In fiber optics, a graded index is an optical fiber whose core has a refractive index that decreases with increasing radial distance from the optical axis of the fiber.
Because parts of the core closer to the fiber axis have a higher refractive index than the parts near the cladding, light rays follow sinusoidal paths down the fiber. The most common refractive index profile for a graded-index fiber is very nearly parabolic. The parabolic profile results in continual refocusing of the rays in the core, and minimizes modal dispersion.
Multi-mode optical fiber can be built with either graded index or step index. The advantage of the multi-mode graded index compared to the multi-mode step index is the considerable decrease in modal dispersion. Modal dispersion can be further decreased by selecting a smaller core size (less than 5-10μm) and forming a single mode step index fiber.[1]
This type of fiber is normalized by the International Telecommunications Union ITU-T at recommendation G.651.1.[2]
History[]
Japanese engineer Jun-ichi Nishizawa invented the graded-index optical fiber as a channel for transmitting light from semiconductor lasers.[3][4] He patented the graded-index optical fiber in 1964.[5]
The graded-index optical fiber is one of the three essential elements of optical communication, as the transmission line, along with the semiconductor laser as the light source and the PIN photodiode as the optical receiver, both also invented by Nishizawa, in 1957 and 1950, respectively. In turn, optical communication provided the basis for internet technology, laying the foundations for the Digital Revolution and Information Age.[5]
References[]
- ↑ A Reference Guide to Optical Fibers and Light Guides, archived from the original on 2015-07-22, retrieved 2015-04-22
{{citation}}: Unknown parameter|dead-url=ignored (|url-status=suggested) (help) - ↑ Characteristics of a 50/125 µm multimode graded index optical fibre cable for the optical access network, retrieved 2012-11-23
- ↑ "Optical Fiber". Sendai New. Archived from the original on September 29, 2009. Retrieved April 5, 2009.
{{cite web}}: Unknown parameter|deadurl=ignored (|url-status=suggested) (help) - ↑ "New Medal Honors Japanese Microelectrics Industry Leader". Institute of Electrical and Electronics Engineers.
- ↑ 5.0 5.1 The Third Industrial Revolution Occurred in Sendai, Soh-VEHE International Patent Office, Japan Patent Attorneys Association