An edge filter is a potential technology in the fiber Bragg grating interrogation that has the advantages of fast response speed and suitability for dynamic measurement. To build a low loss, wideband jammed-array wideband sawtooth (JAWS) filter, a finite reflection virtually imaged array (FRVIA) is proposed and demonstrated. FRVIA is different from the virtually imaged phased array in that it has a low reflective front end. This change will lead to many differences in the device’s performance in output optical intensity distribution, spectral resolution, output aperture, and tolerance of the manufacture errors. A low loss, wideband JAWS filter based on an FRVIA can provide an edge filter for each channel, respectively.
We propose and demonstrate an all‐optical correlator based on modal dispersion in a multimode fiber. Many of the modes can be excited in a large core high numerical aperture step‐index multimode fiber under overfilled launching. The incident optical signal is copied into different modes and a time delay is introduced by the modal dispersion. We use a mask with slits as a space filter to select the modes needed. A correlator of the mask and input signal is achieved at the output end. Thanks to the use of modal dispersion, the correlator is nearly independent of the wavelength and bandwidth of the input signal. By adjusting the slits on the mask, the target patterns of the correlator can be changed easily. A radio frequency signal detection is also experimentally demonstrated with this construction.
Signal processing is studied for Sagnac fiber distributed sensors. Wavelet de-noising and wavelet decomposition
are comparatively used to analyze signals in frequency domain to give smoothed frequency spectra, based on which null
frequencies of the spectra are found more accurately. The analysis is helpful to more accurately locate the disturbance.
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.
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.
Temporal-Spectral Imaging of optical pulses constitutes a technique for the measurement of
fast optical spectral. The experiment to perform real-time spectral analysis of optical pulses in fibre by
time lens is demonstrated in this article. The use of time lens in the demodulation of the grating
wavelengths is discussed in this article.
Using broadband dispersion compensation CFBGs, over 500km-40Gbps NRZ transmission
system on G.652 fiber will be demonstrated without electric regenerator, FEC and Raman amplifier.
The power penalty is about 2dB @ BER =10-10.The CFBGs have better performance: 3dB band is
about 1.2nm, group delay ripple is less than 25ps near center wavelength, power ripple is less than 2dB,
and DGD is less than 1ps. In order to stabilize the DC bias of the LiNbO3 MZ modulator, a
semiconductor cooler is applied to control the temperature. The effect is perfect.
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.
The impact of cascaded CFBGs delay ripple for dispersion compensation has been analyzed. The experimental results show that the overall penalty was proportional either to the number or to the square root of the number of CFBGs employed along the link. The delay ripple of the overall CFBGs fluctuates, and the overall CFBGs reflectivity was not simply additive but was related to the placement of the CFBG and line amplifier gain. For the first time, the experimental results of dispersion compensation for a 2-×10-Gb/s, 1000-km WDM system using self-made CFBGs with less than 1-dB power penalty for each channel have been achieved.
We fabricated linearly chirped fiber gratings by using uniform phase mask instead of chirped mask. The chirp of the grating is realized by precisely setting the distance between the fiber and the phase mask at every point of the fiber. In experiments we derived linearly chirped fiber grating which has dispersion -1102ps/nm, time delay ripple is 17ps. And also the asymmetry high order apodization method is used successfully to reduce the time delay ripple. The experiment results consistent with the simulation results. We can fabricate gratings with different chirp extent use one uniform phase mask conveniently by only changing the curve function of the fiber.
System performance degradation caused by group delay ripples of chirped fiber Bragg grating dispersion compensators is analyzed in detail with considerations for the ripple period, amplitude and phase offset. And the induced different kinds of signal distortions are also shown and explained.
The dispersion of 8×10Gb/s wavelength division multiplex (WDM) system has been compensated by the cascaded chirped fiber Bragg gratings(CFBGs), with ITU-T standard wavelengths and wavelength grid. The ASE of the EDFA could be reduced, the OSNR of the transmitted signal could be increased and the fluctuation of the EDFA gain could be controlled in the certain scope by the dispersion compensated CFBGs' WDM system. Impact of cascaded CFBGs' delay ripple on dispersion compensation has been analyzed. Experiment of error-free 8×10Gb/s 2015km transmission without forward error correction (FEC) and electronic repeaters were demonstrated. In the transmission, simplex CFBGs compensators were used and no other form of dispersion compensators were adopted. The experiment result showed that the consistency of the dispersion compensating in each channel is perfect over 2015km optical fiber transmission. The experiment result does agree with the theoretic analysis.
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.
The random deviation of the periodicity of the gratings will affect the performance of the fiber gratings. The random errors would not accumulate when the gratings were cascaded. But we found a kind of fabricating system errors induced by the method for the side writing of fiber gratings, which would accumulate when cascaded. So laser with the less pulse energy should be used to write the gratings to developing the system's performance.
Based on the theory of Jones Matrix, a model for the analysis of non-PM fiber ring lasers polarization
characteristics was developed. The model was further tested by experiments. From the numerically and
experimentally analysis results, it was found that lasers composed by non-PM fiber can achieve stable output but
its polarization varied with external perturbation. If a polarizer was inserted into the laser cavity, though the
polarization state was more stable, the instability of output was even more serious. So special polarization control
must be performed to obtain single polarization laser output using non-PM fiber.
We have succeeded in transmitting the signal as long as 1400km with G.652 fiber using chirped fiber gratings. Asymmetrical apodization was adopted to reduce the grating’s GDR (group delay ripple). Power and dispersion management was adopted here to suppress the nonlinear effects.
Delay ripples of chirped fiber Bragg gratings (CFBGs), which a CFBG can compensate 200 km long optic fiber's dispersion, have been analyzed in detail. A numerical simulation of cascaded grating delay ripples has been done by Schroedinger equation and compared with experiment of 1,000 km transmission over G652 fiber by 5 groups of CFBGs dispersion compensation. The research shows that the system degradation depends on the delay ripple period, which is 0.01~0.1nm through a lot of experiments, and amplitude of delay ripple. We had experimentally studied fluctate of power penalty depend on ripple perod of CFBGs when source wavelength changed +/-20GHz around CFBGs center wavelength, the results of theory agree well with these of experiment.
For the first time, we study the transmission performance of 10Gbps PRBS data stream over ultra-high polarization mode dispersion (PMD) dispersion compensating fiber (DCF), which PMD coefficient is 237.95ps/km1/2. The simulation has been done by coupled nonlinear Schrodinger equations. Also transmitted experiment has been done by DCF with a PMD coefficient of 237.95ps/km1/2. The result of the simulation is consistent with that of the experiment.
Nonlinear chirped FBG(NLCFBG) is found to have the performance to compensate the dynamical nonlinear dispersion. In this paper, we investigate and compare, for the first time, the reflection spectrum and group delay of apodized nonlinear chirped fiber Bragg gratings which has raised much interest because of its reduced reflectivity
sidelobes in dynamical status. The dispersion characteristics of apodized, nonlinearly chirped fiber Bragg gratings and their potential as dispersion compensators have been studied systematically. It is shown that the super-Gaussian profile and Cones function result in an overall superior performance, as it provides highly quadratic group-delay characteristics in the dispersion-slope compensation.
In this paper, we focus on the improvement of accuracy of phase-shift methods to measure the fiber dispersion. By the analysis of experiment results and possible error sources, the more suitable measurement conditions are provided to decrease the measurement error to a great extent. Except keeping a constant temperature and isolating the device from mechanical vibrations when measurement is carried out, as large as 1nm measurement wavelength step and large wavelength span at several tens nm level are preferred to obtain more
accurate and repeatable measurement.
Dispersion-compensating chirped fiber gratings provide a compact low-loss means of compensating fiber dispersion.
They are potential candidates for per-channel tunable dispersion compensation devices [2]. Group delay ripple (GDR) is
the principle reason restraining the practical implementation of chirped fiber Bragg gratings and many papers indicate
how the GDR impairs the systems performance [1, 3, 4]. S.Jamal has indicated that the period of the group delay ripple
has much important influence on the systems performance [1]. But the ripple period of the chirped fiber grating was not
consistent along side the grating, and Michael Sumetsky has explained the cutoff phenomenon of the high frequency in
[2]. Because the period of the chirped fiber grating changed with the wavelength and the components of different
frequency overlapped with each other, the time-frequency analysis was needed to descript the time-frequency distribution
of the GDR of the grating. [5]
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.
It is first time to study on Gauss pulse transmission over ultra-high PMD fiber. Gauss pulse is broken into a series of deformed pulse when it transmits over ultra-high PMD fiber. He has explained that the walk-off deformed pulses cause by ultra-high PMD. Transmitted experiment has been done using fiber with PMD coefficient 237.95ps/km1/2. The simulated result is consistent with experiment.
With a new apodisation method and special package material, we have made high-quality chirped fiber Bragg gratings (CFBGs) with the fluctuating error of reflectivity less than 1dB, the delay ripple less than +/-15ps and the temperature coefficient being as low as 0.5‰onm/°C. Using such self-made high-quality CFBGs, we present, for the first time, the experiment results of dispersion compensation of 2x10Gb/s 1000km WDM system with less than 1 dB power penalty for each channel.
We used UV laser to write Bragg gratings on the polarization maintaining fiber (PMF). Because of the high-birefringence of the fiber, the Bragg wavelength of the grating on the two polarization axes was different. So that it could introduce great polarization mode dispersion (PMD). When the input was adapted to the axis of the grating, it can serve as the polarization compensation. We measured the polarization of the grating at the end of the article.
We have shown the polarization mode dispersion (PMID) of chirped fiber Bragg gratings (FBG) written on different photosensitive optical fibers. PMD of FBGs on special photosensitive fibers and hydrogenated single mode fiber (SMF) was studied and compared. Experiment results showed that the chirped FBG written on hydrogenated SMF has very low differential group delay (DGD), and it adapt in long-haul optically amplified lightwave systems. The PMD of chirped FBG is determined by the birefringence of the fiber and the dispersion of the chirped FBGs. The birefringence of FBG involved intrinsic and extrinsic or photo-induced birefringence. At the end of this paper, we presented the PMID of the dispersion compensation system using CFBG as dispersion compensator.
Eight-wavelength Er-doped fiber lasers with lasing wavelength separations approximately 1.6 nm and approximately 0.8 nm, respectively, have been achieved by using a Cascaded fiber Bragg grating (CFBG) in the fiber lasers and cooling the Er-doped fiber with liquid nitrogen. Our experiment shows that, utilizing the CFBG to select the lasing wavelengths, it is convenient to achieve fiber lasers with lasing wavelengths and lasing wavelength separations matching the ITU (International Telecommunication Union) channel allocation grid well.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.