Fiber optical transmission system, transmitter and receiver for DQPSK modulated signals and method for stabilizing the same
US8041228B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 19, 2006 |
| Grant date | Oct 18, 2011 |
| Priority date | — |
| Expiry date | May 8, 2028 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B10/66
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A transmitter (3) for generating a DQPSK-modulated optical signal, including: a splitter (7) for dividing an optical carrier signal into a first and second branch (8a, 8b), a first and second Mach-Zehnder interferometer (9, 10) in the first and second branch (8a, 8b), respectively, a phase shifter (11) in one of the branches (8b) generating a nominal phase shift of .pi./2, and a combiner (7′) for combining the optical output signals of the two branches (8a, 8b). The transmitter (3) has a feedback circuit (12) generating at least a first and second bias signal (15.1 to 15.3) for adjusting a bias of at least the first and second Mach-Zehnder interferometers (9, 10), the feedback circuit (12) includes a detector for generating at least a first and second feedback signal from a sample signal extracted from the optical signal after the combiner (7′), and for each bias signal: a local oscillator generating an auxiliary signal modulating the bias signal (15.1 to 15.3) at a pre-defined frequency (f1, f2, f3), a lock-in detector determining a phase difference between the feedback signal and the auxiliary signal, and a bias circuit for generating the bias signal (15.1 to 15.3) from an output…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.