Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1995-01-17
1997-03-25
Chin, Wellington
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359173, 359245, H04B 1004, H04B 1012
Patent
active
056150377
ABSTRACT:
An electro-optical modulation device comprises a first Mach-Zehnder interferometric modulator. This modulator has balanced optical power in each arm to intensity modulate an optical carrier signal in response to an information signal. The invention also includes a second Mach-Zehnder interferometric modulator that is in a cascade connection with the first modulator and also has balanced optical power in each arm. This second modulator receives the optical carrier signal from the first modulator and also intensity modulates the optical carrier signal in response to the information signal. In another embodiment, the electro-optical modulation device comprises an electro-optical modulator, for intensity modulating an optical carrier in response to an electrical signal, and a reflective termination. The termination reflects the intensity modulated optical carrier signal to travel back through the electro-optical modulator. As a result, the modulation effect of the modulator is effectively doubled. Either embodiment is useful for applications that involve bandwidths of less than one octave, for which the embodiments can be easily optimized. The best examples are links for remote antennas, the most notable exception being cable television. For these sub-octave-bandpass links, second-order distortion does not present a problem since these spurious signals fall outside the band of interest. As a result, the second-order distortion control constraint can be sacrificed in an effort to negate third-order distortion and remediate other problems. This trade-off is not available in broadband cable applications.
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Betts Gary
O'Donnell Frederick
Ray Kevin
Chin Wellington
Massachusetts Institute of Technology
Negash Kinfe-Michael
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