The numerous potential applications of UV-induced fiber Bragg gratings (FBGs) in fiber optic sensing and
telecommunication have generated a significant interest in this field in recent years. However, two major factors-the
photosensitivity of the fiber in which the grating is written and the thermal stability of the grating-are of prime
importance in terms of choosing the most appropriate fiber to use and of the long-term functionality of the grating over a
wide range of temperatures. Based on the plasma chemical vapor deposition (PCVD) process, the high Ge (Germanium)
and Ge/B (Germanium/Boron) co-doped photosensitive fiber were developed. It is mature technique that to precise
control the dopant quantity by PCVD process. The photosensitive fibers with different doping composition and doping
concentration have been studied. Based on the experimental results obtained from studies of several kinds of
photosensitive fiber on both the photosensitivity and the temperature sustainability of the FBGs written into them, the
experimental results exhibit that the Boron dopant brings deleterious influence on the FBG's high-temperature
sustainability. The FBG sustainable temperature will become lower than 500°C when the Boron concentration reaches
14% in germanium highly doped photosensitive fiber.
Quartz optical fiber or preform is composed of core and cladding with different refractive index (RI). Their compositions are different from the core to cladding in order to acquire desired RI profile. The physical properties from core to cladding are different, such as thermal expansion coefficients, thermal capacity and glass transition temperatures, which have much effect on the properties of optical fiber. The material composition and structure in PCVD single mode (SM) fiber was introduced in this paper. The composition of PCVD SM fiber was SiO2-GeO2-F-(Cl). F acted as a water-getter to reduce water peak besides lowering the RI of quartz glass and GeO2-F co-deposition was adopted in PCVD fiber. The functional graded material (FGM) design in PCVD SM fiber, which can reduce the attenuation, PMD, splicing loss and improve microbending resistance, was analyzed and discussed.
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.
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, 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 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.
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+-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 60μm2. 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 nm2 (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.