Optical/radio local access network

• US 6,788,898 B1
• Filed: 08/17/2000
• Issued: 09/07/2004
• Est. Priority Date: 04/14/2000
• Status: Expired due to Fees

• Current Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Lin, Lih-Yuan, Miller, Robert R., Britz, David M., Dodley, Jeevan Prakash
• Primary Examiner(s): NEGASH, KINFE MICHAEL
• Application Number:
  US09/641,083
• Time in Patent Office: 1,482 Days
• Field of Search: 398/70, 398/83, 398/115-116, 398/118.45, 398/127.48, 379/56.2
• US Class Current: 398/70
• CPC Class Codes: H04B 10/1125 using a single common optical path

Abstract

A communication system includes a plurality of nodes and a plurality of point-to-point links that interconnect the plurality of nodes into a network. Each node includes an optical switch to controllably route a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch. Each point-to-point link includes a free space optical channel. A first free space optical channel couples to a first node through a receive path and through a transmit path. The receive path couples to a respective in-port of the optical switch of the first node, and the transmit path couples to a respective out-port of the optical switch of the first node. In an alternative embodiment, a communication hub includes a plurality of neighborhood links to corresponding users, an optical switch coupled to the plurality of neighborhood links, and a trunk coupled between the optical switch and a free space optical channel link to the network. A method of communicating in a network having plural links includes sensing the presence of a received signal failure by monitoring channel losses in a first link, the received signal failure resulting from at least one of rain and fog. The method further includes sending data in a free space optical channel of the first link when the received signal failure sensed is due to rain and sending the data in an RF channel of the first link when the received signal failure sensed is due to fog.

Claims

1. A communication system comprising:

a plurality of nodes, each node including an optical switch to controllably route signals from a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch; and

a plurality of point-to-point links that interconnect the plurality of nodes into a network, each point-to-point link including a free space optical channel, a first free space optical channel coupling to a first node through a receive path and through a transmit path, the receive path coupling to a respective in-port of the optical switch of the first node, the transmit path coupling to a respective out-port of the optical switch of the first node, wherein each point-to-point link further includes a radio channel that complements the respective free space optical channel.

2. The communication system of claim 1, wherein:

the radio channel propagates better than the free space optical channel through fog; and

the free space optical channel propagates better than the radio channel through rain.

3. A communication system comprising:

a plurality of nodes, each node including an optical switch to controllably route signals from a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch; and

a plurality of point-to-point links that interconnect the plurality of nodes into a network, each point-to-point link including a free space optical channel, a first free space optical channel coupling to a first node through a receive path and through a transmit path, the receive path coupling to a respective in-port of the optical switch of the first node, the transmit path coupling to a respective out-port of the optical switch of the first node, wherein the first node includes an electrical add drop multiplexer.

4. A communication system comprising:

a plurality of nodes, each node including an optical switch to controllably route signals from a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch; and

a plurality of point-to-point links that interconnect the plurality of nodes into a network, each point-to-point link including a free space optical channel, a first free space optical channel coupling to a first node through a receive path and through a transmit path, the receive path coupling to a respective in-port of the optical switch of the first node, the transmit path coupling to a respective out-port of the optical switch of the first node, wherein the first node includes an optical add/drop multiplexer.

5. A communication system comprising:

a plurality of nodes, each node including an optical switch to controllably route signals from a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch;

a plurality of point-to-point links that interconnect the plurality of nodes into a network, each point-to-point link including a free space optical channel, a first free space optical channel coupling to a first node through a receive path and through a transmit path, the receive path coupling to a respective in-port of the optical switch of the first node, the transmit path coupling to a respective out-port of the optical switch of the first node; and

an outdoor unit that includes an optical telescope.

6. The communication system of claim 5, wherein a second node includes the outdoor unit, the outdoor unit of the second node including at least one gimbal and corresponding servo controller.

7. A communication system comprising:

a plurality of nodes, each node including an optical switch to controllably route signals from a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch; and

a plurality of point-to-point links that interconnect the plurality of nodes into a network, each point-to-point link including a free space optical channel, a first free space optical channel coupling to a first node through a receive path and through a transmit path, the receive path coupling to a respective in-port of the optical switch of the first node, the transmit path coupling to a respective out-port of the optical switch of the first node, wherein each of the plurality of point-to-point links including a dedicated data field to provide 911 service.

8. A method of communicating in a network having plural links, comprising the steps of:

sensing the presence of a received signal failure by monitoring channel losses in a first link, the received signal failure resulting from at least one of rain and fog;

sending data in a free space optical channel of the first link when a received signal failure is sensed due to rain; and

sending a message in an RF channel of the first link when a received signal failure is sensed due to fog.

9. The method of claim 8, further comprising a step of routing the data over the plural links by sending routing commands over a mobile radio system.

10. The method of claim 9, wherein:

the step of sensing determines that the first link is unavailable when the channel losses sensed for both the RF channel and the free space optical channel are greater than a predetermined loss; and

the step of routing routes the message around the first link when the step of sensing determines that the first link is unavailable.