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An optical coherent receiver in one embodiment has a heterodyne configuration, and in another embodiment has a homodyne configuration, in each configuration employs multiple feedback signaling and analog/digital processing to optimize response to a modulated optical input signal, the provision of bo

An optical coherent receiver in one embodiment has a heterodyne configuration, and in another embodiment has a homodyne configuration, in each configuration employs multiple feedback signaling and analog/digital processing to optimize response to a modulated optical input signal, the provision of both individual RF I and RF Q channel outputs.

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What is claimed is: 1. An optical coherent receiver comprising: a series connected subsystem successively including an input signal processor driving an optical coupler, the latter driving a post coupler optical processor, the latter driving a balanced optical-to-electrical (OE) converter, the latt

What is claimed is: 1. An optical coherent receiver comprising: a series connected subsystem successively including an input signal processor driving an optical coupler, the latter driving a post coupler optical processor, the latter driving a balanced optical-to-electrical (OE) converter, the latter driving an RF processor, the latter driving a baseband RF/EDC (Electronic Dispersion Compensation/Equalization) processor, the latter providing an RF output signal from said receiver; a first closed loop subsystem including a peak detector connected between said RF processor and said post coupler optical processor; a second closed loop subsystem including a frequency and phase lock network (FPL) driven by said RF processor, an optical local oscillator (LO) driven by the said FPL, and an optical LO processor driven by said optical LO, said optical LO processor driving said optical coupler; a third closed loop subsystem including said RF processor driving an autoscan, the latter driving said optical LO; said input signal processor being operative for receiving and processing a modulated optical input signal to provide a stable polarized optical output signal Esig; said optical coupler being independently receptive of Esig, and an optical reference signal ELO, for providing a plurality of output signals each of which are a combination of Esig and ELO, and each of which are phase shifted from one another; said post coupler optical processor being independently receptive of said plurality of output signals from said optical coupler, respectively, for both processing these signals via included fiber stretching means for equalizing the path lengths thereof and providing the same as a plurality of path length equalized optical output signals, and for providing an optically derived RF feedback signal to said optical coupler for causing the ratios between any two of the plurality of output signals therefrom to be of a given value; said balanced optical-to-electrical (OE) converter being receptive of said plurality of path length equalized optical output signals, for converting these signals into at least one RF output signal; said RF processor being receptive of said at least one RF output signal for providing a first RF feedback signal that is peak detected via said peak detector to drive said fiber stretching means of said post coupler optical processor to maintain the equalization of said plurality of path length equalized optical signals, for further providing a second RF feedback signal to said autoscan for driving the latter to produce an output signal therefrom for temperature correcting said optical LO, for further providing a third RF feedback signal to drive said frequency and phase lock module to control the phase and frequency of said optical LO, whereby the phase of the latter is locked to the phase of said optical input signal, and for providing a baseband output signal; said baseband RF/EDC processor being receptive of said baseband output signal for processing the same to compensate for both noise and transmission impairments of this signal, and for producing the RF output signal of said receiver; said peak detector being receptive of an RF signal from said RF processor, for providing a control output signal representative of the peak of the RF output signal, for controlling said post coupler optical processor to insure optimal coupling ratio; said FPL being receptive of an RF error signal from said RF processor, for providing a drive output signal for controlling said optical LO to align its frequency/phase to the modulated input signal; said optical LO being operative to produce an optical output signal for driving said optical LO processor to produce said ELO reference signal; and said autoscan being receptive of a filtered IF signal from said RF processor for detecting, tracking, and locking onto said optical input signal. 2. The optical coherent receiver of claim 1, wherein said first balanced OE converter consists of at least one pair of avalanche photodiodes. 3. The optical coherent receiver of claim 1, wherein said input signal processor includes means for optically isolating Esig. 4. The optical coherent receiver of claim 1, wherein said input signal processor includes means for amplifying and filtering Esig. 5. The optical coherent receiver of claim 3, wherein said input signal processor further includes means for amplifying and filtering Esig. 6. The optical coherent receiver of claim 1, wherein said input signal processor is operative for optically isolating, amplifying, filtering, and polarizing said input signal to provide Esig. 7. The optical coherent receiver of claim 2, wherein said RF processor is further operative to provide a fourth RF feedback signal to drive said balanced OE converter to control the responsivity of said balanced OE converter. 8. The optical coherent receiver of claim 1, wherein said RF processor includes means for configuring said receiver as a superheterodyne receiver. 9. The optical coherent receiver of claim 1, wherein said RF processor includes means for configuring said receiver as a homodyne receiver. 10. The optical coherent receiver of claim 8, wherein said optical coupler consists of a variable ratio optical coupler. 11. The optical coherent receiver of claim 9, wherein said optical coupler consists of a variable ratio 90�� optical hybrid. 12. The optical coherent receiver of claim 8, wherein said post coupler optical processor includes: a first optical tap receptive of a first output signal from said variable ratio optical coupler, for splitting the signal into a 99% first feed forward signal, and a first 1% feedback signal; a second optical tap receptive of a second output signal from said variable ratio optical coupler, for splitting the signal into a 99% second feed forward signal, and a second 1% feedback signal; a fiber stretcher receptive of said first feed forward signal, for processing this signal to provide optical path equalizer between said first and second feed forward signals, and producing a fiber stretched feed forward signal; an optical differential comparator receptive of said first and second 1% feedback signals, for producing an electrical direct current (DC) output signal having a voltage level representative of the difference in amplitude between said feedback signals; and said variable ratio optical coupler being receptive of said DC output signal from said differential comparator to insure a 50/50 coupling ratio for the first and second output signals of the coupler. 13. The optical coherent receiver of claim 1, wherein said balanced OE converter includes a pair of positively and negatively biased avalanche photodiodes, respectively, individually receptive of said path length equalized optical output signals, respectively, for producing said at least one RF output signal. 14. The optical coherent receiver of claim 12, wherein said balanced OE converter includes positively and negatively biased first and second avalanche photodiodes (APD), respectively, for receiving said fiber stretched feed forward signal, and said 99% second feed forward signal, for producing said at least one RF output signal. 15. The optical coherent receiver of claim 13, wherein said RF processor includes: a broadband bias tee receptive of said one RF output signal, for both producing a DC feedback signal to said first APD to provide AC responsivity balancing between said first and second APD's, and for providing a feed forward RF output signal analogous to said at least one RF output signal; an impedance-matched broadband RF amplifier receptive of said feed forward RF output signal from said bias tee, for providing an amplified RF output signal to said peak detector; a bandpass filter receptive of said amplified RF output signal, for producing an intermediate frequency (IF) beat note signal; an IF detect module receptive of said IF beat note signal for producing an IF RF output signal; a first double balanced mixer receptive individually of both said amplified RF output signal, and said IF beat note signal, for mixing these signals together to produce a first mixer output signal; a first low-pass filter (LPF) receptive of said first mixer output signal, for producing a first LPF output signal; a 90% delay module receptive of said IF beat note signal, for outputting a delayed beat note signal; a second double balanced mixer receptive individually of both said amplified RF output signal, and said delayed beat note signal for producing a second mixer output signal; a second low-pass filter (LPF) receptive of said second mixer output signal, for producing a second LPF output signal; a first sample-and-hold RF module receptive of said first LPF output signal, operable for time delaying this signal, to produce on demand a first sampled RF output signal; a first decision block receptive of said first LPF output signal, operable for digitizing this signal to provide a first decision block output signal; a second decision block receptive of said second LPF output signal, operable for digitizing this signal to provide a second decision block output signal; a second sample-and hold RF module receptive of said second LPF output signal, operable for time delaying this signal to produce on demand a second sampled RF output signal; a first multiplier receptive of both said first sampled RF output signal, and said second decision block output signal, for multiplying the two signals to produce a first multiplier output signal; a second multiplier receptive of both said second sampled RF output signal, and said first decision block output signal, for multiplying the two signals to produce a second multiplier output signal; a subtraction module receptive of said first and second multiplier output signals, for producing said RF error signal representative of the difference between these signals; and said first and second LPF output signals in combination being representative of said baseband output signal. 16. The optical coherent receiver of claim 1, wherein said balanced OE converter includes a positively and a negatively biased first and second photodiodes, respectively, individually receptive of said path length equalized optical output signals, respectively, for producing said at least one RF output signal. 17. The optical coherent receiver of claim 15, further including: a photocurrent monitor loop for driving the voltage of the negatively biased second APD for optimal operation; and a temperature control loop for maintaining high precision temperature stability of said first and second APD's. 18. The optical coherent receiver of claim 16, wherein said RF processor includes: a broadband bias tee receptive of said one RF output signal, for both producing a DC feedback signal to said first photodiode to provide AC responsivity balancing between said first and second photodiodes, and for providing a feed forward RF output signal analogous to said at least one RF output signal; an impedance-matched broadband RF amplifier receptive of said feed forward RF output signal from said bias tee, for providing an amplified RF output signal to said peak detector; a bandpass filter receptive of said amplified RF output signal, for producing an intermediate frequency (IF) beat note signal; an IF detect module receptive of said IF beat note signal for producing an IF RF output signal; a first double balanced mixer receptive individually of both said amplified RF output signal, and said IF beat note signal, for mixing these signals together to produce a first mixer output signal; a first low-pass filter (LPF) receptive of said first mixer output signal, for producing a first LPF output signal; a 90% delay module receptive of said IF beat note signal, for outputting a delayed beat note signal; a second double balanced mixer receptive individually of both said amplified RF output signal, and said delayed beat note signal for producing a second mixer output signal; a second low-pass filter (LPF) receptive of said second mixer output signal, for producing a second LPF output signal; a first sample-and-hold RF module receptive of said first LPF output signal, operable for time delaying this signal, to produce on demand a first sampled RF output signal; a first decision block receptive of said first LPF output signal, operable for digitizing this signal to provide a first decision block output signal; a second decision block receptive of said second LPF output signal, operable for digitizing this signal to provide a second decision block output signal; a second sample-and hold RF module receptive of said second LPF output signal, operable for time delaying this signal to produce on demand a second sampled RF output signal; a first multiplier receptive of both said first sampled RF output signal, and said second decision block output signal, for multiplying the two signals to produce a first multiplier output signal; a second multiplier receptive of both said second sampled RF output signal, and said first decision block output signal, for multiplying the two signals to produce a second multiplier output signal; a subtraction module receptive of said first and second multiplier output signals, for producing said RF error signal representative of the difference between these signals; and said first and second LPF output signals in combination being representative of said baseband output signal. 19. The optical coherent receiver of claim 11, wherein said post coupler optical processor includes: first through fourth optical taps receptive of first through fourth optical output signals from said optical coupler, respectively, for both producing first through fourth output signals, respectively, each of which are 99% the level of their associated received signal, and for producing first through fourth feedback signals, respectively, each of which are 1% the level of their associated received signal; a peak detector receptive of said second 99% output signal, and a feedback signal from said RF processor; first and second fiber stretchers receptive of said first and third 99% output signals, said second fiber stretcher being further receptive of an output signal from said peak detector, said first and second fiber stretchers being operative to equalize the optical path lengths of said first and second 99% output signals, and said third and fourth 99% output signals, respectively; a first optical differential comparator receptive of said first and second 1% feedback signals, respectively, for producing an output signal that is fed back to said optical coupler; and a second optical differential comparator receptive of said third and fourth 1% feedback signals, respectively, for producing an output signal that is fed back to said optical coupler; said first fiber stretcher, second optical tap, second fiber stretcher, and fourth optical tap, providing first through fourth output signals from said post coupler optical processor. 20. The optical coherent receiver of claim 19, wherein said balanced OE converter includes: a first pair of photodiodes, each of which are positively and negatively biased, respectively, receptive of said first and second output signals from said post coupler optical processor, for converting these signals from optical into a first RF (radio frequency) output signal; and a second pair of photodiodes, each of which are positively and negatively biased, respectively, receptive of said third and fourth output signals from said post coupler optical processor, for converting these signals from optical into a second RF output signal. 21. The optical coherent receiver of claim 20, wherein said RF processor includes: first and second bias tees individually receptive of said first and second RF output signals, respectively, from said balanced OE converter, for both providing bias voltages back to said first and second pair of photodiodes, respectively, and passing through said first and second RF output signals; first and second amplifiers receptive of said first and second RF output signals from said first and second bias tees, respectively, for providing third and fourth RF output signals; first and second peak detectors receptive of said third and fourth RF output signals for providing feedback signals to said first and second fiber stretchers, respectively; first and second time delay modules receptive of said third and fourth RF output signals, for producing fifth and sixth RF output signals representing time delayed third and fourth RF output signals, respectively; first and second analog-to-digital (A/D) converters receptive of said third and fourth RF output signals, respectively, for converting these signals into first and second digitized RF output signals, respectively; a first multiplier receptive of said fifth RF output signal, and said second digitized RF output signal, for producing a seventh RF output signal that is the product of the previous two signals; a second multiplier receptive of and for multiplying together said sixth RF output signal and first digitized RF output signal, to produce an eighth RF output signal; an RF subtraction module receptive of said seventh and eighth RF output signals, for producing said error signal to drive said FPL; and said third and fourth RF output signals also being provided for driving said baseband RF/EDC processor, and said autoscan, respectively. 22. The optical coherent receiver of claim 21, wherein said baseband RF/EDC processor includes: a first differential decoder receptive of said third RF output signal, for producing a first decoded signal; a first low-pass filter receptive of said first decoded signal, for producing an RF I channel output signal; a second differential decoder receptive of said fourth RF output signal, for producing a second decoded signal; and a second low-pass filter receptive of said second decoded signal, for producing an RF Q channel output signal. 23. The optical coherent receiver of claim 21, wherein said first and second pairs of photodiodes each consists of positively and negatively biased avalanche photodiodes, respectively. 24. The optical coherent receiver of claim 23, further including: a temperature control loop for maintaining high precision temperature stability of said first and second APD's; and a photocurrent monitor loop for driving the voltage of the negatively biased second APD for optimal operation. 25. The optical coherent receiver of claim 15, wherein said baseband RF/EDC processor includes: a first differential decoder receptive of said first LPF output signal, for producing a first decoded signal, providing an RF I channel output signal; and a second differential decoder receptive of said second LPF output signal for producing a second decoded signal, providing an RF Q channel output signal. 26. The optical coherent receiver of claim 18, wherein said baseband RF/EDC processor includes: a first differential decoder receptive of said first LPF output signal, for producing a first decoded signal, providing an RF I channel output signal; and a second differential decoder receptive of said second LPF output signal for producing a second decoded signal, providing an RF Q channel output signal. 27. The optical coherent receiver of claim 15, further including: said FPL being receptive of said error signal; said optical LO consisting of a tuneable local oscillator (LO) laser receptive of output signals from both said FPL and said autoscan, for locking the frequency and phase of an optical output signal from said TLO to that of a modulated optical input signal inputted to said input signal processor; said optical LO processor including: an optical isolator receptive of the optical output signal from said TLO, for providing an optically isolated output signal; an amplifier receptive of said optically isolated output signal; an ASE filter receptive of an optical output signal from said amplifier; and a polarization stabilizer receptive of an output signal from said ASE filter, for providing a polarization stabilized optical output signal to drive said optical coupler. 28. The optical coherent receiver of claim 18, further including: said FPL being receptive of said error signal; said optical LO consisting of a tuneable local oscillator (LO) laser receptive of output signals from both said FPL and said autoscan, for locking the frequency and phase of an optical output signal from said TLO to that of a modulated optical input signal inputted to said input signal processor; said optical LO processor including: an optical isolator receptive of the optical output signal from said TLO, for providing an optically isolated output signal; an amplifier receptive of said optically isolated output signal; an ASE filter receptive of an optical output signal from said amplifier; and a polarization stabilizer receptive of an output signal from said ASE filter, for providing a polarization stabilized optical output signal to drive said optical coupler. 29. The optical coherent receiver of claim 1, wherein said input signal processor includes: an optical isolator receptive of said modulated optical input signal, for providing an optically isolated modulated optical output signal; an amplifier receptive of said optical output signal, for modifying this signal; an optical bandpass filter (BPF) receptive of and for filtering out out-of-band optical noise from an output signal from said amplifier; and a polarization stabilizer receptive of a filtered output signal from said BPF, for providing said stable polarized optical output signal Esig.