FAQ RTS Product

What materials do I need to fabricate a fiber sensor?

To fabricate a single fiber sensor, one will need:

  • Desired Length of FBG Fiber
  • 1 x Fusion Splicer
  • 1 x Fiber Optic Cleaver
  • 1 x Razor Blade/Scissors
  • 1 x Fiber Sleeve Strippers
  • 1 x Fiber Coating Strippers
  • 1 x FC/APC Splice-Ready Pigtail
  • Proper Disposal Unit (Trash can, or preferably a fiber optic disposal can)
  • At least 9 feet of Blank Lead Fiber (SMF-28e) – Exposed OR Sleeved (Application dependent)
  • Alcohol
  • Lint Free Wipes
  • Tweezers
  • 1 x Splice Protection Sleeve
  • (Optional) 1 x Lighter – A lighter can be used instead of a fiber coating stripper for the sensing FBG fiber. In general the coating on FBG fiber is stiffer and more difficult to remove than the coating on standard communication fiber (lead fiber). While they can be removed with careful use of the strippers, some prefer to burn and clean it off.
  • (Optional + Recommended) 1 x Heatshrink tubing - When using lead fiber which is sleeved, it has to be cut back a a few inches before the splice point. After splicing, this leaves a short length of lead fiber exposed between the stripped sleeve and the splice protection sleeve. For protection, it is recommended to re-sleeve this exposed portion of the lead cable with a heatshrink.

What are some of the primary sources of noise in the fiber?

  • Bad Splice: Even the slightest bit of dust on the fiber ends can cause a splice to induce a few dB of signal loss. Check the approximate loss provided by the splicer with each splice. A good rule of thumb is to re-splice anything over .07 dB.
  • End Reflection: This is the source of noise in most cases. The end of the sensor fiber can cause a significant reflection back towards the RTS150. This reflection can significantly increase the noise of all the sensors, and even completely cover up the last 5 or 6 gratings. Leave the system running showing you the strain, and crush the very end of the fiber a few times until noise is at an acceptable level. Because the rough surface creation at the end of the fiber is random, it usually takes a few tries to get rid of major reflections. Newer versions of the RTS150 client software comes with a termination calibration tool which can be used to quantify the quality of the termination. See the user manual for more details on crushing and using the calibration software. If the noise level does not change at all with each crush, there is another issue.
  • Dirty Connectors: Even the slightest amount of grease or dust on the FC/APC connectors may significantly alter the signal. Ferrules can be cleaned with 10 or so circular swipes over a lint-free wipe, or even better, a ferrule cleaner. Optical suppliers offer spooled ferrule cleaners for swiping FC/APC connectors, as well as bulkhead cleaners, for cleaning the RTS150 front panel connections, and the broadband reflector connections. It is recommended to clean all connections after EACH disconnect.
  • Bend: Any bends in the sensing or lead fiber with a radius less than about a half of an inch will induce noise. This is caused by light leaving the fiber at higher bending radii. Extra heatshrink tubing can be placed over certain areas if needed to increase bending stiffness.
  • Lead Length: There must be at least 9 feet of lead between the output of the broadband reflector and the splice to your sensing fiber. If there is less than 9 feet, some or all of your gratings will not appear in the RTS150 output, and instead one will see very large amplitude noise.

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