Based on PCVD deposition process and Rod-In-Tube draw process, highly nonlinear fibers were designed and fabricated for efficient fiber nonlinearity generation. Highly nonlinear fibers employed high-concentration GeO2-doped core and fluorine-doped cladding were simulated, in which key structure parameters were investigated, such as the core diameter, core profile shape, and the b/a. The fabricated fibers successfully realized a low attenuation less than 1.30dB/km with an effective area of about 10um<sup>2</sup> and a dispersion slope about 0.020ps/nm<sup>2</sup>/km at the operating wavelength of 1.55um. For different applications such as Raman amplifier and four-wave mixing (FWM) generation, a series of fibers were fabricated with different dispersion spectrums in the S+C+L-band. Some application experiments were also introduced, which were related to fiber properties. Our fabricated fibers achieved the maximum effective Raman gain coefficient of 5.08W<sup>-1</sup>km<sup>-1</sup> and the nonlinear coefficient of 12W<sup>-1</sup>km<sup>-1</sup>.
In order to overcome the defects of G.652 and G.655 optical fibers, new types of ITU recommendation G.656 optical fiber are introduced in the paper. Based on the theory of waveguide, the design principle was described. Several types of G.656 optical fiber are introduced here; these types optical fiber can be used for long haul transmission system and metro network. CWDM and DWDM can also be applied on S+C+L bands with these types fiber. These fibers are manufactured by PCVD process. The minimum dispersion value from 1460nm to 1625nm is greater than 2ps/nm km; the maximum value is less than 14ps/nm km. The effective area at 1550nm is around 52 to 66μm<sup>2</sup>. The excellent polarization mode dispersion properties help the fiber to meet the requirement of high bit rate transmission. The PMD co efficiency of these fibers is less 0.05 ps/km<sup>1/2</sup>.
By use of improved PCVD process, excellent attenuation of these fibers was obtained, the water peak around 1385nm is almost removed; attenuation from 1310nm to 1650nm is less than 0.4 dB/km, attenuation at 1550nm is less than 0.22dB/km. Excellent attenuation performance will help the fiber to utilize the bandwidth effectively.
In this paper, we described a new type of wideband communication fiber with low water peak. The new fiber has excellent dispersion performance. It allows WDM technology to be applied on the range: E band to L+ band, which wavelength range is from 1370nm to 1650nm. It has relative low relative dispersion slope called as RDS, which makes high bit rate transmission system be easy to realize full dispersion compensation with low cost. Low water peak characteristics of new fiber provide necessary condition to extend operation range to E band. New fiber has moderate effective area, which makes new fiber have flexible amplification choices. Excellent PMD performance makes new fiber be suitable for higher bit rate transmission system.
A new type of communication optical fiber with S+C+L-bands was introduced in the paper. This optical fiber is designed for the application of DWDM system on S+C+L-bands. The effective operating bands can be even extended to E-band and L<sup>+</sup>-band. In order to reduce non-linear effect, such as FWM (four-wave mixing) etc., the
minimum dispersion coefficient from 1460nm to 1625nm of the optical fiber is greater than 2ps/nm km, and the effective area at 1550nm is around 60μm<sup>2</sup>. Low dispersion slope is helpful to reduce the cost of dispersion compensation for high bit rate DWDM system and maintain a moderate dispersion value over S+C+L-bands. The dispersion slope of this type of fiber was optimized not to be less than or equal to 0.038ps/km nm<sup>2</sup> (over C-band ), the dispersion coefficient isn’t higher than 11.4 ps/nm km at 1625nm. By the optimization of manufacturing process and precisely designing on index profile, excellent attenuation and PMD performance were obtained. Attenuations at 1550nm and 1625nm are less than 0.24dB/km, PMD co-efficient is less than 0.05 ps/km1/2.