OM3 and OM4 are two common
types multimode fiber used in local area networks, typically in backbone
cabling between telecommunications rooms and in the data center between main
networking and storage area network (SAN) switches. Both of these fiber types
are considered laser-optimized 50/125 multimode fiber, meaning they both have a
50μm micron diameter core and a 125μm diameter cladding, which is a special
coating that prevents light from escaping the core. Both fiber types use the
same connectors, the same termination and the same transceivers—vertical-cavity
surface emitting lasers (VCSELs) that emit infrared light a 850
nanometers(nm). OM3 is
fully compatible with OM4. With so many similarities, and often manufactured
with the same color aqua cable jacket and connectors, it can be difficult to
tell these two fiber types apart. So, what’s the difference between OM3 vs OM4?
Do these two types fiber refer to the same thing?
In fact, the
difference between OM3 vs OM4 fiber is just in the construction of the fiber optic
cable. The difference in the construction means that OM4 cable has
better attenuation and can operate at higher bandwidth than OM3.
What is the reason of this? For a fiber link to work,
the light from the VCSEL transceiver much have enough power to reach the receiver at
the other end. There are two performance values that can prevent this—optical
attenuation and modal dispersion.
the performance difference in OM3 vs OM4 is in the loss (dB) in the cable. OM4 fiber causes lower losses due to its
construction.The maximum attenuation allowed by the standards is shown below.
You can see that using OM4 will give you lower losses per meter of cable.
Name |
100MB |
1000BASE_SX |
10GBASE_S |
40GBASE_SR4 |
100GBASE_SR10 |
OM1 |
2000m |
275m |
33m |
Not Specified |
Not Specified |
OM2 |
2000m |
550m |
82m |
Not Specified |
Not Specified |
OM3 |
2000m |
550m |
300m |
100m |
100m |
OM4 |
2000m |
1000m |
550m |
150m |
150m |
Since the attenuation of OM4
is lower than OM3 fiber and the modal bandwidth of OM4 is higher than OM3, the transmission distance of OM4 is longer than OM3. NBG company has started producing OM4 cables, patchcords and pigtails with customised length and connectors.