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1.
2.
Jin Xue Nanxi Li Kan Wu Jia Haur Wong Chunmei Ouyang Sheel Aditya Perry Ping Shum 《Optics Communications》2012,285(2):153-157
This paper investigates the effectiveness of phase noise suppression by incoherent addition in a passively mode-locked fiber laser. Incoherent addition is achieved by using an interferometer external to the mode-locked laser. Two different types of interferometers, Mach–Zehnder and ring, are investigated experimentally for different background phase noise levels. Measurements show that both types of interferometers can achieve good phase noise reduction for a background phase noise level above ? 130 dBc/Hz. Effects of dispersion management and pulse train intensity ratio in the interferometers are also discussed. Multi-stage cascaded interferometers are proposed for supermode noise suppression of harmonically actively mode-locked lasers. 相似文献
3.
In this Letter, we propose general optimization methods to design broadband high-efficiency grating couplers for planar waveguides. We attribute the coupling bandwidth to the mismatch of effective indices between the diffracted beam and the actual grating structure around the operation wavelength for fiber to waveguide excitation. The coupling bandwidth formula is deduced. A simple parameter-separate optimization procedure is proposed for general layered grating couplers for high coupling efficiency. Using our principle, we optimized a grating coupler for a horizontal slot waveguide operating at wavelength 1.55 μm for TM polarization. The grating coupler has 1 dB bandwidth of 60 nm and coupling efficiency of 65% with incident light from single-mode optical fiber (SMF) at 8°. 相似文献
4.
We propose a novel fiber Fabry-Perot interferometer (FPI) that incorporates a length of microfiber as its cavity and two fiber Bragg gratings (FBGs) as reflectors. The microfiber FPI is simply fabricated by flame-heated taper-drawing the central spot of an FBG into a section of microfiber. Ambient refractive index (RI) influences the effective index of microfiber, and thus the free spectrum range of the microfiber FPI, resulting in RI sensing. A dual-wavelength fiber laser based on the microfiber FPI is constructed, enabling radio frequency interrogation with high resolution. RI sensitivity of 911 MHz/RIU is experimentally demonstrated for microfiber FPI with equivalent diameter of 1.455 μm. Simulation results indicate that the sensitivity can be further enhanced by reducing the diameter of the microfiber. 相似文献
5.
We propose and demonstrate a novel and simple dual-parameter measurement scheme based on a cascaded optical fiber device of long-period grating (LPG) and photonic crystal fiber (PCF) modal interferometer. The temperature and refractive index (RI) can be measured simultaneously by monitoring the spectral characteristics of the device. The implemented sensor shows distinctive spectral sensitivities of -30.82 nm/RIU (refractive index unit) and 47.4 pm/°C by the LPG, and 171.96 nm/RIU and 10.4 pm/°C by the PCF modal interferometer. The simultaneous measurement of the temperature and external RI is experimentally demonstrated by the sensor. The temperature shift and RI shift calculated by the sensor matrix agree well with the actual temperature and RI change in the experiment. 相似文献
6.
We study a class of special strongly rpp semigroups, namely, the class of super rpp semigroups. These super rpp semigroups
are generalizations of both superabundant semigroups and Clifford semigroups within the class of rpp semigroups. In particular,
we prove that a super rpp semigroup is a semilattice of D
(l)-simple strongly rpp semigroups. Our result not only generalizes a well-known theorem of Clifford in the class of completely
regular semigroups but also strengthens some structure theorems obtained by Ren-Shum for superabundant semigroups which are
orthodox. Some special super rpp semigroups are considered and discussed. 相似文献
7.
采用半导体光放大器(SOA)中的瞬态交叉相位调制效应是实现高速全光信号处理的有效途径.利用SOA和带宽为0.4 nm的窄带滤波器同时实现了重复频率为10 GHz、脉冲宽度为10 ps的同相和反相全光波长转换.当滤波器的中心波长相对于探测光载波波长蓝移0.25 nm或者红移0.05 nm时,得到反相波长转换;当滤波器的中心波长相对于探测光波长蓝移0.29 nm或者红移0.25 nm时,得到同相的波长转换.同时用数值模拟了从同相到反相波长转换的极性演化过程,理论分析和实验结果基本相符.
关键词:
半导体光放大器
波长转换
瞬态交叉相位调制 相似文献
8.
Quasi-C-Ehresmann Semigroups and Their Subclasses 总被引:3,自引:0,他引:3
We introduce the concept of a quasi-C-Ehresmann semigroup. Some
special quasi-C-Ehresmann semigroups will be considered. We will
show that the quasi-C-Ehresmann semigroups are special
U-semiabundant semigroups and orthodox U-liberal semigroups,
which have been recently studied by several authors. Some
characterization theorems of this new class of semigroups are
obtained. Many results of quasi-C-semigroups in the literature
can be extended to quasi-C-Ehresmann Semigroups. 相似文献
9.
LetS be a semigroup andE the set of all idempotents inS. LetS-Act be the category of allS-acts. LetC be a full subcategory ofS-Act which containss
S and is closed under coproducts and summands. It is proved that, inC, anS-actP is projective and unitary if and only ifP≅ ∐
jϕ
I
Se
i
,e
i
ϕE. In particular,P is a projective, indecomposable and unitary object if and only ifP ≅Se for somee ∈E. These generalize some results obtained by Knauer and Talwar.
Research partially supported by a UGC (HK) (Grant No. 2160092). 相似文献
10.
We study finite groups whose maximal subgroups of Sylow subgroups are permutable with maximal subgroups.
__________
Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, No. 10, pp. 1299–1309, October, 2006. 相似文献