Low water peak single mode fiber (LWP-SMF) fabricated by PCVD based process has been described. Based on the whole process of PCVD fiber, the hydroxyl contamination and its sources are as follows: (1) raw material, such as SiCl4, GeCl4, O2, C2F6, substrate tube and jacket tube; (2) leakage of the system including PCVD and collapsar; (3) surface contamination. The latter purification of deposited glass is extremely difficult, so the most effective solution is prevention. The hydroxyl contamination prevention and elimination measures, such as purity improvement of raw material, online purification during PCVD, surface absorption reduction and dilution effect with large preform, which are the key factors for LWP-SMF fabrication by PCVD based process, are revealed. Large scale production has revealed that LWP-SMF can be fabricated by PCVD based process combined with above mentioned process innovation. PCVD LWP-SMF complies with or exceeds the ITU recommendation G.652 (C and D) and IEC 6093-2-50 type B 1.3 optical fiber specification. With further development of high purity raw material, machine-airproof improvement and larger preform (above 150mm) combined with material composition and structure optimization in optical fiber or preform, high performance PCVD LWP-SMF with lower water peak or even zero-OH performance will be achieved. Besides, other type of optical fiber with low water peak, such as G.653, G.655 and G.656, can also be made with the advanced PCVD based process.
In this paper, a novel fiber manufacturing process based on PCVD is introduced. The fiber drawing length per preform can reach more than 5,000 km and the cost is lower. The fiber shows better optical and geometrical properties. Such large size preform combines the advantages of PCVD process for high quality and OVD process for low cost. This PCVD RIC process will be helpful for increasing the ability of inside vapor deposition process.
A kind of new single mode optical waveguide has been designed and it is prepared by PCVD process. The design and the characteristics of the optical waveguide are studied and discussed in the paper. The waveguide structure of multi-core layers is adopted. Two types of designs, concept-a and concept-b are analyzed and compared. The characteristics of the optical waveguide based on concept-b are very excellent. It is a kind of non-zero dispersion shift optical fiber (NZ-DSF). The zero dispersion wavelength(λ0) is about 1390nm and the absolute value of dispersion from 1200nm to 1625nm is lower than 14 ps/(nm×km). The typical mode field diameter of this optical waveguide is 9.1 um. However, its cut-off wavelength(λc) is not higher than 1200nm and it is much lower than that of existing non-zero dispersion shift optical waveguide, but the bending resistance property of the optical waveguide is excellent. The Macro-bending loss at 1625nm is about 0.019 dB/turn when the spindle diameter is 32mm. Besides, it has low attenuation in the broad spectrum; especially the water peak is lower than 0.34 dB/km. It has super-broad spectrum, from 1200nm to 1625nm, transmission capability as single mode optical waveguide, so it can be used in the high transmission speed DWDM system.