Novel bulk optic multichannel resonator device for close packed wavelength multiplexing.

A simple bulk optic structure is described that is suitable for multiplexing or demultiplexing many closely spaced wavelengths of light. Aside from input/output coupling hardware, the structure is comprised of a single glass, high finesse, Fabry-Perot etalon with a low efficiency diffraction grating etched into one face. The device concept provides a capability for multiplexing ratios in excess of 10, channel frequency separations smaller than 1 GHz, and can be designed to support optical networks having a total communication capacity in excess of 100 GHz. A laboratory model of the multiplexer was constructed and evaluated to demonstrate concept feasibility. The demonstration model, adjusted to demultiplex nine channels separated by 2.2 GHz for a total capacity of 20 GHz, exhibited a throughput optical coupling of -7 dB and a signal-to-crosstalk ratio greater than 15 dB.

Echelon grating multiplexers for hierarchically multiplexed fiber-optic communication networks.

Echelon gratings have many beneficial properties when used as the dispersing mechanism of a fiber-optic wavelength multiplexer including high optical dispersion, high optical efficiency, greatly reduced sensitivity to polarization, simultaneous utility on many wavelength bands, and a capability for hierarchical multiplexing. The use of echelon multiplexers in a hierarchical environment is discussed, and a prototype echelon multiplexer is constructed and used to demonstrate the unique capabilities of this device for creating wavelength division multiplexing systems.

Calcite 2 x 2 optical bypass switch controlled by liquid-crystal cells.

Three blocks of birefringent calcite and two 6-V twisted nematic liquid-crystal cells have been used to make a 2 x 2 optical bypass switch for series-type fiber-optic networks. Optical cross-talk levels of -32 dB have been obtained in both states. The insertion loss was 3 dB in a nonoptimized switch.

Multimode fiber-optic hydrophone based on the photoelastic effect.

A multimode fiber-optic hydrophone based on the photoelastic effect is described. The device offers the advantages that it is simple, low cost, sensitive, inherently solid state, rugged, and exploits a differential approach for amplitude noise reduction. A minimum detectable pressure of 47 dB re 1 microPa/Hz(1/2) has been demonstrated at 500 Hz, and calculations based on photoelastic material properties indicate that a minimum detectable pressure as low as 15 dB re 1 microPa/Hz(1/2) might be achieved. This device design, therefore, represents an attractive technique for making a practical multimode fiber-optic hydrophone.

Total switching of unpolarized fiber light with a four-port electro-optic liquid-crystal device.

A liquid-crystal switch capable of switching nearly 100% of unpolarized light from one multimode fiber to another had been conceived and demonstrated experimentally. The switch uses a double interaction with a single layer of nematic liquid crystal in which the liquid alignment is initially in plane at 90 degrees to the light propagation. This four-fiber optical reversing switch has a simple structure, a low insertion loss, and a low operating voltage. It should find a wide range of applications in fiber-optic communication systems.

Frustrated-total-internal-reflection multimode fiber-optic hydrophone.

A multimode fiber-optic hydrophone based upon the principle of frustrated total internal reflection has been constructed and tested. The sensitivity of the device to acoustic waves in water is in good agreement with predictions derived from its measured sensitivity to applied static displacements in air. The minimum detectable pressure for the device was 62 dB relative to 1 micro Pa at 500 Hz. Static displacements as small as 4.8 x 10(-3) A can be detected. The sensor is compatible with present multimode fiber-optic sources, detectors, and components.

Passive multiplexing system for fiber-optic sensors.

A multiplexing technique is described that requires no electrical power at the sensor locations and allows the signals from many sensors to be carried on a single optical fiber. The multiplexing technique is compatible with the use of multimode fiber-optic technology and intensity modulation transduction mechanisms. The system described represents a first step toward an ultimate goal of a complete passive fiber-optic sensor system. The results obtained with this system allow predictions to be made of ultimate system performance.

Multimode optical multiplexing with low-voltage drivers.

A series-resonant electrical-drive circuit has been used in conjunction with a fiber-coupled multimode electro-optic switch to achieve 2:1 optical time-division multiplexing from a 5-V sine-wave source at a 1.1-MHz rate. The LiTaO(3) mux-demux device is a unique fiber-optic switch that uses a curved prism electrode to deflect a trapped fiber-light cone while preserving the focusing obtained from an internal mirror.

Electrooptic multiplexer system for multimode fiber communications.

The concept of internal reflectance at grazing incidence has been used to construct functional 4:1 electrooptic multiplexers for multimode single-fiber optical data communication. Individual multiplexer units having insertion losses as low as 10 dB and optical signal-to-crosstalk ratios as high as 15 dB have been fabricated. A complete time division multiplexed optical data link has been assembled using two 4:1 multiplexers. The operation of this link demonstrates the feasibility of optically multiplexing multimode signals and represents a benchmark in the progress to control and route multimode light energy.

Star repeaters for fiber optic links.

A star repeater combines the functions of a passive star coupler and a signal regenerating amplifier. By more effectively utilizing the light power radiated by a light emitting diode, the star repeater can, when used with small diameter channels, couple as much power to all receivers of a multiterminal link as would be coupled to the single receiver of a simple point-to-point link.

Holographic ultrafiche.

Even though photographic emulsions exist that are capable of attaining the theoretical resolution for a given wavelength of light, the lack of reliability in recording conventional images at very high reduction ratios has tended to limit greatly the useful storage density of photographic film. Holographic recording techniques offer a means for attaining the necessary reliability, thereby making the recording of many pages at high reduction ratios feasible. Some tasks that are difficult in conventional recording are in fact quite easy in holographic recording. Generally, the characteristics of holographic recording are very different from recording conventional microimages. We discuss the techniques and problems of holographic ultrafiche recording and indicate our progress in this area.

A technique for producing wide-angle holographic displays.

A new technique has been devised for recording and reconstructing holograms which can be viewed from a wide range of angles simultaneously by a large number of people. The problems which arise through the use of this technique have been analyzed and the limitations delineated. Satisfactory wide angle, three-dimensional displays have been constructed in the manner described by using absorption holograms. The features of these holographic displays agree qualitatively with the predicted theoretical limitations.

Measurements of the stability of bleached photographic phase holograms.

Although efficient high quality, bleached holograms have been made using photographic film, the tendency of the bleach products to darken upon exposure to light seriously limits their usefulness in many practical situations. Nevertheless, the great sensitivity of photographic emulsions makes their use in holography highly desirable. To shed light on the problem of stability, relative measurements of light induced darkening were made on heavily exposed plates bleached to yield one of the reaction products: silver chloride, silver bromide, silver iodide, and silver ferricyanide. We have found that the resistance of the emulsion to darkening increases significantly as the molecular weight of the halide ion is increased. Efficient, high quality, silver iodide holographic gratings usable over the wavelength range from 450 nm to 1200 nm, have been made which exhibit complete immunity to darkening when exposed to white light. Representative measurements of holograms made on Agfa 8E70 plates using the more stable emulsions are presented.

Light beam deflection using holographic scanning techniques.

Holographic techniques provide a mechanically simple method for deflecting light beams through two-and three-dimensional scan patterns. One technique for producing a two-dimensional raster scan through the use of a one-dimensional circular motion is described in detail. To illustrate the feasibility of such devices, a two-dimensional holographic scanner has been fabricated and used to construct a simple closed-circuit television system.

Optical design of wollaston-prism digital light deflectors.

The optical design of Wollaston-prism digital light-deflection systems is analyzed. It is found that the performance of the system is limited by (1) the diffraction spreading of the incident light beam, (2) the walk-off of the beam at the exit aperture, (3) the generation of spurious light, and (4) distortions in the angular deviation of each prism. The magnitude and functional dependence of these limitations are calculated, and criteria are supplied for the design of practical Wollaston-prism light-deflection systems. The design procedure is outlined, and numerical examples are given. The examples show that high-speed Wollaston-prism systems having a capacity of more than 10(6) bits are practical at the present time.