VAD technology has been proposed for laser fiber fabrication to improve its productivity and reproducibility. Rare-earth ion, Yb<sup>3+</sup> has been incorporated with Ce<sup>3+</sup> and Al<sup>3+</sup> by the conventional solution doping process. In order to obtain a transparent Yb-doped core rod, the pre-sintering and consolidation process for the large volume of silica soot deposited by VAD has been significantly investigated. In addition, 20/400μm Yb-doped fiber with octagonal cladding has been fabricated. The cladding absorption was 0.44dB/m at 915nm, which corresponds to ~ 0.2mol% of Yb concentration and the slope efficiency with respect to absorbed pump power at 976nm was 66.7%.
We have proposed the systematic measurement of coating geometry for specialty fibers based on dark field illumination technique. The measured dark-field projection image shows clear interfaces between different refractive index materials. Using own developed image processing tool, the interfaces automatically detected and analyzed. Every degree of measurements provides circularity of each layer and then shows the center point of individual layer. Using this technique, coating diameter, coating non-circularity and coating ellipticity for double clad fiber were successfully measured and high resolution camera also detected some of existing coating defect and delamination.
In this study, cylindrical diffusing optical fiber probe (CDOFP) used for tumor treatment using PDT method is developed and analyzed. Diffusing beam profile of 5mm to 40mm tip length probe is produced and analyzed using laser scribing equipment developed in a previous research. Ball tip at the tip of CDOFP was developed for easier infiltration of tissues and the beam profile of such tip is reviewed. Additionally, CDOFP for PDT tumor treatment was used for laser coagulation test on animal tissue. CDOFP with diffusing tip length 5mm and 15mm was infiltrated inside a cow's liver tissue to process laser coagulation test. Coagulation and thermal damage was measured with twice the maximum intensity of laser, where maximum intensity in-vivo test is 1W 200J.
We have proposed a germanium doped core fiber design for large mode area single-mode applications. The designed fiber effective index, dispersion and bend loss of the fundamental mode and next higher order modes have been calculated using the numerical method. The fiber exhibits a high differential loss between the fundamental mode and higher order modes. Therefore, the designed fiber structure effectively suppresses the higher order modes and retains only the first mode (or fundamental mode) in the core region. Our simulation results demonstrate that, a low loss of 0.1dB/m is achieved for fundamental mode at 1060nm wavelength with 10cm bend radius, along with it also exhibits a high loss of 4.8 dB/m to first higher order mode. The fiber shows a large mode area of 831.4 μm<sup>2</sup> at 1060nm wavelength. The proposed paper further explores the fiber properties such as dispersion and fabrication tolerances. Our design shows a dispersion of 39 ps/km-nm at 1060nm, and also the structure shows a less dispersion variation over a wavelength band of 400nm. The fiber reduces the fabrication difficulties as compared to the other designed fibers. We fabricated the present fiber using the renowned vapor axial deposition technique. In this method, we can achieve the large diameter preforms and also the method decreases the tolerances when dealing with glasses.
The treatment using photodynamic therapy (PDT) among cancer treatment methods shows remedial value in various cancers. The optical fiber probe infiltrates into affected parts of the tissues that are difficult to access, such as pancreatic cancer, carcinoma of extrahepatic bile duct, prostate cancer, and bladder cancer by using endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasonography (EUS) with various types of diffusing tips. <p> </p>In this study, we developed cylindrical diffusing optical fiber probe (CDOFP) for PDT, manufactured ball-shaped end which is easily infiltrated into tissues with diffusing length ranging from 10mm to 40mm through precision laser processing, and conducted beam profile characterization of manufactured CDOFP. Also, chemical reaction between photo-sensitizer and laser in PDT is important, and hence the thermal effect in tissues as per diffusing length of probe was also studied as it was used in a recent study.
Although the patients with cancer on pancreas or pancreaticobiliary duct have been increased, it is very difficult to detect and to treat the pancreatic cancer because of its low accessibility and obtuseness. The pancreatic cancer has been diagnosed using ultrasonography, blood test, CT, endoscopic retrograde cholangiopancreatography (ERCP), endoscopic ultrasonography (EUS) and etc. Normally, light can be delivered to the target by optical fibers through the ERCP or EUS. Diffusing optical fibers have been developed with various methods. However, many of them have mechanical and biological problems in the use of small-bend-radius apparatus or in tissue area. This study developed a therapeutic cylindrical diffusing optical fiber probe (CDOFP) for ERCP and EUS which has moderate flexibility and solidity to treat the cancer on pancreaticobiliary duct or pancreas. The CDOFP consists of a biocompatible Teflon tube and multimode glass fiber which has diffusing area processed with laser and high refractive index resin. The CDOFP was characterized to investigate the clinical feasibility and other applications of light therapy using diffusing optical fiber. The results presented that the CDOFP may be used in clinic by combining with endoscopic method, such as ERCP or EUS, to treat cancer on pancreas and pancreaticobiliary duct.
We designed the large mode area photonic crystal fiber structure. We calculated the effective index, and dispersion of fundamental mode using finite difference time domain method. Numerical results show that fiber structure strips higher order modes from the photonic crystal fiber and retains only fundamental mode with 10cm bend. We have shown the results of two types of photonic crystal fibers. The fiber shows negative dispersion from 1.860 μm to 1.996 μm wavelength. We fabricated the photonic crystal fiber structure and analyzed the fabrication difficulties of the fiber design.
We fabricate versatile holey fibers with 6-hole, 18-holes in order to improve their property in terms of
bending insensitivity. The fabricated holey fibers are applied for connection and integration for
compact optical devices.
Biomedical optical imaging technologies based on optical fibers have been of great interest because of their superiority over conventional bulk-optic counter part in size and integration. Flexible endoscope is a key component to deliver the reflected optical signal from biological tissue to the optical imaging system, such as Optical Coherence Tomography (OCT) and Fiber Confocal Microscopy (FCM). However, conventional optical fibers for the biomedical imaging endoscope have been suffered from a critical wiring problem of a fiber waveguide, which induces additional loss severely. In this work, we have shown excellent properties of holey optical fibers with low bending loss under a minimum bending radius of 10 mm or less, which is almost reaching the wiring limit of endoscope. A curled optical patch cord, like a curled telephone cord, is practically demonstrated for the convenient access of imaging probe to the biological target at the flexible distance. The quality improvement of optical imaging is compared to show the great potential for the endoscopic OCT and endoscopic FCM.
We experimentally demonstrate real practical optical curl patch cords based on holey fibers with bending insensitivity.
After making 6-hole holey fibers with the VAD method, the optical curl patch cord with the fabricated holey fiber is
Recently, the use of bend-insensitive fiber in FTTH applications has become a major issue. The R&D center of OPTOMAGIC is in the process of verifying and presenting the possibility of using holey fiber in the telecommunications field through various reliability testing while comparing it to conventional single mode optical fiber.
This paper describes the low attenuation at the 1400nm band of optical fiber, which depends on a deposited first cladding and core diameter ratio (D/d) of core rod on Vapor Phase axial Deposition (VAD) process and a dehydration method. By using the most suitable D/d for much more efficient productivity and the improved dehydration process, we developed Preform for Zero Water Peak Single Mode (ZWP-SM) fiber to produce over 1,300F.km.