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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.


Structure diagram of TDLAS system: DFB-LD, distributed feedback laser diode; P, R, probe and reference light paths.
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sensors-15-16153-f001: Structure diagram of TDLAS system: DFB-LD, distributed feedback laser diode; P, R, probe and reference light paths.

Mentions: As shown in Figure 1, the measurement system is based on the dual-beam optical structure. A DFB-LD (model WSLS-137010C1424-20) operating at 1368.3 nm (at 28 °C with an injection current of 120 mA) is used as the light source, with emission characteristics of 0.1 mW/mA and 0.004nm/mA. A laser diode controller (LDC; model SRS LDC501) is employed to drive the LD with a resolution of 0.001 °C in temperature and a full scale accuracy of ±0.01% in current, which is connected to a signal generator for an external modulation signal with a conversion factor of 25 mA/V. The output light emitted from the DFB-LD is split by a wavelength flattened single-mode 1 × 2 fiber coupler into two paths (P path and R path) with a splitting ratio of 1:1. P path connects a 10-cmgas cell as a probe beam, while R path is used as a reference beam in assist. Light in both paths is detected by two identical InGaAs photo diodes (PDs) and processed with circuits in R minus P mode to get absorption peaks. After further amplification by circuits, the absorption peaks and R path signals are acquired by a digital oscilloscope for analysis with a computer program. The gas cell is placed in the air.


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)

Structure diagram of TDLAS system: DFB-LD, distributed feedback laser diode; P, R, probe and reference light paths.
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-16153-f001: Structure diagram of TDLAS system: DFB-LD, distributed feedback laser diode; P, R, probe and reference light paths.
Mentions: As shown in Figure 1, the measurement system is based on the dual-beam optical structure. A DFB-LD (model WSLS-137010C1424-20) operating at 1368.3 nm (at 28 °C with an injection current of 120 mA) is used as the light source, with emission characteristics of 0.1 mW/mA and 0.004nm/mA. A laser diode controller (LDC; model SRS LDC501) is employed to drive the LD with a resolution of 0.001 °C in temperature and a full scale accuracy of ±0.01% in current, which is connected to a signal generator for an external modulation signal with a conversion factor of 25 mA/V. The output light emitted from the DFB-LD is split by a wavelength flattened single-mode 1 × 2 fiber coupler into two paths (P path and R path) with a splitting ratio of 1:1. P path connects a 10-cmgas cell as a probe beam, while R path is used as a reference beam in assist. Light in both paths is detected by two identical InGaAs photo diodes (PDs) and processed with circuits in R minus P mode to get absorption peaks. After further amplification by circuits, the absorption peaks and R path signals are acquired by a digital oscilloscope for analysis with a computer program. The gas cell is placed in the air.

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.