We demonstrate an all-fiber picosecond laser with a repetition rate of 1.2 GHz. The seed source is a passively modelocked Yb-doped fiber laser. The pulse width of the seed laser is 4.2 ps with a repetition rate of 19.2 MHz, and the seed exhibits a spectral bandwidth of 3.6 nm at the center wavelength of 1064.1 nm. Due to the length of the cavity, it is difficult to increase the repetition rate of the fiber laser. To solve the above problem, we provide a high-repetition-rate pulsed laser modulator comprising: five 2 × 2 type, splitting ratio 50:50 couplers, two 1 × 2 type, splitting ratio 50:50 couplers, to increase the repetition rate of the seed laser to 1.2 GHz. Meanwhile, the novel combination of the devices can realize a low-loss mutual coupling of laser pulses.
A novel method to compensate dispersion and dispersion slope at the same time by using fiber Bragg grating
written on the tapered core fiber has been presented. The fabrication method about this kind of tapered core fiber has
been realized by precisely controlling the fiber's diameter during the process which is drawing the preform into optical
fiber. The fiber grating written on this kind of fiber has parameter as 3dB bandwidth 0.861nm. Its dispersion value is -
1159ps/nm (within 0.8nm bandwidth), and the dispersion slope is -1.3 ps/nm2. These characteristics of the grating make
it can be used in high speed optical fiber communication systems which need the dispersion and dispersion slope be
compensated at the same time.
The fluorescence intensity ratio (FIR) technique for optical fiber-based temperature sensing is discussed in many
previous papers. But in the high temperature sensing the FIR technique has been researched a little. In this paper, the
temperature dependence of fluorescence in erbium-doped fiber between ~700 and ~1300 °C; is discussed and
experimentally demonstrated. 1450nm and 1530nm wavelengths are chosen to calculate the FIR, and the temperature
coefficient could achieve ~ 0.003dB/°C.
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 high concentration silica host Erbium Doped Fiber with Bismuth-Gallium-Aluminum co-doped was fabricated. The
absorption coefficient of this fiber was up to 19dB/m at the wavelength of 980nm and 42dB/m at 1530nm. Ring structure
lasers with different fiber lengths were presented. Their output characteristics were measured and analyzed.
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.
The relationship between the gain flatness performances with the pump wavelength spacing in single-stage backward-pumped
distributed fiber Raman amplifiers (B-DFRAs) were demonstrated theoretically. It was shown that the gain
spectrum of B-DFRA which pump wavelengths were arranged in a geometric proportion interval sequence were flatter
than one which pump wavelengths were arranged in an equal interval sequence in the same conditions.
KEYWORDS: Polarization, Multiplexers, Feedback signals, Wave plates, Signal attenuation, Telecommunications, Digital signal processing, Optical communications, Optical amplifiers, Control systems
By using thin membrane plating technology in collimating lens, we successfully manufacture a 160Gbit/s time-division multiplexer basing on the combination of fiber and space structure method. The multiplexer is flexible according to your practical need, which can output 20, 40, 80, or 160Gbit/s signal. For 20, 40, 80 or 160Gbit/s multiplexer, insertion losses are 4dB, 6dB, 8dB and 16dB respectively. The low insertion loss provides maximum transmission power. It also has such features: polarization insensitivity, very short coherence length, high time-delay accuracy, and excellent temperature stability. An experiment of two degrees PMD compensation in 160Gbit/s RZ optical communication system is achieved. The PMD monitoring technique is based on DOP as error signal. A practical adaptive optimization algorithm was introduced in dynamic adaptive PMD compensation. The experimental results show the improvement in PMD. With this compensator, a significant improvement of system performance can be achieved by auto-correlative curves. The 2.5ps first-order and 15ps2 second-order PMD are compensated. The PMD compensating time is less than 100ms.
Erbium-doped photonic crystal fiber (EDPCF) is not in the endless single-mode as the refractive index of the core in EDPCF is higher than that of silica cladding. There is a variation between the EDPCF and the conventional PCF. The modified average population inversion iteration method is proposed for simulating the gains and noises of EDPCF amplifiers. The effect of the structural parameters of EDPCF on the cutoff wavelengths, splice loss and the amplification properties is studied in detail by means of the improved average population iterative method combined with the finite element method. According to the design criteria of erbium-doped fiber, the four structural parameters of EDPCF-core radius, the refractive index difference between the core and silica cladding, the relative size of the core and the relative size of air holes are optimized.
The design criteria of the Panda-type erbium-doped polarization-maintaining fiber (EDPMF) are presented, which take into account the cutoff wavelength, mode field diameter, modal birefringence and background loss. The structural parameters are optimized in terms of the design criteria. A Panda-type EDPMF has been manufactured. The fabrication process and the parameter control of the Panda-type EDPMF are in detail described. Its refractive index profile, birefringence and absorption spectra are experimentally investigated.
We demonstrate a 10.7Gb/s-line-rate L-band WDM loop transmission over 1890km standard single-mode fiber (SSMF) with 100km amplifier spacing as well as non-return-to-zero (NRZ) format. For the first time, dispersion compensating fiber (DCF) plus chirped fiber Bragg grating (CFBG) is employed for hybrid inline dispersion compensation. The power penalty of each channel is less than 3dB after three loop transmission. The experimental results show that high-performance-CFBGs can be successfully used in ultra-long haul (>1000km) WDM systems. We also point out that all-CFBG compensation scheme is not suitable for re-circulating loop transmissions.
In this paper we introduce some methods to improve performance of cladding pumped L-band EDFA. C-band seeds, ASE end-reflectors, and hybrid configurations use the cladding pumped fiber and convential EDF have been studied.
The necessity of packaging and the basic principle of temperature compensation package for fiber gratings are expatiated. A method of packaging fiber gratings with the negative temperature coefficient material is introduced, and the temperature characteristic and long-term stability of packaged fiber gratings are measured. This packaging keeps the compact structure and doesn't influence the intrinsic characteristic of fiber gratings. In addition, its temperature coefficient is reduced to 0.0005nm/°C, and this result reaches applicable request. The more important is this packaging can keep good long-term stability. After half a year, the characteristic, reflecting wavelength and temperature coefficient of the packaged fiber gratings have little changed, and this result realizes the high stability packaging for fiber gratings.
Multi-stage discrete Raman amplifiers with midway isolators to suppress double Rayleigh backscattering (DRB) are fully investigated at constant nonlinearity. The results show that placing Raman pumps at the last stage only is sufficient. For most conditions, two isolators can achieve adequate performance improvement, while more isolators only lead to slightly OSNR increase. The optimum positions of the isolators are insensitive to varied Raman gains, nonlinear phase shifts and Rayleigh coefficients, but sensitive to different fiber lengths as well as Raman pumping schemes. Moreover, backward pumping scheme can derive better noise performance than bi-directional pumping when using midway isolators.
A theoretical investigation of bidirectionally dual-order pumped distributed Raman amplifiers is presented in detail, and comparisons with other Raman amplification schemes, i.e., bidirectional first-order pumping and Raman-plus-erbium-doped fiber hybrid amplification, are carried out at identical nonlinear phase shifts. The results show that symmetric bidirectional dual-order pumping can achieve the best optical signal-to-noise ratio performance by appropriate choice of the second-order pump wavelength and second-to-first-order pump power ratio for both short- and long-span conditions.
We investigated the issue of dynamic gain control for multi-wavelength pumped broadband distributed Raman
amplifiers. For the first time, we proposed that using a pair of fiber gratings in a section of the transmission fiber, a gain
clamped broadband distributed fiber Raman amplifiers can easily be made through all optical method. The method is
based on the utilization of the pumps’ interactions and uneven gain property along the fiber in the amplifier.
In this paper we investigate both noise and transmission performance of bi-directionally pumped Raman amplifiers (RAs) in longhaul WDM systems detailedly. Compared with backward pumping or Raman+EDFA
hybrid amplification, bi-directionally pumping can provide flatter OSNR spectra in wideband WDM applications, as well as better noise performance at identical nonlinear phase shift due to its uniform power distribution. Moreover, transmission impacts induced by SPM and XPM are also analyzed, which indicates that Raman amplified systems are more sensitive to dispersion maps than discrete amplification.
In this paper we propose a novel structure to enhance pump conversion efficiency and noise characteristics of L-band EDFAs. By adding only a input-reflect fiber Bragg grating and reflecting fractional backward ASE power as a secondary forward pump to further amplify the signal light, larger than 20dB small signal gain improvement and 1dB NF decrease can be achieved. We also investigate the influences of different wavelength FBGs. Experimental results agree well with numerical simulations.
The cylindrical waveguide (optical fiber ) with a metal outer clad were analysed. The propagation constant of core mode and clad mode were derived from vector method and then solved by numerical method. And some characteristics of the mode in metal clad fiber were studied. We also analysied the effect of metal clad to the long-period fiber grating.
32 chirped FBGs (fiber Bragg gratings)-based dispersion compensators and EDFA (Er-Doped Fiber Amplifier) gain-equalizators is demonstrated. Dispersion compensation of 600km G652 fiber and limiting amplification of 16 wavelength signals with low power penalty of<2dB can be obtained at a 10GHz/s optical communication system.
In this paper we introduce the characteristic of the long period grating and methods to fabricate LPGs which are used as gain equalization filter to get broadband amplifiers. Long period fiber gratings used to flatten the gain spectrum of erbium-doped fiber amplifiers (EDFA) were fabricated in experiment. The bandwidth of the EDFA is 35 nm with the gain variation no more than +/- 0.5dB.
This paper demonstrates a novel dual-period fiber grating sensor which can measure strain and temperature simultaneously. The dual-period fiber grating consists of a long-period fiber grating (LPG) and a fiber Bragg grating (FBG) which are written in the same section of an uncovered hydrogen-loaded fiber orderly. As is known, the Bragg wavelength of LPG and that of FBG have the different sensitivity of strain and temperature, then strain and temperature can be determined simultaneously by measuring the two transmitted Bragg wavelengths of the dual-period fiber grating. The accuracy of the sensor in measuring strain and temperature is estimated to be +/- 16 (mu) (epsilon) in a range from 0 to 1700 (mu) (epsilon) and +/- 0.8 degree(s)C from 20 to 120 degree(s)C, respectively.
In this article, we used weakly guiding scalar approximation and coupled-mode theory to model long-period fiber gratings precisely. We also analyzed some phenomena about the growth and annealing of the LPG in H2-loaded fiber using molecular diffusion theory. At last, we developed a novel method to fabricate long-period fiber gratings with demanded transmission spectra and achieved a gain-flattened EDFA with a gain variation of +/- 0.5 nm in 35-nm bandwidth.
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