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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.

Transmission characteristics of fiber Bragg gratings (FBGs) written in holey fibers with different air-hole size are investigated. The cladding mode coupling of FBGs inscribed on holey fibers is remarkably suppressed due to air holes inside of the silica cladding. The wavelength spacing between the main peak due to the core mode coupling and side peak due to the first-order cladding mode coupling increases as the air-hole size increases because the reduction of the effective index of cladding mode depends on the air-hole size within the fiber. The strain and temperature sensitivities of FBGs are also investigated corresponding to air-hole size of holey fibers. The temperature sensitivities of holey-fiber-based FBGs are similar regardless of air-hole size of holey fibers (~1.9%), but their strain sensitivities are enhanced (~28.4%) as the air-hole size increases

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.

We discuss bending properties of a long-period fiber grating (LPFG) inscribed into a holey fiber (HF) depending on an axial rotation angle. High quality of the HF-based LPFG with a high extinction ratio of more than 20 dB is achieved. The proposed HF-based LPFG has bending insensitivity under a certain range of the bending curvature. As the bending curvature is higher than 4 m(-1), the center wavelength of the grating is shifted into the shorter wavelength. Bending sensitivity of the HF-based LPFG is changed by an axial rotation angle, which shows its dependence on the rotational orientation. We measure the transmission characteristics of the HF-based LPFG with the ambient index change. The HF-based LPFG has ambient index insensitivity because of the air holes in the inner cladding.

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.

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.

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.

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 developed.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We propose and experimentally demonstrate a simple and flexible scheme for the simultaneous measurement of strain and temperature using long-period fiber gratings (LPFGs) based on versatile holey fibers (HFs) with different air-hole sizes. The strongly resonant LPFGs (as much as approximately 24 dB) can be successfully achieved. The LPFGs inscribed in the HFs have similar temperature sensitivities regardless of air-hole size because of the same material composition. The strain sensitivities of the LPFGs, however, are different, since holey fibers have different cross-sectional areas depending on the air-hole size. The strain sensitivities of the HF-based LPFGs are enhanced by a factor larger than 2 as the air-hole size increases.

We propose and experimentally demonstrate a simple and flexible scheme for simultaneous measurement of strain and temperature based on long-period fiber gratings inscribed in versatile holey fibers with various air-hole sizes.

We discuss bending properties of long-period fiber grating (LPFG) inscribed into a holey Fiber depending on an axial rotation angle and achieve a bending-insensitive LPFG under a certain range of bending curvature (

We experimentally demonstrate a 320 Gbit/s (32Chs times 10 Gibt/s) WDM signal transmission of bending insensitive holey fibers of less than 0.04 dB. Error free operation is achieved for all 32 channels.

We propose a novel fabrication method of holey fibers with different size, pitch, and shape of air holes. By expanding a Ge-doped preform with air holes at high temperature, the size and shape of air holes can be readily modified.

We propose a simple technique for simultaneous measurement of stain and temperature based on fiber Bragg gratings written in holey fibers with different air hole in one-layered air holes within the silica cladding.

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.

We discuss effect of air hole size on transmission characteristics of fiber Bragg gratings written in holey fiber. The strain and temperature sensitivities of grating strongly depend on the air hole size of holey fibers.

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.