Coherent optical detection and signal processing method and system
OwnerMichael George Taylorinventor
Life of this patent
Estimating the term…
Abstract
A method and system of coherent detection of optical signals. The system utilizes a digital signal processor to recover an incoming optical signal. The system employs a local oscillator, which does not need to be phase locked to the signal. The signal may be consistently recovered, even when the polarization state varies over time. Additionally, the signal may be recovered when it comprises two channels of the same wavelength that are polarization multiplexed together. In addition, any impairment to the signal may be reversed or eliminated.
Claims20
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.
A method of receiving an incoming optical signal in a coherent optical detection system, said method comprising the steps of:
- emitting light from a local oscillator, said local oscillator not requiring a phase lock with the incoming optical signal;
- generating at least four copies of the incoming optical signal and four copies of the local oscillator light by an optical mixing hybrid;
- combining, by the optical mixing hybrid, the copies of the incoming optical signal and the copies of the local oscillator light into at least four outputs, wherein four outputs of the at least four outputs of the optical mixing hybrid may be selected such that the Jones vector of the optical signal relative to the local oscillator light at each of the four selected outputs is distinct from the Jones vector of the optical signal relative to the local oscillator light at the other three of the selected outputs;
- receiving optical signals from the four outputs by four photodetectors in communication with the optical mixing hybrid;
- digitizing electrical signals, by four A/D converters, from the four photodetectors;
- and
- performing computations, by a digital signal processor, 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.
Dependencies are inferred from the claim text.