Chang-Hyun Jung

Ultralow bending loss fibers with higher-order mode strippers

We propose and demonstrate bend-insensitive fibers equipped with higher-order mode strippers. The mode stripper is realized by filling a section of air holes with epoxy to attenuate any higher-order modes that are excited at fiber junctions and are confined by the air holes surrounding the core. We found that the higher-order modes are well suppressed with 5 cm-long epoxy columns. An ultralow bending loss of 0.025 dB/turn at a bend diameter of 10 mm, together with single-modeness, is experimentally demonstrated in a bend-insensitive fiber with six air holes 16 μm in diameter.

Flexible Curled Optical Cord for Bending-Insensitive Optical Imaging Delivery

In the application of optical imaging technologies to the biomedical field, the flexible optical cord is one of the key components used to deliver the reflected optical signal from the internal biological tissue to the biomedical imaging system. However, the conventional optical fibers suffer from a critical wiring limitation, which results in severe power losses under a small bending radius that is less than a few centimeters. In this paper, we demonstrate that holey optical fibers with 18 air holes in cladding have negligible bending loss under a minimum bending radius of 3 mm. Excellent bending insensitivity of the holey fibers can effectively reduce the device size and space, which will be highly beneficial to the flexible endoscopic common-path optical coherence tomography system. A curled optical cord, similar to a curled telephone cord, is specially designed and fabricated to accommodate access of the imaging probe to the biological target at flexible distances. The curled optical cord displays excellent optical properties of a much lower bending loss and better optical imaging quality, but the attenuation and insertion losses are still the same as that of a conventional single-mode fiber-based optical cord.

All normal dispersion fiber with large mode area at 2 micron wavelength

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.

Cladding mode suppression in bend-insenstivie fiber with epoxy-filled air holes

Reduction of bending loss has been recognized as an important aspect in optimizing single mode fibers for FTTH applications. Recently, introduction of several air holes around a germanium doped core has been intensively investigated for bending loss control [1]. Such a fiber is called a bend insensity fiber (BIF). Usually larger air holes result in low bending loss for the core mode. However, the air hole layer forms another waveguide additional to the core, and there exist inner cladding modes guided with low loss. The cladding modes are excited at imperfect splices with single mode fiber, and they cause modal interference and intensity fluctuation. The trade off between the low bending loss and the cladding mode suppression, therefore, has been a main issue in design of BIFs.

Fabrication and characteristics evaluation of PANDA polarization-maintaining optical fibers with B 2 O 3 SAP's by VAD method

We investigated the PANDA type polarisation-maintaining optical fibers which were drawn VAD synthesized preforms with stress-applying parts(SAP) by VAD method. The fabricated fiber has 1.3 mm beatlength in the 633 nm region, and −25 dB/km crosstalk. So ths fiber can be used in precision gyroscope system.

Improvement of optical characteristics of holey fibers and their applications to connection and integration for fabrication of compact optical devices

We investigate the optical characteristics improvement of holey fibers with the low bending loss fabricated by VAD method. The proposed holey fibers are applied to connection and integration for fabrication of compact optical devices.

Fabrication of holey-fiber-based optical patch cords with bending insensitivity and their feasible reliability

We propose the holey-fiber-based optical cord cables with the excellent optical characteristics in terms of attenuation loss, insertion loss, and bending loss for the application to access network like FTTH. The attenuation loss of the holey-fiber- based cord cable with the length of 1 km at 1383 nm is as low as ~0.323 dB/km. The bending loss under the bending diameter of 5.5 mm is measured to be ~0.04 dB. We also test the proposed holey-fiber-based optical cable for E-PON transmission systems by measuring the internet speed in the server under the bending diameter of 7, 3, and 1 cm.

Improvement of optical characteristics of holey fibers and their applications

We investigate the optical characteristics improvement of holey fibers with the low bending loss fabricated by VAD method. The proposed holey fibers are applied to connection and integration for fabrication of compact optical devices.

Curled optical patch cord for bending insensitive biomedical imaging endoscope

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.

Bending insensitive optical curl cord patch cords based on Holey-fibers for FTTH

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 developed.