A. C. L. Wong

The Hong Kong Polytechnic University, Hong Kong, Hong Kong

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Publications (7)9.6 Total impact

  • A.C.L. Wong · W.H. Chung · H.Y. Tam · C. Lu
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    ABSTRACT: We report the fabrication of extremely short linear-cavity distributed Bragg reflector fiber lasers (DBR-FLs). It has a total length of 7 mm, the shortest FL being reported. The FLs are characterized in details. We constructed a FL sensor array that has great potentials for large-scale, high sensitivity sensing applications.
    Communications and Photonics Conference and Exhibition (ACP), 2010 Asia; 01/2011
  • A. C. L. Wong · W. H. Chung · H. Y. Tam · C. Lu
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    ABSTRACT: A low-noise, ultra-short linear-cavity distributed feedback fiber laser (DFB-FL) with extremely narrow linewidth is presented. The FL has a total length of 17 mm, which is, to our knowledge, the shortest DFB-FL being reported. It has a measured linewidth of merely 250 Hz without active stabilization. It has a polarization beat frequency of 101 MHz, which is several times lower than that of most FLs. The relaxation oscillation frequency and relative peak are 110 kHz and −76.5 dB/Hz, respectively. The FL exhibited low-noise characteristics, with an intensity noise of −107 dB/Hz at 1 MHz. Due to low dopant concentration of the EDF and low splice loss with ordinary single-mode fibers, the net insertion loss amounts to only 0.45 dB. Such low pump power loss greatly enhances the capability of multiplexing a large number of FL sensors. Thus, these ultra-short DFB-FLs open up new opportunities for the development of compact-sized point sensor array systems for large-scale high sensitivity sensing applications.
    Laser Physics 01/2011; 21(1):163-168. DOI:10.1134/S1054660X10230143 · 1.03 Impact Factor
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    ABSTRACT: We propose and demonstrate using a single tilted moiré fiber Bragg grating (TMFBG) with the discrete wavelet transform (DWT) technique for simultaneous measurement of refractive index (RI) and temperature. The particular feature of interest is that the spectrum consists of two separate parts associated with the phase-shifted main Bragg mode and discrete cladding modes, and that they have distinctive responses to RI and temperature. Our results showed that the cladding modes are, while the Bragg mode is not, sensitive to the surrounding RI. On the other hand, both the Bragg and cladding modes have the same linear temperature response. Hence, temperature can be obtained from the Bragg mode shift, and RI from the differential shift between the Bragg and cladding modes. In our experiment, the measured shifts of the Bragg and cladding modes can be unambiguously determined by applying the DWT technique. Thus, simultaneous two-parameter sensing using only a single TMFBG sensor is realized.
    IEEE Photonics Technology Letters 12/2010; DOI:10.1109/LPT.2010.2072955 · 2.11 Impact Factor
  • A. C. L. Wong · M. Giovinazzo · H. Y. Tam · C. Lu · G. D. Peng
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    ABSTRACT: We present using a single tilted moiré fiber Bragg grating for simultaneous measurement of refractive index and temperature using the discrete wavelet transform technique. The former is obtained from the differential shift between the Bragg and cladding modes, and the latter from the Bragg mode shift only.
  • Source
    H Y Fu · A C L Wong · P A Childs · H Y Tam · Y B Liao · C Lu · P K A Wai
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    ABSTRACT: Three multiplexing schemes are presented for polarization-maintaining photonic crystal fiber based Sagnac interferometric sensors. The first technique is wavelength division multiplexing using coarse wavelength division multiplexers (CWDMs) to distinguish signals from each multiplexed sensor in different wavelength channels. The other two schemes are to multiplex sensors in series along a single fiber link and in parallel by using fiber-optic couplers. While for the CWDM scheme, the multiplexed sensing signal can be obtained by direct measurement; for the other two multiplexing techniques, the sensing signal is more complex and cannot be easily demultiplexed. Thus, some signal processing methods are required. In this regard, two mathematical transformations, namely the discrete wavelet transform and Fourier transform, have been independently and successfully implemented into these two schemes. The operating principles, experimental setup, and overall performance are discussed.
    Optics Express 10/2009; 17(21):18501-12. DOI:10.1364/OE.17.018501 · 3.49 Impact Factor
  • A. C. L. Wong · H. Y. Fu · H. Y. Tam · C. Lu
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    ABSTRACT: For the first time, discrete wavelet transform (DWT) is used for the demultiplexing of photonic crystal fibre Sagnac interferometric sensors. This DWT technique was demonstrated experimentally through pressure measurements with sensors multiplexed in series.
  • Source
    P. Childs · A.C.L. Wong · Gang Ding Peng
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    ABSTRACT: The performance of a strain sensor system based on the use of carrier-modulated gratings and Fourier-domain decoding is analyzed. For three sensors, Young's modulus is measured as 69.98 ± 0.27, 69.15 ± 0.81, and 70.65 ± 0.58 GPa. Crosstalk is shown to exist only when two sensors are designed with an overlap of the carrier band in the Fourier domain. Improving the data processing shows it is possible to limit this crosstalk to a value below that of the system error.
    Journal of Lightwave Technology 04/2006; 24(3):1388- 1394. DOI:10.1109/JLT.2005.863323 · 2.97 Impact Factor