Abstract: The present patent application provides a vertical cavity surface emitting laser assembly. The vertical cavity surface emitting laser assembly includes a vertical cavity surface emitting laser, optical element and optical detector. The optical element includes an identation. A portion of the output light of the VCSEL passes through the indentation and to the optical detector to be used for power monitoring.

Abstract: The present patent application provides a vertical cavity surface emitting laser assembly. The vertical cavity surface emitting laser assembly includes a vertical cavity surface emitting laser, optical element and optical detector. The optical element includes an identation. A portion of the output light of the VCSEL passes through the indentation and to the optical detector to be used for power monitoring.

Abstract: Methods and circuits for providing a minimum driving voltage to a current-driven load (such as a laser diode) are disclosed. The circuit and methods may be useful for efficiently providing a bias and/or driving current to the current-driven load with minimal energy loss. The circuit generally comprises (1) a driver or voltage source configured to provide the bias and/or driving current to the current-driven load, (2) a sense circuit configured to (i) sense the bias and/or driving current and (ii) convert the bias and/or driving current to a first voltage, and (3) a comparator configured to (i) receive the first voltage and first and second reference voltages and (ii) provide a feedback/error signal to the driver or voltage source, the feedback/error signal configured to maintain or adjust the bias and/or driving current at or towards a target value.

Abstract: Methods for receiving a signal and a detection circuit are disclosed. The detection circuit and related methods may be useful for the fast and accurate receiving of data signals. The detection circuit generally comprises a first circuit having a first time constant, a second circuit having (i) a common input with the first circuit and (ii) a second time constant, the second time constant being less than the first time constant, and a switch configured to (i) charge the first circuit with an input signal when the switch is in a first state, and (ii) charge or discharge the second circuit with the input signal when the switch is in a second state, the switch having the second state when the input signal is no longer received at the common input.

Abstract: The present disclosure relates to a differential drive circuit. The differential drive circuit generally includes a differential driver, a first transmission line coupled to a first output node of the differential driver, and a second transmission line coupled to a second output node of the differential driver. A laser diode is coupled to the first and second transmission lines. The first and second transmission lines have different delays, lengths, or impedances. In some embodiments, the delay between the first transmission line and the second transmission line is 0.2-0.4 times a rise time or fall time of a signal on either transmission line.

Abstract: An optical transceiver and/or optical network, and methods of monitoring optical transceivers, may be useful for increasing the dynamic range and/or determining the received signal strength and/or link budget of the optical transceiver and/or a different optical transceiver in the optical network. The circuitry generally comprises a photodiode configured to generate a first current responsive to an optical signal, a current mirror configured to produce a second current equal or proportional to the first current, and a nonlinear element configured to produce a first voltage from the first current.

Abstract: Methods for detecting and/or indicating the presence of valid data and threshold setting and data detection circuitry are disclosed. The threshold setting and data detection circuitry and related methods may be useful for fast and accurate reception of optical signals. The detection circuit generally comprises (i) a first circuit configured to regulate or control a DC offset of a differential input signal, and (ii) a second circuit coupled to the first circuit, the second circuit configured to indicate the presence of a data signal at the differential input signal when a voltage difference between true and complementary nodes of the differential input signal is above a predetermined threshold.

Abstract: An optical transceiver and methods for using the same are disclosed. The optical transceiver and methods may be useful for providing more accurate information regarding trends in operation of the optical transceiver, predicting an impending failure of the optical transceiver, and providing details of the optical transceiver prior to failure. The optical transceiver generally includes (1) at least one of (i) a receiver configured to receive optical information and (ii) a transmitter configured to transmit optical information, (2) circuitry configured to sample data for one or more operational parameters of the receiver and/or transmitter, (3) logic configured to perform one or more statistical calculations on the sampled data to generate statistical information, and (iv) one or more memories configured to store the sampled data and the statistical information.

Abstract: A circuit, optical transceiver and/or methods for using the same may be useful for determining average power, extinction ratio, and/or modulation amplitude when monitoring an optical transceiver and/or optical network. The circuit generally comprises a photodiode configured to generate a first current responsive to an optical signal, a current mirror coupled to a first terminal of the photodiode, and a detector coupled to a second terminal of the photodiode. The current mirror is configured to produce a second current equal to or proportional to the first current, and the detector is configured to determine a power or amplitude of the optical signal. Further, the present scheme may communicate information using a low speed signal superimposed on or combined with the relatively high speed optical signal.

Abstract: Methods and circuits for providing a minimum driving voltage to a current-driven load (such as a laser diode) are disclosed. The circuit and methods may be useful for efficiently providing a bias and/or driving current to the current-driven load with minimal energy loss. The circuit generally comprises (1) a driver or voltage source configured to provide the bias and/or driving current to the current-driven load, (2) a sense circuit configured to (i) sense the bias and/or driving current and (ii) convert the bias and/or driving current to a first voltage, and (3) a comparator configured to (i) receive the first voltage and first and second reference voltages and (ii) provide a feedback/error signal to the driver or voltage source, the feedback/error signal configured to maintain or adjust the bias and/or driving current at or towards a target value.

Abstract: The present disclosure relates to an optical power monitoring circuit including an automatic power control (APC) loop and a microcontroller unit (MCU), and a method for monitoring the same. The APC loop comprises a laser diode (LD) and a feedback loop to maintain a laser optical power. The MCU is configured to (i) monitor a bias current using a current sense circuit, (ii) monitor a rate of change of the bias current with time, and (iii) adjust a target power of the APC loop. By monitoring the bias current and the rate of change, and comparing them against thresholds, the target power can be adjusted by the MCU, to prevent roll-over in the laser diode, damage to the laser, and/or a hard failure in the data links that use the laser.

Abstract: An optical transceiver and/or optical network, and methods of monitoring optical transceivers, may be useful for increasing the dynamic range and/or determining the received signal strength and/or link budget of the optical transceiver and/or a different optical transceiver in the optical network. The circuitry generally comprises a photodiode configured to generate a first current responsive to an optical signal, a current mirror configured to produce a second current equal or proportional to the first current, and a nonlinear element configured to produce a first voltage from the first current.

Abstract: A circuit, optical transceiver and/or methods for using the same may be useful for determining average power, extinction ratio, and/or modulation amplitude when monitoring an optical transceiver and/or optical network. The circuit generally comprises a photodiode configured to generate a first current responsive to an optical signal, a current mirror coupled to a first terminal of the photodiode, and a detector coupled to a second terminal of the photodiode. The current mirror is configured to produce a second current equal to or proportional to the first current, and the detector is configured to determine a power or amplitude of the optical signal. Further, the present scheme may communicate information using a low speed signal superimposed on or combined with the relatively high speed optical signal.

Abstract: An optical transceiver and methods for using the same are disclosed. The optical transceiver and methods may be useful for providing more accurate information regarding trends in operation of the optical transceiver, predicting an impending failure of the optical transceiver, and providing details of the optical transceiver prior to failure. The optical transceiver generally includes (1) at least one of (i) a receiver configured to receive optical information and (ii) a transmitter configured to transmit optical information, (2) circuitry configured to sample data for one or more operational parameters of the receiver and/or transmitter, (3) logic configured to perform one or more statistical calculations on the sampled data to generate statistical information, and (iv) one or more memories configured to store the sampled data and the statistical information.

Abstract: The present disclosure relates to an optical power monitoring circuit including an automatic power control (APC) loop and a microcontroller unit (MCU), and a method for monitoring the same. The APC loop comprises a laser diode (LD) and a feedback loop to maintain a laser optical power. The MCU is configured to (i) monitor a bias current using a current sense circuit, (ii) monitor a rate of change of the bias current with time, and (iii) adjust a target power of the APC loop. By monitoring the bias current and the rate of change, and comparing them against thresholds, the target power can be adjusted by the MCU, to prevent roll-over in the laser diode, damage to the laser, and/or a hard failure in the data links that use the laser.

Abstract: Methods for detecting and/or indicating the presence of valid data and threshold setting and data detection circuitry are disclosed. The threshold setting and data detection circuitry and related methods may be useful for fast and accurate reception of optical signals. The detection circuit generally comprises (i) a first circuit configured to regulate or control a DC offset of a differential input signal, and (ii) a second circuit coupled to the first circuit, the second circuit configured to indicate the presence of a data signal at the differential input signal when a voltage difference between true and complementary nodes of the differential input signal is above a predetermined threshold.

Abstract: Methods for receiving a signal and a detection circuit are disclosed. The detection circuit and related methods may be useful for the fast and accurate receiving of data signals. The detection circuit generally comprises a first circuit having a first time constant, a second circuit having (i) a common input with the first circuit and (ii) a second time constant, the second time constant being less than the first time constant, and a switch configured to (i) charge the first circuit with an input signal when the switch is in a first state, and (ii) charge or discharge the second circuit with the input signal when the switch is in a second state, the switch having the second state when the input signal is no longer received at the common input.

Abstract: The present disclosure relates to a differential drive circuit. The differential drive circuit generally includes a differential driver, a first transmission line coupled to a first output node of the differential driver, and a second transmission line coupled to a second output node of the differential driver. A laser diode is coupled to the first and second transmission lines. The first and second transmission lines have different delays, lengths, or impedances. In some embodiments, the delay between the first transmission line and the second transmission line is 0.2-0.4 times a rise time or fall time of a signal on either transmission line.

Abstract: In a coarse wavelength division multiplexing (CWDM) optical transmission system, a distributed feedback (DFB) laser is tuned so that the peak reflection of the grating overlaps with the gain range of the DFB laser. The diffraction grating is tuned so that the peak is positioned on the long wavelength end of the gain spectrum at a selected temperature. The optical transmission system operates in an environment having a wide temperature range (i.e., about ?40° C. to about 85° C.). Heat is applied to the laser and as the laser temperature increases, the gain range overtakes the grating peak. When the gain range and the grating peak overlap at increased laser temperature, laser output is improved.

Abstract: In a coarse wavelength division multiplexing (CWDM) optical transmission system, a distributed feedback (DFB) laser is tuned so that the peak reflection of the grating overlaps with the gain range of the DFB laser. The diffraction grating is tuned so that the peak is positioned on the long wavelength end of the gain spectrum at a selected temperature. The optical transmission system operates in an environment having a wide temperature range (i.e., about ?40° C. to about 85° C.). Heat is applied to the laser and as the laser temperature increases, the gain range overtakes the grating peak. When the gain range and the grating peak overlap at increased laser temperature, laser output is improved.