摘要:
Method and apparatus for causing light to interact with surface acoustic waves so that the light is either scattered out of or coupled into an optical wave guide. In the case of scattering when the light is propagating in an optical wave guide and chirped surface acoustic waves interact with the light, the light is scattered out of the optical wave guide into a focused beam. The focused beam of light travels in a path parallel to the surface acoustic waves and at the same velocity as the acoustic waves. The focused beam can scan objects to obtain electrical signals corresponding to the optical image of the objects and also the beam can be focused on a plurality of photodetectors to multiplex the light. In the case of coupling when the light is incident on an optical wave guide and the frequency of the chirped surface acoustic waves is selectively varied, the light is selectively coupled into the optical wave guide in a corresponding manner. The selective coupling of the light permits the frequency spectrum and the angular distribution of the light to be analyzed.
摘要:
A data distribution system has a number of data processing devices interconnected by data transmission media. At least one of the data processing devices transmit data to other data processing devices in the system. The transmitting data processing system includes memory for storing the data to be transmitted, programmable data processing circuitry, and data transmission apparatus for transmitting an encoded representation of the stored message as a sequence of data packets. Priority data, stored in the memory, represents a plurality of assigned priority levels for specified portions of the stored message such that portions of the stored message have respective assigned priority levels. A data encoding program generates an encoded representation of the stored message that includes, for each portion of the stored message, a level of redundant data corresponding to the priority level assigned to that portion of the stored message. As a result, the encoded representation of the stored message includes different levels of redundant data for the different portions of the stored message. Each receiving data processing system includes memory for storing received data, programmable data processing circuitry, and data receiving apparatus for receiving at least a portion of the transmitted data packets. A data decoding program generates a decoded representation of the received data stream. The data decoding program decodes different portions of the received encoded data in accordance with the different levels of redundant data included in the received data stream.
摘要:
An optical fiber point-to-multipoint communications network is disclosed of the type having a bus topology. The broadcasting terminal (101) of the network includes an information transmitting laser (102) and a local oscillator laser (103) the signals of which are launched onto opposite ends of an optical fiber bus (104) to counter-propagate thereon. At each of the M stations (105-1-105-M) connected to the bus, a wideband directional coupler (106-1-106-M) couples portions of each of the counter-propagating signals to a balanced coherent detector (107-1-107-M). The effective total power input to the balanced coherent detector at each of the stations is equal regardless of the location of the station relative to the broadcasting terminal. In another embodiment the stations are connected to ring-shaped optical subbuses which are coupled to the main bus. Several two-way point-to-multipoint embodiments are disclosed which employ wavelength division multiplexing techniques to enable communications from the stations back to the broadcasting terminal.
摘要:
In a digital, time division multiplex communication system, a first-in, first-out buffer (10) at each subscriber station is employed to establish a conference call. The digital words of the conferees being listened to are entered into the buffer as they are received. They are then read out at a different bit rate such that they all occupy an equal fraction of the word period. The words are decoded in a standard D/A converter (11) and combined in a filter (12).
摘要:
The efficiency of packet switching networks is improved by using a collision avoidance technique rather than collision detection. The subscriber links are connected to a common node. A collision avoidance circuit in each link monitors the node to determine whether it is in a busy or idle status. The first message to arrive places the node in a busy status at which time all other, nontransmitting links are disconnected, thereby avoiding a collision. Later arriving messages are stored in buffers at each subscriber location and are transmitted when the node is again idle. In this manner messages are transmitted on a first-come basis, and can be of arbitrary duration regardless of bit rate.
摘要:
An injection laser is automatically stabilized so that the laser operates above threshold when the laser current is modulated. The invention makes use of the fact that the laser junction voltage saturates at currents above the threshold. A signal which modulates the laser current and causes the laser current to fall below the threshold level therefore results in a change in the junction voltage. These changes in the junction voltage are monitored and used to increase the bias current so that the laser operates above threshold.
摘要:
The present invention relates to a method and apparatus for breaking optical fibers. The present method comprises the steps of: clamping an optical fiber at two spaced-apart peripheral areas on opposite sides of the area of intended break; heating the area of the intended break to at least the annealing temperature of the fiber; scoring the fiber along the line of intended break; and either bending and pulling or pulling the fiber apart to produce a break with a flat end surface. The heating step may also be advantageously employed to melt or evaporate a jacket surrounding the optical fiber adjacent to the area of intended break.
摘要:
An online conference session management system includes computer sites associated with a conference session holder, a plurality of service providers and a plurality of conference session participants. The conference session holder and each service provider has a respective associated public/private key pair for a specified online conference session. Each service provider is provided with an active participant registration certificate that gives the service provider the authority to register participants of the specified conference session, as well as authority to register other service providers as active participants of the specified conference session by providing those other service providers with respective active participant registration certificates. Each active participant registration certificate is digitally signed by either the conference session holder or one of the service providers using a private key of a public/private key pair unique to the conference session holder or respective service provider. Each active participant registration certificate includes the public key of the public/private key pair unique to the service provider whose authority to register participants is given by that active participant registration certificate. The service providers provide participants of the specified conference session with passive participant registration certificates. Each passive participant registration certificate is digitally signed by a service provider using a private key associated with that service provider. A passive participant registration certificate is validated by verifying the certificate's digital signature with the public key associated with the service provider that provided the passive participant registration certificate, and then validating that service provider's active participant registration certificate.
摘要:
A distributed star network for providing point-to-point and broadcast-type communication among a plurality of user stations is disclosed. The distributed star network is implemented using single mode optical technology including single mode lasers and single mode optical fibers.
摘要:
Apparatus is disclosed which stabilizes the temperature, and thereby the output wavelength, of an injection laser. Means (50 and 23) monitor the laser terminal voltage across a laser (11) and derive a voltage laser therefrom which is proportional to the junction voltage of the laser. Means (24) compares the voltage to a reference value from source (27) and a temperature controller (35) adjusts the laser temperature in response to the results of the comparison.Further embodiments of the present invention vary the output wavelength of the laser by varying the reference value from source (27) against which the laser junction voltage is compared.