The 50/125μm and 62.5/125μm multimode fibers are the common fiber types in optical transmission networks, in which 50μm and 62.5μm represent the diameter of the core used to transmit optical signals in the optical fiber, while 125μm represents the diameter of the cladding, which can protect the core and limit the propagation of light within the core. Although the cladding size of these two multimode fibers is the same, the different core diameter makes their bandwidth different. So, can these two kinds of multimode fiber be mixed? What is the impact of mixing on the transmission performance of optical fiber?
According to ISO 11801 standard, multimode fiber can be divided into OM1, OM2, OM3, OM4 and OM5. The core diameter of om1 multimode fiber is 62.5μm, and the core diameter of the remaining four multimode fibers is 50μm. These five types of multimode fibers are different in transmission rate, transmission distance and sheath color. The smaller the core diameter, the higher the transmission rate and the longer the transmission distance.
Why mix multimode fiber?
The 62.5μm multimode fiber is usually used in 10/100Mbps Ethernet with light emitting diode (LED) as light source. With the continuous upgrading of network speed, multi-mode optical fiber with LED as light source has been far from meeting the transmission requirements of high-speed network. Therefore, a 50μm multimode fiber with vertical cavity surface emitting laser (VCSEL) as the light source has emerged. Compared with LED light source, 50μm multimode fiber with VCSEL as light source has higher power and higher quality laser output. Therefore, 50μm multimode fiber is used more and more widely. Although many large-scale networks (such as data centers) are installed with 50μm multimode fiber, there are still many applications that need to use 62.5μm multimode fiber. Therefore, the demand for mixing 50μm and 62.5μm multimode fiber is also increasing.
What are the problems with hybrid multimode fiber?
There are two cases of hybrid multimode fiber. One is that light enters from 62.5/125μm multimode fiber to 50/125μm multimode fiber. The 50/125μm multimode fiber has a small core diameter and can be easily coupled with 62.5/125μm multimode fiber. In this case, the offset and coupling angle difference will not have a great impact on the transmission of the fiber.
The other is that light enters from 50/125μm multimode fiber to 62.5/125μm multimode fiber. When the 62.5/125μm multimode fiber is mixed with 50/125μm multimode fiber, due to the larger core diameter of the former, the light in 62.5/125μm multimode fiber will disperse from the core into the cladding of 50/125μm multimode fiber, resulting in a part of loss. If the fiber loss is large, it is not recommended to mix 62.5/125μm and 50/125μm multimode fiber.
Although the laser light sources of 50μm and 62.5 μm multimode fibers are different, they are fully compatible, but it is recommended that you do not mix different types of fibers in a single link. If the loss is within your acceptable range, you can mix 50 μm and 62.5 μm multimode fibers as appropriate.
Not only the compatibility of 62.5 μm and 50 μm multimode fibers is important, but also the compatibility of multimode fibers with different bandwidth or from different suppliers needs to be paid attention to.
