Code division multiplexing lightwave networks based upon optical code conversion

The performance of Sparse Optical Code Conversion (SOCC) architectures is investigated in Optical Burst Switching (OBS) networks using a hybrid technology, which apply optical code and wavelength division multiplexing. The simulation results indicate that the increase of the number of optical codes and the utilization of SOCC conversion, lead to considerable decrease of the Burst Blocking Probability and latency. In addition, this hybrid technology also improves the utilization of network resources.

The concept of a virtual optical code/wavelength path (VOCP/VWP) is introduced within the transport layer of the network. A potential solution to wavelength path (WP) allocation problems that may limit the expansion of WDM-based transport on mul-networks is demonstrated by employing optical code division multiplexing (OCDM). Key technologies of the VOC/VWP concept are both optical code and wavelength conversions. A transparent VOCP/VWP network is experimentally demonstrated in the total link lengths of 180 km with four network nodes and at a channel data rate of 10 Gb/s. In the proposed photonic network, network nodes are capable of optical code and wavelength conversions with 8.05 THz ultrawide-band operational bandwidth by supercontinuum generation. Transparency is achieved using optical 3R by clock recovery and optical time-gating.

This paper investigates the performance of optical code conversion architectures in hybrid technology using wavelength and optical code division multiplexing for optical burst switching network. An OCDM-based multigranularity optical cross-connect is used to enable and convert the optical path switching in bandwidth granularity finer than the wavelength-based path. Such an optical path switched by OCDM-based MG-OXC is capable of hybrid optical code/wavelength conversion along the path from a source to destination. Simulation results indicate that increasing the number of optical codes per wavelength and applying optical code conversion considerably decreases the burst blocking probability and latency, and also increases network throughput. In addition, the results show the advantages of are using sparse-partial optical code conversion architecture in WDM/OCDM OBS network.

An optical code-labeled router that performs packet forwarding through optical code label swapping (OCLS) based on code division multiplexing technology is proposed. It can enhance the processing speed of packets that can adapt to the growth of data and the aggregation of data service. The throughput of the router increases obviously since the optical code division multiplexing (OCDM) paths on the same wavelength can be processed in parallel. Moreover, it is attractive for its traffic control, bandwidth efficiency, protocol transparency, channel granularity, and so on.

Optical networks that support high‐speed, low‐cost communication services are required. an optical path is proposed that utilizes wavelength multiplexing technology at the path layer of transport network layers. Optical path schemes, wavelength path (WP)/virtual wavelength path (VWP) that can realize optical path networks are also proposed. Although wavelengths are a resource in optical networks, the number of wavelengths required to construct an optical path network has not been evaluated.This paper describes a method of network protection using the optical path technique that enhances network reliability and proposes a method for establishing a restoration path that restores failed active paths in both WP and VWP schemes. Proposed herein is an optical path accommodation design to establish WPs or VWPs in a physical network considering the proposed restoration method. Furthermore, optical path networks are constructed by establishing WPs or VWPs on a physical network that has a regular structure and the number of wavelengths required in the network are evaluated. This evaluation makes it clear that the VWP scheme requires fewer wavelengths than the WP scheme.

Path layer technologies play a key role in the development of a powerful and failure resilient broadband integrated services digital network (B-ISDN). The authors discuss wavelength division multiplexing/frequency division multiplexing (WDM/FDM) techniques and demonstrate that optical paths can greatly enhance the path layer capability and, therefore, network performance. It is shown that effective network failure restoration can be achieved with optical paths. The applicability of the wavelength path (WP) technique to global area networks is revealed. WPs are applied to the national backbone network example to evaluate the required number of wavelengths and to identify optical cross-connect node requirements. A new optical path concept is proposed, i.e., the virtual wavelength path (VWP). In the VWP scheme, wavelengths are assigned on a link-by-link basis. The wavelength assigned to a wavelength path has only local significance. Significant benefits of the VWP such as the simplified path accommodation design within a transmission facility network and the reduced number of wavelengths needed, are elucidated. >

Research in the field of fiber optics has, in recent times, looked at various ways of studying Optical Code Division Multiplexing (OCDM) and addressing the issues therein. The studies have examined the occurrence of increased bandwidth that results when OCDM is used for transmitting data through both modes: optical fibers and free space optical communication. However, this has not resulted in improved functioning of OCDM in the field of fiber optics. This present study attempts to improve OCDM operations by suggesting replacement of one of the circuit components in the system, the Splitter. It also shows that its usage manifests not only enhancement in OCDM performance but also plays a role in decreasing the Q-Factor while increasing the Bit Error Rate (BER) and Multiple Access Interference (MAI) in the system. The use of OCDM within different kinds of encoding is also examined in this study, leading to newer analyses and explanations. Three parameters were mainly examined for this study: Max Q-Factor, BER, and Eye Height that occurred with the use of BER analyzer in the Optiwave 7 Simulation Environment. The effectiveness of Q-Factor was investigated for varied numbers of users within 50 km, greater efficacy and distance at a fixed speed of 1GB/s. It was discovered that employment of Wavelength Division De-Multiplexing as a substitute for Splitter and WDM for combiner led to an increase to 32 users while, at the same time, showing lower BER and MAI and raised Q-Factor and distance.

We analyze the performance of fiber fault monitoring of a PON using a centralized, passive optical coding (OC) system. We develop an expression for the detected monitoring signal, study its statistics, and contrast our OC monitoring system with standard optical code division multiplexing (OCDM) data communication. We derive a new closed form lower bound expression for the interference probability, and use this to find the signal-to-interference ratio (SIR). A service provider cannot control the physical layout of homes in a coverage area; measuring performance for one network layout would be insufficient to test our proposed monitoring system. Client geographic distribution has a significant impact on the SIR. We consider five different PON geographical distributions and study their effect on OC monitoring performance. Our results show that SIR is sufficient to successfully monitor the network. In addition, we find that the uniform radial (UR) distribution, an analytically tractable distribution, gives good performance estimation and can therefore be a useful tool in characterizing performance in terms of both SIR and signal-to-noise ratio (SNR).

Evolution of the optical fiber systems is currently seeing the general acceptance of wavelength division multiplexing (WDM) as the best mechanisms in increasing the transmission capacity of fiber optics. However, there are problems associated with WDM technique such as wavelength drifts, wavelength inventory and management and stringent demultiplexing requirements that tend to either limit the system's performance or increase the cost. Also, it is difficult to construct a WDM system for a dynamic set of multiple users because of the significant amount of coordination among the nodes required for successful operation. Optical Code Division Multiplexing (OCDM) provides some solutions to the problems. This simple technique operates on a single broadband light source, thus alleviating the problems and cost of handling multiple lasers as in WDM systems. This paper elaborates the working principle of the OCDM technique and provides some proofs on its viability.

Previously, an optical code-division multiplexing (OCDM)-based network architecture was proposed to improve the wavelength utilization and to provide finer bandwidth granularities to users. By this technology, different channels using distinct optical codes (OCs) can be multiplexed onto the same wavelength, in which an OC is considered as the basic unit in lightpath provisioning. In the ideal case, multiaccess interference (MAI) inherent to the OCDM technology is assumed to be removed completely at intermediate nodes and cannot be propagated or accumulated along the lightpath. However, since no optical-electrical (O/E) or electrical-optical (E/O) conversion is allowed in transparent OCDM-based optical networks, the MAI cannot be removed completely at intermediate nodes with current all-optical regeneration techniques. As a result, the residual MAI may be propagated and accumulated along the lightpath and affect other active lightpaths carried by the same wavelength in the network. The affected active lightpaths may build unintended cycles along which the MAI is accumulated. Furthermore, this MAI keeps increasing when the lightpaths traversed by the cycle are active, which deteriorates the lightpath signal quality. Since this deterioration may eventually result in unacceptable signal quality and service disruption, the phenomenon caused by the MAI is termed as cycle attack in this paper. The explanations of the MAI propagation mechanism and the cycle attack problem are given. A depth-first search (DFS)-based algorithm is proposed to diagnose such cycle attacks under dynamic traffic conditions. The numerical results show that our DFS-based cycle attack diagnostic algorithm enables one to detect cycle attacks effectively, and the two-way resource reservation method associated with heuristic wavelength assignment is shown to mitigate the blocking performance degradation due to cycle attacks greatly with some proper wavelength and OC configuration.

We present the application of Optical Code Division Multiplexing (OCDM) techniques in order to enhance the spectral operation and detection capability of fiber Bragg grating (FBG) sensors networks even under overlapping conditions. In this paper, Optical Orthogonal Codes (OOC) are used to design FBG sensors composed of more than one reflection band. Simulation of the interaction between the encoded Gaussian-shaped sensors is presented. Signal decoding is performed in the electrical domain without requiring additional optical components by means of the autocorrelation product between the reflected spectrum and each sensor-codeword. Results illustrate the accuracy and distinction capability of the method.

This paper proposes a distinct packed-switched architecture for all-optical mesh networks. It is a transparent multi-level and multi-rate solution employing all optical flip-flop and optical code gate. It relies on duplicating and filtering packets using Optical Code Division Multiplexing technology.

This paper presents a novel packet-switched routing architecture for all-optical networks using optical code division multiplexing (OCDM). The proposed architecture accommodate OCDMA label switching to the concept of optical code gate. It achieves optical header recognition and duplicated packet filtering employing new addressing scheme and optical code gates. The latter uses an all-optical flip-flop based on a single SOA-MZI as the basic building block. Encoding and decoding of OCDMA labels are passively achieved by strain-tunable fiber Bragg gratings.

Broadcast-and-select optical code division multiplexing (OCDM) and a WDM hybrid network are presented, in which 10 Gbit/s spectrum-sliced supercontinuum (SC) binary phase shift keying (BPSK) pulse code sequences are used as multi-wavelength optical BPSK code sources.

The performance of phase encoding and decoding based on phase shift superstructured fiber Bragg grating (SSFBG) in the optical code division multiplexing (OCDM) system was investigated and analyzed. The correlation characteristics for phase shift SSFBG based en/decoder were evaluated by considering input pulse width, grating refractive index modulation amplitude and wavelength mismatch between encoder grating and decoder grating. The impact of fiber dispersion on OCDM transmission over single-mode fiber (SMF) is also estimated. The theoretical results show that the degradation of coding performance is obvious under the impact of increasing of input pulse width, encoder-decoder wavelength mismatch and fiber dispersion, and there is a contradiction between correlation property and insertion loss of SSFBG en/decoder, we need to select moderate refractive index modulation amplitude of SSFBG grating.