Why new data centers don't use OM2 multimode fiber

Why don't data centers use multimode OM2 fiber anymore? Here's the answer. First of all, OM2 is mainly a traditional 50/125 micron graded refractive index multi-mode fiber. The OM2 fiber is based on LED light source in terms of standard and design, and has low bandwidth requirements. It can transmit at 1000Mbit/s or lower when combined with LED.

The OM2 will exit the data center mainly due to the maturity and commercial availability of the 850nm Vertical Cavity Surface Emission Laser (VCSEL), which immediately became the primary light source for multimode communication systems. OM2 fiber has low bandwidth and is not optimized for VCSEL lasers, so OM2 fiber will be gradually replaced by OM3 fiber.

The multi-mode OM3, OM4 and OM5 are designed based on the VCSEL laser as the light source. The design of the fiber is optimized for the wavelength of 850nm, so that the bandwidth of the fiber is optimal at 850nm. In addition, according to the characteristics of VCSEL laser mode, "effective mode bandwidth" is introduced. "Effective mode bandwidth" is used to evaluate the bandwidth of multi-mode fiber when VCSEL laser is used. OM3 fiber is standardized on "effective mode bandwidth", so as to ensure the transmission performance of fiber when VCSEL laser is used. Later OM4 fiber is on the basis of OM3 fiber continues to improve the "effective mode bandwidth" index requirements.

The OM2 has a low bandwidth and does not require the effective mode bandwidth, which cannot ensure the transmission performance of the optical fiber when the VCSEL laser is used. The transmission distance of OM2 on the 10G SFP+ SR multi-mode optical module is not ideal, which can only reach about 82 meters, while the transmission distance of OM3 multi-mode optical fiber can reach 300 meters. OM2 is not suitable for transmission at rates above 10 gigabytes.

At present, the internal connections of data centers have entered the 25G+ era, and OM2 optical fibers cannot be used for new data centers or the upgrade of existing data centers. Therefore, multi-mode OM3, OM4, and OM5 will become the popular solutions for multi-mode cabling.