Showing papers on "Single-mode optical fiber published in 1971"

EFFICIENT, SINGLE‐MODE, cw, TUNABLE SPIN‐FLIP RAMAN LASER

Abstract: Continuous operation of a spin‐flip Raman laser in InSb using a CO pump laser has been achieved in a single longitudinal and single transverse mode with over‐all power conversion efficiency in excess of 50% and output power in excess of 1 W. Measured threshold powers were less than 50 mW.

Electronically tunable optical filter using acoustic waves

Abstract: A tunable optical filter suitable for use in integrated optical circuits including the combination of a substrate having an optical waveguide such as a thin film thereon. Means such as an optical fiber or grating is provided for introducing light waves in a first mode into the waveguide. An acoustic transducer driven by a tunable electronic signal source is used to propagate acoustic waves on the surface of the waveguide. The optical and acoustic waves interact to produce another optical wave having a mode different than the original optical wave when phase matching conditions are satisfied. A mode filter is located in the waveguide to block the original optical wave and pass the second optical wave.

A Comment on the Aries Observations

Abstract: Dr Swallow’s observations of the vertical profile of currents show how different a view of the deep ocean is now emerging. The tendency of currents to increase with depth below the permanent thermocline is so striking that it seems timely to point out that just this possibility was suggested recently by linearized theory (Rhines 1970). The work showed how short, yet quasi geostrophic, Rossby-topographic waves have a dominant mode that ceases to be independent of depth, and instead has faster currents near the bottom, due to the combined action of rotation, stratification and bottom slopes. This comment is not the first (nor probably the last) application of linear theory to such observations, for both Longuet-Higgins (1965) and Phillips (1966) have suggested their interpretation as Rossby waves of a constant-depth ocean model. Noting this vertical shear, Phillips was forced to invoke a mixture of the familiar baroclinic and barotropic modes. There are, however, objections to this, since those baroclinic modes are exceedingly slowly propagating, and cannot be expected to persist with such strong currents. Also, as Dr Swallow points out, the current directions do not vary greatly in the vertical, suggesting an explanation as a single mode rather than a mixture. The bottom slopes, however, can greatly alter both horizontal propagation and vertical stucture. In particular the presence of vertical shear no longer implies impossibly small frequencies.

High efficiency injection laser cavities

Abstract: The specification describes injection lasers employing heterosemiconductor structures for obtaining an enlarged crosssectional area cavity defined by an optical waveguide terminated by the cleaved faces of the semi-conductor structure (usually known as mirrors). The enlarged area of the cavity allows higher power output from the laser for the same power density on the mirrors. The power density is limited by damage to the mirrors. The waveguide produces an output consisting of two plane wave lobes for each mode. Techniques for mode enhancement are described from which higher ultimate power for a single mode and higher efficiency can e predicted without exciting modes of other order. Separation between the thresholds of competing modes can be enhanced, for example, by placing a spherical reflector in the path of one output lobe to focus the energy back into the original cavity while at the same time aperturing the mirror to block modes of other order. This expedient is based upon the uniqueness of the lobe angle for a given mode. Also described is a technique for combining the dual lobe output characteristic of this laser structure by using a beam splitter in reverse.

Light Interface Technology Improvement Investigation.

Abstract: : The report establishes a baseline model for an optical data link utilizing a single fiber bundle. This model is solely concerned with light interface technology (LIT) for digital signal transmission. Data link performance is characterized by the pulse amplitude, pulse rise and fall times, pulse delay, and signal-to-noise ratio of the photodiode output. The LIT link has been analyzed as an entirety considering four major areas; light emitting diodes, fiber optic light guide, fiber optic/diode interface, and photodiode. Fiber optic/diode interface has been investigated with regard to loss mechanisms of coupling light into and out of fiber bundles. Fiber optic light guides have been surveyed and evaluated. The three major types that have been given consideration are total internal reflection fibers, total internal refraction fibers and waveguide mode fibers. Space division multiplexing investigations considering Lambertian sources were completed for the TIR and SELFOC fiber types. Number of channels possible, optical cross coupling of fibers, and sampling effect are the main topics discussed. Analog properties of a typical link were investigated with respect to distortion. Experiments were completed using various wavelength LEDs and at various temperatures. (Author)