Single Mode Fiber: How Much Do You Know?

Posted on  by FS.COM

Fiber optic cable is categorised into single mode fiber and multimode fiber optic cable. Both of them use a kind of or many kinds of glass fiber to transmit data. Among them, single mode fiber optic cable may offer the best future proof capabilities, for which it holds advantages in terms of bandwidth and reach for longer distances. However, how much do you know about single mode fiber?

Single Mode Fiber

What Is Single Mode Fiber?

In optical fiber technology, single mode fiber (SMF) or monomode fiber, is an optical fiber that is designed for the transmission of a single ray or mode of light as a carrier to propagate 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. The small single mode fiber core size and single light push virtually eliminate any distortion that could result from overlapping light pulses. Therefore, single mode optical fiber cable provides the least signal attenuation and the highest transmission speeds of any fiber cable type. For these reasons, single mode optical fiber is the best choice for transmitting data over long distance.

8 to 10µm single mode fiber

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 categorised into OS1 and OS2, which are cabled SMF fiber specifications. OS1 and OS2 are standard single mode optical cables respectively used with wavelengths of 1310nm and 1550nm with a maximum attenuation of 1 dB/km and 0.4 dB/km. The following table explains the differences between OS1 and OS2.

Name OS1 OS2
Standards ITU-T G.652A/B/C/D ITU-T G.652C/D
Cable Construction Tight buffered Loose tube
Application Indoor Outdoor
Maximum Attenuation 1.0dB/km 0.4dB/km
Distance 10 km 200 km
Price Low High

In a nutshell, OS1 fiber is a tight buffered cable designed for use in indoor applications (such as campuses or data centers) where the maximum distance is 10 km. OS2 fiber is a loose tube cable designed for use in outdoor cases (like street, underground and burial) where the maximum distance is up to 200 km. Both OS1 and OS2 fiber optic cable allow a distance of gigabit to 10G Ethernet. Besides, OS2 fiber can support 40G and 100G Ethernet.

Single Mode Fiber vs Multimode Fiber

Core Diameter

Single mode fiber core diameter is much smaller than multimode fiber. A typical single mode cable is a core diameter of 8 to 10μm, while multimode fiber is 50 or 62.5μm. The cladding diameter of both is 125 μm.

optical fiber core diameter

Light Source

Laser and LED are usually used as a light source. The LED light source produces more dispersed light (many modes of light), these light sources are usually used in multimode fiber jumpers (OM1 and OM2). At the same time, laser light sources (which produce light close to a single mode) are commonly used for single mode cables.

Modal Dispersion

Lasers used to drive single mode fiber produce a single wavelength of light. Therefore, its modal dispersion is much smaller than multimode fiber.

Single Mode Fiber vs Multimode Fiber Modal Dispersion


Since single mode fiber has less modal dispersion than multimode fiber, SM fiber has a higher bandwidth than multimode fiber.

Signal Attenuation

The attenuation of multimode fiber is higher than SM fiber. The fiber core of single mode cable is very narrow, so the light that passed through these fiber optical cables is not reflected too many times, which keeps the attenuation to a minimum.

9/125 Single Mode Fiber Simplex 50/125 OM3 Multimode Fiber
Attenuation at 1310nm 0.36 dB/km Attenuation at 850 nm 3.0 dB/km
Attenuation at 1550nm 0.22 dB/km Attenuation at 1300 nm 1.0 dB/km


Single mode fiber has a greater distance than multimode fiber. Multimode fiber generally has a reach up to 2 km, whereas SM fiber has the potential to reach 200 km.

Single Mode Fiber vs Multimode Fiber transmission distance

Single mode fiber provides higher transmission rate and up to 50 times more distance than multimode fiber. The following table shows the single mode fiber speed and distance:

Data Rate Cable Fiber Type Maximum Distance
Fast Ethernet (100BASE-FX) 9μm single mode 1310nm 2 km
Gigabit Ethernet (1000BASE-SX) 9μm single mode 1310nm 5 km
Gigabit Ethernet (1000BASE-LX) 9μm single mode 1310nm 5 km
Gigabit Ethernet (1000BASE-EX) 9μm single mode 1310nm 40 km
Gigabit Ethernet (1000BASE-ZX) 9μm single mode 1550nm 70 km
Gigabit Ethernet (1000Base-LH) 9μm single mode 1550nm 70 km
10G Ethernet (10GBASE-LR) 9μm single mode 1310nm 10 km
10G Ethernet (10GBASE-SR) 9μm single mode 1310nm 10 km
10G Ethernet (10GBASE-ER) 9μm single mode 1550nm 40 km
10G Ethernet (10GBASE-ZR) 9μm single mode 1550nm 80 km
40 Gigabit Ethernet (40GBASE-LR4) 9μm single mode 1310nm 10 km
40 Gigabit Ethernet (40GBASE-ER4) 9μm single mode 1550nm 40 km
100 Gigabit Ethernet (100GBASE-LR4) 9μm single mode 1310nm 10 km
100 Gigabit Ethernet (100GBASE-ER4) 9μm single mode 1550nm 40 km
100 Gigabit Ethernet (100GBASE-CWDM4) single mode fiber 2 km

Color Sheath

According to the TIA-598C standard definition, for non-military applications, single mode cable is coated with yellow outer sheath, and multimode fiber is coated with orange or aqua jacket.

Single Mode Fiber vs Multimode Fiber color


Multimode fiber can support multiple light mode, its price is higher than single mode fiber. However, on the device side, single mode fiber devices are more expensive than multimode fiber devices because single mode fiber typically uses solid-state laser diodes. For more information about cost comparison between single mode fiber and multimode fiber, please refer to Single-mode Cabling Cost vs. Multimode Cabling Cost

Single Mode Fiber Connector Types

A fiber optic connector terminates the end of a fiber optic cable. A number of fiber optic connector types have been evolved and withstood the test of time to become industry standards. The main types of single mode fiber connectors include: ST, FC, SC, and LC. Get more details about commonly used fiber optic connectors here: Fiber Optic Connector Types, Market, & Installation

What’s the Advantages of Single Mode Fiber?

Through the introduction of single mode fiber and single mode fiber vs multimode fiber, we can see many advantages of single mode fiber:

Longer Transmission Distance
Greater Bandwidth Capacity
Increased Transmission Speed
Limited Data Dispersion & External Interference
Less Signal Attenuation

Single mode fiber doesn’t have modal dispersion, modal noise, and other effects that come with multimode transmission. So it can carry signals at much higher speeds than multimode fibers. They are standard choice for high data rates or long distance span telecommunications which use laser diode based fiber optic transmission equipment.


The use of single mode fiber optical cable is the best way to get rid of modal dispersion over long distance. So it is very popular to be used in backbone systems, and a number of large companies use SMF cables to wire up an entire building or a corporate office. Compared to multimode fiber cable, these fiber patch cords are future-proofing and an effective way to save money on the hardware by purchasing these cables in bulk.