Abstract: A programmable broadband N×N cross-connect switch includes an N×N wavelength coupler combined with N tunable lasers, N modulators and N optical receivers. Each of the N tunable lasers can selectively produce N different wavelengths. The coupler couples the N wavelengths to the N modulators. The N modulators modulate the N wavelengths using N input electrical signals, each modulator being selectable by choosing a laser wavelength. The N optical receivers receive and detect the N modulated wavelengths to produce N output electrical signals therefrom, each receiver receiving and detecting a different one of the N different wavelengths. By selecting a laser wavelength a particular modulator and receiver is selected so that a modulated signal, formed at the selected modulator when an input electrical signal modulates the selected wavelength, is switched to the selected receiver.

Abstract: A parallel ring network is restorable upon sensing a failure of a transmission media. A central transmitter is coupled to one end of a first transmission medium. A central receiver is coupled to one end of a second transmission medium. A central sensor senses a transmission media failure centrally and provides a central alarm. In response to the central alarm, the central receiver is coupled to another end of the first transmission medium and the central transmitter is coupled to another end of the second transmission medium. At least one local station has a local receiver, a local transmitter, a local sensor for sensing a transmission media failure locally and providing a local alarm, and a local switch. In response to the local alarm, the local switch moves from a first position to a second position. When the local switch is in the first position, the local transmitter is coupled to the second transmission medium and the local receiver is coupled to the first transmission medium.

Abstract: A monolithically integrated laser which is rapidly tunable over a wide optical frequency range comprises a frequency router formed in a semiconductive wafer defining a tuned cavity. A control circuit applies electrical energy to predetermined controllably transmissive waveguides connecting the frequency routing device with reflective elements defined in the wafer. This tunes the laser to a desired one of a plurality of optical frequencies. Application of such electrical energy creates frequency selective pathways through the wafer able to support selected lasing frequencies. This laser is economical to construct and is useful in high capacity, high speed optical communications networks.

Abstract: A parallel ring network is restorable upon sensing a failure of a transmission media. A central transmitter is coupled to one end of a first transmission medium. A central receiver is coupled to one end of a second transmission medium. A central sensor senses a transmission media failure centrally and provides a central alarm. In response to the central alarm, the central receiver is coupled to another end of the first transmission medium and the central transmitter is coupled to another end of the second transmission medium. At least one local station has a local receiver, a local transmitter, a local sensor for sensing a transmission media failure locally and providing a local alarm, and a local switch. In response to the local alarm, the local switch moves from a first position to a second position. When the local switch is in the first position, the local transmitter is coupled to the second transmission medium and the local receiver is coupled to the first transmission medium.

Abstract: A combined wavelength router and switch apparatus for use in an optical communication system is disclosed. The apparatus includes arrays of optical signal demultiplexers, wavelength division switches, space division switches and multiplexers, arranged in a manner that can increase the connectivity of an optical system using wavelength division multiplexed (WDM) signals. In several embodiments, time-multiplexed wavelength division switches and time-multiplexed space division switches may be used to increase further the degree of connectivity of the system or to reduce the number of wavelength division switches and space division switches required. Additional arrays of wavelength division switches or time-multiplexed wavelength division switches may be included to allow carrier frequencies to be shifted to meet the channel ordering requirements of the optical system.

Abstract: An optical frequency translator includes a frequency routing device formed on a semiconductive wafer between two reflective facets forming a laser cavity. Waveguides associated with the device each contain an integrated optical amplifier selectively acting as a gate preventing the flow of optical energy through a respective waveguide or as a gain-providing element which amplifies optical energy flowing through a respective waveguide. When a selective one of the optical amplifiers is activated with bias current the optical energy produced by this current operates in conjunction with the optical energy of the input signal so that lasing action occurs between the reflective facets. The lasing action occurs along a predetermined path determined by the optical amplifier or amplifiers that are activated. The lasing action in this particular path is supported at a particular selected frequency. This particular frequency is the frequency to which the input signal is to be translated.

Abstract: In a laser control arrangement for tuning a laser a portion of the optical signal exiting a resonator is directed to the input of an optical frequency routing device. The routing device has a plurality of outputs each for receiving one of the frequencies supplied by the laser. Each output is coupled to a photodetector. When the laser emits a frequency of light corresponding to one of the resonant frequencies of the resonator, the resonant frequency will appear on one of the outputs of the routing device and will be detected by the photodetector coupled to that output.

Abstract: Communication between an upstream point, such as a TV-source headend followed by a fiber optic line, and a number of downstream points, such as coaxial cable connected subscriber locations, is achieved by wavelength or frequency demultiplexing a spectrum of downstream radio-frequency signals with a surface-acoustic-wave (SAW) demultiplexer-multiplexer and distributing the demultiplexed signals to the downstream points, for example through the cables.

Abstract: A tunable waveguide grating includes a plurality of N waveguides which define N optically transmissive pathways. A plurality of (N-1) electrodes are arranged in the pathways such that the kth pathway contains (k-1) electrodes, where 0<k<N. As a result of this arrangement, an optical signal propagating through the kth pathway will experience a phase shift provided by each of the (k-1) electrodes arranged in that pathway. Consequently, in contrast to prior tunable optical gratings, each electrode may contribute a phase shift to the portions of the signal propagating through several waveguides and hence as the number of waveguides increases no individual electrode is required to produce relatively large phase shifts.

Abstract: A tunable laser formed on a semiconductive wafer comprising a plurality of monolithically integrated optical amplifiers and a planar optical multiplexer is disclosed. According to the invention, one of the optical amplifiers is activated by energy, which amplifier produces a signal. The signal is carried along a waveguide associated with the optical amplifier and enters a reflective Dragone router, which is the preferred optical multiplexer. The reflective Dragone router functions, in conjunction with the activated optical amplifier, to define a wavelength selective optically transmissive pathway to create lasing action. Facet mirrors are cleaved in the semiconductive wafer defining the lasing cavity which includes the optical amplifiers, associated waveguides and the reflective Dragone router.

Abstract: A monolithically integrated laser which is rapidly tunable over a wide optical frequency range comprises a frequency router formed in a semiconductive wafer defining a tuned cavity. A control circuit applies electrical energy to predetermined controllably transmissive waveguides connecting the frequency routing device with reflective elements defined in the wafer. This tunes the laser to a desired one of a plurality of optical frequencies. Application of such electrical energy creates frequency selective pathways through the wafer able to support selected lasing frequencies. This laser is economical to construct and is useful in high capacity, high speed optical communications networks.

Abstract: An N.times.N passive star coupler can be used to provide a high performance optical data network to interconnect many users at gigabit rates. Ignoring excessive losses, a signal incident on any input port is divided equally between all of the output ports. The average power at all of the input ports N of the star is equal to the average power at all of the output ports N. But, the power per channel at each output port is equal to only 1/N of the applied power. This loss which is due to splitting cannot be recovered by an amplifier at either the input port or the output port of the star coupler unless the amplifier saturation power is greater than the transmitter power. This invention solves the problem of amplifier saturation.

Abstract: One aspect of the invention is a Fabry-Perot cavity which has in part a waveguiding portion and in part a nonwaveguiding portion. In this manner, a cavity is constructed whose length would be too short to manipulate effectively if it were comprises exclusively of a waveguiding portion, and whose length might have unacceptable diffraction losses if it were comprised exclusively of a nonwaveguiding portion. In the inventive device the resonant wavelength can be adjusted by varying the length of either the gap or the waveguide or both. The device can be advantageously constructed and aligned using fiber coupling technology.

Abstract: Stabilized, single-mode operation of semiconductor lasers is obtained by introducing longitudinally spaced variations in the effective refractive index along the active waveguiding medium, where said index changes have a spatial period corresponding to many half-wavelengths of the guided optic wave. Because the spatial period of the variations is relatively long, as opposed to half an optical wavelength used in the prior art distributed feedback lasers, a laser in accordance with the invention is much easier to fabricate.

Abstract: A means for aligning components of an optical system without the use of conventional optical equipment is disclosed. This means includes the use of a pair of electrodes in proximity with the light guiding portion of a pyroelectric system element. The absorption of light in the waveguide produces a current in the pyroelectric material tht is monitored at the electrodes. Alignment of the system components is achieved by adjusting their relative position to increase the monitored signal.

Abstract: The ridge-structure in a ridge waveguide laser is notched at periodic intervals to produce a longitudinally crenelated ridge, and the electrode on the ridge side of the laser is alloyed only to the topmost surfaces of the ridge. As a result, the active region of the laser is pumped only in the regions that are underneath the topmost surfaces of the ridge, and the laser is caused to prefer the longitudinal modes whose maxima coincide with the spatial Fourier components of the pumped regions.

Abstract: Optical power is coupled into an optical waveguide system such as an optical fiber with maximum efficiency by a superluminescent light-emitting diode having lateral confinement of the light in the junction plane. The waveguide developed in the light-emitting diode is constructed to have an effective numerical aperture equal to the numerical aperture of the optical waveguide, and the refractive index n, the length L and width D of the waveguide in the diode is constructed such that the parameter nD/2L is much less than the numerical aperture. As a result, the inverted population of electrons within the active region are utilized with maximum efficiency to develop rays that are coupled into, and can be guided by, the optical waveguide system.

Abstract: Optical waveguides are formed in semiconductors, for example, InP and InGaAsP, by indiffusion of selected metal atoms.

Abstract: A means for aligning components of an optical system without the use of conventional optical equipment is disclosed. This means includes the use of a pair of electrodes in proximity with the light guiding portion of a pyroelectric system element. The absorption of light in the waveguide produces a current in the pyroelectric material that is monitored at the electrodes. Alignment of the system components is achieved by adjusting their relative position to increase the monitored signal.

Abstract: There is disclosed a method of fabricating an optical waveguiding surface layer in an optically transparent crystalline substrate, such as lithium niobate, by selectively indiffusing metal ions, such as titanium, into the crystal to effect an increase in the index of refraction of a surface portion thereof. The indiffused metal ions serve to raise both the ordinary and extraordinary refractive indices of the substrate by amounts which are of the order of one percent at the diffusion surface and which gradually decrease by one-half at depths of the order of one micrometer below the surface. By properly adjusting the relevant diffusion parameters in the method, the important surface waveguide characteristics can be independently controlled.