1. Optical fiber classification
Optical fibers can be divided into single-mode and multi-mode according to the transmission mode of light in them. The core diameter of the multimode fiber is 50 or 62.5 μm, and the outer diameter of the cladding is 125 μm, which is expressed as 50/125 μm or 62.5/125 μm. The core diameter of the single-mode fiber is 8.3 μm, and the outer diameter of the cladding is 125 μm, which is expressed as 8.3/125 μm.
The working wavelengths of optical fibers are short-wave 850nm, long-wave 1310nm and 1550nm. The fiber loss generally decreases with the increase of wavelength. The loss of 850nm is generally 2.5dB/km, the loss of 1.31μm is generally 0.35dB/km, and the loss of 1.55μm is generally 0.20dB/km, which is the lowest loss of optical fiber. The loss tends to increase for wavelengths above 1.65 μm. Due to the absorption of OHˉ (water peak), there are loss peaks in the range of 900~1300nm and 1340nm~1520nm, and these two ranges are not fully utilized.
2. Multimode fiber optic cable
Multi Mode Fiber - The core is thicker (50 or 62.5μm) and can transmit light in multiple modes. But its intermodal dispersion is large, which limits the frequency of transmitting digital signals, and it will be more serious with the increase of distance. Therefore, the distance of multimode fiber transmission is relatively short, generally only a few kilometers. The following table compares the bandwidth of multimode optical cables:
Minimum Mode Bandwidth (MHz*km)
Fiber Type Full Mode Bandwidth (LED) Laser Bandwidth (Laser)
850nm 1300nm 850nm 1300nm
OM1(62.5/125) 200 500 ffs ffs
OM2(50/125) 500 500 ffs ffs
OM3 (10G 50/125) 1500 500 2000 ffs
When it comes to 10 Gigabit multimode optical cables, it is necessary to make some explanations. Optical transceivers and optical fibers are inseparable from optical fiber systems when transmitting optical signals. Because traditional multimode fiber can only support 10 Gigabit transmission for several tens of meters, ISO/IEC 11801 has formulated a new multimode fiber standard grade, the OM3 category, and in 2002 the new optical transceiver used for 10 Gigabit applications. Officially promulgated in September. OM3 fiber is optimized for both LED and laser bandwidth modes and is subject to rigorous DMD testing and certification. The optical fiber cabling system using the new standard can support at least 10 Gigabit transmission to 300 meters in multimode mode, and can reach more than 10 kilometers in single mode mode (1550nm can support 40 kilometers transmission).
Integrated wiring
Multimode optical cables are divided into multimode solutions (62.5/125μm) and 10G multimode solutions (laser optimized 10G 50/125μm). Please refer to the following table for specific transmission indicators:
Solution Type Gigabit Transmission (m)
1 Gb/s 10 Gigabit transmission (m)
10Gb/s
OptiSPEED OM1 275 32
LazrSPEED 150 OM2 800 150
LazrSPEED 300 OM3 1000 300
LazrSPEED 550 OM3+ 1100 550
From the above table, comparing the standards, we can see that the optical cables provided by ZR Cable far exceed the indicators defined in the standards.
Therefore, if you want to choose a multimode fiber optic cable, you should consider the following points:
A. From the perspective of future development trends, the horizontal cabling network speed needs to be upgraded to 1 Gb/s bandwidth to the desktop, the main building backbone network needs to be upgraded to 10 Gb/s rate bandwidth, and the campus backbone network needs to be upgraded to 10 Gb/s or 100Gb/s rate bandwidth. At present, network applications are growing at a rate of about 50% per year. It is expected that in the next five years, gigabit to the desktop will become as common as the current 100M to the desktop. Therefore, the current system planning must be forward-looking, and the horizontal part should be considered Category 6 wiring, the backbone part should consider 10 Gigabit multimode optical cable, especially now the cost of Category 6 copper cable plus 10 Gigabit multimode optical cable and Category 5 copper cable plus Gigabit multimode optical cable is less than 10~20%. The difference between left and right, from the perspective of long-term application, if the cost allows, the use of Category 6 copper cable plus 10 Gigabit optical cable should be considered.
3. Single-mode fiber optic cable
Single-mode fiber (Single Mode Fiber): The central core is very thin (the core diameter is generally 9 or 10 μm), and only one mode of light can be transmitted. Therefore, its intermodal dispersion is very small, which is suitable for long-distance communication, but there are also material dispersion and waveguide dispersion, so the single-mode fiber has higher requirements on the spectral width and stability of the light source, that is, the spectral width should be narrow and stable. Be good.
It was later found that at a wavelength of 1310 nm, the total dispersion of a single-mode fiber is zero. From the point of view of the loss characteristics of the optical fiber, 1310nm is just a low-loss window of the optical fiber. In this way, the 1310nm wavelength region has become an ideal working window for optical fiber communication, and it is also the main working band of practical optical fiber communication systems. The main parameters of 1310nm conventional single-mode fiber are determined by the International Telecommunication Union ITU-T in the G652 recommendation, so this fiber is also called G652 fiber.
As mentioned above, due to the absorption of OHˉ (water peak), there are loss peaks in the range of 900~1300nm and 1340nm~1520nm, which is called water peak. At present, the zero-water peak single-mode optical cable provided by ZR Cable is solving this problem, eliminating the influence factors of the 1400nm water peak, thus providing users with a wider transmission bandwidth, and users can freely use all bands from 1260nm to 1620nm, Therefore, the transmission channel is increased from the previous 240 to 400, and the performance is 50% more available bandwidth than the traditional single-mode fiber, which lays a solid foundation for the CWDM coarse wavelength division multiplexing technology to be upgraded to 100G bandwidth in the future. The ideal backbone fiber system.
At the same time, since G.652.D is the latest index of single-mode fiber, it is the strictest index among all G.652 levels and is completely backward compatible. If only G.652 is indicated to mean the performance specification of G.652.A, this should be especially noted. TeraSPEED fibers meet the performance specifications of G.652.A, .B, .C and .D beyond all specifications, as shown in the following table:
G.652.A G.652.B G.652.C G.652.D TeraSPEED
attenuation
1310nm 0.5 0.4 0.4 0.4 0.35
1383nm 0.4 0.4 0.32
1550nm 0.4 0.35 0.3 0.3 0.24
1625nm 0.4 0.4 0.4 0.4
Polarization Mode Scattering PMDQ (ps/km) 0.5 0.2 0.5 0.2 0.08
Our recommendations for the selection of single-mode optical cables are as follows:
From the perspective of transmission distance, if you want to support 10 Gigabit transmission in the future, you should consider using single-mode optical cable if the distance is longer.
4. Conclusion: Single-mode or multi-mode?
Based on the above analysis, we believe that users should invest in the best performance at the lowest price from the perspective of application, transmission distance, forward-looking, and cost.
