Factors that can lead to the failure to transmit light through an unbroken fiber optic coil

1. Bending Radius: If the fiber optic coil has been bent beyond its minimum bending radius, it can cause micro cracks or fractures in the fiber core or cladding. This can lead to light loss due to increased scattering or absorption of light within the fiber.

2. Mechanical Stress: Excessive mechanical stress, such as twisting or pulling on the fiber optic coil, can cause deformation or damage to the fiber, affecting its ability to transmit light effectively.

3. Contamination: Dust, dirt, or other contaminants on the surface of the fiber can obstruct or scatter light as it travels through the fiber, leading to reduced transmission efficiency.

4. Connector Issues: Poorly terminated connectors or connectors that are not properly aligned with the fiber can cause significant light loss at connection points, impacting overall transmission through the coil.

5. Fiber Quality: Low-quality fiber optic cables or fibers with defects introduced during manufacturing can have higher attenuation, resulting in reduced light transmission even through an apparently unbroken coil.

6. Environmental Factors: Changes in temperature or humidity can affect the optical properties of the fiber, potentially leading to increased attenuation and reduced light transmission.

7. Wavelength Issues: If the fiber is designed for a specific wavelength range (such as single-mode fibers optimized for certain wavelengths), using light outside this range may result in higher attenuation.

8. Age and Wear: Over time, fiber optics can degrade due to aging effects, which might not be visibly apparent but can still impact light transmission performance.

In summary, while a fiber optic coil may appear physically intact, several underlying factors such as bending beyond the minimum radius, mechanical stress, contamination, poor connectors, fiber quality, environmental conditions, and wavelength mismatches can collectively or individually contribute to the failure to transmit light effectively through the fiber optic coil.