Showing papers on "Zero-dispersion wavelength published in 1978"

Self-phase-modulation in silica optical fibers

Abstract: We report measurements of frequency broadening due to self-phase-modulation (SPM) in optical fibers. The use of single-mode silica-core fibers and mode-locked argon-laser pulses leads to the simplest and cleanest measurements yet made of SPM. The qualitative features of the frequency spectrum are in good agreement with theoretical expectations. The experiment provides an independent measurement of ${n}_{2}$, the self-focusing coefficient. The results also point to some simple and useful techniques based on fibers for the measurement and analysis of mode-locked laser pulses.

Narrow-band Bragg reflectors in optical fibers.

Abstract: The formation and characterization of narrow-band-waveguide reflection filters in Ge-doped silica optical fibers is described. The filters can have complex response profiles and are tunable in frequency by mechanical strain.

Material dispersion in lightguide glasses

Abstract: Material dispersion measurements are reported on six characteristic lightguide glass compositions. The measurements were made on bulk specimens and cover the wavelength range from 0.8 to 1.5 μm. It is observed that in these silicate glasses the wavelength at which material dispersion is zero is in all cases greater than 1.2μm.

Polarization mode dispersion in single-mode fibers

Abstract: In real single-mode optical fibers, imperfections cause the two possible polarizations to propagate at different phase velocities This birefringence leads to different group velocities We have measured the resulting mode dispersion in short fiber lengths (05-25 m) from the depolarization of broad-bandwidth light In a typical fiber we found 30 psec/km at 069-microm wavelength, in good agreement with the observed birefringence The effect of mode dispersion can be compensated by a +/-68 degrees double twist midway along the fiber, interchanging the fast and slow modes

A universal fiber-optic (UFO) measurement system based on a near-IR fiber Raman laser

Abstract: A universal fiber-optic measurement system, which is useful for measuring loss and dispersion in the 1.06-1.6 \mu m wavelength region, is described. The source is a silica fiber Raman laser pumped by a mode-locked and Q -switched Nd:YAG laser at 1.06 μm. Subnanosecond multiple-Stokes pulses in the 1.1-1.6 \mu m wavelength region are generated in a low-loss single-mode silica fiber. The use of this near-infrared fiber Raman laser for characterizing various transmission properties of single and multimode test fibers is demonstrated. Loss spectra, intramodal dispersion, and intermodal dispersion data are obtained in the wavelength region of minimum loss and minimum material dispersion for silica fibers.

ZnCl2 glass: A potential ultralow‐loss optical fiber material

Abstract: Zinc chloride glass is a potentially useful medium for ultralow‐loss (∼1 dB/103 km) optical fibers for wavelengths in the 3.5–4‐μm region. In this region, intrinsic absorption, scatter, and material dispersion are all expected to be small, and the common fully oxidized transition metal impurities and H2O should exhibit extremely weak absorption as well.

Fusion splices for optical fibers by discharge heating

Abstract: A new type of electric discharge fusion splicing apparatus for optical fibers offering several advantages is developed and evaluated. An average splicing loss of 0.10 dB is obtained for step-index multimode silica fibers with a 60-μm core diameter. Tolerances in discharge energy, fiber misalignment, compression force and stroke length during fusion, and end face conditions are discussed experimentally. No accurate fiber axis adjustment is necessary in this apparatus. Mechanical strength of the splice is also excellent.

Direct measurement of wavelength dispersion in optical fibres-difference method

Abstract: A new method is described for direct and precise measurement of wavelength dispersion in the core of an optical fibre over a wide wavelength region.

Truncated Parabolic-Index Fiber with Minimum Mode Dispersion

Abstract: The use of a parabolic-index fiber as an optical transmission line has been receiving extensive attention because of its excellent mode dispersion characteristics. In the present paper, the modal dispersion in the optical fiber with truncated parabolic index distribution is analyzed theoretically in detail by using a variational method. Taking the influence of the cladding upon the propagating modes into consideration, it is found that there exists an optimum index distribution for which the modal dispersion is minimized. The standard deviation of the normalized group delay of propagating modes is used to estimate the modal dispersion behavior of the fiber.

Low-loss single-mode fibers with different B(2)O(3)-SiO(2) compositions.

Abstract: Design considerations, fabrication, and transmission characteristics of single-mode optical fibers made with different borosilicate compositions are discussed. Fibers with core sizes as large as 15 microm and refractive-index differences below 0.1% were made with the modified chemical vapor deposition (MCVD) process. Minimum losses achieved with fibers up to 1-km lengths were 1.3-1.4 dB/km in the 1.02-1.1-microm range. Microbending losses were avoided by jacketing the fibers with silicone resin. Single-mode operation is maintained in moderately overmoded fibers (V ~ 3.0) because of leakage loss through a finite cladding thickness and because of bends in the fiber axis.

Splice loss evaluation for optical fibers with arbitrary-index profile.

Abstract: A method is presented for calculating offset and tilt losses for fiber splices with axially symmetric arbitrary-index profiles by approximating the profile with a staircase function. This method is applied to a large-core dual-mode fiber with zero intermodal dispersion as well as to single-mode fibers with step- and parabolic-index profiles. When a splice loss of 0.2 dB is permitted, the normalized offset misalignment is found to be D(N) = 0.635 for the dual-mode fiber at normalized frequency v = 4.605 and a power-law exponent alpha = 4.5. The D(N) value compares favorably with the values 0.560 and 0.614 for conventional step- and parabolic-index single-mode fibers, respectively. The dual-mode fiber is superior to the step- and parabolic-index fibers with respect to permissible splice offset tolerances.

Profile dispersion effects on transmission bandwidths in graded index optical fibers

Abstract: Transmission bandwidths of optical fibers would be maximized if their refractive index profiles were optimally graded. However, dispersive differences between fiber material constituents make the optimal power law profile exponent α depend on wavelength. This profile dispersion effect is significant for germanium borosilicate fibers and makes their observed transmission bandwidths change by more than 300 percent within a 650-1050 nm wavelength range. Measurements are made in spectrally filtered white light from a xenon arc lamp that is sinusoidally modulated by an electrooptic crystal. Reduction of sine wave envelope intensity due to transmission in a fiber gives its baseband frequency response. The functional dependence of bandwidth on wavelength is used to diagnose whether α is larger or smaller than the optimal value which minimizes intermodal dispersion at particular wavelengths.

Pulse dispersion properties of fibers with various material constituents

Abstract: Intermodal dispersion properties are compared for high silica fibers with borosilicate (B 2 O 3 -SiO 2 ) and germania borosilicate (GeO 2 -B 2 O 3 -SiO 2 ) graded-index profiles. Pulse transmission measurements were systematically correlated with profile shapes so that new fibers could be fabricated with closer-to-optimal profile gradients at a wavelength of 907.5 nanometers. Germania borosilicate fibers with power law profile exponents (α ≈ 2.03) lowered intermodal dispersion 50 times from the result expected for comparable step-index fibers with N.A. ≈ 0.19. By contrast, borosilicate fibers with α ≈ 1.78 caused a 100-fold pulse width reduction in fibers with N.A. ≈ 0.14, corresponding to a 2σ = 0.13 ns/km pulse-broadening rate.

Optical fiber (800-Mbit/sec) transmission experiment at 1.05 microm.

Abstract: An 800-Mbit/sec optical fiber transmission experiment at the 1.05-μm wavelength is reported. Single frequency output of a LiNdP4O12 laser is modulated with a guided-wave LiNbO3 modulator in an NRZ code and is transmitted through 4-km long single-mode fibers. The minimum receiving level is −30 dBm using a Ge avalanche photodiode. It is shown that, since the repeater spacing is limited by loss rather than dispersion in the present system configuration, a more than 10-km repeater spacing seems to be feasible. Distinctive features and problems associated with the system and constituent devices are discussed.

Nonlinear pulse propagation in optical fibers.

Abstract: We discuss the propagation of nonlinear optical pulses in fibers. The wave equation is solved taking the radial dependence in an average way. The radius versus wavelength curves for "no dispersion" in SiO(2) glass are calculated and plotted. These no-dispersion curves separate the regions of light and dark solitons supported by the fibers.

Pulse broadening in long-span single-mode fibers around a material-dispersion-free wavelength

Abstract: Broadening of short optical pulses propagated along 10.4- and 6-km-long single-mode fibers was measured at a wavelength of 1.293 μm. The fiber core was made of germanium-doped silica glass, and the cladding was pure silica glass. The average loss was 1.33 dB/km on ten pieces about 1 km long. Measured dispersion was 3.9 psec/km/nm for 10.4-km-long fibers, which is in good agreement with the theoretical result obtained by taking the waveguide as well as material dispersion into account. The present experiment confirms that it is beneficial to use the 1.3-μm wavelength region for large-capacity digital transmission.

Light wavelength multiple branching system

Abstract: PURPOSE:To obtain the light wavelength branching filter of low coupling losses and less deviations for respective wavelength bands by subsequently arraying the band- pass filters using interference films from the wavelength bands of larger optical fiber transmission losses. CONSTITUTION:In the transmission path, the wavelength at which the optical path length in glass bulk 10 for the wavelength giving maximum loss is first taken out, whereby the reduction in losses is accomplished. The losses of the respective wavelengths become smaller in the order of lambda1, lambda8, lambda4, lambda2, lambda3, lambda7, lambda5, lambda6. For this purpose, interference film band-pass filters are arrayed in the order of 21, 28, 24, 22, 23, 27, 25 so that the optical path lengths in the bulk become subsequently longer. As a result of such constitution, the loss fluctuations of transmission systems by the transmission line and multiple branching circuit may be reduced.

Launch dependent loss in short lengths of graded-index multimode fibers.

Abstract: In this paper we describe the effect of different launching conditions on the loss measured with a calorimeter in short (~1-m) lengths of multimode optical fiber. A qualitative description of the relation between the energy distribution in the fiber and various excitation variables is given, and many examples are presented that illustrate the effect that launch conditions have on the fiber loss. The use of launch-dependent loss phenomena to diagnose loss mechanisms in optical fibers is discussed. In particular, loss plots are shown for two germania-doped silica-core fibers that indicate a strong absorption loss mechanism located deep within the fiber core.

Wavelength dependence of modal dispersion in graded-index optical fibres

Abstract: We describe a method based on the selective mode excitation at different wavelengths for studying the profile dispersion influence on the modal dispersion. By using this technique, we are able to determine either the optimum wavelength at which the fibre should be operated or the correction needed for optimising the index profile at a given wavelength.

Optimum operating wavelength for chromatic equalisation in multimode optical fibres

Abstract: Complete chromatic equalisation is not possible in a graded-index fibre owing to the variation of material properties across the core. We show that it is still possible to choose an operating wavelength which effectively eliminates first-order material dispersion.

Zinc chloride optical fibers for transmission in the infrared

Abstract: ZnCl 2 optical fibers are advantageously used for transmission of radiation in the infrared portion of the spectrum. Losses as low as 10 -3 dB/km may be obtained when radiation of wavelength between 3.0 and 4.5 microns is transmitted in such fibers. Fabrication techniques allow for the formation of graded fibers to further improve transmission characteristics.

Dispersion in optical fibers: new aspects.

Abstract: Group delay differences among modes, which limit the bandwidth of optical fibers, arise not only from distortions of the refractive profile but also from profile dispersion caused by the dependence of the profile contour on wavelength. An efficient method is presented which helps to explain the interaction of both effects, shows a new way of minimizing the total dispersion by matching the two effects, and simplifies the calculation of pulse broadening in imperfect real fibers.

Material dispersion in quartz glass fiber waveguides

Abstract: The dispersion of the refractive index n (λ) of the core (GeO2+SiO2) and cladding (SiO2) of a two-layer fiber blank was determined in the wavelength range 0.8–2.6 μ similar determinations were made for KV, KSG, and KV70 (anhydrous) quartz glasses. The spectral distribution of the material dispersion (λ /c)(d 2n /dλ 2) and numerical aperture of the waveguide layer were determined. Zero material dispersion of various samples of pure SiO2 was observed in the range 1.26–1.30 μ and similar results were obtained for the fibers at 1.3 to 1.32 μ. The near-field method was used to determine the spectral distribution of the aperture of a glass fiber waveguide drawn from the prepared blank and it was found that the material dispersion in the finished waveguide was the same as in the blank (within the limits of the experimental error). In the 1.6 μ range, where the total losses in the waveguide were less than 1 dB/km, the material dispersion amounted to 24 psec (nmkm)−1.

Fiber-Optical Transmission Between 0.8 and 1.4 /spl mu/m

Abstract: The present state of the art and expected development in discrete components for Fiber-optic transmission systems are reviewed. Predicted performance of fiber systems in the 0.85, 1.06, and 1.27 /spl mu/m regions is presented, and the advantages of longer wavelength operation quantified. Itisconcluded that operation near 1.27 /spl mu/m is particularly attractive for a) moderate data rate systems employing LED's and multimode fibers whose chromatic dispersion and attenuation are greatly reduced compared with 0.85 and 1.06 /spl mu/m, and b) high data rate systems employing lasers and monomode fibers. In systems employing lasers and graded index multimode fibers, the advantage of 1.27/spl mu/m versus 1.06 /spl mu/m operation is not as pronounced, although transmission distances at both of these longer wavelengths are significantly increased from those at 0.85 /spl mu/m.

Fiber-optical long-distance telecommunication line operating at the wavelength of 1.3 μ

Abstract: A 2-km fiber-optical telecommunication line was investigated. Specially developed new semiconductor heterolasers, emitting at the wavelength of 1.3 μ, and low-loss optical fibers were used in this line. The energy characteristics of the new lasers were found to be suitable for data transmission over tens of kilometers.

Delay equalizer for optical fiber transmission path

Abstract: PURPOSE:To make possible transmission of a wide band in the wavelengths other than zero dispersion wavelength of the transmission path by constituting the wavelength dispersion of the transmission path through the use of the photo circuits consisting of two lenses and four diffraction gratings CONSTITUTION:Diffraction gratings 2 and 3, 4 and 5 are so disposed as to oppose with each other and become parallel with each other The exit light from a transmission path 7 passes through a lens 1 then through the respective diffraction gratings and enters a photo detector 8 out through the lens 6 The dispersion value of the transmission path may be made zero at a certain wavelength and the delay time by wavelengths may be equalized by finely adjusting the distances l between the four diffraction gratings Since this delay equalizer for optical transmission path is so constituted as to compensate the wavelength dispersion of the transmission path by the photo circuits, the total dispersion may be made zero even in transmission of wavelengths other than the zero dispersion wavelength and an extra wider band may be realized

Profile dispersion measurements for optical fibres over the wavelength range 350 to 1900nm

Abstract: Pulse spreading in multimode optical fibres is caused primarily by a) transit-time differences which exist between modes and b) material dispersion effects which are apparent when using non-monochromatic sources. The resultant pulse spreading may be minimised, respectively by designing graded-core fibres with optimal refractive-index profiles, and by operating in the wavelength range 1.27-1.35µm, where the material dispersion effect is small. In order to optimise refractive-index profiles in this longer-wavelength region it is essential to possess accurate refractive-index data on commonly-used fibre materials over a wider spectral range than has been hitherto available. In this paper we present for the first time results giving the required optimum index profile over the extended wavelength range 350nm to 1900nm, thus allowing fibre design for the 1.3µm region. Furthermore, the expansion which has been achieved in the wavelength range of the measurements has resulted in a considerable improvement in accuracy over the results reported previously.

Decreasing method for connection loss of optical fiber cable

Abstract: PURPOSE:To reduce the coupling losses owing to construction parameter differences by containing the optical fibers of the same parameter structure within the same groups of optical fiber cables and connecting the optical fibers within the same group with each other at the cable connecting. CONSTITUTION:Optical fibers 10 are divided to regions 11 thru 14 varying with construction parameters such as core diameter, refractive index difference, outside shape, ellipse, eccentricity and refractive index distribution. If the optical fibers of each of the regions 11-14 are trisected to the same groups 21-24 of the optical fiber cables 20A-20C and the optical fibers in the same groups 21-24 are connected with each other at the connecting of the cables 20A-20C, then the optical fibers of the same construction parameters are connected and the coupling looses owing to the differences in the construction parameters decrease.

Reliability of Dynamic Fatigue Data for Plastic Coated Fused Silica Optical Waveguide Fibers

Abstract: The reduction in strength of glass fibers under stress and in the presence of moisture or water follows a log stress vs. log time to failure dependence theoretically and experimentally. Errors in the acquisition of fatigue data for plastic coated fibers are minimized when the time dependent parameter in the dynamic case is actual time to failure and not strain rate. Also for those fibers tested in humid or water environments, the transport time of water through the fiber coating must be considered for those systems demonstrating a time and/or temperature dependence of transport. The time dependent reduction in strength by slow crack growth is fatigue and its rate is given by the slope of the log stress vs. log time to failure curve. The intercept of this curve is the "instantaneous" strength. For plastic coated fibers this intercept shows marked reduction in a water environment as compared to drier ambient conditions. This reduction is attributed to surface energy decrease, but this concept has not been rigorously researched. Slope and intercept data given for a variety of plastic coatings on fused silica fiber and compared statistically in ambient and water environments, enable engineering worst case predictions of lifetime to be made. These predictions, however, are for fibers having high instantaneous strengths in > 20 Km lengths and are therefore not representative of fibers exhibiting low proof-test strength levels. Also, the possibility of interfacial coating-glass interactions occuring and having adverse effects on these predicted fiber lifetimes is not considered.

Modal caustics and dispersion mechanism in optical fibers.

Abstract: Modal dispersion is explained through the frequency dependence of modal caustics in the ray optics treatment of propagation in multimode optical fibers. Examples are shown for different index profiles that give rise to dispersion equalization or deterioration.