function of core and cladding in optical fibre
Core ( optical fiber ) - Wikipedia Core ( optical fiber ) This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . ( July 2017 ) ( Learn how and when to remove this template message ) The structure of a typical single - mode fiber . 1 . Core 8 μm diameter 2 . Cladding 125 μm dia . 3 . Buffer 250 μm dia . 4 . Jacket 400 μm dia . Light propagating in a multi-mode fiber The core of a conventional optical fiber is a cylinder of glass or plastic that runs along the fiber 's length . The core is surrounded by a medium with a lower index of refraction , typically a cladding of a different glass , or plastic . Light travelling in the core reflects from the core - cladding boundary due to total internal reflection , as long as the angle between the light and the boundary is less than the critical angle . As a result , the fiber transmits all rays that enter the fiber with a sufficiently small angle to the fiber 's axis . The limiting angle is called the acceptance angle , and the rays that are confined by the core / cladding boundary are called guided rays . The core is characterized by its diameter or cross-sectional area . In most cases the core 's cross-section should be circular , but the diameter is more rigorously defined as the average of the diameters of the smallest circle that can be circumscribed about the core - cladding boundary , and the largest circle that can be inscribed within the core - cladding boundary . This allows for deviations from circularity due to manufacturing variation . Another commonly quoted statistic for core size is the mode field diameter . This is the diameter at which the intensity of light in the fiber falls to some specified fraction of maximum ( usually 1 / e ≈ 13.5 % ) . For single - mode fiber , the mode field diameter is larger than the physical diameter of the core , because the light penetrates slightly into the cladding as an evanescent wave . The three most common core sizes are : 9 μm diameter ( single - mode ) 50 μm diameter ( multi-mode ) 62.5 μm diameter ( multi-mode ) See also ( edit ) Buffer ( optical fiber ) References ( edit ) Jump up ^ Insulation / circuits . Lake Publishing Corporation . 1978 . Jump up ^ `` The FOA Reference For Fiber Optics - Optical Fiber '' . www.thefoa.org . Retrieved 2016 - 04 - 10 . This article related to telecommunications is a stub . You can help Wikipedia by expanding it . Retrieved from `` https://en.wikipedia.org/w/index.php?title=Core_(optical_fiber)&oldid=811212183 '' Categories : Fiber optics Telecommunications stubs Hidden categories : Articles needing additional references from July 2017 All articles needing additional references All stub articles Talk About Wikipedia فارسی Edit links This page was last edited on 20 November 2017 , at 05 : 31 ( UTC ) . About Wikipedia
1. Optical fiber core structure
2. Total internal reflection in optical fibers
3. Core and cladding in optical fibers
4. Single-mode and multi-mode fiber core sizes
5. Mode field diameter in optical fibers