Gigabit Multi
As we all know, Cable System in the transmission of light signals, can not do without optical transceivers and fiber.
Types of optical transceivers are two major categories:
LED (LED) and laser light-emitting devices (Laser). Although the performance, the laser light emitting diode devices are far superior, but because of manufacturing costs, so that has been most LAN users can not afford the high cost of laser light emitters. Until recently, a new type of vertical cavity surface emitting light emitting device device VCSELs (Verticalc
av itysurface emittinglasers) emergence to solve this problem. VCSELs absorption of laser light device performance advantages such as high response speed, transmission spectra narrow, and the advantages of LEDs such as high coupling efficiency and low cost. Therefore, low-cost high-performance VCSELs emitting devices with multi-mode fiber optic cable can transmit up to the way 10Gb / s signal.
However, another problem appeared to the user that the transmission distance. In addition to using the optical fiber transmission rate of users, but also on the transmission distance requirements. Experimental results show that the traditional multi-mode fiber optic cable, whether it is 50 m or 62.5 m, although to support 10Gb / s network transfer, but the support distances of 100 meters, which is simply the application of the network backbone can not be met.
Multimode fiber transmission bottleneck?? DMD Why 100Mbps can support the 2000 meters of multimode fiber, 1Gbps can only support the 550 meters? The main reason is precisely because the phenomenon of multi-mode fiber DMD. After
Test , We find that multi-mode fiber in the transmission of light pulses, optical pulse in the transmission process is unstable broadening, when such divergence has seriously to a certain extent, superimposed with each other between before and after the pulse, making the receiving end could not accurately distinguish each a light pulse signal, a phenomenon we call DMD (DifferentialModeDelay). The main reasons is that multi-mode fiber with a light pulse contains more than one modal component, from the optical point of view, each modal component in the fiber transmission paths of different, for example, along the central line optical fiber transmission light weight, and transmission through the fiber cladding reflected light component has a different path. From the electromagnetic point of view, the multi-mode fiber diameter in the three-dimensional space that contains a lot of modes (300-1100) component, the composition is very complicated.
When we use light-emitting devices such as LED, the surface light emission LED light filled the whole fiber (which we refer overfilled model). Uniform distribution of light energy in all components of the mode. As different path component arrival time of light transmission are different, and therefore pulse will gradually widen. However, uniform distribution of energy, each component of a light pulse of the whole rather small, technically, we called this kind of bandwidth, OverfilledLaunchBandwidth (OFB); when we replace the LED Laser, the situation will become different, the laser contains only very few modal components, which carry the energy of each optical component is very concentrated, so each optical component instead of the light pulse will have a major impact. Give an extreme example, if there is only two modal components, they arrive at different times, which will lead to a serious divergence of the light pulse.
Itself as the performance of LED light-emitting device limitations, in more than 1Gbps high-speed applications, the light-emitting devices are light-emitting devices using laser, multimode fiber from the traditional standards and design methods are LED-based, so , due to two different light-emitting device transmission, optical fiber itself must be modified to adapt to light changes. Therefore, ISO/IEC11801 proceed to develop a new standard grade multimode fiber, or OM3 category, and was formally promulgated in September 2002. The Avaya Inc. SYSTIMAXSCS structured cabling systems, has launched the first international standards for my company OM3 multi-mode fiber-LazerSPEED solution, the potential for the current 10Gb / s networking applications.
ISO standards on the re-classification of multi-mode optical fiber, OM1 refers to the current traditional 62.5 m multimode fiber, OM2 refers to the current traditional 50 m multimode fiber, OM3 is a new Gigabit fiber. Note that two modes of fiber-optic bandwidth of indicators, OverfilledLaunchBandwidth is matched against the LED indicator light-emitting devices, and LaserBandwidth a new laser light devices for matching targets. OM3 fiber while two modes are optimized. Another to note is that the choice of transmission wavelength, 850nm or 1300nm. Although the longer the wavelength, the better the performance, but the cost of light-emitting devices will be doubled, therefore, the user, if possible, try to select the short wavelength applications to reduce costs. For example, the new VCSELs is to short wavelength light-emitting devices for the application environment, while the Standard Laser is mainly used for long-wavelength light-emitting device environment.
OM3 fiber testing problem DMD test of the main steps are: 5 m using a single-mode fiber optic probe connected OM3 measured by single-mode fiber-optic probe continuously measured pulse occurs at the same time, the probe scanning
Mobile From the optical axis to the edge of mobile, moving around each 1 m. On the receiving end, each position pulse will be recorded and superimposed on the map with a time domain to form DMD indicators. To reach the path of light pulses generated due to different time difference, and because light pulse itself is unstable, the sum of these two differences, according to standard than to determine whether to meet the standards of OM3 fiber.
Because the test requires very sophisticated equipment, and testing methods. Users can now be tested in the field, only by specialized laboratory testing, Avaya SYSTIMAX Labs is the company a few can be one of the test.
OM3 fiber performance advantages Network applications as users upgrade facing pressure from the current 1Gb / s, to the future 10Gb / s, how to present the application and implementation for the future smooth upgrade over, that every user needs careful consideration.
In the current 1Gb / s network era, the traditional multi-mode fiber to support a distance not more than 550 meters, while the mean for the same time using single-mode fiber laser emitting device using expensive, although the wiring system, the two cost is almost the same, but the network device, at least two options mean that double the price difference. In many cases, when the user’s transmission distance over 500 meters, 1000 meters but when they had to use
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