Abstract: A method and device for wavelength locking is provided, wherein an element having a wavelength dependent characteristic such as a Fabry Perot etalon is used to provide an output signal having an intensity that varies with wavelength. The intensity of a reference signal derived from an input signal is compared with an output from the Fabry Perot etalon to provide a feedback signal that corresponds to the frequency of the input signal. The system is calibrated before wavelength locking is performed to determine a ratio of intensities that determines a locked state or condition.

Abstract: An optical device is provided having an input and an output terminal spaced equidistant from an optical axis of a graded index lens. An at least partially reflective surface is disposed spaced but adjacent from another end face of the graded index lens. The optical path length from the input or output terminal to a first end face of the lens is equal to the optical path length from the other end face of the lens to the at least partially reflective surface. The graded index lens has a length that collimates light launched from the input terminal to the at least partially reflective surface. Moving the input an output terminals toward or away from one another changes the angle at which light exits the other end face of the graded index lens, and thus changes the angle at which light is incident upon the at least partially reflecting surface.

Abstract: A connection assembly for two or more optical fibers, which is hermetically sealed by means of a thin-walled flexible metallic sleeve. The assembly comprises two fiber ends, each terminating in an optical component such as a lens, the lenses having distal end faces held together so that light can pass from one fiber to the other through the lenses, and a fiber tube is mounted on each fiber adjacent the proximal ends of the respective lens and is hermetically sealed to the fiber. Each fiber tube has a metallic coating, and the thin-walled metallic sleeve is connected by solder to the metallic coatings on the fiber tubes. Preferably, the metallic sleeve has a central portion with bellows-like convolutions.

Abstract: An optical device is disclosed wherein a first GRIN lens and a second GRIN lens having their optical axes offset. The first GRIN lens has one or more input ports at an input end. The second GRIN lens is disposed to receive light from the first GRIN lens. A reflecting surface is coated onto a second end face of the second GRIN lens or alternatively is disposed adjacent to the second end face and positioned to reflect an input beam of light launched into the input end face of the first GRIN lens. The reflective surface is at a location where light incident upon it to be returned to the first GRIN lens is collimated. By placing a filter and third GRIN lens between the first and second lenses double filtering may be achieved at the pass band or pass wavelength of the filter. Furthermore, the more simple arrangement including only first and second lenses provides a means of directing light into and out of the device at different angles or directions with respect to the optical axis of the first lens.

Abstract: A device for coupling out of or into a transmission system which carries light signals is provided. A first optical fiber having a Bragg grating therein has its cladding optically coupled to a second optical fiber having a Bragg grating therein so as to allow at least a predetermined wavelength of light incident upon the first Bragg grating to be forward coupled from the core to the cladding and then to the core region of the second optical waveguide via the second Bragg grating.

Abstract: This invention relates to a reflective optical isolating device having at least two stages. In one embodiment a polarization independent optical isolating device has an input/output end and a reflector at another end. An isolator is disposed between the reflector and the input/output end. The isolator includes a non-reciprocal rotator in the form of a Faraday rotator, and in one embodiment the isolator also includes two reciprocal rotators. A first end of the isolator includes a birefringent crystal for separating an input beam of light in an input direction and for combing two beams of light in an output direction. The isolator also includes a second birefringent crystal at the other end for combining a separated beam of light on route to the reflector and for separating a combined beam of light in the output direction. In one embodiment two separate single isolation stages are provided, and in another embodiment two stage isolation is provided without providing two single stages of isolation.

Abstract: A method and optical system are provided which lessen spherical aberration normally associated with coupling small-diameter core optical fiber with a collimating lens. By coupling and optically aligned ends of thermally expanded core (TEC) fiber having a small output angular divergence to a GRIN lens, spherical aberration is significantly reduced.

Abstract: A hybrid filter includes a dichroic interference WDM filter closely coupled with a Bragg grating. Preferably the Bragg grating is housed within a sleeve having an end face that is directly coupled with an end face lens of the WDM interference filter. The entire filter can be placed within a single housing and temperature controlled. Etalon effects are lessened by placing the Bragg grating as close as possible to the WDM filter. Multiple hybrid filters of this type optically coupled to an optical circulator provided multi-channel demultiplexing.

Abstract: A method and device is provided wherein a reinforcement is provided for one or more optical fibers. One or more fibers are inserted into a sleeve made of a material that is substantially the same as the material of the cladding of the one or more optical fibers. The bore of the sleeve is sized to accommodate the one or more optical fibers; After the one or more optical fibers is inserted into the sleeve sufficient heat is applied to the sleeve for a duration to collapse the sleeve onto the one or more optical fibers. Preferably, the sleeve is a glass pre-form consisting substantially of 90% or greater silica.

Abstract: A voltage controlled attenuator for an optical telecommunication system comprises an optical attenuator placed between an input and an output lens for obstructing the path of an incoming light beam. The attenuator has variable attenuation (reflection, absorption, etc.) which is controlled for maintaining a preset power of the outgoing light beam. To this end, a fraction of the outgoing signal is diverted to an output detector by reflecting off an end face of a lens, and processed for obtaining a control signal representative of the output power. The control signal actuates a dc motor which displaces the attenuator to a position corresponding to a preset output power.

Abstract: A novel design for producing bandpass filters with essentially square shapes with little or no ripple in the passband zone. Filters are of the all-dielectric type that consist of multiple cavities of bandpasses with the first and last cavities consisting of four less layers than the inner cavities. The inner cavities all have the same number of layers. All of the cavities are separated from each other by quarter wave thick layers of low index material. Layers of low index material may be added between the filter and the entrance and exit mediums. Multiple half-waves are added to the outer cavity quarter-wave stacks in particular and also may be added to some of the inner cavity stacks, These sharpen the transition from low transmission to high transmission without unduly adding ripple to the high transmission zone. The thickness of the first few layers and last few layers may be altered to enhance the transmission of the filter by matching the index structure of the passband to the adjacent mediums.

Abstract: A device for connecting a first optical fiber end held by a first connector plug selectively to second or third optical fiber ends held by different types of connector plugs, in which each different type of plug has an associated connector socket, these sockets each including a non-circular connector flange and each having a ferrule alignment sleeve held by a retainer bushing projecting outwardly from the connector flange, the alignment sleeves being of the type suitable for receiving cylindrical ferrules attached to each fiber end. The device comprises a fixed part having an aperture extending between its inner and outer surfaces, and having a connector adapter projecting from the inner surface and suitable for receiving the first connector plug, and having a radially extending outer surface portion accessible from the outer surface and surrounding a recess suitable for receiving the retainer bushing of another connector plug.

Abstract: A device for distributing an optical signal has an optical waveguide with a plurality of gratings disposed in series therein, the gratings having a predetermined reflectivity response within a specific wavelength range; an optical circulator having at least three ports, one of the ports serving as an input port for receiving the optical signal, and another port for removing at least a part of the optical signal reflected from one of the gratings; and control means for individually controlling at least some of the gratings to effect a change of the wavelength range of the reflectivity response of the gratings. The change may be a shift, an expansion or a compression of the range. The device can function as a signal distributor (router), an equalizer or a demultiplexer. The reflectivity response is preferably a sloped response.

Abstract: A system for automatically aligning optical components without active alignment techniques is provided. Optical components are placed into an alignment sleeve having an opening with a diameter sized to tightly receive optical components. Optical fibers having thermally expanded core ends are used to coupled light within the alignment sleeve. In instances where the optical fibers are offset from the longitudinal axis of the sleeve, means are provided to prevent rotation of an optical fiber tube holding the optical fibers.

Abstract: An attenuator capable of controllably attenuating at least two wavelengths of light is configured to have an optical waveguide section having at least two Bragg gratings disposed therein in series. The Bragg gratings have a sloped reflectivity response within a predetermined wavelength range. The sloped response is a function of refractive index variations within each of the grating elements. By compressing or expanding at least one of the gratings, the periodicity is modified so as to shift its central wavelength within a predetermined wavelength range.

Abstract: A lensing system is provided for coupling light from one optical fiber to another through a plurality of graded index (GRIN) lenses. The system is capable of coupling light of two significantly different wavelengths in a relatively efficient manner. More specifically, a first GRIN lens having at least two ports on an outwardly facing end face is provided for coupling light of one of the wavelenghts from one of the at least two ports to another of the at least two ports. A second GRIN lens typically being about one half pitch, having an end face juxtaposed to an end face of the first GRIN lens, is provided for, in combination with the first lens, adjusting for differences in the two significantly different wavelengths, so that light will efficiently be coupled between a third graded index lens and the first graded index lens that are of different lengths to accommodate for the different wavelengths of light.

Abstract: A multi-pass Fabry-Perot etalon, or bandpass, filter, has a Fabry-Perot cavity defined by two partially reflective mirrors with a gap therebetween and a third reflecting mirror positioned adjacent said two mirrors and arranged to reflect substantially any light eliting said cavity back into it. The filter can replace two single-pass Fabry-Perot etalon filters and can provide lower signal loss and simpler wavelength control.

Abstract: An optical tap/coupler consists essentially of a two graded index lenses having a holographic beam splitter (HBS) in between. The HBS independent of polarization state and wavelength of an input light beam splits an incoming beam into at least two beams. The two beams are directed to two separate locations or ports at an end face of one of the graded index lenses thereby providing a main beam and a tap beam at an output of the device. The device is compact and can accommodate other optical components between the two graded index lenses.

Abstract: A wavelength filter for use with optical fibers comprises a plurality of filter units, each unit comprising first and second collimating lenses separated by a filter element, the filter elements of the two units being capable of passing first and second wavelengths respectively, and each unit being such as to reflect light transmitted by the filter element of each of the other units. A first of the units has its first lens connected to an input optical fiber and also connected to a first connecting optical fiber positioned so that one of these optical fibers is capable of receiving light from the other fiber reflected off the filter element of the first unit. The first unit has its second lens connected to a second connecting optical fiber carrying light of a first wavelength transmited from the input optical fiber through the first filter unit.

Abstract: An optical switch has a stepping motor with a fiber faceplate on which are mounted end portions of output optical fibers terminating in GRIN lenses. The end portions are arranged along a pitch circle. The faceplate is spaced from the stepping motor and the diameter of the pitch circle is smaller than the diameter of the stepping motor, the output fibers diverging from the faceplate towards the motor and beyond in a space-saving arrangement. The stepping motor drives a movable arm with attached end portion of an input optical fiber, also with a GRIN lens, into one of a plurality switching positions. The connection between the fibers and the lenses and also the relative axial arrangement of the paired lenses in the switching positions is offset to reduce or minimize the reflection of light transmitted from the input fiber to the output fiber, back to the input fiber.