Professional Manufacturer of Fiber Optic Products

How to Grade Fibre Patch Leads

As we know, fibre patch lead is a cable with connector(s) on either end. So when to grade the fibre patch leads, the right way is to make it clear how to grade the connectors and cable.

Connector

Let’s begin with the connector. There are two aspects that should be noted well about the connector.

The first one is end-face quality. The polishing process during producing fibre patch leads is the key to good performance. According to IEC-61300-3-35, the polished end-face of a connector is divided into measurement regions defined as follows.

End Face

Zone Diameter for single-mode Diameter for multimode
A: Core 0 um to 25 um 0 um to 65 um
B: Cladding 25um to 120 um 65um to 120 um
C: Adhesive 120 um to 130 um 120 um to 130 um
D: Contact 130 um to 250 um 130 um to 250 um

 

There are 3 different level requirements for single-mode defined as below.

Requirement for PC polished connector, single-mode fibre, RL  45dB
Zone name Scratches Defects
A: Core None None
B: Cladding No limit ≤ 3um

None > 3um

No limit < 2um

5 from 2um to 5um

None > 5um

C: Adhesive No limit No limit
D: Contact No limit None≥10um
Requirement for PC polished connector, single-mode fibre, RL  26dB
Zone name Scratches Defects
A: Core 2 ≤ 3um

None > 3um

2 ≤ 3um

None > 3um

B: Cladding No limit ≤ 3um

3 > 3um

No limit < 2um

5 from 2um to 5um

None > 5um

C: Adhesive No limit No limit
D: Contact No limit None≥10um
Requirement for APC polished connector, single-mode fibre
Zone name Scratches Defects
A: Core  ≤ 4

 

None
B: Cladding No limit No limit < 2um

5 from 2um to 5um

None > 5um

C: Adhesive No limit No limit
D: Contact No limit None≥10um

The second one is IL(insertion loss), RL(return loss). the quality of polishing will affect the IL&RL.

These parameters stand for the optical performance when mated with other connectors. According to IEC-61755-1, there are four grades to identify the optical performance of interface for single-mode fibre.

Attenuation grade Attenuation(>97%) Mean
A Reserved Reserved
B ≤0.25 ≤0.12
C ≤0.50 ≤0.25
D ≤1.0 ≤0.50
Return loss grade Return loss(mated) Notes
1 ≥60dB ≥55dB in unmated condition(APC only)
2 ≥45dB
3 ≥35dB
4 ≥26dB

 

Cable

When coming to the cable, especially fibre patch leads used in indoor applications. Most of the time, we are caring about the fire rate. There are three fire rates that widely used in applications.

OFNP, OFNR, OFN.

OFNP (Optical Fiber, Nonconductive, Plenum)

OFNP (optical fibre, nonconductive, plenum) is used in plenum applications. It is used between a ceiling and the floor above it, where space is reserved for the circulation of air. It has the highest rated fire retardant hence it emits little smoke during combustion. The non-conductive element within OFNP means it contains no electrically conductive components.

OFNR (Optical Fiber, Nonconductive, Riser)

OFNR (optical fibre, nonconductive, riser) is used in riser applications. It is used in vertical zone or space, such as the pathways that pass through floors inside a building, prevent fire from spreading from floors to floors within the building.

OFNR (Optical Fiber, Nonconductive)

Abbreviation for optical fibre nonconductive. OFN is the designation given by the National Fire Protection Association (NFPA) to interior Fiber optic cables that contain no electrically conductive component, and which are not certified for use in Plenum or Riser applications.

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