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K. Ramachandran

Bio: K. Ramachandran is an academic researcher from University of Mississippi. The author has contributed to research in topics: Interferometry & Optical amplifier. The author has an hindex of 4, co-authored 9 publications receiving 31 citations. Previous affiliations of K. Ramachandran include University of Hyderabad & Indian Institutes of Information Technology.

Papers
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Journal ArticleDOI
TL;DR: In this article, a perturbation term has been inserted in the expression for free spectral range and formula for shift in the fringes, due to rise in temperature of the fiber, in order to accommodate the effect of interference among the higher order cladding modes.
Abstract: Earlier reported micro-Mach-Zehnder interferometer (MMZI) sensors, fabricated by concatenation of tapered fibers, considered the interference between LP01 and LP02 modes only for generating the fringe pattern. However, the experimental studies evidenced aperiodic and nonsinusoidal spectral response, which may be attributed to the occurrence of interference among higher order cladding and LP01 and LP02 modes enroute the interference region. In order to accommodate the effect of interference among the higher order cladding modes, a perturbation term has been inserted in the expression for free spectral range and formula for shift in the fringes, due to rise in temperature of the fiber, in this paper. Furthermore, three samples of in-house fabricated MMZIs, placed over a direct current carrying power resistor, senses the temperature produced due to emanation of Joule's heat and resulted into shift in the output fringe pattern. The effect of change in temperature/current is displayed as shift in the output spectrum, recorded on an optical spectrum analyzer, in accordance with the amended equations. The fabricated sample demonstrates the higher current sensitivity 1.76 nm/A 2 with the regression/correlation coefficient (R 2 ) value 0.99.

10 citations

Journal ArticleDOI
TL;DR: In this paper, an all-fiber interferometric technique for gain flattening of amplitude spontaneous emission (ASE) response of an erbium doped fiber amplifier (EDFA) is presented.

10 citations

Journal ArticleDOI
TL;DR: In this article, a simple Sagnac interferometer based all-fiber technique has been proposed for dynamic maneuvering of wavelength response of any type of filter so as to match the desired spectral pattern as intended before fabrication of the gadget.
Abstract: Post fabrication spectral tuning of an all-fiber wavelength filter is a pertinent challenge that needs to be resolved before the filters integration into the communication link. A simple Sagnac interferometer based all-fiber technique has been proposed for dynamic maneuvering of wavelength response of any type of filter so as to match the desired spectral pattern as intended before fabrication of the gadget. The method would prove its usefulness in obtaining preferred position of the wavelength notch, depth of the notch, full width at half maxima from the filter even after its fabrication and thus, mitigates the deleterious effects of departure from the deliberated spectrum. The wavelength response of an all-fiber Mach–Zehnder interferometer has been dynamically manipulated after its fabrication and a gain equalized filter has been realized by employing the projected process. As an application, amplified spontaneous emission of an erbium doped fiber has been flattened over a range of 35 nm within an accuracy of ± 0.26 dB in the C-band.

7 citations

Journal ArticleDOI
TL;DR: In this paper, a miniaturized micro Mach-Zehnder interferometer (MMZI) was employed for gain equalization of amplified spontaneous emission spectrum of an erbium doped fiber.

5 citations

Journal ArticleDOI
TL;DR: The study reveals that a small quantity of PEDOT is sufficient to initiate the positive charge transfer mechanism between its oxidized state to the lone pairs of electrons on the oxygen atoms of the nitro group of the explosive molecules, and the intensity of the Raman spectra of RDX, HMX and TNT is dropped.

4 citations


Cited by
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Posted Content
06 Apr 2006
TL;DR: In this paper, a heat-and-pull rig is proposed for fabricating adiabatic tapers with 3-4μm diameter, where a CO2 laser is continuously scanned across a length of fiber that is being pulled synchronously.
Abstract: We describe a reproducible method of fabricating adiabatic tapers with 3–4μm diameter. The method is based on a heat-and-pull rig, whereby a CO2 laser is continuously scanned across a length of fiber that is being pulled synchronously. Our system relies on a CO2 mirror mounted on a geared stepper motor in order to scan the laser beam across the taper region. We show that this system offers a reliable alternative to more traditional rigs incorporating galvanometer scanners. We have routinely obtained transmission losses between 0.1 and 0.3dB indicating the satisfactory production of adiabatic tapers. The operation of the rig is described in detail and an analysis on the produced tapers is provided. The flexibility of the rig is demonstrated by fabricating prolate dielectric microresonators using a microtapering technique. Such a rig is of interest to a range of fields that require tapered fiber fabrication such as microcavity-taper coupling, atom guiding along a tapered fiber, optical fiber sensing, and th...

121 citations

Journal ArticleDOI
Shao-cheng Yan1, Bi-cai Zheng1, Jin-hui Chen1, Fei Xu1, Yan-qing Lu1 
TL;DR: In this article, a microfiber-graphene-integrated device has been proposed for monitoring electrical current with a high sensitivity of 67.297μm/A2.
Abstract: A graphene-based electrical current sensor is proposed utilizing a microfiber coil resonator. Monolayer graphene sheet with a large sheet resistance is transferred onto the surface of a glass capillary rod. A microfiber is spirally wrapped around the graphene sheet to form a coil resonator. Heat generated from electrical current shifts the resonant wavelength because of the thermal effect in the microfiber resonator. The sensor exhibits a very good performance with a high sensitivity of 67.297 μm/A2, which is two orders of magnitude higher than that reported earlier. Our results show that microfiber-graphene-integrated devices have great potential for miniature and highly sensitive fiber sensors for monitoring electrical current.

44 citations

Journal ArticleDOI
TL;DR: In this paper, a practical single-fiber Mach-Zehnder interferometer (SF-MZI) based weight sensor has been proposed and experimentally demonstrated and a novel mathematical basis corroborating the shift in the output fringe pattern with applied weight placed on its interference region has been substantiated.
Abstract: A practical single-fiber Mach-Zehnder interferometer (SF-MZI) based weight sensor has been proposed and experimentally demonstrated. Considering the two modes interference, a novel mathematical basis corroborating the shift in the output fringe pattern of SF-MZI with applied weight placed on its interference region has been substantiated. Further, a correlation between the average induced birefringence, due to loading of interferometer, and the applied weight has been suggested theoretically and endorsed experimentally for the first time for the suggested scheme. The sensitivity of the proposed configuration was observed to be 112 pm/gm for the applied weights ranges from 0 to 100 gm. For the same weight ranges, the sensitivity of the interferometer, was enhanced, by placing it between phase shifters (PSs) inserted in Sagnac interferometer, to 183 pm/gm and 151 pm/gm, respectively.

9 citations

Journal ArticleDOI
TL;DR: In this article, a novel technique to enhance the sensitivity of single-fiber (SF) MZI-based refractive index sensor is presented, where an indigenously fabricated SF-MZI has been placed in MZI cascaded fiber loop mirror (FLM) and its sensitivity is enhanced from 20.24nm/RIU to 40.92nm/RU over a relatively large range from 1.3344 RIU to 1.4532 RIU.

8 citations

Journal ArticleDOI
TL;DR: An optical fiber inclinometer based on non-reciprocal phase change effect in a single-mode fiber loop mirror (FLM) is proposed in this paper, where the phase of light waves in FLM is controlled by two-phase shifters (PSs).
Abstract: An optical fiber inclinometer based on non-reciprocal phase change effect in a single-mode fiber loop mirror (FLM) is proposed. The phase of light waves in FLM is controlled by two-phase shifters (PSs). The relationship between the inclination angles and phase differences of the two-PSs, and transmitted light power was derived by Jones calculus. The signature of the birefringence obtained through simulation on the output light has been confirmed by experimentation. From the results, it was found that when the birefringence of the two-PSs are different, two measurement sensitivities (17.07 × 10−3 deg−1 and 21.37 × 10−3 deg−1) can be realized with one angle measurement system. We also report a method for changing measurable ranges, and measurement sensitivity. Since the angle can be directly measured from the transmitted light power, the results of this work contribute to the realization of simple and low-loss inclinometers using standard single-mode fiber.

8 citations