OM1, OM2, OM3 in multimode fiber


When we usually design multi-mode optical cables, everyone will see words such as OM1, OM2 or OM3. Many people do not know what these represent. Below is a brief description of the differences between them.


Before telling the difference, let's make up some noun explanations:

850nm: Indicates the 0.85μm band with the smallest optical fiber transmission loss;

1300nm: Indicates that the optical fiber transmits a 1.30μm band smaller than 850nm;

62.5/125μm: indicates that the outer diameter of the optical core is 62.5μm, and the outer diameter after adding the cladding is 125μm;

50/125μm: indicates that the outer diameter of the optical core is 50μm, and the outer diameter after adding the cladding is 125μm;


In fact, in the new multimode optical fiber standard promulgated by ISO/IEC 11801, multimode optical fiber is divided into three grades: OM1, OM2, and OM3. We generally call the traditional 62.5/125μm OM1 grade multimode optical fiber cable, and 50/125μm is called the OM1 grade multimode optical fiber cable. It is an OM2 grade multimode optical cable, and OM3 refers to a multimode optical fiber with 10 Gigabit transmission.

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Multimode fiber

Then let's talk about the difference between them:

OM1 grade multimode fiber is a multimode fiber with a specification of 62.5/125μm. At the rate of a gigabit system, the 850μm band can transmit 300m, and the 1300μm band can transmit 550m, and its bandwidth is 200/500MHZ*km @850/1300nm.


OM2 grade multimode fiber mostly refers to the multimode fiber with 50/125μm specification. Since the outer diameter of the optical core and the outer diameter of the cladding are relatively small, its bandwidth is larger than that of the OM1 optical fiber, and its bandwidth is 500/500MHZ *km @850/1300nm, especially after the emergence of low-cost vcsel light sources at 850nm, 50/125μm fiber has a higher bandwidth at 850nm and can transmit a longer distance, so it is very suitable for the current mainstream 1gb/s system middle.


Since OM1 and OM2 are based on LED light source in the early standard and design, there are certain compatibility problems with the current mainstream high-speed network light source vcsel, which cannot exert the real bandwidth of vcsel, so it needs to be transformed. In order to meet the higher transmission speed of 10gb/s, the International Organization for Standardization ISO, the International Electrotechnical Commission IEC, and the American Telecommunications Industry Alliance ITA-TR42 have jointly drafted a new multi-mode optical fiber standard, which is divided into OM3 grades. .


After reading the above content, I believe that everyone has some understanding of multimode fiber. In the subsequent integrated wiring design, we can choose the multimode fiber of the level we need according to the actual situation. In addition, I would like to remind you that when choosing multimode fibers of different grades, you should also choose pigtails and jumpers of the same grade.


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