What you need to know about Fiber Optic Attenuators. Read here: https://nexus-net.info/a-beginners-guide-to-fiber-optic-attenuators/

1. Fiber cladding
Light
Fiber
Light absorption
Fully filled core
Fiber cladding
Gap
Fiber cladding
Light
Fiber
Light reflection
Fixed Optical Attenuator Optical Variable Attenuator
Designed to generate an unchanging
level of signal attenuation.
Has the stability, wavelength insensitivity,
and mode insensitivity that’s helpful during
signal testing and measurement.
Absorptive Principle
The optical fiber’s capability to reduce
optical power by converting
the energy it absorbs into heat.
Gap-Loss Principle
The attenuator is placed in the fiber path
together with an in-line configuration
to lessen the optical signal produced.
Reflective Principle
Attenuators reduce the optical signal
by scattering and reflecting
the light that passes through it.
Different Types of Fiber Optic Attenuators
Optical Attenuator Working Principles
That You Need to Know