光纤传播模式 Input pulse one oels (a) Step-index multimode ngo ba红mx Input pulse tib o goners odt bongos n(b) Graded-index multimode U arl n 多 Output pulse N (e)Single modeisedt rpoe i x(3 b oni Figure 4.4 Optical Fiber Transmission Modes A
网络通信 11 光纤传播模式
Description o Step-Index Multimode Light from a source enters the cylindrical glass or plastic core Rays at shallow (pii) angles are absorbed by the surrounding material. This form of propagation is called step-index multimode (多模突变) referring to the variety of angles that will reflect With multimode transmission, multiple propagation paths exist each with a different path length and hence time to traverse (f if) the fiber. This causes signal elements(light pulses) to spread out in time, which limits the rate at which data can be accurately received. Put another way(另一方面), the need to leave spacing between the pulses limits data rate. This type of fiber is best radius is reduced, fewer angles will reflect. By reducing the radius of the core to the order of a wavelength, only a single angle or mode can pass: the axial ray 网络通信 12
网络通信 12 Description Step-Index Multimode ◼ Light from a source enters the cylindrical glass or plastic core. Rays at shallow（平缓）angles are absorbed by the surrounding material. This form of propagation is called step-index multimode, （多模突变）referring to the variety of angles that will reflect. With multimode transmission, multiple propagation paths exist, each with a different path length and hence time to traverse（穿 过）the fiber. This causes signal elements (light pulses) to spread out in time, which limits the rate at which data can be accurately received. Put another way（另一方面）, the need to leave spacing between the pulses limits data rate. This type of fiber is best suited for transmission over short distances. When the fiber core radius is reduced, fewer angles will reflect. By reducing the radius of the core to the order of a wavelength, only a single angle or mode can pass: the axial ray