Is fiber optic internet

In my opinion, yes. My sound quality was improved when I used an optical cable as described below 

My Ethernet source drives a netLINK Ethernet Media Converter model HTB-GS-03 with a fiber optic output driving a fiber optic cable to my Infigo Audio IS-1 streamer.  A 5V wall adapter powers the netLINK.  The streamer’s only digital output is USB to the DAC.  Infigo chose USB as the sole output format because done right it provides ultimate performance.  Any other format would increase cost while limiting bit rate, sample rate and ultimate performance.

Fiber optic isolation in this case improves audio quality by eliminating network noise and jitter. This separation between the ‘dirty’ network and the clean audio chain ensures that RF and EMI interference, as well as high-impedance leakage currents from network devices, do not degrade the audio signal. As a result, digital music reproduction is cleaner, quieter, and more transparent, providing a more natural and lifelike sound experience. 

Thanks for the response.  With that in mind, do you think if the internet source was from a fiber source, that alone would affect sound?

@rivinyl 

I believe a fiber internet source alone does not inherently affect sound quality in audio streaming, as digital data transmission ensures bits arrive intact regardless of the medium.  We need others to respond.  

FYI - Fiber optics can reduce electrical noise, RFI, and EMI compared to copper connections by using light signals immune to electromagnetic interference. In high-end audio setups, this may lower the noise floor, improve timing precision, and yield a cleaner soundstage when using fiber media converters between network components.