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.
Temperature stability based on high Ge-doped fibre Bragg grating (FBG) is presented. A high Ge-doped photosensitive
fibre (PSF) used for writing FBG was manufactured. Temperature characteristic of the FBG from 20 to 300°C had been
researched. The transmission efficiency is about 75% at 300°C.
Two kinds of self-loading Farby-Perot (F-P) fiber sensors were prepared by creating micro-grooves on side-face of
single mode fiber-28 (SMF-28) and photonic crystal fiber (PCF) with 157 nm excimer laser. Self-loading F-P
interference fringe shifts were measured under different temperature, stress and alcohol solution. Temperature sensing
experiments show that the sensitivity of PCF and SMF F-P sensors are 0.0580nm/°C and 0.0535nm/°C when the
temperature ranges from 30 °C to100 °C. The interference fringe shifts of PCF and SMF F-P sensors are 1.6 nm and 2.2
nm when they were loaded with 80 μm elongation along fiber axis, which correspond to stress sensitivity of 1.41pm/με
and 1.50pm/με respectively. The interference fringe shifts of the SMF F-P sensor and the all-solid PCF sensor are
0.4775nm and 0.3490nm when the quality percentage of alcohol changes from 0 to 99.99%.
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 fiber's photosensitivity,
study the fiber's photosensitivity influenced by the doping process. The fiber's data indicate that the high F doped
(5 mol%) Ge/F photosensitive fiber's grating has the 80% reflectivity, much lower than the low F doped (1 mol%)
Ge/F photosensitive fiber's 94% reflectivity. Then the Boron doped would increase the fibre's 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.
With the increasing application in the ultraviolet (UV) area, the fiber's UV transmission performance should be studied.
In UV fibers, however, the presence of Germanium can result in ultraviolet radiation-induced color centers, which are
point defects in the core's silica that generate absorption bands in the UV and visible spectrum that deteriorate the optical
fiber transmission in that spectral region. The fiber's UV transmission performance would be influenced by the fiber
core's doping content. Based on the advanced plasma chemical vapour deposition process, three types of different
doping content fibers were fabricated. With test these fibers' transmission efficiency and stability, study the optimized
doping process of the UV fiber.
The Boron doped would increase the fibre's photosensitivity distinctly just when the dope content reach about 5%. Then
the Boron content would get the saturation to influence the fiber's photosensitivity about 30%.
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 fiber's photosensitivity,
study the fiber's photosensitivity influenced by the doping process. The data indicate that the high F
doped (5%) Ge/F photosensitive fiber's grating has the 80% reflectivity, much lower than the low F
doped(1%) Ge/F photosensitive fiber's 94%. The F doped content can influence the fiber's photosensitivity distinctly.
Single mode fiber (SMF) has been used widely in local and access network since the early 1980's. 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.
In this paper, the DGD (Differential Group Delay) method for beat length measurement of PANDA polarization maintaining (PM) fibers is theoretically analyzed in detailed. And the analysis indicates, regarding the series of silica optical fibers, the error of beat length at different testing wavelength can be ensured less than 2% based on present fiber designs and germanium-doped concentration level. Presently the PMD400 (Polarization Mode Dispersion) analyzer is applied to measure the beat length of polarization maintaining fibers at Yangtze Optical Fiber and Cable Company. Lots of test results shows the DGD method is very reliable, convenient and nondestructive. In practical, the relative deviation of beat length at different wavelength can be kept under 1.5% below based on a number of experimental data. Therefore, the DGD of a PM fiber can be tested at a definite wavelength, such as 1550nm, and then the beat lengths at other operating wavelength can be got according to the relationship between beat length and operating wavelength.
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. It's 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.
In this paper, a 850nm-optimized dispersion-unshifted single-mode optical fiber was introduced. This type of
fiber is completely compatible with G652 series fibers, but its bandwidth at 850nm wavelength has been
optimized in order to fitting the potential applications. This fiber was manufactured by PCVD (Plasma-active
Chemical Vapor Deposition) method. In order to increasing the 850nm bandwidth, the core-RI-profile (Refractive
Index) of this fiber was designed as graded-index profile. With a piece of about 36km length fiber, some relevant
geometric and optical characteristics had been got. The core diameter, MFD (Mode Field Diameter) was about 13
micron and 9.6 micron respectively. The cut-off wavelength and zero-dispersion wavelength was at 1315nm and
1323nm nearly. The attenuation at 1310nm and 1550nm was less than 0.34dB/km and 0.19dB/km respectively.
With all of these results, this 850nm-optimized fiber was completely corresponding with specifications of G652
series of fibers. Meanwhile, OFLB (Over-Filled Launch Bandwidth) test showed the bandwidth at 850nm was
larger than 400MHz.km comparing to about 150MHz.km OFL bandwidth of normal G652 fiber. Because of the
pretty large 850nm bandwidth, this fiber could be possibly used at 850nm wavelength in LAN (Local Area
Network) or DSN (Data-Storage Network) field. In order to validating the compatibility with G652 fibers, the
splice loss between this fiber and normal G652 fiber also had been tested.