Stephen M. Emo

Bismuth rare‐earth iron garnet composition for a magneto‐optical wheel rotation rate sensor

A magneto‐opticalgarnet composition has been developed for use in a multimode, two‐port, fiberoptic wheel rotation rate sensor for aerospace applications. The sensor utilizes a layer of (Bi, Y, Gd, Tm, Lu, Ca)3(Fe, Si)5O12grown on a (111)‐oriented substrate of Gd3Ga5O12 by standard liquid‐phase‐epitaxy techniques. The sensor has an integral biasing magnet and lensless coupling of multimode glass fibers to a polarizer/garnet/analyzer sandwich. The sensor operates at a signal channel of 725 nm and a reference channel of 850 nm, convenient wavelengths for semiconductor emitters and detectors. The (Bi, Y, Gd, Tm, Lu, Ca)3 (Fe, Si)5O1 2 layer is grown to 25‐μm thickness on one side of the substrate. It has a saturation field of 500 Oe, Curie temperature of 530 K, and the following approximate room‐temperature optical properties at 725 nm: a Faraday rotation of 15°, an optical attenuation of 5 dB, a specific rotation of 0.65°/μm, a specific attenuation of 0.25 dB/μm, and a figure of merit of 2.5°/dB. The low figure of merit is a consequence of the strong optical absorption of iron cations in the near infrared, but it is sufficient for this device. Gadolinium and thulium incorporation onto dodecahedral lattice sites serves the dual purpose of reducing the saturation magnetization and reducing the temperature dependence of magnetization. Device operation is specified over a temperature range of −65 to 450°F (−54 to 232°C), but layers of slightly higher Curie temperature allow operation to an upper temperature limit of 550°F (288°C).

Fast, low insertion-loss optical switch using lithographically defined electromagnetic microactuators and polymeric passive alignment structures

A micro-optoelectromechanical switch that combines microactuator technology developed via the Lithographie Galvanformung Abformung process with lithographically defined polymeric alignment elements is described. The multimode optical switch achieves submillisecond switching times, low insertion loss (<1 dB), low cross talk (<70 dB), low voltage (3 V), and wavelength independence.

Polymer optical interconnection technology: toward WDM applications

We have developed organic polymeric materials that can be readily made into both multimode and single-mode optical waveguide structures of controlled numerical aperture and geometry, making them excellent candidates for WDM applications. Waveguides are formed lithographically, with the liquid monomer mixture polymerizing upon illumination in the UV via either mask exposure or laser writing. Our waveguides are low loss (0.03 dB/cm at 840 nm multimode) as well as temperature resistant (up to 10 years at 120 degree(s)C), enabling use in a variety of applications. Single-mode structures such as directional couplers have been made via laser writing. We further discuss the fundamental optical properties of these polymers and as they relate to WDM applications. As an example, we discuss an inorganic multimode WDM sensor that has been developed for aerospace applications and its integration with multimode polymer waveguides.

Common electro-optic interface module for decoding dissimilar input parameters

A common electro-optic interface (EO) has been designed and tested with a new optic sensor decoding architecture. The new EO module converts Wavelength Division Multiplexed (WDM) position, temperature and pressure signals using the same circuitry. This module uses the combination of Digital Signal Processing (DSP) technology along with a new temperature and pressure sensing technology. This approach results in common circuitry for processing three dissimilar inputs. The new architecture was made possible by advancements in two major areas, DSP and growth of advanced materials with tailored optic properties. This paper will discuss both the top level architecture of sensors and EO module and the performance advantages.

Integrated optic components for advanced turbine engine control systems

The status of present optic technology in turbine engine control is highlighted, and future developments and trends are explored. Attention is given to a base engine control system configured with a primary and backup or standby control. Specific needs for integrated optic components in advanced turbine engine control systems are addressed. The optic harness and interconnect, as well as the electrooptic interface involving only coupling optic excitation and return signals are discussed. A number of 1:2 and 1:5 power splitters and combiners being fabricated using the ion-exchange technology on glass substrates are shown. The devices are potentially useful for the combination of various optical signals from a number of sensor units, and in addition calibration signals could be added prior to signal processing. Integrated optic and electrooptic interfaces are expected to evolve into the engine control environment. A concept for a multilayer electrooptic module which contains a single or multiple optic layers within the printed wiring card is illustrated.