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An optical receiver adapted to apply multiple-sampling processing to an intermediate frequency (IF) signal generated based on heterodyne detection of an optical communication signal. In one embodiment, the receiver has an optical-to-electrical signal converter coupled to a signal decoder adapted to

An optical receiver adapted to apply multiple-sampling processing to an intermediate frequency (IF) signal generated based on heterodyne detection of an optical communication signal. In one embodiment, the receiver has an optical-to-electrical signal converter coupled to a signal decoder adapted to process the IF signal generated by the converter to generate a bit sequence corresponding to the optical communication signal. To generate a bit value, the signal decoder first obtains two or more sample-bit values by sampling the IF signal two or more times per signaling interval. The decoder then applies a logical function to the sample-bit values, which produces the corresponding bit value for the bit sequence. Due to the multiple-sampling processing, a receiver of the invention does not require the time-consuming fine wavelength tuning of its local oscillator, which advantageously reduces the channel switching time achieved in the receiver compared to that in prior-art heterodyne receivers.

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What is claimed is: 1. A method of signal processing, comprising: (A) converting a first optical signal into an electrical signal having an intermediate frequency and an amplitude corresponding to optical power of the first optical signal; (B) sampling the electrical signal two or more times per si

What is claimed is: 1. A method of signal processing, comprising: (A) converting a first optical signal into an electrical signal having an intermediate frequency and an amplitude corresponding to optical power of the first optical signal; (B) sampling the electrical signal two or more times per signaling interval to generate two or more signal samples, wherein there is a relative time delay between first and second signal samples of the two or more signal samples; (C) comparing each of the first and second signal samples with a decision threshold value to generate first and second sample-bit values; and (D) applying a logical function to the first and second sample-bit values to generate a bit sequence corresponding to the optical signal, wherein: the first optical signal has a first wavelength; step (A) comprises mixing the first optical signal with a second optical signal having a second wavelength, wherein the intermediate frequency corresponds to wavelength difference between the first and second wavelengths; and for a signaling interval corresponding to an optical "1", the relative time delay and the wavelength difference cause at least one of the first and second signal samples to be greater than the decision threshold value. 2. The method of claim 1, wherein the second optical signal is generated by an optical source without receiving feedback from a signal decoder that implements steps (A) through (D). 3. The method of claim 1, wherein the relative time delay between the first and second signal samples and a relative time delay between the second signal sample and a third signal sample are substantially equal. 4. The method of claim 3, wherein each relative time delay corresponds to a phase shift at the intermediate frequency of about 120 degrees. 5. The method of claim 1, wherein the relative time delay between the first and second signal samples corresponds to a phase shift at the intermediate frequency of about 90 degrees. 6. The method of claim 1, wherein: the first optical signal is WDM signal, wherein the first wavelength corresponds to a WDM channel; and the second optical signal is a continuous wave signal. 7. The method of claim 1, wherein: step (C) comprises: comparing the first signal sample with a first decision threshold value to generate the first sample-bit value; comparing the second signal sample with a second decision threshold value to generate the second sample-bit value; and step (D) comprises: inverting the second sample-bit value. 8. The method of claim 1, wherein step (D) comprises applying an "OR" function to the two or more sample-bit values to generate a bit of the bit sequence. 9. The method of claim 1, wherein the first optical signal is an intensity-modulated signal. 10. The method of claim 1, comprising: sampling the electrical signal four times per signaling interval to generate four sample-bit values; and utilizing three of the four sample-bit values in further signal processing while discarding the remaining one sample-bit value. 11. An optical receiver, comprising: a signal converter adapted to convert a first optical signal into an electrical signal having an intermediate frequency and an amplitude corresponding to optical power of the first optical signal; and a signal decoder coupled to the signal converter and adapted to: (i) sample the electrical signal two or more times per signaling interval to generate two or more signal samples, wherein there is a relative time delay between first and second signal samples of the two or more signal samples; and (ii) compare each of the first and second signal samples with a decision threshold value to generate first and second sample-bit values; and (iii) apply a logical function to the first and second sample-bit values to generate a bit sequence corresponding to the optical signal, wherein: the first optical signal has a first wavelength; the signal converter is adapted to mix the first optical signal with a second optical signal having a second wavelength, wherein the intermediate frequency corresponds to wavelength difference between the first and second wavelengths; and for a signaling interval corresponding to an optical "1", the relative time delay and the wavelength difference cause at least one of the first and second signal samples to be greater than the decision threshold value. 12. The receiver of claim 11, wherein the signal converter comprises: a local oscillator adapted to generate the second optical signal; an optical coupler adapted to mix the first optical signal with the second optical signal to generate third and fourth optical signals; and a pair of photo-detectors coupled to a differential amplifier, wherein the third and fourth optical signals are converted into the electrical signal having the intermediate frequency. 13. The receiver of claim 12, wherein the local oscillator is adapted to generate the second optical signal without receiving feedback from the signal decoder. 14. The receiver of claim 12, wherein: the first optical signal is WDM signal, wherein the first wavelength corresponds to a WDM channel; and the second optical signal is a continuous wave signal. 15. The receiver of claim 11, wherein the relative time delay corresponds to a phase shift at the intermediate frequency of about 120 degrees. 16. The receiver of claim 11, wherein the relative time delay corresponds to a phase shift at the intermediate frequency of about 90 degrees. 17. The receiver of claim 11, wherein the signal decoder comprises: a decision circuit coupled to the signal converter and adapted to sample the electrical signal two or more times per signaling interval to generate two or more sample-bit values; a de-multiplexer having an input port and two or more output ports, wherein: the input port is coupled to the decision circuit; each of output ports is adapted to receive a different bit corresponding to the samples of the electrical signal; and a logic gate coupled to the output ports and adapted to apply the logical function to the two or more sample-bit values to generate a bit of the bit sequence. 18. The receiver of claim 17, wherein: the decision circuit is adapted to sample the electrical signal four times per signaling interval to generate three sample-bit values and one unutilized bit; the de-multiplexer has four output ports, wherein: three of the output ports are adapted to receive the three sample-bit values; and the remaining output port is adapted to receive the unutilized bit; and the logic gate is an "OR" gate coupled to the three output ports and adapted to apply an "OR" function to the three sample-bit values. 19. The receiver of claim 11, wherein the signal decoder comprises: at least first and second decision circuits, each coupled to the signal convener and adapted to sample the electrical signal at least one time per signaling interval, wherein: the first decision circuit is adapted to generate the first sample-bit value; the second decision circuit is adapted to generate the second sample-bit value; and the first and second decision circuits sample the electrical signal with the relative time delay; and an inverter coupled to the second decision circuit and adapted to invert the second sample-bit value. 20. The receiver of claim 19, wherein the signal decoder comprises an "OR" gate coupled to the first decision circuit and the inverter and adapted to apply an "OR" function to the first sample-bit value and the inverted second sample-bit value to generate a bit of the bit sequence. 21. The receiver of claim 19, wherein each decision circuit is adapted to compare a sample of the electrical signal with a respective decision threshold value to generate an output-bit value. 22. The receiver of claim 21, wherein: the first decision circuit is adapted to compare the first signal sample a first decision threshold value to generate the first sample-bit value; and the second decision circuit is adapted to compare the second signal sample with a second decision threshold value different from the first decision threshold value to generate the second sample-bit value. 23. An optical communication system, comprising an optical receiver adapted to receive a first optical signal via a communication link, wherein the optical receiver comprises: a signal converter adapted to convert the first optical signal into an electrical signal having an intermediate frequency and an amplitude corresponding to optical power of the first optical signal; and a signal decoder coupled to the signal converter and adapted to: (i) sample the electrical signal two or more times per signaling interval to generate two or more signal samples, wherein there is a relative time delay between first and second signal samples of the two or more signal samples; and (ii) compare each of the first and second signal samples with a decision threshold value to generate first and second sample-bit values; and (iii) apply a logical function to the first and second sample-bit values to generate a bit sequence corresponding to the optical signal, wherein: the first optical signal has a first wavelength; the signal converter is adapted to mix the first optical signal with a second optical signal having a second wavelength, wherein the intermediate frequency corresponds to wavelength difference between the first and second wavelengths; and for a signaling interval corresponding to an optical "1", the relative time delay and the wavelength difference cause at least one of the first and second signal samples to be greater than the decision threshold value. 24. The system of claim 23, wherein the signal converter comprises: a local oscillator adapted to generate the second optical signal; an optical coupler adapted to mix the first optical signal with the second optical signal to generate third and fourth optical signals; and a pair of photo-detectors coupled to a differential amplifier, wherein the third and fourth optical signals are convened into the electrical signal having the intermediate frequency. 25. The system of claim 24, wherein the local oscillator is adapted to generate the second optical signal without receiving feedback from the signal decoder.