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Singlemode Fiber Types

There are several designations used to describe various types of SM fiber that are often confusing. Here are the ones in common use today.

 

Description	IEC SMF Type	ITU Spec.	TIA Spec
Standard Singlemode Fiber	B1.1	G.652	OS1
Cutoff Shifted Fiber	B1.2	G.654
Low Water Peak Fiber	B1.3	G.652	OS2
Dispersion Shifted Fiber	B2	G.653
Non-Zero Dispersion Shifted Fiber	B4	G.655

The standards bodies with vested interest in the governance of optical fiber specifications are:

ISO (International Organization for Standardization) – Formed of manufacturers and standards bodies representing over 90 nations. For optical fiber specifications and standards, ISO and IEC collaborate on several Joint Technical Committees (JTC).

IEC (International Electrotechnical Commission) – IEC addresses the electronics and telecommunications industries, and counts over 50 nations among its membership. The current IEEE 802.3 standard for Ethernet cites TIA-568 and ISO/IEC 11801 for optical fiber specifications.

TIA (Telecommunications Industry Association) – Now part of the Electronic Industries Alliance (EIA). TIA is comprised of manufacturers who are primarily suppliers to the telecom industry but include other interested groups. TIA is primarily involved (through the American National Standards Institute or ANSI) in optical fiber and system test standards.

ITU (International Telecommunication Union) – The ITU is part of the United Nations System of Organizations, and over 180 countries currently are represented within the ITU. The ITU administers the commonly referenced single-mode fiber standards documents, G.652 through G.655, as required by telecom systems manufcturers and their customers.

The ITU has defined a series of recommendations that describe the geometrical properties and transmissive properties of multimode and single-mode fiber-optic cables. The four most important recommendations are listed here:

ITU G.651    Covers multimode 50/125 micron graded-index fiber.

ITU G.652    Covers single-mode NDSF (non-dispersion-shifted fiber). This fiber is in most of the cable that was installed in the 1980s. Optimized in the 1,310-nm range. Low water peak fiber has been specifically processed to reduce the water peak at 1400 nm to allow use in that range. There are 4 subcategories:

G.652A :
   Atten </= 0.5 / 0.4 at 1310 / 1550nm
Macrobend </= 0.5 dB at 1550nm
PMD </= 0.5 ps/sqrt(km)

G.652B :
   Atten </= 0.4 / 0.35 / 0.4 at 1310 / 1550 / 1625nm
Macrobend </= 0.5 dB at 1625nm
PMD </= 0.2 ps/sqrt(km)

G.652C :
   Atten </= 0.4 from 1310 to 1625nm, </= 0.3 at 1550nm, and
at 1383nm, it must be </= that specified at 1310nm, after hydrogen aging.
Macrobend </= 0.5 dB at 1625nm
PMD </= 0.5 ps/sqrt(km)

G.652D (covers all above):
   Atten </= 0.4 from 1310 to 1625nm, </= 0.3 at 1550nm, and
at 1383nm, it must be </= that specified at 1310nm, after hydrogen aging.
Macrobend </= 0.5 dB at 1625nm
PMD </= 0.2 ps/sqrt(km)

ITU G.653    Covers single-mode dispersion-shifted optical fiber. Dispersion is minimized in the 1,550-nm wavelength range. At this range attenuation is also minimized, so longer distance cables are possible.

ITU G.654: Covers single-mode fibre which has the zero-dispersion wavelength around 1300 m wavelength which is cut-off shifted and loss minimized at a wavelength around 1550 nm and which is optimized for use in the 1500-1600 nm region.

ITU G.655    Covers single-mode NZ-DSF (nonzero dispersion-shifted) fiber) , which takes advantage of dispersion characteristics that suppress the growth of four-wave mixing, a problem with WDM (wavelength division multiplexing) systems. NZ-DSF supports high-power signals and longer distances, as well as closely spaced DWDM (dense WDM) channels at rates of 10 Gbits/sec or higher. G.655 is optimized for WDM and long-distance cable runs such as transoceanic cables. It uses dispersion to reduce the effect of four-wave mixing (FWM), which occurs in DWDM systems when three wavelengths mix in such a way to produce a fourth wavelength that overlays and interferes with the original signals.

TIA TR-42 specifies singlemode fiber for premises applications. OS1 or OS2 fiber for outdoor or indoor/outdoor applications is specified for a maximum attenuation of 0.5 dB/km at either 1310 05 1550 nm. For indoor applications,  OS1 or OS2 fiber  is specified for a maximum attenuation of 1.0 dB/km at either 1310 05 1550 nm.

(C) 2002-9, The Fiber Optic Association, Inc.

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