Patent ID: 7599630
Filing Date: 2009-10-06
Classification: H04B

Abstract:
1. A coherent optical detection system receiving an incoming optical signal in a fiber optics network, said system comprising: a local oscillator emitting light; an optical mixing hybrid for generating at least four optical waves similar to the incoming optical signal and four optical waves similar to the local oscillator light, said optical mixing hybrid combining the optical waves similar to the incoming optical signal and the optical waves similar to the local oscillator light into at least four outputs, wherein said local oscillator does not have to be phase locked to the incoming optical signal; wherein each of the outputs of the optical mixing hybrid has a specific Jones vector associated with the output, such that the beat product between the optical wave similar to the optical signal and the optical wave similar to the local oscillator light is the same as the beat product that would be observed by mixing the original incoming optical signal with local oscillator light having the Jones vector, and wherein four outputs of the at least four outputs of the optical mixing hybrid may be selected such that the Jones vector associated with each of the four selected outputs is distinct from the Jones vectors associated with the other three selected outputs; four photodetectors communicating with the optical mixing hybrid, wherein said four photodetectors receive optical signals from the four outputs; four A/D converters to receive electrical signals from the four photodetectors, said four A/D converters digitizing the received electrical signals; and a digital signal processor for performing computations on digital values from the four A/D converters to obtain information carried by the incoming optical signal without limitation to the state of polarization of the incoming optical signal.