Cascaded RZ and NRZ laser modulators having RZ/NRZ phase alignment bias control
US6917455B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 25, 2003 |
| Grant date | Jul 12, 2005 |
| Priority date | — |
| Expiry date | Jul 12, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B10/5162
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An optical transmitter architecture has a return-to-zero (RZ) laser modulator coupled in cascade with a non-return-to-zero (NRZ) laser modulator. Modulator bias and electronic phase delay bias are controlled using dither-based feedback, so as to align the phase of the RZ clock signal with that of the NRZ data. A first method uses an RZ quadrature AM dither or an RZ “hillclimber” bias dither, to apply a relatively low frequency dither signal to a variable RF delay for the RZ clock signal applied to the RZ modulator or NRZ data signal applied to the NRZ modulator. A second method is an RZ quadrature AM dither or “hillclimber” bias dither scheme that applies equal amplitude and opposite phase dither signals to perform complementary modulation of both the RZ and NRZ MZ modulators simultaneously.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.