How to Choose Single-mode and Multimode Optical Fibers in Integrated Cabling Design

Optical fibers can be divided into single-mode and multi-mode according to the transmission mode of light in media. Correspondingly, users should invest in the best performance at the lowest price from the perspective of application, transmission distance, forward-looking and cost.



1. Optical Fiber Classification

Optical fibers can be divided into single-mode and multi-mode according to their transmission modes. The core diameter of multimode optical fibers is 50 or 62.5 micron, and the outer diameter of cladding is 125 micron, representing 50/125 micron or 62.5/125 micron. The core diameter of single-mode fiber is 8.3 micron and the outer diameter of cladding is 125 micron, representing 8.3/125 micron.

The working wavelengths of optical fibers are 850 nm in short wave, 1310 nm in long wave and 1550 nm in long wave. The loss of optical fibers generally decreases with the increase of wavelength. The loss of 850 nm is 2.5 dB/km, the loss of 1.31 um is 0.35 dB/km, and the loss of 1.55 um is 0.20 dB/km. This is the lowest loss of optical fibers. The loss of wavelength over 1.65 um tends to increase. Due to the absorption of OH-(peak), there are loss peaks in the range of 900-1300 nm and 1340-1520 nm, which are not fully utilized.

2. Multimode Optical Fiber

MultiMode Fiber - The core is thick (50 or 62.5 um), and it can transmit light of various modes. However, its inter-mode dispersion is large, which limits the frequency of digital signal transmission, and will become more serious with the increase of distance. Therefore, the distance of multimode optical fiber transmission is relatively close, usually only a few kilometers.

When it comes to 10,000-mega multi-mode optical cable, some explanation is needed. Optical transceivers and optical fibers are indispensable to the transmission of optical signals in optical fiber systems. Because traditional multimode optical fibers can only support tens of meters of 10,000 Mega transmission, ISO/IEC11801 has formulated a new standard class of multimode optical fibers, namely OM3, in order to meet the needs of 10,000 Mega applications, which was officially promulgated in September 2002. OM3 optical fiber optimizes both bandwidth modes of LED and laser, and requires strict DMD testing and certification. The new standard optical fiber cabling system can support at least 10,000 Mega transmission to 300 meters in multi-mode mode mode mode, and more than 10 kilometers in single mode mode mode mode mode mode mode mode mode (1550 nm can support 40 kilometers transmission).

Compaq's multimode optical cables are divided into multimode Opti SPEED solutions (62.5/125 micron) and multimode Lazr SPEED solutions (50/125 micron laser optimization). LazrSPEED is divided into three series, namely LazrSPEED 150, 300, 550 series, and LazrSPEED 10,000 Mega multi-mode optical cables are all certified by ULDMD.

If we want to choose multimode optical cable, we should consider the following points:

A. In terms of future development trend, the horizontal wiring network rate needs 1 Gb/s bandwidth to the desktop, the building backbone network needs to upgrade to 10 Gb/s bandwidth, and the campus backbone network needs to upgrade to 10 Gb/s or 100 Gb/s bandwidth. At present, network applications are growing at an annual rate of about 50%. It is expected that gigabit-to-desktop will become as common as current 100-to-desktop applications in the next five years. Therefore, it is necessary to have a certain foresight in current system planning. Six types of cabling should be considered in the horizontal part, and 10,000-megabit multi-mode optical cables should be considered in the main cadres, especially in the current six types of copper. There is only about 10-20% difference in the cost of cable plus 10,000-mega multi-mode cable and super-5 kinds of copper cable plus 10,000-mega multi-mode cable. From the perspective of long-term application, if the cost permits, 6 kinds of copper cable plus 10,000-mega optical cable should be considered.

B. From the investment point of view, OptiSPEED (ordinary multi-mode 62.5/125) is chosen where 10G will not be used in at least 10 years. Owing to the use of low-cost VCSEL and 850-nm light source equipment for OM3 optical cable, the cost of 10,000-mega transmission is greatly reduced.