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A Time Difference Method for Measurement of Phase Shift between Distributed Feedback Laser Diode (DFB-LD) Output Wavelength and Intensity.

Liu Y, Chang J, Lian J, Liu Z, Wang Q, Zhu C - Sensors (Basel) (2015)

Bottom Line: This approach takes advantage of asymmetric absorption positions at the same wavelength during wavelength increase and decrease tuning processes in the intensity-time curve by current modulation.The phase shifts at modulation frequencies ranging from 50 Hz to 50 kHz were measured with a resolution of 0.001π.As the modulation frequency increased the shift value increased with a slowed growth rate.

View Article: PubMed Central - PubMed

Affiliation: School of Information Science and Engineering, Shandong University, Jinan 250100, China. Liuyongning1990@163.com.

ABSTRACT
A time difference method to conveniently measure the phase shift between output wavelength and intensity of distributed feedback laser diodes (DFB-LDs) was proposed. This approach takes advantage of asymmetric absorption positions at the same wavelength during wavelength increase and decrease tuning processes in the intensity-time curve by current modulation. For its practical implementation, a measurement example of phase shift was demonstrated by measuring a time difference between the first time and the second time attendances of the same gas absorption line in the intensity-time curve during one sine or triangle modulation circle. The phase shifts at modulation frequencies ranging from 50 Hz to 50 kHz were measured with a resolution of 0.001π. As the modulation frequency increased the shift value increased with a slowed growth rate.

No MeSH data available.


Related in: MedlinePlus

(a) DFB-LD output intensity (red) and wavelength (blue) with a phase shift of 0.1π; (b) Transmitted light intensity (red) and absorption peaks (blue).
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sensors-15-16153-f002: (a) DFB-LD output intensity (red) and wavelength (blue) with a phase shift of 0.1π; (b) Transmitted light intensity (red) and absorption peaks (blue).

Mentions: Here we propose a convenient approach aimed at measuring such a phase shift mentioned above, which takes advantage of asymmetric absorption positions at the same wavelength but belonging to the wavelength increase and decrease tuning processes in the intensity-time curve with current modulation, respectively. A certain gas absorption line is selected to mark a wavelength in the intensity-time curve. Specifically, when absorption happens, it would reduce the intensity of the transmitted light; therefore, the information of tuning wavelengths can be reflected by such an intensity variation. What is more, within a full and symmetric current tuning circle, the same wavelength will appear twice, during the wavelength increase and decrease tuning processes, respectively, and if there exists a phase shift between output wavelength and intensity, the absorption positions will become asymmetric around the intensity symmetry axis in the transmitted intensity-time curve. The time points where absorption happens can be readily measured, and then the phase shift can be calculated based on the relation between the time points, which is explained in more detail in Figure 2. Herein we demonstrate the method by measuring the water vapor absorption line at 1368.6 nm with a full width at half maximum of about 0.0348 nm [9].The wavelength tuning range should be large enough in this measurement method to scan across the absorption line.


A Time Difference Method for Measurement of Phase Shift between Distributed Feedback Laser Diode (DFB-LD) Output Wavelength and Intensity.

Liu Y, Chang J, Lian J, Liu Z, Wang Q, Zhu C - Sensors (Basel) (2015)

(a) DFB-LD output intensity (red) and wavelength (blue) with a phase shift of 0.1π; (b) Transmitted light intensity (red) and absorption peaks (blue).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541872&req=5

sensors-15-16153-f002: (a) DFB-LD output intensity (red) and wavelength (blue) with a phase shift of 0.1π; (b) Transmitted light intensity (red) and absorption peaks (blue).
Mentions: Here we propose a convenient approach aimed at measuring such a phase shift mentioned above, which takes advantage of asymmetric absorption positions at the same wavelength but belonging to the wavelength increase and decrease tuning processes in the intensity-time curve with current modulation, respectively. A certain gas absorption line is selected to mark a wavelength in the intensity-time curve. Specifically, when absorption happens, it would reduce the intensity of the transmitted light; therefore, the information of tuning wavelengths can be reflected by such an intensity variation. What is more, within a full and symmetric current tuning circle, the same wavelength will appear twice, during the wavelength increase and decrease tuning processes, respectively, and if there exists a phase shift between output wavelength and intensity, the absorption positions will become asymmetric around the intensity symmetry axis in the transmitted intensity-time curve. The time points where absorption happens can be readily measured, and then the phase shift can be calculated based on the relation between the time points, which is explained in more detail in Figure 2. Herein we demonstrate the method by measuring the water vapor absorption line at 1368.6 nm with a full width at half maximum of about 0.0348 nm [9].The wavelength tuning range should be large enough in this measurement method to scan across the absorption line.

Bottom Line: This approach takes advantage of asymmetric absorption positions at the same wavelength during wavelength increase and decrease tuning processes in the intensity-time curve by current modulation.The phase shifts at modulation frequencies ranging from 50 Hz to 50 kHz were measured with a resolution of 0.001π.As the modulation frequency increased the shift value increased with a slowed growth rate.

View Article: PubMed Central - PubMed

Affiliation: School of Information Science and Engineering, Shandong University, Jinan 250100, China. Liuyongning1990@163.com.

ABSTRACT
A time difference method to conveniently measure the phase shift between output wavelength and intensity of distributed feedback laser diodes (DFB-LDs) was proposed. This approach takes advantage of asymmetric absorption positions at the same wavelength during wavelength increase and decrease tuning processes in the intensity-time curve by current modulation. For its practical implementation, a measurement example of phase shift was demonstrated by measuring a time difference between the first time and the second time attendances of the same gas absorption line in the intensity-time curve during one sine or triangle modulation circle. The phase shifts at modulation frequencies ranging from 50 Hz to 50 kHz were measured with a resolution of 0.001π. As the modulation frequency increased the shift value increased with a slowed growth rate.

No MeSH data available.


Related in: MedlinePlus