What do optical fiber OS1 OS2 OM1 OM2 OM3 and OM4 mean?

Optical fiber is a medium used for transmitting optical signals. The terms OS1 OS2 OM1 OM2 OM3 and OM4 are internationally recognized classification standards for optical fibers mainly used to distinguish the performance characteristics and application scenarios of different types of optical fibers. According to the differences in their transmission modes they can be divided into two major categories: SingleMode Fiberand Multimode Fiber.

1.Single-mode optical fiber:

The singlemode optical fiber mainly used for long-distance and high-bandwidth transmission.

OS1:

The OS1 is traditional single-mode optical fiber. Comply with the ITU-T G.652A/B standard. It is suitable for backbone networks with short transmission distances (such as the access layer of metropolitan area networks) or low requirements and is usually used in Ethernet and broadband services. Its attenuation (signal loss) index is relatively lenient. However with the advancement of technology OS1 optical fibers have gradually been replaced by more advanced standards.

OS2:

The OS2 is called zero water peak single-mode fiber or low water peak single-mode fiber. Compared with OS1 OS2 optical fiber overcomes the influence of the water peak at 1383nm. The water absorption peak near the 1383nm wavelength is significantly reduced or eliminated thereby opening up a wider available wavelength range (1280nm to 1625nm) and expanding its applicable bands to four including the O band E band S band and C band. It is particularly suitable for wavelength division multiplexing technology. The OS2 single-mode optical fiber can be better applied to the next-generation 40G and 100G standards. This is currently the most commonly used single-mode optical fiber type in newly built networks. Its performance is superior to OS1 supporting longer distances and higher rates.

2. Multimode optical fiber:

The Multimode  fiber mainly used for short-distance and high-bandwidth transmission it is commonly found in scenarios such as data centers and inside buildings. The cost is usually lower than that of single-mode optical fiber but the transmission distance is limited.

OM1

The OM1 is a standard for multimode optical fibers which is mainly used for short-distance data transmission. Due to its large core diameter OM1 optical fiber can support multiple mode transmissions and thus is called multimode optical fiber. In the early Ethernet and broadband services OM1 optical fibers were widely used.

OM2

 The OM2standard is a multimode fiber developed on the basis of OM1. Compared with OM1 OM2 optical fibers have a smaller core diameter and can support more mode transmissions. In addition OM2 optical fibers also feature higher bandwidth and lower attenuation performance making them more efficient in long-distance data transmission.

OM3

The OM3 standard is a multimode fiber developed on the basis of OM2. Compared with OM2 OM3 optical fibers have higher bandwidth and lower attenuation performance with a significant increase in bandwidth (typically 2000 MHZ km@850 nm that is 2000 MHZ km). It can effectively support a 10G Ethernet transmission distance of up to 300 meters making it more efficient in long-distance data transmission. In addition OM3 optical fibers also adopt a new refractive index distribution technology further enhancing the transmission performance. It is one of the mainstream choices for current data centers and high-speed networks.

OM4

The OM4 standard is an enhanced laser-optimized 50/125μm multimode fiber developed on the basis of OM3. It is usually water blue/violet outer skin (violet is also used to distinguish it from OM3). Further optimized on the basis of OM3 it provides a higher bandwidth (typically 4700 MHz* k@850 nm). It supports 10G Ethernet with a transmission distance of up to 550 meters and better supports 40G and 100G Ethernet (with MPO connectors the transmission distance can reach 100-150 meters). In addition OM4 optical fibers also adopt a new refractive index distribution technology and a smaller core diameter further enhancing their transmission performance. It is the first choice for data centers that require higher performance.

OM5

(By the way) Wide-wave multimode fiber. It is usually a lime green skin. Designed to support a wider wavelength range (850nm to 950nm) it is particularly optimized for short-wave wavelength division multiplexing technology to transmit multiple signals over a single optical fiber and is mainly used in future higher-capacity data centers (such as supporting 100G/400G SWDM4 applications).

Summarize the key differences:

Selection Guide

For long-distance transmission (> several hundred meters) or ultra-high bandwidth: Choose single-mode optical fiber (OS2).

For short distances (such as between data center cabinets and within buildings): Choose multimode optical fibers.

Sensitive to existing low-speed equipment or cost: OM1/OM2 (but gradually phased out, new construction is not recommended).

Mainstream 10G applications with high cost performance: OM3.

For a longer 10G distance or to prepare for the deployment of 40G/100G: OM4.

Future-oriented SWDM applications: OM5

To sum up

Simply put, OS is single-mode and OM is multi-mode. The larger the number, the better the performance, the higher the supported rate or the longer the distance usually. Now, when creating a new high-speed network, OS2 is the preferred choice for single-mode and OM3 or OM4 for multi-mode.