Technique for direct measurement of single-mode fiber chromatic dispersion

A technique for the direct measurement of single-mode fiber chromatic dispersion is presented. The technique uses wavelength modulation to provide a differential fiber chromatic delay signal from which chromatic dispersion is obtained directly. The system is described in detail and practical measurement results shown to illustrate the high accuracy of the technique and its versatility in use with all fiber types.     

Direct measurement of chromatic dispersion in single-mode fibres using streak camera

For the first time the dispersion characteristics in a single-mode fibre in the 1 ?m-wavelength region is directly measured using a streak camera with a synchroscan streak tube having an S-1 photocathode.     

Polarization dispersion measurement on twisted single-mode optical fibers

A new method for measuring polarization dispersion between two eigen polarization modes is presented. It utilizes the measured phase shift corresponding to birefringence difference between two adjacent wavelengths. This method makes it possible to measure small polarization dispersion by using a short test piece even when eigen polarization modes are elliptically polarized. A polarization dispersion of 0.4 ps/km in twisted single-mode fibers can be measured in an approximately 4-m-long fiber by using 1.152- and 1.161-μm lines in a He-Ne laser. Experimental data that polarization dispersion decreases with an increase in fiber twist ate in very close agreement with theoretical results.     

Phase-shift technique for the measurement of chromatic dispersion in single-mode optical fibres using LEDs

The phase-shift technique has been successfully extended to chromatic dispersion measurements in single-mode optical fibres. Using only two sinusoidally modulated LEDs operating at 1.33 and 1.47 ?m, accurate results have been achieved in the spectral region of interest, in good agreement with those obtained with the Nd-Yag laser and Raman fibre technique.     

Ultralow chromatic dispersion measurement of optical fibers with a tunable fiber laser

We describe a novel convenient technique to allow for the accurate measurement of the dispersion coefficients till fourth-order in the zero-dispersion wavelength region of single-mode optical fibers. The proposed method is based on a careful spectral analysis of modulation instability occurring in both normal and anomalous dispersion regime and the associated dispersive waves emitted by soliton fission. It simply requires a high-power tunable continuous-wave fiber laser and an optical spectrum analyzer and is able to retrieve both the sign and magnitude of dispersion coefficients with enhanced precision.     

Triple-clad single-mode fibers for dispersion shifting

A design procedure for triple-clad dispersion-shifted single-mode fibers is developed. Following this procedure, fibers are identified which have low dopant concentrations in the core compared to those of the previous dispersion-shifted fiber designs, a second-mode cutoff wavelength close to the operating wavelength, zero dispersion at 1550 nm, a small bending loss at 1550 nm (for a bend radius of 3.75 cm), and a spot size that is large enough not to compromise the splice loss. A significant advantage of these fibers is that low-dispersion is available over a wide wavelength band about the wavelength of zero dispersion     

New method for measuring the chromatic dispersion of installed single-mode fibers utilizing wavelength division multiplexing techniques

This paper describes a novel method designed to measure the chromatic dispersion of installed single-mode fiber cables. The systems developed utilize the modulation phase/multiple laser diode techniques; however, by the addition of wavelength division multiplexing, the reference laser and fiber was eliminated. Laboratory and field results for measured wavelength ranges of 1200-1330 and 1200-1550 nm are presented.     

Polarization mode dispersion measurement in elliptical core single-mode fibers by a spatial technique

Polarization mode dispersion in elliptical core single-mode fibers has been measured by a spatial technique based on a visibility maximum position measurement in an interferometer. Using the technique, wavelength dependence of the modal dispersion has been measured by varying optical source wavelength between 821 and 904 nm. As a result, contribution of geometrical and strain birefringences on the modal dispersion has been evaluated, and normalized frequency dependence of the modal dispersion has been clarified. Moreover, the dispersion compensation effect has been observed by interchanging the fast and slow modes of two fibers at a splice point. The experimental results reveal that the spatial technique is very useful for polarization mode dispersion measurement.     

A single-mode fiber with chromatic dispersion varying along thelength

A method for fabrication of a novel type of optical fiber with dispersion varying along the fiber length is described. The method takes into account the calculated dependence of fiber dispersion on fiber core diameter for the measured profile of the preform and the desirable dispersion dependence on the fiber length. The main optical parameters of the drawn fiber are theoretically studied and experimentally measured. The fibers are of great interest for nonlinear fiber optics. Such applications of the fibers, such as high-quality soliton pulse compression, soliton pulsewidth stabilization through compensation of losses, and generation of a high-repetition-rate train of practically uninteracting solitons, are considered     

Interferometric determination of dispersion variations in single-mode fibers

Interferometry is used to study the variation of the zero dispersion wavelength (λ0) and the absolute group index (Ng) along the lengths of depressed cladding single-mode fibers. All of the results are for 34-cm samples of AT&T fibers drawn on production facilities. For two 7.5-km fibers sampled approximately every 1 km,bar{lambda_{0}} = 1299.6 pm 2.7and 1300.5 ± 2.9 nm. For five additional 0.8-km fibers, the average of the end-to-end differences of λ0is 2.0 nm. These results indicate the feasibility of inferring λ0for long lengths of these fibers from measurements made on a 34-cm length. At 1.30 μm,bar{N_{g}}and σ are 1.4659 and 0.0003, respectively (60 fibers from 28 preforms). The corresponding values at 1.55 μm are 1.4666 and 0.0003 (46 fibers from 19 preforms). These results place a lower limit of 0.02 percent on the accuracy of pulse delay measurements of unstressed lengths of AT&T production fibers.     

Polarization dispersion measurement in long single-mode fibers with zero dispersion wavelength at 1.5 µm

Polarization dispersion in 1 km long single-mode fibers is measured by observing the wavelength dependence of fiber birefringence. A typical measured value is 0.24 ps/km at the 1.2 μm wavelength. The measured wavelength dependence of polarization dispersion is explained well by a theory taking into account elliptical core deformation. Fitted core ellipticity values for the two test fibers are 0.012 and 0.003.     

基于相位-强度调制转换的光纤色散精确测量方法

在分析光纤色散导致的相位-强度调制转换的基础上,提出了一种利用电光相位调制的光纤色散扫频测量方法。方法的原理为光纤色散使相位调制信号获得附加相移并产生周期性衰落,从衰落曲线的特征性凹陷频率确定出光纤色散。实际运用中,由于凹陷频率附近的信号弱,因此噪声大且不稳定。为了解决这一问题,通过衰落曲线的多项式拟合,进一步提高凹陷频率和光纤色散的测量精度。实验中,对长光纤或者短光纤分别测试以验证本文方法对于不同色散的适应性。实验结果表明,本文方法的相对误差小于0.22%。使用矢量网络分析仪(VNA)和相位调制器进行测试,可工作于不同光波长,适用于测量不同种类的光纤的色散;并且可以利用简单的实验系统,实现光纤色散的大小和符号的测量。     

Wavelength dispersion characteristics of single-mode fibers in low-loss region

Wavelength dispersion characteristics of single-mode silica fibers in a very low-loss region, including zero dispersion wavelengths, are studied in detail using a "difference method." Wavelength dispersion of single-mode fibers is compared for fibers with same material dispersion but with different waveguide structure. Material dispersion is evaluated by extracting waveguide dispersion from experimental results. Effects of waveguide dispersion on the zero dispersion wavelength of the single-mode fiber in a longer wavelength region are clearly analyzed. Single-mode fiber design consideration is given from the wavelength dispersion point of view.     

Temperature dependence of chromatic dispersion in single mode fibers

This paper describes the temperature dependence of chromatic dispersion in single-mode fibers for a temperature range of -60°- 250°C. Highly accurate dispersion measurements demonstrated a linear relationship (0.025 nm/°C) between the zero dispersion wavelength and temperature for tests conducted below 150°C. Further tests in the high-temperature range showed an increase in this dependence. For both temperature ranges, the results were independent of fiber coating and structure.     

A review of single-mode fibers with modified dispersion characteristics

Standard first-generation single-mode fibers are optimized for operation at a wavelength of 1.3 μm, where they exhibit zero dispersion. By modifying the fiber design it is possible to shift the zero dispersion wavelength to 1.55 μm, where the lowest losses occur in silica-based fibers. Advanced fiber structures can also be designed such that relatively flat dispersion spectra can be achieved over a wide range of wavelengths. In this paper, the theoretical and practical attempts to develop advanced fiber designs have been reviewed.     

Polarization mode dispersion of short and long single-mode fibers

Polarization mode dispersion (PMD) in short and long single-mode fibers was measured by a polarization-maintaining Michelson interferometer. A nonnegligible PMD was found in some standard fibers. The sensitivity enables PMD to measure the bend-induced PMD of a fiber rolled on a 28-cm diameter drum. A theoretical model for PMD with random mode coupling is developed, and an explicit equation for the time-of-flight distribution is presented. Comparison between measurements on short and long fibers with residual birefringence leads to an estimation of the coupling length on the order of 20-30 m     

Interferometric measurements of chromatic and polarisation mode dispersion in highly birefringent single-mode fibres

Interferometric measurements on highly birefringent single-mode fibres have been performed. The group delay spectrum of each polarisation mode is independently measured over the whole 1.0?1.73?m spectral range. The polarisation mode dispersion is obtained by direct subtraction of the group delay spectra.     

单模光纤弯曲损耗的测量与分析

提供了弯曲半径从1．7mm到5．8mm，波长从1520nm到1565nm范围内单模光纤弯曲损耗的测试结果。观察到了弯曲损耗呈震荡变化、随着弯曲半径的增加损耗减小，振幅减小，随着波长的增加损耗增加、振幅增大的现象。并利用光纤的耦合模理论对单模光纤弯曲损耗震荡进行了解释。     

Full characterization of polarization-mode dispersion withrandom-mode coupling in single-mode optical fibers

Theoretical expression has been derived for polarization-mode dispersion with random-mode coupling in optical fiber by simple means. The square-root dependence of polarization-mode dispersion not only on a fiber length but on a mean-coupling length has been experimentally verified for the first time. This characterization became possible only by the use of highly birefringent polarization-maintaining fiber and introduction of fusion splices with desired coupling lengths     

Chromatic dispersion modeling of single-mode optical fibers: adetailed analysis

We present here an efficient method for single-mode fiber modeling. This paper deals mainly with chromatic dispersion computation but the analysis can be extended to other single-mode characteristics. This synthesis shows that key-parameters have to be correctly chosen in order to insure an accurate modeling of chromatic dispersion. Finally, the results we obtained with this method are presented. The agreement between theoretical calculations and measurements is also explained