Patent Publication Number: US-9431792-B2

Title: Method and apparatus for active voltage regulation in optical modules

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of, and claims priority and benefits of, U.S. patent application Ser. No. 14/135,200 filed Dec. 19, 2013, which further claims the benefit of U.S. Provisional Application Ser. No. 61/747,302 entitled “Method and Apparatus for Active Voltage Regulation in Optical Modules” filed Dec. 29, 2012. The above-referenced applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a method and apparatus for voltage regulation in optical modules, particularly to optimize performance and extend the operating temperature range. 
     Voltage regulators are often used in a variety of electronics applications. However, voltage regulators are not typically used in optical modules, such as transceivers. When voltage regulators are utilized, they are used to provide power isolation, noise filtering, and/or to regulate a nominally fixed input voltage to a supply voltage required by the electronics in the optical module. Therefore, a need exists for active voltage regulation to adjust supply voltages for electronics in an optical module to optimize performance over temperature. 
     SUMMARY OF THE INVENTION 
     A method and apparatus for active voltage regulation in optical modules having a voltage regulator to change the supply voltage provided to laser diode driver and receiver electronics to optimize module performance over temperature is provided. The ambient temperature of the module may be monitored, and the outputs of the voltage regulator may be controlled to provide voltages that may be optimized with respect to temperature for one or more of the integrated circuits in the optical module. This control may be implemented via a temperature sensitive feedback or via a control input from a microcontroller with a temperature monitor input. The supply voltage may be optimized to minimize the voltage required to achieve acceptable performance at a given temperature. Minimizing the supply voltage to an integrated circuit may also lengthen the lifetime of the integrated circuit, and therefore the lifetime of the optical module. In addition, the voltage regulator may be used to provide higher than standard supply voltages to a laser diode driver to compensate for higher laser, particularly vertical-cavity surface-emitting laser (VCSEL), voltage at low temperatures. 
     To this end, an embodiment of an optical module apparatus having active voltage regulation to adjust supply voltages for electronics in an optical module to optimize performance over temperature is provided. The apparatus may have a combination of one or more semiconductor light sources, one or more photodetectors, and zero or more optical modulators. 
     The apparatus may have one or more optical fibers and optics to couple light from the semiconductor light sources into the optical fibers and from the optical fibers onto the photodetectors. The apparatus may also have driver and interface electronics, amplifiers, and microcontrollers. The apparatus may have a temperature monitor having an output and a voltage regulator with one or more outputs. Finally, the apparatus may have voltage regulator control electronics configured to adjust outputs of the voltage regulator with respect to the output of the temperature monitor. 
     In an embodiment, the semiconductor light source may be one or more of the following: a light emitting diode (LED), a vertical-cavity surface-emitting laser (VCSEL), a Fabry-Perot laser and a distributed feedback (DFB) laser. 
     In an embodiment, the photodetector may be one or more of the following: a p-l-n photodetector, an avalanche photodetector, a metal-semiconductor-metal (MSM) photodetector and a traveling wave photodetector. 
     In an embodiment, the semiconductor light source may be directly modulated or may be modulated using an optical modulator. 
     In an embodiment, the temperature monitor may be a thermistor or a thermocouple. 
     In an embodiment, the optical fiber may be a single mode fiber or a multimode fiber. 
     In an embodiment, the optical module may be an optical transceiver, an optical transmitter or an optical receiver. 
     In an embodiment, the optical module may transmit digital data and/or analog data. In an embodiment, the optical module may be used to implement data interconnects for control systems or for clock signal distribution. 
     In an embodiment, the optical module may be an optical interrogator. 
     In an embodiment, the voltage regulator enables the optical module to operate on different supply voltages. 
     In an embodiment, the voltage regulator may stabilize the voltage output and may reduce supply voltage ripple. 
     In an embodiment, the output voltages of the voltage regulator may be controlled to optimize performance of the optical module over temperature. 
     In an embodiment, the output voltages of the voltage regulator may be adjusted to provide the minimum supply voltage required at a given temperature by different electronics enabling power consumption to be minimized. 
     In an embodiment, the output voltages of the voltage regulator may be adjusted to provide the minimum supply voltage required at a given bit rate by different electronics enabling power consumption to be minimized. 
     In an embodiment, the output voltages of the voltage regulator may be adjusted to provide the minimum supply voltage required at a given temperature by different electronics enabling the optical module lifetime to be maximized. In an embodiment, the output voltages of the voltage regulator may be adjusted to provide the minimum supply voltage required at a given bit rate by different electronics enabling the optical module lifetime to be maximized. 
     In an embodiment, the output voltage of the voltage regulator used as the supply voltage for the laser diode driver may be increased at low temperatures to compensate for higher VCSEL drive voltages at low temperatures. 
     In an embodiment, the output voltage of the voltage regulator used as the supply voltage for the laser diode driver may be adjusted to ensure sufficient voltage headroom at given drive conditions. 
     In an embodiment, the output of the temperature monitor may be used as a control input by the voltage regulator control electronics. 
     In an embodiment, the voltage regulator control electronics adjust the voltage output settings of the voltage regulator. 
     In an embodiment, the voltage regulator control electronics and the temperature monitor may be the same components. 
     In an embodiment, the voltage regulator outputs may be controlled by the voltage regulator control electronics to produce different voltages for different electronics in the optical module. 
     In an embodiment, the temperature monitor may be integrated in the electronics. 
     In another embodiment of the invention, a method of regulating voltage in an optical module is provided. The method may have the steps of: providing one or more semiconductor light sources, one or more photodetectors, and zero or more optical modulators; coupling light from the semiconductor light source into an optical fiber and from the optical fiber onto the photodetector; monitoring the temperature of the optical module; providing a voltage regulator having an output; and adjusting the output of the voltage regulator with respect to the temperature of the optical module. 
     In an embodiment, the method may have the step of providing the output of the voltage regulator to the semiconductor light source as a drive voltage. 
     In an embodiment, the method may have the step of providing the output of the voltage regulator to the photodetector as a bias voltage. 
     In an embodiment, the method may have the step of controlling the output of the voltage regulator outputs to produce different voltages for different electronics in the optical module. 
     In an embodiment, the method may have the step of using the output of the temperature monitor as a control input for adjusting the voltage output settings of the voltage regulator. 
     In an embodiment, the method may have the step of adjusting the output voltages of the voltage regulator to provide a minimum supply voltage required at a given bit rate. 
     In an embodiment, the method may have the step of adjusting the output voltages of the voltage regulator to provide a minimum supply voltage required at a temperature 
     In an embodiment, the method may have the step of adjusting the output voltages of the voltage regulator to optimize performance of the optical module over temperature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an embodiment of an optical module with active voltage regulation wherein the control of the voltage regulator over temperature may be implemented with a temperature dependent resistance. 
         FIG. 2  is a schematic diagram of an embodiment of an optical module with active voltage regulation wherein the control of the voltage regulator over temperature may be implemented using a microcontroller with a temperature monitor input. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A method and apparatus for implementing active voltage regulation in optical modules such as transceivers are provided. In the preferred implementation, a voltage regulator may be used to provide a supply voltage that may be adjusted with temperature to integrated circuits within the optical module to optimize performance of the optical module. The voltage regulator circuit may provide more than one individually controlled supply voltages if different integrated circuits in the optical module require different voltages at a given temperature. By controlling the supply voltages for integrated circuits in the optical module such as laser diode drivers, transimpedance amplifiers, and microcontrollers, the performance of each of these components, as well as other components such as VCSELs, may be optimized to reduce power consumption and improve module lifetime. In addition, the voltage regulator may provide a stable voltage supply at higher than nominal input levels for the laser diode driver at low temperatures, enabling the laser diode driver to drive VCSELs at low temperatures where the VCSEL voltage would be too high without this control. At higher temperatures, the supply voltage to the laser diode driver may be reduced to improve the lifetime of the laser diode driver. In addition, the voltage regulator may also be used to implement more common functions such as voltage step-down and noise filtering. The voltage regulator may also be designed to accommodate a range of input voltages. 
     The control of the voltage regulator over temperature may be implemented in a variety of ways. Referring now to the Figures where like numerals indicate like elements, a schematic diagram of an embodiment of an optical module  10  with active voltage regulation is shown in  FIG. 1 . The control of the voltage regulator  20  over temperature may be implemented with a temperature dependent resistance  90 .  FIG. 2  is a schematic diagram of another embodiment of an optical module  10  with active voltage regulation. The control of the voltage regulator  20  over temperature may be implemented using a microcontroller  100  with a temperature monitor input  110 . 
     For relatively simple monotonic temperature adjustment of the supply voltages, the preferred implementation may use a temperature dependent feedback resistor  90  in the voltage regulator circuit as shown in  FIG. 1 . For designs that require more complex adjustment of the supply voltages versus temperature, the voltage regulator  20  may be controlled with the microcontroller  100  that obtains the temperature of the optical module  10  from the temperature monitor  110  such as a thermistor, as shown in  FIG. 2 . 
       FIG. 1  illustrates a schematic diagram of an embodiment of the optical module  10  with active voltage regulation. The optical module  10  may be used to implement data interconnects for control systems and/or for clock signal distribution. The optical module  10  may be an optical interrogator. 
     The optical module  10  may have the voltage regulator  20 . The control of the voltage regulator  20  over temperature may be implemented with the temperature dependent resistance  90 . The voltage regulator  20  may have an Input Voltage and outputs Supply Voltage  1  and Supply Voltage  2 . The voltage regulator  20  may enable the optical module  10  to operate on different supply voltages. For example, Supply Voltage  1  may be an output supply voltage provided by the voltage regulator  20 . Supply Voltage  1  may be connected as the supply voltage for a laser diode driver  30 . Further, Supply Voltage  1  may be adjusted to ensure sufficient voltage headroom at given drive conditions. 
     The optical module  10  may have an input for Input Data  35 . The laser diode driver  30  may take Input Data  35  and output Data  40  to a vertical-cavity surface-emitting laser (VCSEL)  50 . At low temperatures, Supply Voltage  1  may be increased to compensate for higher VCSEL drive voltages at low temperatures. Supply Voltage  2  may be connected as a supply voltage for a transimpedance amplifier  60 . The transimpedance amplifier  60  may receive Data  65  from a photodetector  70 . The transimpedance amplifier  60  may provide an output of Output Data  75  from the optical module  10 . The optical module  10  may have one or more optical fibers  54  connected between the VCSEL  50  and the photodetector  70  of the same or different optical modules. Optics  56  may also be provided to facilitate coupling light  52  into and/or out of the one or more optical fibers  54 . 
     Control of the voltage regulator  20  over a range of operating temperatures may be implemented with control electronics  80  and/or the temperature dependent resistance/resistor  90 . The temperature dependent resistor  90  may be implemented by a thermistor, a thermocouple or the like. Further, the voltage regulator  20  may stabilize the voltage output and may reduce supply voltage ripple. 
     The output voltages of the voltage regulator  20  may be controlled to optimize performance of the optical module  10  over a range of operating temperatures. The output voltages may also be controlled to minimize power consumption of the optical module  10 . Moreover, the output voltages may also be controlled to maximize the lifetime of the optical module  10 . For example, the output voltages of the voltage regulator  20  may be adjusted to provide the minimum supply voltage required at a given temperature by different electronics enabling power consumption to be minimized. Also, the output voltages of the voltage regulator  20  may be adjusted to provide the minimum supply voltage required at a given bit rate by different electronics. 
     Also, the output voltages of the voltage regulator  20  may be adjusted to provide the minimum supply voltage required at a given temperature by different electronics enabling the lifetime of the optical module  10  to be maximized. Similarly, the output voltages of the voltage regulator may be adjusted to provide the minimum supply voltage required at a given bit rate by different electronics enabling the lifetime of the optical module  10  to be maximized. 
     The ambient temperature of the optical module  10  may be monitored, and the outputs of the voltage regulator  20  may be controlled to provide voltages that may be optimized with respect to temperature for one or more of the integrated circuits in the optical module  10 . This control may be implemented via a temperature sensitive feedback  95  implemented with the control electronics  80  and the temperature dependent resistor  90  as shown in  FIG. 1 . 
       FIG. 2  illustrates a schematic diagram of another embodiment of an optical module with active voltage regulation. Control of the voltage regulator  20  over a range of temperatures may be implemented with the microcontroller  100  and the temperature monitor  110 . Such an embodiment may be preferred where more complex adjustment of the supply voltages with respect to temperature may be required. The voltage regulator  20  may be controlled with the microcontroller  100 . The microcontroller  100  may obtain the temperature of the optical module  10  from the temperature monitor  110 . The temperature monitor  110  may be a thermistor. The temperature monitor  110  may provide an output  115  to the microcontroller  100  that may provide the control input  120  to the voltage regulator control electronics  80 . The output  115  of the temperature monitor  110  may also provide the control input  120  to the voltage regulator control electronics  80 . The voltage regulator control electronics  80  may adjust the voltage output settings of the voltage regulator  20 . In an embodiment of the invention, the voltage regulator control electronics  80  and the temperature monitor  110  may be the same component. Further, the temperature monitor  110  may be integrated in the control electronics  80 . The voltage regulator outputs, for example, Supply Voltage  1  and Supply Voltage  2 , may be controlled by the voltage regulator control electronics  80  to produce different voltages for different electronics in the optical module  10 . Although only two supply voltages are shown in the drawings, additional supply voltages may be provided by the voltage regulator  20  in other embodiments of the invention. 
     The ambient temperature of the optical module  10  may be monitored, and the outputs of the voltage regulator  20  may be controlled to provide voltages that may be optimized with respect to temperature for one or more of the integrated circuits in the optical module  10 . This control may be implemented via the temperature sensitive feedback as shown in  FIG. 1  or via the control input  120  from the microcontroller  100 . The temperature monitor  110  may provide the output  115  to the microcontroller  100  that may provide the control input  120  to the voltage regulator control electronics  80  as shown in  FIG. 2 . 
     It should be understood that various changes and/or modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and/or modifications may be made without departing from the spirit and/or scope of the present invention and without diminishing its attendant advantages. It is, therefore, intended that such changes and/or modifications be covered by the appended claims.