Different Types of Fiber Optic Cable
What Is Fiber Optic Cable?
Fiber optic cable carries information using light through extremely thin strands of glass or, in some specialized applications, plastic. Unlike copper Ethernet cabling, which transports electrical signals, fiber provides an optical transmission medium capable of supporting high bandwidth across distances ranging from short data-center links to long-haul telecommunications networks.
The two fundamental families used in enterprise networking are single-mode fiber (SMF) and multimode fiber (MMF). Within these families are standardized optical-fiber categories including OS1, OS2, OM1, OM2, OM3, OM4 and OM5.
Single-Mode vs. Multimode Fiber
The most important first step when selecting fiber is determining whether the link requires single-mode or multimode optical infrastructure.
Single-Mode vs. Multimode Fiber at a Glance
| Characteristic | Single-Mode | Multimode |
|---|---|---|
| Typical Core | Approx. 9 µm | 50 µm or 62.5 µm |
| Common Categories | OS1, OS2 | OM1, OM2, OM3, OM4, OM5 |
| Typical Optical Windows | 1310 nm / 1550 nm applications are common | 850 nm applications are common |
| Typical Use | Long reach, campus, carrier and high-capacity links | Enterprise buildings and data centers |
| Reach Potential | Very long, depending on optical standard | Generally shorter than single-mode |
OS1 vs. OS2 Fiber
OS1 and OS2 are single-mode optical-fiber designations. Both are associated with the approximately 9/125 µm single-mode geometry, but their intended cabling environments and optical performance characteristics differ.
OS1 Fiber
OS1 is associated with single-mode cabling used primarily in indoor premises environments. It can be encountered in building backbones and legacy enterprise fiber installations.
OS2 Fiber
OS2 is the common choice for modern long-distance single-mode infrastructure. Its low attenuation characteristics make it well suited to campus backbones, outside-plant links, data-center interconnects and telecommunications networks.
OM1, OM2, OM3, OM4 and OM5 Fiber
Multimode fiber has evolved through multiple standardized performance categories. Modern enterprise and data-center installations most commonly encounter OM3 and OM4, while OM1 and OM2 remain important in legacy environments and OM5 supports wideband multimode applications.
| Fiber | Core / Cladding | General Positioning | Common Environment |
|---|---|---|---|
| OM1 | 62.5/125 µm | Legacy multimode | Older enterprise networks |
| OM2 | 50/125 µm | Improved legacy multimode | Existing building networks |
| OM3 | 50/125 µm | Laser-optimized multimode | Enterprise and data centers |
| OM4 | 50/125 µm | Higher-bandwidth laser-optimized multimode | Modern high-speed data centers |
| OM5 | 50/125 µm | Wideband multimode | SWDM-capable multimode systems |
OM1 Fiber
OM1 uses a 62.5 µm core and is commonly encountered in older premises networks. It was widely deployed before laser-optimized multimode fiber became common. Existing OM1 infrastructure can continue to support compatible applications, but its bandwidth-distance capabilities are more limited for modern high-speed Ethernet.
OM2 Fiber
OM2 uses a 50 µm core and offers improved bandwidth characteristics compared with OM1. It remains present in many existing enterprise installations but has largely been superseded by laser-optimized OM3 and OM4 for new high-speed network deployments.
OM3 Fiber
OM3 is a 50/125 µm laser-optimized multimode fiber designed for high-speed optical networking. It became a major data-center fiber type because it supports VCSEL-based Ethernet applications while providing substantially greater bandwidth than earlier multimode generations.
OM3 remains relevant for many 10GbE, 40GbE and 100GbE deployments when link distance and the selected optical transceivers are within the applicable Ethernet specification.
OM4 Fiber
OM4 is also 50/125 µm laser-optimized multimode fiber but provides higher modal bandwidth than OM3. This allows supported optical standards to operate over greater distances or gives network designers additional margin within high-speed multimode installations.
For modern multimode data-center infrastructure, OM4 is frequently selected when 10GbE, 25GbE, 40GbE, 100GbE or higher-speed applications must be supported within the reach limits of the chosen optics.
OM5 Fiber
OM5 is a 50/125 µm wideband multimode fiber designed to support transmission across a broader wavelength range than conventional laser-optimized multimode fiber. It can be used with shortwave wavelength-division multiplexing technologies that transmit multiple wavelengths over a fiber.
OM5 is not automatically required for every high-speed multimode network. Selection should be based on the transceiver technology, link architecture, migration plan and economic requirements of the installation.
What Does 9/125, 50/125 or 62.5/125 Mean?
Fiber dimensions are commonly expressed using the diameter of the optical core followed by the diameter of the surrounding cladding, measured in micrometers (µm).
Common Fiber Optic Wavelengths
Fiber links operate using specific optical wavelengths determined by the transceiver and networking standard. The cable and optical transceivers must be compatible with the intended application.
Commonly associated with short-reach multimode Ethernet optics.
Historically used in various multimode fiber applications.
Widely used by single-mode Ethernet and telecommunications optics.
Common in long-distance optical systems and wavelength-based transport networks.
Simplex vs. Duplex Fiber
Simplex Fiber
A simplex cable contains a single optical fiber. It can be used by applications designed to transmit over one fiber, including certain bidirectional optical systems.
Duplex Fiber
A duplex assembly contains two fibers. Many Ethernet optical links use one fiber for transmit and the other for receive, although the exact architecture depends on the optical standard.
Common Fiber Cable Constructions
Frequently used for indoor premises cabling where fibers require additional individual protection and accessibility.
Common in outside-plant and long-distance installations where environmental protection is a major consideration.
Multiple buffered fibers are contained within a common outer jacket for compact routing and structured installations.
Individual fibers receive more substantial protection, allowing them to be separated from the main cable for routing or termination.
Includes additional mechanical protection for environments where crushing, impact or other physical hazards are a concern.
High-fiber-count assemblies can provide structured connectivity between racks, distribution areas and data-center zones.
Fiber Cable Jacket and Installation Ratings
Optical performance is only part of cable selection. The cable construction and jacket must also be appropriate for the installation environment and applicable building requirements.
Which Type of Fiber Should You Use?
Fiber selection should begin with the network application rather than cable color alone. Determine the Ethernet speed, transceiver type, required distance and existing infrastructure before selecting the fiber.
| Requirement | Fiber Often Considered | Why |
|---|---|---|
| Existing Legacy Multimode | OM1 / OM2 | May already exist and support compatible applications |
| Modern Multimode Network | OM3 / OM4 | Laser-optimized for high-speed enterprise Ethernet |
| Higher Multimode Reach / Margin | OM4 | Higher modal bandwidth than OM3 |
| SWDM Application | OM5 | Designed for wideband multimode operation |
| Long-Distance / Campus | OS2 | Low-loss single-mode infrastructure |
| Long-Term High-Capacity Backbone | OS2 | Supports a broad range of long-reach optical technologies |
Fiber Type Must Match the Optical Transceiver
Selecting fiber by speed alone is not sufficient. The optical transceiver determines the required fiber type, wavelength, connector interface and supported reach.
For example, two 10GbE transceivers can use very different optical specifications: one may be designed for short-reach multimode fiber while another is designed for kilometer-scale single-mode operation. Always verify the exact transceiver specification before selecting or reusing fiber infrastructure.
Read the Fiber Transceiver Guide →Fiber Optic vs. Copper Ethernet Cable
Fiber Optic Cable
Fiber provides high bandwidth, long-distance capability and immunity to electromagnetic interference. It is commonly selected for backbone, data-center, campus and high-speed switch-to-switch connectivity.
Copper Category Cable
Twisted-pair copper remains widely used for endpoint connections, access-layer networking and applications requiring Power over Ethernet. The appropriate medium depends on distance, speed, equipment and power requirements.
Compare Category Cable Types →