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1.
The analysis of the group delay ripple (GDR) generated by chirped fiber gratings is developed based on the Fabry-Perot (F-P) resonator. It shows clearly how the GDR is generated and why the periods of GDR varies along the chirped fiber gratings. It could also explain why apodization could suppress the GDR and how apodization affects the chirp of the grating. The theory could be used to devise the apodization of fiber gratings. 相似文献
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Sumetsky M Reyes PI Westbrook PS Litchinitser NM Eggleton BJ Li Y Deshmukh R Soccolich C 《Optics letters》2003,28(10):777-779
Group-delay ripple (GDR) introduced by systematic and random errors in chirped fiber Bragg grating fabrication is the most significant impediment to application of these devices in optical communication systems. We suggest and demonstrate a novel iterative procedure for GDR correction by subsequent UV exposure by use of a simple solution of the inverse problem for the coupled-wave equation. Our method is partly based but does not fully rely on the accuracy of this solution. In the experiment we achieved substantial reduction of the low-frequency group-delay ripple, from +/- 15 to +/- 2 ps, which resulted in dramatic improvement of the optical signal-to-noise-ratio system penalty, from 7 to less than 1 dB, for a chirped fiber Bragg grating used as a dispersion compensator in a 40-Gbit/s carrier-suppressed return-to-zero system. 相似文献
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We propose a new multiplexing technique using amplitude-modulated chirped fiber Bragg gratings that have an identical center Bragg wavelength. Each grating is inscribed with a unique amplitude modulation that allows them to be multiplexed with complete overlapping within a certain bandwidth. To demodulate the multiplexed signal, the discrete wavelet transform is employed. Concurrently, a wavelet denoising technique is used to reduce the noise. This proposed multiplexing technique has been verified through strain measurements. Experimental results showed that for strains applied up to 1250 microepsilon the absolute error and cross-talk are within +/-20 microepsilon and 16 microepsilon, respectively. A strain resolution of 4 microepsilon is obtained. 相似文献
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We describe the use of a matched linearly chirped fiber Bragg grating (FBG) pair as a key element in an adjustable optical delay line. This delay line has the unique property that the achievable optical group delay is orders of magnitude greater (factor of 10(2) in our experiment) than the actual physical displacement. We demonstrate operation of such an optical delay line over a delay range of 3.5 mm using a pair of matched 1300-nm chirped FBGs with a bandwidth of 20 nm each. 相似文献
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R.T. Zheng N.Q. Ngo L.N. Binh S.C. Tjin J.L. Yang 《Applied physics. B, Lasers and optics》2006,82(1):59-63
We present the design and development of piece-wise stepped-chirp fiber Bragg gratings (FBGs) with arbitrary group delay responses
using a uniform phase mask in a pre-stretched fiber. The method involves writing a series of sub-gratings on a pre-stretched
fiber whose length is varied during the UV exposure process. Two motorized stages are employed to control the length of the
pre-stretched fiber in order to adjust the grating pitch at each writing step to achieve piece-wise stepped chirping of the
FBG. To demonstrate the effectiveness of the method to produce chirped FBGs with arbitrary group delay responses, a linear-chirp
FBG and a quadratic-chirp FBG were fabricated, and their measured performances agree well with analytical predictions.
PACS 42.81.-i; 42.79.Dj; 42.79.Ci 相似文献
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This paper presents an analysis of how to obtain narrow transmission band in the centre of the spectrum of the arbitrary chirped fiber Bragg grating (ACFBG). Grating chirp coefficient and refractive index profile are the critical parameters in contributing to performance of fiber Bragg grating. The reflection spectra and transmission band were analyzed with different refractive index profile. Apodization techniques are used to get optimized reflection spectra. The simulations are based on solving coupled mode equations by transfer matrix method that describes the interaction of guided modes. 相似文献
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Apodization is a crucial technology for improving the dispersion performance of fiber Bragg gratings (FBGs). In this paper, we focus on how to select an optimal apodization for chirped fiber Bragg gratings and demonstrate a novel apodization selection method capable of choosing the optimal apodization based on the relationship between the bandwidth change and variation in average group delay ripple (GDR). Compared with current approaches, the novel method can select an optimal apodization profile and parameter for FBGs easily and accurately. Two numerical experiments are used to demonstrate the advantages of this method, one exhibits the different performances of five different apodization profiles, the other evaluates the influence of FBG parameters such as grating length, period, chirp, and index change on the apodization performance. 相似文献
11.
Skaar J 《Optics letters》1999,24(15):1020-1022
A new, simple method for characterization of fiber Bragg gratings is proposed. The group delay of the grating is obtained from measurement of the spectral reflectivity response of a grating that is interfering with a bare-fiber end reflection. 相似文献
12.
Viswanathan NK 《Optics letters》2004,29(21):2470-2472
The first, to my knowledge, experimental demonstration of photoerasure of UV-induced birefringence and polarization-mode dispersion (PMD) in chirped fiber Bragg gratings is presented here. The photoerasure process carried out by launching high-peak-power (approximately 0.6-kW) pulsed (10-Hz, 5-ns) circularly polarized laser light in the visible wavelength (532 nm) through the core of a fiber with the grating was found to reduce its PMD by more than 85% to 0.12 ps. Possible reasons for the photoerasure process, including photobleaching of UV-induced absorption and randomization of dipole orientation of UV-induced defects, are discussed. 相似文献
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A high channel-count comb filter based on multi-concatenated sampled chirped fiber Bragg gratings(MC-SCFBGs) is proposed and optimally designed by using several chirped gratings with different fundamental grating periods,instead of non-grating sections of SCFBGs.The numerical simulations of the reflection spectra show that the channel spacing and the channel bandwidth in MC-SCFBGs are smaller than those in multi-concatenated chirped fiber Bragg gratings(MC-CFBGs) and that the spectral bandwidth of MC-SCFBGs can be greatly broadened by increasing the cascade number of the grating sections in each sampling period. 相似文献
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《Comptes Rendus Physique》2016,17(9):1027-1037
When a fiber Bragg grating strain sensor is embedded inside a structure, the interaction of the sensor with the host material can lead to spurious results if the radial strain is neglected. In this article, we use numerical simulations to show that the axial and radial strains can be simultaneously measured with a single fiber in which a Bragg grating and a long-period grating are superimposed. Moreover, we present an optimal architecture of the sensor. 相似文献
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A novel tunable polarization mode dispersion compensator with strain chirped fiber Bragg gratings 总被引:1,自引:0,他引:1
A tunable polarization mode dispersion (PMD) compensator based on strain-ckirped fiber Bragg gratings (FBGs) is proposed. It natures in flexible designing, large tuning range, without using linear or nonlinear chirped phase mask, fast tuning response time, continuously adjustable, all-fiber based, compact, and cheap. 相似文献
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A tunable polarization mode dispersion (PMD) compensator based on strain-chirped fiber Bragg gratings (FBGs) is proposed. It natures in flexible designing, large tuning range, without using linear or nonlinear chirped phase mask, fast tuning response time, continuously adjustable, all-fiber based, compact, and cheap. 相似文献
18.
To model chirped fiber Bragg gratings (FBGs) for dispersion compensation in optical fibers a novel method of single expression (MSE) is used. The reformulation of Helmholtz's equation in the MSE to the full set of first-order differential equations leads to dealing with the electric field amplitude, its derivative, power flow density and phase distributions in any aperiodic media. The phase derivative obtained numerically permits to compute the dispersion slope in the time delay of investigated chirped gratings. Reflective and time delay spectra of linearly chirped gratings of different lengths and chirp coefficients are computed. A self-similarity law for the gratings of the same strength but different lengths and chirp coefficients is revealed. The apodization of gratings is applied to reduce sidelobes in gratings' reflection spectra and eliminate oscillations in the time delay characteristics. 相似文献
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Interferometric temperature-insensitive strain measurement with different-diameter fiber Bragg gratings 总被引:2,自引:0,他引:2
An interferometric strain-sensing system that combines an unbalanced Mach-Zehnder wavelength discriminator and spliced different-diameter fiber Bragg gratings is presented that has the capability to distinguish strain from temperature effects. Because the gratings are written in 135- and 165- microm -diameter fibers drawn from the same preform, when they are spliced they show similar temperature sensitivities but different responses to applied strain. Thus the relative Bragg wavelength difference of the two gratings is affected only by strain, and one can measure it accurately by monitoring the amplitude variation of the interference signal rather than the conventional phase variation. 相似文献