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A-56
IM 39J06B40-01EN 14th Edition: May 30, 2022
A6. Sensor Optical Fiber
A6.1. Choosing Sensor optical fiber
Sensor optical fibers to be used must satisfy the DTSXL System specifications.
Table Sensor Optical Fiber Specifications
Item Specification Requirements
Optical connector E2000/APC
Optical fiber material
50/125 µm GI quartz fiber or SM fiber
(Select the optical fiber by specification code)
Wavelength characteristics
Minimal loss and flat wavelength loss characteristics at the 1550 nm
band
Typical loss
GI: 0.25 dB/km (for the ST) or 0.25 dB/km (for the AS)
SM: 0.20 dB/km (for the ST) or 0.20 dB/km (for the AS)
Splicing method Fusion splicing
Connection loss 0.3 dB max., 0.15 dB max. on average
Reflection
No reflection (Anti-reflection termination required at the far end of the
optical fiber.)
A6.2. Precautions When Choosing Sensor optical
fiber
In addition to the specification requirements stated above, observe the following
precautions when selecting sensor optical fiber.
■
Precautions on Environment Resistance
●
Temperature
Selected optical fibers must cover the intended temperature distribution measurement
range.
Typical optical fibers are resistant up to 80
°
C. If higher temperatures are to be
measured, heat-resistant optical fibers (e.g., polyimide-coated optical fibers). In addition
to short-term deterioration, deterioration under prolonged exposure to high temperatures
must also be considered when selecting sensor optical fibers.
●
Humidity
Optical fibers deteriorate when in contact with water (or the OH radical). If sensor optical
fibers must be used in water or at high humidity, select water resistant and heat-resistant
optical fibers. Beware that optical fibers deteriorate even faster under high-temperature,
high-humidity conditions.
●
Corrosive gas
For installation in the presence of hydrogen sulfide or other corrosive gases, select a
metal-tubing cable (e.g., made of incoloy) resistant to the specific corrosive gases.
●
Length
Optical fiber splice points should be as few as possible, preferably none. The required
optical fiber length must be determined taking into account the optical fiber laying
method employed. The required length must include extra length for optical fiber
sagging and installation, and thus would be longer than the length calculated from the
drawing or map.