Method and system for optical heterodyne detection of an optical signal

A system for optical heterodyne detection comprising:

• means for measuring a fraction of an input signal before said input signal is combined with a local oscillator signal and for generating a first electrical signal that is representative of said measured fraction of said input signal;
• means for measuring a fraction of said local oscillator signal before said local oscillator signal is combined with said input signal and for generating a second electrical signal that is representative of said measured fraction of said local oscillator signal;
• an optical coupler having a first input and a second input, said first input being optically connected to receive said input signal, said second input being optically connected to receive said local oscillator signal, said optical coupler having an output for outputting a combined optical signal that includes said input signal and said local oscillator signal;
• a heterodyne receiver having an input for receiving said combined optical signal from said optical coupler and an output for outputting a third electrical signal that is representative of said combined optical signal, said third electrical signal including a heterodyne signal;
• and
• a processor for receiving said first electrical signal, said second electrical signal, and said third electrical signal, and for generating an output signal that is indicative of an optical parameter of said input signal in response to said heterodyne signal and said first electrical signal.

A method for monitoring an optical signal utilizing optical heterodyne detection, comprising steps of:

• providing a first optical signal;
• providing a second optical signal, one of said first and second optical signals being a local oscillator signal and the other signal being an input signal;
• measuring a fraction of said first optical signal before said first optical signal is combined with said second optical signal;
• generating a first electrical signal that is representative of said measured fraction of said first optical signal;
• combining said first optical signal with said second optical signal to create a combined optical signal;
• generating a third electrical signal that is representative of said combined optical signal;
• and
• generating an output signal that is indicative of an optical parameter of said input signal, said step of generating said output signal including a step of utilizing said first electrical signal to reduce signal noise in said third electrical signal, wherein said signal noise is contributed from said first optical signal.