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ABSTRACT: An efficient Ytterbium-doped fiber laser (YDFL) operating at 1028 nm is demonstrated using a fiber Bragg grating (FBG). The
Ytterbium-doped fiber (YDF) is drawn from Yb2O3-doped preform, fabricated through deposition of porous layer of composition SiO2-GeO2 by the MCVD process in conjunction with a solution doping technique. The fabricated YDF has a 0.1 mol % of Yb2O3 in the core, a Ytterbium ion lifetime of 1.1 ms, an absorption of 7.65 dB/m at 976 nm. The fiber laser has the maximum efficiency
of 51% with pump power threshold of 19 mW using a FBG in conjunction with a Fresnel reflection to form a linear cavity resonator.
The efficiency and threshold are better compared to the similar YDFL configuration using a commercial YDF.
Laser Physics 04/2012; 19(5):1021-1025. · 3.61 Impact Factor
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ABSTRACT: The performance of a high output power Erbium-Ytterbium doped fiber amplifier (EYDFA) pumped by a 927 nm laser diode are proposed
and experimentally investigated. The EYDFA provides a flat gain and output power higher than 23 dBm in the wavelength region
from 1545 to 1566 nm using a double-pass configuration. A broadband fiber Bragg grating is used in the double-pass EYDFA to
allow a double-propagation of the test signal in the gain medium and thus improves the gain and output power characteristics
of the amplifier. The maximum output power of 390 mW is obtained at the maximum 927 nm pump power of 4.1 W which translates
to a power conversion efficiency of about 10%.
Laser Physics 04/2012; 20(10):1899-1901. · 3.61 Impact Factor
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ABSTRACT: A stable mode-locked fiber laser employing a 49 cm long bismuth oxide based erbium doped fiber (Bi-EDF) by using a slow saturable
absorber is demonstrated. Near transform limited short pulses with a repetition rate of 8.27 MHz are obtained at a wavelength
of 1560 nm with a maximum spectral width of 15 nm. Results indicate that pulse characteristics are strongly dependent on pump
power rather than spectral width. Moreover the Time-Bandwidth products (TBWP), pulse duration, the energy fluctuation and
timing jitter decrease with increasing pump power. The pulse width is continuously varied from 1.2 ps to less than 300 fs.
It produces stable mode locking with a maximum spectral width of 15 nm, minimum timing jitter of 4 ps and energy fluctuations
of 2.5%. The pulse train was amplified using a two-stage amplifier up to 447 mW average power corresponding to peak powers
of 177.3 kW.
Laser Physics 04/2012; 21(5):913-918. · 3.61 Impact Factor
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ABSTRACT: A multiwavelength Ytterbium-doped fiber ring laser operating at 1030 nm region is demonstrated using a Sagnac loop mirror
and a Mach-Zehnder interferometer. We report the Performance comparisons of multi-wavelength oscillations in Yb3+ doped fiber lasers (YDFL) with typical commercial ytterbium doped silica fibers. By adjusting the polarization controller
(PC), a widely tunable laser range of 22 nm from 1030 nm to 1050 nm is obtained. The Mach-Zehnder interferometer (MZI) design
has exhibited simplicity in the operation for controlling the smallest wavelength spacing compared to Sagnac loop mirror method.
In our observations, the smallest achieved stable wavelength spacing in Sagnac loop mirror setup and MZI setup were 2.1 nm
and 0.7 nm, respectively. In case of nine-wavelength operation with a MZI setup, the stability, Full Width at Half Maximum
(FWHM) and side mode suppression ratio (SMSR) of laser lines are not affected by increasing pump power, While for above four
wavelength operation, the laser stability with Sagnac loop mirror becomes worse specially for higher input pump power and
the power fluctuation among the wave-lengths would be also slightly larger.
Laser Physics 04/2012; 20(2):516-521. · 3.61 Impact Factor
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ABSTRACT: Highly efficient laser action from an Ytterbium-doped fiber (YDF) is demonstrated using a fiber Bragg grating (FBG) in conjunction
with a 4% Fresnel reflection at room temperature. The YDF used is drawn from Yb2O3-doped preform, fabricated through deposition of porous layer of composition SiO2-GeO2 by the MCVD process in conjunction with a solution doping technique. The fabricated YDF has a core composition of 0.2 wt
% of Yb2O3, 1.8 wt % of Al2O3 and 23 wt % of GeO2 with a pump absorption of 9.0 dB/m. The fiber laser operates at wavelength of 1028 nm with a slope efficiency of 88% with
respect to the launched 976 nm pump power using the YDF length of 7 m.
Laser Physics 04/2012; 20(3):656-660. · 3.61 Impact Factor
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ABSTRACT: We propose and experimentally demonstrate a triple-wavelength fiber ring laser using a semiconductor optical amplifier (SOA)
in conjunction with a series of fiber Bragg gratings (FBGs). The three channels operate at 1554.4, 1555.3, and 1556.1 nm with
a peak power above −25 dBm and optical signal-to-noise (OSNR) above 30 dB at SOA drive current of 350 mA under the room temperature.
The proposed laser configuration has the advantages of a simple and compact structure, multi-wavelength operation and the
system can be upgraded to generate more wavelengths by increasing the number of FBG used.
Laser Physics 04/2012; 19(5):1002-1005. · 3.61 Impact Factor
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ABSTRACT: We experimentally demonstrate a simple structure but efficient multi-wavelength erbium-doped fiber laser (EDFL) using a 49
cm Bismuth-based erbium-doped fiber (Bi-EDF) as gain medium. The Bi-EDF provides erbium amplification and FWM effect in the
cavity to generate a stable multi-wavelength comb operating in C-band region. We have achieved more than 5 lines with peak
power of more than −35 dBm and channel spacing of 0.5 nm by incorporating a broadband fiber Bragg grating and polarization
controller in the ring cavity.
Laser Physics 04/2012; 20(6):1414-1417. · 3.61 Impact Factor
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ABSTRACT: An experiment on gain enhancement in the long wavelength band erbium-doped fiber amplifier (L-band EDFA) is demonstrated using
dual forward pumping scheme in double-pass system. Compared to a single-stage single-pass scheme, the small signal gain for
1580 nm signal can be improved by 13.5 dB. However, a noise figure penalty of 2.9 dB was obtained due to the backward C-band
ASE from second stage and the already amplified signal from the first pass that extracting energy from the forward C-band
ASE. The maximum gain improvement of 13.7 dB was obtained at a signal wavelength of 1588 nm while signal and total pump powers
were fixed at -30 dBm and 92 mW, respectively.
Pramana 04/2012; 61(1):93-97. · 0.57 Impact Factor
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ABSTRACT: The effect of output coupler reflectivity (or output coupling ratio) on the performance of a linear cavity Brillouin/erbium
fiber laser (BEFL) is demonstrated. The operating wavelength, output laser power and number of channels vary with changes
in the coupling ratio in the linear cavity system. The optimum BEFL operation is obtained with an output coupling of 40%,
i.e., 60% of the laser power is allowed to oscillate in the cavity. A stable laser comb consisting of up to 40 channels with
line spacings of approximately 0.09 nm are obtained at the Brillouin pump and 980 nm pump with powers of 2.5 mW and 100 mW,
respectively. The linear cavity BEFL has the potential to be used in inexpensive wavelength division multiplexing system.
Pramana 04/2012; 68(3):451-456. · 0.57 Impact Factor
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ABSTRACT: We propose and demonstrate a tunable S-band multiwavelength Brillouin/Raman fiber laser (MBRFL) with a tuning range of between 1490 to 1530 nm. The proposed MBRFL is designed around a 7.7 km long dispersion compensating fiber in a simple ring configuration, acting as a nonlinear medium for the generation of multiple wavelengths from stimulated Brillouin scattering (SBS) and also as a nonlinear gain medium for stimulated Raman scattering (SRS) amplification. A laser source with a maximum power of 12 dBm acts as the Brillouin pump (BP), while two 1420 nm laser diodes with a total power of 26 dBm act as the Raman pumps (RPs). The MBRFL can generate a multiwavelength comb consisting of even and odd Stokes at an average power of -12 dBm and -14 dBm respectively, and by separating the even and odd Stokes outputs, a 20 GHz channel spacing is obtained between two consecutive wavelengths. Due to the four-wave mixing (FWM) effect, anti-Stokes lines are also observed. The multiwavelength comb generated is not dependent on the BP, thus providing high stability and repeatability and making it a highly potential source for many real-world applications. This is the first time, to the knowledge of the authors, that a tunable MBRFL has been developed using SRS to obtain gain in the S-band region.
Applied Optics 04/2012; 51(11):1811-5. · 1.41 Impact Factor
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Optics & Laser Technology. 01/2012;
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ABSTRACT: A low-cost microfibre knot resonator (MKR) is fabricated and the resonant wavelength tunability characteristic of this device is investigated and demonstrated. The spacing of the transmission comb spectrum is unchanged with the temperature, but the resonant wavelength linearly shifts with the temperature change at a slope coefficient of 50.6 pm/ C. The resonant wavelength can also be tuned by applying electric current to the copper wire, which is fastened by the microfibre knot. This is attributed to the thermally induced optical phase shift in the MKR caused by the heat produced by the flow of the electric current over a short transit length. The authors analysis indicates that the wavelength shift is linearly proportional to square of the current and the maximum tuning slope achieved is 51.3 pm/A<sup>2</sup>.
IET Optoelectronics 01/2012; · 1.03 Impact Factor
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ABSTRACT: a b s t r a c t A compact current sensor using a microfiber knot resonator (MKR) is demonstrated. With the assistance of a copper wire that is wrapped by the microfiber knot, resonant wavelength inside the MKR can be tuned by applying electric current to the copper wire. The resonant wavelength change is based on the thermally induced optical phase shift in the MKR due to the heat produced by the flow of electric current over a short transit length. It is shown that the wavelength shift is linearly proportional to the square of the amount of current and the maximum tuning slope of 51.3 pm/A 2 is achieved using a newly fabricated MKR.
Sensors and Actuators 10/2011;
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ABSTRACT: A high output power and narrow linewidth Brillouin fibre laser source is demonstrated with an output power of 400 mW by a master-oscillator/power-ampliner system. The laser has a linewidth of 10 kHz, optical signal-to-noise ratio of 45 dB, cladding pumping power threshold of 300 mW and a tunable output from 1548.5 to 1565 nm. The slope efficiency of 1557.4 nm signal improves from 8.7 to 12% with the increase of the input signal power from -10 to 5 dBm.
IET Optoelectronics 09/2011; · 1.03 Impact Factor
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ABSTRACT: This paper describes innovations within a set of assistive tools and technologies for system integration, deployment, monitoring, and maintenance of ocean energy devices (wave energy converters and tidal turbines). These tools comprise of simulation, modelling, control and visualisation tools, including modelling of ocean waves, currents, surface and submerged energy converters, marine platforms and supporting vessels (ships and ROVs). The flexible design of these tools enables their use as separate standalone modules, as well as their integration into a unique integrated system. Four main innovations of the proposed system are 2D Advanced Topview Display, Advanced Pilot Interface, 3D Real-Time Augmented Reality Display and Advanced Control System with Fault-Tolerant Capabilities. System validation and technology demonstration was performed through a series of test trials with different ROVs and support vessels off the west coast of Ireland, in Galway Bay and Shannon Estuary. Selected results of these trials are presented in this paper.
OCEANS, 2011 IEEE - Spain; 07/2011
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ABSTRACT: A passively mode-locked fiber ring laser is demonstrated using a 49 cm long bismuth oxide based erbium-doped fiber (Bi-EDF) and a fast semiconductor saturable absorber. Stable and clean short pulses are achieved because of these short and high nonlinear characteristics of the Bi-EDF. The laser operates at 1560 nm with a repetition rate of 8.3 MHz and a center wavelength of 1560 nm. The calibrated auto-correlator pulse trace of the laser shows a sech2 pulse shape, with an estimated pulse width of 340 fs. (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters 04/2011; 8(6):449 - 452. · 9.97 Impact Factor
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ABSTRACT: Supercontinuum generation with considerable flatness and low fluctuation is investigated in nonlinear fibers by amplification of pulsed seed signal of a stable mode locked bismuth oxide based erbium doped fiber laser. Spectral expansion from 980 to 1750 nm is obtained by 340 fs pulses at 1560 nm amplified up to 177 kW in a dispersion flattened highly nonlinear fiber. A comparison is made for different types of nonlinear fibers and evaluation of spectral bandwidth at high powers is probed. (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) (© 2011 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters 02/2011; 8(5):369 - 375. · 9.97 Impact Factor
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ABSTRACT: A tapered fiber is fabricated by heating and stretching a piece of optical fiber after the polymer protective cladding has been removed. An equidistant comb-like transmission spectrum, with a spacing of 1.6 nm and an extinction ratio of more than 5 dB, was obtained by the tapered fiber due to the multibeam interferences of the cladding modes. The tapered fiber was applied in a ring erbium-doped fiber laser (EDFL) to generate dual-wavelength lasing oscillations. The EDFL operates at wavelengths of 1557.0 nm and 1558.6 nm with a stable peak power and a signal-to-noise ratio of more than 40 dB.
Journal of Modern Optics 12/2010; 57(21):2111-2113. · 1.17 Impact Factor
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ABSTRACT: In this paper, we examine the H<sub>∞</sub> Filter-based SLAM especially about its convergence properties. In contrast to Kalman Filter approach that considers zero mean gaussian noise, H<sub>∞</sub> Filter is more robust and may provide sufficient solutions for SLAM in an environment with unknown statistical behavior. Due to this advantage, H<sub>∞</sub> Filter is proposed in this paper, to efficiently estimate the robot and landmarks location under worst case situations. H<sub>∞</sub> Filter requires the designer to appropriately choose the noise's covariance with respect to γ to obtain a desired outcome. We show some of the conditions to be satisfy in order to achieve better estimation results than Kalman Filter. From the experimental results, H<sub>∞</sub> Filter performs better than Kalman Filter for a case of bigger robot initial uncertainties. Subsequently, this proved that <sub>∞</sub> Filter can provide another available estimation method for especially in SLAM.
Control Applications (CCA), 2010 IEEE International Conference on; 10/2010
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ABSTRACT: Microscopic aspects of traffic codes for heterogeneous traffic flow are considered to be optimal for the performance of vehicular ad-hoc network. Within the scope of this concept, fluid dynamic model was applied for density estimation of heterogeneous traffic conditions. The effect of jamming density on velocity and density dynamics having influence of safety distance between the vehicles is accordingly presented in this paper. The new approach for density estimation is expected to provide more realistic data about road conditions for implementing vehicular ad- hoc network.
Communication Systems Networks and Digital Signal Processing (CSNDSP), 2010 7th International Symposium on; 08/2010
