A Time Difference Method for Measurement of Phase Shift between Distributed Feedback Laser Diode (DFB-LD) Output Wavelength and Intensity
School of Information Science and Engineering, Shandong University, Jinan 250100, China
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Academic Editor: Vittorio M.N. Passaro
Sensors 2015, 15(7), 16153-16161; https://doi.org/10.3390/s150716153
Received: 21 April 2015 / Revised: 25 June 2015 / Accepted: 29 June 2015 / Published: 6 July 2015
(This article belongs to the Special Issue Optical Sensors for Chemical, Biological and Industrial Applications)
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.
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Keywords:
phase shift; DFB-LD; infrared spectroscopy; fiber optics sensors
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MDPI and ACS Style
Liu, Y.; Chang, J.; Lian, J.; Liu, Z.; Wang, Q.; Zhu, C. A Time Difference Method for Measurement of Phase Shift between Distributed Feedback Laser Diode (DFB-LD) Output Wavelength and Intensity. Sensors 2015, 15, 16153-16161.
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