共查询到20条相似文献,搜索用时 716 毫秒
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This paper studies the influence of random phase and amplitude fabrication errors on the performance of optical filters based on fiber Bragg gratings (FBG's). In particular, we analyze two effects of particular importance for optical communications: the excess crosstalk induced in apodized gratings commonly used in wavelength-division-multiplexing (WDM) systems, and the time-delay fluctuations that appear in chirped gratings employed to compensate the fiber dispersion. A statistical model is presented to explain these effects in terms of the coherence length of the grating fabrication procedure 相似文献
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Twyford E.J. Jokerst N.M. Kohl P.A. Tayag T.J. 《Photonics Technology Letters, IEEE》1995,7(7):766-768
We have demonstrated and evaluated a grating array outcoupler fabricated by photoelectrochemical (PEC) etching, a manufacturable and practical approach for fabrication of grating-based III-V semiconductor waveguide devices. An array of submicron period gratings was etched into photolithographically delineated areas in a single PEC step. The fabricated devices are: 10-μm wide rib waveguides with 0.35-μm first-order outcoupling gratings; and 10-μm wide rib waveguides with 10 μm×10 μm pixellated areas of gratings. Device characterization demonstrates the effectiveness of outcoupling grating fabrication using PEC and that the pixellated grating outcoupler is an effective and simple means of generating an optical beam array 相似文献
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Min-su Kim Jung Jin Ju Seung Koo Park Jae Yeob Shim Myung-Hyun Lee 《Lightwave Technology, Journal of》2009,27(21):4809-4813
Chirped gratings can be readily implemented in uniform-period waveguide Bragg gratings (WBGs) by adopting a tapered profile in the core patterning process. Based on our analysis, we have demonstrated that controlled linear chirps can be generated in WBGs with specifically designed core-taper profiles. By virtue of our established design and fabrication techniques, the measured center wavelengths, bandwidths, and dispersion coefficients of our fabricated straight and tapered polymeric WBGs agree very well with the designed values. We also obtained fairly low polarization-dependent wavelength shifts from the straight WBGs owing to the adopted low-birefringence polymeric materials. 相似文献
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In this paper, a dynamic optical arbitrary waveform generator (OAWG) based on cross phase modulation (XPM) is proposed. According to the characteristics of XPM, the nonlinear phase shift of signal can be changed along with the pump power. The amplitude of signal can be changed by controlling the phase shift at one arm of a Mach-Zehnder interferometer (MZI) using XPM effect between signal and pump. Therefore, the phase and amplitude of the optical frequency comb (OFC) can be controlled by two pump arrays. As a result, different kinds of waveforms can be synthesized. Due to the ultrafast response of XPM, the generated waveform could be dynamically updated with an ultrafast frequency. The waveform fidelity is affected by the updating frequency. 相似文献
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We report on the first dispersion study performed on planar Bragg gratings for WDM systems. The gratings are produced in low-loss single-mode polymeric waveguides and have a remarkable amplitude response (reflectivity >99.99%, suppressed out-of-band features). The phase response study shows that the dispersion that they introduce in a system (<100 ps/nm) is lower than that typical of fiber Bragg gratings 相似文献
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The chirp and optical extinction ratio of a multiple quantum-well (MQW) Mach-Zehnder modulator depend on the device design and on the voltage waveforms applied to the arm electrodes. For 10 Gb/s transmission over nondispersion shifted fiber, joint optimization of the bias and modulation voltages is considered for a conventional modulator and a π-phase-shift modulator. Measured attenuation and phase constants for an optical signal propagating in the modulator waveguide are used to accurately model the Mach-Zehnder modulators. The influence of asymmetric Y-branch waveguides in the modulators is examined taking into consideration group velocity dispersion and self-phase modulation arising from the Kerr nonlinearity. When the modulators are operated with maximum optical extinction ratio, the dispersion limited transmission distance depends on the device design (phase-shift and Y-branch splitting ratio) and modulation format (dual drive or single drive). Optimization of the bias and modulation voltages reduces this dependence significantly, while also increasing the dispersion limited transmission distance 相似文献
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Wavelength-interleaved OADMs incorporating optimized multiple phase-shifted FBGs for fiber-radio systems 总被引:2,自引:0,他引:2
Marra C. Nirmalathas A. Novak D. Lim C. Reekie L. Besley J.A. Weeks C. Baker N. 《Lightwave Technology, Journal of》2003,21(1):32-39
We demonstrate that a single fiber Bragg grating (FBG)-based optical add-drop multiplexer can be used to improve the optical spectral efficiency in a mm-wave WDM-fiber wireless network. The technique employs wavelength interleaving in conjunction with optical single-sideband modulation, together with a single multiphase-shifted fiber Bragg grating. Wavelength optical add-drop features are also demonstrated using the grating, and our results show the performance of the novel grating in terms of channel isolation and add-drop functionality. We perform simulations to optimize placement of the phase shifts when an apodization profile is applied to the grating, in an attempt to minimize in-band and out-of-band transmission-amplitude ripples. Experiments are performed using cascade configurations both with the apodized gratings with optimal phase-shift positions and with the original unoptimized gratings. The experimental results demonstrate how these novel gratings can be used in fiber-radio networks incorporating multiple optical add-drop multiplexers. 相似文献
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A directional coupling mechanism between different waveguides in a periodic array of waveguides is suggested. The optical power transfer between two different waveguides is mediated by the coupling between zero-order modes of two of the waveguides and the second band of the periodic structure. Analytical solutions for the no-detuning (narrow band) and far-from-resonance cases are presented. The far-from-resonance case is shown to resemble a simple two-mode system with complete optical power transfer between the two waveguides, coupled by localized gratings. The transfer is mediated by the second band of the periodic structure. The transition length depends strongly on the shape of the perturbation, and depends exponentially on the distance between the waveguides, yet it allows us to transfer power from one waveguide to another at such distances, for which the transition via conventional directional tunneling mechanism is impossible. Our analytical results are supported by numerical calculations carried out for a model problem with realistic parameters. 相似文献
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Akiyama S. Itoh H. Sekiguchi S. Hirose S. Takeuchi T. Kuramata A. Yamamoto T. 《Lightwave Technology, Journal of》2008,26(5):608-615
InP-based Mach-Zehnder modulators with capacitively loaded traveling-wave electrodes (CL-TWEs), which have segmented structures along the optical waveguides, are presented. Devices with various structural parameters for gap length (the length between adjacent segmented phase modulators) and total active length were fabricated and investigated both optically and electrically. Excellent characteristics such as characteristic impedance matching to 50 Omega and low electrical propagation losses were obtained. Using the optimum structures, 40- and 10-Gb/s large signal operations were successfully performed with peak-to-peak driving voltages of 3.0 and 1.2 V, respectively. The effects of structural parameters, such as gap length and total active length on electrical and optical modulation properties, are discussed. 相似文献
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Fiber grating spectra 总被引:65,自引:0,他引:65
In this paper, we describe the spectral characteristics that can be achieved in fiber reflection (Bragg) and transmission gratings. Both principles for understanding and tools for designing fiber gratings are emphasized. Examples are given to illustrate the wide variety of optical properties that are possible in fiber gratings. The types of gratings considered include uniform, apodized, chirped, discrete phase-shifted, and superstructure gratings; short-period and long-period gratings; symmetric and tilted gratings; and cladding-mode and radiation-mode coupling gratings 相似文献
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M.G. Thompson D. Brady S.W. Roberts 《Photonics Technology Letters, IEEE》2003,15(7):924-926
By measuring the phase and amplitude distribution of the optical paths in a flatband arrayed waveguide grating, the array mask was redesigned to correct for the slow varying phase errors within the array waveguides, leading to a reduction in both the chromatic dispersion across the passband of the device and in the transmission band tilt. 相似文献
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Volume current method for analysis of tilted fiber gratings 总被引:4,自引:0,他引:4
An analytic approach to calculate the radiation pattern (including the wavelength dependence, azimuthal distribution, and polarization dependence) of tilted fiber phase gratings using the volume current method (VCM) is introduced in this paper. Results for both uniform and apodized fiber gratings are derived and discussed, and a brief comparison to experimental measurements from practical devices is also made 相似文献
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Optical phased array technology 总被引:16,自引:0,他引:16
McManamon P.F. Dorschner T.A. Corkum D.L. Friedman L.J. Hobbs D.S. Holz M. Liberman S. Nguyen H.Q. Resler D.P. Sharp R.C. Watson E.A. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1996,84(2):268-298
Optical phased arrays represent an enabling new technology that makes possible simple affordable, lightweight, optical sensors offering very precise stabilization, random-access pointing programmable multiple simultaneous beams, a dynamic focus/defocus capability, and moderate to excellent optical power handling capability. These new arrays steer or otherwise operate on an already formed beam. A phase profile is imposed on an optical beam as it is either transmitted through or reflected from the phase shifter array. The imposed phase profile steers, focuses, fans out, or corrects phase aberrations on the beam. The array of optical phase shifters is realized through lithographic patterning of an electrical addressing network on the superstrate of a liquid crystal waveplate. Refractive index changes sufficiently large to realize full-wave differential phase shifts can be effected using low (<10 V) voltages applied to the liquid crystal phase plate electrodes. High efficiency large-angle steering with phased arrays requires phase shifter spacing on the order of a wavelength or less; consequently addressing issues make 1-D optical arrays much more practical than 2-D arrays. Orthogonal oriented 1-D phased arrays are used to deflect a beam in both dimensions. Optical phased arrays with apertures on the order of 4 cm by 4 cm have been fabricated for steering green, red, 1.06 μm, and 10.6 μm radiation. System concepts that include a passive acquisition sensor as well as a laser radar are presented 相似文献
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The unapodized and apodized step-chirped gratings (SCGs) for broadband frequency converters based on quasi-phase-matched second-harmonic generation with pump depletion in lithium niobate waveguides have been theoretically modeled and simulated as a function of the number of sections, and compared with the linearly chirped gratings (LCGs) for the first time to our knowledge. It is shown that for the same length, using fewer sections with more segments and larger amounts of chirp, the efficiency and bandwidth of an SCG approach over that of an LCG and can be extensively improved with apodization. Moreover, the increasing chirp period and duty cycle for the SCG structure may provide a more convenient method for fabrication and poling. In addition, we present useful relations for the band-widths that help to find the appropriate number of segments in the proposed SCGs of a given length. 相似文献