Network with shared optical sources

Details Network with shared optical sources Network with shared optical sources

2001-04-24

2004-08-24

Negash, Kinfe-Michael (Department: 2633)

Optical communications

Multiplex

Wavelength division or frequency division

C398S082000, C398S083000, C385S024000

Reexamination Certificate

active

06782204

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to the field of optical networks.
BACKGROUND OF THE INVENTION
Optical networks typically utilize a plurality of optical sources, typically lasers, to generate optical carriers which are typically modulated with information at a transmitting station, transmitted on one or more optical waveguides (typically optical fiber), and subsequently demodulated at a receiving station. Two or more optical carriers of differing wavelengths &lgr;
i
are typically multiplexed onto an optical waveguide, transmitted along the optical waveguide, and de-multiplexed at another location, at which location one or more modulated optical carriers is demodulated and the information delivered to its destination.
FIG. 1
(prior art) is a block diagram of a ring Optical Add/Drop Multiplexed (OADM) network
100
, comprising a plurality of add/drop nodes
102
.
FIG. 2
(prior art) is a block diagram of a linear Optical Add/Drop Multiplexed (OADM) network
200
, comprising a plurality of add/drop nodes
202
. A typical add/drop node
300
is depicted in
FIG. 3
(prior art).
A multiplexed input signal
302
comprising a plurality of modulated respective optical carriers (also referred to as wavelengths herein) each carrier comprising a substantially single respective wavelength &lgr;
i
, i.e., a substantially pure single wavelength beam, passes through an optical amplifier
304
, and into a separating device
306
, typically a de-multiplexing device, that separates the “through” wavelengths
308
from the “drop” wavelengths
310
. The drop wavelengths
310
are directed to a device
312
where they are de-multiplexed, and each wavelength is output onto an optical waveguide
314
, which waveguide is typically optical fiber. Each of the drop wavelengths
310
is demodulated in a respective receiver
316
, the respective receiver
316
then passing the information as a result of demodulation, on to its respective destination. The information received at receiver
316
is also, in parallel fashion, channeled to an input
322
(labeled Add signal #
1
) of a modulator
320
, where the information modulates a new beam originating from a source
318
whose wavelength is typically identical to the carrier of the respective drop wavelength (in this case, &lgr;
1
). Each information channel to be modulated typically requires a separate laser source, as typically a laser source emits a single carrier wavelength. Laser sources used in optical networks tend to be costly items; therefore it would be advantageous to reduce the number of sources, e.g.,
318
, typically lasers, needed to operate the add/drop node
300
.
FIG. 9
is a block diagram of a Passive Optical Network (PON), comprising a Host Digital Terminal (HDT)
902
, which in turn typically comprises a plurality of Host Digital Terminal Passive Optical Network Terminal Modules (HPTM)
904
, and typically a plurality of Optical Network Units (ONU)
906
. Typically each of the Optical Network Units (ONU)
906
comprises an optical source, typically a laser, which, in the ONU's transmit mode, generates a carrier wavelength &lgr;
i
that is modulated in the ONU before being output. As indicated above, optical sources, typically lasers, used in optical networks tend to be costly items; if it were possible to eliminate the necessity for each ONU to comprise an optical source, the result would be advantageous, in that there would be a reduction in the overall number of optical sources required in order to operate the PON.
SUMMARY OF THE INVENTION
Methods and apparatuses are contemplated for sharing optical sources in an optical network, which typically reduces the number of optical sources needed to operate the optical network.


REFERENCES:
patent: 6084694 (2000-07-01), Milton et al.
patent: 6115158 (2000-09-01), Kaneko
patent: 6233077 (2001-05-01), Alexander et al.

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