Abstract: A reference frequency distribution system for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and remote unit in phase. A fiber optic cable connects the reference unit to the remote unit. A frequency source at the reference unit produces a reference frequency having an adjustable phase. A fiber optic transmitter at the reference unit modulates a light beam with the reference frequency and transmits the light beam into the fiber optic cable. A 50/50 reflector at the remote unit reflects a first portion of the light beam from the reference unit back into the fiber optic cable to the reference unit. A first fiber optic receiver disposed at the remote unit receives a second portion of the light beam and demodulates the reference frequency therefrom to be used at the remote unit.

Abstract: A unipolar original electrical signal is encoded by alternate mark inversion and combined with a DC bias current for injection of a semiconductor laser to produce a bipolar FSK optical signal that is transmitted to a receiver. At the receiver, the received signal is coupled with optical local power and fed to an optical/electrical transducer, preferably a semiconductor, to produce an electrical signal that is demodulated to produce the original unipolar signal. The demodulator may be of different types, for example employing delaying part of the amplified electrical signal and mixing the delayed part with the original signal for passage of the combined signal through a low pass filter; with proper selection of the delay, an AMI decoder is not needed. The demodulator may also be of the type that has one or more band pass filters to respectively separate the positive mark, space and negative mark signals that may thereafter be added.

Abstract: This invention relates to mechanisms for steering or pointing transmitted optical radiation beams and/or the look directions from which optical radiation beams are received. It also relates to optical communications systems incorporating such mechanisms, more particularly but not exclusively interspacecraft communications systems.

Abstract: A crossover network implemented using two-dimensional arrays of nodes. The network is a perfect shuffle equivalent network because it is topologically equivalent to a crossover network of one-dimensional arrays of nodes. The two-dimensional arrays are arranged in rows and columns and there are a plurality of link stages interconnecting successive arrays. The network is implemented efficiently in free space optics because the network topology requires optical crossovers in some link stages that interconnect only nodes in the same column of successive arrays and optical crossovers in the other link stages that interconnect only nodes in the same row of successive arrays.

Abstract: Two intermediate frequency signals, which are used in a polarization diversity optical heterodyne receiver operable according to demodulation and subsequent combination and have a common intermediate signal frequency variable in an intermediate frequency range, are subjected to delaying relative to each other and then combined into a combined intermediate frequency signal. A frequency discriminator (24) discriminates the intermediate signal frequency of the combined intermediate frequency signal to produce a control signal for use in stabilizing a local optical frequency of a local beam used in combination with a signal beam susceptible to polarization fluctuation. A delay may be given for the delaying to one of the two intermediate frequency signals alone. Alternatively, a delay may be given for the delaying to only one of two local beam components which are coupled to two signal beam components for use in producing the two intermediate frequency signals.

Abstract: A bus receiver communicates with a bus head end transmitter via a communication path different from read and write optical fibers used by a plurality of remote terminals on the bus so that the bus receiver can quickly determine beginning and end of time slots, clock frequency, and signal trigger levels using a minimum amount of bits attached to a front end of each packet in each time slot.

Abstract: A fiber optic multiplexing controller for transmitting a separate original electrical signal to each of a plurality of signal receiving devices. Each separate original electrical signal originates from one or a plurality of signal sending units. A transmit section of the controller includes an encoder for encoding the separate original electrical signals into a single multiplexed electrical signal. The transmit section further includes a fiber optic transmitter for converting the multiplexed electrical signal to an optical signal. Thereafter, the optical signal is transmitted via fiber optics to a receive section of another identical controller. This receive section includes an optical receiver, provided for the purpose of receiving the transmitted optical signal and converting it to a multiplexed electrical signal. The multiplexed signal, whether electrical or optical, is made up of discrete portions. Each portion of the signal is devoted to a predetermined one of the separate original electrical signals.

Abstract: An optical transceiver module is disclosed, particularly for connection to a bidirectional optical-waveguide communications network. It contains an optical transmitter (S), an optical receiver (E), and wavelength-selective means (K, C) which prevent any optical feedback to the optical transmitter (S) and the optical receiver (E) and guide the light to be received exclusively to the optical receiver (E). Such means are, for example, wave-length-selective couplers (C, K) implemented as fiber-optic couplers or as one or more integrated optical devices.

Abstract: There is provided by this invention an optical heterodyning device comprised of a semiconductor heterostructure having a forward biased electrode connected thereto for optically mixing an input signal frequency with a local oscillating frequency in the separate confined laser cavity and a reverse biase electrode connected thereto for detecting the intermediate frequency produced. The local oscillator provides preamplification in the laser cavity and can be effectively phase locked to the input signal frequency.

Abstract: An optical data link for transferring data between a pair of connectors and for activating an electrical device to which one of the connectors is attached. A light-emitting diode (LED) and a phototransistor are mounted in each of the connectors, with the LED of each connector visible to the phototransistor of the other connector when the connectors engage each other. The LEDs and phototransistors are connected to respective interface circuits. The interface circuits for at least one of the LEDs limits the current through the LED regardless of the amplitude of a driving signal. The interface circuits for the phototransistors maintain a relatively constant voltage across the phototransistors so that the phototransistors function as current switches. The electrical device is activated in response to closure of a magnetically sensitive reed switch mounted in the connector attached to the electrical device.

Abstract: The present invention relates to a technique for suppressing intermodulation products introduced by nonlinearities of a laser in a multicarrier Freqeuncy Division Multiplexed (FDM) fiberoptic link. More particularly, for two or more closely spaced FDM channel information signals within a predetermined band of frequencies in an FDM optical transmission system, third-order intermodulation products, which are produced by nonlinearities of a transmitting laser, also fall in-band and provide interference in the channel information signals.

Abstract: A polarization diversity light receiving system using base combining is disclosed, which is arranged so that the control signal for the local oscillator laser is the sum of squared values of received signals.

Abstract: Method and apparatus for making phase stable measurements of charateristics of microwave antennas and other devices utilizing an optical transmission path as a phase stable reference in order to identify phase errors along a radio frequency transmission path induced by flexing of a radio frequency transmitting cable as the antenna probe or antenna under test is moved in the course of testing. Similar apparatus and techniques are described for use with a harmonic mixer to gather receiver data which is free of phase errors caused by movement of the antenna.

Abstract: A method and apparatus for transmitting data between two transmission-receiving units with infrared signals wherein one of the two transmitting receiving units does not have its own power supply and is to be supplied with energy by light received with photocells. When the data receiver and energy receiver are in close proximity, blooming of the data can occur and, thus, faulty data transmission results. In the invention, the data and energy are intermittently and alternately transmitted such that during the energy transmission the data transmitter of the first transmitting receiving unit sends out auxiliary synchronization pulses and after predetermined time both the energy transmission as well as the auxiliary transmission pulses are simultaneously shutoff. The trailing edges of both pulses can be unambiguously recognized even during blooming and are used as a synchronization signal which causes the second transmitting receiving unit to start sending data.

Abstract: An image information transmitting apparatus comprises an image output unit for outputting image information, a modulation unit for pulse-frequency modulating the image information from the image output unit and a demodulation unit for demodulating the modulated signal from the modulation unit to form the image information. The demodulation unit discriminates a signal content by a time interval from a rise to a fall or vice versa of the input modulated signal.

Abstract: An electro-optical coherent light beam signal transmission system capable of transmitting signals occupying a wide bandwidth collimated beam for a substantial distance. The system has a coherent light generator modulated at a wide bandwidth and a reflecting mirror system that radiates the modulated coherent light generated in a selected direction and spreads the said coherent light into a collimated beam having a safe energy level distribution. A coherent light receiving module in alignment with the radiated coherent light beam decollimates and focusses the coherent beam on a light sensor. Subsequently the communications signal is distributed to end users through cable systems. The coherent light generator is preferably a semiconductor coherent light generating diode and includes a temperature monitoring and regulating system which maintains coherent light generator at an optimum operating temperature for peak output levels.

Abstract: A power supply circuit, which steps down an input voltage, is provided in an optical repeater for an optical communications path. A DC current supplied from a regulated current supply through a conductor is increased by the power supply circuit before being provided to the amplifier circuit of the optical repeater, so that power consumption is reduced.

Abstract: A switch for receiving packets on optical fiber input trunks and for switching the packets to appropriate optical fiber output trunks is disclosed. The packet switch is a hybrid switch comprising both optical and electronic devices and specifically comprises and electronic input buffer, an optical transport network and an optical control network. The optical transport network prevents internal collisions within the switch and the optical control network prevents external collisions of packets. The packet switch exploits the inherent properties of optical and electronic devices for the specific functions they are best suited for.

Abstract: The present invention relates to an optical backplane for use in a switching system or computer for interconnecting a plurality of associated circuit modules. The backplane comprises a switch which is interconnected to each of the associated circuit modules by a separate multifiber ribbon, each ribbon including (1) a plurality of transmit and receive optical fibers, and (2) an optical fiber for providing concurrent synchronization signals to each of the associated circuit modules. The switch includes a switching block for coupling parallel optical signals received from the plurality of receive optical fibers in any multifiber ribbon, transmitted by a sending module, to the transmit fibers of each of the multifiber ribbons for transmission to all of the modules associated with the optical backplane.

Abstract: Apparatus for transmitting meter data in serial form by IR emissions to a remote, hand-held communicator having a front-end detector circuit including a photodiode responding to the meter data and dissipating a d.c. term occasioned by indirect ambient illumination of the photodiode in the IR region. Corresponding control communication from the communicator to the meter is provided by IR emissions directed from an emitter of narrow beam angle to a wider angle receiving photodiode mounted with the meter at a location shielding it from direct sun illumination emanating above a horizontal plane extending from the immediate region of the photoresponsive receiver. Higher data transmission rates of 19.2 Kbaud are available in conjunction with an FSK transmission approach employing two channels.