Dispersion Compensating Fibers

The negative dispersion slope of dispersion-compensating fibers has been optimized by increasing the width of the depressed cladding. Simultaneous compensation and dispersion slope has been demonstrated on an actual link.

Design and manufacture of dispersion compensating fibre for simultaneous compensation of dispersion and dispersion slope

We have demonstrated the fabrication of multichannel fibre Bragg gratings (FBGs) in which the dispersion and the central wavelength are adjusted in each channel. The multi-channel character is achieved by superimposing many gratings on a section of an optical fiber. The adjustment of the central wavelength is precise within /spl plusmn/10 pm. The precision of the dispersion adjustment is close to /spl plusmn/2% which renders possible third-order dispersion compensation.

Multi-channel fiber Bragg gratings for dispersion and slope compensation

A dispersion compensating optical fiber, together with a dispersion-shifted fiber that provides zero dispersion in a 1.5-micron wavelength range and guides signal light in a 1.5-micron or 1.6-micron wavelength range, can compose an optical transmission line, which provides improved transmission characteristics and efficient dispersion compensation. The total dispersion slope of an optical transmission line is improved while the dispersion of a dispersion-shifted fiber is well compensated for. The dispersion compensating optical fiber has a triply-cladded structure including first, second and third cladding layers applied in sequence over the core. The difference in relative index of refraction between regions as well as their outside diameters are optimized while the dispersion of the dispersion-shifted fiber is compensated for so that an optical transmission system with a desirable total dispersion slope can be realized.

Dispersion compensating fiber

The invention relates to a dispersion compensating optical fiber which is connected to an optical fiber having a positive dispersion value at wavelength band of 1.55 μm and concurrently has a function of compensating dispersion of optical fibers having a positive dispersion value and a function acting as an optical transmission line, and relates to a wavelength division multiplexing optical transmission line using the dispersion compensating optical fiber. The refractive index profile of the dispersion compensating optical fiber is determined to be W-shaped. 1.0%≦Δ1≦1.4% and −0.45≦Δ2/Δ1≦−0.285 are established where the relative refractive index difference of said center core ( 1 ) with respect to said cladding ( 3 ) is Δ1 and the relative refractive index difference of said side core ( 2 ) with respect to said cladding ( 3 ) is Δ2, and further 0.4≦Ra≦0.5 is established where the value Ra (Ra=a/b) of the outer diameter a of the center core ( 1 ) with respect to the outer diameter b of the side core ( 2 ) is Ra. The dispersion slope at a wavelength of 1.55 μm is negative, and the dispersion value σ is −50 ps/nm/km≦σ<−20 ps/nm/km, wherein the transmission loss is 0.25 dB/km or less, the polarization mode dispersion value is 0.15 ps/km ½ or less, and the mode field diameter is 5.5 μm or more.

Dispersion compensating optical fiber, and wavelength division multiplexing transmission line using a dispersion compensating optical fiber

Summary form only given. We report results of large volume production of more than 10000 km of dispersion-compensating fibers (DCF). This is equivalent to more than 1000 modules, which each can compensate 60 km of standard fiber. Reproducible large volume production of DCF is a difficult task. The design is very sensitive towards small variations in the index profile. For example, we find for our design that a 1% variation of either the core diameter or core index results in a change in dispersion of 5 and 2.5% respectively. Another challenge is to obtain low polarization-mode dispersion (PMD). DCF is more than one order of magnitude more sensitive to core ovalities than conventional telecommunication fibers due to the high core index used. Therefore extreme care has been taken to avoid core ovalities. At the same time we stimulate the mode coupling by introducing oscillatory twist into the fiber during draw. Enhanced mode coupling not only reduces the PMD, but also gives a more stable PMD value, for example during temperature cycling of DCF modules.

D. Jacobsen

Papers

Large volume manufacturing of dispersion compensating fibers