of a novel two-dimensional enhanced multi-diagonal (2D-EMD) code along with the implementation of corresponding architecture for incoherent optical code division multiple access passive optical network (OCDMA-PON). The proposed algorithm is derived by using spatial coding as second dimension in the existing 1D-EMD code to elevate orthogonality within adjacent codes and minimize the interference of subscribers simultaneously accessing the medium. Performance of the proposed 2D-EMD OCDMA system is analyzed through Gaussian approximation and simulation analysis for an agreeable bit error rate (BER) of $$10^{-9}$$ . Analytic analysis shows that the proposed 2D-EMD OCDMA system support more subscribers in comparison with existing systems based on 2D diluted-perfect difference (2D-DPD) and diagonal eigenvalue unity (DEU) codes. Cardinality of the proposed setup surpasses 2D-DPD and 2D-DEU by 5 and 1.8 times for an acceptable BER of $$10^{-9}$$ . Moreover, the optimal communication requirement is satisfied by 2D-EMD system with lowest effective source power of $$-27$$ dBm at 622 Mbps of data. Simulation analysis through a highly recognized software called Optisystem also validates the mathematical analysis and shows that the proposed system can accommodate large number of subscribers at high data rates. Both analytical and simulation analysis proves that the proposed system is able to support next generation PONs.

On the performance of OCDMA/SDM PON based on FSO under atmospheric turbulence and pointing errors

This paper proposes and analyzes an optical code-division multiple-access (OCDMA) network based on free-space optical (FSO) links for broadband access provisioning in areas where laying down optical fiber is difficult or even impossible. Spectral-amplitude coding (SAC) category generated by a compact encoder is adopted as a coding scheme with binary ON-OFF keying (OOK) modulation and direct detection. Moreover, we employ spatial multiplexing scheme to increase the capacity of the proposed network by exploiting the unused already generated (by compact encoder) codewords at a certain acceptable bit error rate (BER) level. A closed-form average BER expression is derived under the joint impact of both turbulence-induced fading modeled by the Gamma-Gamma (ΓΓ) distribution and misalignment-induced fading, in the presence of beat noise, shot noise, and thermal noise. In addition, the data link layer performance modeled by Markov chain is evaluated in terms of achieved throughput and average packet delay by considering the effects of atmospheric turbulence and pointing errors. Our results show that both the atmospheric turbulence and the pointing errors impose a detrimental impact on the achievable throughput and average delay of FSO-based OCDMA passive optical network (PON).

Reducing Inter-Core Crosstalk Impact via Code-Interleaving and Bipolar 2-PPM for Core-Multiplexed SAC OCDMA PON

Inter-core crosstalk (XT), caused by closely spaced cores, is the principal challenging issue of implementing multicore fiber (MCF)-based optical networks as it limits the network performance severely. In this paper, we propose and demonstrate using bipolar M-ary pulse position modulation (PPM) signaling in conjunction with the code-interleaving (CI) technique to address the inter-core XT problem in MCF-based optical code-division multiple-access (OCDMA) passive optical networks (PONs) with spectral-amplitude coding employed as the coding scheme. The bit error rate of the proposed network is derived based on an accurate analysis for the statistics of the decision random variables, i.e., mean and variance. The analysis accounts for inter-core XT, optical beat noise, and receiver noise. In addition, a comparison between the performance of core-multiplexed OCDMA PON adopting the newly proposed techniques, namely, unipolar on-off keying (OOK) with CI and bipolar 2-PPM with CI and that adopting unipolar OOK without CI, is presented under both data rate and average photons per bit constraints. The obtained results show that bipolar 2-PPM and CI are capable of reducing the inter-core XT impact on the performance of MCF-based OCDMA PONs. Furthermore, bipolar 2-PPM with CI outperforms other schemes in terms of the number of supportable users and energy efficiency.

Dynamic reconfigurable encryption and decryption with chaos/M-sequence mapping algorithm for secure H.264/AVC video streaming over OCDMA passive optical network

To enhance the security of H.264/AVC streaming, such as that for Internet protocol television, over a passive optical network (PON), a dynamic reconfigurable coding---decoding scheme, based on a chaotic sequence, was demonstrated and characterised by pseudo randomness and a maximal period. Compared with conventional optical code-division multiple-access (OCDMA) PONs, without providing a dynamic reconfigurable mechanism and trigger timing, a secure mechanism was generated using a proposed chaos/maximal length sequence (M-sequence) mapping algorithm and embedded in a codebook to control an electrical controller (register). Because the state of the electrical controller (register) is used by the chaos/M-sequence mapping time sequence pattern to trigger a switch matrix and then vary the M-sequence signature address code for each authorised user, the scrambling and interleaving function of the encryption scheme was implemented in the OCDMA-PON physical layer for various M-sequence signature address codes to carry individual H.264/AVC transmissions of the same channel. The proposed chaos/M-sequence mapping algorithm provided similar pseudo randomness and higher variance effectiveness compared with a general uniform distribution of the pseudo-random, autocorrelation, and cross-correlation properties of the proposed time sequence. In addition, the scrambling and interleaving efficiency was determined to be sufficiently high by the reduced peak signal-to-noise ratio of encrypted videos and the produced unidentifiable videos for unauthorised users.

Performance analysis of OCDMA PON configuration supporting multi-rate bursty traffic with retrials and QoS differentiation

An Optical Code Division Multiple Access (OCDMA) Passive Optical Network (PON) is a highly promising PON configuration, thanks to the potential of OCDMA technology in eliminating channel contention and efficiently supporting multi-rate traffic with different QoS requirements. In this paper, we provide a mathematical framework for a call-level performance analysis of an OCDMA PON that accommodates multiple service-classes of bursty traffic with retries. Blocked calls of random arrivals may immediately retry several times, by requesting less resources (number of codewords) each time, in order to be admitted for service. The bursty nature of traffic is denoted by the fact that in-service calls may alternate between transmission and no-transmission periods. Our analysis takes into account user activity and the various components of additive noise. An approximate recursive formula is derived for the efficient calculation of call-level performance measures. The proposed analytical model is further extended to assess the performance of an OCDMA PON that provides QoS differentiation, through the utilization of multiple-weight optical codes. Both proposed models are verified through simulation and found to be absolutely satisfactory. Moreover, comparison of the new models with a model without retries shows the necessity and effectiveness of the new models.

Performance Analysis of OCDMA PONs Supporting Multi-Rate Bursty Traffic

Optical Code Division Multiple Access (OCDMA) provides increased security communications with large dedicated bandwidth to end users and simplified network control. We analyse the call-level performance of an OCDMA Passive Optical Network (PON) configuration, which accommodates multiple service-classes with finite traffic source population. The considered user activity is in accordance with the bursty nature of traffic, so that calls may alternate between active (steady transmission of a burst) and passive states (no transmission at all). Parameters related to multiple access interference, additive noise, user activity and number of traffic sources are incorporated to our analysis, which is based on a two-dimensional Markov chain. An approximate recursive formula is derived for efficient calculation of call blocking probability. Furthermore, we determine the burst blocking probability; burst blocking occurs when a burst delays its returning from passive to active state. The accuracy of the model is completely satisfactory and is verified through simulation. Moreover, we reveal the consistency and necessity of the proposed model.

Discussion on Construction of OCDMA PON Address Code-(<i>F,K</i>,2) Optical Orthogonal Codes

Optical code division multiple access (OCDMA) passive optical network (PON) can find wide applications in the next optical access network. One of its key techniques of is construction of address code. Aiming at the facts that(F,K,1) optical orthogonal code (OOC) possesses good performance but capacity is small, and number of users in OCDMA PON is not very big thereafter OOC auto-correlation or cross-correlation may not be very strict,(F,K,2) OOC can be used as address codes for OCDMA PON. In this paper, the method of constructingOOC based on block design is discussed. The algorithm of construction (F,K,2) of OOC from block design is presented and simulated; several groups of(F,K,2) OOC are gained. The results show that the algorithm has good astringency and simplicity. It can construct(F,K,2) OOC effectively. It is feasible.

A new code family suitable for high-rate SAC OCDMA PONs applications

In this paper, a new code family named partitioned partial prime (PPP) code is proposed for high-rate spectral amplitude code (SAC) optical code-division multiple-access (OCDMA) passive optical networks (PONs) applications. They are derived from the well-known prime codes (PCs) and a manner of partitioning technique. To minimize in-phase cross-correlation (IPCC), we employ the partial and padding schemes. In addition, the influences of both phase-induced intensity noise (PIIN) and shot noise are further mitigated by the partition and two-code keying (TCK) schemes. The PPP code family has the property of good code balance, flexible code length, and excellent orthogonality. The numerical results show that the proposed system using PPP codes can substantially accommodate a lot of maximum and simultaneous users with high-rate transmission and low bit error rate (BER).

Demonstration of Low-Cost Uplink Transmission in a Coherent OCDMA PON Using Gain-Switched Fabry–Pérot Lasers With External Injection

We propose and demonstrate a simple and low-cost uplink transmission scheme for coherent optical code-division multiple access (OCDMA) passive optical networks (PONs), using gain-switched Fabry-Perot (GS-FP) lasers with external injection as local light sources at optical network units. Experimental results based on the two-user 1.25-Gb/s OCDMA system confirm the feasibility of this scheme. The system performance is compared with that of the OCDMA system using a conventional mode-locked laser (MLL). The auto-correlation peak to the maximum wing level (P/W) ratio is also given as the central wavelength of the GS-FP laser varies. The present low-cost scheme is highly preferable for OCDMA PON applications.

Analysis of Scalability and Performance in Passive Optical CDMA Networks

This paper proposes a novel architecture for coherent optical code-division multiple-access passive optical networks (OCDMA-PON). As optical spreading sequences, a recently introduced prime code family hereby referred to as double-padded modified prime code (DPMPC) has been employed and analyzed. The transceivers operate under homodyne dual-balanced detection scheme. For coherent modulation, binary phase-shift keying is employed where the phase is modulated by Mach-Zehnder external phase-modulator. The proposed architecture for optical network units and line terminals are also presented and analyzed. The network scalability of fiber link distances as well as bit-error rate, considering (1) fiber link noise e.g., amplifier spontaneous emission noise; (2) thermal noise; (3) photo-detectors' shot-noise; (4) relative intensity noise; and (5) mainly multiple-access interference, have been investigated. The results have indicated that this architecture can improve the network scalability, capacity and transmission performance, leading to the promising scheme for optical transport networks.

Layer 2 and 3 Contention Resolution and Radio-Over-Fiber in OCDMA PON for Transparent Optical Access in Personal Networks

In this paper, we analyze, for the first time, the eminent role of optical transparent networking in personal networks. We show how an optical access network mitigates many issues with respect to connectivity and mobility management. A concrete personal network user-scenario deduces requirements for such an architecture. A combination of passive optical network, optical code-division multiple access (OCDMA), and radio-over-fiber exhibits minimal cost and complexity because of centralized network control and management, resource sharing, and simplified network nodes. We enable transparent peer-to-peer communication between optical networking units in the OCDMA passive optical network subnet of the central office. We use, for the first time, simultaneously optical code-sense medium access control and optical code packet switching for contention resolution.

Fiber-Bragg-Grating-Based Optical Code-Division Multiple Access Passive Optical Network Using Dual-Baseband Modulation Scheme

We propose a fiber-Bragg-grating (FBG)-based optical code-division multiple access passive optical network (OCDMA-PON) using a dual-baseband modulation scheme. A mathematical model is developed to study the performance of this scheme. According to the analyzed results, this scheme can allow a tolerance of the spectral power distortion (SPD) ratio of 25% with a bit error rate (BER) of 10-9 when the modified pseudorandom noise (PN) code length is 16. Moreover, we set up a simulated system to evaluate the baseband and radio frequency (RF) band transmission characteristics. The simulation results demonstrate that our proposed OCDMA-PON can provide a cost-effective and scalable fiber-to-the-home solution.