One 160 Gb/s optical time division demultiplexer based on two cascaded electro-absorption modulators
as sampling windows was demonstrated and experimentally studied in detail. The two stages were used
for the 160 Gb/s into 40 Gb/s demultiplexing and 40 Gb/s into 10 Gb/s demultiplexing respectively.
Temporal imaging is one of the important research issues using time-lens. The theory of
temporal imaging using time lens is discussed briefly. The experiment to perform optical pulses
compression is demonstrated and the problem is further discussed by numerical simulation in this article.
The single sideband (SSB) modulation format is obtained using the narrowband fiber Bragg grating (NFBG) made by
ourselves. Then The SSB modulation format and double sideband (DSB) modulation format transmit over 155 km G.652,
respectively. And dispersion is compensated by chirp fiber Bragg grating (CFBG) made by us. The results show that the
power penalty of SSB signal is smaller than that of DSB signal when the input power and the bit error rate (BER) are the
same; when the BER is E-12, the power penalty of SSB signal is 0.8 dB smaller than that of DSB signal.
The effect of non-ideal dispersion and reflection characteristics of chirped fiber Bragg gratings (CFBG)
on the 40-Gb/s and 10-Gb/s transmission is investigated. The effect of group delay ripple (GDR) on
eye-opening penalty (EOP) of carrier-suppressed return-to-zero (CSRZ) and return-to-zero (RZ)
formats is analyzed and compared. The system penalty for different amplitude and period ripples are
quantified.
A simple multi-wavelength erbium-doped fiber laser with narrow-line-width lasing output was proposed and
demonstrated using fiber Bragg gratings and Arrayed-Waveguide Gratings (AWG). Wavelength competition was
naturally prevented in this kind of laser by using AWG in the linear-cavity. As an example, a triple-wavelength erbium-doped
fiber laser was experimentally investigated. Using the laser scheme, the proposed laser can laser three
wavelengths simultaneously. The fiber laser retrieved the optical side-mode suppression ratio of over 50dB and the
average output power of -10.714, -10.649 and -10.578dBm at 1554.710, 1555.516 and 1556.421nm, respectively. And
the 3-dB bandwidth of each laser was less than 0.010nm. Moreover, the output power stability of the laser had also been
measured and analyzed. Experiment results showed that the laser can be operated stably in narrow-line-width with
single- and triple-wavelength output at room temperature.
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.
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).
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.
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 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 transmission characteristics of a nonuniform photonic fiber Bragg grating (PFBG) are studied in detail by FEM
furnished with 1st - order BGT - like TBC and transfer matrix method. The effects of the air hole size on PFBG's
transmission properties such as effective index, Bragg reflective wavelength, normalized bandwidth and centre
wavelength shift are investigated. It is believed the study can provide useful information for PFBG's design and
optimization with a more effective and accurate method.
A novel fibre Bragg grating (FBG) hydrophone system is introduced in the paper. The influence of the sound pressure on
the FBG is transformed to light intensity measurement with tuned laser. Elastic material and matched FBGs are
employed to enhance the sensitivity of the hydrophone system. The hydrophone system can operate in a wide acoustic
frequency range from 100Hz to 3kHz and good linear relationship is observed between the output light intensity and the
sound pressure.
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.
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.
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