US 5,221,983 A · Passive photonic loop architecture employing wavelength multiplexing

Abstract

A fiber optic subscriber loop architecture is disclosed. The architecture utilizes a double star configuration comprising a Central Office and a plurality of Remote Nodes. Illustratively, in the Central Office, one bank of N lasers supplies wavelengths .lambda..sub.1, .lambda..sub.2 . . . .lambda..sub.N in a first wavelength band to form channels on which downstream information will be transmitted to subscribers. In one embodiment, a second bank of N lasers operating at wavelengths .lambda..sup.N+1, .lambda..sub.N+2 . . . .lambda..sub.2N in a second wavelength band is used to form unmodulated channels to be delivered to subscribers for use in subsequent upstream transmissions. Groups of N wavelength channels are combined via WDM techniques at the Central Office before being transmitted over feeder fibers to the Remote Nodes. In the downstream direction, the Remote Nodes rearrange the wavelength channels received from the Central Office so as to route two wavelength channels, one modulated channel from the first wavelength band and one unmodulated channel from the second wavelength band, to each of a plurality of subscriber premises attached thereto. At each subscriber station, the modulated channel is decoded while the unmodulated channel is modulated with upstream information and transmitted back to the associated Remote Node. Each Remote Node multiplexes groups of the modulated channels from the second wavelength band and routes them back to the Central Office over the feeder fibers. In the above-described double-star subscriber loop architecture, there are no active devices in the Remote Nodes.

Claims8

Dependent claims

A double-star fiber optic subscriber loop architecture comprising:

a central office,
a plurality of passive, all optical remote nodes connected to the central office, and
a plurality of subscriber premises connected to each remote node,
said central office comprising means for generating a plurality of modulated wavelength channels in a first wavelength band, means for generating a plurality of unmodulated wavelength channels in a second wavelength band, and wavelength division multiplexing means for forming multiplexed signals each comprising a group of modulated or unmodulated channels from said first or second wavelength bands, respectively, to be transmitted to said remote nodes, wherein said plurality of wavelength channels in said first wavelength band is generated by a first bank of lasers, a power splitter associated with each laser in the first bank, and an external modulator associated with each output of each power splitter,
each said passive remote nodes including means for receiving a plurality of said multiplexed signals from said central office and optical means for passively processing said received multiplexed signals in optical form so that each subscriber premises receives one modulated channel from said first wavelength band and one unmodulated channel from said second wavelength.

2 more elements

A double-star fiber optic subscriber loop architecture comprising

a central office,
a plurality of passive, all-optical remote nodes connected to the central office, and
a plurality of subscriber premises connected to each passive remote node,
said central office comprising means for generating a plurality of modulated wavelength channels in a first wavelength band, means for generating a plurality of unmodulated wavelength channels in a second wavelength band, and wavelength division multiplexing means for forming multiplexed signals each comprising a group of modulated or unmodulated channels from said first or second wavelength band, respectively, to be transmitted to one of said passive remote nodes, said plurality of modulated wavelength channels in said first wavelength band being generated by a first bank of lasers, a power splitter associated with each laser in the first bank, and an external modulator associated with each output of each power splitter,
each of said passive, all-optical remote nodes comprising
a WDM comprising
a first group of WDM devices for demultiplexing a plurality of multiplexed signals in a first wavelength band and a second wavelength band received from said central office into a plurality of individual channels in said first wavelength band and said second wavelength band, respectively, for distribution to said individual subscriber premises,
a second group of WDM devices for multiplexing a plurality of individual modulated channels from individual subscriber premises in a second wavelength band into a plurality of multiplexed signals in said second wavelength band, and
a third group of WDM devices for multiplexing/demultiplexing said multiplexed signals in said first and second wavelength bands, and
optical means for transmitting a modulated channel in said first and second wavelength bands to each of said subscriber premises and for receiving a modulated channel in said second wavelength band from each of said subscriber.

7 more elements

Dependencies are inferred from the claim text.

Passive photonic loop architecture employing wavelength multiplexing

Life of this patent

Passive photonic loop architecture employing wavelength multiplexing

Life of this patent

Abstract

Claims8