Instrument List
The instruments used for installing fiber Bragg grating (FBG) sensors mainly include:
- Fusion splicer and matching stripping tools
- Portable FBG interrogator
- OTDR
- Stable light source
- Optical power meter
- Visual fault locator (red-light pen)
Fusion Splicer and Matching Stripping Tools
Fusion Splicer
The splicing requirements of bridge and tunnel structural health monitoring projects are basically comparable to access-network (installation & maintenance) work in telecom engineering: only a few splices at a time (far fewer than long-haul trunk cable splicing), with modest battery demands — one battery generally covers a full day of work. Therefore, a model designed for access-network or installation/maintenance applications is sufficient.
Brand choice: based on more than ten years of field statistics, we endorse the two Japanese imports — Fujikura and Sumitomo. This is not blind preference for foreign products; we have simply been burned by domestic units before, and the experience left its mark.
Matching Stripping Tools
- Fiber cleaver: choose a cleaver from Fujikura or Sumitomo — it is the key to splice quality and efficiency
- Miller stripper: domestic stainless-steel versions, though a bit pricier (actually only around 80–90 RMB), are reliable and durable. When we built a submarine tunnel monitoring system, the high-humidity, high-salinity environment inside the tunnel caused ordinary Miller strippers to rust completely within days of a single use
- Other pliers and knives: these are consumables — stock several spares, and simply discard and replace them when they rust or break; they cost little
Portable FBG Interrogator
This is the most expensive instrument on the list — not because it is remarkably sophisticated or technically advanced, but because demand is so small that unit costs stay high. In the past we mainly rented equipment from sensor manufacturers. If anyone finds a general-purpose model at a reasonable price, we would welcome the exchange.
OTDR
OTDRs are mainly used during the operation and maintenance phase. Tunnels and bridges are often several kilometers — even a dozen or more — long. When troubleshooting a fault (such as a sensor going offline or abnormal data), you can test the affected channel from the acquisition station end to help locate the fault point.
Stable Light Source and Optical Power Meter
These two instruments are typically used together. When splicing sensors into a chained array, they allow real-time control of the channel's transmission quality. Pay attention to connector types during testing, and keep a complete set of adapter patch cords and other passive optical components on hand.
Visual Fault Locator (Red-Light Pen)
Mainly used for fault troubleshooting: within a single channel it helps test continuity and locate fault points. We recommend keeping two units — one with 5 km range and one with 30 km range — for near-end and trunk fiber testing respectively.
Instrument Care
Instruments must be protected and properly maintained: charge them promptly, address problems as soon as they appear, and ensure that when the project needs them, every instrument is in healthy working condition.