Wavelength Division Multiple Access Networks Research Articles

Performance analysis of modified accelerative preallocation MAC protocol for passive star-coupled WDMA networks

For the passive star-coupled wavelength-division multiple-access (WDMA) network, a modified accelerative preallocation WDMA (MAP-WDMA) media access control (MAC) protocol is proposed, which is based on AP-WDMA. To show the advantages of MAP-WDMA as an adequate MAC protocol for the network over AP-WDMA, the channel utilization, the channel-access delay, and the latency of MAP-WDMA are investigated and compared with those of AP-WDMA under various data traffic patterns, including uniform, quasi-uniform type, disconnected type, mesh type, and ring type data traffics, as well as the assumption that a given number of network stations is equal to that of channels, in other words, without channel sharing. As a result, the channel utilization of MAP-WDMA can be competitive with respect to that of AP-WDMA at the expense of insignificantly higher latency. Namely, if the number of network stations is small, MAP-WDMA provides better channel utilization for uniform, quasi-uniform-type, and disconnected-type data traffics at all data traffic loads, as well as for mesh and ring-type data traffics at low data traffic loads. Otherwise, MAP-WDMA only outperforms AP-WDMA for the first three data traffics at higher data traffic loads. In the aspect of channel-access delay, MAP-WDMA gives better performance than AP-WDMA, regardless of data traffic patterns and the number of network stations.

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.

Coherent optical CDMA (OCDMA) systems used for high-capacity optical fiber networks-system description, OTDMA comparison, and OCDMA/WDMA networking

As the wavelength resource in mainstream wavelength-division multiple-access (WDMA) systems becomes exhausted, and the bit-rate limitation within a single wavelength bandwidth is reached, alternative approaches to implementing a high-capacity optical fiber network need to be investigated. Coherent optical code-division multiple-access (OCDMA) systems, that can access many users simultaneously and asynchronously (or synchronously) across the single wavelength and same timeslot via spread spectrum techniques, are one alternative. In the longer term, the advantages of OCDMA in tandem with WDMA (OCDMA/WDMA) networks are compelling and worthy of further investigation in the goal of realising an extensive, flexible, high throughput and easily managed optical telecommunication infrastructure. In this paper, coherent OCDMA systems are introduced, and the issues of the system implementation within high-capacity optical fiber networks are discussed. A performance comparison between OCDMA and OTDMA systems is then carried out, both of them using narrow pulse laser sources. An optical fiber network utilizing coherent OCDMA techniques as one layer of a multiplexing hierarchy, in tandem with WDMA, is illustrated and a possible hybrid OCDMA/WDMA network architecture (and its performances and advantages) is described.

A 32-channel tunable receiver module for wavelength-division multiple-access networks

We report the realization of a 32-channel tunable optical receiver module for packet-switched multiwavelength computer networks. The tunable receiver consists of a planar array waveguide grating demultiplexer, photodetector array and followed by selectable receivers. The channel selection is based on sequential switching of the received optical signals in stages at the analogue level. Typical receiver sensitivity is -24 dBm at 10/sup -9/, using a 700-Mb/s nonreturn-to-zero (NRZ) pseudorandom binary sequence (PRBS). The channel switching time is /spl sim/40 ns.

Demonstration of gigabit WDMA networks using parallelly processed subcarrier hopping pilot-tone (P/sup 3/) signaling technique

An extremely short header transmission and processing time in a gigabit wavelength-division-multiple-access (WDMA) network has been experimentally demonstrated. This was achieved by using parallelly processed subcarrier hopping pilot-tones in combination with an array of detectors and RF switches. The results showed that, without considering the time consumed in an arbitration circuit, the total processing time of the hopping pilot-tone headers was as short as 40 ns which is independent of the number of network nodes and data transmission rate.

Wavelength requirements of all-optical networks

All-optical networks are networks for which all data paths remain optical from input to output. With rapid development of optical technology, such networks are a viable choice for the high speed wide area networks of the future. Wavelength division multiple access (WDMA) currently provides the most mature technology for all-optical networks. The authors discuss a class of WDMA networks that are homogeneous in the sense that each node contains both an input/output port and a switch. They focus on the permutation routing problem and first, present a lower bound on the number of wavelengths required for permutation routing as a function of the size and degree of the network. They use particular topologies, including the multistage perfect shuffle, the Debruijn, and the hypercube, to find achievable upper bounds on the number of required wavelengths.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of laser direct intensity modulation index on optical beat interference in subcarrier multiplexed wavelength division multiple access networks

Degradation in carrier-to-interference ratio (CIR) due to optical beat interference (OBI) in subcarrier multiplexed wavelength division multiple Access (SCM/WDMA) networks using direct photodetection is evaluated. The subcarriers are assumed to directly intensity modulate separate lasers. A large signal model for the modulated laser light is used. The discrepancy in CIR between this model and the small signal model commonly used in the literature is important at high modulation indices (4.5 dB at about unity modulation index). This justifies the introduction of the large signal model for analyzing OBI. It is found from analytical results that OBI is lower for higher intensity modulation indices. >

Use of delegated tuning and forwarding in wavelength division multiple access networks

Proposes delegated tuning and forwarding (DTF), a new architecture for dynamically assigning wavelength channels in a broadcast star optical network. DTF exploits tunable components without making excessive demands on tuner agility by combining the tuning on demand of receivers with the forwarding of packets over a logical topology. The authors describe the control algorithms of DTF and prove some results establishing their stability and robustness. They show by simulation that DTF achieves lower hop-counts in conditions of light-to-moderate load than do DeBruijn graph networks. When a DTF network is saturated, the average number of hops in each path is only about 10% higher than the average for a DeBruijn graph network, suggesting that, even under high loads, the evolution of network topology under DTF is close to optimal. >

Lossless wide-band reflective star coupler using erbium-doped fiber amplifiers

A wide-band 64-port amplified reflective star coupler (ARSC) using eight fiber amplifiers and only four pump laser diodes is demonstrated. The loss of this ARSC can be fully compensated from 1530 mn to 1565 nm due to its double-pass amplification process. The power margin increment of 21.7 dB with the power penalty of 1.3 dB and the cross-channel power penalty of 2 dB are achieved in a 1.7 Gb/s system experiment. This ARSC technology makes the star coupler cost-effective to be used in many larger wavelength division multiple access networks. >

Performance of WDMA networks with baseband data packets and subcarrier multiplexed control channels

The use of subcarrier multiplexed control channels for wavelength-division multiple access (WDMA) networks transporting baseband data packets is investigated. The contention problem is analyzed, and general expressions are derived for the throughput of slotted and random-arrival networks with N access nodes and Q subcarriers. The throughput of the networks is significantly increased by using multiple subcarriers for control channels. >

Performance Analysis of Single-Hop Wavelength Division Multiple Access Networks

Wavelength division multiple access (WDMA) provides a way to tap the huge bandwidth of an optical fiber by simultaneously operating on multiple channels at different wavelengths, with each channel running at the speed of the electronics of an end user station. This paper presents a mathematical model which approximates WDMA networks with general hardware configurations and arbitrary traffic patterns. Packets which cannot be transmitted upon arrival are blocked (i.e., lost) immediately. We first study the case of a uniform traffic matrix and observe that, when the number of wavelengths is fewer than the number of stations, it is better to have both tunable transmitters and tunable receivers, rather than having only either one of them tunable. Furthermore, we find that only a small number of tunable transmitters and receivers per station is needed to produce performance close to the upper bound. We then construct a general traffic model and propose an iterative solution procedure. A case of hot-spot traffic is studied using this model. We find that adding more resources to the hot-spot node will help improve its performance, but only to a limited extent determined by the traffic imbalance. The match between the model and simulation results are shown to be excellent.

A wavelength division multiple access network for computer communication

A first-generation design, called Rainbow, for optical wavelength division multiaccess (WDMA) computer networks is described. The Rainbow research prototype takes the form of a direct detection, circuit-switched metropolitan-area-network (MAN) backbone consisting of 32 IBM PD/2's as gateway stations, communicating with each other at 200-Mb/s data rates and submillisecond switching times. The prototype architectural options for realizing WDMA networks are discussed, along with reasons for choosing this design point. Experimental measurements on the prototype are presented. Ways of extending this prototype to more stations, higher bit rates, and faster setup times are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>