What Is Single Mode Fiber?

Single mode fiber (SMF) is a type of fiber optic cable that only allows one light mode to transmit at a time. Generally, single mode cable has a narrow core diameter of 8 to 10µm (micrometers), which can propagate at the wavelength of 1310nm and 1550nm.

Modes of light can only propagate through single mode fiber optic cables due to their small core diameters. As a result, the amount of light reflection that occurs as light passes through the core is reduced, reducing attenuation and allowing the signal to propagate further.

Signals such as Cable TV, Internet, and telephone are generally carried by single mode fibers, which are wrapped together into a huge bundle. Single mode fiber is used over long distances, however, at high transmission speeds, the cable and equipment used for single mode fiber are more expensive compared to multimode fiber (MMF).

Single Mode Fiber Types: OS1 vs OS2

As we all know, multimode fiber is usually divided into OM1, OM2, OM3, OM4 and OM5 fiber types. When it comes to single mode fiber types, it can be categorized into OS1 and OS2 fiber, which are SMF fiber specifications.

OS1 fiber is mainly used in the construction of indoor applications, such as campus networks and building networks, where the maximum distance is 10 km. OS2 fiber is more suitable for outdoor applications including backhaul networks, external plants, FTTH, WDM/DWDM network, etc., where the maximum distance is up to 200 km.

OS1 vs OS2: What are Their Differences?

It’s of great significance to figure out the difference between OS1 and OS2 when conducting deployments. The specification table below will present the differences between them clearly.

Standards ITU-T G.652A/B/C/D ITU-T G.652C/G.657.A1 (part)
Cable Construction Tight Buffer Loose Tube
Application Indoor Outdoor
Attenuation 1.0db/km 0.4db/km
Max. Distance 10 km 200 km
Price Low High

What are the Pros and Cons of Single Mode Fiber?


  • Transmission distance: single mode fiber supports a greater distance than multimode fiber because of its lower attenuation. For example, multimode fiber generally has a reach of several hundred meters, whereas single mode fiber has the potential to reach 200 km.
  • Bandwidth capacity: single mode fiber supports high bandwidths and high speeds up to 10Gbps for about 10Km, compared to a multimode fiber optic cable.
  • Data dispersion: single mode fiber only transmits light of one mode, causing no modal dispersion.
  • Attenuation: the fiber core in the single-mode fiber optic cable is relatively small, so very little light is reflected as it passes through, minimizing attenuation.


  • Stricter technology: because of the smaller core diameter, it is more difficult to manufacture and handle SMFs than MMFs.
  • High cost: single mode fiber devices are more expensive than multimode fiber devices because single mode fiber typically uses solid-state laser diodes.
  • Requires much tighter tolerances: it is difficult to couple light into a single mode fiber than into a multimode fiber because of the smaller fiber core diameter inside the SMF. The smaller cores (8-10 µm) require much tighter tolerances than coupling light into the larger cores (62.5/50 µm) of multimode fibers.

Applications of Single Mode Fiber Optic Cables

Single mode cable is mostly used in several applications where to need only one cable for sending at the multi-frequency (WDM Wave-Division-Multiplexing); such as –

  • Local area network as well as point to point links in many cities
  • One and multiple buildings
  • Small and medium scale companies
  • College campuses


Based on the aforementioned, single mode fiber is effective for network construction in a variety of circumstances. The easiest technique to eliminate modal dispersion over long distances is to utilize single mode fiber optical cable. As a result, single mode fiber is frequently used in backbone networks.

Another choice to extend HDMI signal across two building is using HDMI over fiber extenders. AV Access 4KEX300-F supports resolution up to 4K@60Hz 4:4:4 8 bit and HDCP 2.2, transporting HDMI signal up to 1000ft/300m over a duplex OM3 multi-mode optical fiber cable.

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