Method and apparatus for generating 8-QAM-modulated optical signal
AssigneeAT&T Intellectual Property I, L.P.
InventorsXiang Zhou, Peter Magill
Life of this patent
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Abstract
A system and method for producing an 8-QAM-modulated signal are disclosed. The methodology, in an exemplary expedient, generally comprises splitting light from a CW laser into two parts; modulating the first part with a first signal and modulating the second part with a second signal; phase shifting the modulated second part by about π/4; combining the modulated first part with the phase shifted and modulated second part to produce a four-level modulated signal; and phase modulating the four-level modulated signal with a third signal with a phase modulation of (0, π/2). Several variations of this method are described herein.
Claims24
An apparatus, comprising:
- a first coupler that receives light and splits the light into a first part and a second part;
- a first modulator that modulates the first part with a first signal to produce a modulated first part and a second modulator that modulates the second part with a second signal to produce a modulated second part;
- a phase shifter that shifts a phase of the modulated second part by π/4 to produce a phase shifted modulated second part;
- a second coupler that combines the modulated first part with the phase shifted modulated second part to produce a four-level modulated signal;
- and
- a phase modulator that further modulates the four-level modulated signal with a third signal with a phase modulation of (0, π/2) to produce an 8-quadrature amplitude modulation signal.
An apparatus, comprising:
- a phase modulator that receives light and modulates the light with a first signal with a phase modulation of (0, π/2) to produce a modulated light;
- a first coupler that receives the modulated light and splits the modulated light into a first part and a second part;
- a first modulator that modulates the first part with a second signal to produce a modulated first part and a second modulator that modulates the second part with a third signal to produce a modulated second part;
- a phase shifter that shifts a phase of the modulated second part by π/4 to produce a phase shifted modulated second part;
- and
- a second coupler that combines the modulated first part with the phase shifted modulated second part to produce an 8-quadrature amplitude modulation signal.
A method for producing an 8-quadrature amplitude modulation signal, comprising:
- splitting light into a first part and a second part;
- modulating the first part with a first signal to produce a modulated first part and modulating the second part with a second signal to produce a modulated second part;
- phase shifting the modulated second part by π/4 to produce a phase shifted modulated second part;
- combining the modulated first part with the phase shifted modulated second part to produce a four-level modulated signal;
- and
- phase modulating the four-level modulated signal with a third signal with a phase modulation of (0, π/2).
A method for producing an 8-quadrature amplitude modulation signal, comprising:
- phase modulating light with a first signal with a phase modulation of (0, π/2) to produce the phase modulated light;
- splitting the phase modulated light into a first part and a second part;
- modulating the first part with a second signal to produce a modulated first part and modulating the second part with a third signal to produce a modulated second part;
- phase shifting the modulated second part by π/4 to produce a phase shifted modulated second part;
- and
- combining the modulated first part with the phase shifted modulated second part.
Dependencies are inferred from the claim text.