Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1993-03-02
1994-12-13
Chilcot, Jr.
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359181, 359182, 356345, H04B 1000
Patent
active
053733835
ABSTRACT:
A method and apparatus for improving the signal-to-noise ratio (SNR) and dynamic range of an optical fiber system. An optical fiber system (10) includes a laser(12) that produces a coherent light signal conveyed over an optical fiber (14) to a Mach-Zehnder modulator (16). An input signal modulates the coherent light, producing modulated side bands, which together with the carrier comprise a modulated light signal. The modulated light signal is filtered using an integrated optical filter (24) that substantially attenuates the carrier frequency, while passing light at the frequency of the modulated side bands. A detector (28) demodulates the filtered light with a substantially greater SNR than would otherwise have been possible. In one preferred form of the invention, the integrated optical filter comprises an imbalanced interferometer (40), and in another embodiment, tile interferometer produces imperfect nulls aligned with the carrier frequency. A relatively higher power laser(12) can be used without damage to detector (28), since the integrated optical filter substantially reduces the average power of the modulated light by attenuating the carrier, thereby enhancing SNR and dynamic range of the system.
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Chilcot Jr.
Negash Kinfe-Michael
The Boeing Company
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