How to evaluate a fibre cable supplier

What you are really buying from a fibre supplier

A fibre assembly looks like a commodity until it fails in a live rack or on an outside broadcast. The glass, the ferrule and the polish are tiny, and the faults that matter are invisible without a microscope or a test set. That changes how a supplier should be judged. The price of a cord says little. The things that decide whether you can use the product are how well the supplier reads your drawing, what they test, what they record, and how they behave when something goes wrong.

This guide gives a method for comparing two or more suppliers of fibre cable and assemblies on evidence. It applies to a buyer in an enterprise, a data centre, a broadcast company, an integrator or an equipment maker. It starts from a clear written specification, because a supplier cannot be judged against a vague one. If you have not written yours yet, start with the guide to writing an RFQ for fibre assemblies and return here.

The method has five parts: separate the product from the maker, test the paperwork, test the samples, score the offers on weighted criteria, and plan the first order so that it checks the supplier before you rely on them.

Three kinds of fibre supplier

Suppliers sit in three groups, and the questions you ask change with the group.

None of the three is automatically better. A trader can be the right choice for a catalogue part you need tomorrow. An assembly maker is the better route for a made-to-drawing job with your polarity, lengths and marking, because they can change the build itself. Our custom fibre optic assemblies page describes that route. Radix makes fibre optic assemblies to the buyer's drawing in Pune, so the questions below are written for an assembly maker, but they work on any supplier.

Questions that separate a supplier who can answer from one who cannot

Ask these in writing and compare the answers side by side. A good answer is specific. A weak answer is a slogan or a deflection. Do not accept "we follow international standards" without a standard number.

Specification and drawing control

• Do you work from my drawing, or do you map it to your catalogue code? Who confirms the mapping in writing?
• How do you record the revision of a drawing, and how do you stop an old revision being built?
• Which details do you ask me to confirm before building: gender, polarity, key orientation, polish, boot colour, marking?

Testing and records

• Which tests are run on every assembly, and which on a sample?
• Is insertion loss measured on each assembly, at which wavelengths, and with what launch condition for multimode?
• Is return loss measured for angled-polish single-mode assemblies?
• Is the end face inspected, and to which acceptance criteria? The industry reference is IEC 61300-3-35.
• What does the test record look like, and can I see a blank or a sample?

Traceability and change

• Can a failed assembly be traced to a batch, and what does the batch record include?
• Will you tell me before changing the cable, connector or process?

Commercial terms

• How is a quote built, what does it include, and for how long is it valid?
• What happens with a wrong build: who pays for the return and the rework?

The supplier's own words are not proof. The point of the questions is to see whether the process exists. A supplier who can describe a test method precisely, show a sample record and name the standard has a process. One who cannot probably does not. Radix, for example, tests each cord before dispatch, and the test record format, wavelengths and limits are details to ask for in the quote, not assumptions to make.

Reading a test record

A test record is the strongest piece of evidence a supplier can show, if you know what to look for. A column of "pass" marks tells you little. A record with numbers tells you much more.

The two losses are explained in the guide to insertion loss vs return loss, and the way a typical cord is tested is covered in how fibre patch cords are tested. For the limits you compare against, note the common reference values. Cabling standards such as TIA-568.3-D and ISO/IEC 11801 allow up to 0.75 dB for a mated connector pair in a channel, and a supplier can often deliver lower. A supplier's low-loss grade should be named, with its limit stated, not described as "low loss".

Samples: how to test them yourself

Ask for samples of the exact build, not the nearest catalogue item. Then check them in three ways before you trust the supplier with volume.

1. Drawing check. Lay the sample beside your drawing and check every line: fibre type, connector, polish, length, polarity, marking and colour. Count fibres on a multi-fibre cord. Measure the length from connector tip to connector tip if that is how you specified it.
2. End face check. Inspect each connector with a fibre scope before cleaning, and again after cleaning. Dirt that cleans off is a handling matter. Scratches, pits and cracks that stay are a polish or termination fault. See the guide to connector end-face cleaning and inspection.
3. Loss check. Measure insertion loss with a light source and power meter, with a reference you set yourself. Compare your result with the supplier's record. A mismatch of a few hundredths of a dB is normal because of reference and cleaning differences. A mismatch of several tenths of a dB deserves a question.

Keep the sample and its record on file. A reference sample from the approved run is useful later, when a repeat order arrives that looks slightly different and you need to know whether it is correct.

If you cannot test loss yourself, a third-party check or an independent test at your own site is worth the cost for the first order of a new supplier.

Worked example: a weighted scorecard

Suppose a broadcast integrator needs 200 LC duplex OM4 cords in four lengths and compares three suppliers. The numbers below are assumed, to show the method.

Step one: decide the weights before you open the quotes, so that price does not set the criteria. Step two: score each supplier from 1 to 5 on each criterion, using evidence such as a sample test, a record or a written answer. Step three: multiply and add.

The weighted score is the sum of weight times score, divided by 5 to give a percentage of the maximum.

• X: 20x5 + 25x4 + 25x4 + 10x3 + 10x5 + 10x3 = 100 + 100 + 100 + 30 + 50 + 30 = 410, or 82 per cent.
• Y: 60 + 125 + 100 + 40 + 30 + 20 = 375, or 75 per cent.
• Z: 80 + 50 + 75 + 20 + 40 + 50 = 315, or 63 per cent.

Supplier Z is cheapest and scores last. That is the usual lesson of a scorecard: it makes the trade visible. Run a sensitivity check by doubling the price weight to 20, which makes the maximum 550. X becomes 440, or 80 per cent, Y becomes 395, or 72 per cent, and Z becomes 365, or 66 per cent, so the order of the three does not change. If it had changed, price would be deciding the outcome and you should say so openly.

Red flags in a quotation

• The quote does not repeat your specification. It names a catalogue code only.
• Test is described as "100 per cent tested" with no method, wavelength or limit.
• No answer to the question "which standard?" other than a general reference to international standards.
• Tolerances are not stated for length, or length is measured differently from your drawing without saying so.
• Large price gap to the others with no difference in specification. Ask what has been left out: connector grade, cable type, test, packaging.
• A refusal to share a blank test record or a sample record.
• Pressure to place the order before questions are answered.
• Certificates cited by name with no certificate number or issuing body. Ask to see the document before relying on a claim.

None of these proves a supplier is poor, but each is a reason to ask a follow-up question. A good supplier answers follow-ups without friction.

When a supplier comparison is the wrong exercise

Not every fibre purchase needs a scorecard. For a one-off cord to replace a broken one, the speed of delivery and the right connector are the whole decision. A formal comparison also stops being useful when only one supplier can build the item, such as a special rugged connector, or when a customer has named an approved supplier. In those cases spend the effort on the first-order checks below, not on scoring.

The reverse matters too. A purchase that goes into hundreds of racks, a broadcast truck, or an outdoor installation is expensive to fix after the fact. A day of comparison before the order is cheap beside a re-pull.

A warning about price. A price comparison is only valid if the quotes cover the same specification. Compare the fibre type, connector grade, polish, jacket, test, labelling and packaging line by line before comparing totals. Our notes on fibre optic cable price show which line items move a quote.

Plan the first order to check the supplier

A first order is itself a test. Plan it that way.

1. Order a small first lot with the real drawing, not a trial part.
2. Have the supplier confirm the drawing back to you in writing before they build.
3. Inspect the first lot against the checklist above, on receipt, before it goes into any equipment.
4. Compare the delivered record with your own loss and end-face checks.
5. Approve the lot in writing, and keep a reference sample.
6. Place the repeat order against that approved lot.

Record how the supplier handled the clarifying questions, the delivery and any fault. These are the same things you would score again at the next review. If you want to see how Radix handles this, send a drawing through the request a quote page, by phone or on WhatsApp, and we reply with what we can build and what we need confirmed. For export orders, the guide to buying fibre assemblies from India for export covers the paperwork and the checks specific to cross-border supply. The overview of fibre optic cable manufacturers in India also describes the market.