Optical communications networks

Details Optical communications networks Optical communications networks

1996-11-26

1998-06-30

Negash, Kinfe-Michael

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

359119, 359168, 370424, H04J 1402

Patent

active

057742448

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to wavelength management in an optical communications network employing wavelength division multiplexing.
2. Related Art
The efficient use of wavelengths in a wavelength division multiplexed communication system has been addressed by others. For example, U.S. Pat. No. 5,319,485--Yasui et al uses a wavelength control unit to monitor communication paths and, in response to a connection request signal, to select an optical signal wavelength to be used from among currently unused wavelengths on the communication paths. Other prior art considered pertinent by the Examiner includes:
It is known from "A Precompetitive Consortium on Wide-Band All-Optical Networks", by S B Alexander et al., Journal of Lightwave Technology, Vol. 11, No. 5/6, May 1993, to configure an all-optical network (AON) as a hierarchical tree structure in which a plurality of level-0 AONs, having optical terminals and also known as passive optical networks (PONs), are connected to level-1 AONs which in turn are connected to level-2 AONs. Each PON has a fixed frequency-selective local bypass for wavelengths which are pre-allocated for use at level-0, thus enabling the same wavelengths to be used by each PON. To connect with a terminal on a different PON, a terminal must use a wavelength not in the level-0 set to reach its associated level-1 AON where the wavelength is routed either to a PON on that level-1 AON or upwards to an associated level-2 AON to reach a PON on a different level-1 AON. Frequency changers may be used in this latter case.
International Application No. PCT/US92/03251 (International Publication No. WO 92/18890) discloses an optical network of nodes and connecting links of pairs of fibres carrying optical signals in opposite directions. Each node comprises an optical switch in the form of a controllable linear divider-combiner (LDC) assembly which under the control of a Network Control Centre performs power dividing and combining for each of the wavebands from a waveband demultiplexer to route signals from an input port to an output port.
The articles "Linear Lightwave Networks: Performance Issues" by T E Stern et al., Journal of Lightwave Technology, Vol. 11, No. 5/6, May/June 1993, and "Linear Lightwave Networks: How Far Can They Go?", by T E Stern, Conference Record, IEEE Global Telecommunications Conference, 2-5 Dec. 1990, Vol 3, pages 1866-1872, also disclose optical nodes employing an LOC as an optical switch performing controllable waveband selective optical signal routing, combining, and splitting. The switch proper comprises controllable power dividers (also known as directional couplers) disposed so that each input port can be controllably connected to any output port. In preferred arrangements there are several switches, each having its input ports connected to the output of a common waveband demultiplexer and its output ports connected to a common waveband multiplexer. In this way, wavelengths in a waveband can be confined to limited regions of a large network, and the waveband can be reused in other parts of the network.
The article "The LAMBDANET Multiwavelength Network: Architecture, Applications, and Demonstrations", by M S Goodman, et al., IEEE Journal on Selected Areas in Communications, Vol. 8, No. 6, August 1990, discloses a plurality of nodes, each of which transmits on a respective wavelength, connected to a star coupler so that each node output is broadcast to each other node. In order to separate the received set of wavelengths a node may use wavelength tunable filters and receivers, or multiple fixed receivers.
The paper "Multiwavelength Ring Networks for Switch Consolidation and Interconnection", by S S Wagner et al., Conference Record, International Conference on Communications, 14-18 Jun. 1992, Vol. 3, pages 1173-1179, discloses a plurality of Central Offices (COs) connected by a 2-fibre multiwavelength-ring network. One CO acts as a switch, and each of the other COs sends transmissions to the switching CO on a respective

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Wagner et al, "Multiwavelength Ring Networks for Switch Consolidation and Interconnection", Conference Record, International Conference on Communications, 14-18 Jun. 1992, vol. 3, pp. 1173-1179, Chicago.
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Goodman et al, "The Lambdanet Multiwavelength Network: Architecture, Applications and Demonstrations", IEEE Journal on Selected Areas in Communication, vol. 8, No. 6, Aug. 1990, New York, pp. 995-1004.
Alexander et al. "A Precompetitive Consortium on Wide-Band All-Optical Networks", Journal of Lightwave Technology, vol. 11, No. 5/6, May 1993, New York, pp. 714-732.
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