Showing papers on "Optical Carrier transmission rates published in 1985"

Optical transmission system

Abstract: In a coherent optical transmission system an input optical signal is amplified by being frequency down converted to an intermediate frequency, for example by means of a photodiode (1) and a reference optical local oscillator signal, and the photodiode output current is amplified in a GaAs FET wideband amplifier (6) and inserted on an optical carrier signal comprised by the reference signal by means, for example, of an integrated optical single sideband modulator (up converter) (7). By use of the same optical local oscillator to drive both the photodiode down converter and the integrated optic single sideband up converter, input/output coherence is ensured. The optical local oscillator may be comprised by a GaAlAs laser (3) stabilized to an "atomic" standard (4,5). Channel dropping/insertion may be carried out at the intermediate frequency, for example following the amplifier (6).

Passive optical star bus with collision detection for CSMA/CD-based local-area networks

Abstract: A prototype 16-terminal passive star bus suitable for carrier sense multiple access with collision detection (CSMA/CD)-based fiber-optic local-area network is described. Operation is at 16 Mbit/s over optical path lengths of 600 m. The optical wavelength is 830 nm. A novel and simple collision detection method based on listening onto the bus is incorporated within the system. In addition, data is scrambled instead of Manchester encoded. The effect that scrambling has on the collision detection method, as well as on the detection of both the bus idle state and the beginning and end of data packets is examined in detail. The network efficiency is calculated taking into account the operation of the scrambler as well as the collision detection method.

Optical fiber communication for local area networks with frequency-division-multiplexing

Abstract: A method and associated system for providing multi-channel transmission of digital and broadband video information in optical fiber communication for local area networks through frequency-division-multiplexing, comprising the steps of generating a plurality of closely spaced optical carrier wave pairs with the optical carrier waves within each optical carrier wave pair having a predetermined separation frequency between one another, assigning each of the plurality of optical carrier wave pairs to a predetermined frequency slot and optically combining the plurality of optical carrier wave pairs to provide a multiplexed optical output wave. Advantageously, in addition to direct detection the plurality of optical carrier wave pairs may be detected by opto-electronic heterodyne detection and/or incoherent optical-heterodyne detection to electronically recover the optical carrier wave pairs.

Optical switching mean.

Abstract: A node of an optical transmission network, for example a local area network, has a combined by-pass switch and optical modulator. The by-pass switch and modulator (45) comprises an optical switching matrix with two non-intersecting waveguides (W1, W2) connected by a further waveguide (W3). The junctions between the non-intersecting waveguides and the further waveguide perform both modulation of an optical carrier signal and re-routeing of the transmission path along the network.

System for relaying optical phase modulation wave

Abstract: PURPOSE:To attain relaying for transmission by applying phase modulation to an ultrahigh speed optical phase modulation optical wave by means of an optical carrier outputted from a ligh source whose frequency is superhighly stable, having high Q, single polarized wave and single mode, of the same characteristic as that for carrier phase-modulated at the transmission side and transmitting the result to an optical fiber transmission line. CONSTITUTION:An optical wave Somega transmitted from an optical fiber 1 is extracted by a Y circulator 8, led to a photodetector array 12 via a spatial coupling filer 11 having a transfer function Yomega=Somega of received light having a conjugate characteristic with the optical wave Somega, a Y circulator 9 and a lens 10, the demodulation is conducted in parallel processing, the signal is impressed to a waveguide 22 comprising an LD having a low Q which is adjusted to be on the verge of emission as an electric signal so as to irradiate a light having a center frequency of omega2, the light is superimposed on an optical fiber 5 as a phase modulation wave by an optical carrier having a center frequency omega1 outputted from an LD14 having a high Q, and the result is transmitted to an optical fiber 2 via the Y circulators 8, 9 . The optical wave from the LD13 having low Q and the LD14 having high Q and superimposed on the optical fiber 5 is phase- modulated on the optical fibers 5, 3 and 2, and the transmitted ultrahigh speed optical phase modulation optical wave is reproduced.

Development of a medium-/small-scale local area optical fiber loop network

Abstract: This report describes the outline of an optical loop network which is the most suitable for a system consisting of about 200 terminals. Upon development of an optical local-area network (LAN) to be used within this range, the compact, low cost, and general purpose properties, as well as the reliability and expandability of the system should be considered first. Especially, determination of the transmission rate and selection of the microprocessor to be used are important items to realize the compact and low cost network as desired. There are two examples for such systems which are used actually now. One is the HLN-8140 Loop, which is suitable for small-sized systems. It is a packet switching loop network using the token-passing method with a transmission rate of 1 Mbit/s. Another example is the HLN-8380 Loop which can cover up to medium-sized systems. It is a circuit-switching loop network with a transmission rate of 10 Mbit/s, and it allows transparent communications to be made via telephones and facsimiles.

Digital signal multiplexing unit

Abstract: Digital signal multiplexing unit in which twelve digital signals with a bit rate of 44.736 Mbit/s are combined in a multiplexer (1) using time division multiplexing. The frame is formed from four sub-frames in accordance with CCITT Recommendation G.922. A demultiplexer (2) is able once again to separate the twelve digital signals at a bit rate of 44.736 Mbit/s.

Optical communication network

Abstract: PURPOSE:To realize a high line utilizing rate and a short transfer delay by using a transmission control procedure which completes transmission sequentially from data of a transmission controller placed at the nearest position to an optical carrier source to avoid collision. CONSTITUTION:When a transmission controller, e.g., 220 inputs a transmission request of data from a computer 228, the data is stored in a storage section 221, and when a reception section 223 and a control reception section 224 receive only an optical carrier propagated from an optical carrier source, an optical switch 225 makes switching by using an electric signal to the optical carrier data from the optical carrier source 204 and an optical signal corresponding to the data is outputted to a transmission line. This optical signal is branched at reception couplers 236, 246, received by control reception sections 234, 244 to keep optical switches 235, 245 in the passing state. Thus, the optical signal passes through the switches 235, 245, is reflected at a reflecting point 201 and received by reception sections 243, 233, 223 and 213.