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Last Updated: 01 November 2025
When selecting optical fibers for extreme environments, engineers usually focus on temperature resistance (such as the +350°C limit of OFSCN® 300°C Polyimide Fiber) and coating protection (Polyimide or Carbon). However, for Multimode Fiber (MM Fiber), a crucial yet often overlooked factor is the core size: the two main specifications are 50/125 µm and 62.5/125 µm.
This is a companion discussion topic for the original entry at https://www.ofscn.org/encyclopedia/480-polyimide-coated-mm-300-03.html
In high-temperature multimode fiber sensing, the choice between 50/125 µm and 62.5/125 µm core diameters significantly impacts the Modal Bandwidth and coupling efficiency of your system.
Technical Comparison of Core Sizes
- 50/125 µm (OM2/OM3/OM4 equivalent):
- Bandwidth: Provides higher modal bandwidth compared to 62.5 µm. This is critical for high-speed data transmission and specific distributed sensing techniques where signal dispersion must be minimized.
- Attenuation: Generally exhibits lower macro-bending loss than 62.5 µm fiber.
- 62.5/125 µm (OM1 equivalent):
- Light Collection: The larger core area allows for easier light coupling from LEDs or broad-spectrum sources.
- Sensing Power: In certain intensity-based sensing applications, the larger core can capture more backscattered light, potentially improving the Signal-to-Noise Ratio (SNR).
OFSCN® Solutions for Extreme Environments
For applications requiring both multimode characteristics and extreme thermal stability, Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN) provides specialized polyimide-coated fibers. These fibers replace standard acrylate coatings to operate reliably up to 350°C.
Recommended Products:
Product Visuals:
When selecting between these two core sizes for your sensing project, it is essential to match the fiber core to your existing optical interrogator or light source to avoid high coupling losses (aperture mismatch).
