July 30, 2009
Furukawa Electric is actively engaged in the research and development of microstructured optical fibers (Note 1), as the next-generation optical transmission fibers that can cope with the ever-increasing information and communications traffic. Having embarked on full-fledged research and development in 2007, we have produced remarkable R&D achievements including: in March 2009, for the first time in the world, we succeeded in developing multi-core holey fiber (Note 2) that is a kind of microstructured fiber capable of realizing a transmission capacity almost one hundred times that of conventional optical fiber, and we made a presentation at the Optical Fiber Communication Conference and Exposition, the world's largest academic conference in the optical communications field; and at the Optoelectronics and Communications Conference held in Hong Kong this July, we made a presentation under the title of “The study on loss reduction of Holey Fiber by viscosity profile control,” which is a manufacturing technology aimed at quality improvement.
Hereafter, we intend to build up verification experiments on long-distance transmission, as well as to make quality improvements in transmission loss and the like, aiming at putting this technology into practical use in ten years.
Developmental Background
Cross-section of multi-core holey fiber
Since its practical application began nearly 30 years ago, optical communication has become to be widely used in our daily lives. Optical fiber, which constitutes the underlying infrastructure of optical communication, has now expanded its application to the transoceanic, long haul, metro, access and premises. Especially the number of domestic FTTH (Fiber To The Home) subscribers continues to increase.
The amount of information that is necessary in each home is expected to increase as the service such as the delivery of high-definition videos. In order to achieve ultra-large capacity transmission for such a new information era, Furukawa Electric is pursuing the developmental of innovative optical fiber technologies.
Product Features and Specifications
One of our targets is holey fiber (Note 4), a type of microstructured fiber, characterized by having “holes” in its cladding. Due to this holey structure, the fiber realizes the “Endlessly Single Mode (ESM)” characteristics (Note 5) that is unattainable with conventional core-cladding structured optical fiber (Note 3). Whereas the wavelengths for long-distance transmission have been limited conventionally from 1300 to 1600 nm, the ESM characteristics enable the use of shorter wavelength (e.g., 1 µm), thereby expanding the transmission capacity by using wavelength multiplexing. Moreover, based on the holey fiber technology, Furukawa Electric has succeeded in achieving, for the first time in the world, “multi-core holey fiber” that has seven cores within an optical fiber.
When multiple cores are provided in a single fiber, optical signals within the fiber usually interfere with each other, resulting in the degradation of optical signals during long-distance transmission. We have optimized the structure design of the holey fiber, making it theoretically possible, for each core of the 180-µm diameter fiber which is almost equivalent to the conventional size, to transmit optical signals with ultra-large bandwidth over a distance of more than 100 km. Verification experiments on long-distance transmission are scheduled, so as to put this technology into practical use. Thus, a single fiber of this type can realize an ultra-large transmission capacity that is almost one hundred times that of conventional fibers, being capable of coping with the growing information and communication traffic in the future. Moreover, since large-capacity transmission can be realized using a small number of fibers,materials necessary to manufacture fibers and cables can be reduced., thereby making a contribution to resource saving.
Development of Manufacturing Technology
For practical application of holey fibers, not only structural design to realize novel characteristics but also processing is key technology. Furukawa Electric is developing the processing technology jointly with OFS, an affiliate company in the U.S., taking advantage of its manufacturing processing technology. The loss reduction technology by material viscosity adjustment is one of our achievements. We intend to develop manufacturing technologies further, aimed at quality improvement.
Glossary
Optical fibers generally have a double-layered structure for light transmission consisting of core and cladding, whereby the refractive index of the core is higher than that of the cladding so as to confine light, working as a light waveguide.
(Note 1)Microstructured optical fiber:
This fiber has holes in the cladding or core-cladding.
(Note 2) Multi-core holey fiber:
This fiber has multiple cores in a single optical fiber based on the holey fiber technology.Back to Main Content
(Note 3) Conventional optical fiber:
This fiber has core and cladding made of solid silica, sometimes called “solid type” fiber in contrast to “holey” fiber.Back to Main Content
(Note 4) Holey fiber (HF):
A kind of microstructured optical fiber, also termed as “photonic-crystal fiber (PCF),” . The periodic configuration of holes realizes a light waveguide structure.Back to Main Content
(Note 5) Endlessly Single Mode (ESM):
Common optical fibers have a wavelength limitation on the single mode that is suitable for long-distance optical transmission. Generally, the lower limit capable of single-mode transmission corresponds to cutoff wavelength. When a cutoff wavelength does not exist allowing for single-mode transmission at any wavelength, this situation is called “Endlessly Single Mode (ESM).”Back to Main Content