EN 50173 Fibre Optic Standard: What Planners and Installers Need to Know

EN 50173 defines structured cabling across Europe as the central fibre optic standard for the DACH region, establishing binding requirements for all fibre installations. The standard sets mandatory specifications for transmission classes, attenuation values, and link budgets that planners and installers must observe during fibre network design and deployment. In practical terms, this means: maximum channel attenuation of 1.5 dB for multimode links up to 300 metres and 2.0 dB for singlemode up to 2000 metres in the tertiary segment.

Fundamental Requirements of EN 50173 for Fibre Optic Cabling

EN 50173 comprises several part standards covering specific application areas. EN 50173-1 defines general requirements, while EN 50173-2 focuses on office buildings. For industrial environments, EN 50173-3 applies, imposing enhanced requirements for mechanical resilience and environmental conditions.

As a planner, you must consider three essential hierarchy levels when designing to EN 50173. Primary cabling connects sites with routes up to 3000 metres. Secondary cabling within buildings allows up to 500 metres. Tertiary cabling from the floor distributor to the workplace is limited to maximum 100 metres.

Cabling Level	Maximum Route Length	Typical Fibre Type	Attenuation Budget
Primary cabling	3000 m	OS2 Singlemode	3.5 dB
Secondary cabling	500 m	OM3/OM4/OS2	2.5 dB
Tertiary cabling	100 m	OM3/OM4	1.5 dB

Transmission Classes and Performance Requirements per EN 50173

The standard defines various optical classes for different transmission speeds and wavelengths. Class OF-300 supports Gigabit Ethernet over 300 metres with OM3 fibres. Class OF-500 enables 10 Gigabit Ethernet over 500 metres with OM4 fibres. For singlemode applications, Class OS-2000 specifies transmission up to 2000 metres.

• OM3 fibres: 2000 MHz·km at 850 nm, optimised for VCSEL lasers
• OM4 fibres: 4700 MHz·km at 850 nm, extended bandwidth
• OM5 fibres: Wavelength multiplex capable for 850–950 nm
• OS2 fibres: Singlemode for long-distance links up to 40 km

EN 50173 prescribes specific limit values for each class. Link loss comprises fibre attenuation and connector losses. For example, an OM4 installation over 150 metres with four connectors yields: 0.45 dB fibre attenuation plus 1.0 dB connector losses equals 1.45 dB total attenuation.

Measurement Requirements and Documentation per DACH Cabling Standard

EN 50173 requires comprehensive documentation of all installed links. Every fibre connection must be measured and recorded in accordance with IEC 61280-4-2. Measurements are performed bidirectionally at 850 nm and 1300 nm for multimode and 1310 nm and 1550 nm for singlemode.

Installers must document the following measurement values: link attenuation in both directions, reflectance attenuation at all connectors, and the optical length of the link. Reflectance attenuation must be at least 35 dB for multimode and 45 dB for singlemode.

• OTDR measurement for fault location and route characterisation
• Attenuation measurement with light source and power meter
• Microscopic endface inspection per IEC 61300-3-35
• Polarity verification for multi-fibre connectors such as MPO/MTP
• Documentation in digital asset registry

Connector Requirements in EN 50173

The standard permits various connector types but defines strict quality criteria. LC connectors per IEC 61754-20 dominate the tertiary segment due to their compact form factor. SC connectors per IEC 61754-4 are common in existing installations. The E2000 connector per IEC 61754-15 offers optimum contamination protection with its integrated shutter.

Connector Type	Insertion Loss	Return Loss PC	Return Loss APC
LC	< 0.25 dB	> 45 dB	> 60 dB
SC	< 0.30 dB	> 45 dB	> 60 dB
E2000	< 0.20 dB	> 50 dB	> 65 dB
MPO/MTP	< 0.35 dB	> 35 dB	> 60 dB

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Practical Implementation of EN 50173 in Splice Modules

Splice modules form the central nodes in structured cabling per EN 50173. The standard mandates clear identification of all fibres and ports plus adequate bend radii of at least 30 mm for singlemode and 25 mm for multimode. Modern splice modules meet these requirements through pre-configured cassettes with integrated fibre management.

Packing density plays a decisive role in planning. EN 50173 recommends filling no more than 60 percent of available distributor capacity to allow for future expansion. In a 19-inch distributor with 96 fibres per 1 RU, initially only 60 fibres should be installed.

• Reserve at least 1 metre of slack per fibre
• Separate routing of singlemode and multimode
• Colour coding per DIN VDE 0888
• Strain relief for all incoming cables
• Dust shutters for unused ports

Fire Safety and Environmental Requirements of the European Fibre Optic Standard

EN 50173 references the Construction Products Regulation and requires compliance with Euroclass Dca for fibre optic cables in buildings. Cables must be classified per EN 50575 and contribute only limitedly to flame spread in case of fire. Smoke production must meet class s2 and dripping behaviour class d1.

Different building areas have specific requirements. Escape routes mandate halogen-free cables of class B2ca. Risers require class Cca. Standard office areas are satisfied with class Dca. Documentation of cable types used is relevant for inspection.

Quality Assurance and Acceptance Criteria per EN 50173

Standards-compliant acceptance of a fibre installation requires systematic testing. Every installed link must meet defined limit values. Total attenuation must not exceed the calculated link budget. Optical return loss must meet minimum values.

• Visual inspection of all connectors at 200× magnification
• Attenuation measurement with calibrated instrument
• OTDR reference measurement for asset documentation
• Verification of mechanical strain relief
• Inspection of minimum bend radius compliance
• Completeness check of labelling

The acceptance report must contain all measurement results, measurement instruments with calibration dates, and names of testing personnel. Warranty services from many manufacturers require standards-compliant installation and documentation.

Integration of Modern Transmission Technologies in the DACH Cabling Standard

EN 50173 accommodates current and future transmission technologies. For 40 and 100 Gigabit Ethernet, the standard defines special requirements for multi-fibre connectors. MPO/MTP connectors enable parallel transmission over 12 or 24 fibres. Polarity must be configured per Method B.

Wavelength multiplexing techniques expand transmission capacity of existing fibres. EN 50173 supports CWDM with 18 channels and DWDM with up to 96 channels. Spectral attenuation must be specified for the range 1260 to 1625 nm. OM5 fibres additionally enable SWDM in the range 850 to 950 nm.

Special Requirements for Industrial Environments per EN 50173-3

Industrial environments impose heightened demands on fibre optic cabling. EN 50173-3 defines four environmental classes from M1 (office environment) to M4 (heavy industrial). Temperature range, vibration, electromagnetic interference, and chemical exposure determine the classification.

Environmental Class	Temperature Range	Protection Grade	Typical Application
M1	0°C to +50°C	IP20	Office, control room
M2	−25°C to +70°C	IP54	Warehouse
M3	−40°C to +85°C	IP65	Outdoor area
M4	−40°C to +85°C	IP67	Process environment

Future-Proof Design Through Standards-Compliant Planning

EN 50173 continues to evolve and integrate new technologies. The current edition already accommodates 400 Gigabit Ethernet and Terabit transmission. Planners should factor in reserves for future bandwidth demands. An oversizing of 30 percent has proven effective in practice.

Selecting high-quality components pays off long-term. Singlemode cabling offers virtually unlimited bandwidth reserves. Modular distributor systems allow flexible adaptation without recabling. The initial additional investment is recovered through reduced operational costs and extended service life.

• Use OS2 singlemode for all links exceeding 100 metres
• Install OM5 multimode for short high-speed links
• Provision for MPO breakout cassettes
• Consider microcables for future extensions
• Document in digital twin for operational management

Practical Tools for EN 50173 Implementation

Various software solutions assist planners in standards-compliant design. Calculation programmes automatically determine attenuation budgets and verify limit values. CAD systems with integrated standards libraries simplify documentation. Project management tools help coordinate complex installations.

The right test equipment is critical for quality assurance. Modern OTDR instruments provide automatic evaluation per EN 50173. Video microscopes with image analysis objectively assess connector endfaces. Cloud-based documentation systems enable central management of all test reports.

Frequently Asked Questions About EN 50173 European Fibre Optic Standard

Which fibre categories are suitable for 10 Gigabit Ethernet?

For 10 Gigabit Ethernet, OM3 fibres up to 300 metres, OM4 fibres up to 550 metres, and OS2 singlemode for distances up to 10 kilometres are appropriate. EN 50173 defines corresponding transmission classes OF-300, OF-550, and OS-10000.

How many connectors are permitted at maximum?

EN 50173 does not limit the number of connectors but rather the total attenuation budget. With high-quality connectors rated at 0.25 dB insertion loss, typically four to six connectors are feasible without exceeding limit values.

Which measurements are mandatory at acceptance?

Bidirectional attenuation measurement at specified wavelengths and documentation of all values are mandatory. OTDR measurements are recommended but not required. Endface inspection is considered standard practice in modern installations.

Does EN 50173 apply to existing networks?

The standard primarily applies to new installations. For expansions of existing networks, new components should meet current requirements. Full retrofitting is necessary only during major modernisations.

How does EN 50173 differ from ISO/IEC 11801?

EN 50173 is the European implementation of international ISO/IEC 11801 with specific adaptations for the European market. Additional requirements primarily concern fire safety and environmental aspects per European directives.

What documentation must be retained?

Complete installation documentation including network plans, measurement results, and component lists must be available throughout the network’s operational life. Digitally archived documents should be stored in standardised formats such as PDF/A.

Consistent application of EN 50173 as the central DACH cabling standard safeguards investment in modern fibre infrastructure. Planners and installers adhering to defined standards create future-proof networks with guaranteed performance. As a manufacturer of modular fibre optic solutions, Fiber Products supports you with standards-compliant systems meeting all EN 50173 requirements and renowned for Swiss precision quality.

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