Elimination of residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy using an optical fiber delay line

Chakraborty, Arup Lal; Ruxton, Keith; Johnstone, Walter; Lengden, Michael; Duffin, Kevin L.

doi:10.1364/oe.17.009602

Cited by 53 publications

(25 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the analysis of TDLS with WMS for weak absorption, the detected signals can be expanded based on Taylor-series. This can simplify the analysis of the absorption line shape function [9,11]. All the generated harmonic signals can be found from the Taylor-series expansion of a(v) around v 1 as follows [11].…”

Section: Simple Analysis Of Second Harmonic Signals In Wmsmentioning

confidence: 99%

“…Thus some compensation or calibration has to be made for further process of distorted spectra. Recently, two new techniques called intensity-stabilized spectrometer [8], and optical fiber delay line method [9], have been reported for suppression of RAM effect. It is shown in both reports that elimination of RAM would increase the sensitivity of TDLS with WMS, and then exploit its full potential.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Dual-beam wavelength modulation spectroscopy for sensitive detection of water vapor

et al. 2014

View full text Add to dashboard Cite

A technique was reported for sensitive detection of water vapor based on dual-beam wavelength modulation spectroscopy (WMS). Particular attention was focused on the problem of laser power variation (LPV) and residual amplitude modulation (RAM), which accounted for the absorption profile's distortion during application of WMS. Impact from LPV and RAM was eliminated by photocurrent normalization through a balanced ratiometric detector, which was a dual-beam technique with shot noiselevel performance. When consideration of distortion was required, this could enormously simplify the spectra analysis procedure. In the experiment symmetry of the WMS, profile had gotten an improvement by a factor of about 102 compared with traditional single-beam method. During the application test of water vapor detection, the detected amplitude of WMS was well proportional to water vapor concentration ranging from 25 to 1,048 ppmv and the sensitivity was achieved to be 52 ppbv for just a 10-cm optical path length.

show abstract

Section: Simple Analysis Of Second Harmonic Signals In Wmsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dual-beam wavelength modulation spectroscopy for sensitive detection of water vapor

et al. 2014

View full text Add to dashboard Cite

show abstract

“…This fortuitous situation has enabled the use of RAM method at the phase-quadrature frequency to recover the absorption lineshape and to thereby achieve calibration-free measurement of the concentration of methane. The sensitivity of the system can be further increased by implementing the RAM nulling method [29]. This is currently being explored.…”

Section: Conclusion and Future Scopementioning

confidence: 99%

Rapid detection of methane, carbon dioxide and ammonia for harsh environments using tunable doide laser spectroscopy

Upadhyay¹,

Dighe²,

Chakraborty³

2013

2013 International Conference on Microwave and Photonics (ICMAP)

Self Cite

View full text Add to dashboard Cite

This paper reports time-varying and simultaneous detection of the pressure and concentration, of hazardous gases such as methane, carbon dioxide and ammonia using tunable diode laser spectroscopy (TDLS). The concentration and pressure of the gases is extracted with a time resolution of 10s, which makes this method useful in applications that require in situ, real-time measurements of several gases. A calibration-free wavelength modulation spectroscopy (WMS) approach known as the Residual Amplitude Modulation (RAM) method has been used at a modulation frequency when intensity modulation (IM)is at phase-quadrature to the frequency modulation (FM). TDLS offers the dual advantage of remote detection of gases and quantification of gas parameters. This makes them ideally suited to hazardous environments such as coal mines.

show abstract

“…The manually controlled fiber-optic RAM nulling technique reported earlier [5], has been extended by incorporating an electronically controlled variable optical attenuator (VOA) and an optical switch. Feedback control has been…”

Section: Microcontroller-operated Ram Nulling Using a Mems Electronicmentioning

confidence: 99%

Detection of methane at 1650nm and carbon dioxide at 2004nm using tunable diode laser spectroscopy

Upadhyay

Chakraborty

2012

International Conference on Fibre Optics and Photonics

Self Cite

View full text Add to dashboard Cite

Recovery of the absolute absorption line shape is demonstrated for methane with a 1650nm edge-emitting laser and for carbon dioxide with a 2004nm VCSEL. The potential for direct detection and wavelength modulation spectroscopy are explored.OCIS codes: (300.6260) Spectroscopy, diode lasers; (120.0280) Remote sensing and sensors; (280.4788) Optical sensing and sensors 1. Calibration-free wavelength modulation spectroscopy techniques Industrial gas measurement using tunable diode laser spectroscopy (TDLS) has witnessed significant advances in recent times. The advent of frequency-agile semiconductor lasers in mid-infrared region [1], has given new impetus to the extraction of concentration, pressure and temperature [2,3]. TDLS is ideal for high-specificity, real-time measurements and offers very good sensitivity particularly for mid-infrared fundamental absorption lines of gases. When the unavailability of mid-infrared sources precludes direct detection and one is constrained to probe the significantly weaker near-infrared overtones, one uses wavelength modulation spectroscopy (WMS) to achieve high sensitivity. WMS essentially involves the interaction of the spectrally-modulated output of a laser with a gas absorption line to give rise to signal components at various harmonics of the modulation frequency (f m ).For injection current-modulated laser diodes, the intensity modulation (IM) is separated from the wavelength modulation (WM) by a modulation frequency-dependent phase angle ψ 1 , and is predominantly linear. The IM and the WM components interact with a gas absorption line to give rise to various concentration-dependent IM-WM terms that become progressively smaller at increasingly higher harmonics of f m . Typically, one of these harmonics is recovered and the gas concentration and pressure are extracted from specific attributes of the detected signal. WMS signals are characterized by the modulation index defined as m = a/γ, where γ is the half-width-half-maximum value of the linewidth of the absorption feature and ais the WM amplitude. The m-value is a very important parameter because it determines the form and amplitude of the Fourier coefficients of the spectrally-modulated absorption line and therefore the strength of the harmonic signals. Edge-emitting lasers as well as VCSELs have been popular for WMS because of their unique and rather contrasting properties. VCSELs are particularly popular because of their lowpower operation, wide tunability, narrow linewidth and low intensity modulation properties.Traditional 1f or 2f WMS however requires signal calibration because the 1f and 2f signals are affected by variable system parameters such as laser intensity, optical throughput and variable gas pressure in industrial processes. Two recent calibration-free 1f WMS techniques namely the RAM method and the Phasor Decomposition (PD) method [3], that allows the recovery of the absolute gas absorption line from which gas parameters are conveniently extracted. These methods are particularly useful for edge-emitting ...

show abstract

Elimination of residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy using an optical fiber delay line

Cited by 53 publications

References 11 publications

Dual-beam wavelength modulation spectroscopy for sensitive detection of water vapor

Dual-beam wavelength modulation spectroscopy for sensitive detection of water vapor

Rapid detection of methane, carbon dioxide and ammonia for harsh environments using tunable doide laser spectroscopy

Detection of methane at 1650nm and carbon dioxide at 2004nm using tunable diode laser spectroscopy

Contact Info

Product

Resources

About