Feng Tu

Low birefringence depressed cladding photosensitive fiber

The highly Ge-doped photosensitive fiber (PSF) has been widely used in the fabrication of fiber Bragg gratings (FBGs). Its birefringence and cladding mode coupling characteristics greatly influence FBGs transmission feature in communication application areas. In this work, a new concept of the PSF is introduced which, along with an optimized birefringence design, a precisely controlled fabrication process, and a cladding mode depressed design, results in a written FBG with -25-dB clad mode-depressed ratio and a polarization mode dispersion value less than 0.045 ps.

The influence of fiber's photosensitivity by doping process

With the rapid development and widely used of fiber grating, the demand of high quality photosensitive fiber has increase greatly. Based on the plasma chemical vapor deposition (PCVD) process, the Ge/F co-doped photosensitive fiber was developed. Through analyze the fibers photosensitivity, study the fibers photosensitivity influenced by the doping process. The data indicate that the high F doped (5%) Ge/F photosensitive fibers grating has the 80% reflectivity, much lower than the low F doped(1%) Ge/F photosensitive fibers 94%. The F doped content can influence the fibers photosensitivity distinctly.

Research on the FBG's high-temperature sustainability influenced by the doping process

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 and high speed drawing process, the high Ge (Germanium) doped photosensitive fiber were developed. It is mature technique that to precise control the dopant quantity by PCVD process and fiber defects control by the drawing process. The photosensitive fibers with same doping process and drawing process 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 drawing temperature and drawing tension influence on the FBGs high-temperature sustainability. The drawing tension would influence the FBGs high-temperature sustainability greater than the drawing temperature.

Material composition and structure design in PCVD silica-based single-mode fiber

Single mode fiber (SMF) has been used widely in local and access network since the early 1980s. Fiber loss reduction will accelerate the construction of various transmission systems with longer repeater spacing. It has been reported that the transmission loss in SMF increases due to residual stress, which is caused by viscosity mismatch between the core and cladding material. The idea of viscosity matching is to match the viscosity of core and cladding doping to minimize the viscosity difference on the cross-section of the fiber or preform. The dopant concentrations can be chosen so that the viscosity of core and the cladding are equal in ideal step index fiber. However, all the reported viscosity-matching design is based on single dopant, for example, only GeO2 is doped in the central core and only F in the cladding. In this paper, optical loss reduction through viscosity-matched design for the SMF with GeO2-F codoped silica core and cladding is described. The impact of viscosity-matching on optical loss of silica-based single-mode fiber has been investigated in detail theoretically and experimentally based on PCVD fiber. For PCVD optical fiber, F is introduced in core is to reduce the water peak. Single mode optical fiber with low attenuation fabricated by PCVD process can be gotten through viscosity-matching design between core and cladding. Viscosity-matching can reduce the sensitivity of attenuation to drawing tension. The model for estimating the viscosity matching has been deduced, which can not only be used for conventional SMF but also for the fiber with arbitrary index profile.

Development of PMF for high precision fiber optic gyroscope by PCVD based process

In this paper, we describe a development of a polarization-maintaining fiber by PCVD based process which can be used in the high precision gyroscope and present its measured properties. This kind of fiber is designed as the reduced cladding PMF. The fabrication of the polarization-maintaining fiber is based on the PANDA PMF PCVD based process. Thus, with the reduced cladding, the fiber has better bending properties. Fabrication by the PCVD process, the fiber also has good longitudinal uniformity and a low-loss about 0.374dB/km @ 1310nm, 2.0mm beatlength and -30dB/km crosstalk. Its environmental performance of crosstalk is also good for fiber optic gyroscope. These better properties make this fiber can be used in the high precision gyroscope system.

Research on the FBG's high temperature sustainability influenced by the drawing process

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 and high speed drawing process, the high Ge (Germanium) doped photosensitive fiber were developed. It is mature technique that to precise control the dopant quantity by PCVD process and fiber defects control by the drawing process. The photosensitive fibers with same doping process and drawing process 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 drawing temperature and drawing tension influence on the FBGs high-temperature sustainability. The drawing tension would influence the FBGs high-temperature sustainability greater than the drawing temperature.

Research on the optical fiber's photosensitivity influenced by the doping process

Based on the plasma chemical vapor deposition (PCVD) process, the Ge/F (Germanium/Fluorine) and Ge/B (Germanium/Boron) co-doped photosensitive fiber was developed. Through analyze the fibers photosensitivity, study the fibers photosensitivity influenced by the doping process. The fibers data indicate that the high F doped (5 mol%) Ge/F photosensitive fibers grating has the 80% reflectivity, much lower than the low F doped (1 mol%) Ge/F photosensitive fibers 94% reflectivity. Then the Boron doped would increase the fibres photosensitivity distinctly just when the dope concentration reach about 5 mol%. Present the experimental study of the influence of doping on fiber photosensitivity. Through measuring the attenuation spectra and comparing the reflectivities of the fabricated fiber Bragg gratings (FBGs), the photosensitivity of GeF and GeB co-doped fibers are investigated.

Study of doping process influence the fiber's photosensitivity

This study indicate that the Fluorine doped would influence the fibers photosensitivity. The Boron doped would increase it distinctly when the dope content reach 5%. Then it would get the saturation on about 30%.

Low PMD Chirp Fiber Bragg Grating Based on the Low Birefringence Photosensitive Fiber

In this paper, a new kind of low birefringence photosensitive fiber is introduced. Fabricated with this new photosensitive fiber, the chirp fiber Bragg gratings PMD performance could be optimized.

New concept photosensitive fiber

The high Germanium (Ge) doped photosensitive fiber was widely used for Fiber Bragg Grating (FBG) applications. Its birefringence and cladding mode coupling characters greatly influence the FBGs transmission character. A new concept of photosensitive fiber was introduced, with the optimised birefringence and cladding mode depressed design. The FBG write by this new fiber has ~25dB clad mode-depressed ratio and its PMD value were less than 0.045ps.