Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-11-24
2002-04-02
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06366373
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to methods of routing carrier wavelengths through a fiber optic communications network, and more particularly to a method wherein management data is continuously transmitted by subband quadrature coding along with application data on an optical wavelength carrier signal for routing a carrier wavelength through an optical communications network.
2. Brief Description of the Prior Art
Optical communications systems service an important and expanding portion of current needs. The wide bandwidth provided by lightwave carrier signals allows the transmission of larger quantities of data to be sent in a given time frame than in systems using carriers at lower frequencies. Reliable and economical methods are required for directing/routing the optical signals from a source to a desired destination.
FIG. 1
is a simplified diagram of a network
10
for illustrating an example of the routing of signals through a network. Fiber optic cables
12
-
18
interconnect four nodes or hubs
20
-
26
providing access to the network
10
. A symbol such as item
27
is used to indicate that a line is a fiber optic cable, and will be used for that purpose in the various figures of the drawing. Each node in
FIG. 1
includes circuitry for inputting data at
28
and outputting data at
30
, the circuitry having a laser source, a controller, and an add/drop module for receiving/dropping and sending/adding a signal from and to the network
10
.
The signals transmitted include user application data, and must also contain or be accompanied by a signal with management data identifying the required destination. Each node must have the capability of reading the management data and receiving data that is intended for that node. One prior art method of transmitting management data is illustrated in
FIG. 2
wherein a block of management data, noted as a tag
32
, is transmitted to identify a required destination. Each node reads the management data, and responds by receiving user data
34
intended for that destination, and causes user data for other destinations to continue around the network
10
. A signal is simply transmitted around the ring until it reaches the required destination. Another type of network element is illustrated in
FIG. 3
wherein a hub or router
36
evaluates management data, for example from an incoming signal on line
38
, and responds by transmitting the signal on the appropriate one of lines
40
,
42
or
44
.
A disadvantage of the use of a tag
32
or header is that, because it occupies only a finite time frame, it can be lost or misread as a result of system noise. Use of a “header” is described for example in U.S. Pat. No. 5,438,444 by Tayonaka (column 3, lines 20-43; and column 10, lines 26-34). The technique of using a header to determine a destination is also described in
ATM Networks, Principles and Use
, by Martin P. Clark, page 13 (a Wiley Teubner publication). Another disadvantage of using a “tag” or header to carry management data is that it consumes system bandwidth that could otherwise be used for application data. For example, in ATM cells, a cell length is 53 bytes of which 5 are used for a tag to carry management data, as illustrated in FIG.
2
.
Another method that is used to transmit management data is illustrated in FIG.
4
. Two laser sources
46
and
48
at different wavelengths are used. Source
1
carries the application data, and source
2
carries the management data. The data input/modulation of the two sources is managed by a controller
50
. The two source outputs at
52
and
54
are fed through a multiplexer
56
to place them on a single optic fiber
58
. The disadvantage of this method is the cost and complexity of the additional management channel.
SUMMARY
It is therefore an object of the present invention to provide an improved method of transmitting network management data through an optical communications network.
It is another object of the present invention to provide a low cost and reliable method of transmitting management data in an optical communications network.
Briefly, a preferred embodiment of the present invention includes a method of transmitting network management data through an optical communications network for routing of discrete wavelengths through the network by controlling switching at the nodes, wherein the management data is impressed on an optical carrier of a particular wavelength through use of a method known as subband quadrature coding (SQC). The optical carrier is modulated at a first frequency, and at a first intensity to impress application data on the carrier. The carrier is additionally modulated at a second frequency, preferably two orders of magnitude less than the first frequency, and at a second intensity less than the first intensity to impress management data on the carrier for routing the carrier through an optical communications network, from a source to a destination. According to the method, the management data is continuously impressed upon the carrier during transmission of the application data. The optical carrier is multiplexed onto the fiber optic communications line, and upon reaching a first node, the carrier is demultiplexed and an intensity sample of the carrier is detected. The management data is then separated out with a low pass filter, whereupon in response the method directs the carrier signal according to the management data.
REFERENCES:
patent: 5416626 (1995-05-01), Taylor
patent: 5438444 (1995-08-01), Tayonaka et al.
patent: 5712932 (1998-01-01), Alexander et al.
patent: 5920412 (1999-07-01), Chang
patent: 5936754 (1999-08-01), Ariyavisitakul et al.
patent: 5956165 (1999-09-01), Fee et al.
patent: 5959749 (1999-09-01), Danagher et al.
patent: RE36715 (2000-05-01), Taylor
patent: 6101012 (2000-08-01), Danagher et al.
patent: 6108113 (2000-08-01), Fee
patent: 6154484 (2000-11-01), Lee et al.
Clark, Martin P.: “The Technique of Cell Relay,” ATM Networks Principles and Use, published by Wiley Teubner Communications, p. 13.
Gaudino, R., et al.; “Remote Provisioning of a Reconfigurable WDM Multichannel Add/Drop Multiplexer,” IEEE Photonics Technology Letters, vol. II, No. 8, Aug. 1999, pp. 1060-1062.
MacKinnon Neil
Zipin Lee Joseph
Jaffer David H.
LuxN, Inc.
Pascal Leslie
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