Abstract: Fiber optic delay lines in the form of a modified corporate feed having progressive phase delays and a corporate feed having equal phase delays are used to couple RF modulated light signals to detecting, mixing, amplifying and radiating devices of an active array radar. Different RF signals may be sent over the same fiber delay lines using different light colors (or wavelengths) so that the RF modulated signals in the fiber delay lines do not interact with each other. The RF signals can be put on and taken out of the fiber lines using wavelength division multiplexers, for example. This provides an array with a single optical manifold that allows simultaneous full aperture operation at multiple frequencies and/or beams over a wide operating frequency range.

Abstract: Mixing and modulating methods are described for nonlinear optical amplifiers (30) which can generate intermodulation products of radio-frequency signals in an optical carrier signal (26) without the penalty of an optical conversion loss and without the need for radio-frequency mixers, electro-optic modulators and expensive polarization-maintaining optical fibers. The radio-frequency signals can be applied to either a bias port (36) or an optical input port (32) of the optical amplifier and are used to upconvert and downconvert signals in phased-array antenna and remote antenna embodiments of the invention.

Abstract: An optical heterodyne system provides the radiation source and beam scan control of a millimeter wave (MMW) array antenna. The heterodyne system is an optical feed system to produce the MMW by mixing the optical outputs from two lasers, distribute the signal source to an array of radiating elements through a Rotman lens and optical fibers, generate the differential phase shift for beam scan in the optical domain, change the beam direction by switching the input laser being used to illuminate the Rotman lens or by varying the frequency of one of the laser sources. The feed system includes a plurality n-1 lasers spaced along the transmit side of the lens, and a center laser disposed on the center axis of the transmit side. A l:n switch receives a command input to determine which of the n-1 lasers will operate. The beat frequency between the center laser operating frequency and that of the n-1 lasers is the MMW frequency.

Abstract: An antenna system includes a set of symmetrically located center-fed and segmented dipole antennas embedded on top of a frequency selective photonic bandgap crystal. A two-dimensional array of microelectromechanical (MEM) transmission line switches is incorporated into the dipole antennas to connect the segments thereof. An MEM switch is located at the intersection between any two adjacent segments of the antenna arm. The segments can be connected (disconnected) by operating the switch in the closed (open) position. Appropriate manipulation or programming of the MEM switches will change the radiation pattern, scanning properties and resonance frequency of the antenna array. In addition, an MEM switch is inserted into the crystal to occupy a lattice site in the 3-dimensional crystal lattice.

Abstract: An apparatus and method for frequency translation of true time delay signals in a phased array radar system is provided. A local oscillator signal is true time delayed or modulo 2.pi. phase shifted and then mixed with a true time delay beamsteering signal from a true time delay circuit to produce a frequency translated transmit signal which is supplied to an antenna element. A receive signal received by an antenna element is mixed with a true time delayed or modulo 2.pi. phase shifted local oscillator signal to provide a frequency translated receive signal. The frequency translated receive signal can then be passed through a true time delay circuit and other subsequent processing circuitry. The frequency translation permits higher frequency transmit and receive signals to be used with lower frequency true time delay devices.

Abstract: Optoelectronic switching apparatus employing optoelectronic switching devices interconnected by optical media having different delay lengths and an multiport optical coupler. The optoelectronic switching apparatus provides for a multibit true-time-delay beamsteerer for beamsteering phased array antennas. The present invention combines two types of optoelectronic devices, lasers and photodiode switches, using an interconnected passive optical network comprising the optical fibers and the optical coupler. The switches, and input and output signal networks coupled to the respective switches, are controlled using a control signal generator. Using this scheme, any input can be independently selected and a signal can be routed to any output. Furthermore, the product of the total number of different interconnect paths (N.times.M) is provided which provides a greater number of delay lengths than is provided by using only one type of switch (i.e. laser (N) or photodiode (M)) alone.

Abstract: A single transmission optical fiber is used to transmit RF signals of the same frequency but different polarization from a source to a polarization diversity receiver without introducing interference between the signals. The incoming signal of one polarization modulates a first laser transmitter operating at one wavelength, and the incoming signal of the other polarization modulates a second laser transmitter operating at a different, second wavelength. The two modulated optical beams are combined in an optical coupler whose output is connected to the transmission fiber leading to the polarization diversity receiver. At the receiver, a wavelength division multiplexing coupler is used to separate out the two modulated optical carriers. The two RF signals used to modulate the laser transmitters are separately recovered via photodiode detectors to provide inputs to the polarization diversity receiver.

Abstract: When an optical signal is modulated at two modulation frequencies, third order intermodulation distortion (IMD) is eliminated by inducing an out-of-phase signal that is complementary to the modulated signal, and cross-coupling the two signals with each other to remove the third order terms. An optical beam in a first waveguide is electro-optically modulated and coupled with a second waveguide to induce the out-of-phase complementary beam therein. A second optical coupler is provided that cross-couples the beams in the two waveguides downstream from the first optical coupler. The optical coupling coefficients, the coupler lengths, and the differential between the optical propagation coefficients of the two waveguides within the first coupler are selected empirically to substantially negate third order IMD. The differential in propagation coefficients is established by the DC bias of the modulation signal.

Abstract: A bidirectional optical fiber (12) amplifier suitable for use in a dual payout fiber-optic communication link (10) is disclosed herein. The inventive amplifier (12) is typically encasted in a shell or service loop, and is preferably connected between first and second optical fiber segments (18 and 20). The amplifier (12) includes a pump laser (102) for generating optical energy of a first wavelength. A wavelength selective optical coupler (82), in optical communication with the first fiber segment (18) and the pump laser (102), combines optical energy propagating through the first fiber segment (18) with the optical output of the pump laser (102). The amplifier (12) of the present invention further includes a doped optical fiber (114), optically connected between the wavelength selective optical coupler (82) and the second optical fiber segment (20), for amplifying optical energy within a predetermined wavelength spectrum passing therethrough.

Abstract: A high speed opto-electronic crossbar switch 10 disposed to selectively connect signals carried by first and second input optical beams to an output node 42. The inventive switch 10 includes a selectively actuatable photodetector network 22 for converting the signals carried by the first and second input beams to electrical output signals, and for impressing these output signals upon the output node 42. The photodetector network 22 has a first photodetector 30 in optical alignment with the first input beam, and a second photodetector 32 in optical alignment with the second input beam. The inventive crossbar switch 10 further includes a multiplexer 26 for actuating the first and second photodetectors 30, 32 in response to a control signal. The invention also includes a laser diode circuit 24 for illuminating the first and second photodetectors 30, 32 in response to the control signal.

Abstract: A fiber optic fire and overheat sensor system 10 includes a fiber optic cable 12 having a lens 14 at a distal to direct radiation from a fire 16 into the cable 12 and to a radiation detector 18 disposed at a proximal end of the cable 12. Detector 18 is coupled to a fire sensor 19. The detector 18 is sensitive to two wavelength bands including a short wavelength band of approximately 0.8 to approximately 1.1 microns and a long-wavelength band of approximately 1.8 to approximately 2.1 microns. A controller 21, such as a microprocessor, analyzes the fire sensor 19 output signals which correspond to the two spectral bands to determine if a fire is present. The system 10 further includes a body of fluorescent material 20 disposed at the distal end of the cable 12. The material 20 can be interposed between a reflecting surface, such as a mirror 22, and a lens, such as a collimating lens 24. A fiber optic coupler 26 and 26a launches radiation from a source 28, such as a laser diode, into the fiber optic cable 12.

Abstract: A fiber optic fire detection and temperature measurement system 10 includes a fiber optic cable 12 having a lens 14 at a distal to direct radiation from a fire 16 into the cable 12 and to radiation detector 18 disposed at a proximal end of the cable 12. Detector 18 is coupled to a fire sensor 20. Detector 18 is sensitive to three wavelength bands including a short wavelength band of approximately 0.8 to 1.1 microns, a mid-wavelength band of approximately 1.3 to 1.5 microns and a long-wavelength band of approximately 1.8 to 2.1 microns. A controller 22, analyzes the fire sensor 20 output signals which correspond to the two spectral bands to determine if a fire is present. The fiber optic conductor is doped with a material selected for its temperature dependent fluorescent emission characteristics. Radiation from a fire passes via cable 12 to the detector 18. A pulse of radiation from source 28 passes from a coupler 26 and 26a to the cable 12.

Abstract: A fiber optic fire detection and temperature measurement system 10 includes a fiber optic cable 12 having a lens 14 at a distal to direct radiation from a fire 16 into the cable 12 and to a radiation detector 18 disposed at a proximal end of the cable 12. Detector 18 is coupled to a fire sensor 20. The detector 18 is sensitive to three wavelength bands including a short wavelength band of approximately 0.8 to 1.1 microns and a long-wavelength band of approximately 1.8 to 2.1 microns. A controller 22, analyzes the fire sensor 20 output signals which correspond to the two spectral bands to determine if a fire is present. The fiber optic conductor of cable 12 includes an optical filter 32 having a temperature dependent radiation transmission characteristic. Radiation from a fire passes via cable 12 to the detector 18.

Abstract: An optoelectronic crossbar switch 50 for selectively connecting signals on a plurality of optical fiber channels 52 to a given number of output receivers 30-36. Each optical fiber channel is split into a different number of optical fibers 56(a-h) which are arranged into an array having a plurality of rows and columns. Each row contains a fiber from each channel. A current summation network 58 is provided for each row and advantageously employs a plurality of selectively activatable detectors 60-74. The detectors are held in their open circuit state via a CMOS multiplexer 80 so as to minimize crosstalk between addressed and nonaddressed detectors. The switch 50 construction also minimizes the number of required components.

Abstract: A fiber optic buffer defect detection system including a laser, for illuminating the fiber buffer with a collimated beam of light energy, and detectors for detecting any scattering of the beam, from a defect in the fiber buffer. The detectors are mounted to collect scattering out of a radial plane defined by the angular rotation of the beam about the fiber at the point of intersection of the beam with the fiber buffer.

Abstract: The Invention provides a locally distributed crossbar switch to optically connect many computer processors and memories in arbitrary permutation an without interruption. A process or and an associated memory can be packaged together, taking advantage of the fact that the distributed crossbar switch employs local switching. At the same time, processor-memory pairs can be physically separated from other such processor-memory pairs, and by great distance.

Abstract: Fine single crystals of low-melting point materials are prepared by slowly withdrawing a glass crystal growth capillary tube containing the material from a heating apparatus which precisely maintains the molten material at a temperature just above its melting point. Temperature control of the molten material in the crystal growth tube, prior to solidification, is attained by enclosing the crystal growth tube in a temperature control tube containing the molten material being solidified. Preferably, the inside diameter of the temperature control tube is slightly larger than the outside diameter of the crystal growth tube, and both tubes reach into a reservoir of the molten material to be grown as a crystal, so that the molten material is drawn upwardly into the crystal growth tube and the space between the crystal growth tube and the temperature control tube by capillary action.

Abstract: An interferometric sensor (10) employs a sensing optical fiber (12) and a reference optical fiber (14). The sensing fiber (12) has a coating 16 thereon responsive to radiated thermal energy while the reference fiber is shielded therefrom. Both the sensing and reference fibers are subjected to the same ambient environment so that both fibers are subjected to heating by convection or conduction in essentially the same amounts. As a result, the sensor (10) is substantially nonresponsive to convected or conducted thermal energy while being highly responsive to radiated energy, particularly in the 6-30 micron wavelength region.

Abstract: A method of forming a tapered optical waveguide within a substrate (2). An appropriate substrate (2) is coated with a layer of barrier material (4) such as silicon dioxide which provides a relatively tight matrix relative to the open matrix of the substrate (2). The barrier material (4) is deposited on the substrate with a sloping variable thickness that is inversely related to the desired depth of the waveguide taper. The barrier material (4) can be deposited through a vacuum deposition technique and subsequently subjected to ion-milling to provide the desired taper. An appropriate source of metal ions (6), such as silver, capable of being transferred, such as by diffusion into the substrate (2) for increasing the refractive index and thereby defining a waveguide, is then transmitted to and through the barrier material (4).

Abstract: A spectral filter for an integrated optic application, such as in an optical demultiplexer (14), is provided and includes a common input waveguide (20) integrally connected to a pair of optical output waveguides (22, 24). The material selected for the output waveguides (22, 24) can be semiconductor material that provides a low index of refraction for a specific wavelength in one output waveguide and a relatively higher index of refraction for the same wavelengths in the other output waveguide, the output waveguide materials being interrelated in that they have a common index of refraction for at least one wavelength across the spectrum of radiation. An incident spectrum of radiation (16) can be split into at least a pair of bandwidths of radiation to provide a spectral filter function.