Abstract: The characteristic pass and rejection bands of an interference filter may be altered by changing the angle of incidence of light upon the filter. If the input beam is first collimated by a GRIN lens before it is transmitted to the interference filter, the characteristic wavelength bands of the filter can be altered by altering the distance of the input beam from the axis of the GRIN lens. Therefore, ferrules having imbedded therein input/output optical fibers may be provided to vary the distance of the input and output optical paths from the axis of the GRIN lens so that the desired spectral components in these paths are rejected or passed by the filter for performing multiplexing and demultiplexing.

Abstract: An optical coupler is formed by a GRIN lens having an axis and an optical medium contiguous to the GRIN lens but having an index of refraction that is different from that of the lens. An input optical fiber carries an input optical signal along a path substantially parallel to the axis of the lens but is offset from its axis. The lens collimates the input optical signal into a beam that impinges on the interface between the lens and the optical medium at a small angle. Fresnel reflection of the collimated beam at such interface is focused by lens to an output optical path also substantially parallel to the axis of the lens but at the same offset to the axis from the input optical path. The tapping percentage can be controlled by choosing an optical medium having the desired index of refraction. Additional interfaces can be formed between the optical medium and additional media, such as a thin glass disk for additional Fresnel reflections that are also coupled to the same output fiber.

Abstract: A tunable filter includes a filter whose characteristic wavelength band changes with the angle of incidence of the incoming light beam with respect to its normal direction, a motor for rotating the filter in order to change the angle of incidence, and a controller controlling the motor to rotate the filter by an amount so that the filter has a desired characteristic wavelength band. A variable attenuator for adjusting insertion loss between an input light beam and an output light beam includes a pair of input and output collimators, a cam connected to at least one of the two collimators, and a motor for rotating the cam for displacing one collimator relative to the other in order to adjust the insertion loss between the input and output light beams.

Abstract: A demultiplexer employs collimators for directing light of different wavelengths towards a filter so that light of one wavelength may be passed while reflecting light of other wavelengths. Light of the wavelengths that are passed or reflected may again be directed towards the same or different filter for further demultiplexing. The filter used has a characteristic wavelength band that varies with the angle of incidence to the filter. The same types of filter may be used for multiplexing. An input beam is passed through a filter at an angle of incidence at which light of a different wavelength would be reflected. Thus two input beams carrying such two wavelengths are directed towards the same location of the filter on opposite sides of the filter so that the reflected light of one wavelength will emerge as one beam with light of the other wavelength that passes through the filter. The emerging beam is then collected to multiplex light of the two wavelengths.

Abstract: A technique for determining the existence and location of faults within an optical fiber is disclosed. The technique is accomplished through the use of fault detecting means such as an optical time domain reflectometer used in conjunction with an in-line optical filtering device which filters out selected wavelengths of optical radiation within an optical fiber. Specifically, the filtering device comprises two GRIN lenses placed along the optical path of the fiber such that light within the fiber is collimated by the first GRIN lens, and returned to the fiber by the second GRIN lens. The means of wavelength selection is achieved by an optical filter coating on the surface of at least of the GRIN lenses. The optical filter can be an edge pass filter, a band-pass filter, or an absorption filter. The invention provides for a broadband wavelength selection, which is not achieved by fused biconic type wavelength division multiplexers.

Abstract: A technique for causing the distribution of the state of polarization of an optical signal carried in a single-mode optical fiber to be substantially diversified over a time interval. When such a depolarized optical signal is fed into an optical detector, the polarization dependent loss (PDL) of the optical signal attributable to the detector is thereby normalized. By normalizing the PDL attributable to the detector, it is then possible to more accurately measure any PDL of the optical signal attributable to the optical signal passing through an optical device under test.

Abstract: The end portions of a number of optical cables each having one or more optical fibers are fixed onto the conical surface of a supporting frame. The end portion of a movable cable with one or more optical fibers is rotated about the axis of the conical surface so that its end portion is aligned with one of the fixed cables and so that the fibers in the movable cable are optically aligned with the fibers in such fixed cable. The movable cable is rotated by a stepping motor to accomplish the switching action.

Abstract: A fiberoptic lamp includes one or more optical fibers which include an emitting material so that optical energy given off by the emitting material will be transmitted by the fibers. The lamp has a housing which holds the fibers and an exciting device where energy given off by the exciting device causes the emitting material of the fibers to emit optical energy. This eliminates the need to channel the energy of the exciting device or the optical power emitted by the emitting material into apertures or ends of optical fibers and improves the efficiency of the lamp.

Abstract: Two fixed input optical fibers may be aligned with two movable output optical fibers. The two output fibers are moved by exchanging the positions so that either output fiber may be optically aligned with either input fiber. In another optical switch either one of two movable fibers may be optically aligned with either one of two fixed fibers by rotating the movable member. In yet another optical switch a movable fiber may be aligned with one of a number of fixed optical fibers by rotating the movable member using a stepping motor. The angular positions of the fixed fibers are such that the input fiber is optically aligned with any one of the fibers by rotating the input fiber by a number of steps of the stepping motor.

Abstract: Two fixed input optical fibers may be aligned with two movable output optical fibers. The two output fibers are moved by exchanging the positions so that either output fiber may be optically aligned with either input fiber. In another optical switch either one of two movable fibers may be optically aligned with either one of two fixed fibers by rotating the movable member. In yet another optical switch a movable fiber may be aligned with one of a number of fixed optical fibers by rotating the movable member using a stepping motor. The angular positions of the fixed fibers are such that the input fiber is optically aligned with any one of the fibers by rotating the input fiber by a number of steps of the stepping motor.