Bell Telephone Laboratories

At&t Bell Laboratories

Stewart E Miller

John A Copeland, Iii

Kinichiro Ogawa

An active tap for use in an optical multiple access network is disclosed. The tap comprises a semiconductor substrate on which the electronics associated with an active parallel path are fully integrated. These include optical detectors, amplifiers and light emitters formed using standard semiconductor fabrication techniques. A section of fiber, incorporated as an integral part of the tap structure, is provided with a pair of longitudinally spaced discontinuities for deflecting a portion of the incident signal onto the detector and for redirecting the output from the light emitter along the through-path. Alternatively, the tap substrate can be provided with a groove for receiving a fiber segment located anywhere along the distribution network.

Active optical fiber tap

Two-dimensional semiconductor chips are stacked to form a three-dimensional array in which coupling between chips is effected optically. This permits the use of smaller chips, with a corresponding higher yield, and serves to reduce the chip area required for interconnecting leads. It also reduces the internal interconnection path lengths which, at present, limit the speed of operation.

Optically coupled integrated circuit array

A new transmission system configuration is disclosed which takes advantage of the special properties of lightwave devices and the extensive availability of frequency space on optical fibers. The system employs a combination of time and frequency multiplexing at the transmitter, and frequency demultiplexing at the receiver. An advantageous result of combining time and frequency multiplexing is to relax the tolerance requirements on filters at the transmitter. A further advantage is to minimize the effects of mode dispersion introduced by the fiber.

Optical communication system

An electro-optic integrated circuit is disclosed wherein the long electrical connections normally present on a large scale integrated circuit are replaced by an optical waveguide layer. A plurality of epitaxial layers are grown on a single substrate and at least three of the plurality of epitaxial layers are grown with bandgaps that are suitable for optical sources, detectors and waveguiding. These primary layers are separated from each other by a barrier layer having a bandgap greater than either of the adjacent primary layers. Two of the layers adjacent to the substrate are grown to accommodate electrical devices that can be used to couple electrical signals to the optical source layers and to amplify electrical signals provided by the optical detection layer.

Multilayered optical integrated circuit

Optical fibers having enhanced mode coupling produced by an asymmetric refractive index profile that varies periodically along the length of the fiber are described. The prescribed variations are obtained by means of a fabrication process that includes periodically varying the source of at least one of the fiber materials in a direction transverse to the fiber-drawing direction. This transverse periodicity is translated into the desired longitudinal periodicity along the fiber by the fiber-drawing process.

Optical fiber with enhanced mode coupling

Transmission configurations are described for providing usable service despite the complete interruption of one or more of several transmission links. This is accomplished by encoding (11) the information content of each of a plurality of input signals (S.sub.1, S.sub.2 . . . S.sub.n) into a multiplicity of encoded signals (s.sub.1, s.sub.2 . . . s.sub.m) for simultaneous transmission along a multiplicity of transmission links (13.1, 13.2 . . . 13.m). At the receiver, a decoder (12) recovers the individual input signals. By accepting temporarily either a bandwidth or a signal-to-noise reduction, service is continued even though one or more of the transmission links fails.

Fail-safe transmission system

A method of fabricating an optical fiber having an asymmetric refractive index profile that varies periodically along the length of the fiber is described. The prescribed variations are obtained by means of a fabrication process that includes periodically varying the source of at least one of the fiber materials in a direction transverse to the fiber-drawing direction. This transverse periodicity is translated into the desired longitudinal periodicity along the fiber by the fiber-drawing process.

Method for fabricating optical fibers with enhanced mode coupling

The separate steps of forming an optical fiber preform and then drawing the fiber are combined into an essentially simultaneous process wherein a 'stub' preform (18) is formed by means of the so-called 'vapor-phase axial-deposition' method while the fiber (17) is simultaneously drawn from the end of the stub that is opposite to the end upon which the particulate matter (14, 15) is being deposited.

Method of fabricating optical fibers

A terminating portion of an optical fiber waveguide having a polished beveled end is laterally disposed directly on the light-emitting surface of a light-emitting diode (LED). The light power coupled into the fiber consists of two components: the light power directly coupled into the fiber all along the region of contact between the fiber and the light-emitting surface; and the light power reflected by the beveled end and directed along the fiber axis.

Coupling arrangements between a light-emitting diode and an optical

Dispersion is reduced in a graded index optical fiber having a finite number of core layers by introducing slow longitudinal variations into the thickness of each layer. The thickness of each layer varies between maxima and minima, the latter being proximate to zero.

Optical fiber having reduced dispersion

Dispersion is reduced in a graded index optical fiber having a finite number of core layers by introducing slow longitudinal variations into the index of refraction of each layer. The index of refraction of each layer varies between a maximum which is proximate in value to the minimum index of refraction of the more central radially adjacent layer and a minimum which is proximate in value to the maximum index of refraction of the next furthermost radially adjacent layer.

Directional optical waveguide couplers for use with planar-form optical waveguides or optical fiber waveguides are disclosed. In the coupler arrangements, light energy propagating in a direction of interest in the core of a cladded optical waveguide is first coupled into a selected region of the cladding by a mode coupling means and then coupled out of the selected cladding region by a branching optical waveguide or power tap for subsequent conversion to a representative electrical signal. The selected region of the cladding is isolated from spurious cladding modes by a pair of stripper-absorber means to ensure that the coupled out light energy is derived only from the core-guided modes propagating in the direction of interest.

Directional optical waveguide couplers

A process for manufacturing preforms from which clad optical fibers having longitudinal, eccentric, azimuthal index inhomogeneities may be drawn. In one embodiment, the known CVD process for making preforms is modified by the use of asymmetric heating to produce circumferentially alternating deposits of doped and undoped glass which act as the fiber core when the preform is subsequently collapsed and drawn into a fiber.

Method for forming optical fiber preform

An improved technique for producing optical fibers is disclosed. In this technique the optical fiber preform is fabricated by axial deposition from a direction along the preform axis as opposed to radial deposition from a direction perpendicular to the preform axis. The instant technique does not require a cylindrical mandrel and, consequently, the technique does not require removal of a mandrel and the collapse of a non-solid preform prior to drawing. In addition to these advantages, the technique may be used to form optical fibers with highly resolved longitudinal gradations in index of refraction. The resolution of such gradations when formed using the instant technique is limited only by the deposition rate and the ability to rapidly alter the concentration of the material being deposited.

Axial fabrication of optical fibers

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.

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Locust, NJ, United States of America

Stewart E Miller