I saw that computer Network Interface Cards (NICs) that use fiber ports (SFP) instead of RJ-45 ports and I wonder if there would be any significant advantage in connecting the computers directly through optic fibers instead of RJ-45 (UTP)
There's several advantages to Fiber-to-the-desk
length: copper cabling is limited to 90 meters of horizontal cabling (leaving 10 meters for patching). Fiber doesn't have this limitation. In some building this can make a difference
cabled once for all: upgrading from 1Gbs to 10/50/100Gbs or a future Tbs doesn't require to recable the building, the fiber will do the job. Considering the cost of cabling, this can be a huge advantage.
security: it's more difficult to spy (tape) on a fiber cable than on copper. By listening to the radio frequency, one can remotely listen the traffic that goes over a copper cable. I did a fiber-to-the-desk project in a diplomatic office and this was the reason to go fiber.
fiber is immune to radio interference.
The main reason for fiber is reach: a fiber port with the appropriate optics can connect over many dozen kilometers - transceivers for 70 km or more are not uncommon. Currently, fiber Ethernet exists for up to 100 Gbit/s, with 200 and 400 Gbit/s being developed.
Other reasons may be: electromagnetic immunity, thinner cable, slightly lower latency, harder to tap
Copper is limited in reach (usually max. 100 m) and speed; the fastest copper Ethernet PHY, 40GBASE-T runs over just 30 m with special Cat.8 cable).
There are some main advantages of using fiber optic cables instead of copper: Fiber optic transmission is faster; Fiber optic transmission results in less attenuation; Fiber optic cables are impervious to electromagnetic interference (EMI); Fiber optic cables do not break as easily. http://www.thefoa.org/tech/fo-or-cu.htm I hope this link may be helpful to you~