Soliton self-frequency shift (SSFS) is a phenomenon that Raman self-pumping continuously transfers energy from higher frequency components of optical pulse to its lower frequency components. It has been explored over the last decades, because it has many potential applications in the fields of all-optical wavelength conversion, ultra-fast all-optical switch, all-optical de-multiplexing and so on. In this paper, Firstly, using split-step Fourier method for numerical simulation, it has been found that the soliton self-frequency shift increases with the increase of soliton peak power and nonlinear coefficient of the transmission fiber, and decreases with the increase of soliton width and group velocity dispersion. At the same time, third order dispersion is taken into account, which has a significant inhibitory effect on soliton selffrequency shift. Secondly, according to the existing conditions in the laboratory, self-frequency shift in a 2-km-long single-mode fiber has been experimentally studied, especially the influences of soliton peak power and optical fiber dispersion. A continuously tunable self-frequency shift with central wavelength from 4.29 nm to 43.25 nm has been achieved by adjusting the peak power of the soliton. It has been shown that the soliton self-frequency shift can be effectively tuned by flexibly adjusting the related parameters, which provides guidance for many practical applications of soliton self-frequency shift.
In recent years, optical fiber communication system has made a great development, but the quality of the optical signal will be seriously deteriorated by some factors, such as amplified spontaneous emission (ASE) noise, group velocity dispersion and so on. The traditional regeneration technology is accomplished within the electrical domain, and the opticalelectrical-optical conversion consumes vast amounts of energy. So it is necessary for all optical regeneration technology. This paper introduces the principle of an all-optical 2R regenerator based on self-phase modulation(SPM) and offset filtering technology. The deteriorated optical signal at 40 Gbit/s has been regenerated by the combination of SPM in highly nonlinear fiber (HNLF) and offset filtering. The factors influencing the regeneration have been analyzed by changing related parameters. It is concluded that by reasonably choosing parameters, we can get the best result of all-optical 2R regeneration.
A tunable dual-wavelength passively mode-locked thulium-doped fiber laser (TDFL) based on single-wall carbon nanotube is demonstrated. By properly tuning the pump power and the polarization controller, both single- and dual-wavelength mode-locked operation can be achieved. The repetition rates of the single- and dual-wavelength mode-locked operation are both 17.64 MHz. The duration of the ultrashort soliton pulse is about 3.7 ps. By appropriately adjusting the polarization state of the laser, the dual wavelength can be tuned from 1879.8 and 1894.5 nm to 1903.3 and 1914.1 nm.
A method for tuning the chirp ratio of a fiber grating without the central wavelength shift is proposed by using a two-fixed-end compressive beam, which induces a linear strain distribution along the grating. This technique allows dynamic control of the grating’s chirp ratio by changing the displacement of the translation stage. The 3-dB bandwidth tuning range is from 6.52 to 13.5 nm when the grating is tuned in the broadening way, while the bandwidth tuning range is from 6.52 to 0.95 nm in the compressing way. The proposed method has potential applications for the dynamic dispersion compensation and the sensors of pressure and displacement, etc., by detecting the change of bandwidth information.
In this work an all-fiber linearly-polarized Yb-doped double-clad fiber laser is proposed, in which the resonance cavity is
composed of a pair of polarization maintaining fiber Bragg gratings (PM-FBGs). The polarization hole burning is
enhanced by the selective polarization feedback by the PM-FBGs. A three-port polarization beam splitter with fiber
pigtail was inserted into the laser cavity to select different polarization states. The laser features wavelength of 1069.72
nm and 1069.98 nm, output power of 125 mW, SNR of 45 dB, slope efficiency of 52%, as well as linewidth of 30.7 pm.
The polarization characteristics of the laser are studied by measuring the laser power transmitted through a rotating Glan-
Thomson polarizer. The degree of polarization of each lasing line is over 12 dB under different pump levels.
This paper investigates the performances of 16×100Gbit/s return-to-zero differential quadrature phase shift keying (RZDQPSK)
coded modulation signals in dense wavelength division multiplexing (DWDM) system and compares three
different dispersion compensation fiber (DCF) methods. The performance has been evaluated by using Q value as the
major parameter along with the variation of the input power for different channels with different dispersion
compensation schemes. It is observed that symmetrical compensation of DCF is more excellent than pre-compensation
and post-compensation methods. Corresponding to symmetrical compensation of DCF method, the maximum values of
Q factor are 11.7026, 10.5128 and10.5138 for channel NO.1, channel NO.8, and channel NO.16, respectively.
Meanwhile, the eye diagram shape of symmetrical compensation method is superior to the others.
A multi-channel tunable mechanically induced long-period fiber gratings (LPFGs) scheme is presented, which can
induce several LPFGs with different resonance wavelengths simultaneously. LPFGs spectra characteristics are simulated
to find the influence of these parameters such as grating length, tilt angle and the pressure on the fiber. The simulation
results show that the transmission loss peak mainly depends on both the grating length and the pressure, while tilt angle
factor dominates the resonant wavelength. The infuence of the pressure and tilt angles on the transmission spectra is
experimentally studied. This multi-channel LPFGs module will have great potential applications in the fiber sensing field
and flexible filter design region.
Symmetrical apodization technique of the chirped fiber Bragg grating has the advantages of suppressing the sidelobes of
reflection spectra and smoothing the curves of group delay. However, it shortens the bandwidth of the reflection
spectrum markedly. Compared with symmetrical apodization method, the asymmetric method can increase the 3dB
bandwidth by 64.08% without the change of group delay curves. The apodization simulation is implemented by using a
rised cosine function with different apodization length ratios at both ends of the grating. There is a compromise between
the bandwidth and the group delay ripple. The result shows that the grating with 30% apodization at the long wavelength
end and 20% apodization at the short wavelength side can improve the reflection bandwidth effectively and depress the
group delay ripple within the range of ±2 ps.
The distributed optical fiber temperature measurement system (DTS) is a kind of sensing system, which is applied to the
real-time measurement of the temperature field in space. It is widely used in monitoring of production process: fire alarm
of coal mine and fuel depots, heat detection and temperature monitor of underground cable, seepage and leakage of dam.
Through analyzing temperature effect of optical fiber Raman backscattering theoretically, a distributed temperature
sensor based on single-mode fiber was designed, which overcame the inadequacies of multimode fiber. The narrow pulse
width laser, excellent InGaAS PIN, low noise precision difet operational amplifier and high speed data acquisition card
in order to improve the stability of this system were selected. The demodulation method based on ratio of Anti-Stokes
and Stokes Raman backscattering intensity was adopted. Both hardware composition and software implementation of the
system were introduced in detail. It is proved that its distinguishing ability of temperature and space are 1 m and 2 m,
respectively. The system response time is about 180 s, with a sensing range of 5 km and the temperature measurement
range 0~100 °C.
VoD is a very attractive service which used for entertainment, education and other purposes. In
this paper, we present an evolution method that integrates the EPON and SCM-PON by WDM
technology to provide high dedicated bandwidth for the metropolitan VoD services. Using DVB,
IPTV protocol, unicasting and broadcasting method to maximize the system throughput and by
numerical analysis, the hybrid PON system can implement the metropolitan VoD services.
Through a two laser beams interference method, holographic gratings were successfully fabricated in Polyacrylic Acid
binder photopolymer (PAA). The real-time dynamic fabrication process of the grating was monitored by a He-Ne laser
which was used as the probe light. During the heat treatment process of grating, the refractive index modulation and
hence the diffraction efficiency will change. Firstly, the gratings were fabricated under different temperature; secondly,
the dynamic change of diffraction efficiency of holographic grating with temperature was investigated just after
fabricating it at room temperature. The change range of temperature in experiments was from 25°C to 100°C. We found
there was one optimal temperature value for each kind of photopolymer. The surface topographical change of
Photopolymer film was also investigated by atomic force microscope(AFM). The results and concerned discussion will
help to design and synthesize the highly functional Photopolymer that can show better environmental stability.