Showing papers on "Dispersion-shifted fiber published in 1974"

Phase‐matched three‐wave mixing in silica fiber optical waveguides

Abstract: We have observed phase‐matched nonlinear mixing in a silica fiber optical waveguide using the dispersion of the guide modes to compensate for bulk dispersion. A tunable dye laser signal is mixed with a fixed‐frequency pump wave to generate output in specific waveguide modes at different frequencies. The technique is useful as a probe of waveguide properties and for the study of the nonlinearities of the medium.

Hyperbolic type optical fiber lens coupler for coupling the fiber to an optical line source

Abstract: The angular profiles of optical radiation emitted by certain conventional optical sources, such as a semiconductor P-N junction laser, are similar to those of optical line sources. In order to increase the optical coupling efficiency from such optical line sources to an optical fiber, the input end of the fiber is shaped essentially into the form of a hyperbolic cylindrical lens by first forming a flat wedge at this end of the fiber and then finishing the wedge to the desired essentially hyperbolic cylindrical surface. This finishing can be accomplished by either a flame (heat) type polishing or a mechanical (fine abrasive) type polishing.

Optical fiber power taps employing mode coupling means

Abstract: In an optical fiber power tap, signal power is coupled out of an optical fiber waveguide by a dielectric body disposed in a coupling relationship laterally offset from an intermediate length of the fiber, and is converted to a representative electrical signal suitable for utilization by a photodetector disposed adjacent to the dielectric body. In accordance with the disclosed invention, the operation of the fiber tap is improved by combining therewith means for coupling a portion of the signal power in the fiber from lower order modes to higher order modes. The mode coupling means illustratively comprises a pair of corrugated plates which is pressed against the fiber to periodically deform a region of the fiber just preceding the fiber tap. Provided the spatial periodicity of the corrugations in the plates is properly selected, and the pressure exerted on the plates is sufficiently large, the periodic deformation of the fiber causes the desired higher order mode coupling, and assures that there is sufficient power distributed in the higher order modes of the fiber for the dielectric coupling body of the fiber tap to couple out. The mode coupling means can be employed to provide an adjustable optical fiber tap, and can facilitate the tapping of clad fiber waveguides.

GaAs Twin-Laser Setup to Measure Mode and Material Dispersion in Optical Fibers.

Abstract: Two synchronously self-pulsing GaAlAs lasers, emitting at slightly different wavelengths, are combined in a setup which evaluates mode and material dispersion in multimode fibers. The results show that material dispersion which causes a pulse broadening of 3.6 ns/km, which may represent a serious limit to the bit rates achievable in a multimode fiber system using an LED source.

Measurements of the Baseband Frequency Response of a 1-km Fiber

Abstract: Typical light-emitting diodes have a spectral width between 300 A and 500 A. This is sufficient to cause significant pulse broadening as a result of material dispersion in a long optical glass fiber. An experiment was performed to measure the magnitude of this effect in a fiber of 1-km length. The experiment measures the average intensity transfer function of the fiber.

Fiber distributed feedback laser

Abstract: Utilizing round optical fibers as communication channels in optical communication networks presents the problem of obtaining a high efficiency coupling between the optical fiber and the laser. A laser is made an integral part of the optical fiber channel by either diffusing active material into the optical fiber or surrounding the optical fiber with the active material. Oscillation within the active medium to produce lasing action is established by grating the optical fiber so that distributed feedback occurs.

Pulse Widening in a Multimode Optical Fiber Excited by a Pulsed GaAs LED.

Abstract: A 1-km length of low-loss multimode optical fiber made by Corning Glass Works was excited by the pulsed output of a GaAs LED. The pulses were 3.6 nsec wide and had a spectral width of 460 A. After traveling through the fiber, the pulse had a half-power width of 6 nsec, of which 4.2 nsec was estimated to be due to material dispersion.

Optimal trade-off of mode-mixing optical filtering and index difference in digital fiber optic communication systems

Abstract: In a digital fiber optical communication system, the optical power required at the receiver input to achieve a desired error rate depends upon the shape of the received pulses. In systems employing multimode fibers and/or broadband sources, we can experience pulse spreading in propagation because of the group velocity differences of different modes or because of dispersion. In an effort to control or compensate for pulse spreading, we can trade off coupling efficiency between the light source and the fiber (by varying the core-cladding index difference or bandlimiting the source), scattering loss in the fiber (by introducing mode coupling), and equali sation in the receiver at baseband. This paper investigates the optimal trade-off for various fiber-source combinations.

Propagation of a semiconductor laser pulse in an optical fiber

Abstract: Frequency modulation of the optical carrier, due to heating a p-n junction, is a characteristic feature of the injection laser radiation. This feature is allowed for in a calculation of the distortion of a pulse generated by such a laser and traveling in an optical fiber characterized by frequency dispersion. The optimal parameters of the fiber, corresponding to the maximum narrowing of the pulse, are determined.