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Single-mode optical fiber cable (SMF) is classified into two categories; OS1 and OS2. These two kinds of optical fiber cables come with different characteristics. OS1 single-mode fiber cables are not compatible with OS1 type SMF cables. A link comprising of OS1 and OS2 type of single-mode fiber may not perform as desired because of poor signal performance. During cable deployment, the incompatibility between OS1 type and OS2 type of single-mode fiber cables should be kept in mind. In this article, we are going to discuss the major differences between the two SMF cable types.

Single-Mode Fiber Standards

ITU-T G.652 is the standard that contains recommendations about the transmission, mechanical, and geometrical attributes of single-mode optical fiber. The ITU-T G.652 standard can further be classified into four categories:

  • ITU-T G.652.A
  • ITU-T G.652.B
  • ITU-T G.652.C
  • ITU-T G.652.D

These categories are based on attenuation requirements and PMD requirements at 1383 mm. The G.652.A and G.652.B relates to conventional fibers. Whereas, the subcategories G.652.C and G.652.D contain recommendations regarding low water peak fibers.  


Differences between OS1 and OS2 type Single-mode Fiber Cables

OS1 optical cables are designed and manufactured according to the requirements as specified by ITU-T G.652 and its subcategories G.652A, G.652B, G.652C, and G.652D. 

Thus, it can safely be stated that OS1 SMF cables are designed to comply with all the design specifications and operation parameters mentioned in ITU-T G.652 and its subcategories. OS1 is a very broad term as it encapsulates a variety of single-mode fibers. 

OS2 single-mode fibers are also designed and manufactured on basis of the recommendations contained by the ITU-T G.652 standard. However, OS2 fibers are the ones that comply with the requirements defined in subcategories G.652.C and G.652.D, which means that OS2 single-mode fibers are low-water-peak fibers only.

OS1 vs. OS2 - Construction

OS1 single-mode optical fiber cables are designed for indoor applications. These cables come enclosed in a thick polymer jacket. OS1 cables are mostly deployed in scenarios where communication links within a campus or other kinds of information facilities are required. The tight-buffered construction of OS1 SMF cable ensures maximum protection of the fiber core and keeps it held firmly.


OS2 SMF optical cables come with a loose tube construction. The design characteristics of OS2 cables makes them a better choice for outdoor applications. The fiber core in these cables is contained by a semi-rigid, gel filled tube. Thus, OS2 cables can be stretched to an extent without causing any harm to the core.

OS1 Vs. OS2 - Attenuation (between 1310 and 1550 nm)

When it comes to attenuation, OS2 optical fiber cable offers better performance than OS1. In typical circumstances, the maximum attenuation of OS1 cable remains around 1 dB/kilometer. Whereas, the attenuation values for OS2 cable remains around 0.4 dB/kilometer. Consequently, the maximum link distance achievable through an OS2 cable is higher as it can reach up to 200 kilometers – much better than the maximum link distance of 10 kilometers that can be achieved through an OS1 optical fiber cable.


OS1 vs. OS2 SMF Cables - Which way to go?

OS1 and OS2 optical fiber cables are generally recommended for long-haul transmissions and you must choose the appropriate cable suitable for your application. 

OS1 cables are generally used in the construction of indoor networking infrastructures like the ones found on campus and building networks. Moreover, the OS1 cables are also used to achieve connectivity between data centers and telecommunication exchanges.

OS2 optical cables are preferred for outdoor applications which include backhaul networks and external plants. The tendency of the OS2 cables to support longer link distances makes this class a viable solution for scenarios where links are needed to be stretched over 2 kilometers.


  • OS1 cables are ideal for indoor, short-distance applications
  • OS2 cables are designed for outdoor applications
  • OS1 cables have a tight-buffered construction whereas OS2 cables come with a loose-tube design.
  • In terms of attenuation, OS2 outperforms OS1
  • OS1 optical fiber cables cost lower than OS2 cables.