When an oblate spheroidal shell is subject to hydrostatic pressure the lengths of its equatorial and meridional circumferences experience changes of opposite sign. If optical fibers comprising the two legs of an interferometer are wound around these circumferences a push-pull hydrophone is created which requires no internal access. This paper will report the sensitivities of a proof of principle ellipsoidal shell hydrophone as determined by conventional bonded resistive strain gages and by optical-fiber interferometry. The shell fabricated at the Naval Postgraduate School was cast from Stycast 1266 epoxy.

This paper describes the design and development of a fiber-optic backbone being examined for data transport in a submarine combat system. Generalized network requirements were determined from functional necessities and the geometry and environment. Both commercial and research fiber-optic networks were then assessed to determine the state of the art and selection of candidate structures. The performance of these structures was analyzed and compared and a candidate architecture was designed and developed.

The inherent immunity of fiber optic materials to electromagnetic environmental effects provides numerous opportunities for wide-spread use of fiber optics aboard ship. Federal budget constraints may reduce the development of new fiber optic systems to address military applications. However there are sufficient similarities between industrial and military sensor needs to warrant use of off-the-shelf fiber optic sensor systems.

A high degree of fault tolerance is required in both commercial and military fiber optic networks. Building fault tolerant physical layers for itultiport fiber optic systems is difficult because of the limited optical loss budget available and the limitations of electro-optic components including sources couplers and switches. This paper describes a fault tolerant fiber optic physical layer based on U. S. Patent 4 The concept permits the circumvention of faults in electronics power supplies or in optical fibers without the need for bypass switches. The fault tolerance is achieved through the use of a 1XN coupler with multiple photodiodes and fibers.

Deviations from ideal alignment and end finish can result in lossy fiber optic connections. Models of amodal fiber-to-fiber interconnects (where the optical energy has no modal structure) commonly used by connection system designers assume independence of the misalignment parameters. This paper describes a method of studying the interaction of these parameters using both computer modeling and laboratory data. The initial results show a coupled relationship existing between several pairs of misalignment parameters. In these instances the net loss due to combinational misalignments was significantly different than the linear addition of the individual loss values.

NASA Lewis together with John Carroll University has worked for the last several years to develop wavelength-multiplexed digital position transducers for use in aircraft control systems. A prototype rotary encoder is being built for a demonstration program involving the control of a commercial transport''s turbofan engine. This encoder has eight bits of resolution a 90 degree range and is powered by a single LED. A compact electro-optics module is being developed to withstand the extremely hostile gas turbine environment.

A 5V/5mW power by light (PbL) power supply has been designed and developed. The design is based on a 50mw 800nm laser diode a segmented GaAs photocell and a DC/DC converter which acts as a voltage regulator. This paper discusses the system concept and elements as well as the measured efficiencies of the components and the system configuration. The paper also discusses the scalability of the design concep

There are government and industry trends towards avionics modularity and integrated avionics. Key requirements implicit in these trends are suitable data communication concepts compatible with the integration concept. In this paper we explore the use ofCode Division Multiple Access (CDMA) techniques as an alternative to collision detection and collision avoidance multiple access techniques.

Fly-by-wire/Flybylight (FBW/FBL) controls are in the process of supplanting traditional mechanical control technology for commercial transport aircraft. Douglas Aircraft Company in cooperation with its suppliers is actively pursuing a comprehensive program to develop and validate advanced flight control concepts and technologies. This paper details the various perceived technical barriers associated with fly bylight as well as the work in progress to overcome them. The advantages of flybylight technology are discussed with particular attention to its potential to help prevent and/or tolerate electromagnetic effects.

The present examination of the use of fiber-optic (FO) networks in launch vehicles proceeded from the definition of a data bus architecture able to supplant the mesh network that typically connects major second-stage avionics packages, as well as replacing the takeoff-minus-zero umbilical link between vehicle and launch complex. The analysis undertaken for such a system in the case of a Delta launcher gave attention to bus traffic, costs, and risk factors; on the basis of analysis results, a hybrid FO/electrical network was selected and its candidate termini were tested for ruggedness and reliability.

Many applications for fiber optic components and systems exist in mobile platforms. Some of the mobile platforms will be expected to operate through or survive exposure to ionizing radiation. Construction of systems that can survive the required radiation environments requires special design considerations. This paper describes the effects of ionizing radiation on some fiber optic components and systems for use in mobile platforms, and an example of transient radiation test data on a prototype analog two wavelength referenced system is presented.

Fiber optics have recently been seen to offer several major benefits in liquid-fuel rocket engine applications. Fiber-optic sensors can provide measurements that cannot be made with conventional techniques. Fiber optics also can reduce harness weight, provide lightning immunity, and increase frequency response. This paper discusses the results of feasibility testing optical fibers in simulated liquid-fuel rocket engine environments. The environments included cryogenic and high temperatures, and high vibration levels.

The three major sub-systems of an aerospace platform are Structure (airframe), Propulsion and Avionics. Traditionally, avionics, the electronics for control and communication, was assigned a relatively less important role. In the modern aerospace vehicles, however, avionics and its integration into the overall system, has become as important if not more, particularly for some defense systems, e. g. ATF (Advanced Tactical Fighter)1 ,2 For space platforms e. g. the Shuttle and the Space Station, the on-board avionics will play a crucial role. Avionics itelf is undergoing a conversion from the analog to digital systems and the associated networks3 are also expected to be entirely digital. One of the penalties one pays in the conversion to digital systems is that the bandwidth needed in digital networks can be an order of magnitude higher than the analog bandwidth. Digital systems also tend to be not as robust as analog systems. A single spike in an analog system may go unnoticed, however, in the absence of any error correcting mechanism, the corruption of a single bit in a digital stream could have disastrous consequences. Adoption of error correcting codes again increases the bandwidth. In view of the high bandwidth, immunity to Electromagnetic Interference and other factors, serious consideration is being given to digital optical communication, based on Fiber Optic Local Area Networks (FOLAN), on-board aerospace vehicles4. In principle a FO-LAN can be implementing by just replacing the copper coax wire by an optical fiber and one can immediately expect the benefits of increased bandwidth, noise immunity etc. There are, however, several problems that attend this transition including; -- very few, if any, fiber optic systems are space qualified. Even the standards for flight and space worthiness are not well established. -- the effect of space environment, e. g. vacuum, UV (and other radiation), atomic oxygen, temperature excursions, acceleration cycles etc., on fiber optic components is not well understood. -- some mundane looking problems, such as connectors and passive T's, turned out to be formidable obstacles, particularly for space applications where in situ repair and maintainence can become critical issues. -- the intrinsic bandwidth of the fiber is indeed quite high (in Gigabits/sec), however, the pointto-point transfer of mission oriented information from one node to another, i. e. the information capacity, depends on many other factors that can adversely effect the overall performance of the network. Here we shall address only the last problem, namely, the transfer of information on FOLAN aboard space systems. In particular we will discuss the factors that effect FOLAN performance in the context of Bandwidth, Throughput and Information Capacity.

The alignment techniques, bearing designs, and optical system configuration used by a low optical feedback/low insertion loss single-mode optical rotary joint are presented. Attention is given to the test results obtained for temperature, shock and vibration, and humidity cycles. Initial design criteria have been substantially exceeded by the system components fabricated to date; only the humidity-related performance goals have yet to be reached, due to the intrinsic permeability of the rotating interface by water vapor in initially hot, humid atmospheric conditions that support condensation upon subsequent cooling.

E-Systems/ECI Division has developed a fiber optic based broadband communications bus for application to ground airborne and shipboard Command Control Communication Intelligence (C31) platforms. The system is based on a linear low noise fiber optic backbone bus with up to 3 GHz bandwidth and interface modules which allow voice (PABX) data and video to be handled and switched in one common media. This concept greatly reduces the complexity of system integration and deployment while decreasing the system weight.

A new heat resistant plastic optical fiber with Teflon AF cladding has been develope,which is suitable for use up to 135 degrees C, 10 degrees higher than that currently available. Also introduced will be a plastic image transfer fiber which consists of more than 200 tinly fibers.Discussion will include properties and applications for this new image fiber.

A fiber-optic temperature sensor has been developed for aerospace applications on the basis of the time rate of decay (TRD) principle, with a view to an operational temperature range of -60 to 350 C. This TRD system has completed qualification testing and will then undergo flight tests. Attention is presently given to the design and performance of four low temperature sensors that are subelements of the larger sensor system; in order to convert analog signals into over/under temperature indications, simple comparators are implemented in software.