Methods to control phase shifts of delay demodulation devices

Details Methods to control phase shifts of delay demodulation devices Methods to control phase shifts of delay demodulation devices

2009-03-27

2010-10-12

Sanghavi, Hemang (Department: 2874)

Optical: systems and elements

Optical demodulator

C385S001000, C385S011000

Reexamination Certificate

active

07813032

ABSTRACT:
The present invention provides methods to control phase shift of delay demodulation devices to reduce Polarization Dependent wavelength (PDλ) to be less than, for example, 0.5 GHz (i.e. 0.004 nm). The method to control phase shift in a Planar Lightwave Circuit (PLC) for demodulating Differential Quadrature Phase Shift Keying (DQPSK) comprising two Mach-Zehnder interferometers, each having two arm waveguides and heaters placed on the two arm waveguides, the method comprising the steps of: (first step) supplying electricity to at least one predetermined heater on the two arm waveguides of each Mach-Zehnder interferometer such that Polarization Dependent wavelength (PDλ) is reduced as electricity is supplied to the predetermined heaters; (second step) inserting a half-wave plate in the two arm waveguides of each Mach-Zehnder interferometer after PDλ is reduced in the first step; (third step) supplying electricity to the predetermined heater on the at least one of the two Mach-Zehnder interferometers used in the first step to control phases of the DQPSK signals after the half-wave plates are inserted.

REFERENCES:
patent: 6546161 (2003-04-01), Okuno et al.
patent: 7480091 (2009-01-01), Hasegawa et al.
patent: 2005/0058398 (2005-03-01), Doerr
patent: 2007-60442 (2007-03-01), None

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