Optical waveguides – Temporal optical modulation within an optical waveguide
Reexamination Certificate
2001-02-23
2002-12-31
Healey, Brian (Department: 2874)
Optical waveguides
Temporal optical modulation within an optical waveguide
C385S002000, C385S014000, C385S015000, C385S024000, C359S199200, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06501866
ABSTRACT:
FIELD
The field of interest is optical networks, and more specifically, optical switching fabrics.
BACKGROUND
An optical switching cross-connect comprises equipment that switches or routes information received from one or more fiber optic media input lines, and transmits the information out through one or more fiber optic media output lines. The connecting of input lines to output lines through the optical cross-connect can occur in any combination or permutation.
FIG. 1
shows a general optical cross-connect
100
with an electrical switching fabric. In this prior art embodiment, each incoming line
102
is fed into the demultiplexer section
104
wherein a demultiplexer
106
separates the multiple wavelengths on each incoming line. In a central portion
108
optical-to-electrical translation of incoming optical signals is accomplished, followed by the switching, which is accomplished electrically. The electrical switching fabric output is then converted via electrical-to-optical translation to optical signals. Finally, each multiplexer
112
in the multiplexer section
110
places several wavelengths onto an output optical transmission line
114
.
FIG. 2
(prior art) shows a conventional electrical-to-optical (EO) conversion
200
. Each input line
202
, typically carrying an optical signal comprising information on a single wavelength carrier, is connected to an optical receiver
204
, which translates the optical signals received on the input line into electrical signals. An electrical switching fabric
206
routes each electrical signal to its intended output line
208
. The electrical signal output from the electrical switching fabric
206
is then fed to an optical transmitter
210
, where the electrical signal modulates an optical laser carrier beam generated by a laser within the optical transmitter. The output of the optical transmitter
210
is fed into an optical transmission line
212
, which is typically a fiber optic cable.
FIG. 3
(prior art) shows a typical optical laser transmitter module
300
, the module comprising a Continuous Wave (CW) fixed International Telecommunications Union (ITU) grid wavelength laser
302
, and an external modulator
304
that modulates the laser carrier beam with information from an Electrical Data Input
306
, which data has come from the electrical switching fabric
206
(see FIG.
2
). A tap
312
diverts some of the light energy emitted from the laser to a wavelength locker
314
, which provides feedback to control circuitry
316
that serves to maintain a specific wavelength of the ITU grid wavelength laser
302
. Monitoring circuitry
318
monitors the wavelength and power of the ITU grid wavelength laser
302
.
As seen in
FIG. 2
, prior art EO conversion employs one optical transmitter
210
for each output line coming from the electrical switching fabric
206
. Prior art further depicted in
FIG. 3
shows that each optical transmitter contains at least one laser that supplies the optical carrier to be modulated by the external modulator
304
, which is then output to an Optical Data Output
310
.
Optical cross-connect architecture comprises both optical and electrical switching fabrics. Electrical switching fabrics require optical-to-electrical (OE) conversion circuitry and electrical-to-optical (EO) conversion circuitry. In designing electrical switching fabrics, EO conversion circuitry is the predominant cost factor. Reducing costs of EO conversion circuitry would have a major impact on overall cost of an electrical switching fabric-based optical cross-connect installation. The set of lasers providing output carrier beams to the output modulators is a major expenditure in EO conversion. A reduction in the total number of lasers needed to produce all output channels would result in a significant cost saving.
SUMMARY
Method and apparatus is provided for supplying output carrier optical signals to output modulators through the use of a reduced number of lasers that comprise a shared laser bank. The total number of lasers employed is less than the total number of optical modulators being supplied with optical carriers.
REFERENCES:
patent: 5894362 (1999-04-01), Onaka et al.
patent: 6233075 (2001-05-01), Chang et al.
patent: 6301037 (2001-10-01), Fischer et al.
patent: 6301402 (2001-10-01), Bhalla et al.
Blakely Sokoloff Taylor & Zafman LLP.
Healey Brian
Mahi Networks. Inc.
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