Fibre Optic Standards

The information provided in this page provides only a basic understanding and guidance, which you will need to verify or use at your own discretion.

 

ITU-T G.653 Compliant Dispersion shifted fibre
These fibres are designed to utilize the low attenuation window of 1550nm by minimizing the dispersion value at around 1550nm. The purpose was good, but it generated Non-linear effects in the transmission which caused more troubles.

ITU-T G.654 Compliant Cut-off Shifted fibre
This fibre is also known as low attenuation fibre. Some manufacturers have extremely low attenuation at 1550nm for this fibre. The application area demands low attenuation like those in Submarine optical fibre cables and terrestrial ultra long haul optical networks. Low attenuation at 1550nm range makes this fibre suitable for 400km span without repeaters. The low attenuation ranges from 0.15 – 0.16 dB/km.

ITU-T G.655 Compliant Non-zero dispersion shifted fibre
NZDSF is the short of Non-zero dispersion shifted fibre. These are wide band transmission supporting fibres. The non-linear effects due to zero dispersion at 1550nm in G.653 fibres are solved by G.655 fibres which are having a non-zero value for dispersion at these wavelength range. ITU-T specifies up to G.655E fibres (latest) from G.655A fibres which are not currently in use.
G.655 fibres are most suitable for DWDM applications. The non-linear effects are successfully solved in G.655 fibres.

ITU-T G.656 Compliant Low Slope Dispersion Non-zero Dispersion shifted fibre
This is another type non-zero dispersion shifted fibre which has more stricter and low dispersion slope which enables to guarantee the DWDM performance in wide wavelength range.
 

ITU-T G.657 Compliant Bend Insensitive fibre
G.657 fibres are the new comers in the market, but became a super hit in the FTTH market. More and more installers are looking for G.657 fibres. As the name indicates, the bend insensitive fibres are suitable for applications where multiple bends will be present. Insensitivity to bends makes them suitable for installation at home and office environment. G.657A is intended to compatible with G.652 D fibres. Interconnectivity with the existing G.652 fibres are guaranteed for the G.657 A fibres.
 

ITU-T G.657B fibres are free from all backward compatibility requirements and does not require to comply with conventional single mode fibres. The difference between 657A and B fibres is in the bending radius. G.657B can be bend at 7.5mm radius and less for some manufacturers.

 

Links for free download of ITU-T Specifications for Optical fibres and related systems.

G.650.1 : Definitions and test methods for linear, deterministic attributes of sm fibre and cable

G.650.2 : Test methods for statistical and non-linear related attributes of sm fibre and cable

G.650.3 : Test methods for installed single-mode optical fibre cable links

G.651.1 : Characteristics of a 50/125 µm MM GI index OF cable for the optical access network

G.652 : Characteristics of a single-mode optical fibre and cable

G.653 : Characteristics of a dispersion-shifted single-mode optical fibre and cable

G.654 : Characteristics of a cut-off shifted single-mode optical fibre and cable

G.655 : Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable

G.656 : Characteristics of a fibre and cable with non-zero dispersion for wideband optical transport

G.657 : Characteristics of a Bending Loss Insensitive SM OF and Cable for the Access Network

G.661 : Relevant generic parameters of optical amplifier devices and subsystems

G.662 : Generic characteristics of optical amplifier devices and subsystems

G.663 : Application related aspects of optical amplifier devices and subsystems

G.663 : Amendments to Appendix II

G.664 : Optical safety procedures and requirements for optical transport systems

G.665 : Generic characteristics of Raman amplifiers and Raman amplified subsystems

G.667 : Characteristics of Adaptive Chromatic Dispersion Compensators

G.671 : Transmission characteristics of optical components and subsystems

G.680 : Physical transfer functions of optical networks elements

G.691 : Optical interfaces for single channel STM-64 and other SDH systems with optical amplifiers

G.692 : (1998) Amendment 1 (01/05)

G.692 : Optical interfaces for multichannel systems with optical amplifiers

G.693 : Optical interfaces for intra-office systems

G.694.1 : Spectral grids for WDM applications: DWDM frequency grid

G.694.2 : Spectral grids for WDM applications: CWDM wavelength grid

G.695 : Optical interfaces for coarse wavelength division multiplexing applications

G.696.1 : Longitudinally compatible intra-domain DWDM applications

G.697 : Optical monitoring for DWDM systems

G.698.1 : Multichannel DWDM applications with single-channel optical interfaces

 

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There are many standards that are either directly or indirectly relevant to fibre optics

The ITU G650 series (includes ITU G.651, G.652, G.653, G.654, G.655. G.656 & G.657 recommendations) standards deal with recommended specifications for various optical fibre types, with G.650 itself dealing with the optical test methods used to verify the fibre specifications. These standards are developed by the International Telecommunications Union (ITU), and are truly international recommendations in that they are referred to all over the world.

The BS 7718 standard, now withdrawn, is the Code of Practice for the installation of fibre optic cabling. This was a very significant document in that it stated how fibre optic cables should be safely installed and tested. Although now withdrawn so as not to conflict with other newer standards, there are elements of BS 7718 that have not yet been released in any other standards, and so some companies and organisations have chosen to still reference this standard. A British standard developed from some FIA documents by the BSI, this standard found widespread appeal outside of the UK due to the lack of an equivalent international or European standards for many years.

IEC 11801 is the international standard developed jointly by ISO (International Standards Organisation) and the IEC (International Electro technical Commission) and is more properly therefore ISO/IEC 11801. The standard is entitled "Information technology - Generic cabling for customer premises" and deals with both copper and fibre optic cabling in buildings. Effectively this is a local area network (LAN) structured cabling standard, although it is important in that it is one of very few standards that detail installation specifications. A closely related standard is the BS EN 50173 standard.

BS EN 50173 is the European standard broadly equivalent to IEC 11801. In the UK this standard is publishes by BSi as BS EN 50173 and is entitled "Information technology - Generic cabling systems". Different parts of this standard are purchased separately and deal with different installation environments.

BS EN 50174 is the European standard now dealing with the installation aspect of IT cabling for fibre optic and copper datacoms cables. Released in the UK by BSI as BS EN 50174, this standard comes in three parts identified on the cabling standards page.

BS EN 50346 European standard covering the testing of installed fibre optics cabling for IT systems. The BSI version of this standard is BS EN 50346 "Information technology - Cabling installation - Testing of installed cabling".

ISO / IEC 14763-3 standard covering the testing of datacoms networks. It is complex for the uninitiated to understand, and takes a different approach to earlier datacoms testing standards, but makes sense given the growing trend for duplex fibre networks and different connector styles at either end of a fibre.

IEC 60825-2 and BS EN 60825-2 are the international and European standards dealing with laser safety in optical fibre communications systems. With the advent of more powerful laser transmitters and in particular optical amplifiers with laser power levels as high as those produced by Raman amplifier system lasers, this standard is becoming more and more important.

OM1, OM2, OM3, OM4 OS1, and OS2 Fibre

In ISO/IEC 11801:2002 and EN50173:2002, four types of optical fibre are specified to support various classes of applications, three multimode optical fibre types (OM1, OM2, and OM3) and one single-mode type (OS1). 

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In the draft Amendment 2 to ISO/IEC 11801:2002 there is the addition of OS2 fibre. 

At the ISO February meeting in Barcelona, ISO/IEC JTC1 SC25 WG3 proposed the establishment of two new optical fibre types or Categories - one multimode and one single-mode. In terms of standardisation, it is unlikely that changes to the list of “OM”s and “OS”s will take place before 2009. However, marketing literature already contains these new designations.

The multimode variant, currently termed OM4, will provide twice the laser/VCSEL bandwidth of OM3 and is targeted to provide greater useable distance and/or lower system implementation costs for the next generation 40 Gb/s and 100 Gb/s Ethernet solutions that are currently in development. 
 
The reference and launch cables Fluke Networks uses are made with OM1 (62.5/125 µm) and OM3 (50/125 µm) fibre for Multimode Adapters and OS1 (9/125 µm) for Single-mode Adapters. For OTDR and fibre optical loss measurements, mixing OM2 with OM3 fibre has no impact on the measurement.
 

Band

Descriptor

Range (nm)

O band

Original

1260 to 1360

E band

Extended

1360 to 1460

S band

Short wavelength

1460 to 1530

C band

Conventional

1530 to 1565

L band

Long wavelength

1565 to 1625

U band

Ultralong wavelength

1625 to 1675

 

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

  • ITU G.651    Covers multimode graded-index fibre-optic cable having a 50-micron nominal core diameter and a 125-micron nominal cladding diameter.
     

  • ITU G.652    Covers single-mode NDSF (non-dispersion-shifted fibre). This cable constitutes most of the cable that was installed in the 1980s. Transmissions take place in the 1,310-nm range where there is minimal signal dispersion. Dispersion causes signal problems over long distances, as described later. G.652 cable supports the following distances and data rates: 1000 km at 2.5 Gbits/sec, 60 km at 10 Gbits/sec, and 3 km at 40 Gbits/sec.
     

  • ITU G.653    Covers single-mode dispersion-shifted optical fibre cable. The cable is designed in a way to "shift" the region where dispersion is minimized to the 1,550-nm wavelength range. At this range attenuation is also minimized, so longer distance cables are possible.
     

  • ITU G.655    Covers single-mode NZ-DSF (nonzero dispersion-shifted fibre) cable, which takes advantage of dispersion characteristics that suppress the growth of four-wave mixing, an effect that is harmful to 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. It supports the following distances and data rates: 6000 km at 2.5 Gbits/sec, 400 km at 10 Gbits/sec, and 25 km at 40 Gbits/sec.

  • G.657 The characteristics of a bending loss insensitive single mode

    Optical fibre and cable for the access network, ITU G.657 standard describes fibres with

    improved macro bend performance. The standard describes two classes of fibres

     

    Class A- Fully compliant with G.652.D with improved bending performance. The minimum designed bend

    radius is 10 mm.

     

    Class B- Fibre designs for niche indoor wiring

    projects with very low macro bend loss not required

    to be compliant with G.652 standard. The minimum designed bend radius is 7.5 mm.

G.655 fibre-optic cable. In particular, G.655 is optimized for WDM and long-distance cable runs such as submarine cables. It uses dispersion to advantage. Dispersion can help reduce an effect called 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.

With DWDM, a single fibre can potentially carry thousands of lambda circuits. A lambda is a specific sub-wavelength of light within one of the windows of light. It provides all the capabilities of an individual circuit. Lambdas are set up using frequency division multiplexing. Think of each lambda as a specific colour of infrared light transmitting at 10 Gbits/sec or more. An optical multiplexer divides the available spectrum on the cable up into many individual lambdas. For example, A PowerMux can put over 800 channels on a single fibre with spacing between channels of 12.5 gigahertz. With the potential of thousands of lambdas per fibre, it is practical for carriers to lease entire optical wavelengths to businesses.

An alternative to DWDM are new optical modulation techniques that boost the capacity of existing cables. Kestrel Solution's Optical FDM combines FDM (frequency division multiplexing), DSP (digital signal processing), and optical modulation to improve performance on existing fibre cables, especially in metropolitan areas where low-quality fibre has been installed (due to short distances) and in SONET systems. Optical FDM gives full access to the total bandwidth of the cable.

Optical fibre cable attenuation

Maximum cable attenuation  dB/km

Fibre

OM1, OM2, and OM3 Multimode

OS1

Singlemode

Wavelength

850 nm

1300 nm

1310 nm

1550 nm

Attenuation

3.5

1.5

1.0

1.0

Multimode optical fibre

modal bandwidth

Minimum modal bandwidth MHz•km

Overfilled Launch Bandwidth

Effective Laser Launch Bandwidth

Wavelength

850 nm

1300 nm

850 nm

Optical fibre type

Core diameter

 

 

 

OM1

50 µm or 62.5 µm

200

500

Not specified

OM2

50 µm or 62.5 µm

500

500

Not specified

OM3

50 µm

1500

500

2,000


The ISO/IEC 11801:2002 and EN50173:2002 specifies optical channel and link Classes OF-300, OF-500, and OF-2000 meeting the requirements of standardised applications and exploiting component capabilities to ease the implementation of applications developed in the future. These classes are designed using either OM1, OM2 or OM3 fibre.
 
OM3 fibre allows the use of 10GBASE-S up to 300 metres using a VCSEL at 850 nm.  

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ITU-T G.651 compliant Multimode fibres and OM1
Multimode fibres can be classified further into two as Multimode 50/125 and Multimode 62.5/125. The classification is based on the core diameter of multimode fibres. 50/125 have a core diameter of 50 micrometers, whereas for 62.5/125 have a core diameter of 62.5 micrometers.

Recent classification of multimode fibres divides them as OM1, OM2, OM3 & OM4 etc. OM1 multimode fibres are 62.5/125 multimode fibres. OM2 and OM3 fibres are compliant with ITU-T G.651 recommendations.

There is a confusion regarding the classification. If any of our reader knows correct way of classification please put a comment. G.651 multimode fibres are used mainly in Local Area Networks (LAN). Multimode fibres are not suitable for Long haul applications. Cheaper transmission devices like lasers etc makes Multimode fibres attractive for short distance transmission within the 300 to 500 meters reach.

For a 10GBASE-SR system demanding 2000 MHz*km, OM2 multimode fibre can be used for a distance of up to 82 meters and OM3 fibres can be used for 300 meters. An OM2 fibre having a bandwidth of 500 MHz*km can be used for 550 meters on a 10BASE-SX/LX networks.

ITU-T does not have any specification for 62.5/125 multimode fibres. OM1 Fibres also know as 62.5/125 Multimode fibres are popular in United States. OM2 and OM3 multimode fibres are also known as ITU-T G.651 fibres.
 

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The core of MMF 50/125 has a graded index refractive index profile, which is gradually changing from the center of the core to the cladding that enables multiple modes with near equal velocity to travel inside the fibre.

ITU-T G.652 Compliant Single Mode fibres
This is the most common single mode fibre in the world. It is designed to have minimum dispersion at around 1310nm, which is supposed to be transmission window for single mode fibres. Conventional single mode fibres can be used at 1550nm with the use of dispersion compensation modules.

G.652A is the first single mode fibres ITU-T classified. G.652B fibres are also known as conventional type single mode fibres and many installers intend to use 652B fibre by mentioning simply G.652. The major difference is in attenuation at both 1310nm and 1550nm and polarization mode dispersion. 652B fibres have a PMD as low as 0.2 ps/sqrt.km where as for 652A fibres have a PMD of 0.5 ps/sqrt.km. Attenuation is low for G.652B fibres.

Similarly G.652C and G.652D fibres differ in PMD value. PMD for G.652C fibre is 0.5 ps/sqrt.km, where as for G.652D fibres have a PMD of less than or equal to 0.2 ps/sqrt.km. Both these optical fibres are known as low water peak fibre having low attenuation at 1360nm through 1480nm, the wavelength range which is not yet used commonly for transmission.

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