We designed and built a computerised single mode fiber interferometer. This paper describes the design of this system and discusses the results. Polarisation problems are optimalised, and a very high temperature sensitivity is obtained.

A new optical fiber interferometer is proposed. It realizes the advantage of having a fiber-optic probe desensitized to environmental perturbations. The passage of the reference and sensing beam through the same path in a Sinale-mode optical fiber constitutes the basis of the new interferometer. Two main applications are suggested: Michelson-type interferometer for vibrating target measurements (FOMI) and fiber-optic link noise-free for fiber-optic sensor applications (FOIL). The experimental results point out the high noise-rejection operated by the new scheme compared with a conventional fiber-optic interferometer.

Progress in optoelectronic broadband switch matrices is reviewed. An experimental integrated 2x2 matrix based on photoconductive optical detectors is described. Isolation greater than 50 dB at frequencies up to 100 MHz is observed in this matrix, which is contained in a single TO-5 package.

Nonlinear optical effects in fibers can affect the intensity and spectral characteristics of an optical signal, thus present power transmission limitations. On the other hand, one can make use of nonlinear optics in fibers for efficient frequency conversion and generation of new frequencies which are important for fiber-optics studies and measurements. In this paper we review the use of single-mode fibers for near-infrared frequency conversion in the 1.1-1.7 μm spectral region by stimulated Raman scattering, tunable Raman oscillation, and stimulated, phase-matched four-photon parametric mixing, and discuss their applications.

Recent developments in fiber optics and laser sources have emphasised the need for high efficiency semiconductor photodetectors responding at unprecedented speeds over an ever-expanding wavelength range. To meet these needs, new types of device structures and new materials are increasingly being explored. The influence of general device and material characteristics on device capability is discussed, and the limitations explained through the use of general, time-dependent detector models. Appropriate device structures and materials are discussed for the development of high quantum efficiency, fast detectors at wavelengths ranging from the ultraviolet through to the infrared region appropriate to future optical communications systems. Recent results using junction and modified Schottky barrier structures are described, and the development of new materials for detector applications in the visible and infrared spectral regions is discussed.

A changing speckle pattern exists at the output of a multimode optical fiber if the optical source is sufficiently coherent. When spatial filtration (for example, at a misaligned connector) or polarization filtration (for example, in certain access couplers) occurs in the presence of such speckle, the optical signal power fluctuates; such fluctuations are called "modal noise." This paper reviews modal noise theory and experiment, including the prediction and measurement of the modal noise signal-to-noise ratio in the presence of spatial filtration and constrained total guided power. It also presents new results relating to modal noise effects in fiber branching devices such as star couplers, access couplers, and power dividers.

Optical guided wave transmission has provided both economic and technical advantages for an array of telecommunication applications. The advances in capability of optical transmission have been the result of dramatic improvements in fiber and other opto-electronic devices. What has not changed significantly is the technique of superimposing information onto the optical carrier. As a result, the information carrying capacity and also the repeater free operation of guided optical wave systems have not reached their full poten-tial. Coherent optical communications is an approach whereby information is carried by either the amplitude, frequency or phase of an optical carrier. Heterodyne detection would increase receiver sensitivity and permit closer optical carrier spacing and thus increase information carrying capacity. This would be achieved by IF filtering with highly selective electrical networks. There are several implementation difficulties that must be overcome to achieve the advantages of optical coherent communications.

A fiber optic cable splicing system is being developed for the U.S. Army Communications-Electronic Command (CECOM). The manually operated splicing machine and cable splice housing are designed to be used to repair communications cable under field conditions. The repair procedure is described, with the aid of photographs of the first working models of the splices and splice housing. Further work is being done to reduce costs and to simplify the operations involved in cable repair.

Splices and demountable connectors are a necessary component in optical-fiber systems as they allow for flexibility in both the installation and maintenance of optical-fiber links. Permanent joints (i.e., splices) tend to have less effect on system performance than remateable connectors; however, they are both capable of profoundly influencing system performance. Joints generally affect both the attenuation and bandwidth of an optical fiber link and thus require careful study.

This paper describes an evaluation of candidate multichannel, hermaphroditic fiber optic connectors under uniform, and where possible, standard conditions. Connectors manufactured by TRW, Bell-Northern, Hughes, ITT-STL (Ptarmigan) and ITT-Cannon were tested. The optical insertion loss was measured while the connectors underwent (1) normal mating, (2) repetitive mating, (3) strain relief flexing, (4) temperature cycling, (5) connector-to-cable tensile stress and, (6) connector-to-connector tensile stress. In addition, the candidate connectors were rated by attributes for (1) mating forces, (2) alignment ease, (3) cleaning, (4) handling damage, and (5) human factors.

The fabrication and performance of GaInAsP/InP LEDs emitting at 1.3 microns is described. These devices are hermetically sealed into microwave pill packages and the use of micro-lens coupling enables power outputs up to -13 dBm to be achieved. Detection of 1.3 micrcn radiation is achieved using the PIN FET approach in which a GaInAs/GaAs photodiode and GaAs FET chip are assembled on a thick film hybrid circuit and hermetically sealed with a fibre pigtail into a metal DIL package. Device performance and construction is detailed. Current best performance of -52.4 dBm and -45 dBm at 41 and 160 Mbauds respectively have been achieved. Life test results are reviewed. These components are currently being used in transmission systems being installed by Plessey Telecommunications Ltd.

A microcomputer controlled system is described for measuring the two dimensional near-field radiation pattern from optical fibers. Because radiation measurements may be made in two dimensions, a novel method has been devised whereby a constant intensity contour of the core is mapped. A modified Left-Most-Looking (LML) digital image encoding algorithm is used to map the contour of the fiber core. The iso-intensity map provides information about the tolerance field, in which all of the measured iso-intensity points lie, and core noncircularity. Such information is useful in determining coupling efficiency at splices, connector joints, and terminal points. This paper will discuss the measurement apparatus, accuracy, precision, stability, and method of analysis of the NBS system. In addition, results will be presented on measurements of core diameters, the length dependence of such measurements, wavelength dependence of the radiation patterns, power law fits to the patterns, calibration apparatus, and iso-intensity contours of telecommunications-grade fibers.

Attenuation Measurements have been made at 0.82 pm and 1.3 pm on 13 types of monofilament fibers wound on conical payout spools at four levels of pressure. An analytical model of microbending attenuation has been derived by modifying a previous model by Gloge. The measured data fit satisfactorily around the trend predicted by the model. Separate trends are explained for graded index and step index fibers. The influences on attenuation of payout link design parameters including numerical aperture, core, cladding and buffer diameters, spool diameter, winding tension and materials choices are also explained.

A computer controlled automated test facility has been developed by Bell-Northern Research for the laboratory evaluation of fiber-optic digital transmission equipment over a range of environmental, electrical and optical stress conditions. The system, named Fiber Optic System Test (FROST), is currently used to verify the design integrity and performance of short wavelength (850 nm) fiber-optic transmission equipment operating at the DS-2 (6.312 Mb/s) and DS-3 (44.736 Mb/s) rates in the digital hierarchy. It can also test equip-ment operating at the DS-1 (1.544 Mb/s) rate. This paper presents the basic system design, describes the implementation and outlines the capabilities of the system. The automated test system has provided data on the equipment being tested which supplemented and expanded information obtained from system trials carried out under field conditions. It permits the rapid verification of improvements in equipment design and enables tests to be carried out on several systems simultaneously, which would be time consuming and expensive if undertaken using manual control. The effectiveness of the test program using the FROST facility has led to the system being enhanced to accommodate long wavelength fiber-optic digital transmission systems. It also has potential applications as a Computer Aided Manufacturing tool.

A large fiber optic system is presently being installed at Vandenberg Air Force Base (VAFB) for the transmission of data, telemetry, control, and video signals between various MX-missile flight testing facilities. The fiber optic system utilizes some 80 kilometers of six-and eight-fiber cable, one third of which includes dual-window fiber. Because of the large quantity of cable installed and strict cable plant testing/validation requirements, a good deal of field measurement data is being acquired. Field measurements include: fiber cable receiving inspection testing using an OTDR, end-to-end link attenuation testing at both short and long wavelengths, and end-to-end link bandwidth testing at short wavelength. Special test equipments were designed to provide the end to end link attenuation and bandwidth measurement capabilities. Measurements taken, along with their respective relationship to draft EIA (fac-tory type) procedures, and test results are discussed in detail.

A review of requirements for testing of fibre optic components is presented, with emphasis on connectors, the connector/cable interface, and fibre and cable parameters affecting the connector/connector interface parameters. The review will be developed from the point of view of an ultimate user of a connectorized cable, and will correlate system requirements with the parameters to be tested and the trends in developing test techniques which properly assign performance responsibility to the cognizant component supplier.

We have successfully fielded a Fiber Optics Radiation EXperiment system (FOREX) designed for measuring material properties at high temperatures and pressures on an underground nuclear test. The system collects light from radiating materials and transmits it through several hundred meters of optical fibers to a recording station consisting of a streak camera with film readout. The use of fiber optics provides a faster time response than can presently be obtained with equalized coaxial cables over comparable distances. Fibers also have significant cost and physical size advantages over coax cables. The streak camera achieves a much higher information density than an equivalent oscilloscope system, and it also serves as the light detector. The result is a wide bandwidth high capacity system that can be fielded at a relatively low cost in manpower, space, and materials. For this experiment, the streak camera had a 120 ns time window with a 1.2 ns time resolution. Dynamic range for the system was about 1000. Beam current statistical limitations were approximately 8% for a 0.3 ns wide data point at one decade above the threshold recording intensity.

The cross impact of key standard access protocols on fiber-optic-configured topologies for local area network (LAN) applications is examined. A taxonomy of topologies and access techniques for fiber optic local area networks is developed. Network performance criteria and the key parameters affecting fiber optic networks are identified. These parameters are used to develop a methodology to enable the selection of an optimum fiber optic topology for a particular access protocol and application. Critical components required for the realization of a fiber-optic-based LAN are discussed.

A fiber-optic local area network, named Fibernet II, has been demonstrated. Fibernet II has been designed for use with the channel access discipline known as carrier-sense multiple-access with collision-detection. The detection of data packet collisions is necessary for Ethernet, a coaxial cable local area network, which uses statistical arbitration to coordinate net access. Plug compatible with Ethernet at the transceiver cable interface, Fibernet II can extend an existing Ethernet installation or can serve as a stand alone Ethernet, replacing coaxial cable with fiber cable. Fibernet II is a five channel prototype active-star configured network operating at a 10M Bit/s data rate. Fibernet is designed for modular growth to enable easy network expansion.

This paper describes the principles and practical implementation of a novel form of optical fibre data telemetry system. The system modulates coherent light propagating in a multimode optical fibre by passing an ultrasonic wave across the fibre. The modulation process is highly efficient, and may be effected by simply attaching a suitable ultrasonic transducer to the outside of a fully cabled and protected fibre. Data connection does not interfere at all with the optical path through the system. A number of similar stations-up to perhaps fifty in total - may be connected to a single fibre link covering a distance up to several kilometres. The system is ideally suited for data collection functions from remote or hazardous areas, since the individual data input stations may be designed to consume minute amounts of power.

A number of schemes for wavelength division multiplexing (WDM) have been reported in the literature in the past few years. However, most of them tend to be laboratory devices used in demonstrating the principle of operation. Recently a simple, low cost, and rugged wave-length multiplexer (X-MUX) based on the interference filter has been devised at Lockheed. These multiplexers have also been used as the central elements for duplexed data links in field applications and have performed exceedingly well. Typically, these X-MUXs have inser-tion loss of 2 dB and a crosstalk between channels of 33 dB at a channel separation of 22 nm. When used in 3-km duplex links, electrical crosstalk between 15 MHz video channels is less than -40 dB, and in 10 MBPS digital links (with contributions from system noise) BERs of less than 10-10 are realized. In this paper, the principle of operation, mechanical con-struction, and test results of the X-MUX will be reported. Detailed test results on full duplex links (up to 3 km link length) will be presented. Use of A-MUX, directional coup-lers, and optical switches for computer interconnects will be discussed. Finally, the use of integrated optic devices for such endeavors will be suggested.

The last decade witnessed the emergence and acceptance of Fly-by-Wire technology for advanced flight control systems. The benefits of fiber-optic technology such as low EMI susceptability, lower aircraft system weight, and lower life cycle cost may substitute Fly-by-Light technology as the accepted state-of-the-art in this decade. This paper addresses the motivation for moving toward Fly-by-Light technology and technology needs for implementation of Fly-by-Light with particular emphasis on the sensors. The paper examines the impact of increased intensity levels of man-made threats (EMI, EMP and nuclear radiation) coupled with the extensive utilization of non-conductive fuselage materials. A baseline Fly-by-Light control system highlights the key system elements of sensors, effectors, and communication which require development for fiber optics to be used. With the ongoing development of fiber-optic communication technology by the telecommunication industry, the responsibility has fallen to the controls industry to provide the generic technology development for the sensing and effector requirements. United Technologies Corporation and in particular its Hamilton Standard and Research Divisions have been developing effector and sensor technology and have applied the results of these efforts to the U.S. Navy Linear Optical Transducer and the U.S. Army Rotary Optical Transducer programs. The linear transducer is a 12-bit, 3.5-inch stroke device. The rotary is a 10-bit, 40 degrees-of-travel unit.

An optical fiber protected distribution system (PDS) has been developed for data transmission links which require cost effective protection from unauthorized access. The nonemanating characteristics of glass optical fibers make them an ideal transmission medium that precludes all but the most sophisticated attempts at compromising the signal integrity. In the PDS, intrusion attempts are limited by the use of detection alarms which activate when the optical fiber cable is penetrated or significantly altered. In an alarm condition, the data is terminated until system integrity is verified and the system is reinitialized. Even if the optical power were to be tapped, signal decoding is made difficult by burying the signal in the natural quantum noise associated with any optical power. The PDS system will transfer RS-232 data from DC to 20 kb/s over link distances up to 2 km with full quantum noise limited protection. The same data rates can be transmitted up to 10 km with alarms but with somewhat reduced protection. The optical fiber PDS offers an alternative for applications that previously required bulky, expensive ferrous metal conduit.

Optical cable communications Systems have progressed to where they can be effectively employed in tactical(highly mobile) communications systems. The goal of a current Marine Corps program is to examine the replacement of CX-4566 (26-pair local distribution cable) with a fiber optic cable system. This replacement would reduce electromagnetic and radio frequency interference and crosstalk. However, the most significant benefit of fiber cable in tactical communications is the better than 10:1 saving in size and weight. This paper describes a demonstration system developed to replace CX-4566 cable assemblies. The fiber optic demonstration system is designed to interface with specific Marine Corps tactical communication shelters. The system mounts externally on the signal entry panel allowing operation with either metalic or fiber optic cable assemblies.