The study of chromatic dispersion and chromatic dispersion slope of WI- and WII-type triple-clad single-mode fibers

In this paper, the chromatic dispersion and chromatic dispersion slope of two kinds of triple-clad single-mode fibers with a depressed index inner cladding named WI- and WII-type were examined. A feasible approach to calculate chromatic dispersion and higher-order dispersion was established successfully, and the influences made by the optical parameters and geometric parameters on the chromatic dispersion coefficient and its slope were analyzed in detail. The calculated results show that the optical parameter R₂, which symbolizes the third cladding effect, has a strong impact on the chromatic dispersion coefficient and the chromatic dispersion slope, and the degrees of such impact are closely related to the other parameters.     

Broadband dispersion compensation of conventional single mode fibers using microstructure optical fibers

This paper presents a microstructure optical fiber for dispersion compensation in a wide range of wavelengths. The finite-element method with perfectly matched absorbing layers boundary condition is used to investigate the guiding properties. The designed novel dispersion compensating fiber shows that it is possible to obtain a larger negative dispersion coefficient of about −130 to −360 ps/(nm km), better dispersion slope compensation, better compensation ratio, and lower confinement losses less than 10⁻² dB/km in the entire telecommunication (1400–1600 nm) band by using a modest number of design parameters and very simple cladding design.     

Simultaneous measurements of non-linear coefficient, zero-dispersion wavelength and chromatic dispersion in dispersion-shifted fibers by four-wave mixing

We report on a new simple technique for the simultaneous measurement of non-linear coefficient, zero-dispersion wavelength, and chromatic dispersion in dispersion-shifted fibers based on partially degenerated four-wave mixing. Both zero-dispersion wavelength and chromatic dispersion of the dispersion-shifted fibers can be measured with high accuracy. The experiment results of two dispersion-shifted fibers will be presented and the technique for obtaining accurate chromatic dispersion and zero-dispersion wavelength will also be discussed.     

Design and characterization of single mode circular photonic crystal fiber for broadband dispersion compensation

In this paper, we present a single mode circular photonic crystal fiber (C-PCF) for broadband dispersion compensation covering 1400 to 1610 nm wavelength band over the telecommunication windows. Investigations of guiding properties are carried out using finite element method (FEM) with circular perfectly matched layer boundary condition. Numerical study reveals that a negative dispersion coefficient of about −386.57 to −971.44 ps/(nm km) is possible to obtain over the wavelength ranging from 1400 to 1610 nm with a relative dispersion slope (RDS) of about 0.0036 nm⁻¹ at 1550 nm wavelength. In addition, the single mode behaviour of C-PCF is demonstrated by employing V parameter. According to simulation, it is found that the proposed C-PCF acts as a single mode fiber within 1340 to 1640 nm wavelength. Moreover, effective dispersion, relative dispersion slope, birefringence and confinement loss are also presented and discussed.     

Maintaining single polarization and dispersion compensation with modified rectangular microstructure optical fiber

In this paper, we propose and numerically demonstrate a highly birefringent microstructure optical fiber which shows negative dispersion coefficient of about −288 to −550 ps/(nm km) covering S to L wavelength bands and −425 ps/(nm km) at the excitation wavelength 1550 nm. This proposed design successfully compensate the dispersion covering S to L communication bands ranging from 1460 to 1625 nm along with relative dispersion slope (RDS) perfectly matched to that of single mode fiber of about 0.0036 nm⁻¹. Apart from dispersion compensation, the designed MOF offers high birefringence of 2.94 × 10⁻² at 1550 nm and better compensation ratio with design simplicity due to circular air-holes in the fiber cladding.     

Analysis of waveguide dispersion characteristics of WI- and WII-type triple-clad single-mode fibers

Waveguide dispersion characteristics of two kinds of triple-clad single-mode fibers named WI and WII were examined in this paper. In view of the impossibility to deduce the expression of waveguide dispersion directly due to the complexity of the characteristic equations, a feasible approach to calculate waveguide dispersion was established. The calculated results indicate that the adjustable range of the zero-dispersion point of the triple-clad WI- and WII-type single-mode fibers is obviously wider than that of the conventional doubly clad W-type single-mode fibers in the same conditions. The influences made by the geometric parameters and optical parameters on the waveguide dispersion and cutoff characteristics of low-order modes for WI- and WII-type fibers were analyzed. The method presented to calculate waveguide dispersion can be applied to multi-clad fibers.     

Design of single polarization single mode dispersion compensating photonic crystal fiber

In this paper, we present a photonic crystal fiber based on hexagonal structure for improved negative dispersion as well as high birefringence in the telecom wavelength bands. It is demonstrated that it is possible to obtain negative dispersion coefficient of −712 ps/(nm km) and relative dispersion slope (RDS) perfectly match to that of single mode fiber (SMF) of about 0.0036 nm⁻¹ at the operating wavelength 1550 nm. The proposed fiber exhibits high birefringence of the order 2.11 × 10⁻² with nonlinear coefficient about 57.57 W⁻¹ km⁻¹ at 1550 nm. Moreover, it is confirmed that the designed fiber successfully operates as a single mode in the entire band of interest.     

Design considerations of depressed clad W-shaped single mode dispersion compensating fibers

Dispersion compensating fibers (DCFs) are being widely used as dispersion compensation techniques because of its superior characteristics. This work reports the theoretical modelling of a single mode DCF having W-shaped shallow as well as deeply depressed clad profile. The DCFs have been designed and optimized by suitable adjusting different fiber parameters such as, central relative index difference (Δ⁺), inner core radius (a), depression depth parameter (ρ), normalized end position of the depressed clad (p), etc. at a given spot size . The figure of merit (FOM) characteristics including the bend loss as well as other losses associated with fiber manufacturing technique have been thoroughly investigated. Performances of these DCFs for recent wavelength division multiplexing (WDM) transmission system have also been discussed. By adjusting different fiber parameters, the effective core area (A_eff) of the above DCFs can be controlled to minimize the effect of non-linearities on them.     

Optical-frequency dependent modal birefringence and polarization mode dispersion of birefringent single-mode optical fibers over a broadband optical wavelength range

Optical-frequency dependent polarization mode dispersion as well as modal birefringence of three kinds of specially designed hollow-induced birefringent single-mode fiber are measured over an optical frequency range between 345 and 410 THz by optical frequency-domain interferometry.     

Polarization mode dispersion in single mode optical fibers due to core-ellipticity

The variation of polarization mode dispersion (PMD) with V-parameter in single mode optical fibers due to core-ellipticity is studied by performing numerical simulations taking into account both geometrical and thermal-stress-induced birefringences as well as the variation of fiber refractive indices with wavelength. Simple empirical relations are given for calculating the mean PMD for any value of core-ellipticity and V-parameter of a standard single mode fiber. It is observed that the mean PMD saturates for V ? 1.8 leading to very small second order PMD.     

Polarization mode dispersion and chromatic dispersion compensation by using a three-stage compensator

A three-stage compensator used for Polarization mode dispersion (PMD) and Chromatic dispersion (CD) compensation is proposed. The compensator is capable of compensating the two components of second-order PMD when no CD exists. Two operating points of compensating second-order PMD have been proposed. Two-stage and three-stage compensators are compared by the outage probability. When CD is introduced, the compensator should retain a quantity of second-order PMD to compensate CD. The outage probability when PMD and CD coexist has been calculated. The results show that a tradeoff must be made in order to compensate CD and PMD at the same time.     

偏振模色散模拟器的特性

通过对微分群时延差(DGD)统计特性和偏振模色散(PMD)矢量自相关函数的数值模拟，分析比较了目前常用的三种PMD模拟器的性能. 结果表明：在DGD分布方面，由DGD发生器构成的模拟器，一个DGD发生器就可与实际光纤PMD的统计特性相符合，而由保偏光纤和可旋转的连接器构成的模拟器则至少需要15段. 在自相关函数方面，基于保偏光纤的模拟器取决于各段光纤的延时量，而基于DGD发生器的模拟器在中心频带外的自相关值很平稳，可视为常数. 关键词： 光纤通信 偏振模色散 偏振模色散模拟器 自相关函数     

Microstructure holey fibers as wideband dispersion compensating media for high speed transmission system

This paper presents a dispersion compensating microstructure holey fiber for wideband transmission system. The finite element method with perfectly matched absorbing layers boundary condition is used to investigate the guiding properties. According to simulation, negative dispersion coefficient of −1455 ps/(nm km) and a relative dispersion slope (RDS) close to that of single mode fiber of about 0.0036 nm⁻¹ is obtained at 1.55 μm. The variation of structural parameters is also studied to evaluate the tolerance of the fabrication. The proposed module can be used in 40 Gb/s dense wavelength division multiplexing (DWDM) systems in optical fiber communication networks.     

能够补偿二阶偏振模色散的三阶段偏振模色散补偿器

简要分析了偏振相关色散对光通信系统性能的影响,提出了一种三阶段高阶偏振模色散补偿方案,从理论上分析了它同时补偿偏振相关色散和偏振主态旋转的可能性,并提出了其可能存在的两种工作方式.通过数值模拟与两阶段补偿方案进行了性能比较,其偏振模色散容限比两阶段补偿提高约17%个比特周期 关键词： 光通信 光偏振 光纤色散     

Broadband nearly-zero ultra-flattened dispersion single mode index guiding holey fiber

This paper proposes and demonstrates a novel type of silica index guiding holey fibers (IGHFs) that has two cladding layers at the defective innermost structures. The proposed IGHFs exhibit remarkable chromatic dispersion properties such as nearly-zero and flattened dispersion over a wide spectral range and single mode guidance along with very low confinement loss. The numerical results indicate that 5 air-hole rings of nearly zero ultra-flattened dispersion single mode IGHFs can be designed with desire flattened dispersion of over a 340 nm bandwidth including the entire band of interest with low confinement loss of less than 10⁻⁶ dB/m.     

Investigation of cladding and coating stripping methods for specialty optical fibers

Fiber optic sensing technology is used extensively in several engineering fields, including smart structures, health and usage monitoring, non-destructive testing, minimum invasive sensing, safety monitoring, and other advanced measurement fields. A general optical fiber consists of a core, cladding, and coating layers. Many sensing principles require that the cladding or coating layer should be removed or modified. In addition, since different sensing systems are needed for different types of optical fibers, it is very important to find and sort out the suitable cladding or coating removal method for a particular fiber. This study focuses on finding the cladding and coating stripping methods for four recent specialty optical fibers, namely: hard polymer-clad fiber, graded-index plastic optical fiber, copper/carbon-coated optical fiber, and aluminum-coated optical fiber. Several methods, including novel laser stripping and conventional chemical and mechanical stripping, were tried to determine the most suitable and efficient technique. Microscopic investigation of the fiber surfaces was used to visually evaluate the mechanical reliability. Optical time domain reflectometric signals of the successful removal cases were investigated to further examine the optical reliability. Based on our results, we describe and summarize the successful and unsuccessful methods.     

Chromatic dispersion behavior of Si-NC-Er doped optical fiber

The chromatic dispersion for conventional and Er-doped fibers using the refractive index approximation is examined. A first, analytical method for investigation of dispersion in step index triple clad optical fiber is used. To design of zero-dispersion shifted fiber for optical communication purpose manipulation of the refractive index and radius of the core are considered. We show that in presence of the Si-NC-Er ions, zero-dispersion wavelength is displaced and the dispersion quantity is increased. In this work, we try to optimize system parameters to obtain minimum dispersion and dispersion shifted fiber with control of the doping levels of Er ions and Si-NC as well as doping profiles. For especial case, we assumed the Gaussian inhomogeneous core refractive index for zero-dispersion wavelength and dispersion managements.     

W型单模单偏振光纤基模截止的条件

给出了 W型单模单偏振光纤基模截止的必要条件。通过对基模截止波长的数值计算 ,分析了这个必要条件的充分性。结论是 :对于圆形内包层 W型光纤来说 ,这是必要的而又充分的条件 ;对于低椭圆度内包层 W型单模单偏振光纤来说 ,它可以在较高的精度上近似作为充分条件 ,而对于高椭圆度内包层 W型单模单偏振光纤来说 ,它仅仅只是必要条件而非充分条件     

Highly birefringent photonic crystal fibers with flattened dispersion and low effective mode area

A highly birefringent index-guiding photonic crystal fibers with flattened dispersion and low effective area is proposed by introducing elliptical air holes in the cladding and small holes both in the core area and in the cladding. With the plane wave expansion (PWE) method, the birefringent, dispersion and effective area of the fundamental modes in such photonic crystal fibers are analyzed in detail. The simulation result shows that high birefringence with a magnitude of the order of 10⁻³, flattened chromatic dispersion from 1100 nm to 1800 nm and low effective area (which mean high nonlinearity) are obtained. Furthermore, the influences on the birefringence and dispersion by geometrical parameters have also been discussed and a modest number of design parameters are given.