AU2004201372A1 - Optical communication system that transmits and receives data through free space - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: Actual Inventors: Address for Service: Terabeam Corporation Charles Gregory AMADON Alexander Douglas CRONIN Cameron S ELLIOTT Richard D RALLISON James Charles STEVENS Karel ZIKAN John SCHUSTER Mark PRATT DAVIES COLLISON CAVE, Patent Attorneys, 1 Nicholson Street, Melbourne, 3000 Invention Title: Optical communication system that transmits and receives data through free space The following statement is a full description of this invention, including the best method of performing it known to us.

Q:\OPER\ARL\JAN-JIUN 2004\MARC-\12430C'60 85.DOC 29/3/04 P:OPER\AR1i2430060 div.doc-26/03/04 la- One aspect of the present invention provides a method for transmitting data between a central point and at least one user, the method comprising: at the central point, modulating data and at least one user address on a light beam; at the central point, transmitting the light beam through free space; demodulating the light beam and retrieving the data and the at least one user address; routing the data to the user according to the user address; and transmitting data from the user to a central point.

Another aspect of the present invention provides a communication system, comprising: a central node configured to transmit through free space an information signal modulated on a diverging coherent light beam; and a user node configured to received from free space the diverging coherent light beam and automatically process the modulated informational signal, wherein the diverging coherent light beam, as received at the user node, has different dimensions diverging coherent light beam at the central node.

A further aspect of the present invention provides an apparatus configured to transmit an optical carrier through free space to a plurality of user nodes, comprising: an input port configured to receive an information signal; a radiant energy generator configured to generate an optical carrier; a signal processor, coupled to the radiant energy generator and the input port, configured to process and combine the optical carrier with the information signal; and an antenna, coupled to the signal processor, configured to produce a shaped and diverging radiant energy and to transmit the combined optical carrier and information signal on the shaped and diverging radiant energy into free space.

Another aspect of the present invention provides a method for transmitting data, comprising: combining several data channels into a data stream; modulating the data stream on at least one diverging light beam; transmitting the diverging light beam through free space; demodulating the diverging light beam and retrieving the data stream; and P:\OPER\ArlI\12430060 div.doc.26/03/04 lbseparating the several channels of data from the data stream.

A further aspect of the present invention provides an apparatus for receiving an information signal, comprising: an antenna configured to receive from free space an optical carrier having an information signal modulated on a shaped and diverging coherent light beam; a signal processor, coupled to the antenna, configured to process and demodulate the shaped and diverging coherent light beam to separate the information signal from the optical carrier; and an output port, coupled to the signal processor, configured to send the information signal to at least one device.

Another aspect of the present invention provides a method of transmitting and receiving data, comprising: receiving encoded data and a multicasting session identifier, the multicasting session identifier indicating a group of recipient user points selected from among a plurality of user nodes configured to receive the encoded data; transmitting the encoded data and a multicasting session identifier on a shaped and diverging light beam via free space to the plurality of user nodes; receiving the shaped and diverging light beam from free space; and decoding the encoded data.

A further aspect of the present invention provides a data communication system, comprising: a transmitter configured to transmit an informational signal through free space modulated on a shaped and diverging coherent light beam, wherein the coherent light beam is sufficiently divergent to be received by a plurality of spatially separated receivers; and a set of receivers, selected from among the plurality of receivers, configured to receive the shaped and diverging coherent light beam from free space and decode the modulated informational signal.

Another aspect of the present invention provides a method for free space optical data communication, comprising: receiving at an antenna, a shaped and diverging coherent light beam transmitted through free space, wherein the light beam has an information signal modulated thereon, P:OPER\Mri\I 2430060 divdoc-26/03/04 Ic and wherein a cross-sectional area of the received diverging coherent light beam as received at the antenna is substantially greater than an area of the antenna; and demodulating and recovering the information signal from the shaped and diverging coherent light beam.

A further aspect of the present invention provides a data communication system, comprising: a transmission node having at least on radiant energy generator that generates information bearing radiant energy beams over several sectors; wherein each subsector comprises a channel; and wherein each channel operates at substantially the same wavelength.

Another aspect of the present invention provides a method of transmitting data comprising: modulating at least one information signal on at least one carrier; and substantially simultaneously transmitting the modulated information signal along a plurality of vertically differentiated sectors.

A further aspect of the present invention provides a communication system, comprising: a central node configured to split an input signal into a plurality of substantially similar output signals; a plurality of transmitters disposed in the central node to transmit the plurality of output signals to a user node as light signals; and a plurality of receivers disposed in the central node to receive a plurality of user signals from the user node.

Another aspect of the present invention provides an apparatus comprising: an amplifier having an input port to receive an input signal and operable to divide the input signal into a plurality of output signals; a plurality of transmitters to transmit the plurality of output signals, and a plurality of receivers associated with respective plurality of transmitters to receive user signals.

A further aspect of the present invention provides a method of transmitting and receiving, the method comprising: P:\OPER\Ar,\12430060 div.doc-26/03/04 Iddividing an input signal into a plurality of output signals; transmitting the plurality of output signals to a plurality of corresponding receivers of a user node; and receiving a plurality of user signals transmitted from the user node light signals.

BRIEF DESCRIPTION OF THE DRAWINGS Figure IA is a block diagram of a communication system.

Figure 113B is an isometric view showing a side of the communication system of Figure IA.

Figure 2 is a block diagram of an illustrative central network components for downlink transmission using the communication system in Figure IB.

Figure 2A is a flow diagram of an illustrative central system controller transmit function.

Figure 3 is a block diagram of illustrative user network downlink reception components.

Figure 3A is a flow diagram of an illustrative user system controller transmit function.

Figure 3B is a flow diagram of an illustrative user system controller receive function.

Figure 4 is a block diagram of illustrative central downlink signal processor components.

Figure 5 is a block diagram of illustrative user downlink signal processor components.

Figure 6 is a flow diagram of an illustrative downlink data transmission and reception process.

Figure 7 is a block diagram of illustrative user network uplink transmission components.

Figure 8 is a block diagram of illustrative central network uplink reception components.

Figure 9 is a block diagram of illustrative user uplink signal processor components.

Figure 10 is a block diagram of illustrative central network uplink components.

Figure 1 1 is a flow diagram of an uplink data transmission and reception process.

Figure 12 illustrates a data packct suitable for use with the communication system of Figure 1A.

Figure 13 illustrates an illustrative transmission point with sectorization.

Figure 14 illustrates examples of various suitable radiation patterns generated by the central transmit antennas in the illustrative central network components of Figure 2.

Figure 15 illustrates an illustrative topography produced by the sectorization of Figure 13.

Figure 16 is a flowchart illustrating an illustrative multicast process.

Figure 17 shows an illustrative central input/output interface.

Figure 18 is a block diagram showing an alternative embodiment of the communication system of Figures IA and 1B.

In the figures. like reference numbers refer to similar elements. In addition, the most significant digit in a reference number refers to a figure in which that element is first introduced an element 204 is first introduced in Figure 2).

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS A communication system. and in particular, a system and method for optical communications in free space is described herein. In the following description, numerous specific details, such as specific symbols and relationships. specific methods of and structures for transmitting, receiving, and processing high speed data. etc.. are set forth to provide a full understanding of the invention. One skilled in the relevant art. however, will readily recognize that the invention can be practiced without one or more of the specific details, or with other methods and structures, etc. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the description of the embodiments.

The detailed description is directed to systems, methods, and interconnected devices Ior networked, high-speed, bi-directional data communication through free space having one or more centrally located transmit/receive stations which use one or more lasers modulated with encrypted.

high-speed (10 Mbps-10 Gbps) data and control signals to illuminate with laser light some or all of the areas surrounding the centrally located transmit/receive stations. The illuminated areas surrounding the centrally located transmit/receive stations encompass one or more user optical receivers having light gathering and filtering elements, active tracking devices, optical detectors. and demultiplexing and decoding circuitry, which receive and select portions of the centrally located transmit/receive stations laser high-speed data stream for output to a user optical transceiver interface output. which is in turn may be connected via a high-speed networking connection to user equipment.

Data coming from user equipment on a 100 Mbps megabit Ethernet goes to the user optical transceiver interface input and modulates a laser collocated in the user optical transceiver. The user optical transceiver sends a collimated laser beam through free space back to the centrally located transmit/receive stations, where the collimated laser beam is received by light gathering and filtering elements, and active and actively tracking matrix detectors. where the data is detected and directed into data routinge circuits. The data routing circuits route the data to node addresses, which can be either within one centrally located transmit/receive station area or within other centrally located transmit/receive station areas, via a high-speed free space optical backbone network-to-network links or anywhere on other networks connected to the centrally located transmit/receive stations(s) routing circuitry.

The centrally located transmit/receive stations routing circuitry also routes incoming data addressed to any or all user optical transceiver(s) by encoding that data into the high-speed data stream of the particular centrally located transmit/receive station laser being detected by the respective user optical transceiver. The laser beams illuminate the area surrounding the centrally located transmit/receive stations in a variety of radiation patterns. The radiation patterns are sectored horizontally (or radially) and/or vertically (or by elevation).

The sectors may be further subdivided into several wavelength channels. The networks transmit and receive data using the channels.

The Communication System Figure lA is a block diagram of a communication system 100. The communication system 100 can be thought of as a hierarchic system with a set of interconnected networks, where each network is a node in the communication system 100, and where each network is interconnected. For example, the communication system 100 can include as nodes one or more central networks 102. user networks 104, and/or peripheral networks 105.

Data is exchanged among the networks. The data may be sent from the central networks 102 to the user networks 104 using shaped and diverging coherent light beams (or light cones) 106, and data is sent from the user networks 104 to the central networks 102 using collimated light beams 108. Each individual network also can include a hierarchy of interrelated subsystems with lower level nodes (or network elements),. which is described more fully below. Data is exchanged among the networks point-topoint, point-to-multipoint, multipoint-to-point, or multipoint-to-multipoint. andpoint-to-multipoint communication can be broadcast. multicast, or simulcast.

For example, during point-to-point communication, any one of the central networks 102 or their lower level nodes can transmit data from itself to any one node in the user networks 104 or the peripheral networks 105. Likewise, any of the central networks 102 or their lower level nodes can receive data from any one of the user networks 104 or their lower level nodes, as well as from any on.e of the peripheral networks 105 or their lower level nodes.

During point-to-multipoint communication, any one of the central networks 102 or their lower level nodes can transmit data from itself to several user networks 104 or their lower level nodes substantially simultaneously. Any one of the central networks 102 or their lower level nodes can transmit data from itself to several peripheral networks 105 or their lower level nodes substantially simultaneously. Likewise. any of the central networks 102 or their lower level nodes can receive data from any of the user networks 104 or their lower level nodes substantially simultaneously, as well as from any of the peripheral networks 105 or their lower level nodes substantially simultaneously.

The hierarchy of the communication system 100 can feature networks interconnected with each other, as Figure IA illustrates, which do not require that 1 the peripheral networks 105 and the user networks 104 be interconnected, or that the central networks 102 be connected to both the peripheral networks 105 and the user networks 104. Moreover, the central networks 102 may be interconnected to each other such that data is transmitted among the individual central networks 102 without passing through a.

peripheral network 105 or a user network 104. This particular example reduces the costs of operation. for example, by allowing central networks to carry their own backbone traffic, unlike other wireless networks that dedicate all of their bandwidth to the user networks.

In one case, a user network 104 is operated by a user that subscribes with the peripheral networks 105 and/or the central networks 102 to send and receive data in a client-server environment. The users may be located at a manufacturing facility, a multinational corporation, a financial institution, or a university, for example, with buildings that house the network components. In that instance, the central networks 102, the user networks 104, and the peripheral networks 105 connect "client" systems with "server' systems so that the server systems may perform a computation, retrieve a file, or search a database for a particular entry in response to a request by the client system. A particular type of client-server environment is not essential. It will be apparent to those skilled in the art that the implementation in other client-server environments is possible, such as airline flight reservations systems, mail-order facilities. etc.

The peripheral networks 105 can be tiny interconnected network operated by a common carrier, including a Public Switched Telephone Network (PSTN), a Local "Exchange Carrier. (LEC) network providing local telecommunication services. an Interexchange Carrier (IXC) providing long distance telecommunication services, a satellite network, a value added network providing dial-up stock market quoting services, electronic mail services, etc.). Alternatively, the peripheral networks 105 can be a collection of networks functioning as a virtual network, including the Internet, the World Wide Web, etc. The peripheral networks 105 also can include data communication networks such as Local Area Networks (LANs), Metropolitan Area Networks (MANs). or Wide Area Networks (WANs). Of course, those skilled in the art will appreciate that a particular type of peripheral network 105 in not required. Instead, any type of peripheral network 105 may be used.

In the central networks 102, the user networks 104, and the peripheral networks 105 utilize Synchronous Optical Network (SONET) technology, which is an optical interface standard that allows internetworking of transmission products from multiple vendors. That is, when the communication system 100 implements SONET technology, interconnection of the networks enables worldwide data communication. Moreover, when the communication system 100 implements SONET technology, a new digital hierarchy ideally suited to handling fiber-based signals and at the same time allowing easy extraction of lower rate signals is accomplished. These include unified operations and maintenance and the flexibility to allow for future service offerings.

In an alternative, the central networks 102, the user networks 104. and the peripheral networks 105 utilize Gigabit Ethernet technology, which is an optical interface standard that allows internetworking of transmission products from multiple vendors. That is. when the communication system 100 implements Gigabit Ethernet technology, interconnection of the networks enables worldwide data communication, especially real-time voice and video and high-end server support. Moreover, when the communication system 100 implements Gigabit Ethernet technology, a new digital hierarchy ideally suited to handling fiber-based signals and at the same time allowing easy extraction of lower rate signals is accomplished. These include unified operations and maintenance and the flexibility to allow for future service offerings.

Figure IB is an isometric view showing a side of the communication system 100. where data is exchanged between the central networks 102 and the user networks 104 in free space using the light cones 106a-c and the collimated light beams 108a-c. The light cones 106a-c are shaped and diverging coherent light beams, such as light amplification of stimulated emission of radiation, or "laser" beams. Laser beams are directional, and can operate in a range of wavelengths in the "'light" region of the e!ectromagnetic spectrum, including visible light, near-infrared light, and infrared light. When the light cones 106a-c are laser beams. the light cones 106a-c accommodate high bit rate, high power, high coupling efficiency, direct high frequency modulation, and long haul operations. The light cones 106a-c are eye-safe, class one laser beams, in accordance with American National Standards Institute (ANSI) standards. In alternative arrangements, the light cones 106a-c operate in accordance with other ANSI standards.

The use of particular wavelengths of laser light provides high bandwidth with very little attenuation (or power loss) in the atmosphere.

Moreover, using laser light allows interconnection with SONET architectures operating at high speeds between central networks 102 typical of off-the-shelf data transmission equipment currently available. Moreover, using the SONET protocol allows arbitrary bandwidth allocation in the wellknown portions of T-I capacity. That is. when the communication system 100 uses the laser lights with SONET. it can accommodate a digital transmission link with the capacity of 1.544 Mbps to many different users across remote distances.

One example of the communication system 100 uses an infrared laser with a wavelength of approximately 1550nm. Of course, those skilled in the art will appreciate that a particular wavelength in the light region of the electromagnetic spectrum is not required by the embodiment. Instead, any wavelength in the light region may be.used.

The light cones 106a-c and the collimated light beams 108a-c can be generated using any well-known holographic optical elements that shape, filter, and diverge or collimate the light appropriately. For example, beam shaping can be accomplished using diffraction gratings, lenses, holographic optical elements, or other standard beam-shaping optic. Wavelength filtering, used in various channelization schemes, can also be achieved usin-g a variety of standard optical components such as interference filters, diffraction gratings, or prisms.

As is described more fully below, the light cones 106a-c bit rate in one embodiment may be between 10 Mbps and 10 Gbps, inclusive. Of course, those skilled in the relevant art will appreciate that a particular data rate is not required. That is, support is provided for any number of data rates.

As is the case with the light cones 106a-c. the collimated light beams 108a-c also can be laser beams or any light beam at a wavelength in the.

"light" region of the electromagnetic spectrum, including visible light, nearinfrared light, and infrared light. Collimating can be accomplished in a wellknown manner, such as by using a diffraction gratings, lenses. or other standard beam-shaping optics.

Of course, those skilled in the art will appreciate that, while much of the communications within the communication system 100 involves the wireless exchange of extremely high-speed. broadcast. digital data. the communication network 100 also supports conventional methods of data communication, such as telephone lines. For example, a central network 102 can transmit Internet video data at an extremely high speed to a user network 104 using a light cone 106a, with the return communication from the user network 104 to the central network 102 being via a standard telephone line. This may be the case when the Internet data is graphics and text. and the user data is credit card information, for example. This also may be the case when the Internet data is graphics and text. and the user data is user authorization information, for example.

Moreover, those skilled in the art will appreciate that, while the communication system 100 can involve the wireless exchange of extremely highspeed, broadcast, digital data, the communication system 100 can use other data rates. That is. the communication system 100 can communicate at data rates commensurate with the type service being provided, the quality of service requested type of information transmitted and/or received, etc.

Downlink Transmission and Reception Structure Figure 2 is a block diagram of illustrative central network 102 downlink transmission components. In this case, the peripheral networks 105 send data for transmission to the user networks 104 via a central router/switcher 204, a. central downlink signal processor 206, and a central transmit antenna 208. A central system controller 210 controls the operation of the central router/switcher 204 and the central downlink signal processor 206.

Generally. data travels along the thick interconnection lines, while other commands, control signals, etc., travel along the thin interconnection lines. Data and other commands, control signals, etc., may also travel on thin and thick interconnection lines, respectively.

For purposes of explanation, only one central network 102 is described with respect to certain aspects of the embodiment of Figure 2. It is to be understood that the embodiment contemplates one or more central networks 102.

The central router/switcher 204 connects the central network 102 to the peripheral networks 105 and to the user networks 104, enabling data' to be exchanged between them. The central router/switcher 204 can interconnect network interface controllers (NICs). disk controllers, graphic display adapters, etc.. to the central network 102. For example, the central router/switcher 204 supports NICs implemented in a G-NIC Network Interface Card available from Packet Engines of Spokane. Washington, adapted from 830nm to 1550nm.

Other illustrative central router/switcher 204 implementations include well-known 10/100 Mbps Ethernet NICs with 64-bit Peripheral Component Interconnect (PCI) buses, which support either Windows NT T M or the Digital UNIX operating system. When the peripheral network 105 is the Internet. the central router/switcher 204 can support Internet points of presence (POPs).

The central router/switcher 204 in one embodiment is a fiber optic backbone that interconnects lower level network elements in the peripheral networks 105 or the central networks 102. In that case, and where the communication system 100 is a packet-switched network, the central router/switcher 204 is the main path for data packets. Packet-switched networks are described more fully below.

The central router/switcher 204 also interconnects the components that transmit the light cones 106 and receive the collimated light beams 108. The central router/switcher 204 manages the routing of data through the communication system 100. For example the central router/switcher 204 divides the central network 102 into logical software-oriented sub-networks, enabling data traffic to be more efficiently routed. The central router/switcher 204 also performs load balancing, partitioning, and statistical analysis on data traffic. The central router/switcher 204 also determines routing priorities. and performs troubleshooting tasks. The central router/sxvitchecr 204 also selects the paths that data from the light beam 108 or data to the light cone 106 will take in the communication system 100. The central router/switcher 204 may dynamically route data based on the quality of service required or the amount of data traffic in the central network 102.

In one example, the central router/switcher 204 implements a link state routing algorithm that calculates routes based on the number of routers.

transmission speed, delays, and route costs. This can be implemented using an "-open shortest path first" (OSPF) protocol running on a PowcrRail 5200 Gigabit Ethernet routing switch available from Packet Engines.

The central router/switcher 204 also includes several queues that hold data waiting to be routed.

The central downlink signal processor 206 receives the data to be sent to the user networks 104 from the central router/switcher 204 and encodes.

modulates, encrypts, buffers, and amplifies the data to produce a carrier whose frequency is in the visible or near-infrared region of the electromagnetic spectrum. A carrier with such a high frequency is sometimes referred to herein as an "optical signal," an "optical carrier." a -carrier." a -carrier signal." a "lightwave signal." a "light cone." or a "'light beam." The central downlink signal processor 206 also shapes the carrier signal for transmission by the central transmit antenna 208. The structure and operation of the central downlink signal processor 206 is described in greater detail below with reference to Figure 4, including queuing of data waiting to be processed.

The central transmit antenna 208 transmits the carrier into free space. For purposes of explanation, only one central transmit antenna 208 is described with respect to the illustrated embodiment of the invention. It is to be understood that the embodiment can contemplate one or more central transmit antennas per local central network and one or more central networks per geographic location.

The central transmit antenna 208 transmits the carrier into free space using geometric optics. such as refractive.

reflective. diffractive, or holographic optics. Imaging geometric optics (IGOs) have the capability of making an image ofan object. The image may either be a 'real image" or a "virtual image." A real image is onec that is cast on a screen, for example. A virtual image is viewed throuch an eyepiece.

To accomplish this task. an IGO has two properties: Parallel light rays passing through the optics are focused to a single point (the "focus"): and Light rays incident from different angles are focused to different foci. all of which lie in a plane (the "focal plane"). A telescope. camera lens, shade projector, magnifying lenses. and contact lenses are examples of imaging geometric optics.

Non-imaging geometric optics (NGOs) do not satisfy at least one of the criterion necessary for an IGO. If one tries to observe an image created by NGOs, the image will either be fuzzy" or nonexistent. Examples of NGOs are the Fresnel lenses used in front of motor vehicle headlights or the rippled .privacy" glass used in certain windows where privacy is required.

A diffraction grating is an example of an NGO suitable for implementing the communication system 100. Of course, any diffraction grating suitable for focusing the desired wavelength that can focus the light cone 106 into a small enough spot could be used. In this case, a diameter for the light cone 106 is 60 microns. Those skilled in the art will appreciate that the particular diameter is dependent upon the desired data rate.

Although IGOs are adequate. they are expensive and the embodiment does not require all of their capabilities. Thus, one example uses NGOs to maximize the utility of the system while minimizing the cost of the transmit and receive optics. A suitable non-imaging geometric optic operating in the 1550nm range is available from Richardson Labs in Meridian, Idaho.

The central system controller 210 controls the operation of the central router/switcher 204. and the central downlink signal processor 206. The central system controller 210 can be implemented in hardware. software. or a combination of both hardware and software. In aspects that are implemented using software, the software may be stored on a computer program product (such as an optical disk, a magnetic disk. a floppy disk. etc.) or a program storage device (such as an optical disk drive, a magnetic disk drive, a floppy disk drive, etc.). The central system controller 210 may also be custom software running on a composite of computers (or processors).

Figure 2A illustrates a flow diagram of a central system controller 210 transmit function 200 suitable for implementing the custom software running on a composite of computers. Operation of the transmit function 200 begins with step 211, where control immediately passes to step 212. In step 212. the transmit function 200 determines which of its data queues advances next to send data to the central downlink signal processor 206. In step 214, the transmit function 200 synchronizes encoding and multiplexing schemes. In one case, a user system controller 310 (see. Figure 3) synchronizes encoding and multiplexing schemes with the user networks 104. That is. the central system controller 210 performs handshaking with the user networks 104 to initiate a data transfer.

In step 216, the transmit function 200 determines the particular encoding required. Typically, the user networks 104 control the encryption scheme. while the central networks 102 control the multiplexing and encoding schemes. Thus, in one example, the central controller 210 determines the particular encoding required.

In step 218, the transmit function 200 decides when a data packet is to be transmitted. In an example, the central system controller 310 makes this decision. Operation of the transmit function 200 is complete following step 218, as indicated by step 220.

The output of the central networks 102 on the downlink are the light cones 106. which are transmitted into free spa.ic and received by the user networks 104. That is. each of the central networks 102 transmits data modulated on a shaped and diverging coherent or other liuht beam throueh free space.

Figure 3 is a block diagram of illustrative user network 104 downlink reception components. A user antenna 302 receives data transmitted Irom the central network 102. processes it using a user do\vnlink signal processor 304. and sends the data to user equipment and devices 308. the user system controller 310. and/or any of the peripheral networks 105. For purposes of explanation, only one user network 104 may be described with respect to certain aspects of the anrrangement shown in Figure 3. It is to be understood that one or more user networks 104 are contemplated.

As mentioned above, the user antenna 302 receives the light cones 106 from free space. The user antenna 302 receives the light cones 106 using an optical receiving antenna, which, in one case, uses holographic optical elements. One example uses well-known telescopes to receive the light cones 106. For example, the user antenna 302 can be a reflective telescope with a modified eyepiece to further confine the spot size of the received light. The user antenna 302 outputs the received light cones 106 to the user downlink sienal processor 304.

The user downlink signal processor 304 receives the light cone 106 and decodes, demodulates. decrypts, and buffers it to separate the data from the carrier. The structure and operation of the user downlink signal processor 304 is described in greater detail below with reference to Fieure The user input/output interface 306 interconnects the user equipment 308. the user system controller 310. and the peripheral networks 105.

Recall that in one example, the user network 104 is operated by a user that subscribes to send and receive data in a client-server environment. such that the central networks 102. the user networks 104, and !he peripheral networks 105 connect "client" systems with **server" systems. The user input/output interface 306 interconnects the client systems with the server systems using appropriate signaling and protocols. In one aspect, the user input/output interface 306 supports well-known full-duplex operation and flow control common to clientserver environments. In another aspect. the user input/output interface 306 supports Signaling Network Management Protocol (SNMP). which is a wellknown method by which network management applications query a management agent using a supported Management Information Base (MIB). This example manages virtually any network type, to include Non-Transmission Control Protocol (non-TCP) devices, such as IEEE 802.1 Ethernet bridges.

The user input/output interface 306 supports bidirectional encryption, with the ability to change keys as needed. The user input/output interface 306 also implements "challenge" and "'reply" authentication when setting the keys. In this instance, the user input/output interface 306 has a unique serial number, even though it does not have a unique network address, which serial number can be used for encryption and other security features. The firmware on the subscriber input/output interface 306 also is protected from hacking.

The user equipment and devices 308 can be any of a variety of well-known equipment, such as gateways. local area networks, bridges. etc. The user equipment and devices 308 also can-be any of a number of well-known user devices, such as printers, hard drives, graphical display adapters, televisions (TVs). TV set top boxes, telecommunication equipment, video conferencing equipment. and audio/visual equipment. such as home theater electronics. etc.

The user system controller 310 operation and structure are similar to the operation and structure of the central system controller 210. in that the user system controller 310 controls the operation of the user downlink signal processor 304 and the user input/output interface 306. The user system controller 310 likewise can be implemented in hardware, software, or a combination of both hardware and software. In cases that are implemented using software, the software may be stored on a computer program product (such as an optical disk. a magnetic disk. a floppy disk. etc.) or a program storage device (such as an optical disk drive, a magnetic disk drive, a floppy disk drive. etc.).

The user system controller 310 may also be custom software running on a composite of computers (or processors). In one example, the user system controller 310 is implemented in a token ring time-division multiplex (TDM) system.

Figure 3A illustrates a flow diagram of a data transmit routine 300 suitable for use with the user system controller 310. The transmit routine 300 begins with step 311. where control immediately passes to step 312 wherein the transmit routine 300 determines the type. amount, and rate of data to be transmitted.

In step 314. the transmit routine 300 communicates the information gathered in step 312 to the central system controller 210. In step 316. the transmit routine 300 transmits data during the life of the token. In step 317, the transmit routine 300 determines if no more data exist, and in step 318 returns a token to the central system controller 210. If in step 318. no more data returns a token to the central system controller 210. the transmit routine 300 returns to step 312.

In step 320, if there is more data. the transmit routine 300 waits for the next token from the central system controller 2!0. and then the transmit routine 300 returns to step 312.

Figure 3B is a receive routine 350 that the user system controller 310 implements in the token ring TDM system embodiment. For example. in step 352, the receive routine 350 receives a data packet and demodulates it. In step 354, the receive routine 350 examines the data packet header, and determines if the data packet address matches a user system address.

In step 356, the receive routine 350 determines whether the address of the data packet matches the user's system address. If the address is a match, then control of the receive routine 350 passes to step 358. wherein the receive routine 350 decrypts the data packet. In step 360. the receive routine 350 sends the data packet to the user's sub-network.

If. on the other hand, in step 356 it is determined that the data packet address does not match a user system address. operation of the receive routine 350 passes to step 362, wherein the receive routine 350 dumps the data packet.

Figure 4 is a block diagram of illustrative central downlink signal processor 206 components. The illustrative central downlink signal processor 206 includes encoders 402. modulators 404. multiplexers 406. and power amplifiers 408 that convert data into a carrier, and amplify the carrier for transmission in free space to the user networks 104.

The encoders 402 convert data into a representation of the data according to a set of rules or conventions specifying the way in which the signals representing the data can be formed, transmitted, received, and processed. In one aspect. the encoders 402 encodes data and control signals into a high-speed data stream. Illustrative encoders 402 are implemented in a Media Access Controller (MAC) chip on Packet Engines' G-NIC. Of course, the encoders 402 can be implemented in any Ethernet card, switch, or repeater with the same encoding capabilities.

The modulators 404 modulate the light cone 106 according to the data to be transmitted on that light cone 106. There are several types of wellknown modulation schemes used for communications frequency modulation. phase modulation, phase-shift keying modulation, quadrature amplitude modulation, etc.), any of which are suitable for implementing communication in the communication system 100. In one example, the modulators 404 are implemented in well-known Ethernet Peripheral Component Interface (PCI) cards whose input and output are via optical fiber. In this case, the modulators 404 use a well-known on-off keying (OOK) amplitude modulation scheme. The OOK amplitude modulation scheme is the lowest cost modulation scheme currently available. Of course, the modulators 404 can be implemented in any Ethernet card, switch, or repeater with the same modulating capabilities. An example uses the serializing/deserializing chip on Packet Engines' G-NIC to implement the modulation task. as well as to drive the laser.

The multiplexers 406 in one aspect are wavelengthl division multiplexers (WDMs) that establish optical channels by combining the wavelengths (or colors) into the light cone 106. That is, the multiplexers 406 mix :several channels at different wavelengths and output the wavelengths on the same light beam. In this aspect, the multiplexers 406 can be well-known passive combiners or selective combiners. In another aspect. the multiplexers 406 are optical time division multiplexers (OTDM), or high density wavelength division multiplexers (HDWDM). Alternatively, multiplexers 406 can be implemented using coherent multi-channel heterodyne or. homodyne detection techniques. In fact, any type of optical combiner that can perform the function of combining the channels, such as fused filter couplers or Soliton multiplexers, also can be used to implement the multiplexers 406. Of course, the invention is not limited by the particular type of multiplexing. For example, the channels can be combined into the light cone 106 using frequency, polarization, spatial position, polarity, space, algebraic transform methods, etc. An example of the multiplexers 406 uses a dense wavelength division multiplexer (DWDM) to select channels at International Telecommunications Union (ITU) standards for the 1530nm- 1560nm range (approximately 0.8nm separation between channels).

The power amplifiers 408 may. receive and amplify one or more wavelengths that will be present in the light cone 106. The power amplifiers 408 tolerate optical signals of many formats (or modulation schemes, such as polarity shift keying or amplitude shift keying) or bit rate (up to many Gbps), the power amplifiers 408 are transparent. In one example of the invention, one geographic locality contains three central network stations. The signals from each of these central network stations are divided into 36 sectors. Each sector is capable of carrying up to eight channels at 100 Mbps to 10 Gbps each. with an overall local geographic capacily of up to 8.650 terabits per second (Tbps) 3 stations x 36 sectors x 8 channels x 10 Gbps.) Preferably, the power amplifiers are erbium doped fiber optic amplifiers (EDFA), that amplify one or more wavelengths simultaneously, available from JDS Fitcel Corporation in Nepean, Ontario. Canada.

Figure 5 is a block diagram of illustrative user downlink signal processor 304 components where user downlink signal processor 304 includes light cone detectors 502, user demodulators 504. user demultiplexers 506, and user decoders 508. which detect and separate data from the carrier in the light cone 106 after it is received from free space by the user antenna 302.

The light cone detectors 502 detect and focus the light cone 106 onto a photodetector (not shown). The light cone detectors 502 may include a concentrator (not shown) which concentrates the light cone 106 and focuses it without loss. After detecting and focusing, the data on the light cone 106 is amplified with a preamplifier (not shown), converted to serial form with a serializer (not shown), and protocol converted using a protocol converter (not shown). The preamplifier. serializer, and protocol converter are available in a G-NIC network interface card manufactured by Packet Engines, as described above with reference to the modulators 404. In this case, the protocol converter can either convert the modulation of the light cone 106 to a Gigabit Ethernet format or reduce it down to a 100 Mbit format. The detectors also include well-known pattern masks, such as diffraction gratings. The light cone detectors 502 output the light cone 106 to the user demodulators 504. Illustrative light cone detectors 502 are implemented in PIN diode in an off-the-shelf 1550nm transceiver unit manufactured by MRV Communications located at 20415 Nordhoff Street. Chatsworth, California 91311.

The user demodulators 504 demodulate the carrier using wellknown demodulation techniques compatible with the modulation schemes used by the modulators 404. For example, the user demodulators 504 are implemented in the Ethernet PCI cards.

The user demultiplexers 506 separate the wavelengths back into frequency-separated independent optical channels using techniques compatible with the multiplexers 406. The demultiplexers 506 can be well-known passive splitters or selective splitters.

The user decoders 508 convert data from the representation of the data established by the encoders 402. For example, the user decoders 508 decodes data and control signals from a high-speed data stream. An example is implemented in a MAC chip on Packet Engines' G-NIC. Of course, the user decoders 508 can be implemented in any Ethernet card. switch, or repeater with the same encoding capabilities. The user decoders 508 output decoded data to the user input/output interface 306. which then makes the data available to the peripheral networks 105.

Any or all of the components in the examples in Figures 2 and 4 or Figures 3 and 5 can be implemented on a single card. respectively. In one instance, the components in Figures 2 and 4 are implemented in a single card from Packet Engines. Similarly, the components in Figures 3 and 5 are implemented in a single card from Packet Engines. Of course, those skilled in the relevantart will appreciate that a particular physical location for the components in Figures 2 and 4 or Figures 3 and 5. respectively, is not essential to practice the embodiment.

Downlink Transmission and Reception Operation Figure 6 is a flow diagram of a downlink data transmission and reception process 600 performed by the central network 102 downlink transmission components, the user network 104 downlink reception components.

and the peripheral networks 105. The process 600 starts at step 602. where control immediately passes to step 604. In step 604. the central router/switcher 204 receives data from the peripheral networks 105 designated for recipients in the user networks 104 or other central networks 102.

In step 606. the central router/switcher 204 routes the data to the central downlink signal processor 206. where in step 608, tile data is processed tor transmission using the encoders 402, modulators 404, multiplexers 406. and power amplifiers 408. Following encoding, modulation. multiplexing, and amplifying, in step 610, the central transmit antenna 208 transmits the data into free space on the light cone 106.

In step 612, the user antenna 302 receives the light cone 106. The user downlink signal processor 304 processes the light cone 106 to remove the data from the carrier, and to separate out one or more of the channels. In step 614. the user input/output interface 306 sends that data to the peripheral networks 105. as indicated.by step 616 and/or to the user equipment and devices 308, indicated by step 618. as appropriate. Following steps 616 and 618, operation of the process 600 is complete. as indicated by step 620.

Uplink Transmission and Reception Structure Figure 7 is a block diagram of illustrative user network 104 uplink transmission components. The peripheral network 105 sends data for transmission to the central networks 102 via the user input/output interface 306 and/or the user equipment and devices 308.and sends it to a user uplink signal processor 702. The user uplink signal processor 702 outputs the data to the user antenna 302 for transmission into free space on the collimated light beam 108.

which is received by the central networks 102. The user uplink signal processor 702 is described more fully below with reference to Figure 9.

Figure 8 is a block diagram of illustrative central networks 102 uplink reception components. A central receive antenna 802 receives data transmitted from the user networks 104, processes the data using a central uplink signal processor 804, and routes the data to the peripheral networks 105 via the central router/switcher 204. The central system controller 210 controls the operation of the central router/switcher 204 and the central uplink. signal processor 804. The central uplink signal processor 804 is described more fully below with reference to Figure Figure 9 is a block diagram of illustrative user uplink signal processor 702 components. The illustrative user uplink signal processor 702 includes user multiplexers 902. user modulators 904. and user optical transmitters 906. The multiplexers 902 operate similarly to the multiplexers 406 in the central downlink signal processor 206. in that the multiplexers 902 can combine channels using WDM, OTDM. HDWDM. coherent multi-channel heterodyne or homodvne detection techniques. fused filter couplers. or Soliton multiplexers. for example.

The user modulators 904 operate similarly to the modulators 404 of the central downlink signal processor 206. For example, the user modulators 904 can implement several types of well-known modulation schemes used for communications. In one aspect of the invention, the user modulators 904 are implemented in well-known Ethernet PCI cards whose input and output are via optical fiber. The user optical transmitters 906 perform well-known optical signal processing on the data prior to output to the user antenna 302. An illustrative optical transmitter 906 includes a laser, an amplifier, and a telescope.

This embodiment uses a telescope manufactured by Mecade in Irvine. California.

whose eyepiece has been adapted to allow a fiber optic element to be inserted into the eyepiece (so that the laser light can be sent into the telescope. and thus.

transmitted into free space).

The output of the user optical transmitters 906 is sent to the user antenna 302. which transmits the multiplexed and modulated data as the collimated light beam 108 to the central networks 102. The central networks 102 receive the collimated light beam 108, process it using the central uplink signal processor 804, and send the data to any of the peripheral networks 105.

Figure 10 is a block diagram of illustrative central network 102 uplink components. As Figure 10 shows, the central receive antenna 802 receives the collimated light beams 108 from free space. The central receive 24 antenna 802 receives the collimated light beams 108 using an optical receiving antenna, which, in one case, uses holographic optical elements.

The central uplink signal processor 804 includes collimated beam detectors 1002. central demodulators 1004, and central demultiplexers 1006. The collimated beam detectors 1002 detect and focus the collimated light beam 108 and provide spatial offsets to spatially separate and separately detect each collimated light beam 108 whether on identical or differing wavelengths. The collimated beam detectors 1002 can be similar to a two-dimensional array of photodetectors. each receiving a collimated light beam 108 from a different user network 104 or a lower level node. The collimated beam detectors 1002 output signals corresponding to the different collimated light beams 108. The central receive antenna 802 outputs the signals corresponding to the different received collimated light beams 108 to the central demodulators 1004. In one embodiment, the collimated beam detectors 1002 focus the collimated light beam 108 onto a I 500nm detector that detects data at rates in excess of 10 Mbps. Such detector is available from MRV Communications.

The central demodulators 1004 demodulate the carrier using wellknown demodulation techniques compatible with the modulation schemes used by the user modulators 904. For example, the user demodulators 1004 are implemented in well-known Ethernet PCI cards.

The central demultiplexers 1006 further separate the wavelen2ths back into spatially independent optical channels using techniques compatible with the user multiplexers.902. As such. the central demultiplexers 1006 can be well-known passive splitters or selective splitters. The central demultiplexers 1006 output data to the central router/switcher 204, which then makes the data available to the peripheral networks 105.

Uplink Transmission and Reception Operation Figure 11 is a flow diagram of' an uplink data transmission reception process 1100 performed by the central network 102 uplink transmission components. the user network 104 uplink reception components. and the peripheral networks 105. The process 1100 starts at step 1102, where control immediately passes to step 1104. In step 1104. the user input/output interface 306 receives data from the peripheral networks 105 and routes the data to the user uplink signal processor 702.

In step 1106. the user uplink signal processor 702 processes the data for transmission using the user multiplexers 902. user modulators 904, and user optical transmitters 906. In step 1108, the user antenna 302 transmits the data into free space on the collimated light beam 108 into free space. In step 1110, the central receive antenna 802 receives the collimated light beam 108 from free space.

In step 1112. the central uplink signal processor 804 invokes steps 352 through 358 of the user system controller 310 receive function 350 (see. e.g., Figure 3B) and processes the collimated light beam 108 to remove the data from the carrier, and to separate out one or more of the channels.

In step 1114. the central router/switcher 204 sends that data to the peripheral networks 105, as indicated by step 1114 and/or to other central networks 102, indicated by step 1116. as appropriate. Following steps 1114 and 1116, operation of the process 1100 is complete, as indicated by step 1118.

It is noted that it can be less expensive to transmit from the user networks 104 to the central network 102 using the collimated light beam 108 as opposed to a shaped and diverging light cone 106. as is transmitted from the central network 102 to the user networks 104. For example, the collimated light beams 108 require less power. Moreover, transmitting using the collimated light beams 108 ensures that there is little interference between bidirectional light transmissions between the central networks 102 and the user networks 104.

Recall that the communication system 100 (see. Figure 1) also supports conventional methods of data communication. Accordingly, the communication network 100 can communicate at data rates commensurate with the medium of communication. For example, the communication system 100 can transmit into free space at one data rate and receive via telephone lines at a different lower) data rate.

Data Packet Structure As described above, the communication system 100 uses packetswitching technology, in which data is divided into individual data packets before transmission and routed through different network elements and may therefore arrive at different times or out of sequence. If received out of sequence. the individual data packets are reassembled at the intended destination.

Figure 12 illustrates a data packet 1200 suitable for use with the communication system 100. The data packet 1200 includes a payload 1202.

which typically is the data content. -For example, the data content can be stock quotes. video/audio for a teleconference, etc. Those skilled in the art will appreciate that the particular payload may vary according to the application and may include information needed to facilitate reassembly of the data packets into the original data sequence.

The data packet 1200 also includes a header 1204. The header 1204 typically includes a destination address 1206 that specifies the destination network element (or recipient) to which the data packet 1200 is to be routed.

That is. the address 1206 specifies which central network 102, user network 104, or peripheral network 105, or their lower level nodes is the designated recipient of the particular data packet 1200. When the recipients recognize their particular address 1206 in the data packet 1200. the recipients accept the payload 1202 appended to the address 1206.

The data packet 1200 also includes a cyclical redundancy check (CRC) 1208, that is used to detect errors in the transmission of the data packet 1200. Other forms of error detection and correction may be used in place of. or in addition to. the CRC 1208. The data packet 1200 may also include error correction data under any conventional error correction method. The data packet 1200 also includes a miscellaneous portion 1210 for miscellaneous control or data information. such as for multicasting or broadcasting sessions. An illustrative data packet 1200 is a SONET data packet structure. An alternative is a standard Internet Protocol (IP) data packet, IPv.4 (IPv.6) data packets with IEEE Ethernet 802.3 framing).

Sectorization Recall that in one example, data is sent from the central networks 102 to the user networks 104 using the light cones 106, and that the light cones 106 are shaped and diverging coherent light beams. Several shaped and diverging coherent light cones 106 are radiated in the substantially circular radiation pattern that illuminates any or all parts of the area surrounding the central networks 102, much like a theatrical spotlight illuminates a stage. Parts of the illuminated-areas can be emphasized, or made "brighter" than others. in order to deliver more signal strength to chosen areas. As is the case with the theatrical spotlight. the light cones 106 can be configured into any shape. The radiation pattern radii can be anywhere from one quarter meter to over three kilometers.

Each central network 102 optically shapes the laser radiation patterns into the narrow radial sectors containing elevation sectors into which the wavelengths of infrared laser lights are transmitted. In one case, the central downlink signal processor 206 shapes the laser beam into the desired radiation pattern, with radial (or horizontal) sectors and/or elevation (or vertical) sectors further divided into several channels. Each channel is allocated particular wavelengths. A user can be assigned a wavelength such that the central networks 102 transmit a high-speed data stream to each user or group of users on the assigned wavelength. Each vertical sector and each horizontal sector may have one or more channels of different wavelengths. Each of the channels may carry at least 10 Gbps of data. This arrangement accommodates a data transmittino capacity in excess of 20 Tbps and can service thousands of users.

Figure 13 illustrates an illustrative transmission point 1301 with sectorization 1300. According to this example, there are several horizontal subsectors, as represented by subsectors 1302a, 1302b and 1302c. Each sector may have vertical subsectors, as represented by subsectors 1306a and 1306b.

Each vertical or horizontal subsector may be further divided into another subsector. Each horizontal subsector 1302a-c and/or vertical subsector 1306a-c can have one or more wavelength channels (not shown).

When the communication system 100 communicates using the transmission point 1301 with the sectorization pattern 1300, the address in the data packet 1200 specifies the appropriate sector 1302 and wavelength channel.

It should be noted that the highly controllable shaped beams make wavelength (or frequency) reuse a non-issue using the communication system 100. The sectors in the communication system 100 are strictly spatially separated, and so any channel can be used in any sector. This spatial reuse technique provides distinct advantages over common non-optical systems.

Conventional frequency reuse schemes were necessary because of radiation pattern side lobe interference caused by well-known right phrasing.

Implementation of sectorization and shaped and diverging coherent light beams 106 avoids side lobe interference problems and. thus, avoids the need for frequency-reuse schemes. To accomplish this, the central transmit antennas 208 use central geometric antennas that are very large in terms of operating wavelength approximately eighty times the wavelength). Conversely, conventional radio antennas are approximately the same size as the carrier wavelength, so they cannot use geometric optics for their transmission sectors.

The transmission point 1301 with the sectorization pattern 1300 can generate several types of "footprints," as defined herein as an area of coverage projected onto the buildings housing the user networks 104 by the beam radiated from the transmission point 1301. In one case, the transmission point 1301 has shaped sectorization designed to project a roughly circular footprint on the buildings housing the user networks 104.

Of course, it is not intended to be limited by the shape of the footprints. Figure 14 illustrates examples of various suitable footprints 1402a-f generated.by the central transmit antennas 208. While, in some cases. only one central transmit antenna 208 is illustrated per set of light cones 106 transmitted, it is to be understood that, for example, the central transmit antenna 208n includes several telescopes, each capable of generating a uniquely shaped radiation pattern. For example, as one telescope of the central transmit antenna 208c generates a light cone 106d which produces a substantially circular footprint 1402d. another telescope of the central transmit antenna 208c generates a light cone (not shown) which produces a substantially heptagonal footprints 1402c.

Other footprints include elliptical, hexagonal. donut-shaped, square, etc. For example, referring back to Figure 13, the subsector 1302a would generate an elliptical footprint. The subsector 1306a produces a hexagonal footprint. The subsector 1306b generates a donut-shaped footprint.

One purpose for overlapping radiation patterns is to deliver data at diffeirent data rates or capacities to the same building. Of course. the particular radiation pattern used is determined by a number of factors. including the size and shape of the building that houses the user networks, for example. that ensure that the power in the optical signal is effectively utilized.

The communication system 100 also can include an optical repeater 1404, which receives, reconstructs, and amplifies either one wav or bidirectionally the light cones 106 and retransmits them to the user networks 104.

The optical repeater 1404 compensates for dead spots in the transmitting radiation patterns. The optical repeater 1404 thus acts as an extension between.

central networks 102. The optical repeater 1404, while depicted as a single element. may contain multiple receiver-transmitter pairs that detect, reconstruct, amplif and retransmit the light cones 106 undcr the components discussed above with respect to Figures 2-6.

Figure 15 shows an illustrative topography 1500 surrounding the central networks 102, by the sectorization pattern 1300. The example depicted in the topography 1500 includes three hexagonal light propagation patterns 1502a, 1502b, and 1502c. In this case, each sectorization pattern 1300 has 36 sectors, where one sector in each sectorization pattern 1300 is represented by the sectors 1502a,, 1502b,, and 1502c,. respectively. An alternative example has 60 radial sectors, each with six degrees of azimuth, and five elevation sectors, each with eight channels accommodating a data rate from 10 Mbps to 10 Gbps. Still another example divides a radiation pattern into 120 three-degree sectors, with each sector delivering 10 Mbps to 10 Gbps to the user networks 104.

Figure 15 also depicts several central networks 102 interconnected by ultra-wide bandwidth optical backbone links 1510. The optical backbone links 1510 also allow interconnection with Internet POPs, major carriers, the PSTN. or other peripheral networks 105.

The systems, methods, and interconnected devices for networked.

high-speed bi-directional data communication through free space described herein are particularly suitable for use in foggy weather conditions, where optical signals are susceptible to attenuation. A study in London. England of point-topoint laser communication produced data on reliability that, when combined with a historical database, produced a weather database with forty years of data collected on an hourly basis. With this kind of information, the parameters of the communication system 100 can be modified to compensate for certain atmospheric conditions. For example, the power output of the central transmit antennas 208 arid/or the user antennas 302, radii of the cells, sensitivity of the detectors and/or the data rate can be increased or decreased as appropriate.

Similarly, the size of the antennas can be adjusted to compensate for any anticipated attenuation of the signal.

The coverage area of the radiation pattern generated by the central transmit antenna 208 also can be predetermined by design to anticipate atmospheric conditions. For example. in the city of Seattle, Washington which is known for foggy conditions typically causing strong attenuation, the radiation patterns can be reduced to one quarter kilometer, as opposed to the two kilometer radiation patterns appropriate for sunny locations.

Other suitable modifications include changing the shape of the light cones 106. changing the tint of the windows through which the light beams/light cones are transmitted, changing the optical amplifier strengths. etc.

Broadcast and Multicast Operation Recall that the communication system 100 broadcasts and multicasts data from the central networks 102. During broadcast operations, the data is transmitted from any one of the central networks 102 or their lower level nodes to all user networks 104 and/or all peripheral networks 105 and/or their lower level nodes. for example. Any well-known broadcast addressing scheme is suitable.

During point-to-multipoint multicast communication. selected user networks 104. peripheral networks 105. and/or their lower level nodes receive.

data. This example is ideal in situations where identical data content is desired to be transmitted to a particular group of user networks 104 and/or peripheral networks 105 substantially simultaneously during video teleconferences).

In this case, the miscellaneous portion 1210 of the data packet 1200. depicted in Figure 12. includes a multicast session identifier (not shown) that identifies a multicast session and a set of users that are the recipients of the transmission during the particular multicast session. The content of the transmission that one member of a multicast session group receives is substantially the same as the high-speed data that another member of the multicast session group receives during a particular multicast session.

Each multicast session identifier is associated with a set of unique addresses. There is a unique address for each recipient of the multicasted data.

The central network 102 transmits the multicast session identifiers to the recipients, which use the association to determine the unique address for each of the recipients associated with the set of unique addresses. The central network 102 adds the unique addresses for the recipients to each data packet 1200 received from the other interconnected networks prior to transmitting the received data packet 1200 to the specified set of recipients.

Each central network 102 also may include a plurality of multicast session identifier translation tables to translate multicast session identifiers into unique addresses for the subscribers. There may be one or more multicast sessions identified by multicast session identifiers. Each of the multicast session identifiers is associated with a set of unique addresses representing a set of users.

The central network 102 includes at least one translation table to correlate the multisession identifiers with each set of unique addresses for the set of selected recipients.

Table I is an example of a multicast session identifier table suitable for use with one example. Table 1 lists example multicast sessions (1 through functional group identifiers (A through D) for the functional groups associated with a particular multicast session, sets of addresses for the particular recipients in the particular fuinctional group, and recipients associated with the unique addresses designated to receive transmissions during the particular multicast session. Note that the multicast sessions may have overlapping recipients such that one recipient may be included in the multicast session as well as in the multicast session Note that the recipients are designated 104a through 104(1 to represent either several user networks 104 or several of their lower level nodes.

Table 1 Multicast Functional Sssion Group i I) Unique Add rcsses Recipients Session Group ID' I A 0112.3456.7890 104a 0223.4567.8901 104b 0334.5678.9012 104c 0445.6789.0123 104d 2 B 0445.6789.0123 104d 0223.4567.8901 104b 0334.5678.9012 104c 3 C 0445.6789.0123 104d S01 12.3456.7890 104a 4 D 0445.6789.0123 104d 0334.5678.9012 104c Figure 16 is a flowchart showing an illustrative multicast process 1600. The multicast process 1600 starts at step 1602. where control immediately passes to step 1604. In step 1604, one of the peripheral networks 105 transmits high-speed data and a multicast session identifier to the central network 102. For example, according to Table 1, during the first multicast session. one of the peripheral networks 105 transmits the functional group identifier to the central network 102.

In step 1606. the central network 102 receives the high-speed data and the multicast session identifier. In step 1608. the central network 102 determines the functional group associated with the multicast session by looking in its translation table. In step 1610, the central network 102 determines the set of recipients in the functional group.

In step 1612. the central network 102 determines the unique address of each recipient in the set of recipients in the functional group. For example, the central network 102 looks in its multicast session identifier translation table to determine the unique address for the sets of recipients associated with the functional group identifier In step 1614. the central network 102 adds the unique address for the sets of recipients to the high-speed data received from the central network 102 and transmits the resulting high-speed data to the recipients 104a-d. Once the high-speed data has been transmitted from the central network 102 to the recipients 104a-d, the multicast process 1600 ends. as indicated by step 1616.

It is noted that the multiplexing and demultiplexing schemes used by the central networks 102 differ from the multiplexing and demultiplexing schemes. used by the user networks 104 in that the central networks' 102 multiplexing and demultiplexing schemes have additional levels of address translation to accommodate routing of incoming IP addresses to the appropriate addressees. The additional routing is implemented in the central router/switcher 204.

All of the optics described herein can be enclosed in a "black box." such as a Faraday cage. to isolate the optical components from outside interference such as extraneous optical frequencies. Enclosing the optics in a black box is less expensive and simpler than conventional methods for eliminating outside interference.

Recall that the central router/switcher 204 connects the centra! network 102 to the peripheral networks 105 and to the user networks 104.

enabling data to be exchanged between them. Recall further that the central router/switcher 204 supports NICs implemented in a G-NIC Network Interface Card available from Packet Engines. Figure 17 shows an illustrative central router/switcher 204 implemented on the G-NIC Network Interface Card.

The central router/switcher 204 in this embodiment includes a gigabit uplink port 1702 and up to two server ports: an optional gigabit server port 1704 and a 10/100 Ethernet server port 1706. The central router/switcher 204 also includes a glue logic and memory control processor 1707. The gigabit uplink port 1702 receives data packets 1200 on its input and sends the data packets 1200 to the output of whichever server port is active. At the same time.

the central router/switcher 204 sends any data packets 1200 received on an input of the active server port to the output of the gigabit up link port 1702.

It is noted that all data packets 1200 coming from either server port 1704, 1706 will be sent to the gigabit uplink port 1702, but the data packets 1200 coming from the gigabit uplink port 1702 destined for either server port 1704, 1706 will be filtered by the glue logic and memory control processor 1707. That is, only the data packets 1200 meeting the filter requirements will be sent to the appropriate server port 1704. 1706. At a minimum, the gigabit uplink port 1702 filters received data packets 1200 by accepting only the data packets 1200 destined for a particular Ethernet address. In this case, the gigabit uplink port 1702 also accept broadcast data packets and multicast data packets. In one example, filtering may be performed by a host computer system under the purview of a user network 104.

The central router/switcher 204 in another example is is connected from one of the server ports directly to a matching port on a host computer system located at a user network 104. In this case, if the gigabit uplink port 1702 uses the same Ethernet address as the port on the host computer system, the central router/switcher 204 supports only that host on its gigabit uplink port 1702. This is because the Ethernet address of the host computer system is programmed into the central router/switcher 204.

In another example, the central router/switcher 204 "autodiscovers" its Ethernet address from the data packets 1200 seen on the server ports. Alternatively. central router/switcher 204 is preprogrammed with the same Ethernet address as an Ethernet card assigned to the host computer system.

Some Additional Features The communication system 100 increases both the transmit and receive communication capacity of conventional communication systems. The greater capacity is important to note because standard telephone lines are being pushed to their limit and can provide only approximately 60 Kbps of data network connection. Other network alternatives have been developed but have their limitations as well. For example, ISDN, once thought to be the wide area networking solution of choice, is limited to 128 Kbps. The newly touted ADSL services are limited to eight Mbps and are asymmetric (fast in only one direction-the downlink). Existing personal computers (PCs) have the ability to network locally at over 100 Mbps. leaving these wide area network technologies extremely inadequate.

The most publicized attempt to break the bandwidth bottleneck incorporates satellites in low-Earth orbits (LEO). These satellite networks can obtain data down-link rates from 1.5-28 Mbps. The cost to deploy these systems.

however, ranees into billions of dollars and requires years to deploy.

Fiber optic and LMDS are also available and planned technologies in the telecommunication market. While LMDS is thought to require only percent of the capital cost of deploying optical fiber, there appears to be an upper limit from four to six Gbps of total traffic capacity per four kilometer wide cell, which places a significant limit on system growth. For example. in an area twice the size of downtown Seattle's business core. only 40 to 60 concurrent customers could have 100 Mbps access. In contrast, the optical communication system 100 can potentially serve up to thousands of such concurrent connections.

The communication system 100 may only require 30 percent of the capital cost of an LMDS (or approximately eight percent of fiber) without the two Gbps limitation of total capacity per cell. Recall that the communication system 100 has the ability to communicate at 2.5 Gbps duplex or 1.25 simplex per channel, and its overall capacity per system may be in excess of two Tbps.

This capacity is 1,000 times higher than LMDS and translates to significantly lower infrastructure costs, and the ability to undercut competitors' pricing and/or outperform competitive offerings.

The communication system 100 accomplishes these staggering speeds/volumes by combining wireless, fiber, and networking concepts to form a unique network that has the ability to deliver terabits of information around the world in a very timely and cost-efficient manner.

The communication system 100 antennas are similar in size and shape to a small dish antenna of the type that can be found on many rooftops.

However, the antennas may be placed behind a window glass. making deployment much easier than rooftop-only installations.

While the technology that the communication system 100 implements allows for a radiation pattern radii well over three kilometers. for urban cores, however, the central networks. 102 can be much smaller and dependent upon the geography of the region as well as the building size and building location. Moreover, as described above, the communication system 100 has a very advantageous channel re-use property, allowing significantly lower costs- significantly higher capacities, and greater bandwidth.

Using a very simple example, assume one central network 102 is sectored into 120 three-degree sectors. with each sector delivering 100 Mbps to Gbps. In this very simple example, this single central network 102 has the ability to deliver 300 Gbps to a large number of users. With the addition of additional channels per sector, the data throughput increases significantly. By using eight channels per sector, the optical communication system 100 has The ability to effectively increase the data throughput on a single local central network 102 to 2.4 Tbps. Such a central network 102 could supply 100 Mbps service to 24,000 concurrent users. This far exceeds conventional communication systems. The only close competitor is LMDS. which currently is limited to about four Gbps per cell site.

Many of the components in the communication system 100 may be implemented using hardware, software, or a combination of hardware and software, and may be implemented in a computer system or other processing system. In aspects implemented using hardware,. the hardware components may be Application-Specific Integrated Circuits (ASICs), or a hardware state machine. In aspects that are implemented using software., the software may be stored on a computer program product (such as an optical disk.

a magnetic disk, a floppy disk, etc.) or a program storage device (such as an optical disk drive, a magnetic disk .drive, a floppy disk drive, etc.). That is.

software may be available from a removable disk or from code downloaded on a hard drive. Moreover, the software can include code stored in a module such as a Read-Only Memory (ROM). Programmable ROM (PROM), or any variation of an Erasable PROM EPROM. EEPROM. etc.).

According to one example, the communication system 100 uses well-known Time Division Multiple Access (TDMA) techniques. In TDMA, each user network 104 is assigned one or more TDMA time slots based on the allocated wavelength (or data rate), and the networks communicate with each other during the designated TDMA time slots. When the communication system 100 uses TDMA technology, the communication system 100 can multiplex several user networks 104 on one TDMA channel, using a well-known diffraction grading (or pattern mask) to receive only certain bits from the data stream for each user network 104.

A resource manager (not shown) coordinates assignments of TDMA time slots. The resource manager negotiates for a channel a time slot at a particular frequency).

Interconnection of the arrangement of the light cones 106 and the collimated light beams 108 may be done using standard Internet protocols, such as "open shortest path first" (OSPF), which is a link state routing algorithm that is used to calculate routes based on the number of routers. transmission speed, delays, and route costs. Interconnection of the light cones 106 and the collimated light beams 108 can also be accomplished using other well-known routing algorithms.

Figure 18 shows an alternative example of the communication system 100.

This alternative example uses a multi-access receiver/transmitter (MART) 1802 for both transmission and reception: The central network 102 is connected to the MART 1802 by a transmission link 1800.

The transmission link 1800 is a hardwire link, such as a telephone line or fiber optic cable, but it is also possible to use a wireless link radio frequency,.

laser light, etc.). Additionally, while Figure 18 depicts the central network 102 and the MART 1802 as being separated. remote components. it is appreciated that the MART 1802 can be within the central network 102.

The MART 1802 includes an array 1804 of central transmit antennas 208 and central receive antennas 802. The central transmit antennas 208 in Figure 18 are coaxially located at the center of their respective central receive antennas 802. Other modifications are possible. For instance, the central transmit antennas 208 may be located near (e.g separated from) their respective central receive antennas 802, instead of being coaxially located. It is also possible to use the same optical device to transmit and receive if wavelength separation between the transmitted and received signals is adequate.

Downlink transmission from the central network 102 to the user network 104 and/or the peripheral network 105 uses a concept of splitting a single broadcast beam into several light cones. 106, with each light cone 106 having all of the information present in the single broadcast beam. First, one or more power amplifiers 408, such as a 500 mW EDFA, in the MART 1802 splits the single broadcast beam received through the transmission link 1800 and provides the individual signals to respective central transmit antennas 208. The central transmit antennas 208 then transmit the individual signals as light cones 106 to the user network 104 and/or the peripheral network 105. The array 1804.

or the individual central transmit antennas 208 and central receive antennas 802.

can be mounted, for example, onto one or more gimbal structures to direct the transmitted light cones 106. Available optics are used to focus and direct the light cones 106 as necessary.

The example shown in Figure 18 allows one or more light cones 106 to be focused on particular receivers in the user network 104 or the peripheral network 105. That is, instead of transmitting to an entire building, separate light cones 106 can be transmitted to particular receivers in the building.

Further. the separate light cones 106 can have different power, such that light cones 106 having greater power are transmitted to receivers that are farther away or are behind darkly tinted windows, and light cones 106 having less power are transmitted to closer-range receivers. Also, the MART 1802 can transmit to more than one building, such that some light cones 106 are transmitted to one building and other light cones 106 are transmitted to other buildings. By adjusting the power level of the transmission and pointing the central transmit antennas 208 in the appropriate direction, it is thus possible to "link" several buildings and at greater distances from the same MART 1802. To maximize efficiency, a given power output of the power amplifier 408 can be apportioned between the various light cones 106, such that light cones 106 requiring less power are reduced in power while the other light cones 106 requiring more power are correspondingly increased in power.

Further. the scope of transmission coveraoe of the MART 1802 is easily changed by adjusting the number of splits in the power amplifier 408. A sector of up to a full hemisphere is possible by splitting a single broadcast signal with the power amplifier 408 and providing central transmit antennas 208 in each quadrant.

The MART 1802 can also receive collimated light beams 108 from the user network 104 and/or peripheral network 105. A plurality of collimated light beams 108 transmitted from individual transmitters in the user network 104 and/or the peripheral network 105 are received by the central receive antennas 802 in the MART 1802. Like the transmission from the MART 1802 described above, the uplink transmission of collimated light beams 108 from the user network 104 and/or the peripheral network 105 to the MART 1802 allows multiple signals to be linked at the MART 1802.

Many possible design parameters can be used for the embodiment shown in Figure 18. For instance, a 12° sector can project a light cone 106 of 100 meters in diameter at a distance of 500 meters. A three mrad beam can project a light cone 106 having a diameter of 1.5 meters at a distance of 500 meters. Using the same transmit power and assuming zero losses during the split, a three mrad beam can be projected at each of 4.444 customers and have the same power density as the 12° sector. Alternatively. service can be provided to 100 customers, with a 16 dB of link margin for each. The increased link margin can be used to reduce the size and costs of each customer's receiver.

Although specific aspects of. and examples for the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention and can be made without deviating from the spirit and scope of the invention, as will be recognized by those skilled in the relevant art. For instance, although a laser has been described herein as generating the various light beams and light transmissions, other light-generating devices, such as light-emitting diodes (LEDs). can be used. Also, although the collimated light beams 108 are used in the network uplink components (see. e.g., Figures 7-10) and the light cones 106 arc used in the network downlink components (see, Figures 2 and 3-5) in the examples described herein, it is to be appreciated that in some cases, the network uplink components can use the light cones 106 or the network downlink components can use the collimated light beams 108. Further, several channels frequency domain) can be used in the uplink as well. with appropriate coordination between a user and a central node.

The teachings provided herein can be applied to optical links made functional by any standard network interconnection. For example, the G-NIC Network Interface Card (see. e.g., Figure 2) can be implemented in PCs. Further. one or more components or functions of the communication system 100 can be embodied in a computer network, computer-readable media (such as magnetic cassettes. digital video disks, CD-ROMs, Bernoulli cartridges, random access memories (RAM), ROMs, smart cards, etc.) and their associated devices. One or more components or functions of the communication system 100 can be embodied in computerreadable or computer-executable instructions such as program modules or macros executable by a microprocessor or by a computer. How to implement these types of features can be understood by one skilled in the art based on the detailed description provided herein.

P:\OPERDW~f377979 spa I.doc-8/10/03 42 These and other changes can be made to the invention in light of the abovedetailed description. In general, in the following claims, the terms used should not be construed to limit the invention to the specific aspects disclosed in the specification and claims, but should be construed to include all optical communication systems that operate under the claims to provide, inter alia, high-speed optical data communication.

Accordingly, the invention is not limited by the disclosure, but instead the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (74)

1. A method for transmitting data between a central point and at least one user, the method comprising: at the central point, modulating data and at least one user address on a light beam; at the central point, transmitting the light beam through free space; demodulating the light beam and retrieving the data and the at least one user address; routing the data to the user according to the user address; and transmitting data from the user to a central point.

2. The method of claim 1 wherein the light beam on which the data and the at least one user address is modulated comprises a shaped and diverging light beam.

3. The method of claim 1 wherein the light beam on which the data and the at least one user address is modulated comprises a shaped, diverging, and coherent light beam.

4. The method of claim 1 wherein the light beam on which the data and the at least one user address is modulated comprises a laser beam.

The method of claim 1, further comprising; modulating the data and several user addresses on a light beam; routing the data to the several user addresses; and transmitting data from at least one of the users to a central point through free space or via at least one telephone line.

6. The method of claim 1, further comprising transmitting the light beam through free space to several user addresses in a point-to-point, point-to-multipoint, mulitpoint-to-point, multipoint-to-multipoint manner.

7. A communication system, comprising: a central node configured to transmit through free space an information signal modulated on a diverging coherent light beam; and P:NOPER\ArI 2430060 div.doc-29/03/04 44 a user node configured to receive from free space the diverging coherent light beam and automatically process the modulated informational signal, wherein the diverging coherent light beam, as received at the user node, has different dimensions diverging coherent light beanm at the central node.

8. The communication system of claim 7, further comprising: a plurality of central nodes each configured to transmit through free space a plurality of information signals modulated on a plurality of diverging light beams; and a plurality of user nodes each configured to receive from free space the informational signals modulated on diverging light beams, wherein the central nodes are configured to transmit to the user nodes in a broadcast, simulcast, or multicast manner.

9. The communication system of claim 7, wherein the central node is configured to transmit through free space to the user node in one of a broadcast or multicast manner.

The communication system of claim 7, further comprising a peripheral node configured to transmit the information signal to the central node for modulation.

11. The communication system of claim 7, further comprising a common carrier, virtual node, or an area node configured to transmit the informational signal to the central node for modulation.

12. The communication system of claim 7, wherein the central node and the user node are interconnected using synchronous optical network (SONET) architectures.

13. The communication system of claim 7, further comprising a peripheral node, wherein the central node, user node, and peripheral node are interconnected using synchronous optical network (SONET) architectures.

14. The communication system of claim 7 wherein the central node and the user node are interconnected using gigabit Ethernet architectures.

P:)PER\,ri\12430060 div.doc-29/03/04 45 The communication system of claim 7, further comprising a peripheral node, wherein the central node, user node, and peripheral node are interconnected using gigabit Ethernet architectures.

16. The communication system of claim 7 wherein the diverging light beam comprises a shaped, coherent infrared laser operating at a wavelength of approximately 1550nm.

17. The communication system of claim 7 wherein the diverging light beam comprises a shaped coherent infrared, near-infrared, or visible light laser beam.

18. The communication system of claim 7 wherein the light beam comprises a shaped and coherent diverging light beam.

19. The communication system of claim 7, further comprising a diffraction grating, beam shaping lens, or a holographic optical element.

The communication system of claim 7, further comprising a beam shaping optic that horizontally shapes the diverging light beam.

21. The communication system of claim 7, further comprising a beam shaping optic that vertically shapes the diverging light beam.

22. The communication system of claim 7 wherein the information signal further comprises at least one data packet having a header and a payload, the header specifying at least one of the user nodes and the payload comprising high-bandwidth data.

23. An apparatus configured to transmit an optical carrier through free space to a plurality of user nodes, comprising: an input port configured to receive an information signal; a radiant energy generator configured to generate an optical carrier; a signal processor, coupled to the radiant energy generator and the input port, configured to process and combine the optical carrier with the information signal; and P:\OPER\AI\i 2430060 dvdoc-29/03/04 46 an antenna, coupled to the signal processor, configured to produce a shaped and diverging radiant energy and to transmit the combined optical carrier and information signal on the shaped and diverging radiant energy into free space.

24. The communication system of claim 23, further comprising a multiplexer configured to combine several information signals from several wavelength channels into the optical carrier.

The communication system of claim 23, further comprising an optical time division multiplexer (OTDM), high density wavelength divisional multiplexers (HDWDM), a coherent multi-channel heterodyne detector, a coherent multi-channel homodyne detector, a fused filter coupler, a Soliton multiplexer, a frequency combiner, a polarity combiner, a spatial combiner, or an algebraic transform combiner configured to combine several information signals from several channels into the optical carrier.

26. The communication system of claim 23 further comprising a power amplifier, an erbium-doped fiber amplifier, or a ytterbium-doped fiber amplifier configured to amplify the optical carrier.

27. The communication system of claim 23, further comprising an encoder configured to encode data and control signals into the information signal.

28. A method for transmitting data, comprising: combining several data channels into a data stream; modulating the data stream on at least one diverging light beam; transmitting the diverging light beam through free space; demodulating the diverging light beam and retrieving the data stream; and separating the several channels of data from the data stream.

29. The method of claim 28, further comprising: modulating the data stream on a shaped and diverging light beam; and routing the several data channels to several user devices.

P:\OPER\Ari\i 2430060 div.doc-29/03/04 47 The method of claim 28, further comprising modulating the data stream on a shaped, diverging, and coherent light beam.

31. The method of claim 28, further comprising modulating the data stream on at least two laser beams having different wavelengths transmitted over substantially the same diverging cone through free space.

32. The method of claim 28, further comprising transmitting the diverging light beam through free space to several users in a point-to-point, point-to-multipoint, multipoint-to- point, or multipoint-to-multipoint manner.

33. The method of claim 28, further comprising encrypting data on several data channels.

34. The method of claim 28, further comprising encoding data on several data channels.

An apparatus for receiving an information signal, comprising: an antenna configured to receive from free space an optical carrier having an information signal modulated on a shaped and diverging coherent light beam; a signal processor, coupled to the antenna, configured to process and demodulate the shaped and diverging coherent light beam to separate the information signal from the optical carrier; and an output port, coupled to the signal processor, configured to send the information signal to at least one device.

36. The communication system of claim 35 wherein the antenna includes at least one holographic optical element or a telescope.

37. The communication system of claim 35 wherein the signal processor includes at leats one shaped and diverging coherent light beam detector, a demodulator, a demultiplexer, or a decoder. P:AOPERrI\ 2430060 div.doc-29/03/04 48

38. The communication system of claim 35 wherein the interface is configured to send the informational signal to one of a signaling node management protocol (SNMP) device, a transmission control protocol (TCP) device, a gateway, a local area node, a bridge, a printer, a hard disk drive, a graphical display adapter, a television, a television set top box, telecommunication equipment, video conferencing equipment, audio/visual equipment, or home theater electronics.

39. A method of transmitting and receiving data, comprising: receiving encoded data and a multicasting session identifier, the multicasting session identifier indicating a group of recipient user points selected from among a plurality of user nodes configured to receive the encoded data; transmitting the encoded data and a multicasting session identifier on a shaped and diverging light beam via free space to the plurality of user nodes; receiving the shaped and diverging light beam from free space; and decoding the encoded data.

The method of claim 39, further comprising appending to the encoded data a group of unique user node addresses respectively representing the group of recipient user nodes.

41. The method of claim 39, further comprising modulating the encoded data and the group of unique user node addresses on a shaped and diverging light beam.

42. A data communication system, comprising: a transmitter configured to transmit an informational signal through free space modulated on a shaped and diverging coherent light beam, wherein the coherent light beam is sufficiently divergent to be received by a plurality of spatially separated receivers; and a set of receivers, selected from among the plurality of receivers, configured to receive the shaped and diverging coherent light beam from free space and decode the modulated informational signal.

43. The system of claim 42 wherein each receiver in the set of receivers has a unique receiver address and the transmitter is configured to add the unique receiver address to the informational signal before transmitting informational signal to the set of receivers. P:\OPER\~AI\l2430060 div.doc.29/03/04 49

44. The system of claim 42 wherein the transmitter is configured to transmit the informational signal using data packets having a multicasting session identifier associated with high-speed data and a set of selected receivers.

The system of claim 42, further comprising a storage device, coupled to the transmitter, configured to store a multicasting session identifier translation table to translate first and second multicasting session identifiers into unique receiver addresses of first and second sets of receivers, respectively.

46. A method for free space optical data communication, comprising: receiving at an antenna, a shaped and diverging coherent light beam transmitted through free space, wherein the light beam has an information signal modulated thereon, and wherein a cross-sectional area of the received diverging coherent light beam as received at the antenna is substantially greater than an area of the antenna; and demodulating and recovering the information signal from the shaped and diverging coherent light beam.

47. The method of claim 46 wherein the information signals comprises at least one video signal, audio signal or data signal.

48. The method of claim 46 wherein the high-speed information signals comprises at least one video signal at a first data rate, an audio signal at a second data rate, or a data signal at a third data rate.

49. A data communication system, comprising: a transmission node having at least one radiant energy generator that generates information bearing radiant energy beams over several sectors; wherein each subsector comprises a channel, and wherein each channel operates at substantially the same wavelength. The data communication system of claim 49 wherein the sectors comprise radial sectors.

P:\OPER A, \2430060 div.doc-29/03/04

51. The data communication system of claim 49 wherein the sectors comprise elevation sectors.

52. The data communication system of claim 49 wherein the sectors comprise radial sectors, wherein each sector includes at least two subsectors, and wherein the subsectors comprise elevational subsectors.

53. The data communication system of claim 49 wherein the sectors include at least one elliptically-shaped sector, hexagon-shaped sector, donut-shaped sector, elliptically- shaped subsector, hexagon-shaped subsector, or donut-shaped subsector.

54. The data communication system of claim 49 wherein each channel operates approximately at a 1550nm wavelength.

55. The data communication system of claim 49 wherein a first channel operates at a first wavelength and a second channel operates at a second wavelength.

56. The data communication system of claim 49 wherein the transmission node comprises a telescope.

57. A method of transmitting data comprising: modulating at least one information signal on at least one carrier; and substantially simultaneously transmitting the modulated information signal along a plurality of vertically differentiated sectors.

58. The method of transmitting data of claim 57, further comprising substantially simultaneously transmitting the modulated information signal along a plurality of horizontally differentiated sectors.

59. The method of transmitting data of claim 57, further comprising transmitting a plurality of channel wavelengths over each of the plurality of vertically differentiated sectors.

P;OPER\AI\l12430060 div.doc-29/03/04 -51 The method of transmitting data of claim 57 wherein at least two of the plurality of vertically differentiated sectors have differing cross-sectional beam shapes.

61. The method of transmitting data of claim 57 wherein each of the plurality of vertically differentiated sectors includes information modulated at the same wavelength.

62. The method of transmitting data of claim 57 wherein the at least one carrier comprises a plurality of diverging coherent light beams transmitted along the plurality of vertically differentiated sectors.

63. A communication system, comprising: a central node configured to split an input signal into a plurality of substantially similar output signals; a plurality of transmitters disposed in the central node to transmit the plurality of output signals to a user node as light signals; and a plurality of receivers disposed in the central node to receive a plurality of user signals from the user node.

64. The system of claim 63 wherein the plurality of user signals comprise light signals.

The system of claim 63 wherein the plurality of output signals comprises a substantially same information content at the input signal.

66. An apparatus, comprising: an amplifier having an input port to receive an input signal and operable to divide the input signal into a plurality of output signals; a plurality of transmitters to transmit the plurality of output signals; and a plurality of receivers associated with respective plurality of transmitters to receive user signals.

67. The apparatus of claim 66 wherein the output signals and user signals comprise light signals. P:\OPER\ArI\l 2430060 div.doc.29/03/04 52

68. The apparatus of claim 66 wherein the plurality of output signals comprise a substantially same information content as the input signal.

69. A method of transmitting and receiving, the method comprising: dividing an input signal into a plurality of output signals; transmitting the plurality of output signals to a plurality of corresponding receivers of a user node; and receiving a plurality of user signals transmitted from the user node light signals.

70. The method of claim 69 wherein transmitting the plurality of output signals comprises transmitting light signals.

71. The method of claim 69, further comprising providing each of the plurality of output signals with a substantially same information content as the input signal.

72. A communication system, substantially as described with reference to the drawings and/or Examples.

73. A method, substantially as described with reference to the drawings and/or Examples.

74. An apparatus, substantially as described with reference to the drawings and/or Examples. Dated this 2 9 th day of March 2004 Terabeam Corporation by DAVIES COLLISON CAVE Patent Attorneys for the applicant(s)