GEO50-H Geophysical Graded-Index Optical Fiber - Hydrogen Resistant, PYROCOAT®*

Product Description

This optical fiber is designed for distributed temperature sensing and communications in applications where hydrogen diffusion is a concern, and in temperatures up to 250 ºC for long durations (~ up to 20 years, performance and reliability will vary depending on installation environment. Consult OFS for guidance). The waveguide features a proprietary, hydrogen insensitive core structure to minimize the effects of hydrogen darkening and also features a thin, hard, polyimide coating for excellent chemical resistance and thermal stability at elevated temperatures.

* NOTE: Hydrogen diffusion performance curve in datasheet
Unit of Measure



N/A Multimode Graded-Index

Short-Term Bend Radius

N/A ≥ 8 mm

Long-Term Bend Radius

N/A ≥ 10 mm

Features and Benefits

Improved Waveguide Resists Hydrogen DarkeningMinimizes permanent losses due to hydrogen ingression in harsh conditions
Graded-Index 50/125 Fiber StructureCompatible with most commercially available Distributed Temperature Sensing (DTS) interrogators; can also be fusion spliced to similar hydrogen insensitive core optical fiber, and traditional lead-in optical fibers
Carbon/Silicone/PFA Coating SystemLow friction, outer coating resists chemicals, abrasion and water absorption and is easy to mechanically strip


N/A OFL @ 850 nm: ≥ 400 Mhz-km
OFL @ 1300 nm: ≥ 400 Mhz-km

Optical Properties

Operating Wavelength

N/A 850/1300 nm


N/A @ 850 nm: ≤ 4.0
@1300 nm: ≤ 2.0 dB/km

Numerical Aperture (Nominal)

N/A 0.20

Dimensions/Geometric Properties

Core Diameter (Nominal)

N/A 50 ± 3 µm

Clad Diameter

N/A 125 ± 2 µm

Coating/Buffer Diameter

N/A 155 ± 5 µm

Clad Non-Circularity

N/A ≤ 2.0%

Core Non-Circularity

N/A ≤ 5.0% %

Coating/Buffer Descriptions

Coating Material


Operating Temperature

N/A -198 to +250 ºC

Mechanical and Testing Data

Proof Test Level

N/A 200 kpsi1.38 GPa