A differential quadrature phase shift keyed system includes a fiber optic source and a first fiber optic differential phase shift keyed demodulator coupled to the fiber optic source having a first phase differential. A second fiber optic differential phase shift keyed demodulator is coupled to the fiber optic source disposed parallel with the first fiber optic differential phase shift key demodulator. The second demodulator has a second phase shift differential equal to the first phase differential plus about 90 degrees.