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US 4,904,963 AGranted
Staggered quadrature phase shift keyed laser modulator
AssigneeMcDonnell Douglas Corporation
InventorJeffrey R. Heidel
Life of this patent
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Abstract
A staggered quadrature phase shift keyed modulator which avoids the need for timing circuits. Three phase modulators serially change the phase of a laser beam so that it may sequentially have a total phase shift of .pi., .pi./2, 0, -.pi./2. The input signal is divided into two pulse trains, one of which is delayed to provide the stagger. The two pulse trains are logically combined to form three control signals for the modulators.
Claims9
An optical modulator having an electronic signal input and an optical output comprising:
- a shift register receiving said input and producing a first output and a second output;
- a delay line connected to said first output to produce a delayed output;
- logic means connected to said delayed output said second output for producing a plurality of control signals;
- a plurality of optical phase modulators, each controlled by one of said control signals, which change the phase of light traveling therethrough;
- a light source producing a light beam which serially passes through each of said phase modulators to produce a phase shifted optical output.
2 more elements
Dependencies are inferred from the claim text.