Single-mode Fiber OS1 vs OS2: Differences, Chose Guide – QSFPTEK

Single-mode Fiber OS1 vs OS2: Differences, Chose Guide

Optical fiber cable is the most widely used transmission media today, which has many advantages such as high bandwidth, long-distance relay, high reliability, small volume, lightweight, etc. It consists of two types, single-mode fiber type, and multimode fiber type. Multimode fiber type is generally used in short-range transmission. It includes 5 types, OM1, OM2, OM3, OM4, and OM5. Conversely, single-mode fiber is used in long-range transmission, and it has two common types, OS1 and OS2. Then, what are the differences between OS1 and OS2? Which one should I choose between OS1 and OS2? This blog will help.

What is Single-mode Fiber?

Single-mode fiber is designed to carry only a single mode of light. It has a very thin fiber core of about 8 to 10.5 µm. Compared with multimode fiber, single-mode fiber has a lower transmission loss and transmission dispersion, so single-mode fiber enables a longer transmission distance and higher bandwidth than multimode fiber type. Therefore, single-mode fiber is widely used in high-speed and great-capability communication systems.

Types and Development of Single-mode Fiber

Since the 1970s, optical fiber transmission systems are constantly developing towards high-speed, long-distance, and large capacity, which promotes the development of the types and performance of the single-mode fiber. The following figure shows the evolution of optical fiber cable driven by the optical fiber transmission system.

The following is a brief introduction from G.652 fiber to G.657 fiber:

  • G.652: The most common single-mode fiber. Zero dispersion wavelength at  1310nm. Divided into four categories, G.652A, G.652B, G.652C, and G.652D based on whether there is a water peak. G.652C and G.652D are low water peak fibers, which eliminate the water peak of 1383nm and can work on a full wavelength of 1260nm~1675nm.
  • G.653: Dispersion-shifted single-mode fiber. Zero dispersion wavelength at 1310nm.
  • G.654: Cut-off shifted single-mode fiber. Designed for transoceanic fiber cables by using pure silica as the fiber core material to reduce the fiber attenuation.
  • G.655: Non-zero dispersion-shifted single-mode fiber. Designed for DWDM system to restrain four-wave mixing crosstalk.
  • G.656: Non-zero dispersion for wideband optical transport single-mode fiber. Designed for increasing the transmission capacity of the DWDM system to ensure the DWDM system can work at a wider wavelength of C, S, and L wavelengths.
  • G.657: Bending-loss insensitive single-mode optical fiber. Designed for FTTH (Fiber to the Home) to face the small space, frequent bending, and difficult operation of FTTH construction.

Differences Between Single-mode Fiber OS1 and OS2

What are OS1 and OS2 fiber? As mentioned above, G.652 consists of four categories, G.652A, G.652B, G.652C, and G.652D. OS1 is the single-mode fiber type that compalint with G.652A and G.652B, whereas OS2 is compliant with G.652C and G.652D. The following blog will introduce what are the differences between OS1 and OS2 in detail.

OS1 vs OS2: Defines, Standard, Wavelength, Attenuation

OS1 single-mode fiber is compalint with G.652A and G.652B while OS2 is compliant with G.652C and G.652D. Then, what are the differences between these four categories of G.652? The following table shows the major performance differences of G.652A, G.652B, G.652C, and G.652D.

SMF Type OS1 OS1 OS2  OS2
G.625 Category G.652A G.652B G.652C G.652D
1310nm Attenuation Coefficient(dB/km) 0.5  0.4 0.4 0.5
1550nm Attenuation Coefficient(dB/km) 0.4  0.35  0.3  0.3 
Macrobending Loss(dB) 0.5(1625nm) 0.5(1550nm) 0.5(1550nm) 0.5(1625nm)
PMD(ps/km^1/2) 0.5 0.2 0.5 0.2

From the above table, we can see the major differences of each category of G.652 fiber are PMD(Polarization Mode Dispersion) and the attenuation coefficient of the fiber link. G.652D fiber integrates a small PMD and wide bandwidth, that’s why it is the first choice of DWDM system within 10Gb/s transmission rate. Besides,  G.652C and G.652D are low water peak fibers, which overcome the influence of the water peak at 1383nm wavelength. So OS2 fiber can work at an extended wavelength including O-wavelength (1325-1360nm), E-wavelength(1360-1460nm), S-wavelength (1460-1530nm), and C-wavelength (1530-1560nm).

In this part, we can conclude the difference between OS1 and OS2 include:

  • G.652 Category: OS1 fiber is compliant with G.652A and G.652B, while OS2 is compliant with G.652C and G.652D. 
  • Wavelength: OS2 fiber enables a wider wavelength than OS1. OS2 supports O-wavelength, E-wavelength, S-wavelength, and C-wavelength, while OS1 only works at O-wavelength and C-wavelength.
  • Attenuation: OS2 fiber optimizes the attenuation and fiber dispersion. For 1310nm and 1550nm, the maximum attenuation of OS2 fiber is 0.4db/km, which is larger than 1.0db/km of OS1 fiber. 

OS1 vs OS2: Structure

OS1 single-mode fiber generally adopts a tight-buffered structure. It encloses fiber in a thick polymer jacket. The fiber core and cladding material is glass, which is fragile and less prone to bend. So OS1 fiber is more used indoor applications.

Different from OS1 single-mode fiber type. OS2 adopts a loose-tube structure. It has a semi-rigid protective sleeve and everything is enclosed within the sleeve so that the fiber core, cladding, and coating can be well protected. So OS2 can be used in outdoor applications.

In this part, the difference between OS1 and OS2 concluded as follows:

  • Structure: OS1 fiber uses a tight-buffered structure, while OS2 uses a loose-tube structure.
  • Application: OS2 fiber is applicable for outdoor uses, while OS1 is only suitable for indoor uses.

OS1 Fiber Structure vs OS2 Fiber Structure 

OS1 vs OS2: Speed, Distance

As a result of the lower attenuation, OS2 allows longer transmission distance and higher speed than OS1 single-mode fiber. 

  • Distance: OS1 supports the maximum distance is only 10km, while OS2 fiber is able to reach 200km. 
  • Speed: OS2 single-mode fiber allows transmission speed up to 40G/100G, while single-mode fiber OS1 is typically used in 1 to 10GbE speed.


 After the above discussion about the differences between OS1 and OS2, you must get clearly understand that OS2 has many advantages over OS1, such as wider wavelength, higher speed, longer transmission distance, lower attenuation, stronger structure, wider-ranging applications, etc. Since OS2 is at a comparable price to OS1, OS2 must be your first choice. QSFPTEK provides cost-effective and performance OS2 single-mode fiber cables at the best price, welcome to consult via

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