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FOCS / STUDIOFIBER OPTIC CURRENT SENSOR • ENGINEERING LAB
LOCAL MODEL · 3D + SIGNAL PHYSICS
HIGH CURRENT BUSBAR INSTRUMENTATION · REFLECTIVE INTERFEROMETER

Measure the current. Never touch the conductor.

Explore a passive fiber sensing head around a high-current busbar, then follow the light through the interrogator, Faraday phase shift, digital demodulation, and measured DC/AC current. Includes a configurable engineering model, assembly plan, firmware concept, BOM, and commissioning checklist.

SIMULATOR · NOT A CERTIFIED DESIGN
Idealized physical relationships with explicit noise and fault models. No actual energized-system installation instructions.
01 / SPATIAL MODELDrag to rotate · scroll/pinch to zoom · click components
REFLECTIVE SENSOR HEAD

Fiber wraps the conductor in a closed path; Faraday phase is proportional to the enclosed current.

PHASE SHIFT 0.000 rad · CLOSED LOOP

Control the current & optics

Experiment with the ideal Faraday effect and see the receiver's measured response. Values are simulated—not a protection or metering grade design.

−500 kA0+500 kA
MODEL STATUS · LOCKEDInterrogator running; positive current gives positive Faraday phase.
A correctly closed fiber contour measures net enclosed current. Coil radius and conductor position do not change the ideal result; a neighboring conductor outside the loop contributes no net ideal signal. Real head defects and stress violate that assumption.

Construct the sensing system

Eight engineering stages, from a low-voltage bench demonstrator to a qualified optical instrument. Select a stage to highlight the relevant 3D component.

Do not fabricate or fit an unqualified sensor around energized busbars. Physical deployment requires insulation coordination, temperature rating, bend-radius verification, arc-flash risk assessment, EMC and applicable product qualification.

Build bill of materials

Engineering selections, not a vendor-quoted purchasing specification.
0 COMPONENT LINESSpecific photonic parts, receiver electronics, housing, reference equipment.
#ItemQtyPurpose / starting specification

Sources for component types: Fibercore current-sensing fiber guidance, ABB optical architectures, and published prototype literature. Specialist components require manufacturer optical-power, wavelength, polarization, bend, thermal, and qualification reviews.

Receiver firmware concept

Illustrative embedded C demodulation, with sensor faults and output scaling.
HOW THIS SIMULATOR OPERATESFour idealized phase-bias samples reconstruct phase with atan2(Y,X); continuity logic unwraps phase and divides by 4 μ₀ V N. Commercial units typically use high-rate modulation and synchronous demodulation with more extensive compensation.
Replace the abstract acquisition routine with synchronized FPGA/ADC hardware. No real sensor drivers, SIL/protection logic, timing qualification, or IEC 61850 network stack are supplied.


Verification & commissioning
A practical engineering review before any field deployment. Click to check off individually demonstrated tests. Checks don't make a design certified.
0 of 10 tests reviewed






150.0kA · primary reference
—kA · received
—rad · round-trip
—mT · ideal circular path
—µW · after losses
LOCKEDphase continuity good


02 / LIVE MEASUREMENT & DEMODULATIONtime domain + four-phase response
Busbar current vs. reconstructed optical current ━ true ━ measured
Phase-stepped interferometer receiver atan2(Y,X)


03 / WHAT THE INSTRUMENT MEASURESreference equations + live derived parameters
The conductor's magnetic field circulates around the busbar. In a properly closed sensing path, the integrated field depends on the net enclosed current, not the exact location of the busbar inside the loop.
B(r) = μ₀I / (2πr)Ideal infinitely long straight conductor; actual busbar geometry changes local field.
∮ B · dl = μ₀IAmpère's law in the ideal nonmagnetic, quasi-static geometry.
Δφ = 4 μ₀ V N IReflective interferometer round-trip differential phase (ideal model).
Verdet constant0.53 rad/(T·m)
Phase sensitivity— µrad/A
Ideal current for 2π phase— kA
Nominal receiver optical power— µW
Example ±500 kA 4–20 mA scale— mA
Neighbor conductor couplingIdeally zero (outside)
The model's sensing fiber is reflective and includes simplified gain, insertion loss, noise, head defects, and phase wrapping. It does not solve coupled electromagnetic and optical material equations numerically.


04 / PROJECT DEFINITION · COMPONENT FUNCTIONS & SAFETY CASEEngineering starting point
Sensor head → passive, close to the busbar
Spun sensing fiber, quarter-wave retarder, reflection termination, mechanically stable insulated housing. No local electrical power is needed at the optical sensing element.
Control cubicle → active electro-optics
1550/1310 nm source, polarization optics, phase modulation, delay fiber, photoreceiver, ADC, FPGA/MCU processing, isolated power, health monitoring, and telemetry.
Smelter / rectifier monitoring
Use DC-capable current measurement across a large enclosed conductor range; design for high ripple, busbar heating, electromagnetic fields, fast transients, and continuous operations.
Protective use → independent qualification
Never use this demonstrator as an overcurrent trip or interlock source. Required verification includes redundancy, diagnostics, loss-of-light response, synchronization, insulation, EMC, latency, and applicable standards.
Technical references & manufacturer guidance
2026 FOCS field research · reflected phase equation · FOCS optical architecture and demodulation research · Fibercore sensing fibers and optics · ABB FOCS (discontinued product notice) · IEC 61869-9 digital instrument-transformer interface · Silica-fiber Verdet constant measurement.






  
FOCS Studio — Fiber-Optic Current Sensor Lab

  
Explore a fiber-optic current sensor model: tune busbar and optics, view simulated signals, export a sample BOM and CSV, and copy firmware pseudocode.


  
What this models

  
FOCS Studio is an interactive engineering model of a fiber-optic current sensor around a high-current busbar. It illustrates the Faraday-effect signal path from the sensing loop through an optical receiver and phase-demodulation model.


  
When to use it

  
Use it to explore how selected current, geometry, optics, and fault conditions affect the modelled phase and receiver output, or to review a conceptual parts list and verification checklist.


  
Who this is for

  
Students, engineers, and technical reviewers learning about optical current sensing and instrumentation. It is a teaching and exploration model, not a certified design or commissioning procedure.


  
How to use it

  
    
    
  1. Adjust the primary current and source, fiber turns, wavelength, loop radius, optical loss, head temperature, conductor offset, and electronic noise.
    2. 
    
  2. Change loop and adjacent-conductor conditions to explore the displayed fault and interference cases.
    3. 
    
  3. Rotate or explode the 3D assembly, then inspect the simulated field, light path, phase, receiver, and measured-current views.
    4. 
    
  4. Open the BOM, firmware-concept, and verification tabs. Capture a sample, export the BOM or CSV, copy the illustrative receiver code, or reset the checklist.
    5. 
  


  
Inputs and outputs

  
Inputs include current, optical and geometric parameters, temperature, alignment, noise, and sensor status. Outputs include modelled busbar current, Faraday phase, local field, optical response, receiver status, and captured sample values.


  
Exports and saving

  
The page can export a sample bill of materials and captured signal CSV, and copy an illustrative embedded-C receiver concept. These are generated examples, not vendor quotations or production firmware. Settings and checklist changes are not saved across reloads.


  
Important limitations

  
The model uses idealized physical relationships with explicit noise and fault cases. It is not protection-grade, certified, or validated for real equipment, and it does not provide instructions for installing a sensor on an energized system. Do not use its values to design or approve a protective trip.


  
Network and data

  
The sensor model runs in the browser. This page also uses the site's standard Google Analytics page-view tag when online; model settings are not submitted to an application backend.


  
Frequently asked questions

  
Can I use the BOM to build a protection system?
No. It is a conceptual sample, not a quoted purchasing specification, certified design, or protection-system approval.

  
Does the model save my inputs?
No. The model runs in the current page and does not save settings across reloads. Standard page-view analytics may run when connected.


  
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