The breakthrough technology in dry fiber fabrication has opened the possibility for using fiber bandwidths all the way from 1.3 to 1.6£gm. However, the fiber amplifier used in commercial product, such as erbium-doped fiber amplifier (EDFA), can not fully cover the whole fiber bandwidths from 1.3 to 1.6£gm with a single fiber amplifier. Recently, the Cr4+-doped fiber has shown a broadband emission from 1.3 to 1.6£gm. Therefore, it is interesting to develop a single fiber amplifier which can operate the wide bandwidth of the 1.3~1.6£gm emission. In this study, we have successfully fabricated and measured the Cr-doped fibers by using a commercial drawing-tower technique and a rod-in-tube method. The core diameters were 26 and 16£gm. The Cr4+ fluorescence spectrum showed a broadband emission from 1.2 to 1.6£gm. The radiation intensity was up to the order of nW. This indicates that the new Cr-doped fibers may be used as a broadband fiber amplifier. The advantages of using the drawing tower to fabricate the Cr-doped fibers are to have a better control of the core diameter, the fiber uniformity and circularity. Therefore, the Cr-doped fibers may have a potential for commercial production and application to lightwave communication systems.

The breakthrough technology in dry fiber fabrication has opened the possibility for using fiber bandwidths all the way from 1.3 to 1.6 £gm. However, the fiber amplifier used in commercial product, such as erbium-doped fiber amplifier (EDFA), can not fully cover the whole fiber bandwidths from 1.3 to 1.6 £gm with a single fiber amplifier. Recently, the Cr4+-doped fiber has shown a broadband emission from 1.3 to 1.6 £gm. Therefore, it is interesting to develop a single fiber amplifier which can operate the wide bandwidth of the 1.3 ~ 1.6 £gm emission. In this study, we have successfully fabricated and measured the Cr-doped fibers by using a commercial drawing-tower technique. The Cr-doped YAG preform was firstly fabricated by a rod-in-tube method. By employing a negative pressure control in drawing-tower technique on the YAG preform, the Cr-doped fibers with a better core circularity and uniformity, and good interface between core and cladding were fabricated. The drawing speed was up to 200m/min. The core diameters were 26 and 16 £gm and the non-circularity was smaller than 3%. The spontaneous emission spectrum showed a broadband emission of 1.2 to 1.6 £gm with the output power density about a few nW/nm. The Cr-doped fibers fabricated by drawing tower are beneficial when integrated with the standard single-mode fibers and broadband WDM couplers for lightwave communication systems. Therefore, the Cr-doped fibers may be used as a broadband fiber amplifier to cover the whole 1.3-1.6 £gm range of silica fibers and have a potential for commercial production and application to lightwave communication systems.

The fabrication of broadband single-mode Cr-doped silica fibers (SMCDSFs) using the fiber drawing-tower method with the modified rod-in-tube technique is demonstrated for the first time. A preform was assembled by using the grown Cr:YAG rod as core and the silica tube as cladding. The outer and inner diameters of the silica tube are 20 and 7 mm, respectively. The initial dimension of the Cr:YAG crystal rod had a length of 0.03 m and a diameter of 500 £gm. The Cr:YAG crystal was grown into a diameter of a 290 £gm with a length of 0.12 m by the LHPG method. The SMCDSFs had a 6 £gm core and a 125 £gm cladding. The transmission loss was 0.08 dB/cm at 1550 nm. The far-field pattern measurements indicated the single-mode characteristic when the propagation wavelength was longer than 1310 nm. In order to solve the interface of core and cladding, a novel rod-in-tube(RIT) perform was employed by inserting the Cr:YAG crystal rod of 0.03m length and 500 £gm diameter into the silica capillary tube, which had the same diameter with the drilled silica rod. The single-mode Cr-doped fibers had successfully been fabricated and the loss had been reduced to 0.03 dB/cm at 1550 nm with a 5 £gm core and a 125 £gm cladding. Furthermore, the SMCDSFs also had the single-mode characteristic when they operated in the optical communication window. The successful fabrication of SMCDSFs may be one step forward towards the achievement of utilizing the SMCDSFs as ultra-broadband fiber optical amplifiers to cover the bandwidths in the whole 1300 to 1600 nm range of low-loss and low-dispersion windows of silica fibers and a broadband source for enabling high resolution in optical coherence tomography (OCT).

The success in fabrication of Cr-doped fibers (CDFs) with fluorescence of Cr3+ by powder-in-tube (PIT) method equipped with drawing-tower process is demonstrated for the first time. The fluorescence intensity of CDFs by fabricated RIT method is weak because the concentration of Cr-ion in Cr:YAG rod is low. However, the fabrication with powder-in-tube (PIT) provides a better solution to improve the concentration of Cr-ion to enhance the fluorescence of CDFs. The Cr-doped powder was composed of CaO-Al2O3-BaCO3-MgO-Cr2O3 as the material of core and then it was poured into the silica tube with outer diameter of 20 mm and inner diameter of 7 mm (20/7) to yield the perform. The CDFs had a 17.5 £gm core and a 125 £gm cladding. The transmission loss was 0.74 dB/cm at 1550 nm. And the fluorescence intensity of Cr3+ between 800~1200 nm was 50 nW/nm. To reduce transmission loss further, we used multi-tubes to raise the ratio of cladding to core. According to the principle of conservation of mass, the core diameter of CDFs was 5 £gm. The transmission loss was improved more than 50% and it reached to 0.135 dB/cm at 1550 nm. Moreover, a single-mode characteristic of CDF was observed when the propagation wavelengths were longer than 1260 nm. The CDFs were successfully fabricated by using a fiber drawing-tower technique with PIT method. The demonstration of CDFs makes it possible as a new generation broadband fiber amplifier, a tunable NIR fiber laser for sensor applications, and a broadband source for high resolution OCT.

¡@¡@Currently, The Cr-doped fibers are grown by LHPG method or drawing-tower technique. The Cr-doped YAG preform was firstly fabricated by a rod-in-tube method. We have successfully fabricated the Cr-doped fibers by using a commercial drawing-tower technique. By employing a negative pressure control in drawing-tower technique on the YAG preform, the Cr-doped fibers with a better core circularity and uniformity, and good interface between core and cladding were fabricated. The core non-circularity was smaller than 3%, the spontaneous emission spectrum showed the bandwidth that approach to 300 nm, and the output power density level have promoted to a few nW/nm. ¡@In this study, we focused on the analysis of dynamic fluorescent characteristics of Cr-doped fibers in order to improve the quality effectively. The lifetimes of Cr4+ fluorescence and concentration of Cr ions were 1.5 £gs and 510 £gg/g, respectively.The concentration of the Cr ions was less than the Cr-doped fibers grown by LHPG method. The high-resolution micrograph showed that there was nano-crystalline structure in the core surrounded by SiO2 amorphous matrix. These nano-particles gathered at the core and formed micrometer clusters, and therefore resulted in high scattering loss around 1.17dB/cm. ¡@¡@In order to improve the Cr-doped fibers quality, reduce propagation loss, and promote the spontaneous emission power density. We have to decrease the temperature and drawing speed in the drawing process Therefore, the new Cr-doped fibers may have the potential for being used as a new generation broadband fiber amplifier to cover the bandwidth of the entire 1.3-1.6 £gm range which exhibit 300 nm usable spectral bands.

In this study, we will discuss the fabrication detail about the capillary optical fiber and microstructured optical fiber (MOF) from the preform manufacture to the drawing process and apply our capillary optical fiber in a temperature sensor device. First, we discuss the influence of the drawing parameters contribution for the fiber, and we will introduce how to design a preform and discuss how to keep our fibre geometry in drawing process by controlling the drawing parameters. For better fiber products, we need to make some important improvements such as fixing the preform geometry and designing the preform pressure or vacuum input path before the fiber drawing process. In the fiber drawing we want to control the fiber inner diameter and make the interval between three capillary tube disappear. We will solve these problems by different preform making methods or drawing tower hardware design and drawing parameter control. Now we can successfully make single ring hole MOFs by the capillary tube sealed method. But the hole structure is not as good as expectation. We will try to design a pressure and vacuum input device to replace the capillary tube sealed method. And help us to make better and more different MOF structures. We also used our capillary optical fiber to be a temperature sensor. We will describe the principle and the sensing sensitivity of our sensing device in this study. Our temperature sensing device shows a linear relationship between the temperature and operation wavelength, and the sensing sensitivity is 0.038nm/¢XC