Apparatus for linearization of optic modulators using a feed-forward predistortion circuit
AssigneeUnited Technologies Corporation
InventorsJames D. Farina, Gregory J. McBrien
Life of this patent
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Abstract
A feed-forward predistortion circuit to provide improved linear response in optic modulators. The circuit includes a non-linear element, an amplifier/delay means and a power combiner. The non-linear element generates a first signal sin(X), where (X) is the input signal. The amplifier/delay means generates a second signal 2(X). The first and second signals are combined in the power combiner to produce a modulating signal 2(X)-sin(X) which is fed to an optic modulator. The modulating signal 2(X)-sin(X) compensates for the transfer function of the optic modulator which has a transfer function sin(X), thereby producing a linear output.
Claims26
A predistortion circuit for linearizing an optic modulator, said predistortion circuit being operative in response to an input signal (X), comprising:
- means for providing a first signal(X);
- means for providing a second signal 2(X);
- and
- means for combining said first and second signals to provide a modulating signal 2(X)-sin(X), such that the optic modulator receiving said modulating signal generates a linear output signal(X).
A circuit for modulating an optic signal, said circuit being operative in response to an input signal(X), comprising:
- means for providing a first signal having a waveform sin(X);
- means for providing a second signal having a waveform 2(X);
- means for combining said first and second signals to provide a modulating signal having a waveform 2(X)-sin(X);
- and
- means for modulating the optic signal with said modulating signal, said means for modulating having a transfer function sin(X), such that the optic signal is modulated to produce a linear output signal(X).
An optical modulating system having a linearized transfer function comprising:
- an optical modulator for receiving a light source input and a modulating input for modulating said light source input, said optical modulator comprising a non-linear transfer function;
- and
- a predistortion system for linearizing said non-linear transfer function of said optical modulator, said predistortion system comprising:
- a non-linear element for receiving an input signal(X) and for responding with an output signal H(X), said input signal(X) having a signal power;
- means for providing an output signal (A*X) in response to said input signal(X).
- means for combining said output signal H(X) of said non-linear element with said output signal (A*X), said means for combining generating an output signal, (A*X)-H(X), having a signal power;
- and
- means for matching said signal power of said input signal (X) with said signal power of said output signal, (A*X)-H(X), of said means for combining such that said signal power are substantially equal, said means for matching generating an output signal received by said optical modulator as said modulating input, thereby linearizing said non-linear transfer function of said optical modulator.
Dependencies are inferred from the claim text.