By TEBAOFLEX Jyen. Originally published on April 8, 2026.
The measured fiber strain is not automatically the host strain
Distributed sensing requires matching the interrogator, fiber, cable and installation. A strain-sensing cable must transfer deformation from the structure; a temperature-reference element may intentionally reduce mechanical coupling. Solifos lists separate BRUsens DTS, DSS and DAS families, illustrating why these duties should not be treated as interchangeable.
Brillouin measurements can depend on both strain and temperature. Compensation can use a separate reference or another validated measurement method; two separate cables are not mandatory for every interrogator. Calibration coefficients belong to the actual fiber and assembly.
Illustrative cross-sensitivity
A linear model is Δν=CεΔε+CTΔT. With explicitly assumed coefficients Cε= 0.048 MHz/με and CT= 1.08 MHz/K, a 1 K change would imitate 22.5με if temperature were ignored. These are example coefficients, not an IEC acceptance criterion or a measured TEBAOFLEX calibration.
Coating expansion, installation restraint and spatial resolution affect the effective response. Temperature compensation must include the uncertainty and thermal tracking of the reference, rather than promising exact strain from nominal coefficients.
Shear-lag model and boundary conditions
For a simplified, uniformly strained bonded segment of total length 2L with free fiber ends, an illustrative average transfer expression is η= 1−tanh(βL)/(βL). It assumes an elastic, idealized bonding model; it is not a universal formula for a grouted field cable.
At βL= 1.3 the expression gives approximately 0.337. At βL= 9.25 it gives approximately 0.892. A claim of 0.985 needs different, demonstrated boundary conditions or measurements; it cannot be read from those same assumptions. Bond slip, creep and a localized crack can invalidate the uniform-strain approximation.
Thermal response is a system property
For an ideal first-order step response, the time constant τ corresponds to 63.2% of the final change and t90 ≈ 2.303τ. Illustratively, τ= 3 s gives t90 ≈ 6.91 s. A plunge-bath response must not be represented as the response to a small hot bearing in air.
Jacket thickness, air gaps, thermal capacity, contact, flow and interrogator averaging matter alongside material conductivity. A metal tube does not by itself guarantee a sub-3.5-second response or fire-detector approval.
Specify a calibration and installation plan
Record gauge length, spatial resolution, scan time, strain/temperature range, mounting or grouting method and allowable drift. Validate the installed response against independent references over representative cycles.
Request traceable optical, mechanical and calibration evidence, including residual strain sensitivity of temperature channels and repeatability of the host-to-cable bond.
Primary references and specification evidence
The references explain the cited technology or manufacturer example. They are not TEBAOFLEX product approvals or evidence that a supplied batch has passed the tests. Request the exact product drawing, specification edition, acceptance criteria and traceable records.
Discuss your application
Discuss the duty, installation and required documentary evidence with TEBAOFLEX. WhatsApp: +86 185 9591 3361. Product suitability and test obligations must be confirmed for the specific order.