The last article discussed the difference between OS1 and OS2 singlemode fiber cables. This post is for multimode. We’ll discuss the OM1 OM2 OM3 OM4 OM5 multimode fiber cables.
Due to its advantages in larger data rate and lower cost within short reach, Multimode fiber is ideal for LAN and data center applications. To achieve a 10G/40G/100G high-density cabling system, using OM2/OM3/OM4/OM5 is cost-effective. Each type has a different reach and data-rate capability. Thus, it’s necessary to understand the distinction between them to select the most appropriate type for your application.
Figure 1: OM1 OM2 OM3 OM4 OM5
What is multimode fiber?
Multimode fiber, short for MMF, can simultaneously transceive multiple modes of light rays, thanks to its large fiber core size, typically 50 or 62.5µm. It can work at 850nm wavelength using low-cost light sources like LEDs (light-emitting diodes) and VCSELs (vertical-cavity surface-emitting lasers). As a result, its relevant optics are relatively less expensive, yet its transmission distance is also limited to several hundred meters.
For more information, refer to Single-mode vs. Multimode Fiber.
Next, we’ll walk you through the five types of multimode fiber one by one.
OM1 62.5µm multimode optical fiber was developed and introduced in the 1980s. So it is already a legacy multimode fiber cable. It is coated with an orange jacket. The introduction of 62.5µm core optical fiber is to couple more signal power than 50µm optical fiber, allowing a 2km reach at 10 Mb/s to support campus applications. Though it can support 10Gb/s within 33 meters transmission distance, people often use it for 100Mb/s Ethernet applications. Today 62.5 µm OM1 multimode optical fiber is obsolete, reserved for use with extensions or repairs of legacy, low bandwidth systems.
Figure 2: Simplex OM1 fiber optic patch cable
Since OM2 fiber, all the later released multimode fiber types have a 50µm core diameter. Similar to OM1, though it can support 10Gb/s within 82 meters transmission distance, people often use it for 1Gb/s Ethernet applications.
Figure 3: 2m OM2 LC to LC duplex fiber patch cord
OM3 is laser-optimized, and OM4 and OM5 are also laser-optimized. The mainstream choice of multimode fiber is selecting from OM3, OM4, and newly released OM5 fiber.
Though OM3 supports 40Gb/s and 100Gb/s Ethernet up to 100 meters, it is mainly used for 10 Gb/s Ethernet up to 300 meters. It is coated with aqua.
Figure 4: OM3 duplex fiber optic patch cable
Like OM3, OM4 is also coated with aqua. Both OM4 and OM5 are backward compatible. VCSEL laser-optimized OM4 can support 40/100 Gb/s up to 150 meters using an MPO connector, although it is often used for 10Gb/s application within 550m.
Figure 5: Armored duplex OM4 fiber optic patch cable
OM5 fiber is wideband multimode fiber, short for WBMMF, coated with lime green. WBMMF is intended to support 4*28Gb/s channels through the 850-953 nm window, according to the ISO/IEC 11801. OM5 is designed for 40Gb/s and 100Gb/s transmission, reducing the fiber counts for high-speed communications.
Figure 6: OM5 LC-SC duplex fiber patch cord
Comparison of OM1, OM2, OM3, OM4 & OM5
The figure below illustrates the already stated difference between OM1, OM2, OM3, OM4 & OM5. Next, let’s discuss other aspects, including bandwidth, wavelength, maximum transmission capability, and distance.
|Standard||ISO 11801||ISO 11801||ISO 11801||TIA 492AAAD||TIA-492AAAE|
|Jacket Color||orange||orange||aqua||aqua||lime green|
Figure 7: Comparison of OM1, OM2, OM3, OM4 & OM5: Standard, Jacket color, Core diameter, and Light source
Bandwidth, Wavelength & transmission distance
First, let’s introduce the minimum Modal Bandwidth, short for MBW, and its two measurements: Overfilled Launch (OFL) bandwidth and effective modal bandwidth (EMB). OFL applies to the LED optical source, and EMB applies to the VCSEL laser.
OM1 and OM2 are only used with LED sources and thus are specified OFL only. In contrast, OM3, OM4, and OM5 can accommodate both LEDs and VCSELs.
|GRADE||CORE SIZE||1Gb DISTANCE||10Gb DISTANCE||40Gb DISTANCE||100Gb DISTANCE||WAVELENGTH||MAXIMUM ATTENUATION||OFL MBW||EMB MBW|
|OM1||62.5µm||300m/1,000ft||36m/118ft||not recommended||not recommended||850nm||3.5db/km||200Mhz-km||not required|
|OM2||50µm||550m/1,800ft||86m/282ft||not recommended||not recommended||850nm||3.5db/km||200Mhz-km||not required|
Figure 8: Comparison of OM1, OM2, OM3, OM4 & OM5: Distance, Wavelength, Modal Bandwidth, and Maximum attenuation.
It’s worth to mention that:
- OM3 at 40G can run up to 240m via duplex LC with 40GBASE-SWDM4 and 330m QSFP+ eSR4;
- OM4 and OM5 can run up to 350m via duplex LC with 40GBASE-SWDM4 and 550m QSFP+ eSR4.
Note: SWDM refers to Short Wavelength Division Multiplexing.
|short-haul premises cabling, like LANs, campuses.||Short-haul premises cabling, like LANs, campuses.||Short-reach, like data centers and LANs.||High-speed networks like data centers and cloud computing.||A high-speed, high-density cabling environment may require SWDM.|
OM1 and OM2 are the cheapest due to their limited transmission distance and capability of bandwidth. OM3 and OM4 are the most popular. For most SMEs, OM3 is the most cost-effective 10Gb/s Ethernet solution. It also provides future-proof potential. Compared to OM4, OM4 is relatively cheaper and suitable for 40/100 Gb/s Ethernet applications. OM5, as the newly released WBMMF, specially designed for SWDM, comes at a high cost.
OM1 and OM2 can’t support 25/40 Gb/s; thus, they almost fall into disuse. OM3 and OM4 are the mainstream choices for high-speed, high-density applications like 25/40/100 Gb/s.
OM5, compared to OM4, is designed for 40/100 Gb/s transmission and can support four SWDM channels, namely, 4*25 Gb/s Ethernet. Backward compatible with OM3 and OM4, OM5 is better than OM4 on performance. It’s fair that OM5 costs more than OM4.