In this paper we present experimental results of measurements of the lens thickness carried out using all fiber low coherence interferometer. A new interferometric device for measuring the thickness of the lens using optical fibers has been developed in response to market demand. It ensures fast, non-contact and accurate measurement. This work focuses above all on the conducting tests to determine the repeatability of the measurement and to verify the ability of using this method in industrial conditions. The system uses a Mach-Zehnder interferometer in which one of the arms is the reference part and the second arm containing the test element is the measurement part. The measurement rate and the easiness of placement of the test lens in the system give the possibility to automate the measurement process. We present the measurement results, which show that the use of low-coherence interferometry allows achieving high measurement accuracy and meeting other industrial needs.
In this paper we present the idea and test results of an all-fiber unbalanced Mach-Zehnder interferometer for fiber Bragg grating shift demodulation. The interferometer design allows to monitor Bragg wavelength changes (caused by temperature or strain variations) as changes of intensity on the output detector. Furthermore the construction is cost-effective and based on simple optoelectronic components, which makes the solution attractive for application as a low cost fiber Bragg grating interrogator.
In this paper we present a fiber Bragg grating shift demodulator with changeable resolution based on an unbalanced fiber Mach–Zehnder interferometer. Preliminary research proves phase sensitivity to Bragg wavelength changes of 6,83 rad/mε. Phase sensitivity can be modified by changing the optical path difference witch is only limited by the coherence length of light reflected by the fiber Bragg grating. This solution can be used as a single sensor or as a part of a more complex system.
In this work we present a novel highly Ge doped microstructured fiber design dedicated for fiber Bragg grating (FBG) inscription and longitudinal strain sensing. Three series of the reported fiber differentiated by air-hole diameters were drawn and presented. After numerical analysis of the propagation conditions (with effective refractive index, loss and mode area calculated) in the real structures, the fibers were subjected to femtosecond FBG inscription. We show the resulting typical FBG spectra, as well as measure the longitudinal strain sensitivity of the fabricated samples and its dependence on the microstructure geometry. An increase of approx. 4% in the Bragg wavelength strain sensitivity was noticed for an increase of the large air-hole diameter of approx. 10%.
Microstructured optical fibers (MOF) sometimes also referred to as photonic crystal fibers (PCF) have been a subject of extensive research for over a decade. This is mainly due to the fact that by changing the microstructure geometry (e.g. distribution and size of the air-holes) fiber properties can be significantly modified to better fit specific applications. In this manuscript we present a novel fiber design with three large air-holes neighboring the core and report on how the air-hole diameter influences the effective refractive index strain sensitivity. As direct measurement of the effective refractive index change may be complex and challenging, we propose to use fiber Bragg gratings (FBG) in our sensing set up. The Bragg wavelength is a function of the effective refractive index, hence the external strain changes can be monitored through the Bragg wavelength shift with a simple optical spectrometer. Furthermore we also include an analysis of the fibers temperature sensitivity.