Optical I-Q-modulator
AssigneeNokia Siemens Networks Oy
InventorWinter Marcus
Life of this patent
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Abstract
The invention describes a modulator for the quadrature modulation of an optical carrier signal with an I- and a Q-portion, where a first optical multimode interferometer (MMI) splits the optical carrier signal into four branches and that in pairs of branches the I-portion and the Q-portion respectively is modulated with a Mach-Zehnder-Structure and a second optical multimode interferometer (MMI) combines the modulated I-portion and Q-portion again to one quadrature modulated optical output signal (OS).
Claims10
A modulator for quadrature modulation of an optical carrier signal with an I-portion and a Q-portion, the modulator comprising:
- a first optical multimode interferometer configured to split the optical carrier signal into four branches carrying intermediate signals, some of the branches containing fixed phase shifters in order to obtain pairwise Mach-Zehnder-structures with a mutual phase shift of a quarter wavelength, and modulators for separately modulating pairs of branches carrying the I-portion and the Q-portion respectively, to form a modulated I-portion and a modulated Q-portion, respectively;
- and
- a second optical multimode interferometer configured to combine the modulated I-portion and the modulated Q-portion to one quadrature modulated optical output signal.
A method for quadrature-modulating an optical carrier signal with an I-portion and a Q-portion, the method which comprises:
- splitting the optical carrier signal with an optical multimode interferometer into four branches carrying intermediate signals;
- providing some branches with fixed phase shifters to obtain therefrom pairwise Mach-Zehnder-structures with a mutual phase shift of a quarter wavelength, and modulating pairs of branches carrying the I-portion and the Q-portion respectively separately with modulators;
- and
- combining the modulated I-portion and Q-portion with a second optical multimode interferometer to one quadrature modulated optical output signal.
Dependencies are inferred from the claim text.