Gas sensing using wavelength modulation spectroscopy

• Type: Article in International Conference Proceedings Book
• Date: 2014

Authors

Viveiros, D (Author) FCUP; Ribeiro, J (Author) FCUP; Flores, D (Author) FCUP; Ferreira, J (Author) Other; Frazao, O (Author) Other; Santos, JL (Author) Other; Baptista, JM (Author) Other

Conference proceedings International

Title: SECOND INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS

2nd International Conference on Applications of Optics and Photonics

Aveiro, PORTUGAL, MAY 26-30, 2014

Indexing

ISI Web of Knowledge - 1 Citation

Scopus - 1 Citation

Scientific classification

FOS: Engineering and technology > Electrical engineering, Electronic engineering, Information engineering

Other information

Authenticus ID: P-009-X5R

DOI: 10.1117/12.2063811

Abstract (EN): An experimental setup has been developed for different gas species sensing based on the Wavelength Modulation Spectroscopy (WMS) principle. The target is the measurement of ammonia, carbon dioxide and methane concentrations. The WMS is a rather sensitive technique for detecting atomic/molecular species presenting the advantage that it can be used in the near-infrared region using optical telecommunications technology. In this technique, the laser wavelength and intensity are modulated applying a sine wave signal through the injection current, which allows the shift of the detection bandwidth to higher frequencies where laser intensity noise is reduced. The wavelength modulated laser light is tuned to the absorption line of the target gas and the absorption information can be retrieved by means of synchronous detection using a lock-in amplifier, where the amplitude of the second harmonic of the laser modulation frequency is proportional to the gas concentration. The amplitude of the second harmonic is normalised by the average laser intensity and detector gain through a LabVIEW (R) application, where the main advantage of normalising is that the effects of laser output power fluctuations and any variations in laser transmission, or optical-electrical detector gain are eliminated. Two types of sensing heads based on free space light propagation with different optical path length were used, permitting redundancy operation and technology validation.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 4