Transmission characteristics of a single-mode fiber in the 1.3-µm wavelength region

Transmission characteristics of 1.3-μm-band single-mode optical fibers were studied experimentally and theoretically. OH-ion content dependence of optical loss in the 1.3-μm region was investigated on single-mode fibers fabricated by the VAD method. The optical loss was evaluated for OH-ion content by calculating correlation factors between the optical loss and 1.39-μm OH-peak absorption loss. It was clarified that the optical loss calculated by correlation factors agreed approximately with the loss given by Lorentzian absorption in case of 0.0253-μm absorption half width, Next, the relationship between chromatic dispersion and fiber parameters was studied for step-index single-mode fibers. It was found that the zero-dispersion wavelength and the incline at the wavelength was expressed as simple functions of effective cutoff wavelength and relative index difference. Experimentally obtained zero-dispersion wavelengths on single-mode fibers fabricated by the VAD method were found to be in excellent agreement with the calculated values.     

Optical multi/demultiplexers for single-mode fiber transmission

This paper describes two types of optical multi/demultiplexers using a single-mode fiber for a two-way transmission system. One type, the filter type, consists of four bandpass filters and a short wavelength pass filter or a long wavelength pass filter. The other, the filter-grating type, consists of two bandpass filters and a grating. The present multi/demultiplexers have four channels with 1.05, 1.15, 1.3, and 1.5 μm wavelengths. Total insertion losses are less than 2.3 and 3.2 dB for the filter type and the filter-grating type, respectively. Cross-talk between channels is less than -40 dB.     

Practical upper limits to cutoff wavelength for different single-mode fiber designs

A practical upper limit to cutoff wavelength in single-mode fiber is investigated. Based on the relationship between the attenuation of the LP11mode and the length dependence of cutoff wavelength, a formula is developed to predict this limit for four fiber designs commonly seen in commercially available fibers. It is found that, depending on fiber design, the upper limit of factory-measured fiber cutoff wavelength is anywhere from 20 to 60 nm above the system operating wavelength, even for a worst case "straight fiber" layout. Under actual field layout conditions, however, the limits converge to approximately 65 nm above the system wavelength for all four fiber designs. The practical upper limit predicted here is confirmed through an experimental evaluation of modal noise effects in a 1.2-Gbit/s single-mode fiber system.     

Ultrawide-band single-mode transmission performance in a low-loss photonic crystal fiber

We describe the ultrawide-band single-mode transmission performance of a photonic crystal fiber (PCF) in the 850 to 1550 nm wavelength range. We confirmed that the fabricated PCF achieves a single-mode operation over the 850 to 1550 nm wavelength range by measuring the mode-field diameter (MFD) and modal delay characteristics. The 10-Gb/s-based wavelength-division multiplexing (WDM) signals with a total capacity of 190 Gb/s were successfully transmitted over a 5.2-km low-loss PCF utilizing the 850, 1310, and 1550 nm regions simultaneously. Our experimental results show that an endlessly single-mode PCF provides an ultrawide-band of more than 160 THz for future optical communication systems.     

单模光纤中输出偏振态随波长变化关系的研究

偏振主态模型对偏振模色散给出了清楚而简单的描述 ,从此模型出发 ,利用邦加球推出了输出偏振态随波长变化的关系式 ,这对正确理解偏振主态模型的概念和机理及进行偏振模色散的进一步研究具有很重要的意义     

Optical componentry utilized in field trial of single-mode fiber long-haul transmission

Realization of large-capacity long-haul transmission systems is now quite promising due to rapid development in the field of optical fibers. This paper describes single-mode fiber optical components for use in the above-mentioned system. In particular, LD modules and optical connectors are most important for construction of a practical system. Thus, they are explained in detail along with their development procedures. Important field trial results of these components are also presented.     

用于高功率飞秒脉冲传输的空心单模Bragg光纤

针对超强能量密度的飞秒脉冲很难在传统光纤中传输的情况,设计了一款用于高功率飞秒脉冲传输的空心单模Bragg光纤。首先基于一维光子晶体的光子禁带特性选择了制作空心Bragg光纤的材料,接着利用光学软件FDTD Solutions分析了光纤各结构参数对光纤模式的影响,并对传输特性进行了分析。随后,通过在光纤包层中引入缺陷层的方法对其进行了进一步的优化,有效调控了该款光纤的色散曲线分布。经全带宽扫描可知,该款空心Bragg光纤单模传输的带宽达100 nm,完全满足了100 fs光脉冲的传输要求。     

Effective cutoff wavelength of the LP11mode in single-mode fiber cables

The effective cutoff wavelength of the LP11mode is investigated for nylon-coated step-index type single-mode fibers stranded in a cable. It is found from the pulse propagation experiments that the single-mode operation is effectively attained in the two-mode region up to theV-value of 3.0. It is numerically estimated that splice loss, bending loss, and absorption loss due to the OH-ion in cladding are reduced by choosing the operatingV-value as large as 3.0.     

Single-mode fiber design for long haul transmission

By using simple yet accurate approximations for the propagation characteristics of a single-mode optical fiber, we obtain a simple model for the total loss and chromatic dispersion of single-mode fiber transmission lines as a function of the operating conditions such as splice offset, microbending loss, bends, etc. This model is then applied to typical cases of terrestrial and submarine systems and we obtain single-mode fiber designs which are stable with respect to slight operating condition changes for both 1.3 and 1.55 μm wavelengths. It appears that the same fiber can be used at 1.3 μm for both terrestrial and submarine systems, and even for 1.55 μm terrestrial systems if monochromatic sources become available at this wavelength. A general comparison between the two wavelengths is carried out and shows under which conditions the 1.55 μm wavelength is of practical interest. It is emphasized that the availability of monochromatic sources at 1.55 μm would make a major breakthrough for the repeater spacing.     

单模光纤的PMD

讨论了单模光纤的偏振模色散PMD，包括PMD与单模光纤的几何尺寸及应力的非圆对称的关系模间耦合的影响。PMD具有瞬时统计特性以及采用Monte Carlo模拟软件对光缆产品的PMDQ进行估算。     

Characteristics of dispersion free single-mode fiber in the 1.5 µm wavelength region

Characteristics of dispersion free single-mode fibers in the wavelength regions 1.5 and 1.3 μm are compared experimentally and theoretically. We consider the influence of the refractive index profile on dispersion, the tolerance limits of structure parameters for minimum dispersion, attainable fiber bandwidth, and transmission loss including splicing and bending losses. For a fiber designed for minimum dispersion at 1.5 μm, the measured fiber loss was less than 1 dB/km and bandwidth was 250 GHz. km. nm. The achievable minimum loss estimation shows the advantage of dispersion free fibers at the 1.5 μm wavelength over dispersion free fibers at 1.3 μm.     

高功率激光单模光纤远距离传输实验研究

受激拉曼散射（SRS）效应是制约高功率激光单模光纤远距离传输应用的瓶颈因素。采用1550nm非偏振连续波单模光纤激光器作为光源, 通过实验研究了不同注入光功率条件下经过103km单模光纤传输所产生的受激拉曼散射现象,运用级联长周期光纤光栅带阻滤波器进行了受激拉曼散射抑制实验,并进行了相应的理论分析。提出了光纤受激拉曼散射抑制有效性判据,实验演示了受激拉曼散射现象,验证了级联长周期光纤光栅带阻滤波器对受激拉曼散射抑制的有效性。     

超高斯光脉冲在单模光纤中的传输特性

从光脉冲在光纤中传输演变所满足的基本方程出发,研究了超高斯光脉冲在普通单模光纤中的传输特性。数值模拟的结果表明,超高斯光脉冲入射后脉冲波形、瞬时啁啾以及峰值强度的演变规律与高斯脉冲入射时不同,脉冲波形不再总保持单峰结构,通常将经历一个从近平顶、多峰、最后到单峰的演变过程;从脉冲的前沿到后沿,瞬时啁啾也不再为线性,而是具有多个极值;峰值强度随传输距离的变化趋势也不再为单调递减,而是先增加后减小。这些变化规律还与入射超高斯脉冲的边沿陡峭程度和初始频率啁啾有关。     

An 800 Mbit/s optical transmission experiment using a single-mode fiber

It has been confirmed by a preliminary transmission experiment that a repeater spacing at 800 Mbits/s can be lengthened up to 7.3 km, by using a combination of a low-loss single-mode fiber and a well designed AlGaAs laser. The laser is modulated by a signal current superimposed on a dc bias current above the threshold. This modulation scheme avoids the spectrum broadening of the laser at the cost of extinction ratio degradation. A discrepancy of about 13 dB exists between the measured and the calculated error-rate performance curves. The major part of the discrepancy, 10 dB, is due to the extinction ratio degradation.     

Distributed single-mode fiber to single-mode planar waveguidecoupler

Light transfer between a curved single-mode fiber and a single-mode planar waveguide is investigated experimentally in dependence on the refractive index and thickness of the planar waveguide and for different polishing depths. Marcuse's model is applied to treat theoretically the coupler, leading to a very good agreement with the experimental results     

Design and performance of ultra-low-loss single-mode fiber cable in 1.5-µm wavelength region

The structural optimization of single-mode fiber for use in the 1.5-μm wavelength region is made with the aim of minimizing the total transmission-line loss over a repeater section. For example, the optimum ranges of the mode-field radius w0and effective cutoff wavelength λceare determined as 5.5 μmleq w_{0} leq 6.5 mum and 1.35μmleq lambda_{ce} leq 1.53 mum for high bit-rate transmission systems with a repeater spacing of 80 km. Based upon the design, ultra-low-loss single-mode fiber cables are fabricated. The average loss of 108 fibers in the cables is 0.19 dB/km at 1.55 μm. The total loss of a 216-km-long fiber link containing 107 splice points was 46.3 dB. Good loss stability at high temperatures as well as during the cable manufacturing processes, are achieved by the appropriate choices of coating materials and optimized fiber parameters.     

单模光纤拉伸器分布式双折射特性实验研究

在偏振敏感光纤系统中,光纤双折射是重要的参 量。基于压电陶瓷的单模光纤(single-mode fiber,SMF)拉伸器是光纤系统中引入应变、光程或 相位变化等常用的器件,而少有人关注过光纤拉伸器引入的双折射特性。本文提出基于分布 式偏振分析的SMF拉伸器双 折射特性表征方法,结合全穆勒矩阵分析和光频域反射仪技术,可以得到SMF拉伸器缠 绕光纤的分布式双折射特性。实 验得到:在光纤拉伸器使用过程中,光纤双折射随驱动电压增大而增加;当光纤拉伸器缠绕 光纤表面不平整时,可引入更高 的基底双折射,且在施加驱动电压时,基底双折射增加更加明显;设计合适的拉伸机构和光 纤缠绕方法,能有效地避免光纤拉 伸器使用过程中双折射的改变,但可能会引入较强的基底双折射。本文研究结果对于在偏振 敏感光纤系统中使用光纤拉伸器时系统性能的评估及优化具有指导意义。     

Mode coupling effects of the cutoff wavelength characteristics ofdispersion-shifted and dispersion-unshifted single-mode fibers

The authors present theoretical background and experimental results to clarify the nature of the hump in the cutoff region of different types of single-mode fibers and discuss its implications. A theoretical model in terms of the coupling between the whispering-gallery mode formed near the silica-cladding/primary-coating boundary and the first higher-order core mode is presented to explain the presence of the hump. An experimental verification of this theoretical model is presented for these fibers. In addition, the curvature sensitivity of the hump is studied for these three fiber types. The results of the study show that for both dispersion-shifted and matched-cladding, dispersion-unshifted fibers, the hump is curvature sensitive and occurs at intermediate (28 and 15 cm) bend diameters. At large (40 cm) and small (10 cm) bend diameters, the hump was not observed in the cutoff region of these two fiber types. However, in the case of the depressed-cladding fiber, the hump was found to be curvature insensitive and occurred at all bend diameters (40, 28, 15, and 10 cm) used in this study     

Investigation of polarization dispersion in long lengths of single-mode fiber using multilongitudinal mode lasers

We have used multilongitudinal mode lasers to investigate the polarization properties of long lengths of single-mode fiber cable. We find that the individual longitudinal modes are >99-percent polarized after propagation through 54.6 km of cabled fiber; however, the different longitudinal modes have different states of polarization at the output. This difference is caused by polarization dispersion, and we estimate a propagation delay difference for the two principal states of polarization to be 0.42 ps in the 54.6 km of cabled fiber.