Optics: measuring and testing – By polarized light examination
Reexamination Certificate
2005-12-06
2005-12-06
Toatley, Jr., Gregory J. (Department: 2877)
Optics: measuring and testing
By polarized light examination
C356S365000, C398S184000, C398S186000
Reexamination Certificate
active
06972842
ABSTRACT:
Timing alignment between a pulse carver (i.e., intensity modulator) and a phase modulator, e.g., in a return-to-zero (RZ) differential phase-shift keying (DPSK) optical transmitter, is monitored by filtering a signal from the transmitter and measuring the power of the filtered signal. In certain embodiments, the filter has a birefringent device (such as a polarization-maintaining fiber) and a polarizer. The polarizer may be a rotating polarizer with a rotating quarter-wave plate in front of it. In other embodiments, the filter is a periodic filter such as a Mach-Zehnder interferometer or an etalon filter. Regardless, the measured power may be used to generate control signals used to variably delay the signals that drive the phase modulator and/or the pulse carver to compensate for detected misalignment. The measured power may also be used to monitor the bit-error-rate degradation caused by timing misalignment between the pulse carver and the phase modulator.
REFERENCES:
patent: 5850305 (1998-12-01), Pidgeon
patent: 6201632 (2001-03-01), Rollins
patent: 6452714 (2002-09-01), Rollins
patent: 2005/0002675 (2005-01-01), Sardesai et al.
Doerr Christopher R.
Kim Hoon
Lucent Technologies - Inc.
Punnoose Roy M.
Toatley , Jr. Gregory J.
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