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Subcarrier Encoded Wavelength Division Multiplexed Network With Full Connectivity

IP.com Disclosure Number: IPCOM000121069D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 127K

Publishing Venue

IBM

Related People

Choy, MM: AUTHOR [+2]

Abstract

The combination of wavelength division multiplexing (WDM), microwave subcarrier multiplexing (SCM) [1], and fiber technology offers an unique capability of optical linking of a few hundred channels in a metropolitan-area computer network or local-area network. In particular, in a computer network environment, a large number of stations with full connectivity is desirable. Although a purely optical dense wavelength division network of up to 600 stations can, in principle, be built, difficulties, such as cost and components availability, along with interchannel crosstalk, laser mode partition, and frequency chirping, renders simple implementation somewhat difficult. The 600- channel system could be achieved by a two-layer structure of 30 wavelength division optical channels, each with 20 RF multiplexed sub carrier channels.

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Subcarrier Encoded Wavelength Division Multiplexed Network With Full
Connectivity

      The combination of wavelength division multiplexing
(WDM), microwave subcarrier multiplexing (SCM) [1], and fiber
technology offers an unique capability of optical linking of a few
hundred channels in a metropolitan-area computer network or
local-area network.  In particular, in a computer network
environment, a large number of stations with full connectivity is
desirable.  Although a purely optical dense wavelength division
network of up to 600 stations can, in principle, be built,
difficulties, such as cost and components availability, along with
interchannel crosstalk, laser mode partition, and frequency chirping,
renders simple implementation somewhat difficult.  The 600- channel
system could be achieved by a two-layer structure of 30 wavelength
division optical channels, each with 20 RF multiplexed sub carrier
channels.  The full connectivity could be achieved by sequentially
optically demultiplexing followed by RF heterodyning with local
oscillator and mixer combination. The full connectivity of a large
number of users necessitates the use of fiber amplifier to satisfy
the power margin requirements.

      The proposed network system consists of N optical and M RF
channels, each RF channel transmitting at B Mb/s using FSK
modulation.  The proposed architecture is depicted in Fig. 1.  On the
transmitting side, as shown in Fig. 2a, the digital data from M
stations are converted to frequency shift-keyed signal.   Individual
carrier frequency, which is set by the voltage controlled oscillator,
is distributed within the modulation bandwidth of the laser diode.
The number of RF channels supported by the modulation bandwidth
depends on the modulation speed.  The spacing between the neighboring
channels is about 2 times the modulation speed. Modulation bandwidth
of commercial InP semiconductor lasers are available to up to 2 GHz.
The data are then combined with a RF power combiner before being
launched into the laser diode.  The laser output is distributed by
the N x N optical star coupler with fiber separation from the coupler
to the stations of up to 30 Km.  At the receiver end, as shown in
Fig. 2b, a 1 x M power sp...