Influence of stress area mismatched Panda erbium-doped polarization-maintaining fibre on the birefringence is analyzed
and compared by finite element method and approximate analytical expression educed by the complex variable method
of elasticity with superposition techniques.
The temperature dependence of fluorescence in erbium-doped silica fiber between ~-30 and ~150°C is discussed.
980nm pumping configuration is used in our experiment. 1450nm and 1531nm wavelengths are chosen to calculate the
FIR (fluorescence intensity ratio) at the first time instead of the mostly used wavelengths 525nm and 550nm. It shows
that as the temperature increases, the fluorescence intensity increases obviously at short wavelengths but changes a little
at long wavelengths. The temperature coefficient can achieve ~0.023dB/°C, and its resolution is improved as the
temperature decreases. Because there are many effects in our experiments, so it shows a deviation from the behavior of
simulation.
A new method of fabricating Panda-type photosensitive polarization-maintaining erbium-doped fiber(PM-EDF) is
proposed and demonstrated. A sample of PM-EDF is fabricated using this method and an exhaustive analysis is made
about the characteristics of PM-EDF, the results shows that this method is practicable. Two fiber Bragg Gratings (FBGs)
are written into PM-EDF directly as the lasers reflectors, a three-states-tuned fiber laser is then obtained using a
polarization controller (PC).
Four types of YDFs with different Al3+ concentration and mole content of GeO2 were manufactured and the refractive
index and absorption spectra of these fibers were explored. With the comparison of four YDFs and detailed analyze, it
was found that higher Al3+ concentration leads to more GeO2 volatilization, which results in the refractive index decrease.
Therefore, mole content of GeO2 should be increased when co-doping Al3+ in YDF to maintain numerical aperture.
Meanwhile, the temperature of making porous layer should be controlled exactly to obtain good repetition of Al3+-
codoped YDF as the little change of temperature has little effect on mole content of GeO2 and SiO2 but has great effect
on compactness of porous layer. By drawing the fiber and testing the related parameters, the results show that the
optimum temperature range for making soot layer should between 1440°C and 1480°C where the absorption coefficients
were as high as 620dB/m with better repeatability. Finally, the ratio of GeO2 to SiO2 should be controlled to obtain long
fluorescence lifetime for fabricating highly ytterbium-doped fiber with required numerical aperture.
Some kinds of high birefringence photonic crystal fibers (PCFs) with elliptical inner cladding are analyzed by Galerkin
finite element method with transparent boundary conditions (TBC). Several properties of them, such as the birefringence,
confinement loss and dispersion are deduced and compared .It is shown that PCFs with different elliptical inner cladding
formed by enlarging or diminishing air holes have different properties. High birefringence can be obtained through
intruding the difference of air holes size along orthogonal direction. Enlarged air holes reduce the CL, and increase the
dispersion and dispersion slope; but diminished air holes is reversed.
A new near-elliptic cladding Polarization-maintaining photonic crystal fibre (PM-PCF) with four different hole diameters was proposed. Since the refractive index decreases gradually from x-axis to y-axis, less polarization coupling and high extinction ratio were obtained compared to the conventional PM-PCFs. Secondly, every hole diameter of near-elliptic cladding was optimized to get good performance, considering proper mode field diameter of x-axis and y-axis for better coupling to SLD and smaller confinement loss of the new PCF, high birefringence and high extinction ratio, especially the effects of disturbance on extinction ratio stability. According to series of comparison on different hole diameters and correlation between different holes, the optimum parameters of this new PCF of Λ=2.2μm, d1=2μm, d2=1.1μm, d3=1.7μm and d4=1.2μm were derived. The optimized near-elliptic cladding PCF can obtain both high extinction ratio (>29dB) and good extinction ratio stability (<2dB with ±10% transverse disturbance of d3) which is useful for practical use.
A novel design of M-Profile Ytterbium doped Fibers (YDFs) for high power fiber Lasers was given. The output power
was two times higher than that in standard double-cladding fiber under the same threshold of damage.
A new near-elliptic inner cladding (NEIC) structure of polarization-stable highly birefringent photonic crystal fiber (HB-PCF)
is proposed and analyzed by using a full-vector finite element method (FEM) with anisotropic perfectly matched
layers. From the numerical results it is confirmed that, with the diameter of air hole A varied by ~10%, the modal
birefringence degradations of the three proposed NEIC-PCFs are less than 4.2 × 10-5, 6 × 10-5 and 1.17 × 10-4,
respectively, while the average birefringence is of the order of 2 × 10-3 at 1.55μm, which strongly proves that the
proposed structure is highly polarization-stable. Especially, the MFDs in x-direction and y-direction of NEIC-PCF with
three holes diminished in the center are measured as 5.8 μm and 2.6 μm, respectively, which are very attractive in the
application field of fiber optic sensor, e.g. fiber optic gyros.
The finite element method is applied for solving the modal field of erbium-doped hole-assisted lightguide fiber
(EDHALF). The modified average population inversion iteration method is proposed for simulating the gain coefficients
of EDHALF amplifiers. The relation between the structural parameters of EDHALFs and the gain coefficient of L band
EDHALF amplifiers is investigated by means of the finite element method combined with the modified average
population inversion method. Four structural parameters of EDHALF-core diameter, the refractive index difference
between the core and silica cladding, the relative hole-to-core spacing and the relative size of air holes are optimized in
terms of the design criteria of L band erbium-doped fiber, which take into account the cutoff wavelengths, the gain
coefficients of L band fiber amplifiers and the splice loss between the EDHALF and the conventional single-mode fiber.
At last, the comparisons between the EDHALF and the conventional erbium-doped fiber for L band applications are
made.
The amplification mechanism of ultra-wide-band telluride-based fiber Raman amplifier (T-FRA) is analyzed by
comparing the stimulated Raman scattering (SRS) characteristics of the telluride-based fiber with silica-based fibers.
Then a multi-pumping scheme to get a gain-flattened FRA is presented. We calculate the pump power in designing
multi-wavelength pumped Raman amplifiers by using some optimal searching method such as genic algorithm and an
effective linear multi-steps method based on average power called Adams-Bashforth method is proposed which not
only utilizes former multi-steps known information to get higher accuracy but also avoids iterative scatting by using
forecasting-correcting policy The search time of genic algorithm is about 8 minutes and the calculation time is 2 to 3
minutes. The optimizing process of six pumps can be completed within 20minutes and the time may increase if we use
'shot' method. Furthermore, a complete computing model is established to optimize the pump wavelength and power
allocation with flat net gain and broad bandwidth. As a result, using telluride-based fiber Raman amplifier, the gain
over 10dB from 1500nm to 1620nm (C and L band) is obtained and the gain spectra is more flat especially in C band.
A novel technique for dispersion compensation is presented. Based on the theoretical analysis, an ideal instance of
characteristics of linear chirped fiber Bragg grating (CFBG) with 11 thermal heads and a laboratory instance of
characteristics of the CFBG with 5 thermal heads varies with different temperature is shown. They are analyzed at room
temperature with variation of the decrease from 3°C to -3°C and the increase from -2°C to 2°C. According to the results
of the simulations based on theoretical analysis, the change of micro-heaters temperature will induce the change of
grating temperature, and then change the Bragg wavelength, delay and delay slope of the CFBG. Further more, a
material experiment is presented. These results show that if the temperature controller is good enough, we will be able to
limit the temperature from 0°C to 4°C and we will receive some random dispersion values from -2608.2ps/nm to -
2835.6ps/nm. Therefore, this dispersion compensator can compensate the survival dispersion completely and can be
applied to the long-distance transmission and the optical communication system.
This paper presents a novel technique for dispersion compensation, employing a linear chirped fiber Bragg grating (CFBG) with a thermal head consisting of several micro-heaters. The micro-heaters temperature are controlled by computer, and the change of micro-heaters temperature will induce the change of grating temperature, and the change of Bragg wavelength, and the change of delay and dispersion of the grating. Thereby, the goal of tunable dispersion compensation to different systems dispersion and the survival dispersion has been achieved.
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