Group protection and LAN service scheme utilizing flexible modularization and high efficiency for metro‐access network

Abstract

In this paper, a reliable scheme based on star topology is proposed by introducing group protection. Depending on interconnecting fibers, all optical network units (ONUs) are divided into some groups and each group contains 2 ONUs.Through these groups, the network can not only realize efficient transmission of local area network service between adjacent ONUs but also provide mutual protection for ONUs in a group when distribution fibers happen to faults. By using the backup pathway, the network can further provide protections for feeder fibers when they fall in faults. With the help of the optical tunable receiver in ONU, dynamic bandwidth allocation algorithm is also supported to realize flexible bandwidth allocation in 1 group. By the subtly design, the network can realize passivity (there are no active devices in remote nodes), modularization, and scalability. By utilizing amplitude modulation, differential phase shift keying modulation and reflective semiconductor optical amplifier technology, wavelength triple reuse is also achieved. Finally, the results of simulation and performance analysis demonstrate the feasibility of the architecture.KEYWORDS group protection, high reliability, LAN, metro-access network, modularization | INTRODUCTIONWith the rapid development of real-time services, such as teleconference, telemedicine, and online education, the more efficient way of communication needs to be considered, especially for the future optical network. 1 However, direct communication among optical network units (ONUs) is not supported in the traditional optical networks. The communication information needs to be firstly transmitted to the optical line terminal (OLT) and then transmitted to the destination ONUs. This will cause some problems, for example, raising the burden of OLT and even resulting in the information congestions, taking up the bandwidth of up and downstream signals, increasing transmission delay, and so on. To solve these problems, the solutions supporting direct communications among ONUs have been proposed. 2 Meanwhile, optical metro-access network can integrate traditional metro and access layers into metro-access layer, which will meet the flattening development trend of future optical network. 3 In a short, it is becoming increasingly important to support direct communication among ONUs for metro-access network.In the support of services, the schemes supporting local area network (LAN) service can be classified into 5 categories in general: additional transceiver, utilizing upstream signals, broadcasting, virtual ring, and ONU ring. Garg et al transmit and receive LAN service together with downstream and upstream services by placing a transceiver in OLT or remote node (RN). 4 The LAN signals will be transmitted to OLT or RN from initiative ONU and next to destination ONU. Wu et al transmit LAN service through orthogonal modulation technology. 5 By utilizing the light source of upstream signals, the LAN signals are produced. Garg et al broadcast the LAN signals to all output ports of a 8 ×...

Highly Reliable Metro-Access Network Based on a Dual-Fiber Ring Architecture and Optimized Protection Mechanisms

“…This scheme can achieve network reliability of more than 99.9999%, which is superior to that of some existing schemes [9], [10], [12], [13], [15], [33], [40], [48]. Furthermore, in contrast to [11], [16], [30] and [34], the proposed scheme can support protection from more types of faults, including single-fiber faults, dual-fiber faults and multifiber faults. For instance, in [11] and [30], the network will not work when there are two fibers broken in the feeder segment.…”

“…Furthermore, in contrast to [11], [16], [30] and [34], the proposed scheme can support protection from more types of faults, including single-fiber faults, dual-fiber faults and multifiber faults. For instance, in [11] and [30], the network will not work when there are two fibers broken in the feeder segment. In addition, in [16] and [34], if two faults occur in the ring section of the network, all the nodes located between the two positions of the faults will not communicate with the CO. On the other hand, in our scheme, since the additional construction cost for the protection of the feeder segment is shared by the large number of users of the overall network [17], the optical protection approach adopted in this segment can greatly enhance the reliability performance while not needing to introduce a high extra cost for each subscriber.…”

“…There now exists a vast body of literature [9]- [13] on architectures supporting the protection of distribution sections for wavelength division multiplexing (WDM) passive optical networks (PONs) and hybrid time and wavelength division multiplexing (TWDM)-PONs. All of these schemes are based on a similar principle of utilizing the wavelength routing properties of arrayed waveguide grating (AWG) [9]- [11] or the power sharing properties of a splitter [12] [13] to select among a certain number of optical network units (ONUs) connected to each other to form a protective ring against distribution-fiber faults. Although these approaches could further improve network reliability, the existing literature on the protection of the distribution section fails to consider the possible situation that when there are more than two faults in such a protective ring, the above schemes can lead to a degradation in optical transmission performance, and all ONUs belonging to the same protective ring may even cease working, which will cause unfair failure risk sharing.…”

“…Therefore, a large and growing body of literature [9]- [13], [15], [16] supporting the protection of the feeder segment concurrently has investigated satisfying the higher reliability requirement of the next-generation optical network. Overall, these schemes focus on the similar aim of developing cost-efficient architecture based on various physical topologies to resist network failures, such as the tree topology [9]- [11], singlefiber ring topology [13], [16], and dual-fiber ring topology [12], [15]. Among them, the schemes in [12] and [15], based on the dual-fiber ring architecture, can enable flexible switching, thus providing resistance against more types of faults on the feeder segment compared to a tree or singlefiber ring architecture [17], [16].…”

“…However, much of the design of complex OSMs thus far has been merely descriptive in nature, rather than based on the development of practical engineering, and it thus lacks the realistic parameters regarding OSMs obtained from tests such as the return loss, crosstalk and switching time, which are critical for demonstrating the feasibility of a scheme. Furthermore, some proposed architectures [11], [13], [16] support wavelength remodulation schemes based on reflective semiconductor optical amplifiers (RSOAs) to enhance the wavelength efficiency and achieve colorless ONU, which could be a cost-effective scheme because of the decrease of the construction cost for each ONU and the increase of the usage efficiency of each optical channel. However, the mitigation of Rayleigh backscattering (RB) noise has failed to be considered, which is the dominant factor limiting upstream transmission in an optical network with reflective ONUs [18]- [20].…”