Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1991-12-02
1993-06-15
Coles, Sr., Edward L.
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359139, 359126, H04B 1014, H04J 1408
Patent
active
052204480
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a bit and frame synchronization unit for an access node of optical transmission equipment.
2. Description of the Prior Art
Transmission equipment and diverse types of information transmission via transmission lines are known in general. Recently, optical transmission lines have become increasingly important for various reasons. In addition to the optical point-to-point connections, complicated network structures with optical lines are also known. For example, in an article entitled "Optical fibres in local area networks", Communications/Communications International, October 1985, pages 19 ff., B. Viklund describes various network structures with glass fiber cables for distribution networks and for networks with connections between diverse subscribers which can be set up individually. In the latter, a ring structure is most favorable. The subscriber stations of an optical transmission line of the aforementioned type are connected to the respective utilized fibers via optoelectrical couplers.
At present, there are components for optical systems, e.g. couplers, switches and modulators, based e.g. on InP semiconductor material, which utilize electro-optical effects in order to influence light. These elements work up to frequencies in the gigahertz range.
The use of address-coded packets for the transmission of information is generally known. Such packets comprise a header and an information part [hereinafter, infopart], wherein the header contains all necessary data for the respective packet and the participating devices, e.g. a destination or target address, data concerning the type of packet, monitoring bits, etc. The infopart is available for the useful information to be transmitted.
When receiving information arriving via an optical line, it is unavoidable that at least a part of the light stream carrying the information is used. Further, every receiving subscriber station must be synchronized to the bit clock and to the clock of the passing packet.
SUMMARY OF THE INVENTION
The object of the invention consists in providing transmission equipment which makes do to a great extent without electrical regenerators while utilizing the aforementioned components. In particular, a bit and frame synchronization unit is to be provided which is simple in construction and operates in an uncomplicated manner.
The solution, according to the invention, makes it possible to provide flexible transmission equipment which has considerable advantages over the comparable, previously known equipment because of its more extensive optical construction. An outstanding immunity to electromagnetic interference should be noted in particular. The synchronization unit works with an integrator which is slow compared to the bit clock and by nature has no problematical reactions to distortions and the like. The synchronization unit is accordingly suitable for rapid transmission lines up to clock frequencies of e.g. several gigabits. Moreover, it is advantageous that the synchronization to the bit clock and frame clock is effected mutually and simultaneously.
The invention is described in more detail in the following by way of example with reference to seven diagrams.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of optical transmission equipment;
FIG. 2 is a schematic view of an optical directional coupler on a very enlarged scale;
FIG. 3 is a symbolic depiction of the directional coupler;
FIG. 4 is a block wiring diagram of a first bit and frame synchronization unit;
FIG. 5 shows assigned functional dependency;
FIG. 6 is a block wiring diagram of a second bit and frame synchronization unit;
FIG. 7 shows the functional dependency of the second bit and frame synchronization unit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a schematic view of transmission equipment 10 on which information is transmitted in the direction of the arrow in the form of addressed packets. An optical fiber 11, particularly a monomode fiber, serves
REFERENCES:
patent: 4554673 (1985-11-01), Stevens
patent: 4777661 (1988-10-01), Spillman
patent: 5130836 (1992-07-01), Kahaku
Noel, "Faraday-Effect Fiber Optic Switch", IBM Tech Disclosure, vol. 26, #7B Dec. 1983 pp. 3744-3745.
Viklund, "Optical Fibers in LAN's", Communications International, Oct. 1985, pp. 19-21 and 24.
Martinson Thomas
Vogel Paul
ASCOM Tech AG
Coles Sr. Edward L.
Pascal Leslie
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