Fiber Optic Local Area Network Research Articles

Efficient modulation technique for optical code division multiple access networks: differential pulse position modulation

In this study, the authors study a fibre-optic local area network deploying optical code division multiple access technique with differential M-ary pulse position modulation (DPPM). The authors present the performance analysis of DPPM signalling using a double optical hardlimiter receiver structure considering the impairment caused by interference of other users. The analysis assumes a set of bit asynchronous transmitters employing generalised optical orthogonal codes for their DPPM signalling (GOOC-DPPM). Using mathematical analysis and simulations, the authors have demonstrated that GOOC-DPPM improves both frame error probability and the maximum achievable network throughput compared with M-ary PPM modulation scheme. It is also indicated that using generalised OOC codes instead of strict OOC codes in DPPM modulation can increase the number of users who can simultaneously transmit data in the network. The authors have analysed the stability of GOOC-DPPM in a multi-user system and demonstrated its stability. Moreover, the performance of the proposed scheme is evaluated when its important design parameters such as code length, code weight and multiplicity index of the modulation are changed. The findings led the authors to provide some guidelines for proper selection of these parameters to be used for efficient system design.

Research on Characteristics of Plastic Materials and Plastic Optical Fiber

Plastic materials have many uses. The plastic optical fiber with a low-cost, light weight, good flexibility, big core diameter, easy coupling, anti-electromagnetic interference and electromagnetic radiation, is used for short range communication. This paper analyzed the characteristics of plastic materials and plastic optical fiber, and proposed a novel application technology for access network. In the access network, the plastic optical fiber is used as a transmission medium, from center router to the server, and the various floors of plastic optical fiber switch to the user using plastic optical fiber connections, constitute a plastic optical fiber local area network, to realize the true meaning fiber to the home.

New Receiver Architecture Based on Optical Parallel Interference Cancellation for the Optical CDMA

Optical Code Division Multiple Access (OCDMA) is considered as the strongest candidates for the future high speed optical networks due to the large bandwidth offered by the system, Based on the vast amount of bandwidth, OCDMA systems have received much attention in fiber optic Local Area Networks where the traffic is typically bursty. However, Multiple Access Interference (MAI), which is originated from other simultaneous users, severely limits the capacity of the system. Optical Parallel Interference Cancellation (OPIC) has been used to reduce the effect of MAI. However, the usage of OPIC in OCDMA systems will increase the demand for hardware complexity which results in higher processing time and cost. The hardware complexity increases in the receiver side of OPIC when the number of transmitter (users) increases. To overcome these difficulties, an efficient method is presented in this paper called, One Stage Optical Parallel Interference Cancellation (OS-OPIC) which is based mainly on the OPIC. Optical Orthogonal Code (OOC) is adopted as a signature sequence for the performance analysis and a new expression for the error probability is derived. It is shown that, the proposed method is effective to reduce the hardware complexity, processing time and cost while maintaining the same bit error probability at the cost of increasing threshold value.

Buffer analysis with finite number of tunable receivers in WDM passive star networks

This study develops a performance model as an expansion of the receiver collision analysis presented in [I.E. Pountourakis, Performance evaluation with receiver collisions analysis in very high-speed optical fiber local area networks using passive star topology, J. Lightwave Technol. 16 (12) (1998) 2303–2310] for WDM networks. By theoretical analysis we estimate the receiver collision phenomenon and evaluate the performance measures and the rejection probability at destination for finite number of tunable receivers. Receiver collision analysis makes the performance behavior more realistic and expands the original analysis.

Quantum key distribution over an installed multimode optical fiber local area network

We have investigated the possibility of a multimode fiber link for a quantum channel. Transmission of light in an extremely underfilled mode distribution promises a single-mode-like behavior in the multimode fiber. To demonstrate the performance of the fiber link we performed quantum key distribution, on the basis of the BB84 four-state protocol, over 550 m of an installed multimode optical fiber local area network, and the quantum-bit-error rate of 1.09 percent was achieved.

Electrostatically actuated 1 × 2 micro-mechanical optic switch

A micro-opto-mechanical 1 × 2 switch has been realised using silicon oxynitride (SiON) planar waveguide technology. The operational principle of the switch is based on the mechanical deflection of a cantilever beam due to electrostatic interaction. The device concept and performance is reported. The switch is monolithically integrated on a silicon substrate and has many potential applications in fibre-optic local area networks.

Testbed for a scalable terabit optical local area network

The design of a fiber-optic local area network (LAN) demonstration system is described. A complete LAN system would consist of an array of 16 personal computers (PC's), where each PC has a network interface card (NIC) with a parallel fiber-optic datalink to a centralized optoelectronic switch core. The centralized core switches the data generated by 16 NIC's, up to 128 Gbit/s of bandwidth. The demonstrator is designed to scale to terabits of bandwidth by use of an emerging optoelectronic technology, i.e., integrated complementary metal-oxide semiconductor (CMOS) substrates with vertical-cavity surface-emitting laser (VCSEL) and photodetector optical input and output. A subset of the complete system was constructed and is operational. A prototype NIC card, with Motorola Optobus VCSEL transceivers for the optical datalinks, was constructed and is described. A prototype high-speed bipolar switch core, with statically configurable electrical positive-emitter coupled-logic 16 x 16 crossbar switches, CMOS field-programmable gate arrays, and Motorola Optobus transceivers, was constructed and is described. We successfully demonstrated the transmission of high-speed packetized data from one NIC card, through 10 m of parallel fiber ribbon and the centralized switch core, and back to the NIC. We summarize our experiences on the design and testing of our first demonstration system and our development toward a terabit switch core.

Performance evaluation of a high-speed wavelength division multiplexing/asynchronous transfer mode optical fiber local area network

This work studies the performance of a proposed high-speed optical fiber local area network based on wavelength division multiplex- ing (WDM) and asynchronous transfer mode (ATM). The design opti- mizes the usage of resources by assigning different types of traffic to two overlapping sub-networks. The WDM segment is a circuit-oriented net- work for high-speed traffic. The ATM sub-network handles control, low speed traffic and overflows of the WDM network. Each network is sup- ported by one of two types of channels. The ATM channel employs con- ventional ATM cells for all stations using a 1300-nm wavelength carrier. The WDM channel which is assigned dynamically for very high-speed applications operates at 1500 nm band. The application of an ATM net- work to handle the overflow traffic reduces blocking in the system by approximately 13% for a 32 WDM system. However, depending on the load, it may increase the delay between 5% to 30%. In addition, employ- ing an adequate queuing policy, we may reduce the blocking by 30% while increasing the delay by 5%. We may conclude that the network is more efficient handling the traffic load compared to a simple circuit switched WDM network. © 1999 Society of Photo-Optical Instrumentation Engi- neers. (S0091-3286(99)02511-8)

Performance evaluation with receiver collisions analysis in very high-speed optical fiber local area networks using passive star topology

The problem of receiver collisions in high-speed optical fiber local area networks is studied in this paper. The configuration of high-speed multichannel LAN's with wavelength division multiplexing techniques using an optical fiber bandwidth gives rise to receiver collisions phenomena. We give a detailed analysis and develop rigorous methods to examine the effect of receiver collisions in this type of multiaccess environment. The evaluations are carried out assuming Poisson arrivals and finite population and examine the throughput performance and the rejection probability at destination. Also numerical results are showing the throughput performance behavior as it compared with the protocol case without receiver collisions.

ORMA: a high-performance MAC protocol for fiber-optic LANs/MANs

Emerging B-ISDN applications are accelerating the demand for high-speed and high-performance fiber optic local and metropolitan area networks (LANs and MANs). Most of the networks proposed for such an environment are based on either a folded bus or dual unidirectional bus technology, primarily due to the unidirectional nature of the fiber optic medium, their cost effectiveness, and their ability to carry asynchronous transfer mode (ATM) cells. Consequently, the design of the medium access control (MAC) protocols is the most crucial aspect for these networks since the decisions made at this level will determine the capabilities and the hardware cost of the network. The author proposes a novel MAC-layer protocol, called Optical Reservation Multiple Access (ORMA), which is suitable for data traffic on fiber optic folded bus MANs and LANs. Its main feature is an efficient optical reservation technique to allow stations to reserve transmission slots, which is attractive for use in fiber optic networks. Unlike conventional protocols. Where reservation is mostly done using software, ORMA performs its reservation using simple and effective optical circuits. Complete descriptions of the ORMA protocol and the associated nodes are given. Then the performance of ORMA is investigated as a function of the throughput, mean packet delay, and fairness among stations using analytical and simulation results. Our protocol is shown to achieve high throughput and small transmission delays while preserving the fairness of the whole network. Moreover, it compares favorably with related state-of-the-art networks. Thus, the ORMA protocol lends itself well to future-generation high-speed MANs and LANs.

Fiber-optic subcarrier multiplexed CDMA local-area networks for subband image transmission

This paper investigates the application of subcarrier multiplexed code-division-multiple-access (CDMA) techniques to image transmission over fiber-optic local-area networks (LANs). In the hybrid scheme, CDMA is used to suppress the interference caused by the laser nonlinearity in the subcarrier multiplexing (SCM) fiber-optic communication systems. Likewise, the SCM scheme is able to increase the channel data rate of CDMA systems. This hybrid system combines the advantages of both schemes and is particularly well suited to subband coding that divides the image information into multiple parallel data streams using an analysis filter bank, each of which is transmitted via a unique subcarrier-code pair, where the spreading code and subcarrier frequency correspond to the image and one of its subbands, respectively. This hybrid scheme also allows more than one image to be transmitted and be accessed simultaneously at the same channel bandwidth, in which each image is assigned a particular spreading code added to its digital data modulating the subcarrier. After transmission, each received signal is independently recovered at a high-Q surface acoustic wave (SAW) receiver with the matching subcarrier-code pair. Other concurrent signals are rejected by the SAW. Then, all the recovered subbands are reassembled by a synthesis filter bank into a close reproduction to the original image. The image quality of subband image transmission via CDMA/SCM fiber-optic channels is evaluated and examined.

A load-controlled scheduling scheme for integrated voice-data communication on high-speed LANs/MANs

A new dynamic bandwidth-allocation (or rate-control) strategy that can be employed for integrating multimedia traffic on a class of high-speed fiber optic local and metropolitan area networks (LANs/MANs) is investigated. This new scheme is adapted from the original work by Limb on load-controlled-scheduling-of-traffic (LOCOST) mechanism, which employs channel feedback for proper distributed control operation. Although the mechanism is quite general for integrating diverse traffic types, the specific focus of this paper is on the integration of packet voice with data. The medium access control is simple, and is fully asynchronous and distributed which make it easy to implement. The necessary control functions are performed locally and independently at each data station based on a single parameter called its packet allowance, while each voice station can transmit a voice packet whenever it can. A gated global queue model is formulated to approximately analyze this system, and simulation results are also included to study the protocol's performance.

Surface-micromachined free-space fibre-optic switches

A novel 2 × 2 free-space fibre-optic switch has been fabricated using surface-micromachining technology. The switch is monolithically patterned on the Si substrate. With this approach, the switch can be made compact, light weight and low cost. In addition, it is potentially integrable with other micro-optical elements and interface electronics. The switch is attractive for fibre-optic local area network applications.

Optimal optical orthogonal code design using difference sets and projective geometry

A different approach to the design of optimal optical orthogonal codes to be used in intensity modulation-direct detection code division multiple access fiber-optic local area networks is introduced. The design method is based on the combination of the concept of difference sets and projective geometry and the designed codewords yield the best achievable correlation properties.

Synchronous fiber-optic CDMA using hard-limiter and BCH codes

In this paper, synchronons code division multiple access (S/CDMA) for fiber-optic local area networks is considered. The performance of the fiber-optic S/CDMA network with negligible thermal and shot noises is interference limited. Here we derive the bit error rate of the S/CDMA system as a function of code length and number of active users, and the performance characteristics are also discussed. Furthermore, we analyze the performance of the fiber-optic S/CDMA system with an ideal optical hard-limiter, and the error probability with error control coding is also derived. In addition, the optimization between the S/CDMA and BCH codes of a constant bandwidth system is presented. The results show that by using an ideal hard-limiter in conjunction with BCH codes in this system, the influence of interference arising from other users can be greatly reduced, and the number of active users can also be increased significantly. >

Optical CDMA via shortened optical orthogonal codes based on extended sets

A novel approach to the design of optical orthogonal codes to be used in intensity modulation-direct detection fiber-optic local area networks is used in this work. The algorithm introduced in this study is based on the extended set concept which enables the design of optical CDMA codes with best achievable correlation properties. One important advantage over existing code design methods is the fact that the code set size will be an input parameter to the design algorithm. Furthermore, the effect of shortening the code length of the generated codewords are also examined in this paper.

Performance analysis of slotted aloha protocol for optical fiber local area networks with star topology

In [1, 2] the present authors initiated the development of dynamic models for optical fiber local area networks. This is a major departure from the traditional approach of communication engineers who are used to steady state analysis based on queueing network theory. Here in this paper, theoretical analysis of the proposed model for a passive star coupler based on the Slotted ALOHA/ALOHA protocol for optical fiber local area networks is presented. The input, measured in terms of the number of user requests in each time slot, is modeled as a Poisson random process with time varying mean intensity thereby allowing time varying data traffic which closely models the real physical data flow. In contrast the traditional approach which uses a mean data traffic fails to capture the true dynamic nature of the system. Simulation and theoretical results are compared and they match well

A subcarrier multiplexed CDM optical local area network, theory and experiment

A hybrid scheme is proposed for the purpose of suppressing the effects of external modulation and/or laser nonlinearities in subcarrier multiplexing (SCM) fiber optic communications systems. Hybrid CDMA/FDMA combines two schemes in such a way that the resulting hybrid network is robust against interference and is much more spectrally efficient than a CDMA system. Several possible architectures are introduced for the hybrid CDMA/FDMA subcarrier fiber optic local area network (LAN). The networks utilize CDMA and SCM, an asynchronous multiple access scheme. Direct sequence spread spectrum multiple access (DS/SSMA), the most common form of CDMA is employed. It is shown that by using the code sequence sets for which the shift-and-add property holds, intermodulation products (IMPs) and harmonics have a similar interference-like effect as nonmatching sequences do. Owing to the fact that the shift-and-add property holds for conventional spreading sequences, suppression of nonlinear distortions is examined. An average error probability performance evaluation of the selected configuration is presented for a transceiver pair. In analysis of the system, the authors assume the interference term arising from other users is Gaussian distributed. The results are compared to that obtained by exact evaluation of interference distribution using Gauss quadrature rule integration method. The authors compare the performance of this scheme for two different code sequence lengths. They also present some preliminary experimental results on the proposed LAN implementation as well as its measured transmission performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Self-homodyne code division multiple access technique for fiber optic local area networks

A new coherent technique for optical coding and decoding based on spread spectrum principles is described. PSK modulation format is employed along with delayed self-homodyne detection. This technique is described theoretically and demonstrated experimentally. An optical fiber code division multiple access system employing the above spread spectrum technique is proposed. >

Delay time computation for an active star topology local area network

Fiber optic local area networks are nowadays widely available for data transport. Different topologies have been proposed, such as a bus, a ring or a star. A star topology, called Hubnet, has been developed at the University of Toronto. It uses a medium access protocol in which collisions are avoided, i.e. the throughput is an increasing function of the offered load. A model is developed in which the delay is investigated as a function of the throughput. The model is compared with a regenerative stochastic analysis and is validated by means of a simulation model and real-life measurements.