Optical power degradation at shorter wavelength

Technical Discussions
1

Hi,

Does anyone know of the reasons behind optical power/ mode quality degradation at short wavelengths (400-600nm)?
I see power drop over time. My fibre is PM-S405-XP with angle cleaving and AR coating.

2

Dear Saurabh

I think the largerst contributer to the attenuation you observe can be due to the scattering loss. Since scattering is intersely proportinoal to the wavelength you can expect larger scattering loss at shorter wavelengths. To mitigate scatering losses at short wavelengths you can make sure to follow cleaning correct fiber storage, handling and cleaning procedures.

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3

Optical fibers with germanium dopes core (the usual step index stuff) can exhibit photodarkening effect over time. The shorter the wavelength and the higher the power, the worst. Interestingly there is an effect with high power cw IR lasers that over time the high power IR throughput triggers absorption increase in the visible region. Photodarkening is basically small changes in the material structure - in some cases reversible, but most often irreversible.

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