Granted Patent B2

US 7,558,487 · App. 11/162,830 · Granted Jul 7, 2009

Abstract

Claims (26)

1. A method for generating multilevel amplitude and phase encoded optical signals comprising the steps of:

generating, a Differential Quaternary/Quadrature Phase Shift Keying (DQPSK) optical signal;

splitting, the DQPSK optical signal into a number of optical signals, wherein each one of the number of optical signals exhibits a different optical power;

modulating, at least one of the number of optical signals through the effect of a zero-biased, Mach-Zehnder Modulator configured for phase modulation; and

combining, each one of the optical signals into a single DQPSK-PAM2 N signal.

2. The method of claim 1 , wherein the splitting step comprises the steps of:

distributing, the optical signals into N+1 output arms of an optical splitter having a respective power splitting distribution of (0.4+2 N−1 ), (2 N−2 ), (2 N−3 ), . . . , (1), (0.5).

3. The method of claim 1 , further comprising the step of:

selectively adjusting, the optical phase of the optical signals prior to their combining.

4. The method of claim 1 , further comprising the step of:

modulating, the MZM with a signal tributary.

5. The method of claim 4 wherein the phase of the optical signal is modulated by an amount approximately equal to π.

6. The method of claim 1 , wherein the combining step comprises the steps of:

receiving, the optical signals from N+1 output arms of an optical splitter having a respective power splitting distribution of (0.4+2 N+1 ), (2 N−2 ), (2 N−3 ), . . . , (1), (0.5) through the effect of an optical combiner.

7. A method for generating multilevel amplitude and phase encoded optical signals comprising the steps of:

generating an optical signal;

splitting, the optical signal into a number of optical signals, wherein each one of the number of optical signals exhibits a different optical power;

modulating, at least one of the number of optical signals through the effect of a zero-biased, Mach-Zehnder Modulator; and

combining, each one of the optical signals into a single QAM2N signal.

8. The method of claim 7 wherein said splitting step splits the optical signal into N optical signals, wherein each one of the N optical signals exhibits a different optical power and each one of the N optical signals is associated with an in-phase tributary (I) or a quadrature (Q) tributary.

9. The method of claim 8 further comprising the step(s) of:

applying, a phase offset of substantially π/2 to those signals associated with a quadrature (Q) tributary, with respect to those signals associated with an in-phase tributary.

10. The method of claim 7 wherein said modulating step comprises the step(s) of:

applying, a tributary signal to the zero-biased, Mach-Zehnder Modulator.

11. The method of claim 7 further comprising the steps of:

formatting, the QAM2N signals with return-to-zero pulse formatting.

Assignments (12)