Thermal control for laser diode used in outside plant communications terminal

Claim 2

A circuit for controlling an output power level of a digital data modulated laser diode operating over a thermal gradient, said laser diode emitting optical energy at a remotely commanded optical power level periodically in a burst mode interval of a recurrent frame within a time division multiplex optical communications network, comprising: monitoring means for monitoring a peak output optical power of the laser diode during a said burst mode interval thereof, transimpedance amplifier means for converting a current signal from the monitoring means into a peak optical level voltage representative of sensed peak optical power during the burst mode interval, comparator means for comparing the peak optical level voltage with a reference voltage derived in response to remotely commanded optical output level and for providing a signal representative of a logical condition from said comparison, adjusting means for adjusting the peak optical power based on the signal and the remotely commanded optical output level.

Claim 3

The circuit of claim 1, the adjusting means comprising: strobe generation means for generating a strobe signal from information related in time to the burst mode interval; clocked storage means for storing the signal representive logical condition upon receipt of the strobe signal so as to provide a control signal, current control means in series with the laser diode and responsive to the control signal to regulate current flow through the laser diode.

Claim 4

The circuit set forth in claim 2 wherein the strobe generation means generates the strobe signal at an end of a data burst occuring during a said burst mode interval, the current control means adjusting the current flow through the laser diode in response to the control signal in a subsequent burst mode interval.

Claim 5

The circuit set forth in claim 3 wherein the clocked storage means includes an integrator means for integrating the stored logical condition over a time period to provide the signal control.

Claim 6

The circuit set forth in claim 4 wherein the integrator means includes either a digital counter or an RC circuit.

Claim 7

The circuit set forth in claim 4 wherein the current control means increases the current flow through the laser diode when the peak optical level voltage is less than the reference voltage and decreases the current flow through the laser diode when the peak voltage is greater than the reference voltage.

Claim 8

The circuit set forth in claim 2 further comprising a power bus for powering the monitoring means, the transimpedance amplifier means, the comparator means, and the clocked storage means, the power bus having a voltage less than 10 volts.

Claim 9

The circuit set forth in claim 5 wherein the adjusting means includes a digital counter whereby the logical condition used for adjusting the peak optical power is generated less frequently than once a frame.

Claim 10

The circuit set forth in claim 1 wherein the adjusting means includes power tuning optical power control means for responding to logical signals relating to the remotely commanded optical power level by controlling bias current through said laser diode during each said burst mode interval to adjust its peak optical power to the commanded level.

Claim 11

The circuit set forth in claim 1 further comprising alternating current coupling means between the transimpedance amplifier means and an input of the comparator means, and voltage clamp means connected to said input of the comparator means for clamping the peak voltage at said input to a value between 0.1 volts and 4.0 volts.

Claim 12

The circuit set forth in claim 2 wherein the circuit receives and responds to a transmit enable control signal marking in time the boundaries of the burst mode interval, an edge of the transmit enable control signal marking an end of the burst mode interval being used for generating the strobe signal, the circuit receiving and modulating a bias current through the laser diode with digital data transitions representing communications information.

Claim 13

The circuit set forth in claim 2 wherein the strobe generation means includes means for characterizing the strobe with information relating to relative humidity at the circuit and further comprising alarm means responsive to the strobe for generating an alarm when the relative humidity exceeds a predetermined level.

Claim 14

A circuit for controlling the output power level of a digital data modulated laser diode operating periodically in a burst mode interval of a recurrent frame within a time division multiplex optical communications network, comprising: enabling means for generating a transmit enable signal denoting a beginning boundary of the burst mode interval; monitoring means for monitoring an output optical power of a LOW pedestal signal of the laser diode during a beginning portion of the burst mode when digital data modulation is not being sent by the laser diode; transimpedance amplifier means for converting a current signal from the monitoring means into an optical level voltage representative of sensed optical power during the beginning portion of the burst mode interval; comparator means for comparing a maximum value of the optical level voltage with a dynamic reference voltage and for providing a signal representative of a logical condition from said comparison; and adjusting means for adjusting the LOW pedestal signal based upon a value of the signal.

Claim 15

A circuit for controlling the output power level of a digital data modulated laser diode operating periodically in a burst mode interval of a recurrent frame within a time division multiplex optical communications network, comprising: enabling means for generating a transmit enable signal denoting a beginning boundary of the burst mode interval; monitoring means for monitoring an output optical power of a LOW pedestal signal of the laser diode during a beginning portion of the burst mode when digital data modulation is not being sent by the laser diode; transimpedance amplifier means for converting a current signal from the monitoring means into an optical level voltage representative of sensed optical power during the beginning portion of the burst mode interval; comparator means for comparing a maximum value of the optical level voltage with a dynamic reference voltage and for providing a signal representative of a logical condition from said comparison; and adjusting means for adjusting the LOW pedestal signal based upon a value of the signal.

Claim 16

The circuit of claim 13, the adjusting means comprising: strobe generation means for generating a strobe signal from information related in time to the burst mode interval; clocked storage means for storing the signal representative of the logical condition upon receipt of the strobe signal so as to provide a control signal, current control means in series with the laser diode and responsive to the control signal to regulate current flow through the laser diode.

Claim 17

The circuit set forth in claim 14 wherein the strobe generation means generates the strobe signal in a transmit enable time interval prior to transmitting digital data, the current control means adjusting the current flow through the laser in response to the control signal in a subsequent transmit enable time interval.

Claim 18

The circuit set forth in claim 15 wherein the clock storage means includes an integrator means for integrating the stored logical condition over a time period to provide the control signal.

Claim 19

The circuit set forth in claim 16 wherein the integrator means includes at least one of a digital counter and an RC circuit.

Claim 20

The circuit set forth in claim 17 wherein the adjusting means includes a digital counter whereby the signal representative of the logical condition used for adjusting the LOW pedestal signal is generated less frequently than once a frame.

Claim 21

The circuit set forth in claim 16 wherein the current control means increases the current flow through the laser diode when the pedestal voltage is less than the dynamic reference voltage and decreases the current flow through the laser diode when the LOW pedestal signal voltage is greater than the reference voltage.

Claim 22

The circuit set forth in claim 13 further comprising power tuning optical power control means for responding to externally supplied logical signals by controlling bias current through said laser diode during each said burst mode interval.

Claim 23

The circuit set forth in claim 13 wherein the digital data transitions are presented to the laser diode after a predetermined pedestal interval, and the strobe generation means is responsive to the beginning of the digital data transition within the interval.

Claim 24

The circuit set forth in claim 21 wherein the transimpedance amplifier means is directly coupled to an input of the comparator means, and further comprising a resistor-capacitor network means connected to a voltage reference input of the comparator means and to the direct coupled input of the comparator means, the time constant of the resistor-capacitor network being longer than the pedestal interval thereby to supply as the dynamic reference voltage to the comparator means the voltage present at the directly coupled input before the occurence of the digital data.

Claim 25

A circuit for controlling the output power level of a digital data modulated laser diode operating periodically in a burst mode interval of a recurrent frame within a time division multiplex optical communications network, the laser diode including a reverse facet photodetector for monitoring the optical output power of the laser diode during each burst mode interval, the circuit comprising: transimpedance amplifier means for converting a current signal from the photodetector into an optical level voltage representative of sensed optical power during the burst mode interval, comparator means for comparing the optical level voltage with a dynamic reference voltage and for providing a signal representative of a logical condition from said comparison, clocked storage means for storing the signal representative of the logical condition upon receipt of a strobe signal, integrator means for integrating the stored signal representative of the logical condition over a time period to provide a control signal, current control means in series with the laser diode and responsive to the control signal to regulate current flow through the laser diode, and strobe generation means for generating the strobe signal from information related in time to the burst mode interval.

Claim 26

A circuit for controlling the output power level of a digital data modulated laser diode operating periodically in a burst mode interval of a recurrent frame within a time division multiplex optical communications network, the laser diode including a reverse facet photodetector for monitoring the optical output power of the laser diode during each burst mode interval, the circuit comprising: transimpedance amplifier means for converting a current signal from the photodetector into an optical level voltage representative of sensed optical power during the burst mode interval, comparator means for comparing the optical level voltage with a dynamic reference voltage and for providing a signal representative of a logical condition from said comparison, clocked storage means for storing the signal representative of the logical condition upon receipt of a strobe signal, integrator means for integrating the stored signal representative of the logical condition over a time period to provide a control signal, current control means in series with the laser diode and responsive to the control signal to regulate current flow through the laser diode, and strobe generation means for generating the strobe signal from information related in time to the burst mode interval.

Claim 27

The circuit set forth in claim 23 wherein the current control means further comprises optical power control means for responding to externally supplied logical signals by controlling bias current through said laser diode during each burst mode interval and further comprising dynamic reference voltage generating means for generating the dynamic reference voltage in function of the externally supplied logical signals and applying the dynamic reference voltage to the comparator means.

Claim 28

The circuit set forth in claim 23 wherein the circuit receives and responds to a transmit enable control signal marking in time the boundaries of the burst mode interval and wherein the circuit receives and modulates a bias current through the laser diode with digital data transitions representing communications information.

Claim 29

The circuit set forth in claim 25 wherein the strobe generation means is responsive to a transition of the transmit control signal marking the end boundary of the burst mode interval.

Claim 30

The circuit set forth in claim 25 wherein the digital data transitions are presented to the laser diode after a predetermined pedestal interval, and the strobe generation means is responsive to the beginning of the digital data modulation within the interval.

Claim 31

The circuit set forth in claim 27 wherein the transimpedance amplifier means is directly coupled to an input of the comparator means, and further comprising a resistor-capacitor network means connected to a voltage reference input of the comparator means and to the direct coupled input of the comparator means, the time constant of the resistor-capacitor network being longer than the pedestal interval thereby to supply as the dynamic reference voltage to the comparator means the voltage present at the directly coupled input before the occurrence of the burst mode interval.

Claim 32

The circuit set forth in claim 28 wherein the current control means further comprises optical power control means for responding to externally supplied logical signals by controlling bias current through said laser diode during each said burst mode interval.

Claim 35

The method set forth in claim 30 wherein the step of converting the component into a control signal comprises the steps of converting the component into a current with a photodiode and translating the current into a control voltage with transimpedance amplifier means, and wherein the step of comparing the control signal with a dynamic reference signal comprises comparing the control voltage with a reference voltage.

Claim 36

The method set forth in claim 30, wherein the dynamic reference voltage is dynamically established during operation of the optical communications network in function of at least one of externally supplied optical power level control signals and internally generated reference voltages related to dynamic detection of low pedestal knee characteristics of the laser diode across said thermal gradient.