Fibre Optic Inspection Microscopes & IEC61300-3-35 Standard

We all know cleaning is a fundamental procedure when it comes to fibre optic systems.

But is cleaning alone enough to guarantee the operation of your network?

The difficulty we face is that the fibre in the ferrule of the connector is not much larger than a strand of human hair.

So it is near impossible to see any dust or dirt on it without a microscope!

Yamasaki Handheld Microscopes

So what are some of the consequences of fibre that is contaminated?

  • High Link Loss and Connectors loss
  • Failed ORL (optical return loss)
  • RIN (relative intensity noise) caused by reflections
  • Loss of time trying to solve issues
  • Network outages
  • Increased failure rates

What can we do to prevent these issues?

Prevention, as always, is better than the cure and this can be achieved by;

  • careful handling of connectors,
  • ensuring dust caps are always fitted when not in use,
  • not touching the endface with fingers to avoid contamination,
  • inspection of the endface prior to connection to ensure the connector meets standards.

Inspection is vital - some contaminants can be very hard to remove and may require cleaning several times, or may require wet/dry cleaning methods.

If inspection is vital what should we be looking for?

In an effort to establish some consistency in fibre optic connector inspections and to achieve more repeatable results the IEC

(International Electrotechnical Commission)  developed the 61300-3-35 Basic Test and Measurement Procedure Standard.

It specifies specific cleanliness grading criteria enabling you to assess either pass or fail for the connector end face.

IEC 61300-3-35 Basic Test and Measurement standard.

IEC standards categories' these into two groups; Scratches and Defects.

  1. Scratches are identified as permanent linear surface features,
  2. Defects include pits, chips, scratches, cracks, particles, embedded and loose debris.

Certification is based on the number of scratches or defects. Furthermore, they have established measurement regions being;

the Core, cladding, adhesive layer, and contact zones.

The certification criteria vary, based on

  • connector type,
  • fibre size 
  • types of defects.

Inspection of the end face can be achieved by one of two methods;

- using an objective method

- using automated certification

Using an Objective Method.

Yamasaki M200 Handheld Microscope

Typically this will be in the form of a handheld microscope. This is often the more cost-effective way of being able to check the end face of a connector.

The IEC61300-3-35 standard can be used as a guideline for manually grading cleanliness. This requires technicians to determine the size and locations of scratches and defects. It is just that little bit harder to get accurate and consistent results. Another disadvantage of using this method is that your eyes may be directly exposed to a working laser light, which is not great. You are therefore well-advised to make sure the microscope you are using in this case has a safety filter. 

Note; that the safety filter in the Yamasaki M200 and M400 is called "Optima GRB3" and is a high transmission heat absorbing filter.


Using Automated Certification Method

Yamasaki V5000 WiFi

Automated certification solutions use algorithmic processes to automatically and quickly inspect, grade, and certify end faces based on the criteria of the IEC standard.

Therefore eliminating any potential for human error. Typically they also come with Pass/Fail Analysis software, taking any guesswork away from you.

Another benefit is that they can be used on either a PC or mobile device for a visual, without exposing the eyes to any harm whatsoever.

Whilst also providing the option to print a certifiable record of the connector prior to installation if working from a PC with a printer connected.

Yamasaki V5000 WiFi


By simply following simple cleaning instructions and adhering to the inspection guidelines set out in IEC61300-3-35, you will significantly reduce the instance of network disruptions and save time and effort in the long run. Without a visual inspection of some kind, you will not have any idea of what the connector end face looks like or if there is any damage to the connector.

So cleaning and inspecting before using any connector is a must!