Multi-mode optical fiber applied to IEEE 802.3ae 10gbit/s Ethernet

People's demand for network transmission capacity is increasing, which has promoted the further development of 10GBIT/S system. The IEEE (Institute of Electrical and Electronics Engineers) 802.3AE describes the system configuration in the local area network (LAN) and wide area network (WAN) with the 10 Gigabit Ethernet specification.

When the transmission speed of the multimode system driven by the LED (light-emitting diode) can reach 622mbit/s, the 10git/s system can make full use of the low price, the vertical resonant cavity surface laser (VCSEL) diode with 850nm working window. In order to use this Vcsel, Tesla developed a new 50/125μm multimode fiber, namely "gigaband (Billion-wave fiber)". When the standard multimode fiber with core-layer diameter is 50μm has the optimized bandwidth in 1300nm window or window between 850 and 1300nm, the new type of fiber has ideal bandwidth at the 850nm working wavelength of vcsel. The Designed optical fiber parameter can ensure the transmission distance of the system reaches 300 meters.

Bandwidth requirements

The information carrying capacity of a single multimode fiber is usually determined by its mode bandwidth. In a strictly speaking sense, the system capacity depends on the interaction of its various components, such as lasers, optical fibers, and detectors. In particular, the interaction between the VCSEL signal source and the light injected into multimode fiber can affect the effective bandwidth of the system.

The latest IEC (International Electrotechnical Commission) multimode Optical Fiber Technical Specifications iec60793-2-10 a new classification of optical fibers ala.2 made a provision. In addition to the mode bandwidth exceeding 1500 mhz.km in full injection, this kind of optical fiber also describes the "effective" (laser injection) bandwidth exceeding mhz.km in detail in the classification.

To facilitate understanding of this "effective" bandwidth definition, the requirements in the specification can be interpreted as the requirements for the optical fiber DMD (differential mode display).

6 DMD templates are defined in the specification, each of which consists of an internal mask and an external mask. The DMD mode of the optical fiber must meet one of the six templates listed in the following table.

Table 1: DMD templates for IEC 60793-2-10 ala.2 multimode fiber 50/125μm

Template number	Inner Mask (radius 5-18μm) [ps/m]	Inner Mask (radius 0-23μm) [ps/m]
1	≤0.23	≤0.70
2	≤0.24	≤0.60
3	≤0.25	≤0.50
4	≤0.26	≤0.40
5	≤0.27	≤0.35
6	≤0.33	≤0.33

Standardization Regulations

In addition to IEC 607983 on the standardization of the Ala.2 category, TIA also in the technical specifications of the TIA/EIA-492AAAC of the optical fiber has been standardized regulations. This kind of optical fiber is also referred to as OM3 type fiber in the Iec/iso indoor wiring 11801 standard.