共查询到20条相似文献,搜索用时 31 毫秒
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讨论了介质薄膜滤波器的色散特点,并推导了单级全通滤波器的理论色散。比较理论色散曲线与实际测量色散曲线,两者吻合较好。但由于单级全通滤波器的色散带宽及斜率不能满足实际所需的色散补偿曲线,因此提出了多级全通滤波器,通过控制级连的单级全通滤波器的谐振波长及反射率,可以增大色散带宽,改善色散斜率,使之满足实用的要求。文中给出了四级全通滤波器的理论色散曲线。 相似文献
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Two-dimensionally periodic photonic crystal microcavity filters in a ridge waveguide format have been designed and fabricated. Transition mode-matching features were added to increase the optical throughput by more than a factor of two. An increase of Q-factor (more than 100%) was achieved by the addition of two further rows of photonic crystal holes to the microcavity filters. Attempts have also been made to tailor the filter response by applying design concepts used in other Bragg-grating optical filter technologies. 相似文献
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We show that high extinction ratio (>20 dB) modal interference in a two-mode dispersion compensating fiber can be utilized to build a compact, easy-to-fabricate tunable all-fiber optical comb filter. Wavelength tunability over the full free spectral range of the comb filter is demonstrated with an electrical power of 115mW using an on-fiber thin film micro-heater deposited directly on the fiber. In another configuration, the comb filter is used as a temperature sensor with dynamic range of >300 °C and sensitivity of <0.1 °C. The temperature sensor is capable of measuring a temperature as high as 500 °C. 相似文献
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薄膜截止滤光片的消偏振设计 总被引:3,自引:2,他引:1
薄膜截止滤光片在倾斜入射时不可避免地会产生s和p二个偏振分量的分离,因而在许多应用,特别是光通讯的应用中成为一个棘手的难题。提出了一种新的设计方法,对最常用的45°入射角,实现了长波通和短波通两种截止滤光片的完全消偏振, 在透射率为50%处,其偏振分离分别为0.3 nm和0.1 nm。基本的设计方法是采用宽带法布里珀罗薄膜干涉滤光片中心波长两侧的干涉带作为长波通或短波通截止滤光片的初始膜系,然后经过适当的优化以提高透射带的透射率。宽带干涉滤光片的间隔层常由半波长厚度的高、低折射率混合膜层组成,如2H2L2H或2L2H2L。由于这种设计的截止区和透射带带宽常嫌不足,故提出了展宽截止区和透射带的方法。对一个典型的短波通截止滤光片,在波长1550 nm,截止区和透射带宽均达到了200 nm。这种设计方法不仅简单、性能优良,而且膜厚控制容差较大,故易于制造。 相似文献
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A general method based on the predistortion technique is presented for determining the optimum coupling parameters of multiple-coupled microring filters in the presence of known uniform resonator loss. The technique involves predistorting the filter transfer function by shifting its poles and zeros to compensate for loss in the microring resonators due to material absorption, surface roughness scattering, coupling loss and bending loss. It is shown that by sacrificing some in-band insertion loss, both the amplitude and group delay responses of the filter can be recovered when loss is present. Application of the method to synthesizing lossy microring filters in both the digital z-domain and analog s-domain will be presented. The proposed technique is general in that it can be applied to both amplitude and phase filters constructed of coupled microresonators in the most general two-dimensional coupling topology. 相似文献
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Wei Jia Liyong Jiang Gaige Zheng Xiangyin Li Haipeng Li 《Optics & Laser Technology》2010,42(2):382-386
An application of the genetic algorithm in designing omnidirectional optical filters is reported in this paper. Concerning different periodic numbers and thickness ratios in the heterostructure, we gave some optimization examples and finally achieved a photonic heterostructure with very broad omnidirectional filter bandwidth as well as a very narrow transmission window. And it is found that when the normal incident beam is tilted at a negligibly small angle, the perfect transmittance peak will vanish. Hence, this heterostructure can be regarded as omnidirectional high-precision filters with potential application in optical filters, optical switches, and many other optical telecommunication areas. 相似文献
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A novel method for the measurement of chromatic dispersion of an optical fiber based on wavelength-to-time mapping using a femtosecond pulse laser (FSPL) and an optical comb filter is proposed and experimentally evaluated. In the proposed approach, the spectrum of an ultrashort optical pulse generated by an FSPL is sliced by an optical comb filter. The spectrum-sliced optical pulse is then coupled into the optical fiber under test. Thanks to the chromatic-dispersion-induced wavelength-to-time mapping in the optical fiber under test, a time-domain waveform similar to the sliced spectrum is generated at the output of the optical fiber, with different frequency components having different time delays. The time delay vs. frequency data are then recorded for the estimation of the chromatic dispersion by using least square fitting. Chromatic dispersions of two types of optical fibers with different lengths are tested. The measured dispersion values agree well with those measured by the conventional modulation phase shift (MPS) method. 相似文献
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High bit rates optical communication systems pose the challenge of their tolerance to linear and non-linear fiber impairments. Coherent optical receivers using digital signal processing techniques can mitigate the fiber impairments in the optical transmission system, including the chromatic dispersion equalization with digital filters. In this paper, an adaptive finite impulse response filter employing normalized least mean square algorithm is developed for compensating the chromatic dispersion in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying coherent communication system, which is established in the VPI simulation platform. The principle of the adaptive normalized least mean square algorithm for signal equalization is analyzed theoretically, and at the meanwhile, the taps number and the tap weights in the adaptive finite impulse response filter for compensating a certain fiber chromatic dispersion are also investigated by numerical simulation. The chromatic dispersion compensation performance of the adaptive filter is analyzed by evaluating the behavior of the bit-error-rate versus the optical signal-to-noise ratio, and the compensation results are also compared with other present digital filters. 相似文献
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This text deals with the study of the characteristics of GADC filters by taking into account the dispersion. After having defined the characteristics of the filter, the influence of separation between the guides and filter length on the characteristics of the filter are studied. It is shown that dispersion plays a very important role in the evaluation of spectral features of the filter and can not be neglected. 相似文献
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A novel wavelength-selective all-fiber filter using a single long-period fiber grating (LPG) interacting with a misaligned fusion splicing point has been demonstrated. The misaligned splicing point couples a part of the core mode power into the cladding modes, which is then recoupled into the core mode by the following LPG. As an optical path difference is introduced by the differential refractive index of the fiber, an in-fiber Mach-Zehnder interferometer is therefore formed, which may function as a cost-efficient WDM filter with good isolation and low insertion loss. 相似文献
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In this paper, a new method for designing three-zone optical pupil filter is presented. The phase-only optical pupil filter and the amplitude-only optical pupil filters were designed. The first kind of pupil for optical data storage can increase the transverse resolution. The second kind of pupil filter can increase the axial and transverse resolution at the same time, which is applicable in three-dimension imaging in confocal microscopy. 相似文献
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You Min Chang 《Optics Communications》2008,281(20):5146-5150
We experimentally demonstrate a single passband, photonic microwave bandpass filter scheme based on stimulated Brillouin scattering (SBS) in optical fiber. A single side band (SSB)-modulated probe and a single frequency, tunable pump beam that have been produced by the combination of conventional Mach-Zehnder modulators and fiber Bragg grating filters, are used for the generation of SBS phenomenon in a 1-km long highly nonlinear dispersion-shifted optical fiber. Using the proposed scheme a single microwave passband with a ∼26 MHz bandwidth is readily achieved over a radio frequency tuning range from 1.3 to 9.3 GHz. The maximum Q-factor is measured to be ∼360. 相似文献
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Anirudh Banerjee 《International Journal of Infrared and Millimeter Waves》2008,29(11):1070-1082
A theory to design narrow band optical filters by using a new photonic crystal structure is presented. This new photonic crystal
structure is composed of low index layers and high index layers arranged in mod. 4 up and down binary number sequence. The
new structure exhibits narrow transmission peaks in the forbidden frequency gap region with high optical transmission (greater
than 99.98%) at C.W.D.M. (Coarse Wavelength Division Multiplexing) center wavelengths. The proposed filters use only 8 layers.
These new binary number sequence photonic crystal narrowband optical filters are much smaller in size, lower in cost and easier
to fabricate as compared to narrowband photonic crystal optical filters based on defect Fractal Cantor multilayers, suggested
recently by a group of researchers. 相似文献
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Adrián J. Torregrosa 《Optics Communications》2010,283(7):1320-1325
We report a theoretical and experimental investigation on the structure and tuning capabilities of cascaded associations of microwave photonic filters composed of a single-source incoherent filter and a continuous-sample filter based on periodically-sliced broadband sources that undergo dispersion after being modulated. We derive the condition that guarantees both incoherent operation and cascading of the radio-frequency responses. This condition implies a lower bound for the ratio between resonance bandwidth (Δf) of the continuous-sample filter and the free spectral range (FSR) of the single-source filter, thus showing the possibility of cascading filters in two complementary regimes, Δf/FSR < 1 and >1. The tunability of the cascaded responses is also explored in a series of proof-of-concept experiments, where a static response of a single-tap, incoherent loop filter is reconfigured by use of a Solc filter. In particular, it is demonstrated a reconfigurable single and dual-bandpass cascaded response, which can be further modified by changes in dispersion, spectral period of the slicing filter, central wavelength or spectral width of the broadband source, and apodization of the resonance. The results are compared with the predictions of the Gaussian model for the degradation of resonances in continuous-sample filters due to second-order dispersion. 相似文献