DRIVING CIRCUIT OF A LASER DIODE AND DRIVING METHOD OF A LASER DIODE
A driving method of a laser diode includes setting a bias current, a modulation current, a first target corresponding to a predetermined average power, and a second target corresponding to a predetermined average modulation power; executing a first adjusting current step group; generating a temporary modulation current according to the modulation current; executing a second adjusting current step group; and executing the first adjusting current step group again.
This application claims the benefit of U.S. Provisional Application No. 61/874,369, filed on Sep. 6, 2013 and entitled “Dual Closed Loop,” the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a driving circuit of a laser diode and a driving method of a laser diode, and particularly to a driving circuit of a laser diode and a driving method of a laser diode that have dual feedback loop for adjusting current to make the laser diode maintain a fixed extinction ratio under different operation temperatures.
2. Description of the Prior Art
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An embodiment of the present invention provides a driving method of a laser diode. The driving method includes setting a bias current, a modulation current, a first target corresponding to a predetermined average power, and a second target corresponding to a predetermined average modulation power; executing a first adjusting current step group, wherein the first adjusting current step group includes driving a laser diode according to the bias current and the modulation current; generating a first monitor value corresponding to an average power of the laser diode according to light emitted by the laser diode; comparing the first monitor value with the first target; and adjusting the bias current or maintaining the bias current according to a first comparison result; generating a temporary modulation current according to the modulation current; executing a second adjusting current step group, wherein the second adjusting current step group includes driving the laser diode according to the bias current and the temporary modulation current; generating a second monitor value corresponding to an average modulation power of the laser diode according to the light emitted by the laser diode; comparing the second monitor value with the second target; and adjusting the modulation current or maintaining the modulation current according to a second comparison result; and executing the first adjusting current step group again.
Another embodiment of the present invention provides a driving method of a laser diode. The driving method includes setting a bias current, a modulation current, a first target corresponding to a predetermined average power, and a second target corresponding to a predetermined average modulation power; repeatedly executing a first adjusting current step group a first predetermined times, wherein the first adjusting current step group includes driving a laser diode according to the bias current and the modulation current; generating a first monitor value corresponding to an average power of the laser diode according to light emitted by the laser diode; comparing the first monitor value with the first target; and adjusting the bias current or maintaining the bias current according to a first comparison result; generating a temporary modulation current according to the modulation current; repeatedly executing a second adjusting current step group a second predetermined times, wherein the second adjusting current step group includes driving the laser diode according to the bias current and the temporary modulation current; generating a second monitor value corresponding to an average modulation power of the laser diode according to the light emitted by the laser diode; comparing the second monitor value with the second target; and adjusting the modulation current or maintaining the modulation current according to a second comparison result; and executing the first adjusting current step group again the first predetermined times.
Another embodiment of the present invention provides a driving circuit of a laser diode. The driving circuit includes a driving unit, a power generation unit, a comparison unit, a first current generation module, and a second current generation module. The driving unit is used for driving a laser diode according to a bias current, a modulation current, and a first driving signal, or according to the bias current, a temporary modulation current, and a second driving signal, or according to the bias current and the modulation current, or according to the bias current and the temporary modulation current. The monitor unit is used for generating a first monitor value corresponding to an average power of the laser diode and a second monitor value corresponding to an average modulation power of the laser diode according to light emitted by the laser diode. The comparison unit is used for comparing the first monitor value with a first target corresponding to a predetermined average power to generate a first comparison result, and comparing the second monitor value with a second target corresponding to a predetermined average modulation power to generate a second comparison result. The first current generation module is used for executing a first corresponding operation on the bias current according to the first comparison result. The second current generation module is used for generating the temporary modulation current according to the modulation current, and executing a second corresponding operation on the modulation current according to the second comparison result.
The present invention provides a driving circuit of a laser diode and a driving method of a laser diode. The driving circuit and the driving method utilize a first current generation module of the driving circuit and an first target to adjust a bias current driving the laser diode, and utilize a second current generation module of the driving circuit and a second target to adjust a modulation current driving the laser diode. Therefore, compared to the prior art, the present invention has advantages as follows: first, because the present invention has a feedback loop corresponding to the first current generation module adjusting the bias current and a feedback loop corresponding to the second current generation module adjusting the modulation current, the present invention does not need an additional memory; and second, because the present invention has the feedback loop corresponding to the first current generation module adjusting the bias current and the feedback loop corresponding to the second current generation module adjusting the modulation current, the present invention can make the laser diode maintain a fixed extinction ratio under different operation temperatures.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
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Step 300: Start.
Step 302: A user sets a bias current IB, a modulation current IM, a first target PAVT corresponding to a predetermined average power, and a second target PMT corresponding to a predetermined average modulation power.
Step 304: The driving unit 202 drives a laser diode 214 according to the bias current IB and the modulation current IM.
Step 306: The monitor unit 204 generates a first monitor value PAV corresponding to an average power of the laser diode 214 when the laser diode 214 is driven by the bias current IB and the modulation current IM according to light emitted by the laser diode 214.
Step 308: The first comparator 2062 of the comparison unit 206 compares the first monitor value PAV with the first target PAVT to generate a first comparison result.
Step 310: The first current generation module 208 executes a first corresponding operation on the bias current IB according to the first comparison result.
Step 312: The temporary modulation current generator 2110 of the second current generation module 210 generates a temporary modulation current IMT according to the modulation current IM.
Step 314: The driving unit 202 drives the laser diode 214 according to the bias current IB and the temporary modulation current IMT.
Step 316: The monitor unit 204 generates a second monitor value PMV corresponding to an average modulation power of the laser diode 214 when the laser diode 214 is driven by the bias current IB and the temporary modulation current IMT according to the light emitted by the laser diode 214.
Step 318: The second comparator 2064 of the comparison unit 206 compares the second monitor value PMV with the second target PMT to generate a second comparison result.
Step 320: The second current generation module 210 executes a second corresponding operation on the modulation current IM according to the second comparison result, go to Step 304.
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Step 500: Start.
Step 502: The user sets a bias current IB, a modulation current IM, a first target PAVT corresponding to a predetermined average power, and a second target PMT corresponding to a predetermined average modulation power.
Step 504: The driving unit 202 drives the laser diode 214 according to the bias current IB and the modulation current IM.
Step 506: The monitor unit 204 generates a first monitor value PAV corresponding to an average power of the laser diode 214 when the laser diode 214 is driven by the bias current IB and the modulation current IM according to light emitted by the laser diode 214.
Step 508: The first comparator 2062 of the comparison unit 206 compares the first monitor value PAV with the first target PAVT to generate a first comparison result.
Step 510: The first current generation module 208 executes a first corresponding operation on the bias current IB according to the first comparison result, and the first counter 2086 of the first current generation module 208 accumulates a comparison number executed by the first comparator 2062.
Step 512: If the comparison number accumulated by the first counter 2086 is equal to a first predetermined value; if yes, go to Step 514; if no, go to Step 504.
Step 514: The temporary modulation current generator 2110 of the second current generation module 210 generates a temporary modulation current IMT according to the modulation current IM.
Step 516: The driving unit 202 drives the laser diode 214 according to the bias current IB and the temporary modulation current IMT.
Step 518: The monitor unit 204 generates a second monitor value PMV corresponding to an average modulation power of the laser diode 214 when the laser diode 214 is driven by the bias current IB and the temporary modulation current IMT according to the light emitted by the laser diode 214.
Step 520: The second comparator 2064 of the comparison unit 206 compares the second monitor value PMV with the second target PMT to generate a second comparison result.
Step 522: The second current generation module 210 executes a second corresponding operation on the modulation current IM according to the second comparison result, and the second counter 2106 of the second current generation module 210 accumulates a comparison number executed by the second comparator 2064.
Step 524: If the comparison number accumulated by the second counter 2106 is equal to a second predetermined value; if yes, go to Step 504; if no, go to Step 506.
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To sum up, the driving circuit of a laser diode and the driving method of a laser diode utilize the first current generation module and the first target to adjust the bias current driving the laser diode, and utilize the second current generation module and the second target to adjust the modulation current driving the laser diode. Therefore, compared to the prior art, the present invention has advantages as follows: first, because the present invention has a feedback loop corresponding to the first current generation module adjusting the bias current and a feedback loop corresponding to the second current generation module adjusting the modulation current, the present invention does not need an additional memory; and second, because the present invention has the feedback loop corresponding to the first current generation module adjusting the bias current and the feedback loop corresponding to the second current generation module adjusting the modulation current, the present invention can make the laser diode maintain a fixed extinction ratio under different operation temperatures.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
Claims
1. A driving method of a laser diode, the driving method comprising:
- setting a bias current, a modulation current, a first target corresponding to a predetermined average power, and a second target corresponding to a predetermined average modulation power;
- executing a first adjusting current step group, wherein the first adjusting current step group comprises: driving a laser diode according to the bias current and the modulation current; generating a first monitor value corresponding to an average power of the laser diode according to light emitted by the laser diode; comparing the first monitor value with the first target; and adjusting the bias current or maintaining the bias current according to a first comparison result;
- generating a temporary modulation current according to the modulation current;
- executing a second adjusting current step group, wherein the second adjusting current step group comprises: driving the laser diode according to the bias current and the temporary modulation current; generating a second monitor value corresponding to an average modulation power of the laser diode according to the light emitted by the laser diode; comparing the second monitor value with the second target; and adjusting the modulation current or maintaining the modulation current according to a second comparison result; and
- executing the first adjusting current step group again.
2. The driving method of claim 1, wherein when the first comparison result is the first monitor value greater than the first target, the bias current is decreased.
3. The driving method of claim 1, wherein when the first comparison result is the first monitor value less than the first target, the bias current is increased.
4. The driving method of claim 1, wherein when the first comparison result is the first monitor value equal to the first target, the bias current is maintained.
5. The driving method of claim 1, wherein when the second comparison result is the second monitor value greater than the second target, the modulation current is decreased.
6. The driving method of claim 1, wherein when the second comparison result is the second monitor value less than the second target, the modulation current is increased.
7. The driving method of claim 1, wherein when the second comparison result is the second monitor value equal to the second target, the modulation current is maintained.
8. The driving method of claim 1, further comprising:
- driving the laser diode according to the bias current, the modulation current, and a first driving signal.
9. The driving method of claim 8, wherein the first driving signal is a burst mode driving signal.
10. The driving method of claim 8, wherein the first driving signal is a continuous mode driving signal.
11. The driving method of claim 1, further comprising:
- driving the laser diode according to the bias current, the temporary modulation current, and a second driving signal.
12. The driving method of claim 11, wherein the second driving signal is a burst mode driving signal.
13. The driving method of claim 11, wherein the second driving signal is a continuous mode driving signal.
14. The driving method of claim 1, wherein the temporary modulation current is a sum of the modulation current and a product of the modulation current and a predetermined value.
15. A driving method of a laser diode, the driving method comprising:
- setting a bias current, a modulation current, a first target corresponding to a predetermined average power, and a second target corresponding to a predetermined average modulation power;
- repeatedly executing a first adjusting current step group a first predetermined times, wherein the first adjusting current step group comprises: driving a laser diode according to the bias current and the modulation current; generating a first monitor value corresponding to an average power of the laser diode according to light emitted by the laser diode; comparing the first monitor value with the first target; and adjusting the bias current or maintaining the bias current according to a first comparison result;
- generating a temporary modulation current according to the modulation current;
- repeatedly executing a second adjusting current step group a second predetermined times, wherein the second adjusting current step group comprises: driving the laser diode according to the bias current and the temporary modulation current; generating a second monitor value corresponding to an average modulation power of the laser diode according to the light emitted by the laser diode; comparing the second monitor value with the second target; and adjusting the modulation current or maintaining the modulation current according to a second comparison result; and
- executing the first adjusting current step group again the first predetermined times.
16. A driving circuit of a laser diode, the driving circuit comprising:
- a driving unit driving a laser diode according to a bias current, a modulation current, and a first driving signal, or according to the bias current, a temporary modulation current, and a second driving signal, or according to the bias current and the modulation current, or according to the bias current and the temporary modulation current;
- a monitor unit generating a first monitor value corresponding to an average power of the laser diode and a second monitor value corresponding to an average modulation power of the laser diode according to light emitted by the laser diode;
- a comparison unit comparing the first monitor value with a first target corresponding to a predetermined average power to generate a first comparison result, and comparing the second monitor value with a second target corresponding to a predetermined average modulation power to generate a second comparison result;
- a first current generation module executing a first corresponding operation on the bias current according to the first comparison result; and
- a second current generation module generating the temporary modulation current according to the modulation current, and executing a second corresponding operation on the modulation current according to the second comparison result.
17. The driving circuit of claim 16, wherein when the first comparison result is the first monitor value greater than the first target, the first current generation module decreases the bias current; when the first comparison result is the first monitor value less than the first target, the first current generation module increases the bias current; and when the first comparison result is the first monitor value equal to the first target, the first current generation module maintains the bias current.
18. The driving circuit of claim 16, wherein when the second comparison result is the second monitor value greater than the second target, the second current generation module decreases the modulation current; when the second comparison result is the second monitor value less than the second target, the second current generation module increases the modulation current; and when the second comparison result is the second monitor value equal to the second target, the second current generation module maintains the modulation current.
19. The driving circuit of claim 16, wherein the first driving signal and the second driving signal are burst mode driving signals.
20. The driving circuit of claim 16, wherein the first driving signal and the second driving signal are continuous mode driving signals.
21. The driving circuit of claim 16, wherein the temporary modulation current is a sum of the modulation current and a product of the modulation current and a predetermined value.
Type: Application
Filed: Sep 5, 2014
Publication Date: Mar 12, 2015
Inventors: Ren-Bang Yeh (New Taipei City), Jiann-Chyi Sam Shieh (San Jose, CA), Chih-Yang Wang (Kaohsiung City)
Application Number: 14/477,893
International Classification: H01S 5/06 (20060101);