The evolving Fibre Distributed Data Interface standard (FDDI) makes effective use of fibre-optic technology in order to provide high performance data links between digital equipment. Future enhancements to the FDDI standard are planned to support simultaneous voice and data transfer, thus providing a powerful communications system over the local area. The implementation and adoption of FDDI relies on the availability of reliable fibre-optic components. This paper describes the components available and discusses their conformance to the FDDI standards. Future developments and applications of FDDI are discussed.

The issues covered by this presentation are related to analog and digital fibre optic link design using Hewlett-Packard's new generation of high speed 820nm components. The emphasis is placed on electronic circuit design. Firstly different LED drivers will be discussed, and then the presentation will focus more on receiver-related items.

The use of wavelength division multiplexing (WDM) to provide multichannel access to a common single optical fibre transmission medium within a local area network (LAN) is discussed. A star-based WDM optical fibre LAN topology is described prior to consideration of possible access strategies which may be employed within such a multichannel network. A multichannel carrier sense multiple access with collision detection (CSMA/CD) access protocol originally conceived for application with broadband coaxial LANs is outlined. Consideration is then given to two novel multichannel token passing access strategies(called the reservation channel and piggyback protocols respectively) which have been specifically designed for application within WDM optical fibre LANs. Computer simulated performance characteristics for the aforementioned multichannel protocols are presented and compared, both with each other and with their respective single-channel approaches employing the same overall network transmission rate. The performance comparison demonstrates not only the distinct benefit of multichannel access in terms of network traffic throughput but also the superiority in terms of network traffic throughput of both the multichannel token passing access strategies over multichannel CSMA/CD when the individual channel bit rates exceed 10 Mbit/s for a WDM optical fibre star LAN with a 2 km diameter.

Recent progress and concentration of efforts in fiber optic technology for the subscriber networks will make it attractive for the deployment of fiber optic cable for residential and small business customers to support future broadband-ISDN requirements. This paper describes a systematic approach for the deployment of the required fiber cable and associated hardware in the distribution and drop portions of a subscriber network. Furthermore, discussions on an optimum architecture will be included for flexibility, reliability, maintainability and underlying economic factors which will allow for a graceful evolution to a subscriber fiber optic network.

This paper reports on the application of an optical tapping technique (Ref.1) to the distribution of broadband analogue signals. The taps use controlled bending of a monomode transmission fibre to couple light into a polymer receptor fibre. Signals may be extracted from the transmission fibre at any point along its length without breaking the fibre. Consequently taps may be installed or removed without taking the fibre out of service.

American electric utilities are beginning to make heavy use of fiber for a number of applications beyond transmission of,voice and data among operating centers and plant facilities. These additional uses include load management and protective relaying. This shift to fiber is due to the advantages offered by fiber and because of congestion in the radio bands used for power line carrier and private microwave systems. This shift to fiber has been facilitated by a regulatory policy permitting utilities to lease reserve capacity on this fiber systems on an unregulated basis. This, in turn, has interested electric utilities in building fiber to their residential and commercial customers for voice data and video. This will also provide for sophisticated load management systems and generation of revenue.

The application of single mode fibre to the local network environment opens up major opportunities for service provision via shared access networks. Previous technologies (copper pair, coaxial cable and multimode fibre) had bandwidth limitation problems that placed a severe restriction on both the level of resource sharing and the service package that could be delivered. The enormous bandwidth capability of single mode fibre can be used to provide significant resource sharing without incurring fundamental restrictions on the capacity of the services carried. The paper briefly outlines some of the activities within British Telecom on shared access systems. Early systems concepts were either based on fibre feeders to remote multiplexers for the delivery of telephony and data services to large customers or the use of advanced wavelength multiplexing techniques over passive optical networks for the transmission of wideband services to business and residential customers. Recently activity has concentrated on a passive optical network that shows good potential for the economic provision of telephony services. The structure of the network allows the later addition of broadband services via additional wavelengths without disturbing existing telephony/data customers. The basic network has a fibre feeder from the exchange to passive optical splitters housed at the Cabinet and Distribution Points (DP). Each customer receives a fibre from DP and via this a TDM multiplex broadcast from the exchange which carries the customer's traffic. The customer equipment accesses the time slots destined for the customer and delivers the data via a suitable interface to provide the services required. Customers transmit back to the exchange in a time multiplex synchronised by a ranging protocol that sets an appropriate delay in the customer equipment to avoid collisions at the optical combiners in the DPs and Cabinet. Present studies are considering a total optical split of 128 ways with a transmission rate of 20 Mbit/s. This allows an attractive set of service options for both business and residential customers. Sufficient capacity is available to feed up to 120 customers (allowing 8 spare optical test points within the network) with 144 kbit/s ISDN connection. Business customers requiring more capacity would access multiple time slots as required up to the limitations of system capacity.

The attenuation of matched cladding and depressed cladding fibres cabled in a loose tube cable structure was measured in the temperature range of - 40 deg C to + 60 deg C. Also measured was the microbending sensitivity of the fibres, which was found to be a function of mode field diameter and cut-off wavelength. From these measurements a direct correlation between the increase in attenuation present at low temperatures (- 20 deg C and below) and the microbendig sensitivity could be deduced.

The optical feedback (OFB) receiver can offer considerably better sensitivity than resistive feedback designs. Such receivers could find important application in multibranched or spectrally sliced local access networks where high optical losses may be encountered: However, an additional feature of these networks is that the system elements (transmitter, receiver etc) must be cost effective in high volume production. This paper will demonstrate an OFB receiver with the highest reported sensitivity of -64.0 dBm at 2.048Mb/s without the need for high quality optoelectronic and electronic components.

With the anticipated increase in demand for broadband services, and due to significant reductions in the cost of single mode fiber technology, it is likely that the local loop will make greater use of fiber optic technology. This will result in a tremendous increase in the required capabilities of a telephone network to handle the massive amounts of subscriber traffic.

The world's first transoceanic optical fibre submarine cable systems are under construction at the moment both in the Atlantic Ocean and in the Pacific Ocean. The OS-280M system developed by KDD has been introduced as a part of these systems. This paper describes the OS-280M system, the first generation optical fibre submarine cable system developed by KDD for the long-haul, transoceanic and international telecommunication service. The future technologies for optical fibre submarine cable systems are also discussed.

Fibre optic technology is now being exploited in many diverse applications including long haul and local network communications, using both direct detection and coherent techniques, sensor systems, microwave optical links and for signal processing. These applications demand active optoelectronic terminal devices such as sources, detectors and integrated components with performance parameters suitable for the application as well as costs (or cost projections) low enough to catalyse the development of the systems. Single frequency distributed feedback (DFB) lasers are now becoming widely available and are suitable for high speed (>2Gb/s) direct detection and for FSK cohefent systems. DFB lasers in combination with external or integrated passive cavities offer reduced linewidth and rapid electronic tuning, opening the way to multichannel subscriber networks. Optoelectronic components capable of microwave bandwidths (10-30 GHz) are also being reported; such components will find applications in microwave bandwidth point to point links, radar remoting and optical signal processing. Critical components here include the laser source, which may be directly modulated or followed by a high speed guided wave modulator and the detector/receiver. In this presentation developments in such active components for single mode fibre systems were reviewed.

Mesa PIN structures have been fabricated in the material system In(As,Sb,P) from layers grown by liquid-phase epitaxy lattice-matched to InAs substrates. The electrical performance of the structures shows their suitability as photodetectors at 2.56õm in optical communications.

A promising technique for the design of high speed integrated optical modulators has recently been reported. By employing a coded sequence of phase reversals within the electrode structure, greatly extended bandwidth may be achieved without increase in drive voltage. This paper discusses the theoretical performance of a modulator of the new type and presents preliminary experimental measurements in the 2-18 GHz frequency range. Coded sequence modulators are expected to have considerable significance in specialised microwave optical applications.

This paper describes the performance of a travelling wave electroded, Ti-indiffused LiNbO3 phase modulator, pigtailed with polarisation maintaining fibres. A rugged high frequency package enables the device to withstand shock, vibrations, acceleration and temperature cycling without compromising the performance. A Vπ of 8 volts at dc and 3dB modulation bandwidth of 4GHz is reported. The measured optical insertion loss for the fibre-pigtailed device - fibre is 3.5 ± 0.5dB.

A high-yield process for making planar InGaAs/InP photodiodes based on metal-organic vapour phase epitaxy (MOVPE) growth at atmospheric pressure has been developed. The process results in very good uniformity and yield and gives high-performance devices of excellent reliability, with a random failure rate of less than 0.3 FITs at 20°C. This reliability performance is easily able to meet the stringent requirements for detectors in submarine systems.

We have developed effective techniques for the design and fabrication of large and complex integrated optical components in lithium niobate. The application of these techniques to the design of an 8x8 space switch array suitable for switching broadband traffic in an optical fibre network is discussed. We consider system constraints on wavelength, loss and crosstalk. The implications of using different switch architectures both on the chip and when interconnecting multiple chips to form larger switch networks are studied. The design of the component has been optimised within the constraints of the integrated optical technology and the packaging and interconnection of the device, taking the system requirements fully into account. Flexible techniques for mask coding and mask production are described. We have measured fully functional switch arrays with switching voltages of 25V and optical loss of 5.5dB.

New Active Bidirectional couplers are manufactured in large quantities and with low costs, in order to equip the French Optical fiber integrated services local telecommunications networks.

Focussed ion beam micromachining is a new maskless process that may be used to fabricate deep (>10 µm) features in LiNb03. This is advantageous, because LiNb03 is difficult to etch selectively otherwise. Features in the form of trenches, cut accurately orthogonal to titanium-diffused channel waveguides, may be used as rugged on-chip mirrors for channel waveguide integrated optics. These may be combined with other waveguide components to form direct reflectors, reflective bends, and electro-optically switchable track-changing reflectors. Experimental data on all three devices are given.

Assemblies of single-mode fibre components have been manufactured on single lengths of fibre, thus avoiding problems associated with splices such as connection losses and unwanted back reflections. Components based on the fused and polished fibre technologies have been networked into specialised assemblies for sensor (particularly interferometric) signal processing and telecommunications systems. Examples are given of practical assemblies and limits on our ability to manufacture are discussed.

The concentricity of a primary and secondary fiber coating can be measured using a laser light forward scattering method. This paper presents a ray-tracing method for calculation of fiber secondary coating eccentricity from the measured intensity patterns. Assuming, that the variation of coating diameters is ±3.0%, variation of the refractive indices is ±0.01, the measuring accuracy of intensity maxima is ±0.3 degrees and eccentricity of primary coating is less than 3.3μpm, then the eccentricity of secondary coating can be measured with an accuracy of ±0.7 μm, when the diameter of the fiber secondary coating is 250μm, the diameter of the primary coating is 205 μm and the diameter of the fiber cladding is 125 μm. The model, derived here, was tested by measuring forward scattered intensity patterns obtained using either HeNe-laser (λ=633 nm) or semiconductor laser diode (λ=780 nm) light. The measurements confirmed that the new model can be used to give the concentricity error of secondary fiber coating with the estimated accuracy.

Using ion exchange in glass, Corning has developped the PhotocorTM range of passive multimode devices. This paper deals with the extension of the range to include wavelength division multiplexers (WDM) and star couplers. The wavelength division multiplexers operate at the standard wavelengths of 850 and 1300nm. Maximum specified insertion loss is 1,5dB with 1,2dB being a more typical figure. Recent devices measure under 1dB. Rejection of the undesired wavelength exceeds 35dB at 850nm. Star couplers have been developed with the same integrated optics on glass approach. For a 8X8 coupler, insertion loss, port to port, is in the range 9.0-11.5dB. Packaging for both devices is fully developed. Environmental and mechanical test results are reported.

The nature of surface plasmons supported by thin metal films is discussed. A dispersion equation is presented and used to define theoretically the design criteria for in line fibre optic polarizers based on the polarization selective evanescent coupling between an optical fibre and the plasmon modes of a thin aluminium film. The experimentally observed design conditions were consistent with the theory and a high quality polarizer and polarizing coupler demonstrating extinction ratios in excess of 50dB and 30dB (per arm) respectively were realised.

A review of optical fiber sensors for local and remote measurements of chemical parameters is presented. Both photometric and optodre sensors are discussed along with their applications in the medical field, in industrial processes control, in safety alarm systems and in environmental pollution monitoring. Typical working principles based on fluorescence intensity modulation and dual wavelength differential absorption are described.

Optically powered resonant structures are important in passive sensor systems which rely upon the use of fibre optics for excitation and interrogation. In this study, photothermal excitaion of the device was simulated and comparison of the output characteristics obtained was made with the work of the experimental investigations.

A remote passive pressure sensor has been demonstrated using a high birefringence optical fibre. The principle is based upon a single fibre polarimetric interferometer and the technique for aligning the birefringence axes of the fibre. The design incorporates a temperature compensation and allows the use of low coherence sources.

We present an analysis of the dependence of the fringe visibility on input polarization in two-beam interferometric sensors, and discuss three techniques which can be used to overcome polarization induced fading in such sensor systems. The principle of operation and experimental performance of each scheme is discussed.

High accuracy interferometric systems sensing slowly varying measurands place great demands on the frequency stability of the optical source used. In this paper, we determine the stability requirements of interferometric systems employing various signal processing techniques, and describe investigations into methods for locking the laser diode to a unique frequency by means of a monochromator, a diffraction grating, an interference filter and an atomic transition in a hollow cathode lamp.

In many liquid crystal systems there is a direct phase transition between an optically scattering smectic or chiral nematic mesophase and the clear isotropic phase. Such transitions are characteristically sharp and take place at well defined temperatures which may occur anywhere in the range -20°C to 200°C. It is this novel feature of liquid crystal systems which together with the attributes of low loss optical fibres forms the basis of an accurate optical temperature switch'. The properties of this device include remote passive sensing with a narrow switching differential which is safe in hazardous environments, and is free from EM and RF interference. In this paper we discuss the operation of the liquid crystal temperature switch in a number of device configurations (reflective or transmissive) together with the wide variety of applications.

A fibre-optic gas detection system for methane has been developed and evaluated. The system is intrinsically safe, fast, reliable and low in maintenance requirements.

This paper describes improvements to a novel fibre optic methane sensor which has several advantages over previously published fibre optic techniques. As with the earlier method, it is based on a scanning Fabry Perot etalon filter and is self-referencing, requiring only a single optical sensing path and photodetector. A laboratory version of the sensor, employing a white light source, has been constructed and tested, and was found to be capable of detecting 0.01% by volume methane in air, with a response time of approximately 1 second.

The sensing of rotation using counterpropagating optical beams in a fiber loop (the SAGNAC effect) has gone through extensive developments and demonstrations since first proved feasible by Vali and Shorthilll in 1976. The interferometric fiber gyroscope minimum configuration2 which uses a common input-output port and single-mode filter was developed to provide the extreme high stability necessary to reach the sensitivities at low rotation rates attainable with current state-of-the-art detectors. The simplicity and performance of this configuration has led to its acceptance and wide-spread use. In order to increase the mechanical stability of this system, all single-mode fiber components are employed and a further advancement to integrated optics has enabled most of the optical functions to be placed on a single mass-producible substrate. Recent improvements in the components (eg polarization maintaining fiber and low coherence sources) have further enhanced the performance of the minimum configuration gyro. This presentation focused on the impact of LiNbO3 integrated optic components on gyroscope developments. The use of Ti-indiffused LiNbO3 waveguide optical circuits in interferometric fiber optic gyroscopes has taken two directions: to utilize only the phase modulator, or to combine many of the minimum configuration optical functions on the electro-optic substrate. The high-bandwidth phase modulator is the driving force for using LiNbO3 waveguide devices. This device allows both biasing the gyro for maximum sensitivity and closing the loop via frequency shifting, for example, thus increasing the dynamic range of the gyro and the linearity of the scale factor. Efforts to implement most of the minimum configuration optical functions onto a single LiNbO3 substrate have been led by Thomson CSF.3 They have demonstrated an interferometric gyroscope with excellent performance using a LiNbO3 optical circuit containing a Y-splitter, phase modulator, and surface-resonant polarizer. JPL and AT&T-BL have an effort, under a NASA contract, to investigate other integrated optic gyro front-end circuits with the eventual goal of combining all minimum configuration functions on a single substrate. The performance of a gyroscope with a LiNbO3 polarizer, 3dB splitter, and phase modulator was discussed along with the waveguide device characteristics. The key advantages, future trends, and present issues involved with using LiNbO3 waveguide devices in a gyroscope were addressed.

The development of a fibre-optic based damage assessment system for composite material structures requires a base of knowledge that to date is not available in the literature. We report on several advances that will contribute towards the development of "structurally imbedded fibre optic damage evaluation" (SIFODE) technology. These include: devising a special surface treatment that allows control of the damage sensitivity of the optical fibres, determining their optimum orientation with respect to the material fibres in the adjacent plies and their depth in regard to an impact surface. The influence of the imbedded optical fibres on the strength and impact resistance of the composite material has also been investigated.

A BiCore fibre (BCF) has been drawn and tested experimentally as a model for studying evanescent mode coupling to be used for single-mode passive fibre components made in the Fused-Head-End technique and in planar optics. The coupling coefficient K is shown to be linearly related to wavelength A. Polarization effects are manifested in the constant term only. Given the variation in core shapes good agreement with existing theory is found. A 167 mm long BCF forms a fibre polarization-splitter. For a BCF filter the figure of merit is the bandwidth length product, typically about 1.2 nm.m FWHM. Bending a BCF over a certain length and radius satisfies well straightforward theory so that the device can be fine-tuned in a controlled way. Some practical applications are indicated.

A common problem experienced in the opto-electronic industry is the need to rapidly and accurately fix time-consuming, optical alignments. Novel chemistry has allowed the development of a generation of positioning resins which combine very rapid cure ("command cure") to good depths with very low cure shrinkage. Interestingly, the cure is triggered by visible blue light, safer and faster than ultraviolet. The cured resins have good stability over a range of environments and show particularly good resistance to solvents. Typical properties of the resins are described with performance data relevant to opto-electronic applications. Applications where the system works to particular advantage are described.