How to choose a fibre sensing solution

Choose a fibre sensing solution by defining the event or condition you need to observe, the information your team needs and the action that should follow. Then assess the sensing method, installation, integration and evidence against that requirement. A product specification alone cannot establish suitability for your site.

Start with the operating decision

For a utility perimeter, an illustrative requirement might be: recognise unauthorised activity, locate it accurately enough for assessment, and get useful information to the person responsible for responding. The team must then define the required accuracy, response time and conditions. Those figures should come from the operating need and a representative evaluation.

Ask three questions before making a shortlist. What needs to be detected or measured? What will distinguish that event from normal activity? Who will assess the information and take action?

Match the sensing method to the question

Distributed acoustic sensing (DAS) is relevant to dynamic disturbance and vibration questions. Distributed temperature sensing (DTS) is relevant to temperature along a route. Distributed strain sensing addresses deformation-related questions. These labels do not describe every instrument's capability. Ask what the proposed system actually measures, how that measurement relates to the event of interest, and what limitations apply.

Start from the application. A perimeter intrusion problem, a temperature-monitoring requirement and a structural movement question may need different systems, different cables and different installation methods. Some projects need a combination of sensing and verification technologies.

Verify the installation assumptions

Existing fibre is a possible starting point, not proof that a proposed system will work. Establish the route, ownership, access rights, fibre condition, optical losses and relevant installation details. Ask the supplier how the cable's placement and connection to its surroundings affect the intended measurement. Record where those assumptions remain untested.

Include power, equipment environment, communications, maintenance access and integration with the receiving systems. Name the party responsible for each interface.

Compare suppliers against the same brief

Give each shortlisted supplier the same information and request a response covering the requirement addressed, evidence offered, unresolved assumptions, installation scope, integration responsibilities, support and proposed acceptance process. Identify which claims are supplier-published and which have been independently demonstrated under relevant conditions.

An attractive range or sensitivity figure is useful only when the conditions behind it are understood. Ask what changes at the actual site and what evidence will establish suitability there.

Agree what the trial will decide

Before equipment arrives, agree who will decide whether to proceed and what evidence they need. Include representative target events, ordinary background activity, operator assessment and the response process. Record limitations and define what would lead to a revised design or a decision to stop.

What should you send to an adviser? A short description of the asset and operating problem, known fibre and site constraints, the current project stage, the decision owner and the decision deadline. Avoid sharing confidential documents until the appropriate arrangements are agreed.

A brief your suppliers can answer

Use the following headings to turn an initial enquiry into a common requirement. An unanswered question belongs in the brief as an unknown, with an owner for resolving it.

Example: a utility perimeter

Consider a hypothetical utility site with an existing fibre route and cameras. Asking for a system that covers the perimeter leaves key questions unanswered. Does the fibre follow the boundary closely enough for the intended application? What activity should generate an alert? How will an operator find the relevant camera view? What happens in an area without useful camera coverage?

The brief should identify those questions before suppliers propose equipment. If the fibre route or camera mapping is uncertain, the next step may be a survey or an integration assessment. A longer equipment range does not resolve an unverified installation assumption.

Buyer questions

Can I use existing telecoms fibre?

Possibly. Establish access, route, fibre condition and installation suitability with the proposed supplier. Do not assume that an available fibre pair is suitable for sensing, or that it can share an active communications service without an agreed technical design.

Is DAS the right choice for every fibre sensing project?

No. Begin with the quantity to be measured and the operating decision. A temperature requirement, vibration question and slow deformation problem call for different evaluation criteria. Ask suppliers to explain both capability and limitations for the actual application.

Should I choose a supplier before writing the brief?

Supplier discussions can help identify what is practical. Keep the customer's requirement explicit, record which advice comes from each supplier and use the same brief when comparing proposals. A product feature should become a requirement only when it serves a justified project need.

Where can Sentari help?

Sentari can help structure the requirement, identify evidence gaps and prepare the questions that make a supplier discussion productive. Site-specific design, performance commitments and acceptance remain matters to agree with the responsible project parties.

Make the next supplier conversation useful

Send Robin a short, non-confidential outline of the asset, the operating problem, your project stage and the decision deadline. That is enough to start discussing an appropriate advisory scope.

Discuss your sensing requirement.

Sources and scope

Further reading: FOSA technology primers, for the underlying sensing methods; Practical Considerations for Field Deployable DAS Systems, David Hill, 2024, for field constraints. The latter concerns geophysical deployment and is not validation of a security installation. This guide is an editorial decision framework, not a site design or engineering approval.

Related guides: DAS installed cost and trial acceptance.

Use the Before you specify fibre sensing worksheet to prepare your project outline.