Dynamic measurement of and compensation for impairments to optical data communication pulses using photon-counting silicon avalanche photodiode

Apparatus for detecting characteristics of an input optical signal comprising

• a photon-counting avalanche Photo Diode, APD, for detecting at least two-photon absorption, TPA, of the optical signal, the optical signal having a wavelength range extending from 1.2 μm to an upper wavelength region that increases as the number of photons simultaneously absorbed by the APD increases beyond two,
• apparatus capable of quantifying the TPA response,
• means for determining a characteristic of the optical signal using the detected TPA response,
• wherein the characteristic being detected is a signal impairment of the optical signal and the detected TPA count is indicative of the signal impairment of the optical signal, and
• wherein the optical signal is optical pulse communication signal and the signal impairment of the optical pulse communication signal being detected is selected from a group including a signal-to-noise ratio, a group velocity dispersion, and a polarization mode dispersion.

Apparatus for detecting characteristics of an input optical signal comprising

• a photon-counting avalanche Photo Diode, APD, for detecting at least two-photon absorption, TPA, of the optical signal, the optical signal having a wavelength range extending from 1.2 μm to an upper wavelength region that increases as the number of photons simultaneously absorbed by the APD increases beyond two,
• apparatus capable of quantifying the TPA response,
• means for determining a characteristic of the optical signal using the detected TPA response, and
• wherein the optical signal is optical pulse communication signal and the characteristic being detected is a pulse width of the optical pulse communication signal and the TPA rate of the APD is indicative of the narrowness of the optical pulse communication signal.

Apparatus for detecting characteristics of an input optical signal comprising

• a photon-counting avalanche Photo Diode, APD, for detecting at least two-photon absorption, TPA, of the optical signal, the optical signal having a wavelength range extending from 1.2 μm to an upper wavelength region that, increases as the number of photons simultaneously absorbed by the APD increases beyond two,
• apparatus capable of quantifying the TPA response,
• means for determining a characteristic of the optical signal using the detected TPA response, and
• wherein the detector apparatus is part of apparatus for real-time compensation of group velocity dispersion, GVD, and wherein the received optical signal is an optical pulse communication signal, the compensation apparatus further including
• a tunable dispersion compensator for receiving the optical pulse communication signal, for providing a variable dispersion to the received optical pulse communication signal in response to a control signal, and for outputting a restored optical pulse communication signal;
• a signal sampling device for sampling a predetermined portion of the restored optical pulse communication signal;
• said detector apparatus detecting and counting the detected TPA rate of the restored optical pulse communication signal and for outputting a TPA count rate signal;
• a control unit responsive to the TPA count rate signal for generating the control signal to the tunable dispersion compensator.

Apparatus for detecting characteristics of an input optical signal comprising

• a photon-counting avalanche Photo Diode, APD, for detecting at least two-photon absorption, TPA, of the optical signal, the optical signal having a wavelength range extending from 1.2 μm to an upper wavelength region that increases as the number of photons simultaneously absorbed by the APD increases beyond two,
• apparatus capable of quantifying the TPA response,
• means for determining a characteristic of the optical signal using the detected TPA response, and
• wherein the detector apparatus is part of apparatus for real-time compensation of polarization mode dispersion, PMD, and wherein the received optical signal is an optical pulse communication signal, the compensation apparatus further including
• a PMD compensator for receiving the optical pulse communication signal, for providing a variable PMD compensation to the received optical pulse communication signal in response to a control signal, and for outputting a restored optical pulse communication signal;
• a signal sampling device for sampling a predetermined portion of the restored optical pulse communication signal;
• said detector apparatus detecting and counting the TPA rate of the restored optical pulse communication signal and for outputting a TPA count rate signal;
• a control unit responsive to the count rate signal for generating the control signal to the PMD compensator.

Apparatus for detecting characteristics of an input optical signal comprising

• a photon-counting avalanche Photo Diode, APD, for detecting at least two-photon absorption, TPA, of the optical signal, the optical signal having a wavelength range extending from 1.2 μm to an upper wavelength region that increases as the number of photons simultaneously absorbed by the APD increases beyond two,
• apparatus capable of quantifying the TPA response,
• means for determining a characteristic of the optical signal using the detected TPA response, and
• wherein the detector apparatus is part of a signal compensation apparatus for real-time compensation of a received optical signal which is an optical pulse communication signal, the compensation apparatus further including
• a first dispersion compensator for receiving a first optical pulse communication signal, for providing a variable dispersion to the received first optical pulse communication signal in response to a first control signal, and for outputting a second optical pulse communication signal;
• a second dispersion compensator for receiving a second optical pulse communication signal, for providing a variable dispersion to the received second optical pulse communication signal in response to a second control signal, and for outputting a restored optical pulse communication signal;
• a signal tap device for sampling a predetermined portion of the restored optical pulse communication signal;
• said detector apparatus detecting and counting the TPA rate of the restored optical pulse communication signal and for outputting a TPA count rate signal;
• a first control unit responsive to the TPA count rate signal for generating the first control signal to the first dispersion compensator during a first time interval;
• a second control unit responsive to the TPA count rate signal for generating the second control signal to the second dispersion compensator during a second time interval;
• wherein the first dispersion compensator is selected from a group including a polarization mode dispersion, PMD, compensator and group velocity dispersion, GVD, compensator;
• and
• wherein when the first dispersion compensator is selected to be the PMD compensator, the second dispersion compensator is selected to be the GVD compensator and vice-versa.

Apparatus for detecting characteristics of an input optical signal comprising

• a photon-counting avalanche Photo Diode, APD, for detecting at least two-photon absorption, TPA, of the optical signal, the optical signal having a wavelength range extending from 1.2 μm to an upper wavelength region that increases as the number of photons simultaneously absorbed by the APD increases beyond two,
• apparatus capable of quantifying the TPA response,
• means for determining a characteristic of the optical signal using the detected TPA response, and
• wherein the detector apparatus is part of an autocorrelation or cross correlation apparatus for determining the autocorrelation or cross correlation between two optical signals which are optical pulse signals, the autocorrelation apparatus further including
• means for producing a first and second optical pulse signals from the optical pulse communication signal, the second optical pulse signal having a controllable delay, relative to the first optical pulse signal, which is varied at a predetermined periodic rate;
• said detector apparatus detecting and counting the detected TPA rate of the combined first and second optical pulse signals and for outputting a TPA count rate signal;
• wherein said characteristic determining means is responsive to the TPA count rate signal for determining the autocorrelation between the first and second optical pulse signals as a function of the relative delay between the first and second optical pulse signals.

Apparatus for detecting characteristics of an input optical signal comprising

• a photon-counting avalanche Photo Diode, APD, for detecting at least two-photon absorption, TPA, of the optical signal, the optical signal having a wavelength range extending from 1.2 μm to an upper wavelength region that increases as the number of photons simultaneously absorbed by the APD increases beyond two,
• apparatus capable of quantifying the TPA response,
• means for determining a characteristic of the optical signal using the detected TPA response, and
• wherein the detector apparatus is part of apparatus for synchronizing a second optical pulse signal to a first optical pulse signal, the synchronizing apparatus further including
• input means for receiving the first optical pulse signal;
• variable delay circuit responsive to an delay adjustment signal for delaying a received second optical pulse signal by an amount determined by the delay adjustment signal to generate a delayed second optical pulse signal;
• combiner for combining the first and second optical pulse signals into a combined optical signal;
• said detector apparatus detecting and counting the TPA rate of the combined optical signal and for outputting a TPA count rate signal;
• wherein said characteristic determining means is responsive to the TPA count rate signal and the first optical pulse signal for generating a delay adjustment signal which when applied to the variable delay circuit results in a delayed second optical pulse signal which is in synchronization with the first optical pulse signal.