Optical waveguides – With optical coupler – Plural
Reexamination Certificate
1998-05-14
2001-07-10
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Plural
C385S003000, C385S027000, C359S199200, C359S199200, C359S326000
Reexamination Certificate
active
06259836
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to optical frequency shifters and their applications.
BACKGROUND OF THE INVENTION
It is desirable to have exactly spaced carrier frequencies for optical transmission systems. This invention provides for such exactly spaced carrier frequencies. It is also desirable to frequency shift previously modulated optical signals for the purpose of switching and retransmission.
SUMMARY OF THE INVENTION
The first object is a frequency shifter. It is a second object of the invention to create optical carrier signals spread at intervals of exactly &ohgr;
m
where &ohgr;
m
is a microwave frequency in the order of 5-50 GHz.
According to an aspect of the invention, there is provided an optical transmission system, comprising an input light guide and N frequency shifters connected to receive light from the input light guide and output light along N output light guides where N is 1 or more, wherein the light carried by each ith output light guide, where i=1, . . . , N, is translated in frequency from light entering the input light guide by i&ohgr;
m
, and where each frequency shifter contributes a frequency translation of &ohgr;
m
.
Each of the N output light guides may be equipped with a modulator to impress an information signal on each output light guide. When the modulated outputs, each of different wavelength, are combined, the result is a wavelength division multiplexed optical signal.
In a further aspect of the invention, the optical transmission system is equipped with a cascade of N frequency shifters at the receiver to generate frequencies &ohgr;
0
+i&ohgr;
m
which may be used for self-homodyne square law direct detection of the information signals.
In a further aspect of the invention, there is provided an optical frequency shifter for translating an input optical frequency by a given amount, which may be used for wavelength placement on outgoing fibers in an optical switch in a wavelength division multiplexing system.
These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.
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Bovernick Rodney
Christensen O'Connor Johnson & Kindness PLLC
Stahl Michael J
Telecommunications Research Laboratories
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