At Tsukuba forum ended on October 16, in Japan, NTT Research labs had displayed the latest developments from Photonic crystal fiber concepts abbreviated to PCF which is considered to be the future development in the fiber optic communication medium. Photonic-crystal fibers have been in the laboratory for more than one decade with the name Photonic crystal fiber given by Philip Russell in his unpublished work in 1991.
Some of the other names given to the concept like Photon crystal fiber are Microstructured fiber, Photonic bandgap fiber, holey fiber, hole assisted fiber, and Bragg fiber.
Following the mechanism of light confinement, Photonic crystal fibers can be divided into two modes of operation. One with a solid core part, or a core with a higher refractive index than the microstructured cladding, that follows conventional optical fibers in index-guiding properties. Another method to confine the light by a microstructured cladding that creates a photonic bandgap, either a lower refractive index core or a hollow air core. Fiberkids are also not able to comment much on the theoretical aspects of these new concepts, but we want to share what we learned from the Tsukuba forum and technical seminar.
NTT research centers are studying this relatively new candidate in optical waveguides for the future large capacity transmission lines. Photon crystal fibers have novel light-guiding properties including ultra wide single mode wavelength operation and very low bending loss, which is unobtainable in conventional optical fibers.
We could count 94 holes in the cladding region though it was a funny job to count. There was a preform of PCF displayed which is magnified through a microscope. Visitors can view the structure of the cladding with cylindrical air holes in the hexagonal shape. But we could not measure the diameter of the air holes!
NTT has succeeded in developing Photon crystal fibers having 0.29dB/km attenuation at 1310nm wavelength transmission. A conventional single mode fiber will have 0.33 dB/km attenuation at 1310nm. The attenuation at 1550nm is typically 0.18dB/km. Obtaining this value for conventional single mode fiber is difficult. The Rayleigh scattering coefficient of Photonic Crystal fiber is 0.72 dB/(km.um4).
The use of the ultra wide band and large capacity transmission was demonstrated through Photonic crystal fibers. Through PCF, 640Gbps WDM transmission at 1550 nm wavelength region is possible, with the low loss being an added advantage. NTT also claims to have achieved the first penalty-free dispersion managed optical solution transmission over 100km long low loss Photonic crystal fiber.
160Gbit/second high speed optical signal transmission over an optical link of 26 kilometers has been successfully achieved through photonic crystal fiber developed by NTT. Now the research centers are studying the use of the 1000nm wavelength region of light as a new communication band considering the future demand for ultra large capacity transmission systems. YDFA will be used as amplifiers in such transmission systems.
There is a video about Photonic Crystal Fiber on the website of NTT Science and Core Technology Laboratory Group Visual Library;
As the research centers are gearing up to develop and come up with new practically possible communication medium alternatives to conventional single mode fiber, there will definitely be a positive evolution in the fiber optic communication to meet the high bit rate transmission of the future.
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