Study of transmission response of edge filters employed in wavelength measurements.

Applied Optoelectronics Centre, School of Electronics and Communications Engineering, Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland.
Applied Optics (Impact Factor: 1.69). 01/2006; 44(36):7789-92. DOI: 10.1364/AO.44.007789
Source: PubMed

ABSTRACT The ratiometric wavelength-measurement system is modeled and an optimal design of transmission response of the employed edge filter is demonstrated in the context of a limited signal-to-noise ratio of the signal source. The corresponding experimental investigation is presented. The impact of the limited signal-to-noise ratio of the signal source on determining the optimal transmission response of edge filters for a wavelength-measurement application is shown theoretically and experimentally.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This thesis describes theoretical and experimental investigations on all-fibre multimode interference (MMI) devices using a singlemode-multimode-singlemode (SMS) fibre structure for use as a new type of edge filter for a ratiometric wavelength measurement system and as novel stand alone sensors. The use of two edge filters, so called X-type edge filters based on SMS fibre structures in a ratiometric wavelength measurement system is proposed and demonstrated. The use of X-type edge filters can improve the resolution and accuracy of wavelength measurement compared to the use of one edge filter in a conventional ratiometric system. Several aspects of the SMS edge filters have been investigated, including the effect of misalignment the SMS fibre cores due to fabrication tolerances, polarization dependence, and temperature dependence. These aspects can impair the performance of a ratiometric wavelength measurement system. Several approaches have been proposed and demonstrated to achieve high resolution and accuracy of wavelength measurement. Misalignment effects due to the splicing process on the spectral characteristics and PDL of SMS fibre structure-based edge filters are investigated numerically and experimentally. A limit for the tolerable misalignment of the cores of an SMS fibre structure-based edge filter is proposed, beyond which the edge filter’s spectral performance degrades unacceptably. It is found that a low PDL for an SMS fibre structure-based edge filter can be achieved with small lateral core offsets. Furthermore, the rotational core offsets position is proposed to minimize the PDL. Analysis of the temperature dependence of SMS X-type edge filters is presented. The temperature variation in the system can be determined and compensated by using an expanded ratiometric scheme with an additional reference arm. New sensing applications of multimode interference in an SMS fibre structure are proposed and demonstrated as a temperature sensor, a voltage sensor based on the strain effect, and a strain sensor with very low temperature dependence. All the sensors utilize a simple intensity-based interrogation system using a ratiometric power measurement system. It is found that the temperature and strain characteristics of SMS fibre structures are linear in nature and can be used for temperature and strain sensors. Based on the strain effect in an SMS fibre structure, a voltage sensor is also proposed. The SMS fibre structure is attached to a piezoelectric (PZT) stack transducer. The displacement of the PZT due to the voltage induces a strain on the SMS fibre structure and in turn results in a change in the ratio response. Finally, a strain sensor with very low temperature induced strain measurement error is investigated. For this purpose two SMS fibre structures were proposed and demonstrated in a ratiometric power measurement scheme, one SMS structure acts as the strain sensor and the other SMS structure acts as the temperature monitor. The use of this configuration can effectively minimize the temperature induced strain measurement error.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An investigation of temperature-induced instabilities in a wavelength measurement system based on macro-bend fiber filter used in the ratiometric scheme are presented. Two wavelength measurement systems based on macro-bend fiber, a standard low bend loss single-mode fiber filter based system and a high bend loss fiber filter based system are considered. In the case of a low bend loss fiber filter based system, the oscillatory variation in the ratio response with temperature and the difference in the temperature-induced ratio variation at different wavelengths makes the temperature corrected calibration of the system unfeasible, which is essential for precise wavelength measurements. The high bend loss fiber filter based system is more sensitive to temperature than the low bend loss fiber filter based system, but critically for the high bend loss fiber filter based system the ratio has a linear variation with temperature, which can be corrected by a suitable temperature calibration process. Comprehensive studies on the temperature dependence of both the macro-bend fiber filter system and its effect on wavelength measurements are presented in this paper.
    Journal of Lightwave Technology 05/2009; 27(10):1355-1361. · 2.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The sloshing impact induced strain exerted on the insulation panel of a liquefied natural gas (LNG) tank was measured in situ by using a fiber-optic Bragg reflector and a wavelength interrogator. To prevent the catastrophic failure of the LNG vessel caused by sloshing impact on the insulation panel, continuous monitoring and dynamic analysis of the induced strain are required. In this study, two different fiber-optic systems are developed based on (1) edge filter type and (2) arrayed waveguide grating type. Bragg reflection sensors were embedded inside the reinforced polyurethane foam insulating panel, which was used to cover the inner surface of the LNG tank. Initially, an edge filter type fiber-optic system is attempted for measuring strain for high speed applications. Another type of fiber-optic system, arrayed waveguide grating, is developed. By incorporating an arrayed waveguide grating device for the interrogation of the reflected wavelength from the Bragg reflector, a dynamic strain of 4000 µε occurring within a duration of 10 ms was able to be measured in real time. The accuracy of the measured data was confirmed by comparing it to the data obtained by means of a high speed camera.
    Journal of Intelligent Material Systems and Structures 01/2010; 21(8):787-796. · 1.52 Impact Factor

Full-text (2 Sources)

Available from
May 29, 2014